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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 326 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 6501

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision total knee arthroplasty, the joint line is inadvertently elevated by 10 mm. Which of the following kinematic changes or clinical complications is most likely to occur as a direct result of this alteration?

. Increased patellar instability and mid-flexion instability
. Decreased tension on the posterior cruciate ligament in flexion
. Patella alta with secondary quadriceps tendon impingement
. Paradoxical anterior femoral roll-back during deep flexion
. Decreased reliance on the medial collateral ligament for coronal stability

Correct Answer & Explanation

. Increased patellar instability and mid-flexion instability

Explanation

Elevating the joint line alters patellofemoral mechanics by creating a pseudo-patella baja, leading to increased contact stresses and patellar instability. It also alters collateral ligament isometry, frequently resulting in mid-flexion coronal instability.

Question 6502

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male presents for a total knee arthroplasty five years after undergoing a medial opening-wedge high tibial osteotomy (HTO). Which of the following technical challenges is most frequently encountered during TKA in this specific patient population compared to primary TKA in a patient without prior surgery?

. Excessive tibial plateau external rotation
. Patella alta requiring distalization of the tibial tubercle
. Increased posterior tibial slope requiring compensatory bone resection
. Medial soft tissue laxity necessitating a constrained insert
. Sclerotic lateral tibial bone requiring specialized reamers

Correct Answer & Explanation

. Increased posterior tibial slope requiring compensatory bone resection

Explanation

A medial opening-wedge HTO inherently increases the posterior tibial slope and often results in patella baja. During a subsequent TKA, the surgeon must correct this exaggerated slope, typically requiring more extensive bone resection from the posterior aspect of the proximal tibia.

Question 6503

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty in a patient with a severe, fixed valgus deformity, the extension gap remains tight laterally, while the flexion gap is well-balanced. Which of the following structures is the primary tether causing the lateral tightness specifically in extension, and should be the initial target for release?

. Popliteus tendon
. Lateral collateral ligament
. Iliotibial band
. Anterior cruciate ligament
. Posterior oblique ligament

Correct Answer & Explanation

. Iliotibial band

Explanation

In a valgus knee, the iliotibial band is a major lateral deforming force that becomes notably tight in extension but relaxes in flexion. The popliteus tendon and lateral collateral ligament are primarily responsible for lateral tightness in flexion.

Question 6504

Topic: 3. Adult Reconstruction (Hip & Knee)

A 28-year-old male presents with a transverse fracture of the femur after a minor fall. He has a history of frequent fractures, short stature, and delayed tooth eruption. Examination reveals an obtuse mandibular angle and short distal phalanges. Radiographs show generalized osteosclerosis, open cranial sutures, and acro-osteolysis of the distal phalanges. What is the mutated enzyme in this condition?

. Carbonic Anhydrase II
. Alkaline Phosphatase
. Iduronate-2-sulfatase
. Cathepsin K
. Tartrate-resistant acid phosphatase

Correct Answer & Explanation

. Cathepsin K

Explanation

The patient has pycnodysostosis, an autosomal recessive lysosomal storage disease caused by a Cathepsin K mutation. Classic features include dense bones, open cranial sutures, obtuse mandibular angle, and acro-osteolysis, distinguishing it from osteopetrosis and cleidocranial dysplasia.

Question 6505

Topic: 3. Adult Reconstruction (Hip & Knee)

A 25-year-old male presents with recurrent stress fractures of the anterior tibia. He has disproportionate short stature, a prominent forehead, and an obtuse mandibular angle. Radiographs show generalized osteosclerosis and acro-osteolysis of the distal phalanges. Which enzyme is primarily deficient in this patient?

. Cathepsin K
. Tissue-nonspecific alkaline phosphatase
. Glucocerebrosidase
. Carbonic anhydrase II
. Lysyl hydroxylase

Correct Answer & Explanation

. Cathepsin K

Explanation

Pycnodysostosis is an autosomal recessive disorder caused by a deficiency in cathepsin K, which is essential for osteoclast-mediated bone matrix degradation. Clinical hallmarks include acro-osteolysis, delayed cranial suture closure, and obtuse mandibular angles with dense, brittle bones.

Question 6506

Topic: 3. Adult Reconstruction (Hip & Knee)
A 28-year-old male sustains a transverse subtrochanteric femur fracture after a minor fall. He is remarkably short in stature with a prominent forehead and short, stubby fingers with dysplastic nails. Radiographs show generalized osteosclerosis, open cranial sutures, and complete acro-osteolysis of the distal phalanges. A deficiency in which enzyme is responsible for his underlying bone disease?
. Carbonic anhydrase II
. Cathepsin K
. Alkaline phosphatase
. Glucocerebrosidase
. Tissue-nonspecific alkaline phosphatase (TNSALP)

Correct Answer & Explanation

. Cathepsin K

Explanation

Pycnodysostosis is an autosomal recessive disorder caused by a deficiency of Cathepsin K, which impairs osteoclast degradation of organic bone matrix. It is distinguished from other osteopetrotic conditions by the presence of delayed cranial suture closure, dysplastic nails, and pathognomonic acro-osteolysis.

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