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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 65 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 1281

Topic: Total Hip Arthroplasty (THA)
A 68-year-old male requires a revision total hip arthroplasty for a loose femoral stem. Radiographs demonstrate a Paprosky Type IIIB femoral defect. Which of the following best defines a Type IIIB defect and indicates the most appropriate femoral implant choice?
. >4 cm of intact diaphyseal bone at the isthmus; use a fully porous-coated cylindrical stem.
. <4 cm of intact diaphyseal bone at the isthmus; use a modular fluted tapered stem.
. Complete loss of the femoral diaphysis to the supracondylar region; use a total femoral replacement.
. Intact metaphysis but an isolated greater trochanteric fracture; use a standard primary stem with a claw.
. Extensive metaphyseal bone loss with >4 cm diaphyseal fit available; use an impaction allograft reconstruction.

Correct Answer & Explanation

. <4 cm of intact diaphyseal bone at the isthmus; use a modular fluted tapered stem.

Explanation

In the Paprosky femoral defect classification, a Type IIIA defect has >4 cm of intact diaphyseal bone at the isthmus, allowing for reliable fixation with a fully porous-coated cylindrical stem. A Type IIIB defect has <4 cm of intact diaphysis, which is insufficient for cylindrical scratch fit. The standard of care for IIIB defects is a modular fluted tapered stem, which achieves rotational and axial stability in a shorter segment of distal bone.

Question 1282

Topic: 3. Adult Reconstruction (Hip & Knee)
A 74-year-old female presents for revision total hip arthroplasty due to aseptic loosening. Radiographs demonstrate severe femoral osteolysis. Intraoperatively, the diaphyseal isthmus is severely expanded, providing less than 3 cm of intact diaphyseal bone available for scratch fit. According to the Paprosky classification, what is the most appropriate femoral reconstructive option?
. Extensively porous-coated cylindrical stem
. Modular fluted tapered stem
. Standard length cemented stem
. Impaction bone grafting with a standard uncemented stem
. Standard length proximally coated cementless stem

Correct Answer & Explanation

. Modular fluted tapered stem

Explanation

This patient has a Paprosky Type IIIB femoral defect, defined by an unsupportive metaphysis and less than 4 cm of diaphyseal isthmus available for fixation. A modular fluted tapered stem is the workhorse for this defect as the flutes provide rotational stability and the taper achieves axial stability in the distal diaphyseal bone.

Question 1283

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a metal-on-polyethylene total hip arthroplasty presents with worsening groin pain 7 years postoperatively. Aspiration is negative for infection. A MARS MRI reveals a large cystic pseudotumor. Laboratory analysis demonstrates elevated serum cobalt levels with normal chromium levels. Which of the following is the most likely etiology?

. Polyethylene wear debris
. Mechanically assisted crevice corrosion at the head-neck junction
. Galvanic corrosion at the stem-sleeve junction
. Bearing surface wear from edge loading
. Unrecognized indolent periprosthetic joint infection

Correct Answer & Explanation

. Polyethylene wear debris

Explanation

In a metal-on-polyethylene THA, a pseudotumor (Adverse Local Tissue Reaction - ALTR) accompanied by an isolated elevation in cobalt relative to chromium strongly indicates mechanically assisted crevice corrosion (MACC), commonly known as trunnionosis, at the modular head-neck junction.

Question 1284

Topic: 3. Adult Reconstruction (Hip & Knee)
During a revision total hip arthroplasty, the surgeon encounters an acetabular defect with 4 cm of superior migration of the hip center. Kohler's line is intact, but there is greater than 40% loss of the superior rim. A jumbo cup lacks adequate superior coverage and stability. What is the most appropriate reconstructive strategy?
. High hip center with a standard uncemented cup
. Uncemented highly porous hemispherical cup with a superior porous metal augment
. Antiprotrusio cage with a cemented cup
. Impaction bone grafting with a cemented cup
. Custom triflange acetabular component

Correct Answer & Explanation

. Uncemented highly porous hemispherical cup with a superior porous metal augment

Explanation

This is a Paprosky Type IIIA acetabular defect ('up and out', intact Kohler's line, >30% superior rim loss). Because the supportive superior rim is deficient, a highly porous cup combined with a superior porous metal augment (or structural allograft) is indicated to restore the hip center, provide initial stability, and allow for biologic ingrowth.

Question 1285

Topic: Total Hip Arthroplasty (THA)

A 70-year-old male with a history of multiple revision total hip arthroplasties presents with recurrent posterior dislocations. Intraoperative evaluation reveals that both the acetabular and femoral components are well-fixed and optimally aligned. However, the patient has profound and irreparable abductor deficiency. Assuming component modularity permits, what is the most reliable reconstructive option?

. Revision of the acetabular shell to increase anteversion
. Revision to a dual-mobility construct
. Revision to a constrained acetabular liner
. Proximal femoral osteotomy
. Trochanteric advancement

Correct Answer & Explanation

. Revision of the acetabular shell to increase anteversion

Explanation

In the setting of recurrent instability due to severe, unrepairable abductor deficiency with well-positioned and well-fixed components, a constrained acetabular liner is the most appropriate option. While dual-mobility constructs are excellent for instability, they rely on a functional dynamic soft-tissue envelope (abductors) and may still dislocate in profound abductor deficiency.

Question 1286

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male who underwent a total hip arthroplasty with a ceramic-on-ceramic bearing 3 years ago complains of a loud 'squeaking' noise when bending or rising from a chair. He denies pain, and standard radiographs appear unremarkable. Which of the following factors is the most significant contributor to this phenomenon?

. Acetabular component malposition leading to edge loading
. Decreased femoral head size
. Small clearance between the head and liner
. High body mass index
. Use of a titanium alloy stem instead of cobalt-chromium

Correct Answer & Explanation

. Acetabular component malposition leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic THA is most commonly associated with edge loading of the bearing surfaces. Edge loading typically results from component malposition (e.g., a steeply inclined or excessively anteverted/retroverted acetabular cup), which causes loss of fluid film lubrication and highly concentrated focal stress.

Question 1287

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male is evaluated for a painful THA 2 years postoperatively. Synovial fluid aspiration reveals a WBC count of 2,800 cells/ยตL and 60% polymorphonuclear neutrophils. To aid in confirming a periprosthetic joint infection based on the 2018 ICM criteria, which of the following synovial fluid biomarkers provides the highest specificity?

. Interleukin-6 (IL-6)
. Procalcitonin
. Alpha-defensin
. C-reactive protein (CRP)
. Tumor necrosis factor alpha (TNF-a)

Correct Answer & Explanation

. Interleukin-6 (IL-6)

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils that has exceptionally high sensitivity and specificity (often >95%) for diagnosing periprosthetic joint infection (PJI). It is included in the 2018 International Consensus Meeting (ICM) criteria as a heavily weighted biomarker for diagnosing PJI.

Question 1288

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex revision THA to remove a well-fixed cementless stem, the surgeon performs an Extended Trochanteric Osteotomy (ETO). To preserve the primary vascular supply to the osteotomized fragment and minimize the risk of necrosis or nonunion, which of the following muscle attachments must be preserved distally?

. Vastus intermedius
. Vastus lateralis
. Gluteus maximus
. Rectus femoris
. Iliopsoas

Correct Answer & Explanation

. Vastus intermedius

Explanation

The Extended Trochanteric Osteotomy (ETO) fragment depends on the maintenance of its soft-tissue pedicle for vascularity. Proximally, the gluteus medius and minimus attachments are maintained, while distally, the vastus lateralis attachment must be preserved to ensure blood supply and distal stability of the fragment.

Question 1289

Topic: Total Hip Arthroplasty (THA)

Following insertion of trial components during a primary THA, the hip is stable. However, intraoperative measurement shows the operated leg is 15 mm longer than the contralateral side, and the global offset is 5 mm less than desired. Which of the following component adjustments will most effectively restore equal leg length while simultaneously increasing global offset?

. Use a shorter femoral head with a longer neck modularity
. Use a high-offset femoral stem combined with a shorter neck modularity
. Increase the acetabular cup size to achieve more medialization
. Change to a standard offset stem with a longer neck
. Use a lateralized acetabular liner with a standard femoral head

Correct Answer & Explanation

. Use a shorter femoral head with a longer neck modularity

Explanation

To correct an overly long leg, the neck length must be decreased (e.g., using a shorter modular head). However, this alone would further decrease offset. Changing from a standard stem to a high-offset stem increases offset independently of leg length. Therefore, using a high-offset stem with a shorter modular neck/head corrects both problems: it reduces leg length while maintaining or increasing the offset.

Question 1290

Topic: Total Hip Arthroplasty (THA)

When utilizing a polished, collarless, taper-slip cemented femoral stem during a primary THA, which of the following biomechanical principles governs its fundamental design and function?

. It is designed to achieve rigid chemical bonding to the polymethylmethacrylate (PMMA) mantle
. It relies on macro-interlock with the cement mantle to resist subsidence
. It subsides within the cement mantle to increase radial compressive forces (hoop stresses)
. It acts strictly as a composite beam with the cement to transfer stress proximally
. It requires a structural collar to prevent distal migration and excessive hoop stresses

Correct Answer & Explanation

. It is designed to achieve rigid chemical bonding to the polymethylmethacrylate (PMMA) mantle

Explanation

Polished, collarless, taper-slip stems (e.g., Exeter) are designed to subside slightly ('slip') within the cement mantle under axial loading. Because they are tapered, this subsidence wedges the stem into the cement, converting axial loads into radial compressive forces (hoop stresses) that strengthen the construct. They do not bond to the cement, unlike composite-beam stems.

Question 1291

Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female presents with a loose total hip arthroplasty. Radiographs show superior migration of the hip center by 3.5 cm and medial migration past Kohler's line into the pelvis. There is massive osteolysis of the ischium and the teardrop is obliterated. According to the Paprosky acetabular defect classification, what is the most likely defect type and the recommended reconstruction strategy?
. Type IIIA; reconstruction with a jumbo cup and multi-hole screws.
. Type IIIB; reconstruction with a custom triflange or cup-cage construct.
. Type IIIC; reconstruction with an extended trochanteric osteotomy.
. Type IIB; reconstruction with impaction bone grafting and a cemented cup.
. Type IIC; reconstruction with a high hip center utilizing a standard hemispherical cup.

Correct Answer & Explanation

. Type IIIB; reconstruction with a custom triflange or cup-cage construct.

Explanation

This patient has a Paprosky Type IIIB acetabular defect. Type IIIB is characterized by severe superomedial migration of the hip center (>3 cm superiorly) and medial to Kohler's line, with destruction of the teardrop and severe ischial lysis. Because less than 40% of the host bone is available for contact, standard hemispherical cups (even jumbo) fail to achieve stability. Advanced reconstruction techniques such as custom triflange components, cup-cage constructs, or massive structural allografts are required to bridge the defect and achieve fixation.

Question 1292

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old male sustains a periprosthetic femur fracture around a cemented total hip arthroplasty following a low-energy fall. Radiographs show a fracture at the tip of the stem. The stem demonstrates gross subsidence, but the proximal and distal diaphyseal bone stock remains thick and structurally sound. According to the Vancouver classification, what is the appropriate treatment?

. Open reduction internal fixation (ORIF) with a lateral locking plate and cerclage cables.
. Revision to a fully porous-coated long uncemented stem bypassing the distal fracture line by at least two cortical diameters.
. Revision utilizing a proximal femoral replacement (megaprosthesis).
. Removal of the implant, fracture fixation, and application of a static antibiotic spacer.
. Revision to a short, highly porous-coated metaphyseal fitting stem.

Correct Answer & Explanation

. Revision to a fully porous-coated long uncemented stem bypassing the distal fracture line by at least two cortical diameters.

Explanation

This is a Vancouver B2 periprosthetic fracture. The fracture is around or just below the tip of the stem (Type B), the stem is loose (2), but the bone stock is of good quality. The standard of care for a B2 fracture is revision arthroplasty utilizing a long uncemented stem (often fluted/tapered or fully porous-coated) that bypasses the most distal fracture line by at least two cortical diameters to ensure adequate diaphyseal fixation, supplemented with cerclage wiring or plating of the fracture.

Question 1293

Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain and a palpable anterior mass. MRI with metal artifact reduction sequence (MARS) reveals a large, cystic periarticular lesion. Histological analysis of the periprosthetic tissue is most likely to demonstrate which of the following primary immune responses?
. Type I immediate hypersensitivity with extensive eosinophilic infiltration.
. Type II cytotoxic hypersensitivity with antibody-dependent cellular cytotoxicity.
. Type III immune-complex hypersensitivity with widespread fibrinoid necrosis.
. Type IV delayed hypersensitivity with perivascular lymphocytic infiltration.
. Innate foreign body response characterized primarily by polymorphonuclear leukocytes.

Correct Answer & Explanation

. Type IV delayed hypersensitivity with perivascular lymphocytic infiltration.

Explanation

The patient has an adverse local tissue reaction (ALTR) / aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL), commonly referred to as a 'pseudotumor' in the setting of a metal-on-metal THA. The pathophysiology is primarily a Type IV (delayed) hypersensitivity reaction to metal ions (cobalt and chromium). Histologically, this is characterized by a dense, perivascular infiltration of T-lymphocytes and macrophages, distinct from the innate macrophage-driven particulate disease seen in classic osteolysis.

Question 1294

Topic: Total Hip Arthroplasty (THA)

During a primary total hip arthroplasty via a posterior approach, the surgeon inadvertently utilizes a femoral component with significantly less offset than the patient's native anatomy, while maintaining equal leg lengths. Which of the following biomechanical consequences is most likely to occur?

. Increased abductor muscle mechanical advantage.
. Decreased joint reactive force across the hip articulation.
. Increased tension on the greater trochanteric musculature.
. Increased joint reactive force and an increased likelihood of impingement.
. Decreased varus bending moment on the femoral stem leading to lower risk of stem loosening.

Correct Answer & Explanation

. Increased joint reactive force and an increased likelihood of impingement.

Explanation

Decreasing the femoral offset brings the femur closer to the pelvis. This shortens the abductor lever arm, decreasing the mechanical advantage of the abductor muscles. To maintain a level pelvis during single-leg stance, the abductors must fire with significantly greater force, which in turn increases the total joint reactive force across the hip. Additionally, the decreased clearance between the femur and pelvis increases the risk of bony or soft tissue impingement, which can precipitate dislocation.

Question 1295

Topic: Total Hip Arthroplasty (THA)

A 62-year-old male with a metal-on-polyethylene (MoP) total hip arthroplasty (large cobalt-chromium head on a titanium stem) presents with new-onset hip pain 5 years post-operatively. Workup reveals a cystic mass and normal inflammatory markers. If mechanically assisted crevice corrosion (trunnionosis) is the primary pathology, serum metal ion testing will most likely demonstrate:

. Elevated titanium levels with undetectable cobalt and chromium.
. Markedly elevated chromium levels with normal cobalt.
. Markedly elevated cobalt levels with normal or slightly elevated chromium.
. Equally elevated levels of both cobalt and chromium.
. Undetectable metal ions, as trunnionosis only produces local tissue reactions.

Correct Answer & Explanation

. Markedly elevated cobalt levels with normal or slightly elevated chromium.

Explanation

In metal-on-polyethylene (MoP) THA utilizing a cobalt-chromium (CoCr) head on a titanium (Ti) alloy stem, mechanically assisted crevice corrosion can occur at the head-neck taper (trunnionosis). This specific galvanic and mechanical corrosion process preferentially releases cobalt over chromium. Therefore, serum analysis typically shows significantly elevated cobalt levels with normal or only slightly elevated chromium levels. This contrasts with wear in metal-on-metal (MoM) articulations, where both Co and Cr are typically elevated.

Question 1296

Topic: 3. Adult Reconstruction (Hip & Knee)

Alpha-defensin is an increasingly utilized biomarker for the diagnosis of periprosthetic joint infection (PJI) from synovial fluid aspirates. What is the precise biological origin and function of this molecule?

. An acute-phase reactant synthesized by the liver in response to IL-6.
. An antimicrobial peptide released primarily by activated neutrophils.
. A complement pathway protein that facilitates opsonization of staphylococci.
. A specific immunoglobulin secreted by B-lymphocytes in the synovial membrane.
. A proteolytic enzyme secreted by macrophages to degrade bacterial biofilms.

Correct Answer & Explanation

. An antimicrobial peptide released primarily by activated neutrophils.

Explanation

Alpha-defensins are small, cysteine-rich antimicrobial peptides that are primarily stored in the azurophilic granules of neutrophils. In response to infection, neutrophils degranulate and release alpha-defensins into the synovial fluid, where they insert into and disrupt bacterial cell membranes. Because its release is heavily tied to the massive neutrophil influx during a true bacterial infection, it is highly sensitive and specific for diagnosing PJI.

Question 1297

Topic: Total Hip Arthroplasty (THA)
A revision total hip arthroplasty is planned for a patient with a loose femoral stem. Preoperative templating and intraoperative findings demonstrate severe proximal bone loss with less than 3 cm of intact diaphyseal bone available for distal fixation. According to the Paprosky femoral defect classification, which of the following stem designs is most appropriate for reliable fixation?
. A fully porous-coated cylindrical non-modular stem.
. A cemented, polished, double-tapered collarless stem.
. A fluted, tapered, modular uncemented stem.
. A short metaphyseal-fitting proximally coated stem.
. A standard length, proximally porous-coated tapered wedge stem.

Correct Answer & Explanation

. A fluted, tapered, modular uncemented stem.

Explanation

This is a Paprosky Type IIIB femoral defect. It is characterized by severe proximal bone loss and an unsupported diaphysis with less than 4 cm of scratch fit available for a cylindrical stem. A fully porous-coated cylindrical stem (which requires at least 4 cm of intact diaphysis, i.e., Type IIIA) has a high failure rate in this setting. The treatment of choice for a Type IIIB defect is a fluted, tapered uncemented stem (often modular), which relies on a 3-point bending fit and axial splining rather than pure cylindrical diaphyseal scratch fit.

Question 1298

Topic: 3. Adult Reconstruction (Hip & Knee)

Femoral impaction bone grafting is a technique utilized in revision total hip arthroplasty for patients with severe cavitary femoral bone loss. To ensure appropriate initial stability and long-term graft incorporation via auto-compression, which type of femoral stem design is strictly required for this technique?

. A fully porous-coated cylindrical uncemented stem.
. A modular, fluted, tapered titanium stem.
. A proximally coated, proximally fixed hydroxyapatite stem.
. A collarless, polished, double-tapered cemented stem.
. A collared, matte-finished, straight cemented stem.

Correct Answer & Explanation

. A collarless, polished, double-tapered cemented stem.

Explanation

Femoral impaction bone grafting (e.g., the Exeter technique) involves tightly packing washed cancellous allograft chips into the femoral canal. A collarless, highly polished, double-tapered cemented stem must be used. The taper and lack of a collar allow the stem to act as a wedge, subsiding slightly within the cement mantle under physiological loading. This controlled subsidence converts axial loads into radial hoop stresses, auto-compressing the bone graft, which is essential for construct stability and long-term graft incorporation.

Question 1299

Topic: Total Hip Arthroplasty (THA)

During a complex revision THA requiring removal of a well-fixed porous-coated stem, the surgeon decides to perform an Extended Trochanteric Osteotomy (ETO). To optimize the probability of bony union of the osteotomized fragment, meticulous care is taken to preserve its vascular pedicle. The primary blood supply to the ETO fragment is maintained by the attachments of which of the following muscles?

. Gluteus medius and minimus.
. Tensor fasciae latae.
. Vastus lateralis.
. Quadratus femoris.
. Piriformis and superior gemellus.

Correct Answer & Explanation

. Vastus lateralis.

Explanation

The Extended Trochanteric Osteotomy (ETO) is a highly reliable technique for extraction of fixed femoral components. The osteotomy involves the greater trochanter and a lateral strut of the femoral diaphysis. To ensure healing, the vascular supply to the lateral diaphyseal bone must be preserved. This is primarily provided by the vastus lateralis muscle (which receives its blood supply from the descending branch of the lateral femoral circumflex artery). The gluteus medius provides some supply to the proximal tip, but the extensive diaphyseal portion relies on the vastus lateralis.

Question 1300

Topic: 3. Adult Reconstruction (Hip & Knee)

A 71-year-old male with highly active Paget's disease of the right hemipelvis and proximal femur requires a primary total hip arthroplasty due to severe secondary osteoarthritis. To minimize perioperative complications specific to the active phase of this disease, preoperative optimization with intravenous bisphosphonates is performed. This therapy is primarily intended to reduce the risk of which of the following intraoperative or early postoperative complications?

. Aseptic loosening secondary to poor initial bone ingrowth.
. Periprosthetic fracture due to increased bone brittleness.
. Excessive intraoperative hemorrhage.
. Postoperative sciatic nerve palsy from heterotopic ossification.
. Early deep periprosthetic joint infection.

Correct Answer & Explanation

. Excessive intraoperative hemorrhage.

Explanation

Paget's disease has three phases: osteolytic, mixed, and osteosclerotic. In the active (osteolytic/mixed) phase, the bone is highly vascular due to massive increases in osteoclastic and osteoblastic activity. Surgery during this hypervascular phase can result in profound, sometimes life-threatening intraoperative hemorrhage. Preoperative administration of bisphosphonates (or calcitonin) decreases disease activity, significantly reducing bone vascularity and thereby mitigating the risk of massive intraoperative bleeding.

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