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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 54 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1061

Topic: 3. Adult Reconstruction (Hip & Knee)

What are the optimal conditions for leaving the acetabular shell in place, replacing the acetabular liner, and grafting the osteolytic defect shown in Figure 39?

. Nonmodular implant
. Instability
. Well-designed, well-fixed modular implant
. Complete radiolucency of the acetabular component
. Migration of the acetabular component

Correct Answer & Explanation

. Well-designed, well-fixed modular implant

Explanation

DISCUSSION: Dense pods of ingrowth into the porous coating of cementless ingrowth sockets are seen.  Channels through the non-ingrown portion allow access to the trabecular bone of the ilium.  Polyethylene wear debris can enter these areas through screw holes.  Expansile, lytic lesions can result, which can become large without compromising implant fixation.  Loosening is late and results from catastrophic loss of bone.  A well-fixed acetabular component with a modular design, a well-designed locking mechanism, and a good survivorship history is a candidate for exchange of the liner and grafting of the osteolytic lesion.REFERENCES: Ries MD: Complications in primary total hip arthroplasty: Avoidance and management.  Wear.  Instr Course Lect 2003;52:257-265.Dumbleton JH, Manley MT, Edidin AA: A literature review of the association between wear rate and osteolysis in total hip arthroplasty.  J Arthroplasty 2002;17:649-661.Pelicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000,pp 175-180.

Question 1062

Topic: 3. Adult Reconstruction (Hip & Knee)

When performing a revision total knee arthroplasty, trial components are inserted and the knee is stable in extension and loose in flexion. Which step should be taken to create a stable construct?

. Insert a constrained tibial insert
. Insert a thicker tibial component
. Insert a larger femoral component
. Augment the distal portion of the femoral component

Correct Answer & Explanation

. Insert a constrained tibial insert

Explanation

DISCUSSIONThe surgeon is facing a common scenario that occurs in revision knee surgery: a loose flexion gap with an appropriate extension gap. A flexion gap can be tightened by translating the femoral component more posteriorly and using an oversized femoral component. Insertion of a thicker tibial component changes both the flexion and extension gap. Augmentation of the distal femur tightens only the extension gap. A constrained insert would only be indicated if oversizing of the femoral component did not adequately tension the flexion gap.

Question 1063

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the strongest contraindication to unicompartmental knee arthroplasty (UKA)?

. Patient age of younger than 60 years
. Patient age of older than 80 years
. Anterior cruciate ligament (ACL) deficiency
. Varus deformity of 5 degrees
. Outerbridge grade II chondromalacia of the patella

Correct Answer & Explanation

. Patient age of younger than 60 years

Explanation

DISCUSSION: UKA prostheses cannot substitute for an absent ACL, and if arthroplasty is indicated, these patients should receive a total knee arthroplasty rather than a UKA.  Age is not an absolute contraindication, and the procedure has been advocated for young patients as well as older patients if they meet the appropriate indications for an arthroplasty.  Varus deformities of the mechanical axis of up to 10 degrees generally are not a contraindication to unicompartmental arthroplasty, as long as the knee can be properly balanced at the time of surgery.  Modest chondromalacia of the patellofemoral joint, especially if asymptomatic, is not a contraindication to UKA.REFERENCES: Lotke PA (ed): Knee Arthroplasty: Master Techniques in Orthopaedic Surgery.  New York, NY, Raven Press, 1995, pp 275-293.Insall JN, Windsor RE, Scott WN, et al (eds): Surgery of the Knee, ed 2.  New York, NY, Churchill Livingstone, 1993, pp 805-814.Tabor OB Jr, Tabor OB: Unicompartmental arthroplasty:  A long-term follow-up study.J Arthroplasty 1998;13:373-379.

Question 1064

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Enlarged acetabular rim
. Cavitary central defect
. Superior migration of 2 cm
. Deficient anterior wall
. Pelvic discontinuity

Correct Answer & Explanation

. Enlarged acetabular rim

Explanation

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.

Question 1065

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 36 shows the radiograph of a patient who has hip pain and is unable to ambulate. What is the most appropriate management for this patient?

. Bisphosphonates
. Protected weight bearing
. Open reduction and internal fixation
. Revision total hip arthroplasty
. Resection arthroplasty

Correct Answer & Explanation

. Bisphosphonates

Explanation

DISCUSSION: The patient has a periprosthetic fracture of the greater trochanter - Vancouver A.  The reason for the fracture of the greater trochanter is the extensive periarticular osteolysis that has occurred as a result of polyethylene wear.  The latter is demonstrated by eccentric seating of the large femoral head in the acetabulum.  The most appropriate management is to reverse the osteolysis process, which involves exchange of the acetabular liner with or without revision of the other components depending on their fixation and position.  The greater trochanter can also be fixed during revision surgery.REFERENCES: Duncan CP, Masri BA: Fractures of the femur after hip replacement.  Instr Course Lect 1995;44:293-304.Parvizi J, Rapuri VR, Purtill JJ, et al: Treatment protocol proximal femoral periprosthetic fractures.  J Bone Joint Surg Am 2004;86:8-16.

Question 1066

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 2a and 2b show the radiographs of a 72-year-old man with aseptic loosening of the tibial component of his total knee arthroplasty. Optimal management should include

. tibial revision only, without stems or augmentations.
. tibial revision only, with stems and augmentations.
. revision of the tibial and femoral components, without stems or augmentations.
. revision of the tibial and femoral components, with stems and augmentations.
. primary arthrodesis.

Correct Answer & Explanation

. tibial revision only, without stems or augmentations.

Explanation

DISCUSSION: The radiographs show massive subsidence of the lateral side of the tibia with severe tibial bone loss and a fractured proximal fibula.  Reconstruction should consist of a large metal or bony lateral tibial augmentation, and a stem long enough to bypass the defect is required.  The femoral and tibial components are articulating without any remaining polyethylene medially; therefore, the femoral component is damaged and needs revision.The insertions of the lateral ligaments are absent, thereby rendering the lateral side of the knee predictably unstable.  Also, the large valgus deformity compromises the medial collateral ligament.  The posterior cruciate ligament is also likely to be deficient with this much tibial bone destruction.  The patient requires a posterior stabilized femoral component at the minimum, and possibly a constrained femoral component.  Retention of the femoral component, even though it may be well-fixed, jeopardizes the outcome.REFERENCES: Lotke PA, Garino JP: Revision Total Knee Arthroplasty.  New York, NY, Lippincott-Raven, 1999, pp 137-250.Insall JN, Windsor RE, Scott WN, et al: (eds): Surgery of the Knee, ed 2.  New York, NY, Churchill Livingstone, 1993, pp 935-957.Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000,pp 339-365.

Question 1067

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Lateralization of the greater trochanter without advancement
. Use of a shorter neck length
. Use of a constrained acetabular component
. Use of a small diameter head
. High cup abduction angle

Correct Answer & Explanation

. Lateralization of the greater trochanter without advancement

Explanation

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.

Question 1068

Topic: 3. Adult Reconstruction (Hip & Knee)

A 64-year-old woman sustains a fracture to her distal femur 5 years after undergoing total knee arthroplasty. When choosing between locked femoral plating and retrograde femoral nailing, which factor is important to consider based on this patient’s surgical record?

. Previous surgical approach
. Previous tourniquet time
. Implant model
. Presence of an anterior femoral notch

Correct Answer & Explanation

. Previous surgical approach

Explanation

DISCUSSIONTreatment of periprosthetic supracondylar femoral fractures is complex and may involve the use of a retrograde intramedullary femoral nail or locked or unlocked femoral plate. Knowledge of certain measurements specific to the model of the implant, specifically to the minimal intercondylar distance and the position of the notch on the femoral component in relation to the intramedullary canal, is crucial when choosing a retrograde nail over a locked femoral plate. Although the surgical approach, presence of an anterior femoral notch, and previous tourniquet time are interesting to consider, none of these factors would preclude the ability to proceed with femoral intramedullary nailing.CLINICAL SITUATION FOR QUESTIONS 128 THROUGH 130Figure 128 is the radiograph of a 78-year-old nursing home resident who has hypertension and peripheral vascular disease. He has developed acute severe hip pain 20 years after undergoing a cementless total hip arthroplasty (THA) and subsequent revision for instability. He was previously ambulatory with a walker and now can no longer ambulate. His erythrocyte sedimentation rate is 8 mm/h (reference range [rr], 0-20 mm/h) and C-reactive protein level is

Question 1069

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 9a and 9b show the radiographs of a 75-year-old man who underwent a revision total knee arthroplasty with a long-stemmed tibial component. In rehabilitation, he reports fullness and tenderness in the proximal medial leg (at the knee). The strategy that would best limit this postoperative problem is use of

. a base plate with an offset tibial stem attachment.
. a bone ingrowth surface on the augment.
. a nonstemmed tibial base plate.
. allograft bone instead of metal augments.
. bone cement to smooth the outline of the proximal medial tibia.

Correct Answer & Explanation

. a base plate with an offset tibial stem attachment.

Explanation

DISCUSSION: The problem with this reconstruction is the medial protrusion of the base plate.  The use of a base plate with an offset stem can prevent the protrusion and thus the impingement and pain.  Allograft bone or smoothing the outline with cement would be just as prominent and likely to cause pain.  An ingrowth surface may improve soft-tissue attachment but would still leave the implant protruding medially and likely to cause pain.  A nonstemmed tibial base plate would lead to less medial protrusion but at the expense of a smaller area for load carriage on the proximal tibia.REFERENCE: Gustke K: Cemented tibial stems are not requisite in revision.  Orthopedics 2004;27:991-992.

Question 1070

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 36a and 36b are the radiographs of a 79-year-old woman who has been experiencing increasing tibial pain 10 years after undergoing revision total knee arthroplasty. There is no evidence of infection. What is the most appropriate treatment?

. Retain the components and implant a tibial strut allograft
. Revise the tibial component with a metaphyseal cone and metaphyseal uncemented stem
. Revise the tibial component with a metaphyseal cone and a press-fit diaphyseal-engaging stem
. Revise the tibial component with a long cemented diaphyseal-engaging stem

Correct Answer & Explanation

. Retain the components and implant a tibial strut allograft

Explanation

DISCUSSIONStems are available for cemented and press-fit implantation. To be effective, press-fit stems should engage the diaphysis (Figures 36c and 36d). They also assist in obtaining correct limb alignment. Short metaphyseal-engaging stems are associated with failure rates between16% and 29%. Cemented stems may be shorter than press-fit stems because they do not have to engage the diaphysis. Short, fully cemented stems offer the advantage of metaphyseal fixation. Hybrid stem fixation makes use of the metaphysis for cement fixation with metaphyseal cones or sleeves and diaphyseal-engaging press-fit stems.RESPONSES FOR QUESTIONS 37 THROUGH 40Lateral femoral cutaneous nerveLateral femoral circumflex arterySuperior gluteal nerveSuperior gluteal arterySciatic nerveFemoral arteryFemoral veinFemoral nerveSaphenous branch of the femoral nerveProfunda femoris arteryInferior gluteal nerveMatch each description below with the anatomic structure listed above.

Question 1071

Topic: 3. Adult Reconstruction (Hip & Knee)
  • Which of the following neurovascular structures is at greatest risk during the introduction of acetabular component fixation screws during total hip replacement?
. Sciatic nerve
. Superior gluteal artery
. Profunda femoris artery
. Femoral artery and nerve
. External iliac artery and vein

Correct Answer & Explanation

. Sciatic nerve

Explanation

Wasielewski et al found on reviewing the literature that vascular injuries during acetabuIar screw placement are an uncommon yet devastating complication of total hip arthroplasty. Damage to the external iliac artery was the most frequent injury yet injury to the external iliac vein and the superior gluteal artery has also been reported Based upon their anatomic study and development of a quadrantsystem they found that the posterior superior and posterior inferior quadrants of the acetabulum are the safest locations for screw placement because of better bone stock as well as less neurovascular structures as compared to the anterior quadrants.

Question 1072

Topic: 3. Adult Reconstruction (Hip & Knee)

Venous thromboembolism may occur after total joint arthroplasty. The risk of this complication is elevated in patients with

. a BMI lower than 30.
. diabetes mellitus, with a hemoglobin A1c test result less than 7.
. tranexamic acid use.
. metabolic syndrome.

Correct Answer & Explanation

. a BMI lower than 30.

Explanation

DISCUSSION:Obesity, a prior history of venous thromboembolism, and metabolic syndrome have all been associated with  an  increased  risk  of  thromboembolism.  A  recent  meta-analysis  showed  that  diabetes  had  no significant relationship with venous thromboembolism following hip or knee arthroplasty. Tranexamic acid is an antifibrinolytic agent that has been shown to reduce blood loss substantially following hip and knee arthroplasty. It has also been shown to be safe in patients with severe medial comorbidities and a prior history of venous thromboembolism.

Question 1073

Topic: Total Knee Arthroplasty (TKA)

A year-old obese man with a body mass index of 42 comes into the office with left knee pain 1 year after undergoing an uncomplicated left medial unicompartmental knee arthroplasty (UKA). Radiographs show a loose tibial component in varus. What is the most appropriate next step to treat this failed construct?

. Aspiration of joint fluid to obtain a cell count
. Revision of the UKA using primary total knee arthroplasty (TKA) components
. Revision of the UKA using a revision TKA with augments
. Procurement of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level

Correct Answer & Explanation

. Aspiration of joint fluid to obtain a cell count

Explanation

DISCUSSION:This patient likely is experiencing failure of the UKA secondary to poor patient selection. In this young, heavy man, the component likely loosened due to the ongoing varus alignment of the knee and his elevatedweight. Despite this likely scenario, the next step is determining whether an infection is the cause of his pain. Prior to obtaining an aspiration, the surgeon can order ESR and CRP studies to determine whether aspiration  is  warranted.  If  the  laboratory  studies  are  unremarkable,  the  surgeon  likely  can  forgo  theaspiration and proceed to a revision TKA with possible augments on standby.

Question 1074

Topic: Total Hip Arthroplasty (THA)

Which of the following factors is most closely associated with early postoperative migration of “stand-alone” lumbar interbody fusion cages?

. Pseudarthrosis
. Placement of the cage through a posterior approach
. Placement of the cage laparoscopically through an anterior approach
. Use of tapered rather than cylindrical cages
. Use of BMP-2 rather than autograft in the cage

Correct Answer & Explanation

. Pseudarthrosis

Explanation

DISCUSSION: Postoperative migration of lumbar interbody fusion cages is a rare complication.  It is most commonly seen after placement of the cages through a posterior approach, with instability of the final construct.  It is not associated with the design of the cage, the type of graft used, or a resultant pseudarthrosis.REFERENCES: McAfee PC: Interbody fusion cages in reconstructive operations on the spine.  J Bone Joint Surg Am 1999;81:859-880.McAfee PC, Cunningham BW, Lee GA, et al: Revision strategies for salvaging or improving failed cylindrical cages.  Spine 1999;24:2147-2153.

Question 1075

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 10 shows patellar radiographs of a 68-year-old woman who underwent bilateral total knee arthroplasty 2 months ago. Following a recent fall onto the left side, she now reports anterior pain in the left knee. A CT scan shows that the femoral and tibial components are appropriately externally rotated and radiographs show acceptable axial alignment and no evidence of loosening. What is the most appropriate treatment option?

. Fracture fixation and bracing
. Lateral retinacular release with proximal realignment
. Tibial component revision
. Distal realignment by medialization of the tibial tubercle
. Revision of the patellar component

Correct Answer & Explanation

. Fracture fixation and bracing

Explanation

DISCUSSION: Treatment of patellofemoral instability after total knee arthroplasty (TKA) is directed by its etiology. In instances of component malpositioning, revision of one or both components is indicated.If the components are determined to be in satisfactory position, soft-tissue procedures can be pursued. Lateral retinacular release is usually the first soft-tissue procedure used to improve patellofemoral mechanics. In this patient, the patellar fracture fragment is so small that it can be excised. Distal realignment is not usually used as the first line of treatment for patellar maltracking following TKA.REFERENCES: Fehring TK, Christie MJ, Lavemia C, et al: Revision total knee arthroplasty: Planning, management, and controversies. Instr Course Lect 2008;57:341-363.Patel J, Ries MD, Bozic KJ: Extensor mechanism complications after total knee arthroplasty. Instr Course Lect 2008;57:283-294.

Question 1076

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman with rheumatoid arthritis is undergoing revision total knee arthroplasty (TKA) during which the medial collateral ligament (MCL) is damaged. Suture anchors are used to attempt primary repair, and a varus-valgus constrained insert also is used. Postsurgically she experiences instability that does not respond to bracing with a 3+ opening to valgus stress (Figure 120). What is the most appropriate surgical option?

. Femoral revision with distal augment
. MCL allograft reconstruction
. Ultracongruent insert
. Rotating-hinge TKA

Correct Answer & Explanation

. Femoral revision with distal augment

Explanation

DISCUSSIONMCL repair or reconstruction may be considered in younger, more active patients, but this intervention is technically demanding and produces variable results. Rotating-hinge TKA is associated with good results in a number of small series that include cases performed with MCL insufficiency or absence. A rotating hinge is preferable over a fixed hinge because of decreased stresses on implants imposed by fixed-hinge devices.

Question 1077

Topic: 3. Adult Reconstruction (Hip & Knee)

At revision, the stem is retained and a new head with a polyethylene bearing is selected. The best option for the head is

. ceramic with a metal sleeve.
. ceramic alone.
. metal with a metal sleeve.
. metal alone.

Correct Answer & Explanation

. ceramic with a metal sleeve.

Explanation

DISCUSSIONCeramic-on-ceramic is a controversial bearing surface typically reserved for younger patients such as this one. Some studies have suggested that the bearing is more expensive and does not really prolong the service life of the implant, although a recent meta-analysis of high-quality trials showed that there is a decreased revision rate with ceramic-on-ceramic, so its use may be justified. Complications of intraoperative bearing fracture and squeaking are more common than with conventional bearings, but pain and function scores are equivalent. Stripe wear associated with a vertical cup and morbid obesity are related to an increased risk for liner fracture. Concerns about head fractures with a new ceramic head and a damaged trunnion have led investigators to conclude that using a harder bearing than the initial bearing surface with a built-in titanium sleeve is probably the best solution when a stem is retained during revision surgery.

Question 1078

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. antibiotics for 6 weeks.
. use of an unlocked brace.
. revision arthroplasty.
. resection of the implants.
. two-stage reimplantation.

Correct Answer & Explanation

. antibiotics for 6 weeks.

Explanation

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.

Question 1079

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old patient with rheumatoid arthritis reports increasing elbow pain and swelling for the past 2 months. She underwent a cemented, semiconstrained elbow arthroplasty 8 years ago. Laboratory studies show a normal peripheral white blood cell count; however, the erythrocyte sedimentation rate and C-reactive protein level are elevated. Radiographs are shown in Figures 48a and 48b. Which of the following organisms is most difficult to eradicate? Review Topic

. Streptococcus viridans
. Staphylococcus epidermidis
. Escherichia coli
. Vibrio parahaemolyticus
. Clostridium difficile

Correct Answer & Explanation

. Streptococcus viridans

Explanation

The patient's history and radiographs are suspicious for a relatively aggressive infection. Staphylococcus epidermidis is difficult to eradicate because of its encapsulation. The lytic area surrounding both the ulnar and humeral components suggests that the prosthesis is also loose. This revision will require component removal, antibiotic spacer placement, and parenteral antibiotics.

Question 1080

Topic: 3. Adult Reconstruction (Hip & Knee)

Hip pain of month duration has developed in a year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. What is this patient's prognosis for infection resolution?

. Good because it is a gram-positive organism
. Good because it is an acute infection
. Poor because it is a gram-positive organism
. Poor because it is a late infection

Correct Answer & Explanation

. Good because it is a gram-positive organism

Explanation

DISCUSSION:The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the  implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin- resistantStaphylococcus epidermidisorganisms treated with a two-stage protocol, the failure rate was21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of California Los Angeles Activity Score, and the 12-item Oxford Knee Score, however.

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