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Arab Orthopaedic Board MCQs - Part 26

27 Apr 2026 87 min read 78 Views
Arab Ortho Board MCQs - Part 25

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For anyone wondering about Arab Orthopaedic Board MCQs - Part 26, Practice Arab Orthopaedic Board MCQs Part 26. Review orthopedic surgery questions 1251 to 1300 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 26

Comprehensive 100-Question Exam


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Question 1

A 35-year-old male presents with a closed pelvic ring injury after a motorcycle accident. Examination reveals a large, fluctuant, soft-tissue swelling over the greater trochanter. Aspiration yields serosanguinous fluid. What is the most appropriate management of this lesion to minimize infection risk prior to definitive pelvic fixation?





Explanation

The patient has a Morel-Lavallée lesion (closed degloving injury). These lesions are at high risk for infection if not addressed, especially if surgical incisions for fracture fixation are planned through or near the zone of injury. Large or established lesions are best managed by thorough open debridement and delayed primary closure or application of negative pressure wound therapy. Percutaneous aspiration alone has a high recurrence rate for large lesions and leaves necrotic fat in the dead space.

Question 2

A 12-year-old obese male presents with a 3-week history of left thigh pain and a limp. Examination shows obligatory external rotation of the hip with passive flexion. Radiographs demonstrate a mild slipped capital femoral epiphysis (SCFE). Which of the following is the most significant risk factor for developing chondrolysis in this patient?





Explanation

Chondrolysis is a devastating complication of SCFE characterized by rapid destruction of the articular cartilage. While it can occur in unpinned SCFE, the most strongly associated iatrogenic risk factor is unrecognized pin penetration into the joint space. Approach and pinning technique must include multi-planar fluoroscopy (the 'approach-withdraw' technique) to ensure the screw threads stay entirely within the femoral head.

Question 3

A 15-year-old female presents with distal femur pain. Imaging reveals a mixed lytic/sclerotic metaphyseal lesion with periosteal reaction. Biopsy confirms high-grade osteosarcoma. Which of the following histologic subtypes has the worst overall prognosis?





Explanation

Small cell osteosarcoma is a rare variant that typically has a worse prognosis than the conventional subtypes (osteoblastic, chondroblastic, fibroblastic) or telangiectatic osteosarcoma. It is often confused histologically with Ewing sarcoma but produces osteoid. Telangiectatic osteosarcoma has a similar or slightly better prognosis compared to conventional osteosarcoma when treated with modern chemotherapy protocols.

Question 4

A 65-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Six weeks postoperatively, she sustains a posterior dislocation while picking up an object from the floor. Closed reduction is successful. Plain radiographs demonstrate appropriate cup inclination (45 degrees) and anteversion (20 degrees). What is the most appropriate next step in management?





Explanation

For a first-time postoperative posterior dislocation occurring within the first few weeks following THA, with radiographically well-positioned components, the initial management is closed reduction followed by non-operative measures. The most appropriate step is the application of a hip abduction brace to restrict provocative positioning (flexion/adduction/internal rotation) while allowing the posterior soft tissues and capsule to heal. Early revision is not indicated unless there is a clear mechanical cause or recurrent instability.

Question 5

During a complex trigger finger release in a 55-year-old diabetic patient, the surgeon inadvertently excises the entire A2 pulley of the ring finger. What is the most likely biomechanical consequence of this isolated injury?





Explanation

The A2 and A4 pulleys are the most critical mechanically for maintaining the flexor tendons close to the bone. Loss of the A2 pulley leads to volar displacement of the flexor tendons (bowstringing). While bowstringing increases the moment arm (torque) at the joint, it significantly decreases the mechanical efficiency of the tendon, leading to an increased work of flexion and requiring increased tendon excursion to achieve the same arc of motion.

Question 6

In the process of secondary bone healing, which of the following signaling molecules is a member of the TGF-beta superfamily and acts as a potent osteoinductive factor directly responsible for driving the differentiation of mesenchymal stem cells into osteoblasts?





Explanation

Bone morphogenetic proteins (specifically BMP-2, BMP-4, and BMP-7) are key members of the transforming growth factor-beta (TGF-b) superfamily. They are the primary osteoinductive factors responsible for driving the differentiation of undifferentiated mesenchymal stem cells into osteoprogenitor cells and osteoblasts during fracture healing. VEGF is primarily responsible for angiogenesis.

Question 7

A 45-year-old male presents with right-sided neck pain radiating down his arm. He complains of weakness when trying to extend his elbow and numbness over the dorsal aspect of his middle finger. The triceps reflex is diminished. Which cervical nerve root is most likely compressed?





Explanation

C7 radiculopathy is the most common cervical radiculopathy. It typically presents with triceps weakness, weakness in wrist flexion or finger extension, numbness in the middle finger, and a diminished triceps reflex. C5 affects the deltoid/biceps reflex; C6 affects the wrist extensors/brachioradialis reflex; C8 affects finger flexors; T1 affects intrinsic hand muscles.

Question 8

A 22-year-old rugby player has recurrent anterior shoulder instability. An MRI reveals a Bankart lesion and an engaging Hill-Sachs lesion. The glenoid bone loss is calculated at 22%. Which surgical procedure is most indicated to prevent further dislocations in this patient?





Explanation

In collision athletes with significant glenoid bone loss (>20%) and an engaging Hill-Sachs lesion (an 'off-track' lesion), soft tissue stabilization procedures like Bankart repair have an unacceptably high failure rate. A bony augmentation procedure, most commonly the Latarjet procedure (coracoid transfer), is the standard of care to restore the anterior glenoid arc and create a 'sling' effect with the conjoint tendon.

Question 9

A 58-year-old patient with poorly controlled type 2 diabetes presents with a red, hot, swollen left foot. Plain radiographs reveal fragmentation of the navicular and cuneiforms with early collapse of the longitudinal arch. There are no skin ulcerations. WBC count, ESR, and CRP are within normal limits. What is the most appropriate initial management?





Explanation

The clinical presentation and normal inflammatory markers in a diabetic patient strongly suggest acute Charcot neuroarthropathy (Eichenholtz Stage I - Fragmentation). In the absence of an ulcer, infection is much less likely. The gold standard for initial management is strict immobilization and offloading, typically achieved with a total contact cast (TCC), until the acute inflammatory phase resolves and the bones begin to consolidate (Eichenholtz Stage III).

Question 10

A 40-year-old male sustains a Schatzker VI tibial plateau fracture following a motor vehicle collision. On arrival, he has tense swelling of the leg, severe pain on passive stretch of the toes, and decreased sensation in the first webspace. Emergent four-compartment fasciotomy is planned. In a standard two-incision technique, through which incision is the deep posterior compartment accessed?





Explanation

In a dual-incision technique for lower leg fasciotomies, the anterolateral incision is used to release the anterior and lateral compartments. The posteromedial incision (placed 1-2 cm posterior to the medial tibial border) is used to release the superficial posterior compartment and the deep posterior compartment. To access the deep posterior compartment, the soleus bridge must be detached from the medial tibia.

Question 11

When applying the Ponseti method for the correction of idiopathic clubfoot, which of the following describes the correct order of deformity correction?





Explanation

The sequence of correction in the Ponseti method follows the acronym CAVE: Cavus (corrected first by supinating the forefoot and elevating the first ray to align it with the hindfoot), Adductus, Varus (corrected simultaneously by abducting the foot around the fixed talar head), and finally Equinus (which is corrected last and often requires a percutaneous Achilles tenotomy).

Question 12

Which of the following bearing surfaces in total hip arthroplasty exhibits the lowest volumetric wear rate in laboratory simulator testing?





Explanation

Ceramic-on-ceramic bearing surfaces exhibit the lowest volumetric wear rates of all currently available bearing couples in total hip arthroplasty. This is due to their extreme hardness, scratch resistance, and excellent lubrication properties (fluid film lubrication). Despite the low wear rate, they carry distinct risks such as squeaking and catastrophic component fracture.

Question 13

In the Thoracolumbar Injury Classification and Severity Score (TLICS), which of the following variables is assigned the highest individual point value?





Explanation

The TLICS system assigns points based on morphology, neurologic status, and posterior ligamentous complex (PLC) integrity. Distraction morphology is assigned 4 points, making it the highest single point value in the scoring system. For comparison: translation/rotation morphology is 3 points, burst is 2; complete neurologic deficit is 2, incomplete is 3; and definite PLC disruption is 3 points.

Question 14

A 32-year-old male fell on an outstretched hand and complains of chronic wrist pain. Radiographs demonstrate a scapholunate angle of 75 degrees and a radiolunate angle of 20 degrees with the lunate extended. These findings are most consistent with which of the following patterns?





Explanation

A scapholunate angle > 60 degrees (normal is 30-60) and a radiolunate angle > 15 degrees with the lunate extended (dorsiflexed) are the radiographic hallmarks of Dorsal Intercalated Segment Instability (DISI). This is most commonly caused by a complete tear of the scapholunate interosseous ligament. In Volar Intercalated Segment Instability (VISI), the lunate is abnormally volarflexed.

Question 15

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





Explanation

According to the 2018 ICM criteria, the two major criteria (either of which definitively establishes the diagnosis of PJI) are: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. Purulence in the joint was downgraded to a minor criterion in modern scoring systems due to subjectivity and false positives in metal-on-metal or highly inflammatory conditions.

Question 16

A 45-year-old female undergoes a proximal crescentic osteotomy and distal soft tissue reconstruction for severe hallux valgus. Six months postoperatively, she complains of transfer metatarsalgia under the second metatarsal head. What is the most likely technical error during the primary procedure?





Explanation

Dorsal elevation (dorsiflexion) of the first metatarsal is a well-recognized complication of proximal first metatarsal osteotomies, particularly if fixation is inadequate. This dorsal malunion leads to a functionally shortened and elevated first ray, removing its weight-bearing capacity. The mechanical load is subsequently transferred to the lesser metatarsal heads, classically causing second metatarsal overload and transfer metatarsalgia.

Question 17

During an anatomic anterior cruciate ligament (ACL) reconstruction, the surgeon aims to accurately position the femoral tunnel. Relative to the lateral intercondylar ridge (resident's ridge) and the lateral bifurcate ridge, where is the native footprint of the anteromedial (AM) bundle of the ACL located?





Explanation

The entire native ACL footprint on the femur is located posterior (deep) to the lateral intercondylar ridge (resident's ridge). The footprint is further divided into AM and PL bundles by the lateral bifurcate ridge. When the knee is viewed in 90 degrees of flexion, the AM bundle footprint is located posterior to the lateral intercondylar ridge and superior (proximal) to the lateral bifurcate ridge, whereas the PL bundle is posterior to the intercondylar ridge and inferior (distal) to the bifurcate ridge.

Question 18

A 28-year-old male presents with a closed midshaft tibia fracture. He develops extreme pain out of proportion to his injury. Compartment pressures are measured. Which of the following absolute or differential pressure values is the most widely accepted threshold for indicating an emergency fasciotomy?





Explanation

A delta pressure (Diastolic blood pressure minus compartment pressure) of less than 30 mmHg is the most widely accepted and clinically validated threshold for diagnosing acute compartment syndrome and indicating fasciotomy. Absolute compartment pressures can be misleading, as tissue perfusion depends on the pressure gradient between the capillary bed and the interstitial space.

Question 19

A 2-year-old female presents with untreated developmental dysplasia of the hip (DDH). Radiographs show a completely dislocated left hip with a false acetabulum. The surgeon plans an open reduction and pelvic osteotomy. Which of the following pelvic osteotomies hinges at the pubic symphysis and improves anterolateral coverage without altering the volume of the true acetabulum?





Explanation

The Salter innominate osteotomy is a complete cut through the ilium extending from the greater sciatic notch to the anterior inferior iliac spine. The distal fragment is rotated anterolaterally, hinging at the pubic symphysis, to improve anterior and lateral coverage. Because it is a complete osteotomy of the ilium, it redirects the entire acetabulum but does not alter its intrinsic shape or volume. Pemberton and Dega are incomplete osteotomies that change acetabular volume.

Question 20

The mechanical axis of the lower extremity is defined as a line drawn from the center of the femoral head to the center of the ankle joint. In a normal, well-aligned lower limb, where does this mechanical axis pass relative to the knee joint center?





Explanation

In a normally aligned human leg, the mechanical axis passes slightly medial to the geometric center of the knee joint (typically about 8 to 10 mm medial to the midpoint of the tibial plateau). This slight medial offset is why the medial compartment of the normal knee bears a larger percentage (approximately 60%) of the physiological weight-bearing load compared to the lateral compartment.

Question 21

A 35-year-old female presents with a recurrent giant cell tumor of the distal femur. The multidisciplinary tumor board recommends a trial of denosumab prior to surgical resection. What is the specific mechanism of action of this medication?





Explanation

Denosumab is a fully human monoclonal antibody that specifically targets and binds to the Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By sequestering RANKL, it prevents RANKL from binding to its receptor (RANK) on the surface of osteoclasts and their precursors, thereby profoundly inhibiting osteoclast formation, function, and survival.

Question 22

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following is considered a 'major criterion' for the definitive diagnosis of a Periprosthetic Joint Infection (PJI)?





Explanation

The 2018 ICM criteria define two major criteria for definitive PJI: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. The other options are considered minor criteria that contribute to a scoring system but do not singularly confirm PJI.

Question 23

A 32-year-old manual laborer presents with progressively worsening dorsal wrist pain. Radiographs reveal sclerosis of the lunate without architectural collapse. MRI confirms avascular necrosis of the entire lunate. Radiographs also demonstrate an ulnar variance of -3mm. What is the most appropriate surgical intervention?





Explanation

This patient has Lichtman Stage II Kienböck's disease (sclerosis without collapse) with ulnar negative variance. In early-stage disease before significant carpal collapse or secondary osteoarthritis occurs, a joint-leveling procedure such as a radial shortening osteotomy is indicated to mechanically unload the lunate and potentially allow revascularization.

Question 24

In the preoperative planning for a long spinal fusion to correct adult spinal deformity, achieving a harmonious sagittal profile is a primary objective. According to Schwab's criteria, the target postoperative Lumbar Lordosis (LL) should be within what range relative to the patient's Pelvic Incidence (PI)?





Explanation

The SRS-Schwab adult spinal deformity classification emphasizes the importance of spinopelvic parameters. The primary goal for restoring sagittal balance is to achieve a Lumbar Lordosis (LL) that is proportional to the Pelvic Incidence (PI), specifically targeting a mismatch of less than 10 degrees (PI minus LL < 10 degrees).

Question 25

When evaluating graft choices for Anterior Cruciate Ligament (ACL) reconstruction, which of the following grafts exhibits the highest initial ultimate tensile load?





Explanation

A quadrupled hamstring autograft demonstrates an initial ultimate tensile load of approximately 4000 to 4100 N, which is significantly higher than that of a 10mm BPTB graft (~2900 N), quadriceps tendon (~2100-2300 N), and the native ACL (~2100 N). Despite the higher ultimate load, clinical outcomes depend heavily on graft healing, fixation, and stiffness.

Question 26

A 45-year-old male is brought to the trauma bay after a high-speed motorcycle collision. He has an Anteroposterior Compression (APC) Type III pelvic ring injury. He remains hypotensive (BP 75/40 mmHg) despite receiving 2 liters of crystalloid and 2 units of uncrossmatched PRBCs. A pelvic binder is correctly applied over the greater trochanters. A FAST ultrasound is negative. What is the most appropriate next step in management?





Explanation

In a hemodynamically unstable patient with an unstable pelvic ring fracture and a negative FAST exam (effectively ruling out major intra-abdominal, intraperitoneal hemorrhage), the primary source of bleeding is assumed to be the retroperitoneal pelvic venous plexus or arterial injury. Immediate preperitoneal pelvic packing and/or pelvic angiography with embolization (dictated by institutional protocols) is the definitive life-saving intervention.

Question 27

A 12-year-old boy presents with left groin pain and an obligatory external rotation of the hip during flexion. Radiographs confirm a moderate, stable slipped capital femoral epiphysis (SCFE). Which of the following patient characteristics is the strongest absolute indication for prophylactic in-situ pinning of the contralateral, asymptomatic hip?





Explanation

Prophylactic pinning of the contralateral hip in unilateral SCFE remains controversial for idiopathic cases. However, it is strongly indicated (often considered an absolute indication) in patients with underlying metabolic bone diseases (such as renal osteodystrophy) or endocrinopathies (like hypothyroidism or growth hormone supplementation), as their risk of developing a contralateral slip approaches 100%.

Question 28

A 55-year-old patient with long-standing, poorly controlled diabetes presents with a swollen, warm, and erythematous right foot. There is no open ulceration. Radiographs reveal marked osteopenia, periarticular bony debris, fragmentation, and dorsal subluxation at the tarsometatarsal joints. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent?





Explanation

Eichenholtz Stage 1 (Developmental) is characterized clinically by a red, hot, swollen foot and radiographically by active bone destruction, fragmentation, periarticular debris, and joint subluxation/dislocation. Stage 0 lacks radiographic changes. Stage 2 involves absorption of fine debris and early fusion. Stage 3 is characterized by remodeling and consolidation of the deformity.

Question 29

Bone morphogenetic proteins (BMPs) play a critical role in bone healing. Which of the following statements accurately describes the mechanism of action of BMP-2?





Explanation

BMP-2 and BMP-7 are potent osteoinductive growth factors. They function by binding to serine/threonine kinase receptors on the surface of undifferentiated mesenchymal stem cells. This binding activates the intracellular Smad signaling pathway, upregulating transcription factors like Runx2, which induces the differentiation of these cells into the osteoblast lineage.

Question 30

During an anterolateral (deltoid-splitting) approach for the open reduction and internal fixation of a proximal humerus fracture, which neurovascular structure is at highest risk if the dissection extends more than 5 cm distal to the lateral edge of the acromion?





Explanation

The axillary nerve courses horizontally across the deep surface of the deltoid muscle, typically 5 to 7 cm distal to the lateral margin of the acromion. Extending the split of the deltoid beyond this safe zone places the axillary nerve at significant risk of iatrogenic injury, leading to loss of deltoid function.

Question 31

Proximal pole fractures of the scaphoid have a high rate of nonunion and avascular necrosis. This is primarily dictated by the intraosseous vascular anatomy of the scaphoid. Where does the dominant arterial supply enter the scaphoid?





Explanation

The primary blood supply to the scaphoid (accounting for 70-80% of the intraosseous vascularity) enters through the dorsal ridge in the distal half of the bone. The blood flow is retrograde to the proximal pole, making proximal pole fractures highly susceptible to avascular necrosis due to disruption of this retrograde vascular supply.

Question 32

In a well-functioning conventional metal-on-polyethylene Total Hip Arthroplasty (THA), what is the primary mode of wear that generates the majority of clinically significant submicron polyethylene debris, ultimately leading to macrophage-mediated osteolysis?





Explanation

Adhesive wear is the primary continuous wear mechanism between two smooth bearing surfaces (such as the metal femoral head and the polyethylene liner). It occurs when microscopic asperities on the softer material (polyethylene) adhere to the harder surface and are then torn away during sliding motion. This process generates millions of submicron particles that provoke the biologic cascade leading to osteolysis.

Question 33

A 19-year-old collegiate gymnast presents with bilateral shoulder pain. Examination reveals a 2+ sulcus sign in neutral rotation, 3+ anterior load-and-shift, and 3+ posterior load-and-shift bilaterally. She denies any specific traumatic event. What is the most appropriate initial management?





Explanation

This patient presents with atraumatic Multidirectional Instability (MDI), classically seen in hyperlax individuals (AMBRI: Atraumatic, Multidirectional, Bilateral, Rehabilitation, Inferior capsular shift). The initial, and often definitive, treatment is an extensive course of physical therapy (usually 6-12 months) focused on strengthening the dynamic stabilizers (rotator cuff and periscapular musculature). Surgery is reserved for patients who fail prolonged rehabilitation.

Question 34

A 78-year-old male sustains an Anderson-D'Alonzo Type II odontoid fracture after a ground-level fall. Imaging reveals 7 mm of posterior displacement. If conservative management is selected, which of the following characteristics is the strongest independent predictor of nonunion?





Explanation

For Type II odontoid fractures, known risk factors for nonunion include initial displacement > 5 mm, posterior displacement, angulation > 10 degrees, and advanced age (typically > 50 or 65 depending on the study). Initial displacement greater than 5 mm is widely cited in literature as the strongest single predictive factor for nonunion, often prompting surgical consideration even in older patients.

Question 35

A 6-week-old infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. Two weeks later at a follow-up appointment, the parents report the infant is no longer actively kicking the right leg. On examination, the infant has active ankle and toe movement but cannot actively extend the knee. Patellar reflex is diminished. What is the most likely iatrogenic cause of this presentation?





Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically resulting from hyperflexion of the hips, which causes compression of the femoral nerve against the inguinal ligament. It manifests as an inability to actively extend the knee. The appropriate action is to temporarily loosen the anterior straps or remove the harness to allow the nerve to recover.

Question 36

Articular cartilage is structurally divided into four distinct zones. Which zone is characterized by the highest concentration of water, the lowest concentration of proteoglycans, and collagen fibers that run parallel to the articular surface?





Explanation

The superficial (tangential) zone of articular cartilage makes up the top 10-20% of the cartilage thickness. It is designed to resist shear forces and contains densely packed Type II collagen fibers oriented parallel to the joint surface. It has the highest water content (up to 80%) and the lowest concentration of proteoglycans compared to the deeper zones.

Question 37

A 28-year-old male presents with severe foot pain after a high-energy motor vehicle accident. Radiographs reveal a Hawkins Type III fracture of the talar neck. Which of the following precisely describes this injury pattern?





Explanation

The Hawkins classification describes talar neck fractures: Type I is an undisplaced fracture; Type II involves subtalar subluxation or dislocation; Type III involves dislocation of both the subtalar and tibiotalar joints (the talar body is often extruded posteromedially); Type IV (added later by Canale and Kelly) includes subluxation or dislocation of the subtalar, tibiotalar, and talonavicular joints.

Question 38

In a 15-year-old patient diagnosed with high-grade, non-metastatic conventional osteosarcoma of the distal femur, which of the following is considered the single most important prognostic factor for long-term overall survival?





Explanation

The degree of histologic tumor necrosis following preoperative (neoadjuvant) chemotherapy is the most reliable and powerful prognostic indicator in high-grade osteosarcoma. A 'good response' is classically defined as 90% or greater tumor necrosis, which strongly correlates with improved disease-free and overall survival rates.

Question 39

A 45-year-old female presents with a painful bunion. Weight-bearing radiographs demonstrate a Hallux Valgus Angle (HVA) of 35 degrees, an Intermetatarsal Angle (IMA) of 16 degrees, and a Distal Metatarsal Articular Angle (DMAA) of 22 degrees. To achieve a congruent joint and prevent early recurrence, the surgical plan MUST incorporate which of the following?





Explanation

A normal Distal Metatarsal Articular Angle (DMAA) is less than 10 degrees. An abnormally high DMAA (22 degrees in this case) indicates significant lateral deviation of the distal metatarsal articular surface. Procedures that correct only the IMA (like a standard proximal osteotomy or Lapidus) without addressing the DMAA will leave the MTP joint incongruent, leading to stiffness, pain, and high recurrence risk. A biplanar or double osteotomy (often including a distal medial closing wedge like a Reverdin) is necessary to reorient the articular surface.

Question 40

A patient presents with profound intrinsic muscle weakness in the right hand. Neurological examination reveals marked atrophy of the first dorsal interosseous and hypothenar muscles. However, sensation is completely preserved over both the volar and dorsal aspects of the small finger and the ulnar half of the ring finger. The compressive pathology is most likely located in which anatomical region?





Explanation

Guyon's canal is divided into three zones. Zone I contains the mixed ulnar nerve proximal to its bifurcation. Compression here causes mixed motor and sensory deficits. Zone II surrounds the deep motor branch only; compression here results in isolated motor weakness of the ulnar-innervated intrinsic muscles with spared sensation. Zone III surrounds the superficial sensory branch; compression here causes isolated volar sensory deficits. The dorsal sensory branch leaves the main nerve proximal to Guyon's canal, so its sensation is spared in all Guyon's canal lesions.

Question 41

A 55-year-old male presents with advanced Scapholunate Advanced Collapse (SLAC) wrist arthritis. Radiographs show arthritic changes involving the radioscaphoid and capitolunate joints, with preservation of the radiolunate joint. What is the most appropriate surgical treatment?





Explanation

In Stage III SLAC wrist, arthritic changes involve the radioscaphoid and capitolunate joints. Because the capitate head is arthritic, a proximal row carpectomy (PRC) is contraindicated, as the arthritic capitate would articulate with the lunate fossa, leading to persistent pain and failure. Scaphoid excision and four-corner fusion is the treatment of choice. The radiolunate joint is characteristically spared in SLAC and SNAC arthritis, making radiolunate-preserving procedures like four-corner fusion ideal.

Question 42

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the parents report that the child has stopped extending her knee on the treated side. On examination, the patellar reflex is absent, and the hip is positioned in 125 degrees of flexion. Which of the following is the most likely cause of this complication?





Explanation

Excessive hip flexion (typically >120 degrees) in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. This presents clinically as a loss of active knee extension and an absent patellar reflex. The treatment is to temporarily adjust the anterior straps to decrease hip flexion or remove the harness until nerve function returns. Excessive abduction, on the other hand, is associated with avascular necrosis.

Question 43

Highly cross-linked polyethylene (HXLPE) was introduced in total hip arthroplasty to reduce wear and subsequent osteolysis. Which of the following mechanical properties is significantly REDUCED as a direct consequence of increasing the radiation dose used to cross-link the polyethylene?





Explanation

Increasing the radiation dose to cross-link polyethylene improves its wear resistance significantly but at the cost of reducing its mechanical properties, particularly fracture toughness, fatigue strength, and ultimate tensile strength. To mitigate oxidation, HXLPE must be remelted or annealed, or doped with an antioxidant like Vitamin E. Creep resistance is actually slightly improved or unchanged by cross-linking.

Question 44

A 42-year-old male requires open reduction and internal fixation for a complex posterolateral tibial plateau fracture. A posterolateral (Frosch) approach is planned. To safely access the posterolateral articular surface, the deep surgical interval is developed between which two structures?





Explanation

The classic posterolateral approach to the tibial plateau (such as the Frosch approach) uses an interval between the lateral head of the gastrocnemius (retracted medially) and the biceps femoris (retracted laterally). This provides direct access to the posterior aspect of the lateral tibial plateau. Care must be taken to identify and protect the common peroneal nerve, which lies directly posterior to the biceps femoris tendon.

Question 45

A 24-year-old male is brought to the emergency department after a high-speed motor vehicle collision in which he was wearing a lap-belt only. Radiographs and CT of the lumbar spine reveal a flexion-distraction injury (Chance fracture) at L2. Which of the following associated injuries must be aggressively ruled out in this patient?





Explanation

A Chance fracture is a flexion-distraction injury of the spine, historically associated with lap-belt use in motor vehicle accidents. The fulcrum of flexion is located anterior to the vertebral body, resulting in failure of the posterior and middle columns in tension. Up to 40-50% of these patients have an associated intra-abdominal injury, most commonly involving hollow viscus organs (small bowel lacerations or perforations) due to the severe compression of the abdomen against the lap belt.

Question 46

During a primary posterior-stabilized total knee arthroplasty, the surgeon assesses the gap kinematics with trial components in place. The knee demonstrates a symmetric and well-balanced extension gap, but the flexion gap is unacceptably tight. Which of the following is the most appropriate technical adjustment to correct this imbalance?





Explanation

A knee that is tight in flexion but balanced in extension has an isolated tight flexion gap. To selectively loosen the flexion gap without altering the extension gap, the surgeon should decrease the anteroposterior dimension of the femoral component by downsizing it (using a smaller femoral component with the same anterior reference to decrease the posterior condylar offset). Increasing the posterior tibial slope (within safe limits) is another option. Resecting more distal femur or releasing the posterior capsule would inappropriately affect the extension gap.

Question 47

A 16-year-old male presents with severe right thigh pain that is distinctly worse at night and dramatically relieved by ibuprofen. Imaging reveals a 1.0 cm radiolucent nidus surrounded by dense reactive sclerosis in the proximal femoral diaphysis. The pathogenesis of this lesion's characteristic pain profile is primarily mediated by local overexpression of which substance?





Explanation

Osteoid osteoma is a benign bone-forming tumor characterized by a small radiolucent nidus (<1.5 cm) surrounded by dense sclerotic bone. The intense, night-time pain that is classically relieved by NSAIDs is due to the extremely high production of Prostaglandin E2 (PGE2) by the nidus-forming osteoblasts. The nidus contains up to 1000 times the normal level of PGE2.

Question 48

Which of the following eponymous radiographic signs describes a crescent-shaped area of increased radiodensity in the proximal femoral metaphysis on an AP pelvis radiograph in a patient with a Slipped Capital Femoral Epiphysis (SCFE)?





Explanation

The Blanch sign of Steel is a crescent-shaped double density seen on the AP radiograph of a SCFE, caused by the superimposition of the posteriorly displaced femoral epiphysis on the metaphysis. Trethowan's sign refers to Klein's line passing completely superior to the epiphysis. Waldenstrom's sign is an increased distance between the medial epiphysis and the pelvic teardrop (effusion). The sagging rope sign is a thin sclerotic line running transversely across the metaphysis indicating severe deformity.

Question 49

Which of the following clinical scenarios of bone formation is predominantly driven by intramembranous ossification rather than endochondral ossification?





Explanation

Distraction osteogenesis (e.g., bone lengthening via an Ilizarov frame) primarily occurs via intramembranous ossification, where osteoblasts directly differentiate from mesenchymal stem cells to form bone without a cartilage intermediate. Callus formation in secondary fracture healing, physeal growth, and most heterotopic ossification occur via endochondral ossification (forming a cartilage model first).

Question 50

In evaluating a patient with recurrent anterior shoulder instability, you assess the 'glenoid track' on advanced imaging. A Hill-Sachs lesion is deemed 'off-track'. Which of the following anatomic scenarios correctly defines an off-track Hill-Sachs lesion?





Explanation

The glenoid track is defined as the contact zone of the glenoid on the humeral head during shoulder abduction and external rotation. It is calculated as 83% of the normal glenoid width minus the width of any anterior glenoid bone defect. A Hill-Sachs lesion is 'off-track' (meaning it will engage the anterior glenoid rim) if its medial margin extends further medially than the medial margin of the glenoid track. This typically requires an operation that addresses the humeral head defect (e.g., remplissage) or restores the glenoid track (e.g., Latarjet).

Question 51

Following a Zone II flexor tendon repair of the index finger, a structured rehabilitation program is initiated. Biomechanical studies have shown that the strength of the tendon repair during the initial healing phase is most directly proportional to which of the following surgical factors?





Explanation

Biomechanical studies have consistently demonstrated that the ultimate tensile strength of a flexor tendon repair is most directly proportional to the number of core suture strands crossing the repair site. For example, a 4-strand repair is significantly stronger than a 2-strand repair, and a 6-strand is stronger than a 4-strand. While an epitenon repair improves gliding and adds some strength, the number of core strands is the primary determinant of initial gap resistance and repair strength, allowing for early active motion protocols.

Question 52

A 58-year-old patient with long-standing, poorly controlled diabetes mellitus presents with a swollen, warm, and erythematous right foot. There is no open ulceration. The skin temperature on the affected foot is 4 degrees Celsius warmer than the contralateral foot. Elevation of the limb for 10 minutes results in significant reduction of the erythema. Radiographs show soft tissue swelling and early periarticular fragmentation at the tarsometatarsal joints. What is the most appropriate initial management?





Explanation

This patient presents with an acute Eichenholtz Stage I Charcot arthropathy. The key clinical distractor is ruling out infection; in acute Charcot, erythema typically resolves with elevation, whereas in cellulitis/infection, it does not. Furthermore, there is no open ulcer. The mainstay of treatment for acute Charcot arthropathy is immobilization and offloading. Total contact casting with strict non-weight-bearing is the gold standard to prevent further architectural collapse during the active fragmentation stage.

Question 53

According to the Young and Burgess classification, a Lateral Compression Type II (LC-2) pelvic ring injury is characterized by anterior ring fractures and which of the following posterior ring injury patterns?





Explanation

In the Young and Burgess classification, a Lateral Compression Type I (LC-1) injury involves a sacral compression fracture. An LC-2 injury involves a crescent (ilium) fracture on the side of impact due to the internal rotation force continuing past the sacrum, causing the strong intact posterior SI ligaments to avulse a piece of the posterior ilium. An LC-3 is a 'windswept' pelvis, featuring an LC injury on the impacted side and an APC-type injury on the contralateral side.

Question 54

In patients undergoing surgical decompression for Cervical Spondylotic Myelopathy (CSM), which of the following preoperative factors has been consistently proven in the literature to be the strongest predictor of postoperative neurological recovery and clinical outcome?





Explanation

Multiple large prospective studies, including those by the AOSpine North America and International CSM studies, have shown that the strongest predictors of postoperative outcomes in CSM are the baseline severity of myelopathy (modified Japanese Orthopaedic Association - mJOA score) and the duration of symptoms prior to surgery. While T2 hyperintensity (and especially T1 hypointensity) and age have some prognostic value, baseline clinical severity and chronicity are the most robust predictors. Surgical approach does not significantly alter the ultimate neurological recovery if adequately decompressed.

Question 55

The direct anterior approach to the hip (Smith-Petersen) exploits a true internervous and intermuscular plane. During the deep dissection, retractors are placed around the femoral neck. To minimize the risk of denervating the tensor fasciae latae (TFL), the surgeon must be careful to protect its nerve supply. Which nerve supplies the TFL, and where does it typically course in relation to this surgical approach?





Explanation

The direct anterior approach utilizes the internervous plane between the femoral nerve (sartorius, rectus femoris) and the superior gluteal nerve (TFL, gluteus medius/minimus). The TFL is innervated by the superior gluteal nerve, which enters the muscle from its posterior-proximal aspect. Overly vigorous retraction of the TFL laterally, or dissection too far proximal and posterior, can place the superior gluteal nerve branches to the TFL at risk, potentially leading to muscle atrophy and a postoperative Trendelenburg gait.

Question 56

A 30-year-old male sustains a vertically oriented, displaced femoral neck fracture (Pauwels Type III) after falling from a height. Open reduction and internal fixation is planned. Biomechanical studies indicate that which of the following fixation constructs provides the greatest resistance to vertical shear forces and varus collapse for this specific fracture pattern?





Explanation

Vertical femoral neck fractures in young adults (Pauwels Type III) are subject to high shear forces, making them prone to varus collapse and nonunion. Biomechanical studies have consistently shown that a fixed-angle device, such as a sliding hip screw (SHS) with a supplemental derotation screw (to control rotational forces), provides superior mechanical stability and resistance to vertical shear compared to multiple parallel cannulated screws for high-angle (vertical) femoral neck fractures.

Question 57

A 12-year-old girl presents with a destructive diaphyseal lesion in the right fibula, accompanied by an 'onion-skin' periosteal reaction. A core needle biopsy reveals a small blue round cell tumor. Molecular genetic testing identifies a t(11;22)(q24;q12) chromosomal translocation. Immunohistochemistry of this tumor is most likely to show strong, diffuse membrane positivity for which of the following markers?





Explanation

The clinical, radiographic, and genetic findings (t(11;22) producing the EWS-FLI1 fusion protein) are diagnostic of Ewing Sarcoma. Ewing sarcoma cells characteristically show strong, diffuse membranous staining for CD99 (the product of the MIC2 gene). Desmin and MyoD1 are positive in rhabdomyosarcoma. S-100 is positive in neural crest origin tumors (like melanoma or schwannoma) and some cartilage tumors. Cytokeratin is a marker for carcinomas and synovial sarcoma.

Question 58

Bone Morphogenetic Proteins (BMPs) are used clinically to enhance bone healing. They act as osteoinductive agents by binding to cell surface receptors and initiating an intracellular signaling cascade. Which of the following intracellular signaling molecules is the primary direct mediator of the canonical BMP pathway?





Explanation

Bone Morphogenetic Proteins (BMPs) belong to the TGF-beta superfamily. The canonical signaling pathway for BMPs involves binding to serine/threonine kinase cell surface receptors, which then phosphorylate intracellular receptor-regulated Smads, specifically Smad 1, 5, and 8. These complex with the co-Smad (Smad 4) and translocate to the nucleus to regulate gene transcription for osteoblastic differentiation. Beta-catenin is involved in the Wnt signaling pathway. NF-kappaB is involved in RANKL/osteoclast signaling.

Question 59

A 6-year-old boy with spastic quadriplegic cerebral palsy is evaluated for hip surveillance. His Gross Motor Function Classification System (GMFCS) level is V. An anteroposterior pelvis radiograph shows a Reimers' migration percentage of 45% bilaterally with early uncovering of the femoral heads, but the femoral heads are spherical and the cartilage space is preserved. What is the most appropriate management?





Explanation

In children with severe CP (GMFCS IV or V), the risk of progressive hip displacement is very high. A Reimers' migration percentage (MP) > 30% defines subluxation, and an MP > 40-50% in a 6-year-old typically requires reconstructive bony surgery to prevent painful dislocation. Soft tissue releases alone (adductor/psoas tenotomies) are generally reserved for early subluxation (MP 30-40%) in younger children (<4 years) with no bony deformity. Once significant subluxation (MP >40%) with bony dysplasia is present, bony reconstruction (VDRO +/- pelvic osteotomy, such as Dega or San Diego) is the gold standard.

Question 60

A 22-year-old female is 16 weeks status-post an uncomplicated primary anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft. She complains of anterior knee pain and a painful clunk at terminal extension. On examination, her knee flexion is symmetric to the contralateral side, but she lacks the final 15 degrees of terminal extension. What is the most likely cause of this complication?





Explanation

The patient is presenting with a classic 'Cyclops lesion' (localized anterior arthrofibrosis), which is a fibrovascular nodule that forms anterior to the ACL graft in the intercondylar notch. It typically presents with a mechanical block to terminal extension, an audible or palpable 'clunk' at terminal extension, and anterior knee pain. It does not severely restrict flexion. Treatment is arthroscopic excision of the nodule. Anterior placement of the tibial (not femoral) tunnel can impinge the graft and lead to a Cyclops lesion, but the direct cause of the block is the fibrovascular nodule itself.

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