ORTHOPEDIC MCQS BANK WITH ANSWER HIP 01

 

1.          Figure 1 shows the radiograph of a 68-year-old man who underwent revision hip arthroplasty with impaction grafting of the femur and cementing of a tapered component into the graft 2 years ago.  The patient remains symptom-free.  Which of the following best describes the most likely histologic appearance of the proximal femur if a biopsy was performed? 

 

1-         Complete restoration of the cortex, with interdigitation of cement into the patient’s native bone

2-         Fibrous membrane encapsulating the stem, surrounded by a cement mantle and dead allograft

3-         Healing by mixed endochondral ossification, similar to fracture healing, surrounding the cement mantle

4-         Allograft resorption, with some cortical restoration because of osteoinduction

5-         Viable trabecular bone resulting from incorporation and remodeling of allograft

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The radiograph shows three zones: an outer regenerated cortical layer, an interface zone consisting of viable trabecular bone and occasional particles of bone cement, and an inner layer of necrotic bone embedded in cement.  No fibrous membrane is noted, and there is no direct contact of cement with native bone.  Based on these findings, it is believed that the middle layer is the result of incorporation of the allograft with further remodeling.

 

REFERENCES: Nelissen RG, Bauer TW, Weidenhielm LR, LeGolvan DP, Mikhail WE:  Revision hip arthroplasty with the use of cement and impaction grafting: Histological analysis of four cases.  J Bone Joint Surg Am 1995;77:412-422.

Gie GA, Linder L, Ling RS, Simon JP, Slooff TJ, Timperley AJ: Impacted cancellous allografts and cement for revision total hip arthroplasty.  J Bone Joint Surg Br 1993;75:14-21.

2.         Compared with cobalt-chromium, the biomechanical properties of titanium on polyethylene articulation in total hip replacement result in

 

1-         an increased rate of volumetric wear.

2-         increased stability.

3-         decreased frictional force.

4-         a decreased rate of acetabular loosening.

5-         a decreased rate of femoral stem loosening.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The surface hardness of titanium is low compared with that of cobalt-chromium alloys.  Titanium articulations are easily scratched, resulting in a significantly increased rate of wear and debris production.  The wear and resulting lysis can also result in an increased rate of loosening.

 

REFERENCES: Simon SR (ed): Orthopaedic Basic Science.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486.

Agins HJ, Alcock NW, Bansal M, et al: Metallic wear in failed titanium-alloy total hip replacements: A histological and quantitative analysis.  J Bone Joint Surg Am 1988;70:347-356.

Robinson RP, Lovell TP, Green TM, Bailey GA: Early femoral component loosening in DF-80 total hip arthroplasty.  J Arthroplasty 1989;4:55-64.

3.         What is the most common reason for reoperation in total knee arthroplasty?

 

1-         Polyethylene insert failure

2-         Malalignment of the knee

3-         Ligamentous instability

4-         Perioperative infection

5-         Patellar-related complications

 

PREFERRED RESPONSE: 5

 

DISCUSSION: Patellar problems currently constitute the largest number of complications after total knee arthroplasty, affecting between 8% and 35% of patients.  These problems include patellar instability, fracture, component loosening, surface erosion, and pain.  Malalignment, as an isolated reason for revision, is uncommon, yet it contributes to accelerated wear of the components.  Joint instability affects up to 6% of patients, and the infection rate in knee arthroplasty is around 1% to 2%.

 

REFERENCES: Blasier RB, Matthews LS: Complications of prosthetic knee arthroplasty, in Epps CH (ed): Complications in Orthopaedic Surgery.  Philadelphia, PA, JP Lippincott, 1994, pp 1066-1069.  

Rand JA: The patellofemoral joint in total knee arthroplasty.  J Bone Joint Surg Am 1994;76:612-620.

Wilson MG, Kelley K, Thornhill TS : Infection as a complication of total knee-replacement arthroplasty: Risk factors and treatment in sixty-seven cases.  J Bone Joint Surg Am 1990;72:878-883.

4.         Which of the following factors is most commonly associated with mechanical failure of a cemented total hip arthroplasty?

 

1-         Increased stem offset

2-         Varus position of the stem

3-         Osteoporotic bone

4-         Patient weight of greater than 154 lb

5-         Gender

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Varus position of the stem is most commonly associated with failure of the cemented femoral component because of association with an inadequate cement mantle in the proximal medial and distal lateral zones.  An inadequate cement mantle and obesity have been associated with increased loosening but not as frequently as a varus deformity.  The influences of gender and osteoporotic bone on the outcome of cemented femoral components have not been established.

 

REFERENCES: Maloney WJ III: Primary cemented total hip arthroplasty, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 179-189. 

Callaghan JJ, Salvati EA, Pellicci PM, Wilson PD Jr, Ranawat CS: Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982: A two- to five-year follow-up.  J Bone Joint Surg Am 1985;67:1074-1085.

5.         Figure 2 shows the radiograph of a 72-year-old woman who reports pain after a fall. History includes several years of increasing thigh pain and limb shortening. Management consisting of an extensive work-up for infection reveals normal laboratory studies, a positive bone scan, and a negative hip aspiration.  What is the most likely etiology of this complication?

 

1-         Loosening of the prosthesis

2-         Modulus mismatch

3-         Chronic infection

4-         Osteoporosis

5-         Metastatic tumor

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The patient has a midstem periprosthetic fracture, which commonly results in loosening of the prosthesis.  Patients who have a large amount of bone loss may require an allograft with the surgical reconstruction.  Although the patient reported a fall, her history is also consistent with preexisting loosening of the prosthesis.  Chronic infection has been shown in up to 16% of these fractures; however, the patient’s work-up revealed no infection.  

 

REFERENCES: Garbuz DS, Masri BA, Duncan CP: Periprosthetic fractures of the femur: Principles of prevention and management, in Cannon WD Jr (ed): Instructional Course Lectures 47. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 237-242.

Bethea JS III, DeAndrade JR, Fleming LL, Lindenbaum SD, Welch RB: Proximal femoral fractures following total hip arthroplasty.  Clin Orthop 1982;170:95-106.

Kelley SS: Periprosthetic femoral fractures.  J Am Acad Orthop Surg 1994;2:164-172.

6.         Figures 3a through 3c show the radiographs and bone scan of a patient who reports increasing pain associated with activity for the past several months.  Laboratory studies show an erythrocyte sedimentation rate of 14 mm/h and a C-reactive protein level of 0.4.  Aspiration is negative for infection.  Management should consist of

 

1-         antibiotics for 6 weeks.

2-         use of an unlocked brace.

3-         revision arthroplasty.

4-         resection of the implants.

5-         two-stage reimplantation.

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The radiographs show polyethylene wear, but exchange of this will not necessarily provide pain relief.  The presence of pain suggests the possibility of occult loosening, and the surgeon must be prepared for this option intraoperatively.  There is little evidence of infection.

 

REFERENCES: Rand JA, Peterson LF, Bryan RS, Ilstrup DM: Revision total knee arthroplasty, in Anderson LD (ed): Instructional Course Lectures XXXV.  Park Ridge, IL, American Academy of Orthopaedic Surgeons, 1986, pp 305-318.

Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 317-322.

7.         Which of the following studies has the highest sensitivity and specificity in diagnosis of osteonecrosis of the femoral head?

 

1-         Intraosseous pressures

2-         AP and frog-lateral radiographs

3-         Technetium Tc 99m bone scan

4-         MRI scan

5-         CT scan

 

PREFERRED RESPONSE: 4

 

DISCUSSION: An MRI scan is both highly sensitive and specific for the evaluation of osteonecrosis.  The measurement of increased intraosseous pressure can be technically difficult and the results have been variable.  Plain radiographs can be normal early in the progression of osteonecrosis of the femoral head.  The technetium Tc 99m bone scan is a very sensitive test.  However, it is not specific; increased uptake can be noted in patients with arthritis, neoplastic disease, fracture, or sepsis.  In addition, because of bilaterality, the frequency of false-negative scans is relatively high.   

 

REFERENCES: Steinberg ME: Early diagnosis, evaluation, and staging of osteonecrosis, in Jackson DW (ed): Instructional Course Lectures 43.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 513-518.

Glickstein MF, Burk DL Jr, Schiebler ML, et al: Avascular necrosis versus other diseases of the hip: Sensitivity of MR imaging.  Radiology 1988;169:213-215.

8.         Figure 4 shows the AP radiograph of a 28-year-old woman who has had moderate pain in the left hip for the past year.  Nonsurgical management has failed to provide relief.  She denies any history of hip pain, pathology, or trauma.  Management should consist of

 

1-         observation.

2-         a Pemberton osteotomy.

3-         a periacetabular osteotomy.

4-         a Chiari osteotomy.

5-         total hip arthroplasty. 

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The radiograph shows developmental dysplasia of the hip with the hip reduced and congruent.  The treatment of choice is a periacetabular osteotomy because it can improve hip biomechanics and prolong the function of the hip joint.  This procedure should be performed prior to the development of severe degenerative changes.  Observation will not alter the patient’s natural history or the biomechanics of the hip.  A total hip arthroplasty should be delayed until severe degenerative changes are present.  A Chiari osteotomy is a salvage osteotomy used for a noncongruent subluxated hip.  A Pemberton osteotomy requires an open triradiate cartilage; therefore, it is not an option in an adult. 

 

REFERENCES: Trousdale RT, Ekkernkamp A, Ganz R, Wallrichs SL: Periacetabular and intertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips.  J Bone Joint Surg Am 1995;77:73-85.

Pemberton PA: Pericapsular osteotomy of the ilium for the treatment of congenital subluxation and dislocation of the hip.  J Bone Joint Surg Am 1965;47:65-86.

9.         What complication is most likely to develop after right total hip arthroplasty in the patient shown in Figure 5?

 

1-         Infection

2-         Dislocation

3-         Heterotopic bone formation

4-         Early mechanical loosening

5-         Excessive bleeding

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The patient has hypertrophic arthritis, which is a strong risk factor for heterotopic bone formation.  The remaining complications are possible but do not have the same significant risks.

 

REFERENCES: Goel A, Sharp DJ: Heterotopic bone formation after hip replacement: The influence of the type of osteoarthritis.  J Bone Joint Surg Br 1991;73:255-257.

Nollen JG, van Douveren FQ: Ectopic ossification in hip arthroplasty: A retrospective study of predisposing factors in 637 cases.  Acta Orthop Scand 1993;64:185-187.

10.        In revision total hip arthroplasty, an acetabular reconstruction cage is best indicated for which of the following patterns of bone loss? 

 

1-         Enlarged acetabular rim

2-         Cavitary central defect

3-         Superior migration of 2 cm

4-         Deficient anterior wall

5-         Pelvic discontinuity

 

PREFERRED RESPONSE: 5

 

DISCUSSION: Acetabular cage reconstruction is indicated in severe disruption of acetabular bone stock when a cementless acetabular component cannot be stabilized in intimate contact with a sufficient bed of structurally sound and viable host bone, with or without a structural graft.  Cages are used in pelvic discontinuity where they provide a bridge between the ilium and the ischium, while supporting a cemented cup.  All of the other scenarios are amenable to achieving an adequate rim fit for a cementless component, using a jumbo cup if necessary.

 

REFERENCES: Whiteside LA: Selection of acetabular component, in Steinberg ME, Garino JP (eds): Revision Total Hip Arthroplasty.  Philadelphia, PA, Lippincott Williams and Wilkins, 1999, pp 209-220. 

Berry DJ, Muller ME: Revision arthroplasty using an anti-protrusio cage for massive acetabular bone deficiency.  J Bone Joint Surg Br 1992;74:711-715. 

11.         Mechanical reduction of the pain associated with the condition shown in Figure 6 can be accomplished through the use of a cane on the contralateral side.  Similarly, if this patient must carry any type of load in his or her arms, it should be carried

 

1-         on the ipsilateral side.

2-         on the contralateral side.

3-         in a backpack.

4-         directly in front with both arms.

5-         with a broad, padded strap on both shoulders.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Patients with diseased hips often must carry objects while walking, yet they are rarely instructed on which hand to use.  The patient should be directed to carry the object on the ipsilateral side, just the opposite of the side he or she would use a cane.  The cane pushes up on the weight of the body so that when the patient is carrying a load, the weight in the hand on the same side as the hip pushes up on the weight of the body, but now the patient has the fulcrum of the hip in between.  Tan and associates mathematically determined the hip forces that result when a load is carried in the ipsilateral hand versus the contralateral hand.  Using a free-body diagram of a single-leg supported stance, they found that when a load was carried in the contralateral hand, the resultant forces on the hip were increased considerably.  Conversely, when the weight was carried in the ipsilateral hand, the forces were actually lower than when no weight was carried at all.  Therefore, carrying a weight on the opposite side resulted in hip forces that were substantially greater than when the weight was carried on the same side.

 

REFERENCE: Tan V, Klotz MJ, Greenwald AS, Steinberg ME: Carry it on the bad side!  Am J Orthop 1998;27:673-677.

12.        Figure 7 shows the AP radiograph of a 60-year-old man who has had pain in the thigh for past 6 months.  History reveals that he underwent hip replacement 1 year ago.  The radiographic changes are most likely the result of what process?

 

1-         Microtrauma

2-         Mechanical loosening

3-         Septic loosening

4-         Neoplasia

5-         Congenital anomaly

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The arrows in the radiograph point to circumferential radiolucencies that strongly support the diagnosis of septic loosening.  Radiolucent lines that occur in such a short time are also typical of an infection.

 

REFERENCES: Garvin KL, Hanssen AD: Infection after total hip arthroplasty: Past, present, and future.  J Bone Joint Surg Am 1995;77:1576-1588.

Barrack RL, Harris WH: The value of aspiration of the hip joint before revision total hip arthroplasty.  J Bone Joint Surg Am 1993;75:66-76.

13.        Figure 8 shows the radiograph of a 72-year-old man who has had severe pain in the left hip for the past 3 weeks.  History reveals alcohol abuse.  The next most appropriate step should consist of

 

1-         hip aspiration.

2-         Doppler ultrasound.

3-         AP tomograms.

4-         a CT scan.

5-         a technetium Tc 99m bone scan.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The radiograph reveals destruction of the femoral head with loss of the articular cartilage.  These findings are consistent with an infected hip, and aspiration will confirm the diagnosis.  Although the patient could have advanced osteonecrosis, typically the cartilage interval is maintained and such destruction is rarely associated with osteonecrosis. 

 

REFERENCE: Callaghan JJ, Dennis DA, Paprosky WG, et al (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 157-161.

14.        Which of the following articulation couplings shows the lowest coefficient of friction as tested in the laboratory?

 

1-         Cobalt-on-polyethylene

2-         Cobalt-on-cobalt

3-         Titanium-on-polyethylene

4-         Stainless steel-on-polyethylene

5-         Ceramic-on-ceramic

 

PREFERRED RESPONSE: 5

 

DISCUSSION: Alumina ceramic is highly biocompatible when used as a biomaterial for joint arthroplasty implants.  It has been shown to have good hardness, low roughness, and excellent wettability, therefore resulting in very low friction.  However, it is expensive and limited reports have shown the problem of fracture on impact.  The exact role for ceramic articulations is unknown at present.

 

REFERENCES: Cuckler JM, Bearcroft J, Asgian CM: Femoral head technologies to reduce polyethylene wear in total hip arthroplasty.  Clin Orthop 1995;317:57-63.

Sharkey PF, Hozack WJ, Dorr LD, Maloney WJ, Berry D: The bearing surface in total hip arthroplasty: Evolution or revolution, in Price CT (ed): Instructional Course Lectures 49.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 41-56.

15.        Which of the following is considered the best cementless acetabular reconstruction method when planning for total hip arthroplasty in a patient with developmental dysplasia of the hip (DDH)?

 

1-         Cemented reconstruction with the cup in an anatomic position and cement filling the defect

2-         Medialized component positioning with no femoral head graft, leaving up to 20% of the shell uncovered

3-         High and lateral positioning of the acetabular component with a femoral head graft

4-         Anatomic positioning of a small shell with a 28-mm liner and 4 mm of polyethylene

5-         Anatomic positioning of the cup and a femoral head graft covering 70% of the cup

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Anatomic positioning of the acetabular component has been shown to be the optimal position for reconstruction of the acetabulum in total hip arthroplasty for DDH.  The use of medialized component positioning has been shown to be successful at maximizing the host bone coverage and minimizing the use of bone graft to structurally support the acetabular component.  A small acetabular component can be used successfully as long as the femoral head is also reduced in size to maintain the thickness of the acetabular polyethylene.  High and lateral positioning for the acetabular reconstruction will result in an increase in the joint reaction forces.  In addition, a high and lateral placement will not provide adequate bone to stabilize the reconstruction.  

 

REFERENCES: Numair J, Joshi AB, Murphy JC, Porter ML, Hardinge K: Total hip arthroplasty for congenital dysplasia or dislocation of the hip: Survivorship analysis and long-term results.  J Bone Joint Surg Am 1997;79:1352-1360.

Dorr LD, Tawakkol S, Moorthy M, Long W, Wan Z: Medial protrusio technique for placement of  a porous-coated, hemispherical acetabular component without cement in a total hip arthroplasty in patients who have acetabular dysplasia.  J Bone Joint Surg Am 1999;81:83-92.

Jasty M, Anderson MJ, Harris WH: Total hip replacement for developmental dysplasia of the hip.  Clin Orthop 1995;311:40-45.

16.        Which of the following mechanisms is considered the most common cause of failure of osteoarticular allografts used for articular reconstruction?

 

1-         Osteocyte surface antigens that trigger an immune rejection

2-         Chondrocyte surface antigens that trigger an immune rejection

3-         Graft collapse during revascularization 

4-         Mechanical loosening at the bone-bone junction

5-         Infection via graft contamination

 

PREFERRED RESPONSE: 3

 

DISCUSSION: Mechanical loosening and infection can occur as complications after surgery, but the most common cause of osteoarticular allograft failure is graft collapse during revascularization.  Clinical rejection because of an immune response is an unusual means of failure.

 

REFERENCES: Meyers MH, Akeson W, Convery FR: Resurfacing of the knee with fresh osteochondral allograft.  J Bone Joint Surg Am 1989;71:704-713.

Beaver RJ, Mahomed M, Backstein D, Davis A, Zukor DJ, Gross AE: Fresh osteochondral allografts for posttraumatic defects in the knee:  A survivorship analysis.  J Bone Joint Surg Br 1992;74:105-110.

17.        When compared with a patient who has a subluxated hip, a patient with a dislocated hip who is undergoing acetabular reconstruction for developmental dysplasia of the hip will most likely have

 

1-         an increased need for revision.

2-         a greater limb-length discrepancy.

3-         a decreased rate of postoperative instability.

4-         a decreased rate of wear.

5-         a decreased rate of peroneal nerve palsy.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The rate of revision has been found to be significantly increased in patients with a dislocated hip preoperatively compared with patients with a subluxated hip.  This may be the result of compromised acetabular bone stock.  The rate of nerve palsy may be increased because of the greater degree of lengthening required to reduce the reconstructed hip.  

 

REFERENCES: Numair J, Joshi AB, Murphy JC, Porter ML, Hardinge K: Total hip arthroplasty for congenital dysplasia or dislocation of the hip: Survivorship analysis and long-term results.  J Bone Joint Surg Am 1997;79:1352-1360.

Schmalzried TP, Noordin S, Amstutz HC: Update on nerve palsy associated with total hip replacement.  Clin Orthop 1997;344:188-206.

18.        The anticoagulant effect of the low-molecular-weight heparins (LMWH) is mediated by the binding affinity of antithrombin III to which of the following coagulation factors?

 

1-         III

2-         V

3-         IX

4-         Xa

5-         XII

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Standard heparin mediates its anticoagulant effect largely through its interaction with antithrombin III.  A conformational change in antithrombin III occurs that markedly accelerates its ability to inactivate the coagulation enzymes thrombin factor (II), factor Xa, and factor IXa.  In contrast, LMWHs do not contain the necessary saccharide units to bind thrombin and antithrombin III simultaneously.  The anticoagulant effect of LMWHs involves binding of antithrombin III to factor Xa.

 

 

REFERENCE: Hirsh J, Dalen JE, Anderson DR, et al: Oral anticoagulants: Mechanism of action, clinical effectiveness, and optimal therapeutic range.  Chest 1998;114:445S-469S.

19.        The primary purpose of obtaining the radiograph shown in Figure 9 is to assess

 

1-         the anterior column of the acetabulum.

2-         the acetabular rim.

3-         the os acetabulae.

4-         anterior coverage of the femoral head.

5-         femoral anteversion.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The radiograph shows a faux profil view of the hip.  The primary purpose of this view is to evaluate anterior coverage of the femoral head.

 

REFERENCES: Beaty JH (ed): Orthopaedic Knowledge Update 6.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 455-492.

Ganz R, Klaue K, Vinh TS, Mast JW: A new periacetabular osteotomy for the treatment of hip dysplasias: Technique and preliminary results.  Clin Orthop 1988;232:26-36.

Lequesne M, deSez S: Le faux profil du bassin: Nouvelle incidence radiographique pour l’etude de la hance.  Son utilite dans les dysplasies et les differentes coxopathies.  Rev Rhum Mal Osteoartic 1961;28:643.

20.       Figure 10 shows the radiograph of an active 75-year-old woman who reports severe leg pain after a fall.  Management should consist of

 

1-         a total hip arthroplasty with a long-stem prosthesis.

2-         a resection arthroplasty with skeletal traction.

3-         hemiarthroplasty with a long-stem prosthesis.

4-         retention of the prosthesis and open reduction and internal fixation.

5-         closed treatment with skeletal traction.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The patient has a comminuted fracture of the proximal femur and joint space narrowing of the acetabulum.  Therefore, the prosthesis should be converted to a total hip arthroplasty.  Because there is extensive comminution, the revision stem should bypass the area of bone loss by two bone diameters.  A hemiarthroplasty is not indicated because the patient has no acetabular cartilage.  Open reduction and internal fixation may not stabilize the prosthesis.  A resection arthroplasty or treatment in traction will not leave the patient with adequate function.

 

REFERENCES: Garbuz DS, Masri BA, Duncan CP: Periprosthetic fractures of the femur: Principles of prevention and management, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 237-242.

Montijo H, Ebert FR, Lennox DA: Treatment of proximal femur fractures associated with total hip arthroplasty.  J Arthroplasty 1989;4:115-123.

21.        Which of the following procedures is considered most appropriate in patients with rheumatoid arthritis?

 

1-         Hip arthrodesis

2-         Osteotomy of the hip

3-         Core decompression of the hip

4-         Synovectomy of the knee

5-         Unicondylar knee arthroplasty

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Synovectomy of the knee prior to loss of articular cartilage has been shown to consistently relieve pain in patients with rheumatoid arthritis.  Partial knee replacement will not arrest the process of joint destruction.  Osteotomy of the hip has not been found to be a successful procedure in patients with rheumatoid arthritis.  Hip arthrodesis should not be considered because of the multiarticular involvement in patients with rheumatoid arthritis.  Core decompression of the hip has not been shown to save the femoral head because the necrosis appears to occur simultaneously with the inflammatory joint process.

 

REFERENCES: Granberry WM, Brewer EJ Jr: Early surgery in juvenile rheumatoid arthritis, in Calundruccio RA (ed): Instructional Course Lectures XXIII.  St Louis, MO, CV Mosby, 1974, pp 32-37.

Stuchin SA, Johanson NA, Lachiewicz PF, Mont MA: Surgical management of inflammatory arthritis of the adult hip and knee, in Zuckerman JD (ed): Instructional Course Lectures 48.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 93-109.

22.       In a patient who has rheumatoid arthritis with acetabular protrusion, what is the best biomechanical position for the cup with respect to the preoperative center of rotation?

 

1-         Medial and superior

2-         Medial

3-         Lateral and superior

4-         Anterior and inferior

5-         Posterior and lateral

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Acetabular protrusion in patients with rheumatoid arthritis moves the center of hip rotation medially and posteriorly.  Positioning of the acetabular component in a patient with protrusion is best accomplished in the normal (anterior and inferior) position and not in a protruded position.  This has been shown both clinically and in a finite-element analysis.  Any medial positioning will produce impingement of the prosthesis neck on the rim, and superior placement produces improper hip mechanics.

 

REFERENCES: Crowninshield RD, Brand RA, Pedersen DR: A stress analysis of acetabular reconstruction in protrusio acetabuli.  J Bone Joint Surg Am 1983;65:495-499.

Ranawat CS, Dorr LD, Inglis AE: Total hip arthroplasty in protrusio acetabuli of rheumatoid arthritis.  J Bone Joint Surg Am 1980;62:1059-1065.

23.       Figures 11a and 11b show the radiographs of a 50-year-old man who was struck by a car.  Treatment should consist of

 

1-         cemented bipolar hemiarthroplasty.

2-         cementless bipolar hemiarthroplasty.

3-         hybrid total hip arthroplasty.

4-         cementless total hip arthroplasty.

5-         open reduction and internal fixation.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The patient has a displaced femoral neck fracture.  Although the treatment remains controversial, most clinicians advocate either a closed or open reduction in younger active patients.  Achieving an anatomic reduction is necessary to avoid loss of reduction, nonunion, or osteonecrosis.  An acceptable reduction may have up to 15° of valgus angulation and 10° of posterior angulation.  Parallel multiple screws or pins are the most common method of internal fixation.  Prosthetic replacement is generally reserved for older and less active individuals.

 

REFERENCES: Callaghan JJ, Dennis DA, Paprosky WG, et al (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 97-108.

Asnis SE, Wanek-Sgaglione L: Intracapsular fractures of the femoral neck: Results of cannulated screw fixation.  J Bone Joint Surg 1994;76A:1793-1803.

24.       One advantage of using onlay strut allograft in femoral revision surgery is that it can

 

1-         provide some structural support to host bone.

2-         provide better osteoconductive properties than cancellous graft.

3-         completely incorporate into the host femur to restore bone stock.

4-         be used for cavitary defects of the femur.

5-         be used as a primary structural support for the femoral component.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Onlay grafts can provide more structural support than morcellized grafts.  They are more easily incorporated into the host femur than bulk segmental total femur allografts; however, the incorporation is never complete.  The use of onlay grafts is principally directed at addressing segmental defects of the femur; their use can be applied with either cementless or cement fixation of the femoral stem.

 

REFERENCES: Emerson RH Jr, Malinin TI, Cuellar AD, Head WC, Peters PC: Cortical strut allografts in the reconstruction of the femur in revision total hip arthroplasty: A basic science and clinical study.  Clin Orthop 1992;285:35-44.

Pak JH, Paprosky WG, Jablonsky WS, Lawrence JM: Femoral strut allografts in cementless revision total hip arthroplasty.  Clin Orthop 1993;295:172-178.

Head WC, Emerson RH Jr, Malinin TI: Structural bone grafting for femoral reconstruction.  Clin Orthop 1999;369:223-229.

25.       Which of the following methodologies has been proven to be effective in reducing the use of homologous blood transfusion following total hip arthroplasty (THA)?

 

1-         Type of postoperative anticoagulation

2-         Preoperative autologous blood donation

3-         General anesthesia

4-         Cementless fixation of the components

5-         The use of wound drains

 

PREFERRED RESPONSE: 2

 

DISCUSSION: A variety of methodologies have been used to decrease the need for homologous blood transfusions following THA.  Some of the effective strategies include preoperative donation of autologous units, intraoperative salvage and recycling, preoperative injection of erythropoietin, and regional anesthesia.  Cementless fixation and use of wound drains have been shown to increase the blood loss with THA.

 

REFERENCES: Huo MH, Paly WL, Keggi KJ: Effect of preoperative autologous blood donation and intraoperative and postoperative blood recovery on homologous blood transfusion requirement in cementless total hip replacement operation.  J Am Coll Surg 1995;180:561-567.

Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB: An analysis of blood management in patients having a total hip or knee arthroplasty.  J Bone Joint Surg Am 1999;81:2-10.

Ritter MA, Keating EM, Faris PM:  Closed wound drainage in total hip or total knee replacement: A prospective, randomized study.  J Bone Joint Surg Am 1994;76:35-38.

26.       A 67-year-old man is requesting revision surgery because of continued pain in the knee after undergoing a total knee replacement 2 years ago.  Examination reveals that the knee is not warm, the incision is well-healed, and the skin has normal coloration and hair formation.  No varus or valgus instability is noted, and knee range of motion is 5° to 100°.  Laboratory studies show an erythrocyte sedimentation rate of 15 mm/h and a WBC of 5,000/mm³.  Aspiration of the knee reveals clear fluid that shows no growth on culture.  Radiographs reveal an appropriately positioned cruciate-retaining cemented total knee arthroplasty that is well-fixed.  What is the probability that the patient’s pain will be improved with revision surgery?

 

1-         5%

2-         10%

3-         40%

4-         60%

5-         90%

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The patient has a well-fixed and aligned painful total knee replacement.  The success rate of revision knee replacement for pain when no mechanical problem can be identified is approximately 40%.  The critical step is to rule out the presence of infection with appropriate laboratory studies and aspiration.  If no infection is detected, revision should be avoided.

 

REFERENCES: Rand JA: Planning for revision total knee arthroplasty, in Zuckerman JD (ed): Instructional Course Lectures 48.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 161-166.

Mont MA, Serna FK, Krackow KA, Hungerford DS: Exploration of radiographically normal total knee replacement for unexplained pain.  Clin Orthop 1996;331:216-220.

27.       For patients undergoing a surgical procedure where the risk of requiring a transfusion is less than 10%, the International Committee of Effective Blood Usage suggests

 

1-         1 unit of autologous blood.

2-         2 units of autologous blood.

3-         1 unit of direct donated blood.

4-         use of cell saver intraoperatively.

5-         no donation is necessary.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: Recent studies have shown a high rate of waste of autologous blood.  Therefore, the Committee does not recommend autologous blood donation for procedures that carry a transfusion risk of 10% or less.

 

REFERENCES: Toy P, Beattie C, Gould S, et al: Transfusion alert: Use of autologous blood.  National Heart, Lung, and Blood Institute Expert Panel on the use of autologous blood.  Transfusion 1992;35:703-711.

Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB: An analysis of blood management in patients having a total hip or knee arthroplasty.  J Bone Joint Surg Am 1999;81:2-10.

28.       Figure 12 shows the radiograph of a 55-year-old man who has severe, painful osteoarthritis of the left hip and is scheduled to undergo a left total hip arthroplasty.  History reveals that he underwent a right total hip arthroplasty 5 years ago that remains pain-free.  Based on the preoperative radiograph, the patient is at greatest risk for what complication?

 

1-         Intraoperative fracture

2-         Deep vein thrombosis

3-         Limb-length discrepancy

4-         Sciatic nerve palsy

5-         Thigh pain

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The patient is at increased risk for limb-length discrepancy because the radiograph shows that the left leg is already longer than the right leg.  To restore the proper biomechanics of the left hip, the left leg may have to be lengthened, further increasing the limb-length discrepancy.  Intraoperative fracture, deep vein thrombosis, sciatic nerve palsy, and thigh pain are commonly associated with total hip arthroplasty, but the patient is not at increased risk for these complications.

 

REFERENCE: Ranawat CS, Rodriguez JA: Functional leg-length inequality following total hip arthroplasty.  J Arthroplasty 1997;12:359-364.

29.       Figures 13a and 13b show the preoperative radiographs of a 60-year-old woman who is scheduled to undergo total knee arthroplasty under epidural anesthesia.  Postoperatively she reports a burning sensation on the dorsum of her foot despite the administration of IV analgesics through a patient-controlled analgesia (PCA) pump.   Management should now include

 

1-         increasing the dose released by the PCA.

2-         administering a different narcotic with the PCA pump.

3-         elevating the leg.

4-         releasing the dressings and knee flexion.

5-         immediately returning to the operating room for revision.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The patient has a significant flexion contracture and valgus deformity; therefore, the risk of peroneal nerve injury is increased.  Idusuyi and Morrey noted that epidural anesthesia also increases the risk of peroneal nerve injury.  The initial symptom can be a burning sensation on the foot, followed by pain and then motor weakness.  Initial management should consist of release of the dressings and knee flexion.  

 

REFERENCES: Idusuyi OB, Morrey BF: Peroneal nerve palsy after total knee arthroplasty: Assessment of predisposing and prognostic factors.  J Bone Joint Surg Am 1996;78:177-184.

Rose HA, Hood RW, Otis JC, Ranawat CS, Insall JN: Peroneal nerve palsy following total knee arthroplasty: A review of The Hospital for Special Surgery experience.  J Bone Joint Surg Am 1982;64:347-351.

30.       Figures 14a and 14b show the plain radiographs of an 85-year-old woman who has had severe pain in the right knee for the past 4 months.  Management should consist of

 

1-         a hinged knee brace.

2-         arthroscopic debridement.

3-         high tibial osteotomy.

4-         total knee arthroplasty.

5-         osteochondral grafts.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The patient has osteonecrosis of the lateral femoral condyle with collapse of the articular surface.  Because there is already collapse of the articular surface, a total knee arthroplasty is the treatment of choice.  The results of total knee arthroplasty in these patients are usually excellent.  However, knee replacement is only a resurfacing procedure, and some patients with global osteonecrosis of the distal femur may have residual pain after knee replacement.  High tibial osteotomy may be indicated in younger patients who have a varus deformity and localized osteonecrosis.  Arthroscopic surgery would provide minimal relief for this patient because there is already collapse of the articular surface.  A hinged knee brace will not adequately unload the joint.  An osteochondral allograft should be considered only for younger patients with localized osteonecrosis.

 

REFERENCES: Bergman NR, Rand JA: Total knee arthroplasty in osteonecrosis.  Clin Orthop 1991;273:77-82.

Lotke PA, Abend JA, Ecker ML: The treatment of osteonecrosis of the medial femoral condyle.  Clin Orthop 1982;171:109-116.

31.        The failure of the acetabular component shown in Figure 15 is most likely the result of the use of a 32-mm head and  

 

1-         the material properties of the polyethylene.

2-         the initial alignment of the component.

3-         overuse of the component by the patient.

4-         failure to stabilize the cup with screws.

5-         increased femoral head offset.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Astion and associates analyzed 23 acetabular components, out of a total of 173 implanted, that had failed because of either migration or severe osteolysis.  The radiographic appearance of osteolysis was positively associated with the duration that the implant had been in situ.  The prevalence of osteolysis was also significantly greater in acetabular components with an outer diameter of 55 mm or less (a polyethylene thickness of 8.5 mm or less).  Thirteen of the 23 components were revised at a mean of 70 months after the index operation.  Examination of the retrieved acetabular components revealed extensive polyethylene damage on the articular and back surfaces of the liners.  Cracks in the polyethylene rim of the liner and deformation of the antirotation notch in the polyethylene rim were common findings.  The density of the polyethylene was greater than expected, and more particles than anticipated had not fused with the surrounding polyethylene.  Factors related to both the design and the material contributed to the failure of these porous-coated anatomic acetabular components.

 

REFERENCE: Astion DJ, Saluan P, Stulberg BN, Rimnae CM, Li S: The porous-coated anatomic total hip prosthesis: Failure of the metal-backed acetabular component.  J Bone Joint Surg Am 1996;78:755-766.

32.       The use of elevated rim acetabular liners and long femoral necks may result in

 

1-         increased abductor tension.

2-         an increased likelihood of impingement.

3-         an increased likelihood of osteolysis.

4-         restricted hip range of motion.

5-         dissociation of polyethylene from the acetabular cup.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Elevated rim acetabular liners may improve the anteversion of the acetabular component that, in turn, might improve the stability of the hip replacement through a range of motion.  Long femoral necks with skirts will increase the abductor tension and may be necessary to equalize limb lengths.  However, either of these measures may increase the likelihood of impingement of the femoral component on the acetabular rim and may lead to dislocation.  The restricted range of motion secondary to impingement has been shown to lead to further polyethylene wear that may result in osteolysis.

 

REFERENCES: Cobb TK, Morrey BF, Ilstrup DM: The elevated rim acetabular liner in total hip arthroplasty: Relationship to postoperative dislocation.  J Bone Joint Surg Am 1996;78:80-86.

Urquhart AG, D’Lima DD, Venn-Watson E, Colwell CW Jr, Walker RH: Polyethylene wear after total hip arthroplasty: The effect of a modular femoral head with an extended flange-reinforced neck.  J Bone Joint Surg Am 1998;80:1641-1647.

33.        Cementation technique has a definite influence on the long-term survival of cemented femoral components.  Both clinical and autopsy studies support the use of a cement mantle with a thickness of how many millimeters?

 

1-         0.5

2-         1

3-         2

4-         3

5-         4

 

PREFERRED RESPONSE: 3

 

DISCUSSION: Long-term radiographic analysis of cemented total hips supports the creation of a 2- to 5-mm cement mantle in the proximal medial region.  Autopsy studies have shown that the incidence of crack formation was greatest when the cement mantle was less than 2 mm.

 

REFERENCES: Ebramzadeh E, Sarmiento A, McKellop HA, Llinas A, Gogan W: The cement mantle in total hip arthroplasty: Analysis of long-term radiographic results.  J Bone Joint Surg Am 1994;76:77-87.

Jasty M, Maloney WJ, Bragdon CR, O’Connor DO, Haire T, Harris WH: The initiation of failure in cemented femoral components of hip arthroplasty.  J Bone Joint Surg Br 1991;73:551-558.

Maloney WJ III: The cemented femoral component, in Callaghan JJ, Rubash HE, Rosenberg AG (eds): The Adult Hip.  Philadelphia, PA, Lippincott-Raven, 1998, pp 965-966.

 

34.       A 73-year-old man is scheduled to have mature heterotopic bone resected from around his left total hip arthroplasty.  The optimal management for prophylaxis against the return of heterotopic bone postoperatively is radiation therapy that consists of

 

1-         400 cGy in one dose.

2-         700 cGy in one dose.

3-         1,000 cGy in five doses.

4-         2,000 cGy in 10 doses.

5-         3,000 cGy in 10 doses.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Patients require prophylaxis for heterotopic bone after resection to prevent recurrence.  The optimal management has been found to be a dose of 700 cGy in one dose delivered either pre- or postoperatively.  A dose of 2,000 to 3,000 cGy is considered excessive.  Radiation therapy consisting of 1,000 cGy in five doses is an acceptable prophylaxis; however, it will require an extended hospital stay of 3 to 4 days and is more problematic for the patient who must be transported for radiation therapy for 5 days.  A dose of 400 cGy is not as effective in prophylaxis for heterotopic bone formation.   

 

REFERENCES: Healy WL, Lo TC, DeSimone AA, Rask B, Pfeifer BA: Single-dose irradiation for the prevention of heterotopic ossification after total hip arthroplasty: A comparison of doses of five hundred and fifty and seven hundred centigray.  J Bone Joint Surg Am 1995;77:590-595.

Pelligrini VD Jr, Gregoritch SJ: Preoperative irradiation for the prevention of heterotopic ossification following total hip arthroplasty.  J Bone Joint Surg Am 1996;78:870-881.

Pelligrini VD Jr, Konski AA, Gastel JA, Rubin P, Evarts CM: Prevention of heterotopic ossification with irradiation after total hip arthroplasty: Radiation therapy with a single dose of eight hundred centigray administered to a limited field.  J Bone Joint Surg Am 1992;74:186-200.

35.       Which of the following is considered a potential advantage in prophylaxis for the prevention of deep venous thrombosis associated with the use of low-molecular weight heparin (LMWH) as compared with fixed-dose unfractionated heparin?

 

1-         Reduction in free fibrinogen radicals

2-         Reduction in bleeding complications

3-         Increased venous flow

4-         Improved bioavailability

5-         Inhibition of factors V, VI, and IX

 

PREFERRED RESPONSE: 4

 

DISCUSSION: One possible reason for improved efficacy of LMWHs is the relative improved bioavailability compared with that of unfractionated heparin.  This is, in part, the result of a more predictable dose response and a longer half-life.  There is no alteration of venous flow, and the rate of bleeding complications is the same or slightly higher than that of other prophylactic agents.  

 

REFERENCES: Colwell CW Jr, Spiro TE, Trowbridge AA: Use of enoxaparin, a low-molecular weight heparin, and unfractionated heparin for the prevention of deep venous thrombosis after elective hip replacement: A clinical trial comparing efficacy and safety.  J Bone Joint Surg Am 1994;76:3-14.

Bara L, Billaud E, Kher A, Samama M: Increased anti-Xa bioavailability for a low-molecular weight heparin (PK 10169) compared with unfractionated heparin.  Semin Thromb and Hemost 1985;11:316-317.

Paiement GD: Prevention and treatment of venous thromboembolic disease complications in primary hip arthroplasty patients, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 331-335.

36.       Figure 16 shows the radiograph of a 75-year-old man who has progressive groin pain and a limp following total hip replacement.  At revision surgery, the anterior and posterior columns of the acetabulum are noted to be intact.  The optimal surgical technique for acetabular component reconstruction is a

 

1-         threaded (screw-in) cup with a hydroxyapatite coating.

2-         protrusio cage reconstruction with a cemented cup.

3-         large cementless cup with bone grafting of defects.

4-         small cup with a high and lateral hip center.

5-         bulk allograft reconstruction of the defect with a cemented cup.

 

PREFERRED RESPONSE: 3

 

DISCUSSION: Large cementless acetabular components have been shown to perform well in revision acetabular reconstruction.  The use of such components is predicated on the presence of adequate anterior and posterior column bone.  If a good press-fit can be achieved between the anterior and posterior columns, typically, the remaining defects can be filled with morcellized bone graft.  Protrusio cages are typically used in situations where it is not possible to obtain adequate fixation with a large acetabular component.  The use of a high hip center with small sockets is more typical of primary arthroplasty in patients with developmental dysplasia of the hip.  Bulk acetabular allografts for large segmental defects might be necessary in certain situations, although the use of bulk allografts has resulted in a high failure rate after 5 years.  Early results of the use of protrusio cages and bone grafting for large segmental defects have been favorable.

 

REFERENCES: Petrera P, Rubash HE:  Revision total hip arthroplasty: The acetabular component.  J Am Acad Orthop Surg 1995;3:15-21. 

Lachiewicz PF, Poon ED: Revision of a total hip arthroplasty with a Harris-Galante porous-coated acetabular component inserted without cement: A follow-up note on the results at five to twelve years.  J Bone Joint Surg Am 1998;80:980-984.

37.        Which of the following is a recognized consequence of hip fusion?

 

1-         Low back pain

2-         Contralateral knee laxity

3-         Difficulty delivering children

4-         Meralgia paresthetica

5-         Contralateral abductor weakness

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Low back pain is an expected long-term complication of fusion; ipsilateral knee laxity is frequently encountered, as is degeneration of the contralateral hip.  Hip fusion is equally valuable for both men and women, with both genders reporting satisfactory sexual function.  Female patients often deliver by elective Cesarean section, although vaginal deliveries are reported. 

 

REFERENCES: Liechti R (ed): Hip Arthrodesis and Associated Problems.  Berlin, Germany, Springer-Verlag, 1978, pp 109-117.

Sponseller PD, McBeath AA, Perpich M: Hip arthrodesis in young patients: A long-term follow-up study.  J Bone Joint Surg Am 1984;66:853-859.

38.        Treatment of a cruciate-retaining total knee that is unstable in flexion is best accomplished by

 

1-         revising the implant to a posterior stabilized device.

2-         revising the implant with a thinner polyethylene insert.

3-         revising the implant with a larger femoral component.

4-         limiting flexion to only 90°.

5-         using quadriceps conditioning exercises and a derotation brace.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Pagnano and associates revised 25 painful primary posterior cruciate-retaining total knee arthroplasties for flexion instability.  The patients shared typical clinical presentations that included a sense of instability without frank giving way, recurrent knee joint effusion, soft-tissue tenderness involving the pes anserine tendons and the retinacular tissue, posterior instability of 2+ or 3+ with a posterior drawer or a posterior sag sign at 90° of flexion, and above-average motion of the total knee arthroplasty.  Twenty-two of the knee replacements were revised to posterior stabilized implants, and three underwent tibial polyethylene liner exchange only.  Nineteen of the 22 knee replacements revised to a posterior stabilized implant showed marked improvement after the revision surgery.  Only one of the three knee replacements that underwent tibial polyethylene exchange was improved.  Flexion instability can be a cause of persistent pain and functional impairment after posterior cruciate-retaining total knee arthroplasty.  Revision surgery that focuses on balancing the flexion and extension spaces, in conjunction with a posterior stabilized knee implant, seems to be a reliable treatment for symptomatic flexion instability after posterior cruciate-retaining total knee arthroplasty.

 

REFERENCE: Pagnano MW, Hanssen AD, Lewallen DG, Stuart MJ: Flexion instability after primary posterior cruciate-retaining total knee arthroplasty.  Clin Orthop 1998;356:39-46.

39.       The stiffness of a 16-mm femoral stem is mostly influenced by the

 

1-         elastic modulus of the material.

2-         surface coating or treatment.

3-         diameter of the femoral stem.

4-         length of the femoral stem.

5-         ultimate tensile strength.

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The stiffness is most influenced by the geometry, in particular the diameter of the stem.  The bending rigidity increases to the fourth power of the radius.  The elastic modulus of the material increases as a direct linear relationship.  The surface coating does not affect the bending rigidity greatly unless it increases the diameter significantly.

 

REFERENCE: Simon SR (ed): Orthopaedic Basic Science.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, p 458.

40.       Figures 17a and 17b show the AP and lateral radiographs of a 75-year-old woman who reports giving way and shifting of the knee, particularly when she is descending stairs or ambulating on level surfaces.  History reveals a total knee replacement 5 years ago.  Treatment should consist of

 

1-         extra-articular ligament repair.

2-         resection arthroplasty with a cement spacer.

3-         revision of the tibial tray.

4-         revision of the patella to an all-polyethylene component.

5-         revision to a posterior cruciate-substituting implant.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The radiographs show well-fixed components of a posterior cruciate-retaining total knee replacement.  The relative position of the femoral component is anteriorly subluxated relative to the tibial component.  The AP radiograph shows that the articular space is markedly asymmetric, indicating either failure or fracture of the polyethylene or subluxation of the femur relative to the tibia.  The patient’s symptoms suggest a failure of the posterior cruciate ligament that is consistent with the radiographic findings; therefore, the treatment of choice is revision to a posterior cruciate-substituting implant.

 

REFERENCE: Pagnano MW, Cushner FD, Scott WN: Role of the posterior cruciate ligament in total knee arthroplasty.  J Am Acad Orthop Surg 1998;6:176-187.

41.        Factors contributing to an increased risk of hip fracture include reduced bone mineral density of the femoral neck, cognitive status of the individual, and

 

1-         increased trunk muscle activity.

2-         increased muscle activity about the hip.

3-         increased muscle activity about the shoulder.

4-         a flexed hip configuration during impact.

5-         falling forward on an outstretched hand.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The etiology of hip fractures in the elderly is multifactorial, and intervention and prevention can occur at multiple points.  Events leading to hip fracture from a fall include fall initiation (during which the individual’s neuromuscular status, cognitive status, and vision come into play along with environmental hazards); fall descent (fall direction toward the side being the most influential, energy content of the fall, and fall height, along with muscle activity of the muscles of the thigh); impact (impact location, soft-tissue attenuation such as from trochanteric padding or from overlying fat, impact surface, and muscle activity); and the structural capacity of the femur (bone mineral density, bone geometry, and bone architecture).

 

Hayes and Myers noted that striking the ground in a stiff state with the trunk muscles contracted actually increased the peak impact force, whereas falling in a relaxed state actually reduced peak impact force.  Flexion of the trunk at impact had no bearing on the impact force.  Direction of the fall was important; falls to the side, not forward, were associated with an increased risk of hip fracture.  Increased muscle activity about the hip is thought to be associated with spontaneous fractures of the hip and may actually account for up to 25% of hip fractures; however, it is not related to fractures resulting from a fall.

 

REFERENCE: Hayes WC, Myers ER: Biomechanical considerations of hip and spine fractures in osteoporotic bone, in Springfield D (ed): Instructional Course Lectures 46.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 431-438.

42.       A healthy 70-year-old man has a swollen knee after undergoing a knee replacement 10 years ago.  Aspiration of the knee reveals cloudy, viscous synovial fluid.  Laboratory studies show an erythrocyte sedimentation rate of 10 mm/h and a C-reactive protein level of less than 0.5.  What is the most likely diagnosis?

 

1-         Infected total knee arthroplasty

2-         Polyethylene wear-related synovitis

3-         Rheumatoid arthritis synovitis

4-         Gout

5-         Tibial component loosening

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Polyethylene wear debris can result in significant synovitis and subsequent cloudy appearing synovial fluid.  Typically, laboratory studies show a WBC of less than 30,000/mm³ and no left shift.  Cytologic examination can reveal intra-articular polyethylene particles.  Infected total knee arthroplasty is extremely uncommon in a healthy, immune-competent patient who has a normal preoperative erythrocyte sedimentation rate and C-reactive protein level.

 

REFERENCE: Barrack RL, Jennings RW, Wolfe MW, Bertot AJ: The value of preoperative aspiration before total knee revision.  Clin Orthop 1997;345:8-16.

43.       The insurance carrier of a patient who underwent total knee arthroplasty 4 days ago is now demanding that the patient be discharged from the hospital.  However, examination reveals that the patient has a range of motion of only 10° to 55°, and the patient is concerned whether she will ever move her knee normally.  The insurance company representative should be advised that

 

1-         discharge at this time may result in loss of motion and the necessity of manipulation under anesthesia.

2-         the insurance company has no right to make such demands on the surgeon or the patient.

3-         if the patient is discharged and fails to regain full motion, she will most likely file a suit against the insurance company.

4-         the patient will require a follow-up examination in 6 weeks to evaluate her progress.

5-         the patient will be given an extra set of exercises to perform at home.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Examination findings that show flexion of only 55° at discharge should alert the surgeon that the patient will require close scrutiny and follow-up.  Mauerhan and associates examined the records of 745 patients who had a primary total knee arthroplasty from 1993 to 1996.  At their institution, development and implementation of clinical pathways resulted in a significant decrease in the average length of stay, beginning in 1993 with 6.4 days +/- 1.8 days and progressively decreasing to 4.4 days +/- 1.0 days in 1996.  The rate of manipulation (patients manipulated at 6 weeks/total number of patients receiving total knee arthroplasty) was 6.0% in 1993, 11.3% in 1994, 13.5% in 1995, and 12.0% in 1996.  In the period of 1993 to 1996, patients requiring manipulation consistently had a lower range of motion of 69.0° +/- 10° at the time of discharge compared with patients not requiring manipulation who had a range of motion of 80.7° +/- 10.6°.  In this era of outpatient services, however, another solution would be to arrange for outpatient physical therapy on a more frequent basis and to see the patient more frequently in the office until an acceptable range of motion is established.

 

REFERENCE: Mauerhan DR, Mokris JG, Ly A, Kiebzak GM: Relationship between length of stay and manipulation rate after total knee arthroplasty.  J Arthroplasty 1998;13:896-900.

44.       Figure 18 shows the radiograph of a patient with a total hip arthroplasty dislocation.  During revision, increasing the diameter of the femoral head while maintaining the ratio of head-to-neck diameter constant has the effect of

 

1- increasing the force to dislocation of the femoral head.

2- increasing the range of motion until impingement of the neck on the liner.

3- decreasing the resisting moment to dislocation of the femoral head.

4- decreasing the range of motion until dislocation of the femoral head.

5- decreasing the range of motion until impingement of the neck on the liner.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Although there is strong clinical and laboratory evidence that suggests smaller head size is linked with lower rates of polyethylene wear, moving to the use of 22-mm heads from larger sizes would tend to increase the dislocation rate.  The key premise to this argument is that the absolute size of the femoral neck remains unchanged.  While neck diameters were appropriate for the early monoblock femoral components, the use of modular femoral stems allows the surgeon to place 22-mm heads onto the same neck and trunion as used by larger heads.  This has the effect of lessening the head-to-neck diameter ratio, which then accentuates the rate of impingement and dislocation.  Reducing the neck diameter in proportion to the head diameter would eliminate the range-of-motion penalty accompanying head size reduction.

 

Scifert and associates used a three-dimensional finite element model to study various combinations of femoral head size and neck ratios.  They found that increasing the diameter of the femoral head while maintaining a constant head-to-neck diameter had the effect of significantly increasing the resisting moment necessary to induce a dislocation.  The higher the head-to-neck ratio, the greater the range of motion until impingement and the greater the range of motion to dislocation. 

 

REFERENCE: Scifert CF, Brown TD, Pedersen DR, Callaghan JJ: A finite element analysis of factors influencing total hip dislocation.  Clin Orthop 1998;355:152-162.

45.       During primary total knee arthroplasty with trial implants in place, the surgeon notes technically satisfactory patellar resurfacing and restoration of a physiologic mechanical axis but excessively lateral patellar tracking.  Treatment should now include

 

1-         a lateral retinacular release.

2-         a tubercle transfer to reduce the Q angle.

3-         a repeat of the tibial and femoral cuts to introduce 5° of varus.

4-         release of the popliteus.

5-         medial vastus advancement.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The most common causes of patellar instability after total knee arthroplasty are valgus malalignment, internal rotation of the femoral or tibial component, medialization of the femoral component, errors in patellar preparation and resurfacing, and failure to perform a lateral release.  These factors should be addressed before considering capsular closure.  Distal extensor mechanism realignment should be avoided because of the complication rate.  The proximal extensor mechanism would not adequately compensate for implant malrotation.

 

REFERENCES: Barnes CL, Scott RD: Patellofemoral complications of total knee replacement, in Heckman JD (ed): Instructional Course Lectures 42.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1993, pp 309-314.

Hungerford DS: Alignment in total knee replacement, in Jackson DW (ed): Instructional Course Lectures 44.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 455-468.

46.       Figure 19 shows the current radiograph of a 48-year-old man who reports hip pain and marked difficulty walking after undergoing revision of a failed total hip replacement 2 years ago.  What is the mechanism of failure?

 

1-         Fatigue

2-         Crevice corrosion

3-         Galvanic corrosion

4-         Loosening

5-         Wear

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Fatigue from repetitive loading of the stem with the distal aspect well-fixed resulted in stem failure.  If the stem had loosened, it would not have broken.  Crevice corrosion occurs at a taper interface; galvanic corrosion occurs at the junction of two metals of differing electrochemical potentials, not along a uniform portion of the implant.

 

REFERENCES: Simon SR (ed): Orthopaedic Basic Science.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486.

Gruen TA, McNiece GM, Amstutz HC: “Modes of Failure” of cemented stem-type femoral components: A radiologic analysis of loosening.  Clin Orthop 1979;141:17-27.

47.       Torsional moments about the longitudinal axis of a total hip arthroplasty show what change during stair climbing compared with walking?

 

1-         Increase by a factor of 50% during stair climbing

2-         Increase by a factor of 100% during stair climbing

3-         Increase only during the first 6 to 8 weeks following implantation, then revert to normal

4-         Decrease by a factor of 50% during stair descent

5-         Decrease by a factor of 100% during stair descent

 

PREFERRED RESPONSE: 2

 

DISCUSSION: The magnitudes of out-of-plane loads on a total hip replacement during activities of daily living can be substantial.  Bergmann and associates studied these forces about two instrumented hip prostheses.  They noted that the torsional moment about the hip during stair climbing is twice as high as during slow walking and that similar moments are generated during slow jogging.  Higher loads were noted when the patients stumbled without falling.  They also noted that the torsional moments observed in vivo were close to or even exceeded the experimentally determined limits of the torsional strength of implant fixations.

 

REFERENCES: Hurwitz DE, Andriacchi TP: Biomechanics of the hip, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip.  Philadelphia, PA, Lippincott Raven, 1998, pp 75-85. 

Bergmann G, Graichen F, Rohlmann A: Is staircase walking a risk for the fixation of hip implants?  J Biomech 1995;28:535-553.

48.       When converting the knee shown in Figure 20 to a total knee arthroplasty, satisfactory outcome can be expected in what percent of patients?

 

1-         Less than 5%

2-         Less than 50%

3-         60%

4-         80%

5-         90%

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Naranja and associates reviewed 37 knees (35 patients, with 28 women and 7 men) without any motion that were converted to total knee arthroplasties.  After an average follow-up of 90 months, the patients lacked an average of  7° of extension and had 62° of flexion.  Results showed a short-term complication rate of 24% (stiffness requiring manipulation, delayed wound healing, and recurrent hemarthrosis), a major complication rate of 35% (patellar tendon or tibial tubercle avulsion, persistent pain requiring arthrodesis, loosening, and joint stiffness requiring arthrotomy for excision of scar tissue), and an infection rate of 14%.  The total complication rate was 57%.  A satisfactory outcome (no pain and an unlimited ambulation distance) was obtained in only 10 patients (29%).  There was no relationship between results and the angle at which the knee was ankylosed preoperatively.  This study revealed that although success in reconstructing a previously ankylosed or arthrodesed knee is possible, the lack of consistent adequate motion and the complication rate may suggest that the surgeon reconsider the risks and benefits of this difficult procedure.

 

REFERENCE: Naranja RJ Jr, Lotke PA, Pagnano MW, Hanssen AD: Total knee arthroplasty in a previously ankylosed or arthrodesed knee.  Clin Orthop 1996;331:234-237.

49.       The specificity of intraoperative frozen sections obtained for the evaluation of infected total hip arthroplasty may be improved by

 

1-         setting the threshold for diagnosis to 10 polymorphonuclear leukocytes per high-powered field.

2-         setting the threshold for diagnosis to 15 polymorphonuclear leukocytes per high-powered field.

3-         ensuring that each sample is obtained and submitted in a truly random fashion.

4-         ensuring that polymorphonuclear leukocyte counts are obtained in a truly random fashion.

5-         correlating the frozen section results with those of the intraoperative Gram stain.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Lonner and associates conducted a prospective study to determine the reliability of analysis of intraoperative frozen sections for the identification of infection during 175 consecutive revision total joint arthroplasties (142 hips and 33 knees).  The mean interval between the primary arthroplasty and the revision arthroplasty was 7.3 years (range, 3 months to 23 years).  Of the 175 patients, 23 had at least 5 polymorphonuclear leukocytes per high-powered field on analysis of the frozen sections and were considered to have an infection.  Of these 23 patients, five had 5 to 9 polymorphonuclear leukocytes per high-powered field and 18 had at least 10 polymorphonuclear leukocytes per high-powered field.  The frozen sections for the remaining 152 patients were considered negative. 

 

On the basis of cultures of specimens obtained at the time of the revision surgery, 19 of the 175 patients were considered to have an infection.  Of the 152 patients who had negative frozen sections, three were considered to have an infection on the basis of the results of the final cultures.  Of the 23 patients who had positive frozen sections, 16 were considered to have an infection on the basis of the results of the final cultures; all 16 had frozen sections that showed at least 10 polymorphonuclear leukocytes per high-powered field. 

 

The sensitivity and specificity of the frozen sections were similar regardless of whether an index of 5 or 10 polymorphonuclear leukocytes per high-powered field was used.  Analysis of the frozen sections had a sensitivity of 84% for both indices, whereas the specificity was 96% when the index was 5 polymorphonuclear leukocytes and 99% when it was 10 polymorphonuclear leukocytes.  However, the positive predictive value of the frozen sections increased significantly (P < 0.05), from 70% to 89%, when the index increased from 5 to 10 polymorphonuclear leukocytes per high-powered field.  The negative predictive value of the frozen sections was 98% for both indices.  At least 10 polymorphonuclear leukocytes per high-powered field was predictive of infection, while 5 to 9 polymorphonuclear leukocytes per high-powered field was not necessarily consistent with infection.  Less than 5 polymorphonuclear leukocytes per high-powered field reliably indicated the absence of infection.

 

REFERENCES: Feldman DS, Lonner JH, Desai P, Zuckerman JD: The role of intraoperative frozen sections in revision total joint arthroplasty.  J Bone Joint Surg Am 1995;77:1807-1813. 

Lonner JH, Desai P, Dicesare PE, Steiner G, Zuckerman JD: The reliability of analysis of intraoperative frozen sections for identifying active infection during revision hip or knee arthroplasty.  J Bone Joint Surg Am 1996;78:1553-1558.

Spangehl MJ, Younger AS, Masri BA, Duncan CP: Diagnosis of infection following total hip arthroplasty, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 285-295.

Della Valle CJ, Bogner E, Desai P: Analysis of frozen sections of intraoperative specimens obtained at the time of reoperation after hip or knee resection arthroplasty for the treatment of infection.  J Bone Joint Surg Am 1999;81:684-689.

50.       Figures 21a through 21c show the radiographs of a 70-year-old woman who has persistent pain with activity after undergoing hip revision 6 months ago.  Treatment should now consist of

 

1-         shortening of the femoral neck.

2-         exchange of the acetabular liner.

3-         revision of the femoral component.

4-         revision of both components.

5-         revision of the acetabular component.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The radiographs show disruption of the posterior column of the acetabulum with radiolucencies about the component.  Because the patient requires a stable construct to allow the bone to heal, the treatment of choice is an antiprotrusio cage and a graft.

 

REFERENCES: Gill TJ, Sledge JB, Muller ME: The Burch-Schneider anti-protrusio cage in revision total hip arthroplasty: Indications, principles, and long-term results.  J Bone Joint Surg Br 1998;80:946-953.

Sharkey PF, Hozack WJ, Callaghan JJ, et al: Acetabular fracture associated with cementless acetabular component insertion: A report of 13 cases.  J Arthroplasty 1999;14:426-431.

51.        A patient who underwent a high tibial osteotomy (HTO) is now scheduled to undergo total knee arthroplasty (TKA).  When compared with a patient undergoing primary TKA without a prior HTO, the patient should be advised to expect a higher incidence of

 

1-         limited range of motion.

2-         patella complications.

3-         infection.

4-         loosening.

5-         tibia fracture.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Conversion TKA following a previous HTO can be successful; however, it is associated with poorer clinical results when compared with other primary TKAs.  There is an increased likelihood of poor range of motion that is partially affected by patella infera created from the osteotomy.  Patella infera also results in difficulty with surgical exposure.  There has been no reported increase in the rate of infection, fracture, or loosening.

 

REFERENCE: Mont MA, Alexander N, Krackow KA, Hungerford DS: Total knee arthroplasty after failed high tibial osteotomy.  Orthop Clin North Am 1994;25:515-525. 

52.       Figures 22a and 22b show the radiographs of a patient who reports stiffness of the hip and associated pain.  Management should consist of

 

1-         use of a cane for ambulation.

2-         diphosphonate therapy.

3-         physical therapy and indomethacin.

4-         surgical excision and radiation therapy.

5-         revision arthroplasty.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The patient has grade IV heterotopic ossification with the limb in an abnormal nonfunctional position.  Treatment should consist of excision of the bone to restore hip motion and prophylaxis to prevent recurrent formation.  The best time to excise the bone is controversial, with no conclusive evidence supporting early or late excision.

 

REFERENCES: Pellegrini VD Jr, Koniski AA, Gastel JA, Rubin P, Evarts CM: Prevention of heterotopic ossification with irradiation after total hip arthroplasty: Radiation therapy with a single dose of eight hundred centigray administered to a limited field.  J Bone Joint Surg Am 1992;74:186-200.

Warren SB, Brooker AF Jr: Excision of heterotopic bone followed by irradiation after total hip arthroplasty.  J Bone Joint Surg Am 1992;74:201-210.

53.       Figure 23 shows the radiograph of a 55-year-old man who underwent a total hip arthroplasty 5 years ago.  Management should now consist of

 

1-         an Ogden-type plate with screws and cerclage bands or cables.

2-         allograft bone plates fixed with cerclage cables and wires.

3-         skeletal traction for 8 weeks.

4-         revision of the femoral stem.

5-         resection arthroplasty.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Because the radiograph shows that the femoral stem is loose within the femoral canal and there is a fracture in the distal cement mantle, the stem should be revised.  The Ogden-type plate and the allograft bone plates will reconstruct the femur but will not restore stability to the stem.  Similarly, traction may allow the femur to heal but will not restore stability to the femoral stem within the femur.  Resection arthroplasty is considered a salvage option following failure of the other procedures.

 

REFERENCES: Lewallen DG, Berry DJ: Periprosthetic fracture of the femur after total hip arthroplasty: Treatment and results to date, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 243-249. 

Bethea JS, DeAndrade JR, Fleming LL, Lindenbaum SD, Welch RB: Proximal femoral fractures following total hip arthroplasty.  Clin Orthop 1982;170:95-106. 

54.       Compared with wear rates of metal-on-standard polyethylene bearings (75 to 250 mm/y), the wear rate of metal-on-metal bearings for hip arthroplasty is approximately how many micrometers per year?

 

1-         Less than 0.5

2-         2 to 5

3-         5 to 20

4-         20 to 50

5-         50 to 150

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Studies on older systems, as well as newer designs, have confirmed that metal-on-metal bearing surfaces undergo linear wear of 2 to 5 mm per year.  Ceramic bearing surfaces produced with recent technology perform even better, with a wear rate of 0.5 to 2.5 mm per year.  Clinical wear rates of metal-on-crosslinked polyethylene have not yet been determined.

 

REFERENCES: McKellop H, Park SH, Chiesa R, et al: In vivo wear of three types of metal on metal hip prostheses during two decades of use.  Clin Orthop 1996;329:S128-S140.

Schmalzried TP, Callaghan JJ: Wear in total hip and knee replacements.  J Bone Joint Surg Am 1999;81:115-136.

55.       A follow-up examination of a patient 6 weeks after knee surgery reveals a range of motion from 5° to 55° of flexion.  Which of the following statements best summarizes the role of manipulation under anesthesia for this patient?

 

1-         Manipulation under anesthesia offers the best chance of improving and maintaining the patient’s range of motion.

2-         The gains from manipulation under anesthesia are only temporary and rarely last more than 6 months.

3-         Increasing the frequency and intensity of physical therapy over the next 2 months will have the same effect as manipulation under anesthesia.

4-         The risks of fracture are so great from manipulating a knee that the patient should be advised to live with a limited range of motion.

5-         The patient’s final result will be poor with or without manipulation.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Esler and associates evaluated the use of manipulation under anesthesia in 47 knees.  Manipulation was considered when intensive physical therapy failed to increase flexion to more than 80°.  The mean time from arthroplasty to manipulation was 11.3 weeks, and the mean active flexion before manipulation was 62°.  One year later, the mean gain was 33°.  Definite sustained gains in flexion were achieved even when manipulation was performed 4 or more months after arthroplasty.  An additional 21 patients who met the criteria for manipulation declined the procedure, and despite continued physical therapy, they showed no significant increase in knee flexion.

 

REFERENCE: Esler CN, Lock K, Harper WM, Gregg PJ: Manipulation of total knee replacements: Is the flexion gained retained?  J Bone Joint Surg Br 1999;81:27-29.

56.       The most compelling clinical reason to convert a hip arthrodesis to a total hip arthroplasty is that the latter

 

1-         improves hip range of motion.

2-         relieves pain associated with arthritis of the lumbar spine.

3-         relieves pain associated with arthritis of the knee.

4-         relieves pain in the contralateral hip.

5-         corrects a limb-length discrepancy.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Studies show that degenerative arthritis of the spine associated with a hip arthrodesis can be decreased with conversion to a total hip arthroplasty.  The pain associated with degenerative arthritis of the knee usually persists after arthrodesis take-down procedures and often requires total knee arthroplasty.  Pain in the contralateral hip is not resolved by converting the arthrodesis.  Improving range of motion of the hip and correcting a limb-length discrepancy are not good indications for take-down procedures.

 

REFERENCES: Strathy GM, Fitzgerald RH Jr: Total hip arthroplasty in the ankylosed hip: A ten-year follow-up.  J Bone Joint Surg Am 1988;70:963-966.  

Lubahn JD, Evarts CM, Feltner JB: Conversion of ankylosed hips to total hip arthroplasty.  Clin Orthop 1980;153:146-152.

57.       A 60-year-old woman reports a painful hip arthroplasty after undergoing surgery 18 months ago.  Radiographs show stable cementless implants without signs of ingrowth.  Laboratory studies show an erythrocyte sedimentation rate of 50 mm/h.  Management should now consist of

 

1-         a technetium Tc 99m scan.

2-         an indium scan.

3-         an ultrasound examination.

4-         aspiration.

5-         revision.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Significant elevation of the erythrocyte sedimentation rate in a patient with a painful hip arthroplasty mandates a complete work-up for infection prior to considering revision surgery.  Reproducibility and reliability of ultrasonography as a diagnostic test still needs clarification.  Aspiration is the easiest and most cost-effective test and should be performed prior to nuclear imaging.  The latter is most valuable if the results are negative, strongly predicting the absence of infection.

 

REFERENCES: Barrack RL, Harris WH: The value of aspiration of the hip joint before revision total hip arthroplasty.  J Bone Joint Surg Am 1993;75:66-76.

McAuley JP, Moreau G: Sepsis: Etiology, prophylaxis, and diagnosis, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip.  Philadelphia, PA, Lippincott-Raven, 1998, pp 1295-1306.

59.       Figure 24 shows the radiograph of an otherwise healthy 56-year-old patient who reports hip pain after undergoing a primary cementless hip replacement 4 months ago.  The next most appropriate step should consist of

 

1-         indomethacin for 3 months.

2-         C-reactive protein and a sed rate.

3-         MRI scan.

4-         bone scan.

5-         follow-up radiograph in 3 months.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Periosteal new bone formation is a warning sign of prosthetic infection.  Indomethacin may prevent heterotopic ossification if given early enough; however, it is irrelevant in this patient.  A C-reactive protein and a sed rate are useful screening studies that add to the predictive value of the radiographs and may be performed routinely if sepsis is suspected.  A bone scan obtained 4 months after surgery would show increased uptake in all cases.  If results of a sed rate and C-reactive protein are normal, then a biopsy should be considered to rule out a neoplasm.

 

REFERENCE: Fitzgerald RH Jr: Infected total hip arthroplasty: Diagnosis and treatment.  J Am Acad Orthop Surg 1995;3:249-262.

60.       Which of the following is considered a physiologic effect of anemia?

 

1-         Decreased heart rate

2-         Decreased coronary artery flow requirement

3-         Increased cardiac output

4-         Increased peripheral resistance

5-         Increased blood viscosity

 

PREFERRED RESPONSE: 3

 

DISCUSSION: The expected physiologic effects of anemia include an increased heart rate and increased cardiac output.  The coronary blood flow requirement increases.  There is a decrease in peripheral resistance and blood viscosity.

 

REFERENCE: Carson JL, Duff A, Poses RM, et al: Effect of anemia and cardiovascular disease on surgical mortality and morbidity.  Lancet 1996;348:1055-1060.

61.        A patient with severe rheumatoid arthritis reports progressive hip pain.  Serial hip radiographs will most likely show which of the following findings?

 

1-         Asymmetric joint space narrowing

2-         Sacroiliac joint ankylosis

3-         Progressive superior and lateral migration of the femoral head

4-         Periarticular osteopenia

5-         Hip synovitis

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Radiographic findings in patients with rheumatoid arthritis include symmetric joint space narrowing, periacetabular and femoral head erosions, and diffuse periarticular osteopenia.  In advanced stages, protrusio acetabuli is a common finding.  Ranawat and associates have shown a rate of superior femoral head migration of 4.5 mm per year and medial (axial) migration of 2.5 mm per year.  Asymmetric joint space narrowing is a classic radiographic finding of degenerative arthrosis.  Sacroiliac joint ankylosis commonly occurs in ankylosing spondylitis.  Hip synovitis is a pathologic diagnosis, not a radiographic finding.

 

REFERENCES: Lachiewicz PF: Rheumatoid arthritis of the hip.  J Am Acad Orthop Surg 1997;5:332-338.

Stuchin SA, Johanson NA, Lachiewicz PF, Mont MA: Surgical management of inflammatory arthritis of the adult hip and knee, in Zuckerman JS (ed): Instructional Course Lectures 48.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 93-109.

62.       A 70-year-old woman reports anterior knee pain after undergoing an uncomplicated total knee arthroplasty 6 months ago.  Examination reveals prepatellar tenderness, with no extensor lag.  The radiographs shown in Figures 25a through 25c reveal a well-fixed patellar component.  Management should consist of

 

1-         closed treatment with early motion.

2-         a cylindrical cast and restricted weight bearing.

3-         open reduction and internal fixation.

4-         patellar revision.

5-         patellectomy.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Patellar fractures that occur after a total knee arthroplasty are usually stress fractures.  Integrity of the extensor mechanism precludes the need for surgical repair or internal fixation, while stability and fixation of the patellar component determine whether revision is indicated.  A cylindrical cast and full weight bearing for 6 weeks is recommended for transverse fractures with an intact extensor mechanism and a stable component.  A similar fracture, if vertical, may be treated with earlier motion.

 

REFERENCES: Rorabeck CH, Angliss RD, Lewis PL: Fractures of the femur, tibia, and patella after total knee arthroplasty: Decision making and principles of management, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 449-458.

Hozack WJ, Goll SR, Lotke PA, Rothman RH, Booth RE Jr: The treatment of patellar fractures after total knee arthroplasty.  Clin Orthop 1988;236:123-127.

Rand JA: The patellofemoral joint in total knee arthroplasty.  J Bone Joint Surg Am 1994;76:612-620.

63.       Figure 26 shows the MRI scan of a 60-year-old man who has had groin pain for the past 2 months.  The patient reports pain with ambulation, and examination reveals an antalgic gait.  He denies any history of steroid or alcohol abuse.  Plain radiographs are normal.  Management should include

 

1-         core decompression.

2-         a vascularized fibula graft.

3-         intraosseous steroid injection.

4-         total hip replacement.

5-         protected weight bearing.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The patient has transient osteoporosis of the hip.  Transient osteoporosis is usually a self-limited condition that is most frequently seen in women in the third trimester of pregnancy and in men in the sixth decade of life.  Transient osteoporosis is best treated with protected weight bearing.

 

REFERENCE: Guerra JJ, Steinberg ME: Distinguishing transient osteoporosis from avascular necrosis of the hip.  J Bone Joint Surg Am 1995;77:616-624.

64.       Which of the following is considered the most common complication of the impaction grafting technique for femoral revision surgery?

 

1-         Loss of fixation

2-         Osteolysis

3-         Bone graft resorption

4-         Early stem subsidence

5-         Infection

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Impaction grafting technique for femoral revision surgery has become increasingly popular over the past decade.  This technique is designed to address cavitary deficiencies of the femur.  The femoral stem is inserted with cement fixation.  Its clinical efficacy has not been shown to be superior to extensively porous-coated stems.  Early subsidence of the stem has been reported in more than 50% of the patients.  However, loss of fixation has occurred infrequently (5%) in reported series conducted by experienced surgeons.  It has not been shown to have a higher infection rate.

 

REFERENCES: Gie GA, Linder L, Ling RS, Simon JP, Slooff TH, Timperley AJ: Impacted cancellous allografts and cement for revision total hip arthroplasty.  J Bone Joint Surg Br 1993;75:14-21.

Meding JB, Ritter MA, Keating ME, Faris PM: Impaction bone-grafting before insertion of a femoral stem with cement in revision total hip arthroplasty: A minimum two-year follow-up study.  J Bone Joint Surg Am 1998;79:1834-1841.

65.       What is the most likely late complication associated with cementless total knee replacement?

 

1-         Loss of motion

2-         Patellofemoral pain

3-         Osteolysis

4-         Heterotopic ossification

5-         Patellar clunk

 

PREFERRED RESPONSE: 3

 

DISCUSSION: In cementless total knee replacement, the risk of osteolysis is 30% if both components are placed without cement and screws are used for tibial fixation.  The risk is 10% when a cemented tibial component is used, and the risk is 0% when both components are cemented.  Loss of motion, patellofemoral pain, heterotopic bone formation, and patellar clunk are complications that can occur after cemented or cementless components are placed.

 

REFERENCE: Beaty JH (ed): Orthopaedic Knowledge Update 6.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 559-582.

66.       Figure 27 shows the radiograph of a 68-year-old woman with a history of rheumatoid arthritis who was injured in a fall.  History reveals that she has been asymptomatic since undergoing a left total knee arthroplasty 9 years ago.  Management should consist of

 

1-         skeletal traction. 

2-         immediate application of a cast brace.

3-         a retrograde supracondylar nail.

4-         revision total knee replacement. 

5-         resection arthrodesis.    

 

PREFERRED RESPONSE: 3

 

DISCUSSION: A supracondylar fracture of the femur that occurs after total knee replacement can be treated effectively by a number of methods.  For this fracture, the use of a retrograde supracondylar nail has been found to be effective in several series.  The treatment of these complex injuries needs to be individualized based on the stability of the implant, the quality of the bone, and the extent of comminution of the fracture.  Revision with the use of an unstemmed implant will not result in effective stabilization of the knee or the fracture.

 

REFERENCE: Ayers DC: Supracondylar fracture of the distal femur proximal to a total knee replacement, in Springfield DS (ed): Instructional Course Lectures 46.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 197-203.

67.       Design factors that enhance the long-term survival of proximally coated cementless hip implants include both initial stability and

 

1-         circumferential porous coating.

2-         a titanium porous coating.

3-         a fluted stem.

4-         a distal centralizer.

5-         modular fixation pads.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Proximally coated femoral components were conceived in response to the proximal stress shielding seen with extensively coated total hip stems, but initial patient studies showed problems with osteolysis, thigh pain, and stability.  However, Mont and Hungerford now report that second-generation devices that have been in use more than 5 years clinically have shown very low aseptic loosening rates (1% to 3%), and patients report less thigh pain (less than 5% in most studies).  These results can be attributed to improved geometry, instruments, and technique, which ensure initial implant stability.  The authors suggest that proximal coating must be circumferential to seal the diaphysis from wear debris, and they note that the concept of proximal coating for cementless femoral stems seems viable as long as the twin requirements of circumferential coating and rigid initial stability are realized.

 

REFERENCES: Mont MA, Hungerford DS: Proximally coated ingrowth prostheses: A review.  Clin Orthop 1997;344:139-149.

Engh CA, Hooten JP Jr, Zettl-Schaffer KF, Ghaffarpour M, McGovern TF, Bobyn JD: Evaluation of bone ingrowth in proximally and extensively porous-coated anatomic medullary locking prostheses retrieved at autopsy. J Bone Joint Surg Am 1995;77:903-910.

Urban RM, Jacobs JJ, Sumner DR, Peters CL, Voss FR, Galante JO: The bone-implant interface of femoral stems with non-circumferential porous coating.  J Bone Joint Surg Am 1996;78:1068-1081.

68.       A 45-year-old man with a painful varus knee is being considered for an upper tibial osteotomy.  Which of the following factors is considered the most compelling argument against this procedure?

 

1-         Flexion contracture of 5°

2-         Subchondral cyst in the medial tibial condyle

3-         Lateral meniscal degeneration seen in an MRI scan

4-         Rheumatoid arthropathy

5-         Previous medial meniscectomy

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Proximal tibial osteotomy is appropriate for the younger and/or athletic patient who has mild to moderate medial compartment osteoarthritis.  Relative contraindications include limited range of motion (eg, flexion contracture of 15°), anatomic varus of greater than 10°, advanced patellofemoral arthritis, and tibial subluxation.  Inflammatory arthritides involve all the compartments and are a contraindication to osteotomies around the knee.

 

REFERENCE: Kelly MA: Nonprosthetic management of the arthritic knee, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 245-249.

69.       An obese patient undergoing total knee arthroplasty is at increased risk for which of the following complications?

 

1-         Wound complication

2-         Infection

3-         Lower knee score

4-         Aseptic loosening

5-         Patellar subluxation

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The rate of wound complications is significantly increased after total knee arthroplasty in obese patients.  Knee scores and the rate of aseptic loosening or patellar subluxation do not appear to be significantly altered.

 

REFERENCES: Winiarsky R, Barth P, Lotke P: Total knee arthroplasty in morbidly obese patients.  J Bone Joint Surg Am 1998;80:1770-1774.

Stern SH, Insall JN: Total knee arthroplasty in obese patients.  J Bone Joint Surg Am 1990;72:1400-1404.

Griffin FM, Scuderi GR, Insall JN, Colizza W: Total knee arthroplasty in patients who were obese with 10 years follow-up.  Clin Orthop 1998;356:28-33.

70.       Figures 28a and 28b show the radiographs of a 79-year-old man who has constant knee pain.  Prior to performing elective knee replacement surgery, management should include

 

1-         reduction of the serum alkaline phosphatase level by 50%.

2-         preoperative radiation therapy of 600 cGy to the surgical site.

3-         aspiration of the knee joint with cell count.

4-         insertion of a vena caval filter.

5-         administration of 25 mg of indomethacin three times a day.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The radiographs show established Paget’s disease.  Bony expansion is evident, with thickened trabeculae consistent with the disordered bone remodeling process.  A reduction of the serum alkaline phosphatase level to 50% of the pretreatment level may reduce pain from Paget’s disease, and it is recommended prior to consideration of joint replacement.  In elective cases, treatment of Paget’s disease should begin at least 6 weeks prior to surgery.  The other modalities are not related to the treatment of Paget’s disease.

 

REFERENCES: Kaplan FS, Singer FS: Paget’s disease of bone: Pathophysiology, diagnosis, and management.  J Am Acad Orthop Surg 1995;3:336-344.

Simon SR (ed): Orthopaedic Basic Science.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 129-184.

Siris ES: Paget’s disease of bone, in Favus MJ (ed): Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism.  New York, NY, Raven Press, 1993, pp 375-384.

 

71.        What is the most common complication of using structural bulk allograft to reconstruct segmental defects of the acetabulum?

 

1-         Infection

2-         Early loss of cup fixation

3-         Graft resorption and collapse

4-         Limb-length discrepancy

5-         Dislocation

 

PREFERRED RESPONSE: 3

 

DISCUSSION: Both autograft and allograft have been used for complex acetabular reconstructions.  They have been shown to be successful in the short term.  However, graft resorption with collapse and subsequent cup loosening have occurred at high rates for both types of grafts, especially if reinforcement rings or cages are not used.

 

REFERENCES: Jasty M, Harris WH: Salvage total hip reconstruction in patients with major acetabular bone deficiency using structural femoral head allografts.  J Bone Joint Surg Br  1990;72:63-67.

Paprosky WG, Magnus RE: Principles of bone grafting in revision total hip arthroplasty: Acetabular technique.  Clin Orthop 1994;298:147-155.

Kwong LM, Jasty M, Harris WH: High failure rate of bulk femoral head allografts in total hip acetabular reconstructions at 10 years. J Arthroplasty 1993;8:341-346.

72.       Radiographs of a 12-year-old boy who has knee pain show a 2-cm osteochondral lesion of the lateral aspect of the medial femoral condyle.  The fragments are not detached from the femur.  Initial management should consist of

 

1-         casting in flexion.

2-         observation.

3-         arthroscopic drilling and pinning of the lesion.

4-         removal and reattachment of the osteochondral lesion.

5-         allograft transplantation for the lesion.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: For a pediatric patient without mechanical symptoms, initial management of an osteochondral defect lesion that is not detached should consist of casting in flexion.  Failure to respond to several weeks or months of nonsurgical management may warrant surgical treatment.

 

REFERENCE: Beaty JH (ed): Orthopaedic Knowledge Update 6.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 505-520.

73.        Which of the following drawbacks is associated with the Ganz periacetabular osteotomy?

 

1-         The tendency to anterior displacement of the hip joint

2-         The need for two incisions

3-         Limited potential for acetabular reorientation

4-         Posterior column disruption

5-         Devascularization of the acetabulum 

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Although technically challenging, the Ganz periacetabular osteotomy offers advantages over other rotational pelvic osteotomies.  Posterior column integrity is maintained, as is the acetabular vascular supply.  Free mobility of the fragment makes large corrections in the center edge angle possible.  Because of the asymmetric cuts and the need to restore anterior coverage, there is a tendency to anterior displacement of the joint while flexing the acetabulum.  The procedure is commonly performed through a Smith-Petersen incision.

 

REFERENCES: Trousdale RT, Ganz R:  Periacetabular osteotomy, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip.  Philadelphia, Pa, Lippincott-Raven, 1998, pp 789-802.

Ganz R, Klaue K, Vinh TS, Mast JW: A new periacetabular osteotomy for the treatment of hip dysplasias: Technique and preliminary results.  Clin Orthop 1988;232:26-36.

MacDonald SJ, Hersche O, Ganz R: Periacetabular osteotomy in the treatment of neurogenic acetabular dysplasia.  J Bone Joint Surg Br 1999;81:975-978.

74.       Which of the following lesions is best suited for autologous chondrocyte implantation?

 

1-         Patellofemoral arthritis

2-         Lateral femoral condylar arthritis

3-         Medial femoral condylar arthritis

4-         Medial femoral chondral defect

5-         Medial femoral and tibial articular chondral matching defects

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Articular chondrocyte implantation is best performed for focal chondral defects of one area of the joint.  It is not indicated for osteoarthritis.

 

REFERENCES: Mandelbaum BR, Brown JE, Fu F, et al: Articular cartilage lesions of the knee.  Am J Sports Med 1998;26:853-861.

Minas T, Nehrer S: Current concepts in the treatment of articular cartilage defects.  Orthopedics 1997;20:525-538.

Brittberg M, Lindahl A, Nilsson A, Ohlsson C, Isaksson O, Peterson L: Treatment of deep cartilage defects in the knee with autologous chondrocyte transplantation.  N Engl J Med 1994;331:889-895.

75.       The additional risk of complications in organ transplant patients receiving a total joint arthroplasty is attributed to

 

1-         infection.

2-         dislocation.

3-         deep venous thrombosis.

4-         periprosthetic fracture.

5-         myocardial infection.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Tannenbaum and associates found that patients who had a joint replacement after an organ transplantation had a rate of infection of 19% (five of 27 joint replacements in 16 patients).  They retrospectively reviewed the results of 35 joint (hip or knee) replacements in 19 patients who had an organ transplant.  The patients received a standard immunosuppressive induction regimen at the time of the transplantation and were maintained on a combination of prednisone, azathioprine, and cyclosporin A.  All patients received antibiotics perioperatively, but antibiotic-impregnated bone cement was not used for any procedure.  Six joint replacements in three patients (median patient age of 48.2 years at the time of the arthroplasty) were performed before a renal transplantation.  Twenty-four joint replacements in 14 patients (average patient age of 40.9 years at the time of the arthroplasty) were performed after an organ transplantation.  Two patients, with an average age of 53.8 years at the time of the arthroplasty, each had a joint replacement both before and after a liver transplantation (a total of five joint replacements).  The average duration of follow-up after the first joint replacement was 8.8 years (range, 1 to 23 years).  An infection developed around the implant in five patients who had undergone the joint replacement after a transplantation.  The average interval from implantation of the prosthesis until detection of the infection was 3.4 years (range, 1 to 6 years).  Of two patients who underwent a liver transplant, one had Pseudomonas aeruginosa infection and the other Escherichia coli infection.  Of three patients who underwent a renal transplantation, one was infected with Staphylococcus epidermidis, one with Enterococcus, and one with Serratia marcescens. 

 

REFERENCE: Tannenbaum DA, Matthews LS, Grady-Benson JC: Infection around joint replacements in patients who have a renal or liver transplantation.  J Bone Joint Surg Am 1997;79:36-43.

76.       Figure 29 shows the radiograph of a 55-year-old patient who has recurrent total hip dislocation.  Dislocation is most likely to occur in this patient when the hip is in which of the following positions?

 

1-         Neutral rotation

2-         External rotation

3-         Internal rotation

4-         Hyperflexion

5-         Midstance phase of gait

 

PREFERRED RESPONSE: 2

 

DISCUSSION: The patient has an acetabular component that is placed in excessive anteversion; this is confirmed by the shoot-through radiograph.  The most common reasons for dislocation of a total hip replacement include inappropriate positioning of the components, inadequate abductor tension, or impingement.  Implants placed without adequate total anteversion tend to dislocate posteriorly, and implants with excessive anteversion tend to dislocate anteriorly.  Superior dislocations can occur if the acetabular component is placed in a severely vertical position with inadequate lateral coverage. 

 

REFERENCE: Paterno SA, Lachiewicz PF, Kelley SS: The influence of patient-related factors and the position of the acetabular component on the rate of dislocation after total hip replacement.  J Bone Joint Surg Am 1997;79:1202-1210.

77.        Back pain and ipsilateral knee pain are common long-term sequelae of hip arthrodesis.  To limit these problems, what position should be avoided during fusion of the hip?

 

1-         Flexion

2-         Abduction

3-         Adduction

4-         External rotation

5-         Internal rotation

 

PREFERRED RESPONSE: 2

 

DISCUSSION: The recommended position for a hip fusion is flexion of 20° to 30°, slight adduction (5°) or neutral, and 10° of external rotation.  In long-term follow-up, patients who underwent fusion in abduction had more ipsilateral knee and low back pain than patients who were positioned in adduction.  Internal rotation should be avoided to prevent interference with the opposite foot during gait.  External rotation facilitates the application of shoe wear.

 

REFERENCES: Callaghan JJ, Brand RA, Pederson DR: Hip arthrodesis: A long-term follow-up.  J Bone Joint Surg Am 1985;67:1328-1335.

Callaghan JJ, McBeath AA: Arthrodesis, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip.  Philadelphia, PA, Lippincott-Raven, 1998, pp 749-759.

 

78.        Which of the following methods most reliably detects mechanical loosening of the hip?

 

1-         Serial planar radiographs 

2-         Joint aspiration

3-         Aspiration and arthrogram

4-         Technetium Tc 99m scan

5-         CT scan

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Mechanical loosening of the hip is best revealed by serial radiographs of the prosthetic joint.  None of the other methods of evaluation is considered reliable in diagnosing mechanical loosening.

 

REFERENCES: Beaty JH (ed): Orthopaedic Knowledge Update 6.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 455-492.

Miniaci A, Bailey WH, Bourne RB, McLaren AC, Rorabeck CH: Analysis of radionuclide arthrograms, radiographic arthrograms, and sequential plain radiographs in the assessment of painful hip arthroplasty.  J Arthroplasty 1990;5:143-149.

79.       A 55-year-old man underwent cementless total hip arthroplasty for advanced painful osteoarthritis of the hip 2 years ago.  The follow-up radiograph shown in Figure 30 shows

 

1-         spot welds and calcar atrophy.

2-         subsidence.

3-         distal cortical hypertrophy.

4-         distal pedestal formation.

5-         complete lucent line around the stem.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The radiograph shows a well-osseointegrated tapered stem with a metaphyseal porous coating, spot welds in the porous region, and calcar rounding.  Trochanteric stress shielding and distal cortical hypertrophy are also signs of ingrown stems but are seen more frequently in association with extensively porous-coated stems exhibiting diaphyseal ingrowth.  There is no evidence of lucent lines or a pedestal, signs that suggest instability.  Femoral stem subsidence can be determined only by a review of sequential radiographs.

 

REFERENCES: Engh CA, Massin P, Suthers KE: Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components.  Clin Orthop 1990;257:107-128.

Vresilovic E, Hozack WJ, Rothman RH: Radiographic assessment of cementless femoral components: Correlation with intraoperative mechanical stability.  J Arthroplasty 1994;9:137-141.

80.       A 52-year-old woman has bicompartmental osteoarthritis following patellectomy.  Treatment should consist of  

 

1-         high tibial osteotomy.

2-         arthroscopic debridement.

3-         patella arthroplasty.

4-         total knee arthroplasty.

5-         knee arthrodesis.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The patient has extensive degenerative changes in both the medial and lateral compartments within the knee; therefore, arthroscopic debridement or an osteotomy will not be helpful.  A patellar arthroplasty will not address the medial and lateral compartments.  Because the extensor mechanism provides a significant amount of anteroposterior stability, a posterior cruciate-substituting total knee arthroplasty is the treatment of choice for this patient.  

 

REFERENCES: Martin SD, Haas SB, Insall JN: Primary total knee arthroplasty after patellectomy.  J Bone Joint Surg Am 1995;77:1323-1330.

Pagnano MW, Cushner FD, Scott WN: Role of the posterior cruciate ligament in total knee arthroplasty.  J Am Acad Orthop Surg 1998;6:176-187.

81.        In hybrid arthroplasty, the use of a polymethylmethacrylate (PMMA) precoated femoral component has been shown to result in

 

1-         increased survivorship compared with nonprecoated stems.

2-         increased bonding of the stem to the cement mantle.

3-         a reduced rate of wear compared with nonprecoated stems.

4-         a reduced rate of revision compared with nonprecoated stems.

5-         a reduced rate of postoperative infection.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: Precoating of the femoral stem with PMMA results in increased bonding of the stem to the cement mantle.  However, this has not been shown to result in superior survivorship compared with nonprecoated stems of similar design.  In one series, the rate of revision of precoated stems was greater than that of nonprecoated cohorts.  The wear and infection rates have not been shown to differ between precoated and nonprecoated stems.  

 

REFERENCES: Sporer SM, Callaghan JJ, Olejniczak JP, Goetz DD, Johnston RC: The effects of surface roughness and polymethylmethacrylate precoating on the radiographic and clinical results of the Iowa hip prosthesis: A study of patients less than fifty years old.  J Bone Joint Surg Am 1999;81:481-492.

Schulte KR, Callaghan JJ, Kelley SS, Johnston RC: The outcome of Charnley total hip arthroplasty with cement after a minimum twenty-year follow-up: The results of one surgeon.  J Bone Joint Surg Am 1993;75:961-975.

82.       A 72-year-old woman has had progressively increasing pain in the right knee for the past 6 months.  She denies any trauma and has no pain in any other joints, but she notes occasional swelling in the knee and a catching sensation.  Figures 31a and 31b show the plain radiographs and Figure 31c shows the MRI scan.  Treatment should consist of

 

1-         arthroscopy and subtotal meniscectomy.

2-         arthroscopy and shaving chondroplasty.

3-         osteochondral bone graft.

4-         high tibial valgus osteotomy.

5-         total knee replacement.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The plain radiograph shows a defect in the lateral femoral condyle and narrowing of the lateral joint space.  The MRI scan shows a lesion consistent with osteonecrosis of the lateral femoral condyle.  The treatment alternatives for this condition are an osteotomy or a total knee replacement, but a total knee replacement is the treatment of choice for a 72-year-old patient.  Arthroscopy or an osteochondral bone graft will not address her symptoms.  A valgus osteotomy will exacerbate the problem by overloading the lateral joint, which is already diseased.

 

REFERENCES: Lotke PA, Ecker ML: Osteonecrosis of the knee.  J Bone Joint Surg Am 1988;70:470-473.

Ecker ML, Lotke PA: Osteonecrosis of the medial part of the tibial plateau.  J Bone Joint Surg Am 1995;77:596-601.

 

83.        Which of the following is considered the most appropriate indication for conversion of a hip fusion to total hip arthroplasty?

 

1-         Moderate arthritis of the ipsilateral knee

2-         Progressive arthritis of the contralateral hip

3-         Severe disabling back pain

4-         Limb-length discrepancy

5-         Increased hip motion

 

PREFERRED RESPONSE: 3

 

DISCUSSION: Hip fusion provides successful long-term results (20 to 30 years).  The usual mode of failure is symptomatic arthrosis of the lower back, contralateral hip, or the ipsilateral knee.  Disabling low back pain is the best indication for conversion and responds well to the procedure.  Degenerative changes in the other joints do not respond as well and frequently require replacement arthroplasty.  Restoration of limb length is not predictable after conversion to hip replacement.  

 

REFERENCES: Santore RF: Hip reconstruction: Nonarthroplasty, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 109-115.

Callaghan JJ, Brand RA, Pedersen DR: Hip arthrodesis: A long-term follow-up.  J Bone Joint Surg Am 1985;67:1328-1335.

84.       Which of the following methods is effective in correcting recurrent dislocation following total hip arthroplasty?

 

1-         Lateralization of the greater trochanter without advancement

2-         Use of a shorter neck length

3-         Use of a constrained acetabular component

4-         Use of a small diameter head

5-         High cup abduction angle

 

PREFERRED RESPONSE: 3

 

DISCUSSION: Recurrent dislocation following total hip arthroplasty is a difficult problem to correct.  Studies conducted by the Mayo Clinic show a failure rate of close to 40% with surgical treatment.  A variety of methods have been successful, but no specific approach has been reported to be the most predictably successful.  To select and institute the proper treatment option, the cause of the dislocation must be identified.  Surgical options fall into several broad categories that include increasing soft-tissue tension (trochanteric advancement or longer neck lengths) or more stable articulation (larger diameter head component, bipolar prosthesis, or a constrained component).  In a series of total hip arthroplasties done with a constrained cup, the loosening rates of the cup and the stem were reported to be 6% each, comparable to a reported series of complex revision total hip arthroplasties at a similar follow-up interval.

 

REFERENCES: Woo RY, Morrey BF: Dislocations after total hip arthroplasty.  J Bone Joint Surg Am 1982;64:1295-1306.

Goetz DD, Capello WN, Callaghan JJ, Brown TD, Johnston RC: Salvage of a recurrently dislocating total hip prosthesis with use of a constrained acetabular component:  A retrospective analysis of fifty-six cases.  J Bone Joint Surg Am 1998;80:502-509.  

85.       A 58-year-old woman who underwent a successful total hip replacement for degenerative arthritis 8 years ago reports groin pain for the past 6 months.  A radiograph of the hip is shown in Figure 32.  At revision, severe deficiency of the posterior column is noted.  What reconstructive option would be most appropriate for the acetabulum?

 

1-         Cementless cup without graft

2-         Cemented cup without graft

3-         Cemented cup with structural bone graft

4-         Bone graft, reconstruction cage, and cemented cup

5-         Bilobed cementless acetabular component

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The radiograph shows medial migration of the cementless acetabular component, strongly suggesting acetabular discontinuity with a combined segmental and cavitary medial deficiency.  The treatment of choice is a morcellized or structural graft, supported with a reconstructive cage bridging the pelvic discontinuity, and a cemented cup.

 

REFERENCES: Whiteside LA: Selection of acetabular component, in Steinberg ME, Garino JP (eds): Revision Total Hip Arthroplasty.  Philadelphia, PA, Lippincott Williams and Wilkins, 1999, pp 209-220.

Berry DJ, Muller ME: Revision arthroplasty using an anti-protrusio cage for massive acetabular bone deficiency.  J Bone Joint Surg Br 1992;74:711-715.

86.       A patient with a previously pain-free knee replacement now reports a sudden inability to ambulate.  Radiographs of the knee are shown in Figures 33a and 33b.  Management should consist of

 

1-         bracing and physical therapy.

2-         insertion of a thicker polyethylene insert.

3-         revision with a cementless modular prosthesis.

4-         revision with a cemented semiconstrained prosthesis.

5-         reconstruction of the extensor mechanism.

 

PREFERRED RESPONSE: 5

 

DISCUSSION: The radiographs show a patellar tendon rupture following a total knee replacement.  This infrequent, but serious, complication is reported to occur in 0.17% to 1.4% of patients after total knee arthroplasty.  Although the radiographs show concerning features such as incomplete tibial and femoral periprosthetic lucencies, it is most important for the surgeon to recognize extensor mechanism disruption.

 

REFERENCES: Insall J, Salvati E: Patella position in the normal knee joint.  Radiology 1971;101:101-104.

Lynch AF, Rorabeck CH, Bourne RB: Extensor mechanism complications following total knee arthroplasty.  J Arthroplasty 1987;2:135-140.

Rand JA, Morrey BF, Bryan RS: Patellar tendon rupture after total knee arthroplasty.  Clin Orthop 1989;244:233-238.

87.        Which of the following factors will adversely affect bone ingrowth in a revision porous-coated stem?

 

1-         Pore size of 400 mm

2-         Interface instability of 25 mm of micromotion

3-         Use of a nonmodular implant

4-         Noncircumferential metaphyseal patch coating

5-         Failure of ingrowth in the previous stem

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The optimal conditions for bony ingrowth include a pore size of 100 to 400 mm, interface micromotion of 50 mm or less, intimate contact between the bone and the implant, circumferential porous coating of the implant, and use of a biocompatible material.  Stem designs with patch coatings have a poor record of bony ingrowth, especially in the revision setting.  Failure of ingrowth in the previous stem would be the result of its own mechanical milieu and would not necessarily predict results for the new stem.

 

REFERENCES: Berry DJ, Harmsen WS, Ilstrup D, Lewallen DG, Cabanela ME: Survivorship of uncemented proximally porous-coated femoral components.  Clin Orthop 1995;319:168-177.

Cook SD, Thomas KA, Haddad RJ Jr: Histologic analysis of retrieved human porous-coated total joint components.  Clin Orthop 1988;234:90-101.

Spector M: Historical review of porous-coated implants.  J Arthroplasty 1987;2:163-177.

88.        In the preoperative planning of revision acetabular reconstruction, the surgeon should identify significant posterior column deficiency by noting which of the following radiographic features?

 

1-         Excessive vertical position of the acetabular component

2-         Medial displacement of the hip center to the ilioischial line

3-         Visible wear of the polyethylene articulation

4-         Osteolysis in the ischium

5-         Superior migration of 1 cm

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Proximal and medial migration of the femoral head usually indicates deficiencies of the dome or anterior column.  Wear of the polyethylene may result in osteolysis and impingement, which are not indicative of any major bone deficiency.  A significant osteolytic lesion in the ischium may represent a major posterior column deficiency that can create a technical challenge during the reconstruction.

 

REFERENCES: Paprosky WG, Magnus RE: Principles of bone grafting in revision total hip arthroplasty: Acetabular technique.  Clin Orthop 1994;298:147-155.

Campbell DG, Masri BA, Garbuz DS, Duncan CP: Acetabular bone loss during revision total hip replacement: Preoperative investigation and planning, in Zuckerman J (ed): Instructional Course Lectures 48.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 43-56.

89.       An 82-year-old woman reports right buttock pain after a car trip.  Laboratory studies show an erythrocyte sedimentation rate of 30 mm/h and WBC of 4,600/mm³.  Figure 34a shows a plain AP radiograph of the pelvis, and Figure 34b shows a delayed technetium Tc 99m bone scan.  Management should consist of

 

1-         bed rest and pain medication.

2-         revision of the right acetabular component.

3-         revision of the right femoral component.

4-         revision of the right total hip replacement.

5-         resection arthroplasty.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The radiograph shows bilateral cemented total hip arthroplasties.  The acetabular components are loose bilaterally, but there has been no acute change.  Therefore, it is unlikely that the acetabular loosening is contributing to the patient’s pain.  The bone scan is consistent with a sacral insufficiency fracture.  This is best treated with bed rest and pain medication.  Activity can be increased as the pain allows.  Revision will not address the pain.

 

REFERENCES: Newhouse KE, el-Khoury GY, Buckwalter JA: Occult sacral fractures in osteopenic patients.  J Bone Joint Surg Am 1992;74:1472-1477.

Marmor L: Stress fracture of the pubic ramus simulating a loose total hip replacement.  Clin Orthop 1976;121:103-104.

90.       Figures 35a and 35b show the radiographs of a patient who underwent debridement of a chronically infected, fully constrained knee prosthesis and now reports pain and instability despite bracing.  History reveals that the patient has had no drainage since undergoing the last debridement 6 months ago.  A C-reactive protein level and aspiration are negative for infection.  Treatment should now consist of 

 

1-         knee arthrodesis.

2-         insertion of a semiconstrained prosthesis.

3-         insertion of an antibiotic-impregnated polymethylmethacrylate (PMMA) spacer.

4-         reconstruction of the extensor mechanism.

5-         amputation.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The radiographs show a significant loss of the proximal anterior tibial cortex, consistent with an extensively damaged or deficient extensor mechanism.  Such a deficit precludes insertion of another knee arthroplasty.  Arthrodesis is the treatment of choice for this patient and is indicated for loss of the extensor mechanism and knee instability.  A recent report on arthrodesis following removal of an infected prosthesis showed a union rate of 91% using a short intramedullary nail.  Insertion of an antibiotic-impregnated PMMA spacer is not indicated because the rationale for using a spacer is to maintain a space for reinsertion of another prosthesis.  Reconstruction of the extensor mechanism would not address the loss of the joint.  Amputation is the final treatment option if the arthrodesis fails.  

 

REFERENCES: Rand JA: Alternatives to reimplantation for salvage of the total knee arthroplasty complicated by infection.  J Bone Joint Surg Am 1993;75:282-289.

Lai KA, Shen WJ, Yang CY: Arthrodesis with a short Huckstep nail as a salvage procedure for failed total knee arthroplasty.  J Bone Joint Surg Am 1998;80:380-388.

Damron TA, McBeath AA: Arthrodesis following failed total knee arthroplasty: Comprehensive review and meta-analysis of recent literature.  Orthopedics 1995;18:361-368.

91.        Which of the following is considered an advantage of metal femoral heads compared with ceramic heads?

 

1-         Superior lubrication properties

2-         Smoother surface

3-         Less susceptible to third body wear

4-         More inert material

5-         Greater neck-length options

 

PREFERRED RESPONSE: 5

 

DISCUSSION: Ceramic-on-ceramic bearing surfaces have superior tribological properties and show lower linear wear than metal-on-metal implants.  However, because of their lower strength and vulnerability to fracture, design considerations constrain the neck-length options available to ensure optimal taper fit.

 

REFERENCE: Cook SD:  Materials consideration in total joint replacement, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds):  Orthopaedic Knowledge Update: Hip and Knee Reconstruction.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 27-33.

92.       What is the most common result if the acetabulum is rotated too far anteriorly during a periacetabular osteotomy?

 

1-         Posterior dislocation

2-         Limited hip flexion

3-         Heterotopic ossification

4-         Femoral nerve injury

5-         Fracture of the posterior column

 

PREFERRED RESPONSE: 2

 

DISCUSSION: In patients with hip dysplasia who undergo a periacetabular osteotomy, the authors note that the freed acetabular segment can be overcorrected for the deformity.  If it is placed too anteriorly, then hip flexion is limited.  Posterior dislocation is a rare complication.  The other complications should not occur as a result of this procedure.

 

REFERENCES: Hussell JG, Rodriguez JA, Ganz R: Technical complications of the Bernese periacetabular osteotomy.  Clin Orthop 1999;363:81-92.

Myers SR, Eijer H, Ganz R: Anterior femoroacetabular impingement after periacetabular osteotomy.  Clin Orthop 1999;363:93-99.

93.       Which of the following radiographic views best assesses anterior coverage of the dysplastic hip?

 

1-         AP of the hip

2-         Obturator oblique

3-         Lauenstein lateral 

4-         Faux profil

5-         Pelvic inlet

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Anterior coverage of the hip may be best estimated by the anterior center edge angle of Lequesne and de Seze (analogous to Wiberg’s angle), which is measured on the well-defined faux profil view.  Evaluation with CT scans also has been described.

 

REFERENCES: Klaue K, Wallin A, Ganz R: CT evaluation of coverage and congruency of the hip prior to osteotomy.  Clin Orthop 1988;232:15-25.

Ganz R, Klaue K, Vinh TS, Mast JW: A new periacetabular osteotomy for the treatment of hip dysplasias: Technique and preliminary results.  Clin Orthop 1988;232:26-36.

 

 

94.       Figure 36a shows the current radiograph of a 65-year-old woman who slipped and fell.  History reveals that prior to the fall she was actively functioning without pain.  Figure 36b shows a radiograph obtained 1 year ago.  Based on the fracture pattern, the failure is most likely related to

 

1-         repetitive loading and fatigue failure.

2-         incomplete bone ingrowth with focal osteolysis.

3-         rotational bone axial loading.

4-         a fixed component with a modulus mismatch.

5-         use of titanium instead of cobalt-chromium.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: The radiograph shows a fracture distal to the prosthesis in a stable, apparently well-fixed prosthetic stem.  The well-fixed prosthesis-bone composite is stiff, creating a modulus mismatch between the proximal and distal femur.  Therefore, the risk of fracture, particularly in osteoporotic bone, is increased at this level.  Revision of the stem to a longer construct is unnecessary, and standard plate and screw fixation has been shown to yield union rates of greater than 90%.  Nonsurgical treatment of fractures distal to the tip of the prosthesis results in high nonunion rates, reported to be from 25% to 42%.  

 

REFERENCES: Johansson JE, McBroom R, Barrington TW, Hunter GA: Fracture of the ipsilateral femur in patients with total hip replacement.  J Bone Joint Surg Am 1981;63:1435-1442.

Bethea JS III, DeAndrade JR, Fleming LL, Lindenbaum SD, Welch RB: Proximal femoral fractures following total hip arthroplasty.  Clin Orthop 1982;170:95-106.

Garbuz DS, Masri BA, Duncan CP: Periprosthetic fractures of the femur: Principles of prevention and management, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 237-242.

 

 

95.       A 70-year-old man has worn through his metal-backed patellar component and sustained damage to the femoral component.  Following removal of the components and debridement of the metal-stained synovium, the surgeon finds that the thickness of the remaining patella is 10 mm.  Treatment should now include

 

1-         insertion of a thicker cement mantle and a thicker patellar insert to achieve a total patellar thickness of 24 mm.

2-         a lateral release after inserting a standard patella.

3-         a distal femoral augmentation to maximize the moment-arm on a standard patellar insert.

4-         leaving the patella alone and performing a lateral release, if necessary, for proper patellar tracking.

5-         an oversized femoral component to improve the moment-arm on a standard patellar insert.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Revision of a failed patellar component can be difficult because of bone loss and damage to the extensor mechanism.  Several authors have advised against reinsertion of a patellar component if the residual patellar thickness is 10 mm or less.  Leaving an unresurfaced bony remnant in place at the time of revision or reimplantation surgery has been shown to be a reasonable option; however, the results are of a lower quality when compared with revision surgery where the patellar component can be retained or revised.  The other treatment options have not been shown to be effective approaches to this problem.

 

REFERENCES: Rand JA: The patellofemoral joint in total knee arthroplasty.  J Bone Joint Surg Am 1994;76:612-620.

Pagnano MW, Scuderi GR, Insall JN: Patellar component resection in revision and reimplantation total knee arthroplasty.  Clin Orthop 1998;356:134-138.

Barrack RL, Matzkin E, Ingraham R, Engh G, Rorabeck C: Revision knee arthroplasty with patella replacement versus bony shell.  Clin Orthop 1998;356:139-143.

 

 

96.       A 65-year-old man has a painful and often audible crepitus after undergoing a total knee arthroplasty 8 months ago.  His symptoms are reproduced with active extension of about 30°.  Examination reveals no effusion or localized tenderness, a stable knee, and a range of motion of 5° to 120°.  Radiographs are shown in Figures 37a and 37b.  Management should consist of

 

1-         revision of all components to ensure patellar tracking.

2-         athroscopic debridement.

3-         arthrotomy and keloid excision.

4-         intra-articular corticosteroid injections.

5-         patellar component revision.

 

PREFERRED RESPONSE: 2

 

DISCUSSION: This is a typical presentation of the patellar clunk syndrome.  The syndrome usually follows implantation of a posterior stabilized prosthesis.  It is thought to be the result of femoral component design and altered extensor mechanics.  The condition usually resolves with arthroscopic debridement of the suprapatellar fibrous nodule.  Arthrotomy or revision is seldom warranted.

 

REFERENCES: Beight JL, Yao B, Hozack WJ, Hearn SL, Booth RE Jr: The patellar “clunk” syndrome after posterior stabilized total knee arthroplasty.  Clin Orthop 1994;299:139-142.

Lintner DM, Bocell JR, Tullos HS: Arthroscopic treatment of intra-articular fibrous bands after total knee arthroplasty: A follow-up note.  Clin Orthop 1994;309:230-233.

97.       What clinical parameter will most likely decrease the need for blood transfusion after total joint arthroplasty?

 

1-         Bilateral total joint replacement

2-         Rheumatoid arthritis

3-         Preoperative donation of autologous blood

4-         Age greater than 65 years

5-         Hemoglobin level of greater than 15 g/dL

 

PREFERRED RESPONSE: 5

 

DISCUSSION: Bilateral joint replacement, chronic disease, and preoperative autologous donation all increase the risk of needing blood.  Young patients and a high hemoglobin level (greater than 15 g/dL) are considered clinical parameters that decrease the risk for requiring allogenic blood. 

 

REFERENCES: Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB: An analysis of blood management in patients having a total hip or knee arthroplasty.  J Bone Joint Surg Am 1999;81:2-10.

Knight JL, Sherer D, Guo J: Blood transfusion strategies for total knee arthroplasty:  Minimizing autologous blood wastage, risk of homologous blood transfusion, and transfusion cost.  J Arthroplasty 1998;13:70-76.

98.       Figure 38 shows the radiograph of a 40-year-old woman who reports severe groin pain and lack of motion of the right hip.  History reveals that the patient underwent a femoral osteotomy for hip dysplasia approximately 30 years ago.  Treatment should include

 

1-         femoral osteotomy.

2-         periacetabular osteotomy.

3-         arthroscopic debridement.

4-         total hip arthroplasty.

5-         hip arthrodesis.

 

PREFERRED RESPONSE: 4

 

DISCUSSION: Although the patient is young, a total hip arthroplasty will provide pain relief and improve her range of motion.  The arthritis is too advanced for the patient to benefit from an osteotomy.  In addition, periacetabular osteotomy and hip arthrodesis do not improve range of motion of the hip.  It has not been established that patients with severe osteoarthritis will benefit from arthroscopic debridement of the hip.

 

REFERENCE: Trousdale RT, Ganz R: Periacetabular osteotomy, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip.  Philadelphia, PA, Lippincott-Raven, 1998, pp 789-802.

99.       What is the primary concern for arthrodesis of a failed infected total knee arthroplasty using internal fixation?

 

1-         Recurrent infection

2-         Lack of stability

3-         Lack of soft-tissue coverage

4-         Stress shielding

5-         Stress risers

 

PREFERRED RESPONSE: 1

 

DISCUSSION: Arthrodesis of the failed infected total knee arthroplasty may be accomplished by external fixation, intramedullary rod fixation, and dual plates and screws.  External fixation runs the risk of pin tract infection, although after its removal, there are no metal surfaces left in place.  Intramedullary rods have been used successfully in the treatment of infected total knees, although they also leave metal within the region of the infection.  The dual plate technique of knee fusion is useful in patients with rheumatoid arthritis who require fusion in the absence of infection because it provides good initial stability and avoids the use of external pins.  However, in the face of infection, the large surface area of the screws and plates may serve as a site for bacteria to hide within a glycocalyx and make eradication of the infection almost impossible.

 

REFERENCE: Windsor RE: Knee arthrodesis, in Insall JN, Windsor R, Kelly M, et al (eds): Surgery of the Knee.  New York, NY, Churchill Livingstone, 1993, pp 1103-1116.

100.     Oxidation of polyethylene after sterilization occurs most rapidly when the implant undergoes

 

1-         gamma radiation in air.

2-         gamma radiation in nitrogen.

3-         gamma radiation in argon.

4-         gas plasma exposure.

5-         ethylene oxide exposure.

 

PREFERRED RESPONSE: 1

 

DISCUSSION: The use of gamma radiation to sterilize polyethylene will result in the formation of free radicals in the material that increase the susceptibility of the material to oxidation and wear.  The packaging can also have an impact.  If the polyethylene is packaged in air, the oxygen in the packaging can significantly oxidize the material on the shelf prior to clinical use.  Gas plasma and ethylene oxide sterilization do not appear to increase oxidation of polyethylene.

 

REFERENCES: Simon SR (ed): Orthopaedic Basic Science.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486.

Wright TM: Ultra-high molecular weight polyethylene, in Morrey BF (ed): Joint Replacement Arthroplasty.  New York, NY, Churchill Livingstone, 1991, pp 37-46.

Collier JP, Sutula LC, Currier BH, et al: Overview of polyethylene as a bearing material: Comparison of sterilization methods.  Clin Orthop 1996;333:76-86.

 

FOR ALL MCQS CLICK THE LINK ORTHO MCQ BANK