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Arab Orthopaedic Board MCQs - Part 16

27 Apr 2026 90 min read 70 Views
Arab Ortho Board MCQs - Part 15

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Looking for accurate information on Arab Orthopaedic Board MCQs - Part 16? Practice Arab Orthopaedic Board MCQs Part 16. Review orthopedic surgery questions 751 to 800 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 16

Comprehensive 100-Question Exam


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Question 1

During an ilioinguinal approach for the fixation of an anterior column acetabular fracture, significant arterial bleeding is encountered posterior to the superior pubic ramus. Which of the following anatomical connections is the most likely source of this bleeding (Corona Mortis)?





Explanation

The Corona Mortis (Crown of Death) represents a vascular anastomosis between the external iliac system (usually via the inferior epigastric artery or vein) and the internal iliac system (obturator artery or vein). It is located posterior to the superior pubic ramus at a variable distance (average 4-6 cm) from the symphysis pubis. Iatrogenic injury during the ilioinguinal approach or placement of superior pubic ramus screws can lead to life-threatening hemorrhage.

Question 2

A 34-year-old female with a recurrent giant cell tumor of the distal radius is deemed unresectable and is started on denosumab therapy. What is the specific mechanism of action of this medication?





Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to the Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By binding to RANKL, it prevents RANKL from activating the RANK receptor on the surface of osteoclasts and their precursors. In giant cell tumors (GCT), the neoplastic stromal cells express RANKL, which recruits and activates the reactive multinucleated giant cells (osteoclast-like cells) that cause bone destruction. Denosumab inhibits this interaction, halting bone lysis.

Question 3

A 4-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 2-week follow-up, the mother reports that the infant has stopped actively extending her knee on the treated side. Upon examination, the hip is well-reduced. Which of the following is the most appropriate management regarding the harness?





Explanation

Decreased active knee extension in an infant treated with a Pavlik harness is highly suspicious for a femoral nerve palsy. This complication is typically caused by excessive hip flexion, which compresses the femoral nerve against the inguinal ligament. The correct management is to immediately loosen the anterior flexion straps. Once the nerve function returns, the straps can be cautiously readjusted. Femoral nerve palsy in this setting usually resolves completely if addressed promptly.

Question 4

A 6-year-old child presents with a notably short neck, a low posterior hairline, and restricted cervical range of motion. Radiographs demonstrate congenital fusion of C3-C4 and C5-C6. Because of the diagnosis, which of the following is the most appropriate initial screening test?





Explanation

This patient presents with the classic triad of Klippel-Feil syndrome (short neck, low hairline, limited cervical ROM). Patients with Klippel-Feil syndrome have a high incidence of associated systemic anomalies. Up to 35% of these patients have genitourinary tract anomalies, most commonly unilateral renal agenesis. Therefore, a screening renal ultrasound is highly recommended. Congenital heart defects (such as VSD) and hearing loss are also common, warranting further evaluation, but renal US is standard for initial workup.

Question 5

During a primary repair of a Zone II flexor tendon injury, extensive trauma to the flexor tendon sheath is noted. To prevent clinically significant bowstringing of the tendon, which of the following combinations of pulleys must be preserved or reconstructed as an absolute minimum?





Explanation

The flexor tendon sheath in the fingers consists of five annular (A1-A5) and three cruciform (C1-C3) pulleys. The A2 and A4 pulleys arise directly from the periosteum of the proximal and middle phalanges, respectively. They are the most critical biomechanical pulleys for preventing tendon bowstringing during finger flexion. Loss of both A2 and A4 results in profound mechanical disadvantage and loss of digital motion.

Question 6

A 55-year-old male undergoes a primary total hip arthroplasty using a ceramic-on-ceramic bearing surface. Two years postoperatively, he complains of an audible squeaking sound from the hip when walking, though he has no pain. Which of the following technical factors is most strongly associated with this phenomenon?





Explanation

Squeaking is a well-documented complication of ceramic-on-ceramic total hip arthroplasties. It is most commonly associated with component malposition, specifically high inclination angle and excessive anteversion of the acetabular cup. This malposition leads to stripe wear and 'edge loading' (the femoral head articulating at the rim of the acetabular liner), which disrupts fluid-film lubrication and generates high-frequency vibrations perceived as a squeak.

Question 7

A Segond fracture observed on an AP radiograph of the knee is widely recognized as pathognomonic for an anterior cruciate ligament (ACL) tear. This bony avulsion occurs at the tibial insertion of the anterolateral ligament (ALL). Where does the ALL anatomically originate?





Explanation

The Segond fracture is a cortical avulsion fracture off the proximal anterolateral tibia, associated with ACL injuries. Anatomical studies identify this as the tibial insertion of the anterolateral ligament (ALL) or the lateral capsular ligament. The ALL originates on the lateral femoral epicondyle, slightly anterior and distal to the origin of the fibular collateral ligament (FCL), and inserts on the anterolateral tibia midway between Gerdy's tubercle and the fibular head.

Question 8

According to Perren's Strain Theory, the local mechanical environment dictates the type of tissue that forms in a fracture gap. What is the maximum interfragmentary strain that permits the formation of primary lamellar bone?





Explanation

Perren's Strain Theory describes how tissue differentiation at a fracture site is governed by interfragmentary strain. Lamellar bone (primary bone healing without a cartilaginous intermediate) can only tolerate an interfragmentary strain of less than 2%. Strains between 2% and 10% permit woven bone formation. Strains between 10% and 30% lead to cartilage formation (enchondral ossification), and strains >30% result in granulation tissue, leading to a nonunion if not stabilized.

Question 9

A 22-year-old soccer player sustains a midfoot injury. An AP weight-bearing radiograph demonstrates a widening of the space between the first and second metatarsal bases and a small avulsion fracture ('Fleck sign'). The avulsed ligament normally connects which two structures?





Explanation

The 'Fleck sign' represents a bony avulsion of the Lisfranc ligament. The Lisfranc ligament is a stout, interosseous ligament that originates from the lateral aspect of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal. It provides critical stability to the midfoot, as there is no direct ligamentous connection between the bases of the first and second metatarsals.

Question 10

During a surgical dislocation of the hip via a trochanteric flip approach, preserving the blood supply to the femoral head is paramount. The main deep branch of the medial circumflex femoral artery (MFCA) runs consistently between which two anatomic structures as it passes posterior to the hip joint?





Explanation

Understanding the precise course of the medial circumflex femoral artery (MFCA) is crucial for joint-preserving hip surgery (e.g., Ganz approach). The deep branch of the MFCA passes superiorly after coursing between the pectineus and iliopsoas, then consistently travels posteriorly between the obturator externus and the quadratus femoris muscles. It then runs deep to the common tendon of the obturator internus and gemelli to supply the femoral head.

Question 11

A 9-year-old male presents with a slipped capital femoral epiphysis (SCFE) of the right hip. Under which of the following conditions is prophylactic in situ pinning of the contralateral asymptomatic left hip most strongly indicated?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strictly indicated in patients who have a high likelihood of a subsequent contralateral slip. Absolute or strong indications include underlying endocrine disorders (such as hypothyroidism or growth hormone deficiency), metabolic bone disease (such as renal osteodystrophy), prior radiation therapy to the pelvis, and very young age (typically females <10 and males <12). Obesity or slip severity on the affected side are not absolute indications on their own.

Question 12

A 20-year-old female presents to the trauma bay after a high-speed motor vehicle collision where she was wearing only a lap belt. Radiographs and CT of the lumbar spine reveal a flexion-distraction injury (Chance fracture) through the L2 vertebral body. She is neurologically intact. Which of the following associated injuries has the highest incidence with this specific fracture pattern?





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 shifted anteriorly to the abdominal wall, leading to distraction forces through the posterior and middle columns, and sometimes the anterior column. This mechanism frequently causes concurrent severe compressive or sheer injuries to intra-abdominal organs. Hollow viscus (bowel) injuries occur in up to 40-50% of patients with Chance fractures.

Question 13

During a primary total knee arthroplasty in a patient with a severe fixed varus deformity, the surgeon removes the medial osteophytes and releases the deep medial collateral ligament. Trialing reveals that the medial compartment is now balanced in flexion but remains excessively tight in extension. What is the most appropriate next step in the medial release sequence?





Explanation

Balancing a varus knee requires an understanding of how specific medial structures affect the flexion and extension gaps. The posteromedial capsule primarily acts as a secondary restraint in extension and has little effect in flexion. If the knee is tight in extension but balanced in flexion, the posteromedial capsule is the correct structure to release. Releasing the superficial MCL would significantly increase the gap in both flexion and extension.

Question 14

A 35-year-old carpenter presents with weakness in his right hand. Examination reveals an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Sensation in the entire hand is intact. Which anomalous or muscular structure is most commonly implicated in the compression of the affected nerve?





Explanation

The patient's presentation of isolated motor weakness to the FPL (thumb IP joint flexion) and FDP to the index finger, with preserved sensation, is classic for Anterior Interosseous Nerve (AIN) syndrome. The AIN is a motor branch of the median nerve. Compression frequently occurs in the proximal forearm. Gantzer's muscle (the accessory head of the flexor pollicis longus) is a well-known anomalous structure that can cause AIN entrapment. Other causes include the tendinous edge of the deep head of the pronator teres or the FDS aponeurotic arch. The ligament of Struthers affects the main median nerve (causing sensory findings), and the Arcade of Frohse compresses the posterior interosseous nerve.

Question 15

A 14-year-old boy has been diagnosed with a high-grade intramedullary osteosarcoma of the distal femur. He undergoes 10 weeks of neoadjuvant chemotherapy followed by surgical resection. Which of the following parameters obtained from the resected specimen provides the most significant prognostic value for long-term overall survival?





Explanation

In the management of high-grade osteosarcoma, the histologic response to neoadjuvant chemotherapy is the single most important prognostic factor for long-term survival. This is quantified by the percentage of tumor necrosis in the resected specimen (Huvos grading system). A 'good' response is defined as greater than 90% tumor necrosis, which correlates with significantly improved disease-free and overall survival rates compared to patients with less than 90% necrosis.

Question 16

A 25-year-old baseball pitcher undergoes shoulder arthroscopy for chronic shoulder pain. The surgeon visualizes a bucket-handle tear of the superior labrum that also splits and extends into the long head of the biceps tendon, with the remaining biceps anchor still attached to the glenoid. According to the Snyder classification, what type of SLAP tear is this?





Explanation

The Snyder classification of Superior Labrum Anterior and Posterior (SLAP) tears: Type I: Fraying of the superior labrum with an intact biceps anchor. Type II: Detachment of the superior labrum and biceps anchor from the superior glenoid. Type III: Bucket-handle tear of the superior labrum with an intact biceps anchor. Type IV: Bucket-handle tear of the superior labrum that extends into the long head of the biceps tendon. This patient has a Type IV lesion.

Question 17

A 55-year-old patient with poorly controlled type 2 diabetes presents with a unilaterally swollen, red, and warm left foot. He denies trauma or skin breaks. Radiographs reveal fragmentation of the tarsometatarsal joints, periarticular debris, and joint subluxation. Inflammatory markers are mildly elevated, but MRI shows no marrow enhancement characteristic of osteomyelitis. According to the Eichenholtz classification, what is the stage and most appropriate initial management?





Explanation

This patient presents with acute Charcot arthropathy of the midfoot. The Eichenholtz classification describes three stages. Stage 1 (Development/Fragmentation) is characterized by a red, hot, swollen foot with radiographs showing bone debris, fragmentation, and subluxation. Stage 2 (Coalescence) involves absorption of debris and early fusion. Stage 3 (Consolidation) shows mature remodeling. The gold standard for initial treatment of Stage 1 Charcot arthropathy is immobilization and offloading, typically using a total contact cast, until the active inflammatory phase subsides.

Question 18

A 28-year-old male is admitted after a motorcycle accident resulting in a closed, comminuted tibial shaft fracture. Two hours post-admission, he complains of severe leg pain out of proportion to the injury. His blood pressure is 110/70 mmHg. The anterior compartment pressure is measured at 45 mmHg using a slit-catheter technique. What is the calculated delta pressure and the recommended intervention?





Explanation

Acute compartment syndrome is a surgical emergency. The 'delta pressure' is calculated as the Diastolic Blood Pressure minus the Intracompartmental Pressure. A delta pressure of < 30 mmHg (some texts say < 20-30 mmHg) is widely accepted as an absolute indication for fasciotomy, as capillary perfusion is significantly compromised. Here, Diastolic BP (70) - Compartment Pressure (45) = 25 mmHg. Because 25 mmHg is less than the 30 mmHg threshold, immediate four-compartment fasciotomy is indicated.

Question 19

Articular cartilage is structurally organized into distinct zones, each with unique mechanical properties and biochemical compositions. Which zone contains the highest concentration of proteoglycans and features chondrocytes arranged in vertical columns perpendicular to the joint surface?





Explanation

Articular cartilage consists of four zones: Superficial, Middle, Deep, and Calcified. The Deep (radial) zone provides the greatest resistance to compressive forces. It is characterized by having the highest concentration of proteoglycans, the lowest water content of the uncalcified zones, and chondrocytes that are arranged in vertical columns. The collagen fibers in this zone are thickest and run perpendicular to the articular surface, anchoring into the tidemark.

Question 20

A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. During the fragmentation stage, an AP radiograph of his pelvis is used to determine his prognosis according to the Herring lateral pillar classification. To be classified as Group C (which carries the worst prognosis), the lateral pillar of the femoral head must demonstrate what percentage of maintained height compared to the contralateral normal hip?





Explanation

The Herring lateral pillar classification is assessed on an AP radiograph during the fragmentation phase of Legg-Calvé-Perthes disease. It is based on the height of the lateral third (pillar) of the capital femoral epiphysis. Group A: 100% of the lateral pillar height is maintained. Group B: >50% of the lateral pillar height is maintained. Group C: <50% of the lateral pillar height is maintained. Patients in Group C have the poorest outcomes, often developing aspherical incongruency and early osteoarthritis.

Question 21

A 45-year-old male presents in hemorrhagic shock following a high-speed motorcycle accident. Anteroposterior pelvis radiograph demonstrates an Anteroposterior Compression Type III (APC-III) pelvic ring injury. A pelvic binder is applied, and a massive transfusion protocol is initiated. Despite these measures, his hemodynamics remain unstable. A FAST (Focused Assessment with Sonography for Trauma) exam is negative. What is the most appropriate next step in management?





Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury and a negative FAST exam, the source of bleeding is predominantly retroperitoneal (venous plexus or arterial). The accepted standard algorithms recommend either preperitoneal pelvic packing or pelvic angiography/embolization. CT scan is contraindicated in a hemodynamically unstable patient. Laparotomy is indicated for intra-abdominal bleeding (positive FAST), but opening the retroperitoneum during laparotomy can release the tamponade effect and worsen pelvic bleeding.

Question 22

In which of the following scenarios is prophylactic in situ pinning of the contralateral, asymptomatic hip most strongly indicated in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial for idiopathic cases but is highly recommended in patients with endocrine disorders (e.g., hypothyroidism, renal osteodystrophy, hyperparathyroidism, growth hormone deficiency) or prior radiation therapy. These patients have a significantly higher risk (up to 100% in some metabolic conditions) of developing a contralateral slip compared to those with idiopathic SCFE.

Question 23

A 55-year-old active male undergoes a total hip arthroplasty utilizing a ceramic-on-ceramic bearing. Two years postoperatively, he complains of a high-pitched squeaking noise during his gait cycle, though he has no pain. Which of the following factors is most strongly associated with the development of this phenomenon?





Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is a well-documented phenomenon. It is most strongly associated with edge loading of the ceramic components, which leads to stripe wear, loss of fluid film lubrication, and subsequent micro-separation and resonance. Edge loading is frequently the result of suboptimal component positioning (e.g., excessive abduction, or extremes of anteversion/retroversion). Other risk factors include younger patient age, taller height, and heavier weight, but stripe wear/edge loading is the primary mechanical cause.

Question 24

A 45-year-old manual laborer presents with advanced Kienböck's disease, classified as Lichtman Stage IIIB. He is being evaluated for a proximal row carpectomy (PRC). Which of the following radiographic findings represents an absolute contraindication to performing a PRC?





Explanation

Proximal row carpectomy (PRC) involves excising the scaphoid, lunate, and triquetrum, allowing the capitate to articulate with the lunate fossa of the radius. Therefore, the articular surfaces of the proximal capitate and the lunate fossa of the distal radius must be preserved. Advanced degeneration of the capitate head or the lunate fossa is an absolute contraindication to PRC, and such patients are better managed with a scaphoid excision and four-corner fusion or total wrist arthrodesis.

Question 25

An 11-year-old male with widely open physes sustains a mid-substance anterior cruciate ligament (ACL) tear. To avoid physeal injury, an all-epiphyseal ACL reconstruction is planned. During preparation of the femoral tunnel, the starting point should be correctly established in which of the following locations?





Explanation

An all-epiphyseal ACL reconstruction is designed to completely avoid crossing the distal femoral and proximal tibial physes. On the femoral side, the tunnel is drilled strictly within the epiphysis, distal to the lateral femoral physis. The trajectory goes from the lateral aspect of the lateral femoral condyle, aiming medially toward the native ACL footprint on the inner wall of the lateral condyle, remaining entirely within the epiphyseal bone.

Question 26

An 80-year-old male sustains a Type II odontoid fracture following a ground-level fall. Which of the following initial injury characteristics is most predictive of nonunion if this fracture is treated nonoperatively with a rigid cervical orthosis?





Explanation

In Type II odontoid fractures, the highest risk factors for nonunion with conservative management include initial fracture displacement > 5 mm (or 6 mm in some series), angulation > 10 degrees, and advanced patient age (especially > 50-65 years). Among these, displacement > 5 mm has been consistently shown to have the highest correlation with nonunion, with rates exceeding 50-80% in older adults when displacement is severe.

Question 27

Bone morphogenetic proteins (BMPs) play a crucial role in inducing osteoblastic differentiation of mesenchymal stem cells. Which of the following intracellular signaling molecules is directly phosphorylated following BMP binding to its cell-surface serine/threonine kinase receptor?





Explanation

Bone morphogenetic proteins (BMPs) belong to the TGF-beta superfamily. When BMP binds to its serine/threonine kinase receptor, it phosphorylates receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. These phosphorylated Smads then form a complex with the common-partner Smad (Co-Smad), Smad 4, and translocate to the nucleus to regulate gene transcription. In contrast, TGF-beta primarily phosphorylates Smad 2 and 3.

Question 28

A 28-year-old male presents with a deep, slow-growing soft tissue mass in the popliteal fossa. Excisional biopsy confirms a biphasic tumor with both epithelial and spindle cell components. Which of the following cytogenetic abnormalities is classically associated with this diagnosis?





Explanation

The diagnosis is synovial sarcoma, which classicially presents as a deep soft tissue mass near a joint (often the knee/popliteal fossa) in young adults. Histologically, it can be biphasic (epithelial and spindle cells) or monophasic. It is characterized by the t(X;18)(p11;q11) chromosomal translocation, which results in the SYT-SSX fusion gene. t(11;22) is Ewing sarcoma; t(12;16) is myxoid liposarcoma; t(2;13) is alveolar rhabdomyosarcoma; t(9;22) is extraskeletal myxoid chondrosarcoma (and CML).

Question 29

When comparing operative repair to nonoperative management for acute Achilles tendon ruptures, high-quality meta-analyses have demonstrated that operative management is associated with which of the following outcomes?





Explanation

Meta-analyses of acute Achilles tendon ruptures indicate that operative repair significantly decreases the rerupture rate when compared to traditional nonoperative management involving prolonged cast immobilization. However, when nonoperative management includes early functional rehabilitation, the difference in rerupture rates between the two groups is not statistically significant. Operative repair consistently carries a higher rate of overall complications, specifically wound-related and soft-tissue issues. Differences in return to sport and long-term strength are often negligible when functional rehab is used.

Question 30

During an olecranon osteotomy for open reduction and internal fixation of an intra-articular distal humerus fracture (AO/OTA 13-C3), the osteotomy should be directed to enter the joint at which of the following landmarks?





Explanation

An olecranon osteotomy is typically performed as a chevron osteotomy directed into the 'bare area' of the greater sigmoid (trochlear) notch. This bare area is devoid of articular cartilage and represents the deepest portion of the notch. Entering the joint here minimizes damage to the articular surface of the proximal ulna and facilitates an anatomic reduction upon repair.

Question 31

A 40-year-old male sustains a bicondylar tibial plateau fracture (Schatzker VI). Preoperative CT scanning reveals a large, displaced posteromedial shear fragment. Which of the following surgical approaches is most appropriate for achieving direct visualization and applying a buttress plate to this specific fragment?





Explanation

The posteromedial shear fragment is common in bicondylar tibial plateau fractures. To adequately reduce and buttress this fragment, an anti-glide or buttress plate must be applied to the posterior aspect of the medial plateau. The optimal approach is the posteromedial approach, which exploits the interval between the medial head of the gastrocnemius (retracted posteriorly/laterally) and the pes anserinus tendons (retracted anteriorly/medially).

Question 32

A 6-week-old female infant is undergoing treatment with a Pavlik harness for a dislocated left hip (Graf Type IV). During a routine follow-up, the parents note the infant is not kicking the left leg as much. On examination, there is decreased active extension of the left knee, though the infant cries and withdraws when the heel is stimulated. What is the most likely cause of this finding?





Explanation

Femoral nerve palsy is a well-known complication of Pavlik harness treatment, usually caused by excessive hip flexion (typically > 100-120 degrees) which places traction on or compresses the femoral nerve against the pelvis. It presents as an inability or decreased tendency to actively extend the knee. The management is to temporarily remove the harness or adjust the flexion straps to a less flexed position. The nerve palsy almost always resolves spontaneously once the tension is relieved.

Question 33

A patient undergoes revision of a total hip arthroplasty composed of a titanium alloy stem and a modular cobalt-chromium femoral head. The revision is performed for an adverse local tissue reaction (ALTR) secondary to metallosis. The primary mechanism of metal degradation at the modular head-neck junction in this scenario is classified as:





Explanation

Corrosion at the modular head-neck taper junction (trunnionosis) is primarily caused by mechanically assisted crevice corrosion, commonly referred to as fretting corrosion. Micromotion between the head and the neck disrupts the protective passivation layer of the metals, exposing raw metal to the body fluid environment (crevice corrosion), which accelerates the release of metal ions and debris, leading to ALTR.

Question 34

During a primary posterior-stabilized total knee arthroplasty, after making the initial measured bone cuts and inserting trial components, the surgeon assesses the gaps. The knee is found to be symmetrically tight in both full extension and 90 degrees of flexion, while the coronal alignment is neutral. Which of the following is the most appropriate next step to achieve balanced gaps?





Explanation

Gap balancing in TKA requires understanding which cuts affect which gaps. The proximal tibial cut affects both the flexion and extension gaps equally. If a knee is symmetrically tight in both flexion and extension, the solution is to increase both gaps simultaneously by resecting more bone from the proximal tibia, or by using a thinner polyethylene insert. Resecting more distal femur would only increase the extension gap. Upsizing the femur would tighten the flexion gap.

Question 35

A 50-year-old female presents with the sudden onset of medial knee pain and a popping sensation while performing a deep squat. MRI reveals a complete radial tear of the posterior horn of the medial meniscus exactly at its root attachment. Biomechanically, this injury is equivalent to which of the following conditions?





Explanation

A complete tear of the meniscal root disrupts the circumferential hoop stresses that allow the meniscus to convert axial loads into tensile stresses. Biomechanically, a complete posterior root tear renders the meniscus completely nonfunctional, leading to contact pressures and joint kinematics that are equivalent to a total meniscectomy. This results in accelerated articular cartilage wear and rapid progression of osteoarthritis.

Question 36

A 65-year-old male complains of bilateral leg pain, heaviness, and cramping that worsens with walking. The symptoms are relieved by sitting or leaning forward over a shopping cart. Which of the following clinical features is most characteristic of his likely diagnosis when differentiating it from vascular claudication?





Explanation

The patient's presentation is classic for neurogenic claudication secondary to lumbar spinal stenosis (relief with lumbar flexion). Neurogenic claudication typically radiates in a proximal-to-distal direction (buttocks/thighs to calves), whereas vascular claudication typically begins distally in the calf and progresses proximally. Additionally, vascular claudication is relieved by merely standing stationary, whereas neurogenic requires sitting or lumbar flexion. Riding a stationary bike flexes the spine and preserves exercise tolerance in neurogenic claudication, but exacerbates vascular claudication due to increased metabolic demand.

Question 37

A 55-year-old male with poorly controlled diabetes mellitus presents with a swollen, erythematous, and warm left foot without skin ulceration. Radiographs reveal fragmentation of the midfoot with subluxation of the tarsometatarsal joints, bony debris, and no signs of consolidation. According to the Eichenholtz classification, what stage is this, and what is the best initial orthopedic management?





Explanation

The patient has acute Charcot arthropathy. The Eichenholtz classification categorizes this as Stage 1 (Developmental/Fragmentation stage), which is characterized clinically by a red, hot, swollen foot and radiographically by bone fragmentation, joint subluxation/dislocation, and debris. The standard of care for acute Stage 1 Charcot is offloading with a total contact cast (TCC) and non-weight-bearing to arrest the destructive process and prevent further deformity until the foot reaches Stage 2 (Coalescence) and Stage 3 (Consolidation).

Question 38

The primary intrinsic blood supply to the flexor tendons within Zone II of the hand is provided by the vincula tendinum. Which of the following vascular structures directly supplies the vincula in this anatomical region?





Explanation

Within the fibro-osseous digital sheath (Zone II), the flexor tendons receive their blood supply intrinsically via the vincula tendinum (vincula brevia and longa) and extrinsically via synovial diffusion. The vincula are supplied by transverse communicating branches that arise directly from the proper digital arteries.

Question 39

A 12-year-old boy is evaluated for a Volkmann's ischemic contracture, which developed following an unrecognized compartment syndrome of the forearm after a supracondylar humerus fracture. Which of the following muscles is typically the most severely affected by ischemia in this condition?





Explanation

Volkmann's ischemic contracture is the late sequela of an untreated volar compartment syndrome of the forearm. The deepest muscles of the volar compartment, specifically the flexor digitorum profundus (FDP, especially to the middle and ring fingers) and the flexor pollicis longus (FPL), lie directly against the bone and are subjected to the highest intracompartmental pressures. Consequently, they suffer the most severe ischemic necrosis and subsequent fibrotic contracture.

Question 40

A 22-year-old male presents with chronic, dull back pain that is worsened at night. He reports the pain is poorly relieved by aspirin. Radiographs and CT scan reveal a 2.5 cm radiolucent lesion with a sclerotic margin located in the posterior elements of the L3 vertebra. What is the most likely diagnosis?





Explanation

Osteoblastoma and osteoid osteoma share similar histological features but are differentiated primarily by size and clinical presentation. Osteoblastomas are typically larger than 2.0 cm (while osteoid osteomas are < 1.5 - 2 cm). Osteoblastomas have a strong predilection for the posterior elements of the spine and produce pain that is less characteristically nocturnal and less dramatically responsive to NSAIDs or aspirin compared to osteoid osteoma.

Question 41

A surgeon revises a failed hip arthroplasty and notices significant corrosion at the modular head-neck junction. The femoral stem is titanium alloy and the femoral head is cobalt-chromium. Which of the following best describes the primary mechanism of galvanic corrosion in this setting?





Explanation

Galvanic corrosion occurs when two dissimilar metals (e.g., Titanium and Cobalt-Chromium) are in contact within an electrolyte solution (body fluid). Fretting (micro-motion) disrupts the protective oxide (passivation) layer, accelerating the electrochemical dissolution of the less noble metal.

Question 42

A 13-year-old girl sustains an ankle injury. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibia. Which of the following best describes the anatomical basis for this specific fracture pattern?





Explanation

The distal tibial physis closes in a specific predictable pattern: central, then posteromedial, then anteromedial, and finally anterolateral. Because the anterolateral portion is the last to close (fuse), it is susceptible to avulsion via the anterior inferior tibiofibular ligament (AITFL) resulting in a juvenile Tillaux fracture.

Question 43

A 24-year-old man is involved in an MVA. Imaging shows a traumatic spondylolisthesis of the axis (Hangman's fracture) with severe angulation and >5mm of translation of C2 on C3. The C2-C3 facet joints are dislocated bilaterally. According to the Levine and Edwards classification, what is the injury type and its recommended primary treatment?





Explanation

This is a Type III Hangman fracture (pars interarticularis fractures with bilateral C2-C3 facet dislocations). Traction is contraindicated as it may exacerbate the dislocation or cause neurologic injury. The recommended treatment for Type III is open reduction and internal fixation.

Question 44

A 35-year-old cyclist falls and sustains a closed degloving injury over the greater trochanter. Two weeks later, a fluctuant swelling is present. Aspiration yields serosanguinous fluid. What is the pathophysiological hallmark of this lesion?





Explanation

A Morel-Lavallée lesion is a closed degloving injury caused by shearing forces that separate the skin and subcutaneous fat from the underlying deep fascia. This creates a potential space that fills with blood, lymph, and necrotic fat.

Question 45

In modern total hip arthroplasty, highly cross-linked polyethylene (HXLPE) has significantly reduced wear rates compared to conventional polyethylene. Which of the following manufacturing processes is utilized to eliminate free radicals and improve the oxidation resistance of HXLPE?





Explanation

Irradiation is used to induce cross-linking in polyethylene, which improves wear resistance but generates free radicals that can lead to oxidation and degradation. To eliminate these free radicals, the polyethylene is either remelted (heated above its melting point) or annealed (heated just below its melting point) or infused with an antioxidant like Vitamin E.

Question 46

A patient undergoes primary repair of a flexor digitorum profundus (FDP) laceration in the middle finger. Postoperatively, the patient demonstrates an inability to make a full composite fist, specifically showing limited active flexion of the index, ring, and small fingers. What is the most likely cause?





Explanation

The Quadrigia effect occurs when the FDP tendon of one finger is advanced too far (typically >1 cm) during repair. Because the FDP tendons to the middle, ring, and small fingers share a common muscle belly, overtensioning one restricts the excursion of the others, leading to a decreased grip strength and incomplete active flexion of the uninjured digits.

Question 47

A 22-year-old football player sustains a hyperplantarflexion injury to his midfoot. AP radiograph demonstrates a "fleck sign". This bony avulsion is most classically associated with the attachment of the Lisfranc ligament to which of the following structures?





Explanation

The "fleck sign" represents a bony avulsion of the Lisfranc ligament. The Lisfranc ligament connects the medial cuneiform to the base of the second metatarsal. The avulsion typically occurs at the base of the second metatarsal.

Question 48

A 30-year-old male presents with chronic anterior leg pain. Radiographs reveal a multi-loculated, eccentric, osteolytic lesion in the anterior cortex of the tibial diaphysis. Biopsy reveals islands of epithelial cells in a fibrous stroma. What is the most appropriate definitive management?





Explanation

The clinical, radiographic, and histological findings describe an adamantinoma, a low-grade malignant bone tumor that almost exclusively occurs in the anterior tibial cortex. It does not respond well to radiation or chemotherapy. The standard treatment is wide surgical resection to prevent local recurrence.

Question 49

A patient with a multi-ligamentous knee injury undergoes a dial test. There is >10 degrees of increased external rotation on the injured side compared to the normal side at 30 degrees of knee flexion, but symmetrical external rotation at 90 degrees of knee flexion. Which structure is isolated as injured?





Explanation

In the dial test, increased external rotation at 30 degrees only indicates an isolated posterolateral corner (PLC) injury. If increased external rotation is present at both 30 degrees and 90 degrees, it indicates a combined PLC and posterior cruciate ligament (PCL) injury.

Question 50

A 28-year-old male sustains a high-energy vertical shear fracture of the femoral neck (Pauwels Type III). What biomechanical characteristic of this fracture makes it at highest risk for nonunion, and how is it optimally addressed during internal fixation?





Explanation

Pauwels Type III femoral neck fractures have a high fracture angle (>50 degrees), which subjects the fracture site to high vertical shear and varus forces. This increases the risk of nonunion and fixation failure. They are biomechanically best stabilized with a fixed-angle device like a sliding hip screw (often with a derotational screw) rather than multiple cancellous screws alone, which are prone to fail under shear.

Question 51

Bone morphogenetic proteins (BMPs) are essential for bone healing. They initiate intracellular signaling primarily by binding to transmembrane receptors. Which of the following intracellular signaling molecules is directly phosphorylated following BMP receptor activation?





Explanation

BMPs belong to the TGF-beta superfamily. When they bind to their serine/threonine kinase cell surface receptors, they cause phosphorylation and activation of receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. These complex with Smad 4 to enter the nucleus and regulate gene transcription for osteoblast differentiation.

Question 52

An 11-year-old obese boy is diagnosed with a unilateral, stable slipped capital femoral epiphysis (SCFE). Prophylactic pinning of the contralateral asymptomatic hip is being considered. Which of the following factors most strongly increases the risk of a contralateral slip and supports the decision for prophylactic pinning?





Explanation

Patients with an initial SCFE have a significant risk of contralateral slip (up to 20-60%). The risk is highest in patients with endocrine disorders (e.g., hypothyroidism) and those with significant remaining growth. An open triradiate cartilage indicates significant skeletal immaturity and remaining growth, representing a strong predictor for subsequent contralateral slip, thus often serving as a relative indication for prophylactic pinning.

Question 53

A 32-year-old female presents with chronic, firm, brawny dorsal edema over the metacarpals of her right hand. She reports it started after a minor contusion 6 months ago. Extensive investigations are negative for infection, inflammatory arthropathy, and complex regional pain syndrome. What is the most likely diagnosis, and what is the best initial management?





Explanation

Secretan's syndrome is a factitious condition characterized by chronic, firm, brawny edema over the dorsum of the hand, usually self-inflicted by repetitive blunt trauma or applying tourniquets. Treatment is conservative, including psychiatric evaluation, casting, and avoiding surgical intervention, which often worsens the condition or fails.

Question 54

A 65-year-old male complains of bilateral leg pain and cramping that worsens with walking. You are attempting to differentiate neurogenic claudication from vascular claudication. Which of the following historical features or physical exam findings is most specific for neurogenic claudication?





Explanation

Neurogenic claudication (due to lumbar spinal stenosis) is classically relieved by spinal flexion (e.g., leaning forward on a shopping cart or sitting), as this posture increases the cross-sectional area of the spinal canal and neural foramina. Walking uphill is also better tolerated because it requires a flexed posture, unlike vascular claudication, which worsens with the increased metabolic demand of walking uphill.

Question 55

A 55-year-old woman with a metal-on-metal total hip arthroplasty presents with new-onset groin pain 5 years postoperatively. Metal artifact reduction sequence (MARS) MRI demonstrates a large, thick-walled cystic mass communicating with the joint space. Serum cobalt and chromium levels are significantly elevated. Which histological feature is most characteristic of the tissue surrounding this adverse local tissue reaction (ALTR)?





Explanation

Adverse local tissue reactions (ALTR) or aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) in metal-on-metal implants are characterized histologically by a delayed Type IV hypersensitivity reaction. This manifests as extensive perivascular lymphocytic infiltration, macrophage accumulation, and tissue necrosis.

Question 56

A 58-year-old patient with poorly controlled diabetes mellitus presents with a swollen, warm, and erythematous right foot. Radiographs demonstrate periarticular osteopenia, fragmentation of the navicular, and subluxation of the tarsometatarsal joints. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent and what is the hallmark of the subsequent stage?





Explanation

Eichenholtz Stage 1 (Development/Fragmentation stage) is characterized by acute inflammation, osteopenia, bone fragmentation, and joint subluxation/dislocation. The next stage, Stage 2 (Coalescence stage), is characterized by a decrease in inflammation, absorption of fine debris, and early bony consolidation/sclerosis.

Question 57

A 15-year-old male undergoes neoadjuvant chemotherapy followed by wide resection of an osteosarcoma of the distal femur. Histopathologic analysis of the resected tumor specimen is performed. Which of the following findings is considered the single most important prognostic factor for long-term survival in this patient?





Explanation

The percentage of tumor necrosis following neoadjuvant chemotherapy (evaluated by mapping the resected specimen, classically graded by the Huvos system) is the most significant prognostic factor for long-term survival in conventional osteosarcoma. A good response is defined as >90% necrosis. While margins and skip lesions are important, tumor necrosis percentage is the classic primary prognostic indicator evaluated post-resection.

Question 58

An orthopedic surgeon is performing an open repair of a severe medial-sided knee injury. The surgeon identifies the superficial medial collateral ligament (sMCL) and the posterior oblique ligament (POL). What is the primary functional difference in knee stability provided by these two structures?





Explanation

The superficial MCL is the primary restraint to valgus stress and is best tested at 30 degrees of knee flexion, where it is taut. The posterior oblique ligament (POL), which is a thickening of the posteromedial capsule, is tightest in full extension and provides resistance against valgus and external rotation forces in extension.

Question 59

Tendon healing progresses through overlapping phases: inflammatory, proliferative (fibroblastic), and remodeling. During the remodeling phase, what is the primary change in the composition of the extracellular matrix that contributes to increased tensile strength?





Explanation

During the early stages of tendon healing (proliferative phase), fibroblasts lay down predominantly Type III collagen, which is disorganized and mechanically weak. During the remodeling phase, Type III collagen is gradually replaced by Type I collagen, which organizes into parallel bundles along the axis of tension, significantly increasing the tendon's tensile strength.

Question 60

A 32-year-old male sustains a spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture). On presentation, he is found to have a complete radial nerve palsy. Closed reduction and functional bracing are selected as the initial treatment. What is the most widely accepted indication for surgical exploration of the radial nerve in this scenario?





Explanation

Primary radial nerve palsy in closed humeral shaft fractures is typically treated expectantly, as >85% recover spontaneously (mostly neuropraxia or axonotmesis). However, a radial nerve palsy that develops after a closed reduction attempt suggests the nerve may have become entrapped in the fracture site, which is a widely accepted absolute indication for immediate surgical exploration. Another indication is failure of spontaneous recovery by 3-6 months.

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