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Orthopedic Surgery Mock Exam - Set B29D06

Orthopedic Surgery Mock Exam - Set FF5036

27 Apr 2026 62 min read 70 Views
Orthopedic Surgery Mock Exam - Set FF5036

Key Takeaway

This mock exam provides 50 randomized questions derived from Arab Board and FRCS databanks to perfectly simulate testing environments.

Orthopedic Surgery Mock Exam - Set FF5036

Comprehensive 100-Question Exam


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Question 1

A 25-year-old male presents with a slow-growing, painful mass around the posterolateral knee. MRI reveals a well-circumscribed, soft tissue mass near the joint without bone involvement. Core needle biopsy demonstrates a biphasic histologic pattern with both epithelial and spindle cells. Which of the following specific chromosomal translocations is most characteristic of this patient's diagnosis?





Explanation

The clinical scenario and biphasic histology (epithelial and spindle cells) are classic for Synovial Sarcoma. The hallmark cytogenetic abnormality for synovial sarcoma is the t(X;18)(p11;q11) translocation, which results in the fusion of the SYT gene on chromosome 18 with one of the SSX genes (SSX1, SSX2, or SSX4) on the X chromosome.

Option 0 is characteristic of Ewing sarcoma. Option 2 is associated with myxoid liposarcoma. Option 3 is seen in extraskeletal myxoid chondrosarcoma. Option 4 is characteristic of alveolar rhabdomyosarcoma.

Question 2

A 45-year-old male is undergoing an ilioinguinal approach for the treatment of an anterior column/posterior hemitransverse acetabular fracture.

During the dissection of the retropubic space (Space of Retzius), brisk arterial bleeding is encountered approximately 5 cm from the symphysis pubis, located posterior to the superior pubic ramus. Injury to which of the following structures is the most likely source of this hemorrhage?





Explanation

The source of bleeding in this location is the 'corona mortis,' which is an anastomotic connection between the external iliac (or inferior epigastric) system and the obturator system. It traverses the superior pubic ramus at an average distance of 5 to 6 cm from the pubic symphysis. Surgeons must carefully dissect the posterior aspect of the superior pubic ramus and ligate these vessels during the ilioinguinal or intrapelvic approaches to avoid catastrophic hemorrhage.

Question 3

A 4-month-old infant with developmental dysplasia of the hip (DDH) has been treated with a Pavlik harness for the last three weeks. At the most recent clinical follow-up, the mother reports that the infant is no longer kicking the affected leg. On examination, the infant exhibits an inability to actively extend the knee, and there is a diminished patellar reflex on the affected side. What is the most likely cause of this complication?





Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, usually caused by excessive hip flexion, which compresses the femoral nerve against the inguinal ligament. It presents as decreased active knee extension and a diminished patellar reflex. When this occurs, the harness must be adjusted to decrease flexion or temporarily discontinued until nerve function recovers.

Question 4

A 22-year-old collegiate baseball pitcher presents with insidious onset of posterior shoulder pain that is most pronounced during the late cocking phase of throwing. Physical examination reveals a glenohumeral internal rotation deficit (GIRD) of 25 degrees compared to the contralateral shoulder, but symmetric total arc of motion. Which of the following is the primary pathoanatomic alteration driving this clinical presentation?





Explanation

Glenohumeral internal rotation deficit (GIRD) in overhead throwing athletes is primarily caused by contracture and thickening of the posteroinferior capsule. This contracture shifts the glenohumeral contact point posterosuperiorly during the late cocking phase (abduction and external rotation), leading to 'internal impingement' of the undersurface of the rotator cuff against the posterosuperior glenoid labrum. Treatment initially focuses on posterior capsular stretching (e.g., sleeper stretches).

Question 5

A 30-year-old male is evaluated in the trauma bay following a high-speed motor vehicle collision. Cervical spine imaging demonstrates a traumatic spondylolisthesis of the axis (Hangman's fracture). The C2-C3 disc space is widened posteriorly with severe angulation, but there is minimal anterior translation of C2 on C3. This injury pattern is classified as a Levine and Edwards Type IIA fracture. Which of the following interventions is strictly contraindicated in the acute management of this fracture?





Explanation

A Levine and Edwards Type IIA Hangman's fracture is a flexion-distraction injury characterized by severe angulation with minimal translation and an intact anterior longitudinal ligament. Applying cervical traction is strictly contraindicated in Type IIA fractures because it worsens the deformity by further distracting the posterior disc space and potentially distracting the fracture site catastrophically. Treatment usually involves closed reduction (gentle extension and compression) and application of a halo vest.

Question 6

When evaluating the biomaterials used in total hip arthroplasty, the sterilization process of ultra-high molecular weight polyethylene (UHMWPE) profoundly affects its long-term wear characteristics. Which of the following sterilization environments for UHMWPE is most strongly associated with free radical formation leading to oxidative chain scission, structural degradation, and accelerated clinical wear?





Explanation

Gamma irradiation of UHMWPE in air (oxygen-containing environment) leads to the formation of free radicals that react with oxygen to form hydroperoxides. Over time, this oxidation leads to chain scission, decreased molecular weight, embrittlement, and catastrophic delamination and wear of the polyethylene bearing surface. Modern sterilization techniques use inert gases (like argon), vacuum packaging, or non-irradiation methods (like ethylene oxide) followed by highly cross-linking and annealing or remelting to eliminate free radicals.

Question 7

A 24-year-old football player sustains a hyperplantarflexion injury to his midfoot. Weight-bearing radiographs show a 3 mm diastasis between the base of the first and second metatarsals. An MRI confirms an isolated, complete rupture of the Lisfranc ligament. Which of the following correctly describes the anatomical attachments of this critically stabilizing ligament?





Explanation

The Lisfranc ligament is an intra-articular ligament that originates from the lateral aspect of the medial cuneiform and attaches to the medial base of the second metatarsal. It is the strongest of the ligaments stabilizing the second metatarsal base and is critical for maintaining the structural integrity of the midfoot arch. There is no direct ligamentous connection between the base of the first and second metatarsals.

Question 8

A 35-year-old rock climber presents with a 'popping' sensation in his long finger after attempting a forceful crimp grip. He demonstrates pain over the volar proximal phalanx and clinically evident bowstringing of the flexor tendons on resisted flexion. Which two annular pulleys of the flexor tendon sheath are considered biomechanically essential to prevent bowstringing and must be preserved or reconstructed?





Explanation

The flexor tendon sheath contains a series of annular (A) and cruciate (C) pulleys. The A2 pulley (located over the proximal phalanx) and the A4 pulley (located over the middle phalanx) are biomechanically the most critical for maintaining the flexor tendons closely apposed to the bone, thereby preventing bowstringing and maintaining the mechanical advantage (moment arm) of the flexor digitorum superficialis and profundus.

Disruption of both results in clinically significant mechanical deficits.

Question 9

Which of the following osteoinductive agents, members of the transforming growth factor-beta (TGF-beta) superfamily, is specifically FDA approved as an alternative to autogenous bone graft in acute, open tibial shaft fractures treated with an intramedullary nail?





Explanation

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is FDA approved for use in acute open tibial shaft fractures that have been stabilized with an intramedullary nail. Its use has been shown to reduce the need for secondary bone grafting procedures. rhBMP-7 (also known as Osteogenic Protein-1, or OP-1) was previously available under a Humanitarian Device Exemption for recalcitrant long bone nonunions, but BMP-2 is the specific agent approved for acute open tibias.

Question 10

A 72-year-old female falls and sustains a displaced, intracapsular femoral neck fracture. Due to the high risk of avascular necrosis and nonunion associated with this injury pattern, a hemiarthroplasty is planned. The profound vascular vulnerability of the adult femoral head is due to its heavy reliance on the ascending cervical branches. Which artery is the primary source of these critical ascending branches?





Explanation

In the adult, the principal blood supply to the femoral head is derived from the medial femoral circumflex artery (MFCA). The MFCA gives rise to the lateral epiphyseal artery system (ascending cervical branches) that penetrate the joint capsule at the base of the femoral neck and course along the retinaculum to perfuse the femoral head. Displaced intracapsular fractures disrupt these vessels, leading to a high rate of osteonecrosis. The artery of the ligamentum teres provides a negligible supply in adults.

Question 11

A 16-year-old male is diagnosed with a high-grade intramedullary osteosarcoma of the distal femur. Staging studies show no clinically detectable pulmonary or osseous metastases. He is initiated on a standard neoadjuvant chemotherapy protocol, followed by limb-salvage wide resection. Which of the following factors obtained from the resected specimen is the most significant prognostic indicator for his long-term survival?





Explanation

In non-metastatic high-grade osteosarcoma, the degree of tumor necrosis following neoadjuvant chemotherapy is the single most powerful prognostic factor for long-term survival. A good response is typically defined as 90% or greater tumor necrosis (Huvos grade III or IV). Patients with less than 90% necrosis (poor responders) have a significantly higher risk of local recurrence and systemic metastasis, resulting in lower overall survival.

Question 12

A 12-year-old male with a BMI in the 99th percentile undergoes urgent in-situ percutaneous pinning with a single cannulated screw for a stable Slipped Capital Femoral Epiphysis (SCFE).

Four months post-operatively, he returns to the clinic complaining of severe, worsening global hip stiffness and pain. Radiographs demonstrate marked, uniform joint space narrowing of the affected hip without segmental collapse of the femoral head. What is the most likely etiology of this complication?





Explanation

The clinical presentation of severe hip stiffness and uniform joint space narrowing on radiographs following SCFE pinning is classic for chondrolysis. A major known risk factor for chondrolysis in this setting is unrecognized penetration of the hardware (screw) into the joint space. Avascular necrosis typically presents with segmental subchondral sclerosis and collapse (crescent sign), rather than uniform joint space loss as the primary early radiographic finding.

Question 13

A 68-year-old male presents with bilateral lower extremity pain, heaviness, and cramping that occurs reliably after walking two blocks. The patient's history is evaluated to differentiate between neurogenic claudication (due to lumbar spinal stenosis) and vascular claudication (due to peripheral arterial disease). Which of the following findings most specifically suggests neurogenic claudication?





Explanation

Neurogenic claudication is characteristically position-dependent. Extension of the lumbar spine decreases the cross-sectional area of the spinal canal and neural foramina, exacerbating compression. Walking downhill forces the spine into extension, making symptoms worse in neurogenic claudication. Walking uphill, leaning on a shopping cart, or sitting flexes the spine, enlarging the canal and relieving symptoms. Vascular claudication is demand-dependent (exacerbated by walking uphill due to increased muscular oxygen demand) and quickly relieved by simply standing still.

Question 14

An orthopedic surgeon is evaluating the native anterior cruciate ligament (ACL) during a knee arthroscopy. The ACL is anatomically divided into two main functional bundles: the anteromedial (AM) bundle and the posterolateral (PL) bundle. Which of the following statements most accurately describes the distinct biomechanical roles of these bundles?





Explanation

The native ACL consists of two primary bundles named for their tibial insertion. The anteromedial (AM) bundle is tight in flexion and is the primary restraint to anterior tibial translation at 90 degrees of knee flexion. The posterolateral (PL) bundle is tight in extension and is the primary restraint to anterior tibial translation and rotational loads (pivot shift) near full extension. Neither bundle is completely isometric.

Question 15

A 65-year-old female is 1-year post-operative from a primary total knee arthroplasty (TKA). She complains of anterior knee pain and a feeling that her kneecap is 'popping out.' Examination and CT imaging demonstrate significant internal rotation of the femoral component relative to the epicondylar axis, as well as internal rotation of the tibial component relative to the tibial tubercle. This combined malrotation is most predictably associated with which of the following patellofemoral complications?





Explanation

Internal rotation of the femoral and tibial components in TKA functionally increases the Q-angle. Internal rotation of the femoral component moves the trochlear groove medially, while internal rotation of the tibial component moves the tibial tubercle laterally relative to the trochlea. This lateralizes the extensor mechanism vector, reliably pulling the patella laterally and resulting in lateral patellar tracking, subluxation, or dislocation.

Question 16

A 55-year-old male with long-standing, poorly controlled type 2 diabetes presents with a warm, erythematous, and swollen right foot and ankle. He denies any systemic symptoms like fevers or chills. Radiographs reveal fragmentation of the tarsal bones, periarticular debris, and subluxation of the tarsometatarsal joints. According to the Eichenholtz classification of Charcot arthropathy, which stage does this patient's clinical and radiographic picture represent?





Explanation

The Eichenholtz classification characterizes the radiographic progression of Charcot arthropathy. Stage I (Development/Fragmentation) is characterized by acute inflammation, osseous fragmentation, periarticular debris, and joint subluxation/dislocation. Stage II (Coalescence) shows decreased inflammation with absorption of fine debris and early fusion. Stage III (Reconstruction) shows rounded bone ends, sclerosis, and stable arthrosis. Stage 0 (added later by Shibata) describes the clinical acute inflammatory phase before distinct radiographic changes occur.

Question 17

A 40-year-old carpenter presents with weakness in his right hand. On examination, when asked to make an 'OK' sign with his thumb and index finger, the distal interphalangeal joint of the index finger and the interphalangeal joint of the thumb remain in extension, resulting in a 'flat' pinch. He has absolutely no sensory deficits in the forearm or hand. This clinical presentation represents a deficit in which of the following muscle-nerve pairings?





Explanation

The patient has an abnormal 'OK' sign, indicating weakness or paralysis of the flexor pollicis longus (FPL) and the flexor digitorum profundus (FDP) to the index finger. These muscles, along with the pronator quadratus, are innervated by the Anterior Interosseous Nerve (AIN), a pure motor branch of the median nerve. AIN syndrome results in weakness of these muscles without any sensory loss.

Question 18

When evaluating the ultrastructure of normal adult articular cartilage, the tissue is anatomically divided into distinct layers or zones from the surface to the subchondral bone. Which zone is biomechanically characterized by having the highest concentration of proteoglycans, the lowest water content, and chondrocytes arranged in vertical columns?





Explanation

The deep (radial) zone of articular cartilage is responsible for providing the greatest resistance to compressive loads. It contains the highest concentration of proteoglycans, the lowest water content, and type II collagen fibers arranged perpendicularly (vertically) to the joint surface. The chondrocytes in this zone are also characteristically arranged in vertical columns. The superficial zone has the highest water content and collagen fibers parallel to the surface to resist shear stress.

Question 19

A 28-year-old male is brought to the trauma center unconscious following a motorcycle crash. He has a closed, highly comminuted midshaft tibia fracture. The extremity is swollen and tense. Due to his altered mental status, continuous intracompartmental pressure monitoring is initiated. An emergent four-compartment fasciotomy is universally indicated when the difference between the patient's diastolic blood pressure and the absolute compartmental pressure (Delta P) falls below what critical threshold?





Explanation

The diagnosis of acute compartment syndrome in an obtunded patient relies on objective pressure measurements. The 'Delta P' concept states that a fasciotomy is indicated when the tissue pressure rises to within 30 mm Hg of the diastolic blood pressure (Delta P < 30 mm Hg). Absolute compartment pressure values alone are less reliable than the Delta P because muscle perfusion depends on the arteriolar pressure gradient, which is directly related to the systemic diastolic pressure.

Question 20

A 14-year-old boy presents with progressive thigh pain. Radiographs demonstrate a large, permeative, lytic lesion in the diaphysis of the femur with an extensive 'onion-skin' periosteal reaction.

A core needle biopsy is performed, and histology reveals densely packed uniform small round blue cells with scant cytoplasm. Immunohistochemistry is strongly positive for CD99. Which of the following chromosomal translocations is most frequently associated with the pathogenesis of this tumor?





Explanation

The clinical presentation, 'onion-skin' periosteal reaction, small round blue cell histology, and CD99 positivity are hallmark features of Ewing Sarcoma. Ewing sarcoma is a primitive neuroectodermal tumor defined by translocations involving the EWSR1 gene on chromosome 22. The most common translocation, found in approximately 85% of cases, is t(11;22)(q24;q12), which fuses EWSR1 with the FLI1 gene. Option 1 is synovial sarcoma, Option 2 is myxoid liposarcoma, Option 3 is extraskeletal myxoid chondrosarcoma, and Option 4 is alveolar rhabdomyosarcoma.

Question 21

A 65-year-old male presents with worsening hand clumsiness, frequent dropping of objects, and a broad-based, unsteady gait. On examination, he has a positive Hoffmann sign and hyperreflexia in his lower extremities. An MRI of the cervical spine reveals severe canal stenosis at C4-C5 and C5-C6. Which of the following MRI findings is considered the most specific indicator of a poor prognosis for neurologic recovery following surgical decompression?





Explanation

T1-weighted hypointensity (representing myelomalacia, necrosis, or cyst formation) is the most specific MRI finding for a poor prognosis in cervical spondylotic myelopathy. While T2-weighted hyperintensity indicates cord edema or inflammation and can be reversible, T1 hypointensity represents permanent structural damage to the spinal cord.

Question 22

A 45-year-old manual laborer presents with chronic right wrist pain. He reports a fall on an outstretched hand 10 years ago that was never treated.

Radiographs reveal a scaphoid nonunion with advanced arthritic changes at the radioscaphoid joint, but the radiolunate joint is completely spared. Which of the following is the most appropriate surgical treatment?





Explanation

The patient has Scaphoid Nonunion Advanced Collapse (SNAC) wrist. Stage II SNAC involves arthritis at the radioscaphoid joint, and Stage III involves the midcarpal joint, but both spare the radiolunate joint. Scaphoid excision and four-corner fusion (capitate, lunate, hamate, triquetrum) is the classic treatment. Proximal row carpectomy (PRC) is contraindicated if there is significant arthritis at the proximal capitate.

Question 23

A 25-year-old male sustained a foot injury in a motor vehicle accident.

Radiographs demonstrate a 'fleck sign' in the first intermetatarsal space and widening between the bases of the first and second metatarsals. What are the anatomic attachments of the ligament most likely ruptured in this injury?





Explanation

The Lisfranc ligament is a strong interosseous ligament that connects the medial cuneiform to the base of the second metatarsal. It is the critical stabilizer of the second tarsometatarsal joint complex. Rupture typically results in lateral subluxation of the second through fifth metatarsals.

Question 24

A 30-year-old female presents with knee pain. Radiographs show an eccentric, lytic lesion in the distal femur extending to the subchondral bone. Biopsy reveals multinucleated giant cells in a stroma of mononuclear cells. Due to the tumor's size and location, she is started on Denosumab prior to surgical intervention. What is the mechanism of action of this medication?





Explanation

Denosumab is a fully human monoclonal antibody that binds directly to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By binding to RANKL, it prevents RANKL from interacting with the RANK receptor on osteoclasts and their precursors, thereby inhibiting osteoclast formation, function, and survival. It is highly effective in treating Giant Cell Tumors of bone.

Question 25

A 40-year-old male sustains a high-energy motor vehicle collision resulting in a severe bicondylar tibial plateau fracture (Schatzker VI).

On examination, the soft tissues are grossly swollen and tense, but there is no compartment syndrome. The initial management is application of a knee-spanning external fixator. What is the most reliable clinical indicator that the soft tissues are ready for definitive open reduction and internal fixation?





Explanation

In high-energy tibial plateau fractures, definitive internal fixation is delayed until the soft tissue envelope recovers to minimize wound complications. The most reliable clinical sign that swelling has adequately subsided and surgery can safely proceed is the appearance of skin wrinkles (the 'wrinkle sign'), which typically occurs 10 to 14 days post-injury.

Question 26

A 12-year-old obese male presents with 3 weeks of right thigh pain and a limp. He is diagnosed with a stable Slipped Capital Femoral Epiphysis (SCFE) and undergoes in situ single screw fixation. To avoid the most devastating vascular complication of this condition and its treatment, the surgeon must be mindful of the primary blood supply to the capital femoral epiphysis. Which vessel is this?





Explanation

The lateral epiphyseal artery, which is the terminal branch of the medial femoral circumflex artery (MFCA), provides the primary blood supply to the capital femoral epiphysis. During SCFE pinning, an exclusively anterior-superior pin placement risks penetrating the joint and damaging the blood supply. Proper placement is strictly center-center to avoid the superolateral extraosseous blood supply.

Question 27

A 65-year-old active female who underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago presents with an audible "squeaking" sound from her hip during walking. She denies any pain, and her radiographs demonstrate well-fixed components with no evidence of loosening. What is the most likely biomechanical cause of this phenomenon?





Explanation

Squeaking is a known complication of ceramic-on-ceramic bearings. It is most strongly associated with edge loading of the bearing surfaces, which typically occurs due to component malposition, specifically an excessively steep (abducted) or excessively anteverted acetabular cup. It can also be related to stripe wear and micro-separation.

Question 28

During an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, the surgeon inadvertently drills the femoral tunnel anterior to the isometric point. What is the most likely postoperative kinematic consequence of this technical error?





Explanation

Proper placement of the femoral tunnel is critical for isometric graft function. If the femoral tunnel is placed too far anteriorly, the distance between the tibial and femoral tunnels increases during knee flexion. Consequently, the graft becomes excessively tight in flexion, leading to a loss of full knee flexion, while remaining relatively loose in extension.

Question 29

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction and fracture healing. Which of the following describes the correct intracellular signaling pathway utilized by BMP-2?





Explanation

BMP-2, BMP-4, and BMP-7 belong to the TGF-beta superfamily. They bind to cell-surface serine/threonine kinase receptors. Upon activation, these receptors phosphorylate intracellular Smad proteins, specifically Smads 1, 5, and 8. These phosphorylated Smads then form a complex with Smad 4 and translocate to the nucleus to regulate the transcription of osteogenic genes.

Question 30

A 25-year-old male sustains a Zone II flexor tendon laceration of the index finger. Repair is performed with a 4-strand core suture and a running epitendinous repair. What is the primary biomechanical advantage of adding the epitendinous suture?





Explanation

In flexor tendon repairs, the addition of an epitendinous suture is crucial. It smooths the repair site by tucking in frayed tendon ends, which significantly decreases gliding resistance (work of flexion). Furthermore, it contributes mechanically by increasing the overall tensile strength of the repair by 10% to 50% and decreases gap formation under load.

Question 31

A 35-year-old male is involved in a severe crush injury at a construction site.

Imaging reveals a widely displaced Anteroposterior Compression (APC) pelvic ring injury. According to the Young-Burgess classification, what specific ligamentous disruption differentiates an APC-III injury from an APC-II injury?





Explanation

In the Young-Burgess classification, an APC-II injury is characterized by symphyseal diastasis and disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but the posterior sacroiliac ligaments remain intact (rotationally unstable, vertically stable). An APC-III injury involves complete disruption of both the anterior AND posterior sacroiliac ligaments, rendering the hemipelvis both rotationally and vertically unstable.

Question 32

A 22-year-old male dives into shallow water and strikes his head. Imaging reveals a C5 burst fracture with significant canal compromise. On neurologic examination, he has absent motor function in the bilateral upper extremities distal to C5 and absent motor function in the lower extremities. He has no sensation to pinprick or light touch below C5, but he has intact perianal sensation and voluntary anal sphincter contraction. What is his American Spinal Injury Association (ASIA) Impairment Scale grade?





Explanation

The ASIA Impairment Scale evaluates the severity of spinal cord injuries. The presence of perianal sensation (sacral sparing) or voluntary anal contraction means the injury is incomplete. Because he has sensory preservation below the neurologic level (including S4-S5) but no motor function extending more than three levels below the motor level, he is classified as ASIA B (Sensory Incomplete, Motor Complete).

Question 33

A 3-month-old female is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip (DDH). At the 3-week follow-up, the parents report that she is no longer kicking her right leg. On physical examination, she has absent active knee extension on the right, and the patellar reflex is absent. What is the most appropriate next step in management?





Explanation

The patient has developed a femoral nerve palsy, a known complication of Pavlik harness treatment caused by excessive hyperflexion of the hip which compresses the femoral nerve. The standard of care is to completely remove the harness to allow the nerve to recover. Once spontaneous recovery of the nerve occurs (usually within weeks), alternative treatment (like a rigid abduction orthosis or cast) can be instituted.

Question 34

A 55-year-old male with a 15-year history of poorly controlled type 2 diabetes presents with a swollen, erythematous, warm, and painless right foot.

Radiographs show early fragmentation and debris at the tarsometatarsal joints. Inflammatory markers are mildly elevated, but there are no open wounds or ulcers. What is the most appropriate initial management?





Explanation

This is a classic presentation of acute Charcot neuroarthropathy (Eichenholtz Stage I: fragmentation/dissolution). The joint is hot, swollen, and red, often mimicking infection. In the absence of an ulcer, deep infection is highly unlikely. The gold standard initial treatment to halt progression and prevent severe deformity is strict offloading and immobilization, most effectively achieved with a Total Contact Cast (TCC).

Question 35

In posterior-stabilized (PS) total knee arthroplasty (TKA), the cam and post mechanism substitutes for the posterior cruciate ligament. The risk of posterior dislocation of the tibia on the femur is related to the 'jump distance'. Which of the following intraoperative modifications most effectively increases the jump distance?





Explanation

Jump distance is the vertical distance the femoral cam must travel to clear the top of the tibial post. Decreasing the posterior slope of the tibial cut effectively increases the relative vertical height of the post relative to the femur, thereby increasing the jump distance and reducing the risk of cam-post dislocation. Conversely, increasing the posterior slope tilts the post backward, reducing its relative height and decreasing the jump distance.

Question 36

A 15-year-old male presents with deep, aching pain in his distal femur. Radiographs reveal an aggressive lytic lesion with a 'sunburst' periosteal reaction. Biopsy confirms a high-grade intramedullary osteosarcoma. He undergoes neoadjuvant chemotherapy followed by wide surgical resection. Which of the following is the most significant prognostic factor for long-term survival in this patient?





Explanation

For conventional high-grade osteosarcoma, the degree of tumor necrosis following neoadjuvant chemotherapy (histologic response) is the single most reliable prognostic indicator for long-term survival. A good response is typically defined as greater than 90% tumor necrosis. Patients with >90% necrosis have significantly better survival rates than poor responders.

Question 37

A 22-year-old elite rugby player undergoes an open Latarjet procedure for recurrent anterior shoulder instability associated with 25% glenoid bone loss.

The primary biomechanical stabilizing effect of this procedure when the arm is placed in the vulnerable position of abduction and external rotation is attributed to:





Explanation

The Latarjet procedure provides stability through a 'triple effect'. While the bony block restores glenoid width, the most significant dynamic stabilizing mechanism in abduction and external rotation (the typical apprehension position) is the 'sling' effect. The transferred conjoined tendon runs across the inferior aspect of the subscapularis and anterior capsule, dynamically tensioning them and preventing anterior translation of the humeral head.

Question 38

A 28-year-old male sustains a high-energy Pauwels type III (vertical) femoral neck fracture. Which of the following internal fixation constructs provides the greatest biomechanical stability and resistance against the specific deforming forces characteristic of this fracture pattern?





Explanation

Pauwels III fractures are vertically oriented (>50 degrees to the horizontal) and experience massive vertical shear forces, leading to a high rate of varus collapse, nonunion, and failure when fixed with multiple cancellous screws alone. Biomechanical studies have shown that a fixed-angle construct, such as a sliding hip screw (which acts as a strong buttress against vertical shear) combined with an anti-rotation screw, provides superior stability for vertical femoral neck fractures in young adults.

Question 39

During surgical fasciectomy for severe Dupuytren's contracture, the surgeon must carefully identify and protect the neurovascular bundles. The pretendinous band of the palmar fascia becomes the pretendinous cord, causing MCP joint contracture. Which specific pathological cord is primarily responsible for contracture of the proximal interphalangeal (PIP) joint and central/superficial displacement of the neurovascular bundle?





Explanation

The spiral cord is formed from the coalescence of four structures: the pretendinous band, spiral band, lateral digital sheet, and Grayson's ligament. As it contracts, it causes PIP joint flexion and crucially spirals around the neurovascular bundle, pulling it centrally, volarly (superficially), and proximally. This altered anatomy puts the digital nerve at extremely high risk of iatrogenic transection during surgery.

Question 40

Articular cartilage provides a low-friction, load-bearing surface for synovial joints. Its biomechanical properties are derived from its specialized extracellular matrix. Which zone of normal articular cartilage contains the largest diameter collagen fibrils oriented strictly perpendicular to the joint surface to resist shear forces, and simultaneously possesses the highest concentration of proteoglycans?





Explanation

The deep (radial) zone of articular cartilage represents about 30% of the cartilage volume. It contains the largest diameter type II collagen fibrils, which are oriented perpendicular to the subchondral bone to anchor the cartilage and resist shear forces. It also contains the highest concentration of proteoglycans (and therefore the lowest concentration of water), providing the highest compressive stiffness.

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