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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 66 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 1301

Topic: 3. Adult Reconstruction (Hip & Knee)

A two-stage exchange arthroplasty is planned for a chronic periprosthetic hip infection. The surgeon debates between utilizing an articulating versus a static antibiotic-loaded polymethylmethacrylate (PMMA) spacer. Which of the following represents an absolute contraindication to the use of an articulating spacer in this scenario?

. Isolation of a multi-drug resistant organism (e.g., MRSA or VRE) from preoperative aspirate.
. Presence of a sinus tract communicating with the joint space.
. Massive uncontained segmental acetabular bone loss precluding the stable seating of a spacer component.
. Patient age greater than 80 years with multiple medical comorbidities.
. A history of a prior failed two-stage exchange arthroplasty.

Correct Answer & Explanation

. Massive uncontained segmental acetabular bone loss precluding the stable seating of a spacer component.

Explanation

Articulating spacers offer the advantages of maintained soft tissue tension, improved patient mobility, and easier reimplantation. However, they require sufficient bone stock to remain stable. Massive, uncontained acetabular bone loss (e.g., Paprosky 3B) or severe abductor mechanism deficiency are contraindications to an articulating spacer because the spacer will dislocate or migrate into the pelvis, causing severe pain and further bone/soft tissue destruction. In these scenarios, a static block spacer (or dowel) is mandatory.

Question 1302

Topic: 3. Adult Reconstruction (Hip & Knee)

In revision total hip arthroplasty (THA), intentionally utilizing a "high hip center" (superiorly and medially displaced compared to the native anatomic center) achieves which of the following biomechanical changes compared to a high and lateralized center?

. Decreased overall joint reaction force
. Increased overall joint reaction force
. Increased bending moment on the femoral stem
. Decreased abductor mechanical advantage
. Increased risk of anterior dislocation

Correct Answer & Explanation

. Decreased overall joint reaction force

Explanation

A high, medialized hip center shortens the body weight moment arm, which decreases the total joint reaction force compared to a lateralized position. However, to maintain abductor tension and leg length, the surgeon must compensate on the femoral side (e.g., using a high-offset stem or increasing neck length).

Question 1303

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with new-onset groin pain 8 years after a primary THA utilizing a large-diameter metal head on a titanium stem with a highly cross-linked polyethylene liner. Serum inflammatory markers are normal. A MARS MRI demonstrates a thick-walled cystic mass communicating with the joint space. What is the most likely primary source of the wear debris causing this presentation?

. Polyethylene liner wear
. Fretting and crevice corrosion at the head-neck junction
. Impingement of the femoral neck on the acetabular rim
. Unrecognized low-virulence periprosthetic joint infection
. Galvanic corrosion between the titanium shell and supplemental screws

Correct Answer & Explanation

. Fretting and crevice corrosion at the head-neck junction

Explanation

This clinical picture describes an adverse local tissue reaction (ALTR) or pseudotumor due to mechanically assisted crevice corrosion (MACC), commonly known as trunnionosis. This is highly associated with large-diameter metal heads on titanium stems, leading to metal ion release even in metal-on-polyethylene bearings.

Question 1304

Topic: Total Hip Arthroplasty (THA)
A patient undergoing revision THA is found to have an acetabular defect with severe ischial osteolysis, superior migration of the acetabular component greater than 3 cm, and the radiographic "teardrop" is completely absent on the AP pelvis radiograph. The Kohler line remains intact. What is the Paprosky classification of this acetabular defect?
. Paprosky IIB
. Paprosky IIC
. Paprosky IIIA
. Paprosky IIIB
. Pelvic discontinuity

Correct Answer & Explanation

. Paprosky IIIA

Explanation

Paprosky IIIA represents severe bone loss with >3 cm of superior migration (often measured from the obturator foramen), severe ischial lysis, and an absent teardrop, but the Kohler line is intact (meaning no medial migration). Paprosky IIIB defects involve medial migration past the Kohler line.

Question 1305

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female sustains a fall 5 years after an uncemented THA. Radiographs show a periprosthetic fracture around the distal tip of the femoral stem. The stem is radiographically loose with subsidence, but there is adequate proximal diaphyseal bone stock remaining. According to the Vancouver classification, what is the most appropriate surgical treatment?

. Open reduction and internal fixation with a lateral locking plate alone
. Revision to a long uncemented proximally porous-coated stem
. Revision to a long uncemented distally fixed (modular or extensively porous-coated) stem
. Revision to a standard length cemented stem with cerclage wiring
. Impaction bone grafting and cementation of a standard length stem

Correct Answer & Explanation

. Revision to a long uncemented distally fixed (modular or extensively porous-coated) stem

Explanation

This is a Vancouver B2 fracture (fracture around the stem, stem is loose, but with adequate bone stock). The gold standard of treatment is revision of the femoral component to a long stem that bypasses the fracture by at least two cortical diameters, typically utilizing a distally fixing cementless stem (e.g., modular fluted tapered stem).

Question 1306

Topic: Total Hip Arthroplasty (THA)

In the setting of recurrent instability after THA, a dual-mobility articulation is often utilized. Which of the following describes the primary tribological mechanism that increases stability in this design?

. The large inner metal head articulates primarily with the small polyethylene liner, preventing cam impingement
. The inner head is constrained within the polyethylene liner to prevent dissociation under distraction forces
. The large outer polyethylene liner articulates with the polished metal acetabular shell at the extremes of motion, increasing the effective head size and jump distance
. The polyethylene liner functions as a bipolar component that locks in full extension
. The skirted modular neck increases the impingement-free range of motion prior to subluxation

Correct Answer & Explanation

. The large outer polyethylene liner articulates with the polished metal acetabular shell at the extremes of motion, increasing the effective head size and jump distance

Explanation

Dual-mobility constructs feature two articulations: a smaller inner articulation (metal/ceramic head in polyethylene) for primary daily motion, and a larger outer articulation (polyethylene liner in a highly polished metal shell) that engages at extremes of motion. This larger outer diameter increases the "jump distance" required for the head to dislocate, significantly reducing the risk of instability.

Question 1307

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex revision total hip arthroplasty, the surgeon performs an extended trochanteric osteotomy (ETO) to remove a well-fixed, extensively porous-coated stem. Which of the following is true regarding the typical ETO fragment?

. It includes the greater trochanter, the lateral half of the proximal diaphysis, and retains the vastus lateralis and abductor insertions
. It includes only the greater trochanter and the abductor insertion, leaving the diaphysis intact
. It must be exactly 15 cm long to ensure healing regardless of stem length
. The vastus lateralis must be detached completely to appropriately mobilize the fragment anteriorly
. Healing typically requires rigid plate fixation in order to counteract the pull of the abductors

Correct Answer & Explanation

. It includes the greater trochanter, the lateral half of the proximal diaphysis, and retains the vastus lateralis and abductor insertions

Explanation

The standard extended trochanteric osteotomy (ETO) fragment includes the greater trochanter and the anterolateral portion of the proximal femoral diaphysis. Crucially, it retains the continuous soft tissue sleeve consisting of the gluteus medius/minimus insertions proximally and the vastus lateralis origin distally, preserving the blood supply and facilitating excellent healing when reattached with cables.

Question 1308

Topic: Total Hip Arthroplasty (THA)

A 78-year-old female presents for revision THA. Radiographs demonstrate a complete transverse separation of the superior and inferior hemi-pelves through the acetabulum. Which of the following surgical constructs is currently considered the most reliable method for achieving initial mechanical stability and long-term biologic fixation in this setting (chronic pelvic discontinuity)?

. Cemented all-polyethylene cup with an ilioischial plate
. Highly porous metal construct (e.g., cup-cage construct or custom triflange acetabular component)
. Impacted cancellous bone graft with a standard hemispherical titanium cup
. Anti-protrusio cage alone
. Bipolar hemiarthroplasty articulating on native acetabular bone

Correct Answer & Explanation

. Highly porous metal construct (e.g., cup-cage construct or custom triflange acetabular component)

Explanation

For chronic pelvic discontinuity, bridging the discontinuity with a construct that provides immediate rigid mechanical stability and allows for biologic ingrowth is the gold standard. Modern techniques heavily favor highly porous metal constructs, such as a cup-cage system, distraction techniques with jumbo tantalum cups, or custom triflange components.

Question 1309

Topic: 3. Adult Reconstruction (Hip & Knee)

You are evaluating a painful THA for possible periprosthetic joint infection (PJI). Joint aspiration yields synovial fluid with a white blood cell (WBC) count of 4,000 cells/ยตL with 85% polymorphonuclear neutrophils (PMNs). According to the 2018 International Consensus Meeting (ICM) criteria, how are these synovial fluid results categorized in the diagnostic scoring system?

. They meet the major criteria for definitive PJI
. They provide 0 points towards the minor criteria for PJI
. They provide minor criteria points but are not definitive for PJI on their own
. They completely rule out PJI
. They indicate a purely mechanical failure without inflammation

Correct Answer & Explanation

. They meet the major criteria for definitive PJI

Explanation

Under the 2018 ICM criteria, a synovial fluid WBC >3,000 cells/ยตL and PMN% >80% are both considered positive minor criteria that contribute points toward the diagnosis of PJI. They do not constitute major criteria (major criteria are a sinus tract communicating with the joint or two positive cultures of the same organism).

Question 1310

Topic: 3. Adult Reconstruction (Hip & Knee)

Wear particles generated from metal-on-metal hip implants or from trunnion corrosion predominantly stimulate an inflammatory response driven by which of the following cell types?

. Neutrophils
. Lymphocytes
. Macrophages
. Eosinophils
. Multinucleated giant cells

Correct Answer & Explanation

. Neutrophils

Explanation

Unlike polyethylene wear debris, which primarily elicits a macrophage-driven response leading to osteoclast activation and osteolysis, metal wear particles and ions (cobalt and chromium) characteristically elicit a lymphocyte-dominated, delayed-type hypersensitivity reaction (Type IV). This is termed ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion) and is a hallmark of adverse local tissue reactions (ALTR) or pseudotumors.

Question 1311

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, combined excessive anteversion of both the acetabular component and the femoral component primarily increases the risk of which sequence of impingement and subsequent dislocation?

. Anterior impingement resulting in an anterior dislocation
. Anterior impingement resulting in a posterior dislocation
. Posterior impingement resulting in a posterior dislocation
. Posterior impingement resulting in an anterior dislocation
. Greater trochanteric impingement resulting in a lateral dislocation

Correct Answer & Explanation

. Anterior impingement resulting in an anterior dislocation

Explanation

Combined excessive anteversion of the cup and the stem moves the femoral neck closer to the posterior rim of the acetabulum during external rotation and extension. This leads to early posterior impingement. The femoral head then levers out of the acetabulum in the opposite direction, causing an anterior dislocation.

Question 1312

Topic: 3. Adult Reconstruction (Hip & Knee)
When considering the use of a "jumbo" hemispherical acetabular cup during revision THA to bridge cavitary defects and achieve rim fit, what is the traditionally accepted minimum diameter threshold that defines an uncemented cup as "jumbo" in a female patient?
. 54 mm
. 58 mm
. 62 mm
. 66 mm
. 70 mm

Correct Answer & Explanation

. 58 mm

Explanation

In revision total hip arthroplasty, a "jumbo" cup is traditionally defined in the literature as an uncemented hemispherical acetabular component with an outer diameter of โ‰ฅ 62 mm in men and โ‰ฅ 58 mm in women. These implants are utilized to achieve secure rim fixation when large segmental or cavitary defects are present.

Question 1313

Topic: 3. Adult Reconstruction (Hip & Knee)
Figure 36 shows an AP radiograph of a 65-year-old man who reports activity-related groin pain. History reveals that he underwent total hip arthroplasty 12 years ago. What is the most likely diagnosis?
. Chondrosarcoma
. Infection
. Wear-induced osteolysis
. Corrosive effect due to dissimilar metals
. Metastatic tumor

Correct Answer & Explanation

. Wear-induced osteolysis

Explanation

DISCUSSION: The AP radiograph demonstrates extensive periacetabular osteolysis. The central hole eliminator has dissociated from the shell and migrated into a lytic defect in the ischium. In a retrieval study, most periacetabular osteolytic lesions had a clear communication pathway with the joint space. Lesions with communication to the joint via several pathways or through a central dome hole (as in this patient) were larger and more likely to be associated with cortical erosion. Although periprosthetic tumors have been described, they are rare and particle-induced inflammation around a prosthesis does not seem to increase the risk for carcinogenesis.

Question 1314

Topic: 3. Adult Reconstruction (Hip & Knee)
Figures 5a and 5b show the radiographs of an active 52-year-old man who has increasing knee pain and progressive varus deformity after undergoing total knee arthroplasty 7 years ago. Examination reveals a small effusion, but he has good motion and stability. What is the most likely diagnosis?
. Wear-induced osteolysis
. Giant cell tumor
. Loose tibial component
. Infection
. Electrolytic reaction caused by dissimilar metals

Correct Answer & Explanation

. Wear-induced osteolysis

Explanation

DISCUSSION: The radiographs show narrowing of the medial joint space, which indicates polyethylene wear and progressive varus alignment. Wear particles incite osteolytic lesions like the one seen on the lateral radiograph.

Question 1315

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following statements best describes the outcome of the routine use of continuous passive motion (CPM) machines after total knee arthroplasty (TKA)?
. CPM is likely to improve early range of motion and final range of motion.
. CPM may improve early range of motion but is unlikely to improve final range of motion.
. CPM is likely to decrease postoperative pain.
. CPM is likely to improve extension but not flexion.
. CPM is likely to restore quicker ambulatory ability.

Correct Answer & Explanation

. CPM may improve early range of motion but is unlikely to improve final range of motion.

Explanation

DISCUSSION: Although CPM machines are used widely in the United States for patients undergoing TKA, the benefit seems to be marginal, if any. Numerous randomized trials have shown that final outcomes after total knee arthroplasty are unaffected by the use of CPM machines postoperatively. Some studies have suggested that use of CPM may improve flexion in the first few weeks, but any short-term benefit from the machine was lost by intermediate-term follow-up. Aside from potential improvement in flexion within the first few postoperative weeks, there does not appear to be any benefit from the machines. There is no improvement in pain, ambulation, or extension. The cost-effectiveness of these machines has been questioned by many authors.

Question 1316

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 142a and 142b are the current radiographs of an 89-year-old woman who had open reduction and internal fixation (ORIF) of a distal periprosthetic femur fracture 4 months ago. An examination reveals well-healed incisions, a painful range of motion from 15 to 85 degrees, and normal neurovascular function. An infection workup, including an erythrocyte sedimentation rate and C-reactive protein level, is negative. The most appropriate treatment option is

. hinge knee bracing with restricted weight bearing.
. revision ORIF.
. revision total knee arthroplasty (TKA).
. above-knee amputation.

Correct Answer & Explanation

. hinge knee bracing with restricted weight bearing.

Explanation

DISCUSSIONCurrent periprosthetic fracture treatments after TKA include ORIF via plating, retrograde nailing, or revision using standard revision TKA components or a distal femoral arthroplasty. Locked plating has demonstrated a trend toward increased nonunion rates when compared to retrograde nailing, as evidenced in this patient. The advanced age of the patient, the presence of failed fixation, and the significant amount of bone loss preclude a trial of further nonsurgical treatment or revision ORIF. A review of 3 methods for treatment of comminuted distal periprosthetic femur fractures in patients older than age 70 demonstrated that distal femur arthroplasty should be considered in patients with advanced age and poor bone quality who require early mobilization. As a result, treatment of this patient with a revision TKA using a distal femoral arthroplasty would be the preferred response because of the bone quality and fracture pattern. Above-knee amputation is a salvage procedure and is not indicated at this time.

Question 1317

Topic: 3. Adult Reconstruction (Hip & Knee)
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
. an increased need for revision.
. a greater limb-length discrepancy.
. a decreased rate of postoperative instability.
. a decreased rate of wear.
. a decreased rate of peroneal nerve palsy.

Correct Answer & Explanation

. an increased need for revision.

Explanation

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.

Question 1318

Topic: 3. Adult Reconstruction (Hip & Knee)
A woman has severe anterior knee pain. Her radiographs indicate end-stage patellofemoral compartment osteoarthritis. The tibiofemoral compartments are preserved. Extensive nonsurgical treatment has failed to provide relief, and she is offered patellofemoral arthroplasty (PFA). What is the most common long-term mode of failure for PFA using an implant with an onlay prosthesis design?
. Infection
. Patellar instability
. Aseptic loosening
. Progression of tibiofemoral arthritis

Correct Answer & Explanation

. Progression of tibiofemoral arthritis

Explanation

Contemporary onlay-design trochlear prostheses in PFA replace the entire anterior trochlear surface. Previous inlay designs were inset within the native trochlea and carried a higher risk of catching and patellar instability, particularly in patients with trochlear dysplasia; they also generally have higher failure rates. The current most common mode of failure is progression of arthritis throughout the knee, in some series as high as 25% at 15 years. Aseptic loosening, particularly of cemented implants, is less common. Infection is an uncommon long-term complication. Patients considering PFA should be advised of the risk of arthritis progression. Many authors routinely obtain a preoperative MRI to assess the status of the tibiofemoral compartments.

Question 1319

Topic: 3. Adult Reconstruction (Hip & Knee)
Figure 10 is the radiograph of a 44-year-old man with a long-standing history of severe hip pain and a limp. Which clinical scenario most likely could occur when performing total hip arthroplasty on this patient?
. Placing the hip center too inferior
. Overmedializing the acetabular component
. Overlengthening the extremity
. Intrasurgical acetabular fracture

Correct Answer & Explanation

. Overlengthening the extremity

Explanation

The radiograph reveals hip dysplasia. Patients with hip dysplasia and severe limb shortening are at high risk for sciatic nerve palsy from overlengthening. Overmedializing the acetabular component is not the preferred response because overlateralization is more of a concern if the cup is placed in the pseudoacetabulum instead of in the true acetabulum. Placing the hip center too inferior is not the preferred response because the concern in this scenario is placing the hip center too superior if the cup is placed in the pseudoacetabulum or if a large-diameter cup is used. Acetabular fractures are possible because of osteoporotic bone at the true hip center, but is less likely than overlengthening of the extremity.

Question 1320

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old woman underwent a primary total hip arthroplasty 14 months ago. She states that the hip has now dislocated four times when rising from a low chair, requiring closed reduction. A radiograph is shown in Figure 3a and a CT scan of her pelvis is shown in Figure 3b. What is the most reliable method for rectifying her instability?
. Use of an abduction orthosis for 6 weeks
. Modular exchange of the femoral head to a 36-mm head and a longer neck
. Modular exchange of the polyethylene liner to a constrained acetabular insert
. Revision and repositioning of the acetabular component and use of a 36-mm femoral head
. A physical therapy program stressing abductor strengthening

Correct Answer & Explanation

. Revision and repositioning of the acetabular component and use of a 36-mm femoral head

Explanation

The radiograph shows well-fixed components without evidence of loosening. The CT scan shows severe retroversion of the acetabular component. Revision of the component into the correct amount of anteversion will most reliably rectify the instability in the face of severe component malposition.

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