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Arab Orthopaedic Board MCQs - Part 28

27 Apr 2026 114 min read 82 Views
Arab Ortho Board MCQs - Part 27

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This article provides essential research regarding Arab Orthopaedic Board MCQs - Part 28. Practice Arab Orthopaedic Board MCQs Part 28. Review orthopedic surgery questions 1351 to 1400 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 28

Comprehensive 100-Question Exam


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Question 1

During the anterior approach to the pelvis (ilioinguinal approach) for fixation of an acetabular fracture, significant hemorrhage occurs near the superior pubic ramus. This is most likely due to injury of an anastomotic vessel connecting which two arterial systems?





Explanation

The corona mortis is a vascular anastomosis between the external iliac system (or inferior epigastric) and the obturator system. It is located on the posterior aspect of the superior pubic ramus and is highly susceptible to injury during an anterior pelvic approach, leading to significant, difficult-to-control hemorrhage.

Question 2

A 65-year-old male presents with new-onset groin pain 6 years after an uncomplicated primary metal-on-polyethylene total hip arthroplasty utilizing a large diameter modular femoral head. Radiographs show well-fixed components in acceptable alignment. Inflammatory markers are normal. Metal Artifact Reduction Sequence (MARS) MRI reveals a large cystic mass adjacent to the greater trochanter. What is the most likely diagnosis?





Explanation

The patient has an adverse local tissue reaction (ALTR) resulting from mechanically assisted crevice corrosion at the modular head-neck junction, known as trunnionosis. This can occur even in metal-on-polyethylene articulations, particularly when a large diameter head is used, as it increases the torque and fretting corrosion at the trunnion.

Question 3

An infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. Hyperflexion of the hips beyond 120 degrees in the harness is most commonly associated with which of the following complications?





Explanation

Hyperflexion of the hip in a Pavlik harness risks compression of the femoral nerve against the inguinal ligament, leading to femoral nerve palsy. Excessive abduction, on the other hand, significantly increases the risk of avascular necrosis of the femoral head.

Question 4

Which of the following factors is the strongest predictor of nonunion in a 75-year-old patient with a Type II odontoid fracture treated conservatively in a halo vest?





Explanation

Risk factors for nonunion in Type II odontoid fractures include age over 65 years, initial displacement > 5 mm, posterior displacement, and angulation > 10 degrees. Initial fracture displacement greater than 5 mm and advanced age are the strongest independent predictors of failure with conservative management.

Question 5

In anterior cruciate ligament (ACL) reconstruction, the addition of an anterolateral ligament (ALL) reconstruction or lateral extra-articular tenodesis (LET) is primarily indicated to control which biomechanical parameter?





Explanation

The anterolateral ligament (ALL) and lateral extra-articular structures act as secondary stabilizers to anterior tibial translation but are primary stabilizers against internal tibial rotation. Reconstructing these structures is indicated in high-risk patients to help control the pivot-shift phenomenon.

Question 6

The primary blood supply to the proximal pole of the scaphoid is derived from vessels that enter the bone at which location?





Explanation

The major blood supply to the scaphoid is from the radial artery. Approximately 80% of the bone, including the entire proximal pole, is supplied by branches that enter the dorsal ridge (distal to the waist) and flow retrogradely. This retrograde vascular supply explains the high rate of avascular necrosis and nonunion in proximal pole fractures.

Question 7

A 16-year-old male undergoes wide surgical resection for a conventional high-grade osteosarcoma of the distal femur following a course of neoadjuvant chemotherapy. Pathologic analysis of the resected specimen reveals 95% tumor necrosis. This histological finding is the most reliable predictor for which of the following?





Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the single most important prognostic factor for overall survival in patients with osteosarcoma. A necrosis rate of > 90% is classified as a 'good response' and is correlated with significantly improved overall survival.

Question 8

A 24-year-old professional athlete sustains a purely ligamentous Lisfranc injury. Based on prospective randomized trials comparing open reduction internal fixation (ORIF) to primary arthrodesis for purely ligamentous Lisfranc injuries, primary arthrodesis is associated with:





Explanation

Studies (such as Ly and Coetzee, JBJS 2006) demonstrate that for purely ligamentous Lisfranc injuries, primary arthrodesis of the medial 2 or 3 rays yields better functional outcomes and avoids the frequent need for secondary fusion due to post-traumatic arthritis or hardware removal associated with ORIF.

Question 9

According to Perren's strain theory of bone healing, primary (contact) bone healing without callus formation requires the interfragmentary strain to be maintained below what threshold?





Explanation

Perren's strain theory posits that absolute stability is required for primary bone healing, meaning the interfragmentary strain must be maintained below 2%. Secondary bone healing (with callus formation) occurs in environments with relative stability, where strain is between 2% and 10%. Strains above 10% result in nonunion or fibrous tissue formation.

Question 10

Prophylactic pinning of the contralateral asymptomatic hip in a patient with a unilateral Slipped Capital Femoral Epiphysis (SCFE) is most strongly indicated in which of the following scenarios?





Explanation

Prophylactic pinning of the contralateral hip is indicated in patients at high risk for a subsequent contralateral slip. Risk factors include underlying endocrine disorders (e.g., panhypopituitarism, hypothyroidism, renal osteodystrophy), prior radiation therapy, and atypical age of presentation (younger than 10 or older than 16 years).

Question 11

When utilizing a volar locking plate for fixation of a distal radius fracture, placement of the plate at or distal to the watershed line significantly increases the risk of rupture of which tendon?





Explanation

The watershed line is a transverse anatomical ridge on the volar margin of the distal radius. Plate prominence at or distal to this line causes attritional wear on the flexor pollicis longus (FPL) tendon due to its immediate proximity as it courses over the distal radius, leading to a high risk of iatrogenic rupture.

Question 12

During a posterior-stabilized total knee arthroplasty (TKA), the surgeon trials the components and notes that the knee is well-balanced in full extension but excessively tight in 90 degrees of flexion. Which of the following is the most appropriate next step to balance the knee?





Explanation

A tight flexion gap with a balanced extension gap implies that the anteroposterior dimension of the femoral component, specifically the posterior condyles, is too large. Downsizing the femoral component using a posterior referencing system will decrease the posterior condylar offset, thereby enlarging the flexion gap without affecting the extension gap.

Question 13

In the Ponseti method for the treatment of congenital idiopathic clubfoot, the sequence of correction of the deformities is strictly protocolized. Which deformity is corrected last, and how is it typically addressed?





Explanation

The acronym CAVE dictates the specific order of correction in the Ponseti method: Cavus, Adductus, Varus, and Equinus. Equinus is the final deformity to be corrected. Because the Achilles tendon is typically very tight and thick, correction usually requires a percutaneous Achilles tenotomy before the final cast is applied.

Question 14

Biomechanical studies of flexor tendon repairs in Zone II demonstrate that the ultimate tensile strength of the repair before gap formation is most directly proportional to:





Explanation

The tensile strength of a flexor tendon repair is directly proportional to the number of core suture strands that cross the repair site. Modern protocols utilizing early active motion favor 4-strand or 6-strand repairs to provide adequate strength and prevent gap formation or frank rupture during rehabilitation.

Question 15

Denosumab, a monoclonal antibody used in the treatment of recurrent or unresectable Giant Cell Tumor (GCT) of bone, exerts its therapeutic effect by targeting which of the following?





Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to and inhibits RANKL. By blocking RANKL, denosumab prevents the interaction with RANK receptors on the surface of osteoclast-like giant cells and their precursors, thereby profoundly inhibiting osteoclastogenesis and the severe osteolysis characteristic of GCT.

Question 16

In a patient with recurrent anterior shoulder instability, a 'remplissage' procedure is indicated for a specific type of bony defect. This procedure involves the capsulotenodesis of which structure into the humeral defect?





Explanation

Remplissage (French for 'filling in') is an adjunctive procedure to an anterior Bankart repair for an engaging (off-track) Hill-Sachs lesion. It involves the tenodesis of the posterior capsule and infraspinatus tendon into the posterolateral humeral head defect, rendering it extra-articular and preventing it from engaging the anterior glenoid rim during external rotation and abduction.

Question 17

A 45-year-old male sustains a high-energy Schatzker Type IV tibial plateau fracture with a large posteromedial coronal shear fragment. To properly neutralize the vertical shear forces during weight bearing, which of the following is the most biomechanically sound fixation strategy?





Explanation

A posteromedial shear fragment in a tibial plateau fracture possesses a coronal fracture line and displaces vertically under physiological load. A laterally based locking plate alone cannot adequately resist these shear forces. The most stable construct is an anatomically contoured buttress plate applied directly to the posteromedial apex via a posteromedial approach.

Question 18

Articular cartilage is highly specialized to resist compressive forces. Which structural component of the extracellular matrix is primarily responsible for drawing water into the cartilage to provide this compressive stiffness via the Donnan osmotic effect?





Explanation

Aggrecan is the predominant proteoglycan in articular cartilage. Its highly negatively charged glycosaminoglycan (GAG) side chains attract cations (like Na+), which in turn draw water into the tissue through the Donnan osmotic effect. This swelling pressure, contained by the Type II collagen tensile network, provides cartilage with its high compressive stiffness.

Question 19

A 32-year-old manual laborer presents with a swollen, painful index finger three days after a minor puncture wound. He exhibits Kanavel's four cardinal signs of flexor tenosynovitis. Which of these signs is considered the earliest and most sensitive indicator of this condition?





Explanation

Kanavel's four cardinal signs of purulent flexor tenosynovitis are: 1) fusiform swelling, 2) resting flexed posture, 3) tenderness along the flexor sheath, and 4) pain with passive extension. Clinical consensus defines pain with passive extension as the most sensitive and earliest clinical sign of tenosynovitis.

Question 20

In the operative treatment of intertrochanteric hip fractures with a sliding hip screw or a cephalomedullary nail, the concept of Tip-Apex Distance (TAD) as described by Baumgaertner is critical. To minimize the risk of lag screw cut-out, the combined TAD (measured on AP and lateral radiographs) should be less than:





Explanation

Baumgaertner et al. demonstrated that a Tip-Apex Distance (TAD) of less than 25 mm is a strong, independent predictor of successful lag screw fixation in intertrochanteric hip fractures. A combined TAD greater than 25 mm significantly increases the risk of the screw cutting out of the femoral head.

Question 21

During anterior pelvic ring surgery via a Pfannenstiel approach, significant bleeding is encountered posterior to the superior pubic ramus. Which two vessels form the most common anastomosis responsible for this bleeding (Corona Mortis)?





Explanation

The Corona Mortis is a vascular anastomosis between the external iliac system (typically the inferior epigastric artery or vein) and the internal iliac system (obturator artery or vein). It crosses over the superior pubic ramus and is highly susceptible to iatrogenic injury during anterior pelvic approaches.

Question 22

During a total knee arthroplasty, the surgeon notes that the knee is well-balanced in full extension, but the flexion gap is excessively tight both medially and laterally. What is the most appropriate next step to balance the knee?





Explanation

A tight flexion gap with a balanced extension gap indicates the posterior condyles are too prominent or the space is too small in flexion. Decreasing the anteroposterior (AP) size of the femoral component increases the flexion gap without affecting the extension gap. Increasing posterior tibial slope or recessing the PCL (if retaining) are alternative solutions.

Question 23

An 11-year-old girl with renal osteodystrophy presents with a symptomatic left slipped capital femoral epiphysis (SCFE). Radiographs confirm a moderate slipped epiphysis on the left. The right hip is currently asymptomatic and radiographically normal. What is the most appropriate management of the right hip?





Explanation

Prophylactic pinning of the contralateral asymptomatic hip is highly recommended in patients with endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy) and those who have undergone previous pelvic radiation, due to an exceedingly high risk (approaching 50-100%) of developing a subsequent slip.

Question 24

A 24-year-old male sustains a traumatic knee dislocation. Following closed reduction, the knee is splinted. His ankle-brachial index (ABI) is measured at 0.85. Palpable distal pulses are present. What is the most appropriate next step in management?





Explanation

In the setting of a knee dislocation, an ABI less than 0.9 is a strong indicator of a potential vascular injury, even if pulses are palpable. A CT angiogram is the gold standard next step to evaluate the popliteal artery and determine if surgical intervention is necessary.

Question 25

Which of the following combinations of orthopedic implant materials is most likely to result in significant galvanic corrosion when placed in direct contact within the human body?





Explanation

Galvanic corrosion occurs when two dissimilar metals are in direct contact within an electrolytic environment. Stainless steel and titanium have significantly different galvanic potentials, making this combination highly susceptible to severe galvanic corrosion and clinical failure, thus it should be strictly avoided.

Question 26

A 35-year-old male sustains a C2 traumatic spondylolisthesis (Hangman's fracture). Imaging reveals a fracture through the pars interarticularis with severe angulation, but minimal translation. The C2-C3 disc space is widened posteriorly. Based on the Levine and Edwards classification, what is the mechanism of injury and the appropriate initial treatment?





Explanation

A Levine and Edwards Type IIA Hangman's fracture features severe angulation with minimal translation and a widened posterior C2-C3 disc space. The mechanism is flexion-distraction. Traction is contraindicated as it exacerbates displacement. Treatment is halo application in slight compression and extension to close the posterior hinge.

Question 27

A 32-year-old manual laborer presents with chronic dorsal wrist pain. Radiographs demonstrate sclerosis of the lunate with coronal fracture lines, but no carpal collapse. Ulnar variance is negative 3mm. According to the Lichtman classification, what is the most appropriate surgical treatment?





Explanation

This patient has Lichtman Stage IIIa Kienbock's disease (lunate fragmentation/collapse but no fixed scaphoid rotation or loss of carpal height). In the presence of negative ulnar variance, a joint-leveling procedure (such as a radial shortening osteotomy) is the most reliable treatment to unload the lunate and halt disease progression.

Question 28

A 40-year-old female sustains a high-energy trauma resulting in a distal femur fracture. CT scan reveals a coronal plane fracture of the lateral femoral condyle. What is the eponymous name of this fracture, and what is the optimal direction of screw fixation?





Explanation

A Hoffa fracture is an intra-articular coronal plane fracture of the femoral condyle, typically the lateral condyle. Biomechanical studies have demonstrated that placing lag screws from anterior to posterior (A-P) provides significantly stronger fixation compared to posterior to anterior (P-A), as A-P screws engage the denser bone of the posterior condyle more effectively.

Question 29

An 18-month-old girl presents with a painless limp. Examination reveals a positive Galeazzi sign and asymmetric thigh folds. Radiographs confirm a completely dislocated left hip with an acetabular index of 38 degrees. What is the most appropriate next step in management?





Explanation

In a child aged 18 months or older with Developmental Dysplasia of the Hip (DDH), conservative measures usually fail. Because there is significant acetabular dysplasia (acetabular index of 38 degrees), open reduction combined with a pelvic osteotomy (e.g., Salter or Pemberton) is necessary to improve anterolateral coverage, followed by spica casting.

Question 30

A 65-year-old woman undergoes a total hip arthroplasty via a direct anterior approach. Postoperatively, she complains of numbness and a burning sensation over the anterolateral aspect of her thigh. Which nerve is most likely injured, and between which two muscles does it typically pass near the anterior superior iliac spine?





Explanation

The lateral femoral cutaneous nerve (LFCN) is at highest risk during the direct anterior approach to the hip. It provides sensation to the anterolateral thigh. Anatomically, it typically exits the pelvis medial to the ASIS and courses distally in the interval between the tensor fasciae latae (TFL) and the sartorius muscle.

Question 31

A 14-year-old boy presents with a painful mass in the diaphysis of his left femur. Radiographs show a permeative, destructive lesion with an 'onion-skin' periosteal reaction. A biopsy is performed. Which of the following chromosomal translocations is most characteristic of this diagnosis?





Explanation

The clinical and radiographic presentation is classic for Ewing sarcoma. Ewing sarcoma is characterized by the t(11;22)(q24;q12) chromosomal translocation in approximately 85% of cases, which results in the fusion of the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11.

Question 32

A 55-year-old overweight female presents with progressive flattening of her left foot, medial pain, and inability to perform a single-leg heel rise. Examination shows a flexible hindfoot with significant forefoot abduction (>40% uncoverage of the talonavicular joint). What is the most appropriate surgical management for this Stage IIb adult-acquired flatfoot?





Explanation

Stage IIb posterior tibial tendon dysfunction (adult-acquired flatfoot) is characterized by a flexible deformity with profound forefoot abduction. Surgical correction requires addressing both columns: a medializing calcaneal osteotomy (for hindfoot valgus), lateral column lengthening (e.g., Evans osteotomy for forefoot abduction), and soft tissue reconstruction (FDL transfer).

Question 33

A 29-year-old male sustains a closed, isolated right scapular body fracture following a motorcycle collision. Radiographs and CT show a highly comminuted fracture with 5 mm of displacement. What is the most appropriate management?





Explanation

The vast majority of isolated scapular body fractures, even those that are highly comminuted or displaced up to 1-2 cm, are treated non-operatively with excellent functional outcomes. Sling immobilization for comfort followed by early shoulder range of motion is the standard of care.

Question 34

In normal articular cartilage, which zone contains the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils oriented perpendicular to the articular surface?





Explanation

The deep (radial) zone of articular cartilage is primarily responsible for resisting compressive forces. It is characterized by the highest concentration of proteoglycans, the lowest water content, and thick collagen fibrils oriented perpendicularly to the articular surface, anchoring into the tidemark.

Question 35

A 60-year-old active male is undergoing arthroscopic rotator cuff repair. A subpectoral biceps tenodesis is planned for a concomitantly degenerative long head of the biceps tendon. What is the primary advantage of subpectoral tenodesis compared to an arthroscopic suprapectoral tenodesis?





Explanation

A subpectoral biceps tenodesis places the fixation distal to the bicipital groove. Its primary advantage is the complete removal of the diseased tendon and synovium from the bicipital groove, which is a recognized source of persistent anterior shoulder pain ('groove pain').

Question 36

In the rehabilitation of Zone II flexor tendon repairs, which of the following suturing techniques biomechanically provides the greatest tensile strength and resistance to gap formation during early active motion protocols?





Explanation

The tensile strength and resistance to gap formation of a flexor tendon repair are directly proportional to the number of strands crossing the repair site. A 6-strand core suture combined with a circumferential epitendinous suture provides significantly greater biomechanical strength, allowing for robust early active motion rehabilitation.

Question 37

A 14-year-old gymnast presents with persistent lower back pain exacerbated by extension. Radiographs reveal a Grade II L5-S1 isthmic spondylolisthesis. After 6 months of conservative management including bracing and physical therapy, her pain remains debilitating. What is the most appropriate surgical intervention?





Explanation

In an adolescent with a symptomatic Grade II isthmic spondylolisthesis that has failed conservative management, the standard surgical treatment is an L5-S1 posterior instrumented fusion. Pars repairs are reserved for defects with no significant slip (Grade 0 or early Grade I).

Question 38

A 30-year-old man falls from a height and sustains a Hawkins Type III fracture of the talar neck. Which of the following best describes the anatomical disruption associated with a Hawkins Type III fracture?





Explanation

The Hawkins classification describes talar neck fractures: Type I is non-displaced. Type II involves subluxation or dislocation of the subtalar joint. Type III involves dislocation of both the subtalar and tibiotalar (ankle) joints. Type IV involves dislocation of the subtalar, tibiotalar, and talonavicular joints.

Question 39

A 6-year-old boy falls on an outstretched hand and presents with elbow swelling and pain. Radiographs reveal a plastic deformation of the ulna with an anterior dislocation of the radial head. According to the Bado classification, what type of Monteggia lesion is this?





Explanation

A Monteggia fracture-dislocation is an ulnar shaft fracture (or plastic deformation in children) with a radial head dislocation. Bado Type I features anterior dislocation of the radial head. Type II is posterior, Type III is lateral, and Type IV involves fractures of both the radius and ulna with an anterior radial head dislocation.

Question 40

A 35-year-old female presents with knee pain. Radiographs reveal an eccentric, lytic, epiphyseal lesion in the distal femur extending to the subchondral bone without a sclerotic border. Biopsy confirms Giant Cell Tumor of bone (GCT). If medical management is considered for a locally advanced and unresectable presentation, which medication specifically targets the pathogenesis of this tumor?





Explanation

Giant Cell Tumor (GCT) of bone features neoplastic stromal cells that express RANKL, which recruits osteoclast-like multinucleated giant cells. Denosumab is a monoclonal antibody that binds to RANKL, potently inhibiting this pathway and is used for advanced or unresectable GCT.

Question 41

A resident is utilizing a ring external fixator for limb lengthening. Over the course of several days of continuous fixed distraction, the measurable force required by the tissue to maintain that specific distraction distance progressively decreases. Which viscoelastic property does this phenomenon represent?





Explanation

This scenario describes stress relaxation, a fundamental viscoelastic property of biological tissues. Stress relaxation occurs when a tissue is held at a constant length or strain, and the internal force or stress within the tissue gradually decreases over time. In contrast, creep is the progressive deformation or lengthening of a tissue when subjected to a constant load or stress over time. Hysteresis represents the energy lost (usually as heat) during the loading and unloading cycles of a viscoelastic material.

Question 42

A 14-year-old boy presents with chronic right knee pain. Radiographs reveal an eccentric, heavily calcified, lytic lesion located purely within the epiphysis of the distal femur, surrounded by a thin sclerotic rim. Histological evaluation demonstrates mononuclear cells with longitudinal nuclear grooves and areas of fine, pericellular calcification resembling "chicken-wire." What is the most likely diagnosis?





Explanation

The clinical presentation, radiographic location (epiphyseal), and distinct histology indicate a chondroblastoma. Chondroblastomas are benign, cartilage-producing bone tumors that classically arise in the epiphyses or apophyses of long bones in skeletally immature patients. The pathognomonic histological feature is the presence of "chicken-wire" calcification surrounding mononuclear cells that often have longitudinal nuclear grooves (coffee-bean nuclei). Giant cell tumors can also be epiphyseal but typically occur after growth plate closure and lack the characteristic chicken-wire calcification.

Question 43

During the ilioinguinal approach for an anterior column acetabulum fracture, significant hemorrhage occurs approximately 5 cm lateral to the pubic symphysis, directly on the posterior aspect of the superior pubic ramus. Which vascular anastomosis has most likely been injured?





Explanation

The bleeding source is the corona mortis, which translates to "crown of death." It is a vascular connection between the obturator system (internal iliac system) and the inferior epigastric or external iliac system. It traverses the superior pubic ramus at an average of 5 cm lateral to the pubic symphysis. Given its location and the potential for massive, difficult-to-control intrapelvic hemorrhage, the surgeon must carefully identify and ligate this anastomosis when performing the ilioinguinal or modified Stoppa approaches.

Question 44

During the trial phase of a cruciate-retaining (CR) total knee arthroplasty, the knee is found to be stable and symmetric in extension, but it is unacceptably tight in flexion, causing anterior liftoff of the tibial tray. Assuming the posterior cruciate ligament (PCL) has already been appropriately managed and recessed, what is the best surgical option to balance the knee?





Explanation

A tight flexion gap with a balanced extension gap implies that the space in flexion needs to be selectively increased without altering the extension gap. Increasing the posterior slope of the tibial cut effectively lowers the posterior aspect of the tibia, opening up the flexion gap while having a minimal effect on the extension gap. Resecting more distal femur would exclusively open the extension gap. Upsizing the femoral component would decrease the flexion gap, worsening the problem. Using a thicker insert would tighten both flexion and extension gaps.

Question 45

A 35-year-old male is involved in a high-speed motor vehicle collision. Imaging reveals a traumatic spondylolisthesis of C2 (Hangman's fracture). The fracture passes through the pars interarticularis. Lateral radiographs demonstrate severe anterior angulation of C2 on C3, but with minimal anterior translation. The disc space is disrupted posteriorly. Based on the Levine and Edwards classification, what is the most appropriate initial management?





Explanation

This is a Levine-Edwards Type IIA Hangman's fracture, characterized by severe angulation and minimal translation, typically resulting from a flexion-distraction mechanism. The posterior longitudinal ligament and disc are significantly disrupted. Crucially, longitudinal traction is strongly contraindicated in Type IIA fractures because it will cause over-distraction and potential neurological injury. The correct treatment is gentle compression to reduce the angulation, followed by halo vest immobilization or surgical stabilization if non-operative measures fail.

Question 46

A 22-year-old rugby player presents with an inability to actively flex the distal interphalangeal (DIP) joint of his ring finger after grabbing an opponent's jersey. Ultrasound confirms avulsion of the flexor digitorum profundus (FDP) tendon with retraction of the tendon end into the palm (Zone II). Based on the Leddy and Packer classification, what type of injury is this and what is the optimal surgical timeframe?





Explanation

This is a classic 'Jersey finger' injury. According to the Leddy and Packer classification: Type I involves retraction of the FDP tendon into the palm, which ruptures both the vincula longa and brevia. The tendon loses its blood supply and must be repaired within 7 to 10 days before irreversible tendon retraction and necrosis occur. Type II retracts to the level of the PIP joint (held by the intact vinculum longum) and can be repaired later. Type III involves a large bony avulsion that catches at the A4 pulley.

Question 47

A 12-year-old girl is diagnosed with a unilateral slipped capital femoral epiphysis (SCFE) of the left hip. The parents inquire about the risk to the contralateral, currently asymptomatic right hip. Which of the following patient factors is the strongest predictor of a future contralateral slip and represents the best indication for prophylactic in-situ pinning?





Explanation

The risk of developing a contralateral SCFE is closely linked to skeletal immaturity. An open triradiate cartilage is a well-established and powerful radiographic marker of significant remaining skeletal growth and is one of the strongest predictors for the development of a subsequent contralateral slip. A modified Oxford Bone Age score can also be utilized. While obesity is a risk factor for initial SCFE, bone age/skeletal maturity (e.g., open triradiate cartilage) is the specific metric most heavily weighed when deciding on prophylactic pinning.

Question 48

A 45-year-old patient undergoes an MRI which reveals a complete radial tear at the posterior root insertion of the medial meniscus. If left untreated, what is the primary biomechanical consequence of this specific injury on knee joint dynamics?





Explanation

The meniscal roots anchor the meniscus to the tibial plateau, allowing the meniscus to convert axial compressive loads into circumferential tension, known as "hoop stresses." A complete radial tear at the meniscal root functionally un-anchors the meniscus, resulting in extrusion under load. Biomechanically, a meniscal root tear leads to a complete loss of hoop stresses, drastically increasing peak articular contact pressures in a manner equivalent to a total meniscectomy. This predisposes the patient to rapid progression of osteoarthritis.

Question 49

A 20-year-old collegiate football player sustains a severe midfoot injury. Radiographs and MRI confirm a purely ligamentous Lisfranc injury with lateral displacement of the second through fifth metatarsals. Based on high-level prospective evidence comparing primary arthrodesis versus open reduction and internal fixation (ORIF) for purely ligamentous Lisfranc injuries, primary arthrodesis of which specific joints is recommended to yield superior long-term clinical outcomes?





Explanation

In purely ligamentous Lisfranc injuries, prospective randomized studies (such as those by Ly and Coetzee) have demonstrated that primary arthrodesis of the medial column (1st, 2nd, and 3rd TMT joints) leads to significantly better functional outcomes, less need for hardware removal, and a lower rate of subsequent procedures compared to ORIF. The 4th and 5th TMT joints are highly mobile and are generally pinned with K-wires rather than fused, to preserve their necessary sagittal motion.

Question 50

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction by binding to serine/threonine kinase receptors on mesenchymal stem cells. Following receptor activation, which of the following intracellular signaling molecules are directly phosphorylated and translocated to the nucleus to regulate gene transcription for osteoblast differentiation?





Explanation

The canonical signaling pathway for bone morphogenetic proteins (BMPs) involves binding to type I and type II serine/threonine kinase receptors. This complex directly phosphorylates receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. The phosphorylated R-Smads then form a complex with the co-Smad (Smad 4) and translocate into the nucleus to activate the transcription of osteogenic genes, including Runx2. Wnt signals via Beta-catenin, and RANKL signals via NF-kappa B.

Question 51

During pre-operative planning for a total hip arthroplasty (THA) in a patient with severe protrusio acetabuli, the surgeon considers the effects of acetabular component positioning. Normalizing the center of rotation by lateralizing the acetabular cup out of the protrusio defect will have what direct effect on the biomechanics of the hip joint?





Explanation

The joint reaction force (JRF) across the hip is a function of the body weight lever arm and the abductor lever arm. The center of rotation in a normal hip is located relatively medially. In protrusio, the center of rotation is excessively medialized, which abnormally decreases the body weight lever arm. When the surgeon lateralizes the cup to restore standard anatomic positioning, the distance from the center of gravity (body weight) to the center of rotation is increased. This increases the body weight lever arm, which subsequently increases the overall joint reaction force compared to the protrusio state. (However, restoring anatomy optimizes abductor mechanics and overall gait).

Question 52

A 65-year-old female sustains a displaced 3-part proximal humerus fracture. According to Hertel's criteria, which combination of radiographic features is the most reliable predictor of humeral head ischemia and subsequent avascular necrosis (AVN)?





Explanation

Hertel et al. described highly predictive radiographic criteria for humeral head ischemia in proximal humerus fractures. The most significant predictors for ischemia (AVN risk) are a short calcar segment attached to the articular fragment (metaphyseal extension < 8 mm), a disrupted medial hinge (> 2 mm displacement), and an anatomical neck fracture type. When a short calcar segment and a disrupted medial hinge are combined, the positive predictive value for ischemia is exceptionally high (up to 97%).

Question 53

The Ponseti method is the gold standard for the treatment of idiopathic clubfoot (talipes equinovarus). The deformity is corrected through a series of specific manipulations and serial casting. According to the strictly defined Ponseti protocol, what is the very first component of the deformity that must be addressed and corrected during the first cast?





Explanation

The Ponseti method follows a precise order of correction, often remembered by the acronym CAVE: Cavus, Adduction, Varus, Equinus. The very first step involves correcting the cavus deformity, which is driven by a pronated forefoot relative to the hindfoot. To correct the cavus, the first metatarsal must be elevated (supinating the forefoot) to align it with the midfoot and hindfoot, establishing a normal longitudinal arch before the rest of the deformities are swung outwards.

Question 54

During the physical examination of a 70-year-old male presenting with clumsiness in his hands and broad-based gait, you ask him to fully extend his fingers, and then you observe that the small (ulnar) fingers spontaneously abduct and he is unable to hold them together with the other fingers. This specific finding is known as:





Explanation

The clinical sign described is the 'finger escape sign,' which is a prominent feature of cervical spondylotic myelopathy (often grouped under the broader term 'myelopathy hand'). It occurs due to profound weakness of the intrinsic hand muscles (interossei) caused by upper motor neuron compromise, leading to the inability to maintain adduction of the ulnar digits. Wartenberg's sign (ulnar neuropathy) also features an abducted small finger, but the finger escape sign in this context of broader myelopathic symptoms (broad gait, clumsiness) points to cord compression.

Question 55

Fractures of the scaphoid proximal pole have a notoriously high rate of nonunion and avascular necrosis due to the bone's retrograde blood supply. The primary arterial supply responsible for perfusing the proximal pole of the scaphoid originates from which of the following vessels?





Explanation

The blood supply to the scaphoid is predominantly retrograde. The major blood supply enters the scaphoid via the dorsal ridge, which is perfused by the dorsal carpal branch of the radial artery. This dorsal supply accounts for roughly 70-80% of the bone's vascularity, specifically feeding the proximal pole in a retrograde fashion. The volar carpal branch supplies the distal 20-30% of the scaphoid (tubercle).

Question 56

A 25-year-old male presents with chronic dull anterior shin pain. Radiographs show a bubbly, multi-loculated lytic lesion in the anterior diaphysis of the tibia. Biopsy demonstrates islands of epithelial cells arrayed in a palisading pattern within a benign-appearing fibrous stroma. What is the most likely diagnosis and appropriate definitive treatment?





Explanation

The diagnosis is adamantinoma. It is a rare, low-grade malignant bone tumor that almost exclusively occurs in the anterior diaphysis of the tibia. The pathognomonic histology is biphasic, showing islands or nests of epithelial cells (which stain positive for cytokeratin) surrounded by a fibrous stroma. Because it is a low-grade malignancy that does not respond well to radiation or chemotherapy, the standard of care is wide surgical resection. Osteofibrous dysplasia occurs in the same location but typically in children <10 years and lacks the malignant epithelial nests.

Question 57

The posterior cruciate ligament (PCL) is the primary restraint to posterior tibial translation and consists of an anterolateral (AL) bundle and a posteromedial (PM) bundle. Which of the following best describes the physiological tensioning pattern of these bundles during knee range of motion?





Explanation

The PCL is composed of two functional bundles named for their tibial attachments: the larger anterolateral (AL) bundle and the smaller posteromedial (PM) bundle. Biomechanically, the AL bundle becomes increasingly tense during knee flexion and acts as the primary restraint to posterior translation at 90 degrees of flexion. The PM bundle is tight in extension and relatively lax in flexion. Double-bundle PCL reconstructions attempt to recreate this reciprocal tensioning relationship.

Question 58

A 30-year-old male returns to the clinic 6 weeks following open reduction and internal fixation of a displaced talar neck fracture (Hawkins Type II). An AP radiograph of the ankle demonstrates a distinct, linear subchondral radiolucent band beneath the dome of the talus. What is the prognostic significance of this radiographic finding (Hawkins sign)?





Explanation

The presence of a subchondral radiolucent band in the talar dome 6 to 8 weeks after a talar neck fracture is known as the Hawkins sign. This radiolucency represents subchondral atrophy/osteopenia secondary to disuse. Crucially, for bone resorption to occur, there must be active blood flow to deliver osteoclasts to the region. Therefore, a positive Hawkins sign is an excellent prognostic indicator that the talar body remains vascularized and the risk of avascular necrosis (AVN) is extremely low.

Question 59

A 28-year-old male is admitted with a severe tibia-fibula fracture. You are monitoring him for acute compartment syndrome using continuous intracompartmental pressure measurements. The patient's blood pressure is 115/80 mmHg, and his mean arterial pressure (MAP) is 92 mmHg. According to the concept of delta pressure (ΔP), what intracompartmental pressure reading would yield a ΔP of exactly 25 mmHg?





Explanation

Delta pressure (ΔP) is considered the most reliable indicator for diagnosing acute compartment syndrome and the need for fasciotomy. It is calculated by subtracting the intracompartmental pressure from the patient's diastolic blood pressure (ΔP = Diastolic BP - Compartment Pressure). A delta pressure of < 30 mmHg is the classic threshold for fasciotomy. If the diastolic BP is 80 mmHg, an intracompartmental pressure of 55 mmHg yields a delta pressure of 25 mmHg (80 - 55 = 25).

Question 60

In the setting of metal-on-polyethylene total joint arthroplasty, the generation of ultra-high-molecular-weight polyethylene (UHMWPE) wear debris is a primary driver of macrophage activation and subsequent periprosthetic osteolysis. Which specific mode of wear is primarily responsible for generating the millions of submicron-sized particles that lead to this cascade?





Explanation

Adhesive wear occurs when the bearing surfaces come into direct contact, creating microscopic transient chemical bonds or "micro-welds" between the polymer and the metal surface. As the surfaces continue to slide, these micro-welds are sheared off, pulling microscopic fragments of polyethylene away from the bulk material. This process continuously produces millions of tiny, submicron-sized wear particles. It is these submicron particles that are phagocytosed by macrophages, triggering the inflammatory cascade (release of TNF-alpha, IL-1, IL-6) that results in osteolysis. Abrasive wear creates larger scratches (ploughing), and fatigue wear leads to macroscopic delamination or pitting.

Question 61

A 35-year-old male presents with chronic knee pain. Radiographs reveal an epiphyseal lytic lesion in the proximal tibia with internal calcifications. Biopsy shows lobules of cells with abundant clear cytoplasm, distinct borders, and scattered giant cells. Which of the following is the most appropriate definitive management?





Explanation

The clinical and histologic picture describes clear cell chondrosarcoma, a low-grade malignant bone tumor that classically occurs in the epiphysis of long bones in adults (unlike chondroblastoma which is epiphyseal but occurs in skeletally immature patients). The treatment of choice is wide surgical resection, as it is relatively radio- and chemo-resistant and prone to local recurrence if managed with intralesional curettage.

Question 62

In total hip arthroplasty, the historical use of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic heads was associated with a specific mode of failure in vivo. Which of the following best describes this phenomenon?





Explanation

Y-TZP ceramics are prone to low-temperature degradation in the aqueous environment of the human body, a process known as phase transformation. The ceramic transforms from a tetragonal phase to a weaker monoclinic phase with a volumetric expansion, leading to microcracking, increased surface roughness, and subsequent massive polyethylene wear or ceramic fracture.

Question 63

A 42-year-old female falls from a height and sustains a comminuted, irreparable radial head fracture along with severe wrist pain. Examination reveals instability of the distal radioulnar joint (DRUJ) and marked proximal migration of the radius on stress fluoroscopy. Which of the following is the most appropriate surgical management?





Explanation

This is an Essex-Lopresti injury (radial head fracture, interosseous membrane tear, and DRUJ disruption). Excision of the radial head without replacement will lead to unopposed proximal radial migration, ulnocarpal impaction, and chronic wrist pain. Management requires restoration of the radiocapitellar joint (using a radial head arthroplasty if the fracture is irreparable) to restore longitudinal column stability, followed by reduction and stabilization (pinning) of the DRUJ.

Question 64

A 28-year-old unrestrained driver sustains an isolated coronal shear fracture of the lateral femoral condyle (Hoffa fracture). When managing this injury, what is the biomechanically optimal direction for lag screw fixation to resist the primary deforming forces?





Explanation

A Hoffa fracture is a coronal shear fracture of the femoral condyle. While anterior-to-posterior (AP) screws are clinically easier to place via an anterior exposure, biomechanical studies demonstrate that posterior-to-anterior (PA) lag screws are significantly stronger. This is because the screw threads engage the thicker, denser anterior diaphyseal/metaphyseal cortex, providing superior pullout strength and resisting the shear forces of the condyle.

Question 65

Which of the following patients diagnosed with a unilateral slipped capital femoral epiphysis (SCFE) is most strongly indicated for prophylactic in situ pinning of the contralateral asymptomatic hip?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended for patients with underlying endocrine disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency) and for patients presenting at a very young age (males <12 years, females <10 years). These patients have a significantly increased risk of developing bilateral disease.

Question 66

A 45-year-old man presents after a high-speed motor vehicle collision. CT shows a fracture through the pars interarticularis of C2 with 4 mm of anterior translation of C2 on C3 and severe angulation. According to the Levine-Edwards classification, this is a Type IIA Hangman's fracture. What is the mechanism of this specific injury type and the recommended treatment?





Explanation

A Levine-Edwards Type IIA Hangman's fracture features minimal translation but severe angulation. The mechanism is flexion-distraction. Crucially, cervical traction is strictly contraindicated as it will exacerbate the distraction, potentially causing severe neurological injury. Treatment typically involves cautious closed reduction under fluoroscopy using gentle compression and slight extension to close the disk space hinge, followed by halo vest immobilization.

Question 67

During medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability, identifying the exact femoral attachment site is critical to ensuring an isometric graft. Which radiographic landmarks accurately define Schöttle's point on a true lateral radiograph of the knee?





Explanation

Schöttle's point defines the anatomic and isometric femoral footprint of the MPFL on a true lateral radiograph. It is located 1 mm anterior to a line extending the posterior femoral cortex, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the level of the posterior point of Blumensaat's line.

Question 68

A 14-year-old male presents with recurrent ankle sprains and rigid, flat feet. Radiographs reveal a continuous 'C-sign' on the lateral radiograph of the ankle. Which of the following physical examination findings is most likely to be present?





Explanation

The 'C-sign' on a lateral ankle radiograph is highly indicative of a talocalcaneal (subtalar) coalition, formed by the continuous bony outline of the medial talar dome and the sustentaculum tali. Patients typically present with a rigid (peroneal spastic) flatfoot, characterized by a hindfoot valgus that does NOT correct (invert) during the single-leg heel rise test, and markedly restricted subtalar inversion and eversion.

Question 69

During the early reparative phase of tendon healing following an acute rupture, which type of collagen is predominantly synthesized by fibroblasts to provide early bridging of the defect?





Explanation

Following an acute tendon rupture, healing proceeds through inflammatory, reparative (proliferative), and remodeling phases. During the early reparative phase, fibroblasts primarily synthesize Type III collagen, which forms a disorganized, mechanically weak bridge across the defect. During the remodeling phase, this is gradually replaced by the stronger, longitudinally oriented Type I collagen, which makes up about 95% of the collagen in normal mature tendons.

Question 70

A 16-year-old male presents with a permeative lytic lesion in the diaphysis of the femur associated with a lamellated 'onion-skin' periosteal reaction. Biopsy demonstrates uniform sheets of small round blue cells. Cytogenetic analysis is most likely to reveal which of the following translocations?





Explanation

The clinical and histological findings describe Ewing sarcoma. The most common chromosomal abnormality in Ewing sarcoma is the balanced translocation t(11;22)(q24;q12), occurring in roughly 85% of cases. This results in the fusion of the EWS gene on chromosome 22 to the FLI1 gene on chromosome 11. t(X;18) is associated with synovial sarcoma; t(12;16) with myxoid liposarcoma; t(2;13) with alveolar rhabdomyosarcoma.

Question 71

According to Kanavel's cardinal signs for pyogenic flexor tenosynovitis of the hand, which of the following is generally considered the earliest and most reliable clinical indicator?





Explanation

Kanavel's four cardinal signs of pyogenic flexor tenosynovitis are: 1) flexed resting posture of the digit, 2) uniform (fusiform) swelling, 3) tenderness along the flexor tendon sheath, and 4) exquisite pain with passive extension. Of these, severe pain with passive extension stretches the inflamed synovium and is considered the earliest, most sensitive, and most reliable sign of the condition.

Question 72

Patellar clunk syndrome is a recognized complication following total knee arthroplasty (TKA). Which of the following prosthesis designs and surgical factors is most strongly associated with the development of this complication?





Explanation

Patellar clunk syndrome is a complication primarily seen in posterior-stabilized (PS) TKA designs. It results from the formation of a fibrous nodule at the superior pole of the patella that catches within the intercondylar notch (femoral box) during active knee extension from a flexed position. Older PS designs with a sharp, prominent anterior intercondylar box, as well as joint line elevation leading to relative patella alta, significantly increase the risk.

Question 73

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up, the parents report she has stopped kicking her leg on the treated side. On examination, the hip is hyperflexed beyond 120 degrees in the harness, and active knee extension is absent. Which nerve is most likely affected?





Explanation

Femoral nerve palsy is the most common nerve injury associated with Pavlik harness treatment for DDH. It is typically iatrogenic, caused by hyperflexion of the hip (usually >120 degrees), which dynamically compresses the femoral nerve against the inguinal ligament or the brim of the pelvis. Clinically, it presents with a loss of active knee extension (decreased kicking). Treatment involves immediate temporary removal or adjustment of the harness flexion straps.

Question 74

A 25-year-old male falls from a height of 30 feet, landing on both feet. He sustains a U-shaped sacral fracture, with a transverse fracture line through S2 connecting bilateral transforaminal longitudinal fractures. Neurological exam reveals absent perianal sensation. This highly unstable injury pattern implies which of the following biomechanical phenomena?





Explanation

A U-shaped sacral fracture consists of bilateral longitudinal sacral fractures joined by a transverse fracture line (commonly at S1 or S2). This injury pathomechanism uncouples the upper sacrum (and therefore the entire axial spine) from the lower sacrum and pelvis, resulting in 'spinopelvic dissociation'. It is highly unstable, is associated with a high incidence of sacral nerve root injury (bowel/bladder dysfunction), and typically requires surgical stabilization with lumbopelvic fixation.

Question 75

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction by promoting the differentiation of mesenchymal stem cells into osteoblasts. Which of the following BMPs is commercially available as recombinant human BMP-2 (rhBMP-2) and is FDA-approved for specific applications such as anterior lumbar interbody fusion (ALIF)?





Explanation

Recombinant human BMP-2 (rhBMP-2), also known commercially as INFUSE, is highly osteoinductive and FDA-approved for use in single-level anterior lumbar interbody fusion (ALIF) with a specific LT-CAGE, as well as for certain open tibial shaft fractures and maxillofacial reconstructions. While BMP-7 (OP-1) also has osteoinductive properties and was previously used under a Humanitarian Device Exemption, the product associated with widespread ALIF use is BMP-2.

Question 76

A patient sustains a cervical spine injury. On examination, there is zero motor function below the level of injury. Pinprick and light touch sensation are absent throughout the lower extremities, but the patient retains deep anal pressure and perianal sensation. According to the American Spinal Injury Association (ASIA) Impairment Scale, how is this injury graded?





Explanation

The ASIA Impairment Scale evaluates spinal cord injuries: ASIA A = Complete (no sensory/motor function preserved in sacral segments S4-S5). ASIA B = Sensory Incomplete (sensory, but no motor function, preserved below the neurological level and includes sacral segments). ASIA C = Motor Incomplete (motor function preserved, more than half of key muscles below the level have a grade <3). ASIA D = Motor Incomplete (motor function preserved, at least half of key muscles have grade >=3). Because this patient retains perianal sensation (sacral sparing) but has no motor function, it is graded ASIA B.

Question 77

A Jones fracture (Zone 2 fracture of the fifth metatarsal) occurs at the metaphyseal-diaphyseal junction and is prone to delayed union or nonunion due to a vascular watershed area. Which of the following arteries provides the primary retrograde intramedullary blood supply to this region, which is disrupted by the fracture?





Explanation

The intramedullary blood supply of the fifth metatarsal is primarily derived from a nutrient artery that enters the medial cortex at the junction of the proximal and middle thirds of the diaphysis. It then courses proximally in a retrograde fashion. A fracture at the metaphyseal-diaphyseal junction (Zone 2) disrupts this retrograde intramedullary flow, creating a vascular watershed area that significantly increases the risk of nonunion.

Question 78

In the setting of an irreversible high radial nerve palsy, tendon transfers are utilized to restore wrist and digit extension. In the classic Boyes transfer to restore finger extension, which muscle is transferred to the extensor digitorum communis (EDC)?





Explanation

To restore finger extension in radial nerve palsy, the standard (Jones) transfer historically used the Flexor Carpi Ulnaris (FCU) or Flexor Carpi Radialis (FCR). However, the Boyes transfer specifically utilizes the Flexor Digitorum Superficialis (FDS) of the middle finger, routed through the interosseous membrane to the Extensor Digitorum Communis (EDC). This spares wrist flexors and provides excellent excursion for digit extension.

Question 79

During a transtibial posterior cruciate ligament (PCL) reconstruction, the graft is subjected to severe mechanical stress as it exits the posterior tibial tunnel, a phenomenon termed the 'killer turn.' Which surgical technique was specifically developed to completely avoid this acute angulation?





Explanation

In a standard transtibial PCL reconstruction, the graft must navigate a sharp, nearly 90-degree turn ('killer turn') as it exits the posterior tibial tunnel to reach its femoral origin. This acute angle causes graft abrasion and attenuation, leading to premature laxity or failure. The tibial inlay technique avoids this entirely by using a posterior approach to secure a bone block directly into a trough at the anatomic posterior tibial footprint, eliminating the tibial tunnel.

Question 80

In the setting of a severe vertical shear (VS) pelvic ring disruption with profound hemodynamic instability, life-threatening arterial hemorrhage from the posterior pelvic elements is most commonly due to injury of which of the following vessels?





Explanation

Vertical shear (VS) pelvic ring injuries involve massive disruption of the posterior sacroiliac complex. Due to its intimate anatomic relationship with the upper border of the greater sciatic notch and the sacroiliac joint, the superior gluteal artery (the largest branch of the posterior division of the internal iliac artery) is highly vulnerable to laceration or avulsion in posterior disruption patterns. Anterior ring disruptions (like APC injuries) are more commonly associated with bleeding from the obturator or internal pudendal vessels.

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