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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 77 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 1521

Topic: 3. Adult Reconstruction (Hip & Knee)
A woman is scheduled to undergo right total hip arthroplasty. Her preoperative radiograph is shown below. To avoid increasing this patient’s combined offset while maintaining her leg length, what is the most appropriate surgical plan?
. Lateralize the acetabular component, use a low offset femoral component, and make a shorter neck cut
. Medialize the acetabular component, use a low offset femoral component, and make a longer neck cut
. Lateralize the acetabular component, use a high offset femoral component, and make a shorter neck cut
. Medialize the acetabular component, use a high offset femoral component, and make a longer neck cut

Correct Answer & Explanation

. Medialize the acetabular component, use a low offset femoral component, and make a longer neck cut

Explanation

The management of patients with proximal femoral deformity can be difficult. Appropriate implant selection and preoperative templating are critical. In this patient, it would be difficult to avoid increasing the combined offset by too much, which could contribute to the overtensioning of the soft tissues and trochanteric pain. By medializing the acetabular component (decreasing the combined offset), using a low offset femoral component or a cemented component placed more valgus (decreasing the combined offset), and making a longer neck cut (to avoid shortening of the lower extremity), restoration of the patient’s native offset and leg length can be achieved.

Question 1522

Topic: 3. Adult Reconstruction (Hip & Knee)
A 62-year-old patient is seen for routine follow-up after undergoing cementless total hip arthroplasty 2 years ago. The patient reports limited range of motion that severely affects daily activities. A radiograph is shown in Figure 51. Management should now consist of
. observation only.
. nonsteroidal anti-inflammatory drugs and protected weight bearing.
. irradiation to the affected area.
. surgical excision.
. surgical excision and postoperative irradiation.

Correct Answer & Explanation

. surgical excision and postoperative irradiation.

Explanation

DISCUSSION: The patient has symptomatic postoperative heterotopic ossification after total hip arthroplasty. Postoperative prophylactic treatments include nonsteroidal anti-inflammatory drugs (usually indomethacin) or low-dose irradiation. The heterotopic ossification shown here is quite mature; therefore, nonsurgical management will not be successful. Surgical excision of grade III or IV heterotopic ossification should be followed with postoperative irradiation to minimize the chances of recurrence. REFERENCES: Ayers DC, Evarts CM, Parkinson JR: The prevention of heterotopic ossification in high-risk patients by low-dose radiation therapy after total hip arthroplasty. J Bone Joint Surg Am 1986;68:1423-1430. Healy WL, Lo TC, DeSimone AA, et al: Single-dose irradiation for the prevention of heterotopic ossification after total hip arthroplasty: A comparison of doses of five hundred and fifty and seven hundred centigray. J Bone Joint Surg Am 1995;77:590-595.

Question 1523

Topic: 3. Adult Reconstruction (Hip & Knee)

Lymphangioma

. Pseudotumor
. A pseudotumor is a hemophilic subperiosteal hematoma. The pseudotumor expands by repeated bleeds and increasing osmotic pressure.
. There was no periosteal reaction or intralesional calcification. The bone wall itself is not expanded as in aneurysmal bone cyst.
. There is nothing in the physical examination or patient history to point to infection.

Correct Answer & Explanation

. A pseudotumor is a hemophilic subperiosteal hematoma. The pseudotumor expands by repeated bleeds and increasing osmotic pressure.

Explanation

In classic hemophilia, a natural factor-VIII level of less than what percentage will lead to severe bleeding and complications:

Question 1524

Topic: 3. Adult Reconstruction (Hip & Knee)
According to Musculoskeletal Infection Society (MSIS) guidelines, which set of patient laboratory study results fits the definition of chronic prosthetic joint infection?
. Erythrocyte sedimentation rate (ESR) 50 mm/hr, C-reactive protein (CRP) 8 mg/L, joint aspiration white blood cell (WBC) count 542, 62% neutrophils, and positive leukocyte esterase
. ESR 42 mm/hr, CRP 12 mg/L, joint aspiration WBC count 3,540, 72% neutrophils, and positive leukocyte esterase
. ESR 20 mm/hr, CRP 15 mg/L, joint aspiration WBC count 4,135, 54% neutrophils, and negative leukocyte esterase
. ESR 25 mm/hr, CRP 7 mg/L, joint aspiration WBC count 252, 82% neutrophils, and negative leukocyte esterase

Correct Answer & Explanation

. ESR 42 mm/hr, CRP 12 mg/L, joint aspiration WBC count 3,540, 72% neutrophils, and positive leukocyte esterase

Explanation

DISCUSSION: The MSIS definition of periprosthetic joint infection was updated in 2014 with two major and six minor criteria. The presence of one major criterion or three minor criteria is diagnostic for infection. The major criteria are two positive cultures with the same organism or a draining sinus tract. The current MSIS minor criteria are 1) an elevated ESR (more than 30 mm/hr) and CRP level (more than 10 mg/L), 2) an elevated synovial WBC count (more than 3,000 cells/microliter), 3) an elevated synovial fluid polymorphonuclear count (more than 80%), 4) a positive histological analysis of periprosthetic tissue, and 5) a single positive culture.

Question 1525

Topic: 3. Adult Reconstruction (Hip & Knee)
A 52-year-old man with a BMI of 40 and primary osteoarthritis undergoes total hip arthroplasty through a posterolateral approach. To retract the femur anteriorly when exposing the acetabulum, the surgeon places a sharp curved retractor over (anterior to) the anterior inferior iliac spine. Pulsatile bleeding is encountered. A branch of which artery has been injured?
. Medial femoral circumflex
. Obturator
. Iliac circumflex
. Femoral

Correct Answer & Explanation

. Femoral

Explanation

DISCUSSION: The femoral artery crosses the hip joint anterior to the anterior hip capsule. The medial femoral circumflex artery enters the joint along the route of the obturator externus. The obturator artery enters the hip joint beneath the transverse acetabular ligament. The iliac circumflex vessel arises superior to the hip joint.

Question 1526

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, increasing the perpendicular distance from the center line of the femur to the center of rotation of the femoral head (femoral offset) results in

. decreased tissue tension
. decreased abductor lever arm
. decreased joint reaction force
. increased body weight over lever arm
. increased polyethylene wear rate

Correct Answer & Explanation

. decreased joint reaction force

Explanation

The advantages to increasing femoral offset at THA are reported toinclude an increased range of motion, better mechanical advantage for the abductors and decreased instability because of better soft tissue tension. According to Charnley,increasing the femoral offset should improve the abductor lever arm which should decrease the abductor force required for walking, and therefore decrease the energy requirement for gait as well as the overall joint reactive force. The largest possible disadvantage of increasing the femoral offset is increasing the out of plane bending moment which puts stress on the prosthetic stem. Poly wear is a direct effect of surface area contact which is not changed with femoral Offset.

Question 1527

Topic: 3. Adult Reconstruction (Hip & Knee)
The figure below shows the radiograph obtained from a 76-year-old woman who has sharp pain in her groin, thigh, and buttocks that worsens with activity. She has been dealing with this pain for more than a year but is otherwise healthy. Recently, she has begun to notice night pain. The pain no longer responds to NSAIDs. She would like to be able to dance at her daughter's wedding in 4 months and wonders how best to proceed. What is the best next step?
. Radiograph-guided steroid injection followed by total hip arthroplasty 6 weeks later
. Total hip arthroplasty
. Physical therapy
. Referral back to her spine surgeon

Correct Answer & Explanation

. Total hip arthroplasty

Explanation

The next best course of action is total hip arthroplasty. The patient is an otherwise healthy woman requesting pain relief and expresses a desire to be dancing in 4 months. She has had more than 6 months of symptoms that are classic hip osteoarthritis symptoms, with pain in the groin and thigh. Severe osteoarthritis is seen in the radiograph as well. NSAIDs are no longer working. Given the objective findings, the subjective reports, and the duration of symptoms, this patient merits surgery. Consideration for steroid injection is reasonable, but given her desire to be dancing in 4 months, an injection would increase her risk of infection if total hip arthroplasty were to be performed within 3 months of the injection.

Question 1528

Topic: 3. Adult Reconstruction (Hip & Knee)
What is the most common cause of mechanical failure of an orthopaedic biomaterial during clinical use?
. Fatigue
. Tension
. Compression
. Shear
. Torsion

Correct Answer & Explanation

. Fatigue

Explanation

In most orthopaedic applications, the materials are strong enough to withstand a single cycle of loading in vivo. However, these loads may be large enough to initiate a small crack in the implant that can grow slowly over thousands or millions of cycles, eventually leading to gross failure. Such fatigue failure has occurred with virtually every type of implant, including stainless steel fracture plates and screws, bone cement in joint arthroplasty, and polyethylene inserts in total knee arthroplasty.

Question 1529

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with severe groin pain and swelling 8 years after a metal-on-metal total hip arthroplasty. Imaging demonstrates a large cystic mass compressing the femoral vein. Blood cobalt and chromium levels are markedly elevated. Aspiration yields fluid negative for infection. What is the most appropriate definitive management for this patient?

. CT-guided aspiration of the cyst and observation
. Revision of the acetabular and/or femoral components to a ceramic-on-polyethylene bearing with extensive synovectomy
. Isolated head and liner exchange to a metal-on-polyethylene bearing
. Prescription of oral metal chelators and physical therapy
. Intra-articular corticosteroid injection

Correct Answer & Explanation

. CT-guided aspiration of the cyst and observation

Explanation

This patient has an adverse local tissue reaction (ALTR) or pseudotumor secondary to a metal-on-metal bearing. The definitive treatment for a symptomatic pseudotumor with elevated metal ions and a negative infection workup is revision arthroplasty to a non-metal-on-metal bearing (such as ceramic-on-polyethylene) combined with an extensive synovectomy to remove all necrotic and metallotic tissue.

Question 1530

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female complains of knee swelling and a sense of instability when rising from a chair or descending stairs 1 year after a primary posterior-stabilized total knee arthroplasty. On physical examination, she lacks varus or valgus laxity in full extension, but demonstrates a positive anterior and posterior drawer test when the knee is flexed to 90 degrees. Radiographs show well-fixed components with no evidence of loosening. What is the most likely technical error leading to this complication?

. Undersizing the anteroposterior dimension of the femoral component
. Excessive distal femoral resection
. Oversizing the tibial component
. Inadequate release of the posterior cruciate ligament
. Use of an excessively thick polyethylene insert

Correct Answer & Explanation

. Undersizing the anteroposterior dimension of the femoral component

Explanation

The patient's presentation of instability specifically in flexion (with stability in extension) is classic for isolated flexion instability. This typically occurs when the flexion gap is disproportionately larger than the extension gap. The most common technical error causing this is undersizing the anteroposterior (AP) dimension of the femoral component, which results in an excessive flexion gap. Excessive distal femoral resection would increase the extension gap, leading to extension instability.

Question 1531

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with recurrent posterior dislocations of her primary total hip arthroplasty. CT evaluation demonstrates the acetabular component is positioned in 10 degrees of anteversion and 35 degrees of abduction. The uncemented femoral component is fixed in 5 degrees of retroversion. What is the most appropriate surgical strategy to restore stability?

. Revise the components to increase both acetabular and femoral anteversion
. Revise the components to decrease acetabular anteversion and decrease femoral anteversion
. Increase acetabular abduction only
. Exchange the modular head to a larger diameter without revising the stem or cup
. Convert to a constrained liner while maintaining the current acetabular shell position

Correct Answer & Explanation

. Revise the components to increase both acetabular and femoral anteversion

Explanation

Combined anteversion (the sum of acetabular anteversion and femoral anteversion) is critical for hip stability. The widely accepted safe zone for combined anteversion is between 25 and 45 degrees. In this patient, the combined anteversion is 10 + (-5) = 5 degrees, which places her at high risk for posterior dislocation due to excessive retroversion of the overall construct. The correct strategy is to increase both acetabular and femoral anteversion (e.g., via revision) to achieve proper combined anteversion.

Question 1532

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female undergoes a total ankle arthroplasty via a standard anterior approach. Three months postoperatively, she reports numbness over the dorsum of her foot. During the surgical exposure, the extensor digitorum longus (EDL) was retracted laterally. Which cutaneous nerve was most likely injured or stretched during this dissection?

. Deep peroneal nerve
. Superficial peroneal nerve
. Sural nerve
. Saphenous nerve
. Medial plantar nerve

Correct Answer & Explanation

. Deep peroneal nerve

Explanation

The superficial peroneal nerve (specifically its intermediate dorsal cutaneous branch) frequently crosses the anterior surgical field from lateral to medial and is at high risk of injury during the anterior approach to the ankle. It is typically identified and retracted laterally with the extensor digitorum longus. The deep peroneal nerve lies deep to the extensor retinaculum between the extensor hallucis longus and tibialis anterior.

Question 1533

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male who underwent a posterior-stabilized total knee arthroplasty 8 months ago complains of a catching sensation and an audible 'clunk' at the superior pole of the patella as his knee extends from 40 degrees to 30 degrees of flexion. Which specific implant design characteristic is most strongly associated with the development of this condition?

. A high patellar component placement
. Excessive posterior translation of the femoral component
. A high intercondylar box ratio with a sharp anterior margin
. Medialization of the tibial tray
. Use of a highly cross-linked all-polyethylene patellar button

Correct Answer & Explanation

. A high patellar component placement

Explanation

Patellar clunk syndrome is most commonly associated with posterior-stabilized total knee arthroplasty designs. It occurs when a fibrotic nodule forms at the quadriceps tendon just proximal to the patellar pole, which then catches within the intercondylar box of the femoral component during extension. It is heavily associated with older PS implant designs that feature a high intercondylar box ratio and a sharp superior/anterior margin of the box.

Question 1534

Topic: 3. Adult Reconstruction (Hip & Knee)

During preparation of the proximal femur for an uncemented, tapered-wedge total hip arthroplasty stem, the surgeon notes a non-displaced longitudinal fracture of the calcar propagating 2 cm distal to the lesser trochanter. The broach remains axially and rotationally stable within the canal. What is the most appropriate next step in management?

. Leave the broach in place, apply cerclage wires around the proximal femur, and proceed with the uncemented stem
. Bypass the fracture by revising to a fully porous-coated cylindrical diaphyseal stem
. Abandon the uncemented plan and switch to a cemented femoral stem
. Proceed with the insertion of the planned uncemented stem without any additional fixation
. Remove the broach, apply a locking plate to the proximal femur, and use a cemented stem

Correct Answer & Explanation

. Leave the broach in place, apply cerclage wires around the proximal femur, and proceed with the uncemented stem

Explanation

Intraoperative non-displaced calcar fractures during broaching for an uncemented stem are a known complication. If the fracture is recognized early, non-displaced, and the broach achieves excellent stability, the standard of care is to place prophylactic cerclage wires around the proximal femur (to prevent propagation during final stem impaction) and proceed with the planned uncemented stem.

Question 1535

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with an inability to perform a straight leg raise 3 years after a primary total knee arthroplasty. Imaging demonstrates patella alta and a palpable defect at the tibial tubercle. An extensor mechanism allograft reconstruction is planned. To maximize the likelihood of a successful outcome, at what degree of knee flexion should the allograft be tensioned and fixed?

. In full extension (0 degrees) with maximal tension
. At 30 degrees of flexion to allow for a physiologic 'J-sign'
. At 60 degrees of flexion to prevent patella baja
. At 90 degrees of flexion to ensure adequate postoperative range of motion
. At 120 degrees of flexion to accommodate high-flex activities

Correct Answer & Explanation

. In full extension (0 degrees) with maximal tension

Explanation

When performing an extensor mechanism allograft reconstruction for a disruption following TKA, it is critical to tension the allograft tightly in full extension (0 degrees). Postoperative stretching and attenuation of the allograft are nearly universal, and tensioning in any degree of flexion will inevitably lead to an extensor lag and clinical failure.

Question 1536

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following is considered a definitive major criterion for diagnosing a periprosthetic joint infection?

. Synovial fluid white blood cell count greater than 3,000 cells/µL
. A single positive intraoperative tissue culture
. A sinus tract communicating directly with the joint
. Elevated serum C-reactive protein (CRP) > 10 mg/L and D-dimer
. A positive synovial fluid alpha-defensin immunoassay

Correct Answer & Explanation

. Synovial fluid white blood cell count greater than 3,000 cells/µL

Explanation

The 2018 MSIS/ICM criteria define a periprosthetic joint infection definitively if either of two major criteria are met: (1) A sinus tract communicating with the joint, or (2) Two positive periprosthetic cultures with phenotypically identical organisms. The other options (elevated synovial WBC, positive alpha-defensin, single positive culture, elevated CRP) represent minor criteria that must be combined to generate a diagnostic score.

Question 1537

Topic: 3. Adult Reconstruction (Hip & Knee)

During the medial release of a primary total knee arthroplasty for a varus deformity, the surgeon inadvertently transects the mid-substance of the medial collateral ligament (MCL). The bone cuts have been made, but the components have not yet been implanted. What is the most appropriate intraoperative management strategy?

. Proceed with a standard unconstrained posterior-stabilized implant and prescribe a hinged knee brace postoperatively
. Harvest a hamstring autograft for anatomic MCL reconstruction and utilize a cruciate-retaining implant
. Perform a primary end-to-end repair of the MCL and implant a constrained condylar knee (CCK) prosthesis
. Implant a rotating-hinge knee prosthesis and leave the MCL unrepaired
. Convert the procedure to a knee arthrodesis

Correct Answer & Explanation

. Proceed with a standard unconstrained posterior-stabilized implant and prescribe a hinged knee brace postoperatively

Explanation

An iatrogenic mid-substance transection of the MCL during TKA requires direct repair. Because the repair alone is insufficient to withstand the coronal plane forces during the healing phase, the construct must be protected by increasing the coronal constraint of the implant. A constrained condylar knee (CCK) prosthesis provides the necessary varus/valgus stability to protect the MCL repair without resorting to the excessive constraint and bone resection of a rotating-hinge device, which is usually reserved for massive bone loss or completely deficient/unrepairable collateral ligaments.

Question 1538

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male with a metal-on-polyethylene total hip arthroplasty presents with new-onset groin pain and swelling 7 years postoperatively.

Radiographs show a well-fixed stem and cup. Serum cobalt is 8.5 ppb and chromium is 1.2 ppb. MRI with metal artifact reduction shows a solid pseudotumor. What is the most likely source of the elevated metal ions?

. Abrasive wear at the bearing surface
. Mechanically assisted crevice corrosion at the head-neck junction
. Impingement of the femoral neck on the acetabular rim
. Third-body wear from broken cement particles
. Galvanic corrosion at the stem-cement interface

Correct Answer & Explanation

. Abrasive wear at the bearing surface

Explanation

In a metal-on-polyethylene THA, elevated cobalt levels that are disproportionately higher than chromium levels are highly indicative of trunnionosis, which is mechanically assisted crevice corrosion and fretting at the modular head-neck taper junction. Because the bearing surface is metal articulating with polyethylene, bearing wear would not produce significant metal ions, but taper corrosion releases massive amounts of cobalt.

Question 1539

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the trial reduction reveals that the knee is symmetric and stable in full extension, but excessively tight in 90 degrees of flexion, preventing full range of motion. Which of the following surgical adjustments will most effectively correct this specific imbalance?

. Downsize the femoral component using an anterior referencing system
. Resect more distal femur
. Increase the thickness of the tibial polyethylene insert
. Release the posterior knee capsule
. Upsize the femoral component using a posterior referencing system

Correct Answer & Explanation

. Downsize the femoral component using an anterior referencing system

Explanation

A knee that is stable in extension but tight in flexion has an isolated tight flexion gap. To increase the flexion gap without altering the extension gap, the surgeon must reduce the posterior condylar offset. This is accomplished by downsizing the femoral component. If an anterior referencing system is used, downsizing reduces the posterior condyles and opens the flexion gap. Resecting more distal femur or releasing the posterior capsule would affect the extension gap.

Question 1540

Topic: 3. Adult Reconstruction (Hip & Knee)

Following a primary total hip arthroplasty performed via a standard posterolateral approach, patients are commonly instructed on 'hip precautions.' Which specific combination of hip movements places the joint at the greatest risk for a posterior dislocation?

. Hip extension, abduction, and external rotation
. Hip flexion, adduction, and internal rotation
. Hip flexion, abduction, and external rotation
. Hip extension, adduction, and internal rotation
. Hip neutral flexion, abduction, and internal rotation

Correct Answer & Explanation

. Hip extension, abduction, and external rotation

Explanation

The posterolateral approach involves dissecting through the posterior capsule and external rotators. Until these structures heal, the hip is most vulnerable to posterior dislocation when the femoral head is driven posteriorly against the weakened capsule. This occurs with a combined mechanism of extreme hip flexion, adduction across the midline, and internal rotation (e.g., crossing the legs while sitting low).

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