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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 81 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 1601

Topic: 3. Adult Reconstruction (Hip & Knee)
What postoperative complication occurs at a significantly higher rate in patients undergoing bilateral simultaneous total knee arthroplasty than in patients undergoing unilateral total knee arthroplasty?
. Aseptic loosening
. Mortality
. Infection
. Bleeding
. Limited motion requiring manipulation

Correct Answer & Explanation

. Mortality

Explanation

Parvizi and associates studied the 30-day mortality rate after more than 22,000 total knee arthroplasties and found that the rate after bilateral total knee arthroplasty was significantly higher than after unilateral total knee arthroplasty. Aseptic loosening, bleeding, and range of motion have not been shown to be statistically different between patients who had unilateral and simultaneous bilateral total knee arthroplasty.

Question 1602

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 125 is the anteroposterior knee radiograph of a 65-year-old man who has been treated for knee pain for 6 years. His pain is constant and is worse when walking up and down stairs and when sitting for a prolonged period. He has medial joint line tenderness and a positive patellofemoral grind test finding. His knee is stable to varus and valgus stress. A Lachman test result is 2+. He had a trial of nonsteroidal anti-inflammatory medications with good relief until 4 months ago. Physical therapy has provided minimal relief, and he has undergone a series of intra-articular injections with corticosteroids. The last 2 injections each provided 1 week of pain relief. What is the most appropriate next treatment option?

. Repeat intra-articular injection
. High tibial osteotomy
. Total knee arthroplasty (TKA)
. Unicompartmental knee arthroplasty

Correct Answer & Explanation

. Total knee arthroplasty (TKA)

Explanation

DISCUSSIONOsteoarthritis is a complex disease. Multiple studies have demonstrated a genetic predisposition and critical role of proinflammatory cytokines in the disease process. Osteoarthritis of the knee has a multifactorial pathogenesis. It is age related and affects women more commonly than men. It is also influenced by such factors as obesity, trauma, repetitive use, muscle weakness, and joint laxity. The treatment of osteoarthritis is multimodal.Nonsurgical treatments include nonsteroidal anti-inflammatory medications, intra-articular injections, weight loss, and physical therapy. Surgical treatments include osteotomy and unicompartmental and TKA.

Question 1603

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is considered a disadvantage of knee disarticulation when compared with transfemoral amputation?

. Increased energy expenditure
. Worse end-bearing surface
. Asymmetry of the prosthetic knee joint
. More pain with weight bearing
. More stump complications in pediatric patients

Correct Answer & Explanation

. Asymmetry of the prosthetic knee joint

Explanation

The decision to perform a transfemoral amputation versus a knee disarticulation remains controversial because there are advantages and disadvantages to each procedure. One potential advantage of the knee disarticulation is that energy expenditure during walking may be less than that for a transfemoral amputee. Another advantage is that the knee disarticulation provides for an end-bearing residual limb. The knee disarticulation also includes complete preservation of the thigh muscles, leading to better muscular balance, and the bulbous shape of the residual limb leads to increased stability of the prosthesis. Disadvantages of knee disarticulation include limitations in knee-joint prosthetic components and concerns regarding the cosmesis of the prosthesis, as well as the asymmetry of the knee joint with respect to sitting and gait. Because knee disarticulations are relatively uncommon compared to transfemoral amputations, many prosthetists may have less familiarity with the fabrication and fit of this prosthesis. One of the more important issues with respect to kneedisarticulation versus transfemoral amputation is the degree of trauma involving the soft tissue around the knee, as increased tissue trauma may lead to painful residual limbs and eventually the need for revision amputation at a higher level. If the residual limb of the knee disarticulation is unable to accommodate the distal-end weight bearing of the socket, then patients with a knee disarticulation may experience decreased levels of function compared with patients undergoing transfemoral amputation.

Question 1604

Topic: 3. Adult Reconstruction (Hip & Knee)
Changes to the properties of ultra-high molecular weight polyethylene with increasing irradiation dose include improved
. resistance to oxidation.
. ultimate tensile strength.
. resistance to crack propagation.
. fracture toughness.
. volumetric wear.

Correct Answer & Explanation

. volumetric wear.

Explanation

DISCUSSION: Increased irradiation doses cause a decrease in the mechanical properties of the polyethylene, resulting in a decrease in ultimate tensile strength, fracture toughness, and resistance to crack propagation. Irradiation leads to the production of free radicals, requiring a step in the manufacturing process (melting, annealing, vitamin E doping) to stabilize the free radicals and reduce the potential for oxidation. Wear resistance is improved with irradiation; however, there is minimal benefit with doses of greater than 10 Mrads. REFERENCES: Collier JP, Currier BH, Kennedy FE, et al: Comparison of cross-linked polyethylene materials for orthopaedic applications. Clin Orthop Relat Res 2003;414:289-304. Gordan AC, D’Lima DD, Colwell CW Jr: Highly cross-linked polyethylene in total hip arthroplasty. J Am Acad Orthop Surg 2006;14:511-523. Jacobs CA, Christian CP, Greenwald AS, et al: Clinical performance of highly cross-linked polyethylenes in total hip arthroplasty. J Bone Joint Surg Am 2007;89:2779-2786.

Question 1605

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following factors will adversely affect bone ingrowth in a revision porous-coated stem?
. Pore size of 400 mm
. Interface instability of 25 mm of micromotion
. Use of a nonmodular implant
. Noncircumferential metaphyseal patch coating
. Failure of ingrowth in the previous stem

Correct Answer & Explanation

. Noncircumferential metaphyseal patch coating

Explanation

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.

Question 1606

Topic: 3. Adult Reconstruction (Hip & Knee)
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?
. Medial and superior
. Medial
. Lateral and superior
. Anterior and inferior
. Posterior and lateral

Correct Answer & Explanation

. Anterior and inferior

Explanation

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. Any medial positioning will produce impingement of the prosthesis neck on the rim, and superior placement produces improper hip mechanics.

Question 1607

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following surgical techniques is associated with an increased incidence of patellar complications after total knee arthroplasty?
. Medialization of the patellar component
. Symmetric patellar osteotomy
. Use of metal-backed patellar components
. Maintaining a patellar thickness of 12 to 15 mm
. External rotation of the femoral component

Correct Answer & Explanation

. Use of metal-backed patellar components

Explanation

Metal-backed patellar components have been associated with a higher failure rate. Some of the observed problems include poor bone ingrowth, peg failure, dissociation of the metal plate and polyethylene button, and component fracture.

Question 1608

Topic: 3. Adult Reconstruction (Hip & Knee)

A year-old man with a history of Legg-Calve-Perthes disease underwent a right hip resurfacing 3 years ago with no perioperative complications. Hip pain has developed gradually during the last 4 months. Radiographs show no evidence of fixation loosening or any adverse changes at the femoral neck. No periarticular osteolysis is evident. What is the most appropriate management of this condition?

. Continue to observe with repeat radiographs in 6 months B. Fluoroscopic-guided iliopsoas tendon cortisone injection C. Hip aspiration
. Serum cobalt and chromium levels and metal-reduction MRI scan

Correct Answer & Explanation

. Serum cobalt and chromium levels and metal-reduction MRI scan

Explanation

DISCUSSION:Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM)  hip  arthroplasties.  All  patients  with  painful  MOM  hip  arthroplasties  should  be  examined  for fixation  loosening,  wear/osteolysis,  and  infection—no  differently  than  patients  without  MOM  hip arthroplasties.  It  is  recommended  to  obtain  serum  trace  element  levels.  If  the  levels  are  high,  cross- sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.

Question 1609

Topic: 3. Adult Reconstruction (Hip & Knee)
A 75-year-old woman undergoes hybrid total hip arthroplasty for osteoarthritis. A postoperative radiograph obtained in the recovery room is shown in Figure 18. Treatment should now consist of
. open reduction and internal fixation with strut graft and cerclage wire.
. open reduction and internal fixation with a plate, screws, and bone graft.
. exchange of the femoral components with insertion of a long stem cementless implant.
. cast immobilization.
. minimal weight bearing and observation.

Correct Answer & Explanation

. minimal weight bearing and observation.

Explanation

DISCUSSION: Intraoperative femoral fractures can often be avoided by careful preoperative planning to optimize implant design and size. Most fractures occur during implantation of a cementless implant; many can be avoided by careful femoral preparation and component implantation, with particular caution in osteopenic bone. Intraoperative femoral fractures are managed according to fracture severity. Minor cracks that do not affect stability or femoral integrity can often be managed intraoperatively with cerclage fixation, limited weight bearing, and observation. Femoral fractures that compromise implant stability or femoral integrity require fracture fixation with cerclage wires, strut grafts, or plates and may require conversion to a long stem implant. This patient’s fracture is nondisplaced and the implant is well seated; therefore, limited weight bearing is considered appropriate management.

Question 1610

Topic: 3. Adult Reconstruction (Hip & Knee)
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
. threaded (screw-in) cup with a hydroxyapatite coating.
. protrusio cage reconstruction with a cemented cup.
. large cementless cup with bone grafting of defects.
. small cup with a high and lateral hip center.
. bulk allograft reconstruction of the defect with a cemented cup.

Correct Answer & Explanation

. large cementless cup with bone grafting of defects.

Explanation

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.

Question 1611

Topic: 3. Adult Reconstruction (Hip & Knee)

He reports that he had no problems with the knee until 6 weeks ago when he noted the gradual onset of pain following a colonoscopy. Examination reveals a painful, swollen knee. Knee aspiration reveals a WBC count of 40,000/mm3. Management should consist of

. suppressive antibiotics.
. open irrigation and debridement with polyethylene exchange.
. one-stage resection arthroplasty and reimplantation.
. two-stage resection arthroplasty and reimplantation.
. arthroscopic irrigation and debridement.

Correct Answer & Explanation

. suppressive antibiotics.

Explanation

The treatment of choice for a late hematogenous infection is two-stage resection arthroplasty and reimplantation, with parenteral antibiotics prior to reimplantation. This is particularly true when septic loosening has occurred as in this patient. Open irrigation and debridement with polyethylene exchangehas been used successfully when the duration of symptoms is 3 weeks or less. Long-term suppressive antibiotics are most commonly used when the patient’s medical condition precludes further surgery. Delayed reimplantation has been shown to be superior to immediate reimplantation in multiple studies. Little data support the use of arthroscopic irrigation and debridement.

Question 1612

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following bearing surface combinations has shown the lowest in vivo wear rates in total hip arthroplasty?
. Cobalt-chromium alloy femoral head-on-cobalt-chromium alloy socket
. Cobalt-chromium alloy femoral head-on-polyethylene socket
. Titanium femoral head-on-polyethylene socket
. Ceramic femoral head-on-ceramic socket
. Ceramic femoral head-on-polyethylene socket

Correct Answer & Explanation

. Ceramic femoral head-on-ceramic socket

Explanation

DISCUSSION: Ceramic bearings, made of alumina, have the lowest in vivo wear rates of any bearing combination, 0.5 to 2.5 µ per component per year. Laboratory wear rates for metal-on-metal are lower than those for metal-on-polyethylene bearings, ranging from 2.5 to 5.0 µ per year. Titanium used for bearing surfaces has a high failure rate because of a poor resistance to wear and notch sensitivity. Wear rates for ceramic-on-polyethylene bearings have varied, ranging from 0 to 150 µ.

Question 1613

Topic: 3. Adult Reconstruction (Hip & Knee)
An otherwise healthy 65-year-old woman has pain 2 years after total hip arthroplasty. The clinical photograph below demonstrates her skin envelope, and associated radiograph. Her C-reactive protein level is normal, and her erythrocyte sedimentation rate is mildly elevated. The white blood cell count is normal. Hip aspiration attempted under fluoroscopy generates no fluid. What is the best definitive treatment?
. Repeat left hip aspiration
. Initiation of a wound care consult and oral antibiotics
. Irrigation and debridement with closure of the dehisced wound, performance of a liner exchange, and administration of intravenous antibiotics
. Debridement of the wound, explant of the total hip, placement of a spacer, and administration of intravenous antibiotics

Correct Answer & Explanation

. Debridement of the wound, explant of the total hip, placement of a spacer, and administration of intravenous antibiotics

Explanation

DISCUSSION: This patient clearly has a chronically infected total hip arthroplasty, indicated by the open, draining sinus, as well as trochanteric bone resorption on radiographs, and two years of pain. Repeating the hip aspiration is unnecessary, because infection is already evident. Initiating a wound care consult would not address the underlying infection. The determination whether to retain the components or perform a two-stage exchange is based more on the acuity of infection. In this particular case, the patient is chronically infected. Irrigation and debridement with a liner exchange and retention of the components are reserved for the acute setting.

Question 1614

Topic: Total Hip Arthroplasty (THA)
Design and manufacturing of a metal-on-metal articulation has an important influence on the tribology. Which of the following statements best characterizes the type of contact that is best for metal-on-metal articulations?
. Equatorial contact should exceed polar contact.
. Polar contact should exceed equatorial contact.
. Polar and equatorial contact should be equal by exactly duplicating radii.
. The “bedding in” process makes consideration of polar equatorial contact unimportant.
. The stiffness of metal-on-metal articulations makes consideration of polar equatorial contact unimportant.

Correct Answer & Explanation

. Polar contact should exceed equatorial contact.

Explanation

DISCUSSION: It is important that the radii of a metal-on-metal head to cup articulation be such that there is polar contact. As the radii become closer to equal, conditions favor higher frictional torque and equatorial seizing. The “bedding in” of metal-on-metal surfaces and their stiffness are both components of the properties considered in the design of polar contact surfaces.

Question 1615

Topic: 3. Adult Reconstruction (Hip & Knee)
In patients undergoing elective hip or knee arthroplasty who are not at elevated risk (beyond the risk associated with the surgery) for venous thromboembolism or bleeding, using pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism was assigned what grade of recommendation by the 2011 AAOS Clinical Practice Guideline, Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty?
. Strong
. Moderate
. Limited
. Inconclusive

Correct Answer & Explanation

. Moderate

Explanation

DISCUSSION: Using pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism in patients undergoing elective hip or knee arthroplasty who are not at elevated risk beyond that of the surgery itself for venous thromboembolism or bleeding was given a moderate grade of recommendation in the 2011 AAOS Clinical Practice Guideline referenced above.

Question 1616

Topic: 3. Adult Reconstruction (Hip & Knee)
When converting the knee shown in Figure 20 to a total knee arthroplasty, satisfactory outcome can be expected in what percent of patients?
. Less than 5%
. Less than 50%
. 60%
. 80%
. 90%

Correct Answer & Explanation

. Less than 50%

Explanation

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%). 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.

Question 1617

Topic: Total Hip Arthroplasty (THA)

Figures 24a and 24b are the radiographs of a 7-year-old boy who fell off the monkey bars and has a closed injury. His hand appears warm and well perfused with an absent radial pulse. What is the best initial treatment?

. Immediate open reduction with an anterior approach
. Immediate open reduction with a posterior approach
. Obtain an immediate arteriogram
. Perform closed reduction and reassess perfusion and pulse

Correct Answer & Explanation

. Immediate open reduction with an anterior approach

Explanation

DISCUSSIONIn displaced extension-type supracondylar fractures, the neurovascular structures get kinked anteriorly or anteromedially related to the displacement. In almost all cases, there is a spontaneous resolution of this kink following closed fracture reduction.

Question 1618

Topic: Total Hip Arthroplasty (THA)

A 23-year-old man is involved in a motor vehicle accident. An AP radiograph is shown in Figure 29a, and axial and sagittal CT scans are shown in Figures 29b and 29c. Neurologic examination shows 1/5 strength of his quadriceps and iliopsoas on the right, with 1/5 quadriceps function on the left. Definitive treatment of his injury should consist of Review Topic

. anterior corpectomy with interbody strut.
. posterior fusion with instrumentation and posterolateral decompression.
. closed reduction and a thoracolumbosacral orthosis (TLSO).
. anterior reduction and instrumentation.
. supine bed rest for 6 weeks, followed by immobilization in a TLSO.

Correct Answer & Explanation

. anterior corpectomy with interbody strut.

Explanation

The imaging studies show a fracture-dislocation. Surgical treatment of this injury consists of a decompression reduction, stabilization, and fusion. A posterolateral decompression can also be performed as necessary. An isolated anterior procedure in this type of injury is contraindicated. The anterior longitudinal ligament is most likely intact; therefore, an anterior procedure further destabilizes the spine. Reduction by an anterior approach would also be difficult. Nonsurgical management of the neurologic injury in this patient is not indicated.

Question 1619

Topic: 3. Adult Reconstruction (Hip & Knee)
Fully dense alumina and zirconia materials have been used as bearing materials in hip arthroplasty to provide greater wear resistance than polished metallic surfaces. Although both have shown reduced wear clinically, what concerns continue to exist about the use of zirconia?
. Less tough than alumina, increasing the chance of brittle failure
. May undergo a phase change that markedly reduces wear resistance
. Not as biocompatible as other bearing materials
. Susceptible to crevice corrosion
. Susceptible to fatigue fracture

Correct Answer & Explanation

. May undergo a phase change that markedly reduces wear resistance

Explanation

DISCUSSION: Zirconia as a bearing surface is “metastable,” meaning that, in the microstructure of the material the zirconia molecules are ordered in a tetragonal fashion, but they can easily transform to a monoclinic microstructure that is less wear resistant. Transformation can occur with input of enough energy (e.g., thermal energy imparted by steam sterilization or mechanical energy at the bearing surface). Zirconia was introduced as an alternative to alumina because it has a higher toughness, making it less susceptible to gross fracture (ceramics do not undergo fatigue fracture, but rather fail from a process of slow crack growth). Zirconia is highly biocompatible (as are many ceramics) and is essentially immune to corrosive processes that can plague metallic alloys such as stainless steel.

Question 1620

Topic: 3. Adult Reconstruction (Hip & Knee)

A prospective, randomized controlled trial of 150 patients undergoing total hip arthroplasty is performed to test whether repair of the capsule during a posterior approach reduces post-operative dislocations in the first three months. The study found no difference in dislocation rate if the capsule was repaired versus not repaired (p = .34). Subsequently, a multicenter follow-up study of 2000 patients showed that repairing the capsule led to a decreased dislocation rate in the first three months (p = .03). Assuming the second study reflects reality, which of the following errors occurred in the first study?

. Observer bias
. Type-II error
. Alpha error
. Type-I error
. Confounding error

Correct Answer & Explanation

. Type-II error

Explanation

In this situation, the null hypothesis was accepted when it should have been rejected. This is a type-II error.A study can have two types of errors. Type-I errors, or alpha errors, occur when the null hypothesis is rejected when it should have been accepted. The alpha level refers to the probability of a type-I error. By convention, the alpha level of significance is set at 0.05, which means that we accept the finding of a significant association if there is less than a one in twenty chance that the observed association was due to chance alone. Type-II errors, or beta errors, occur when the null hypothesis is accepted when it should be rejected. This often occurs when studies are underpowered. In the example above, the null hypothesis is that repair of the capsule does not reduce dislocations within the first three months. Since the first study did not show astatistically significant difference, the null hypothesis was accepted. Since a more powered study showed that repair of the capsule does reduce dislocations, the null hypothesis should have been rejected in the initial study (if it was adequately powered).Fosgate et al. review the importance of sample size calculations when performing research. They state that sample size ensures statistical significance if the subsequent data collection is perfectly consistent with the assumptions made for the sample size calculation (assuming power was set as 50% or greater).Illustration A shows the difference between type-I and type-II errors. Video V is a lecture discussing statistical definition review of PPV, NPV, sensitivity and specificity.Incorrect Answers:

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