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Arab Orthopaedic Board MCQs - Part 6

27 Apr 2026 92 min read 81 Views
Arab Ortho Board MCQs - Part 5

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Looking for accurate information on Arab Orthopaedic Board MCQs - Part 6? Practice Arab Orthopaedic Board MCQs Part 6. Review orthopedic surgery questions 251 to 300 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 6

Comprehensive 100-Question Exam


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Question 1

A 45-year-old male sustains an LC-II pelvic ring injury (crescent fracture) after a motor vehicle accident. Which of the following best describes the pathomechanics and optimal fixation of this specific injury?





Explanation

An LC-II (crescent fracture) is caused by a lateral compression (internal rotation) force. It results in a fracture of the posterior ilium. The strong posterior sacroiliac (SI) ligaments remain attached to the crescent-shaped posterior iliac fragment, leaving the SI joint intact. Treatment typically involves Open Reduction and Internal Fixation (ORIF) of the ilium rather than an SI screw, because the SI joint itself is not dislocated.

Question 2

An 8-month-old female presents with a persistently dislocated left hip after an unsuccessful 6-week trial of a Pavlik harness initiated at age 5 months. Ultrasound confirms continued posteroclavicular dislocation. What is the most appropriate next step in management?





Explanation

In children older than 6 months with Developmental Dysplasia of the Hip (DDH), or those who fail a Pavlik harness, closed reduction and spica casting under general anesthesia with an arthrogram is the next standard step. A rigid abduction brace is sometimes used for Pavlik failure in infants <6 months, but at 8 months, closed reduction is indicated. Open reduction is reserved for failure of closed reduction.

Question 3

During a primary total knee arthroplasty in a patient with a severe, fixed valgus deformity, the knee remains tight laterally in both flexion and extension after standard bone cuts. Which of the following lateral structures should be sequentially released first to optimally balance the knee?





Explanation

In a fixed valgus knee that is tight in both flexion and extension, the Iliotibial (IT) band is typically the first structure addressed (often via pie-crusting) because it serves as a major deforming force in both joint spaces. The popliteus primarily affects the flexion gap, while the LCL and lateral head of the gastrocnemius primarily affect the extension gap.

Question 4

A 25-year-old male sustains a traumatic spondylolisthesis of the axis (Hangman's fracture) following an MVA. Radiographs and CT demonstrate severe angulation of C2 on C3 with minimal translation. Flexion-extension views (done previously at an outside facility) show widening of the C2-C3 posterior disc space with flexion. According to the Levine and Edwards classification, what is the most appropriate management?





Explanation

This describes a Type IIA Hangman's fracture (severe angulation, minimal translation, disruption of the posterior C2-C3 disc space). Traction is strictly contraindicated as it will further widen the disc space and distract the fracture, leading to neurologic compromise. The treatment is closed reduction with slight extension and compression under fluoroscopy, followed by immobilization in a Halo vest.

Question 5

When comparing autografts for anterior cruciate ligament (ACL) reconstruction, which of the following accurately describes the biomechanical properties of a 10-mm bone-patellar tendon-bone (BPTB) graft compared to the native ACL?





Explanation

A 10-mm BPTB graft has an ultimate failure load of approximately 2977 N and stiffness of 620 N/mm. The native ACL has an ultimate load of approximately 2160 N and stiffness of 242 N/mm. Therefore, the 10-mm BPTB graft possesses both a higher ultimate load and higher stiffness compared to the native ACL.

Question 6

A 14-year-old male undergoes neoadjuvant chemotherapy followed by wide surgical resection of an osteosarcoma of the distal femur. Pathological evaluation of the resected specimen is performed. Which of the following findings is the most significant predictor of long-term survival?





Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the single most important prognostic factor for long-term survival in conventional high-grade osteosarcoma. Greater than 90% necrosis (Huvos grade III or IV) defines a 'good responder' and is associated with significantly higher survival rates compared to poor responders.

Question 7

A 42-year-old manual laborer presents with chronic wrist pain. Radiographs reveal a scaphoid nonunion with radioscaphoid arthritis and capitolunate arthritis, but the radiolunate joint is preserved. This corresponds to a stage III Scaphoid Nonunion Advanced Collapse (SNAC). Which of the following is the most appropriate surgical treatment?





Explanation

In SNAC Stage III, arthritis involves both the radioscaphoid and capitolunate joints, while the radiolunate joint is typically spared. Because the head of the capitate is arthritic, a proximal row carpectomy (PRC) is contraindicated (PRC relies on a pristine capitate head articulating with the lunate fossa). Therefore, scaphoid excision and four-corner fusion (capitate, hamate, lunate, triquetrum) is the motion-preserving procedure of choice.

Question 8

A 28-year-old football player sustains a hyperplantarflexion injury to his midfoot. Non-weight-bearing radiographs appear normal. Weight-bearing radiographs reveal a 3 mm diastasis between the base of the first and second metatarsals. What is the most appropriate definitive management?





Explanation

A diastasis >2 mm between the first and second metatarsal bases on weight-bearing radiographs indicates an unstable Lisfranc injury. Unstable injuries require surgical stabilization, either through ORIF or primary arthrodesis (which is increasingly favored for purely ligamentous injuries). Non-operative management is strictly reserved for stable injuries with absolutely no displacement on weight-bearing views.

Question 9

Romosozumab has been introduced for the treatment of severe osteoporosis. What is the precise cellular mechanism of action of this monoclonal antibody?





Explanation

Romosozumab is a monoclonal antibody that binds to and inhibits sclerostin. Sclerostin is an endogenous inhibitor of the Wnt/beta-catenin signaling pathway produced by osteocytes. By inhibiting sclerostin, Romosozumab promotes Wnt signaling, which significantly increases bone formation (anabolic effect) and also decreases bone resorption.

Question 10

A 12-year-old obese male presents to the emergency department unable to bear weight on his right leg for the past 24 hours after a minor fall. Radiographs confirm a severe, unstable slipped capital femoral epiphysis (SCFE). Which of the following complications is he at the highest risk for developing compared to a patient with a stable SCFE?





Explanation

An unstable SCFE is defined by the inability of the patient to bear weight, even with crutches (Loder classification). Unstable SCFE has a notoriously high rate of avascular necrosis (AVN) of the femoral head, ranging from 20-50%, compared to stable SCFE, where AVN is extremely rare (<1%).

Question 11

A 30-year-old male sustains a vertical femoral neck fracture (Pauwels Type III, 70-degree angle) following a fall from height. Which of the following fixation constructs offers the greatest biomechanical stability against the predominant deforming shear forces?





Explanation

Pauwels Type III fractures are highly vertical and experience massive shear forces, leading to high rates of nonunion and varus collapse. Biomechanical studies have demonstrated that a fixed-angle device, such as a sliding hip screw (dynamic hip screw), combined with an anti-rotation screw provides superior resistance to shear forces and a more stable construct than multiple parallel cancellous screws for vertical neck fractures in young adults.

Question 12

A 55-year-old female undergoes a primary total hip arthroplasty using a ceramic-on-ceramic bearing. At 2-year follow-up, she complains of an audible squeaking noise from the hip during specific movements. Which of the following acetabular component positions is most strongly associated with the development of this complication?





Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which typically occurs due to component malposition, specifically excessive acetabular inclination (vertical cup) and/or excessive anteversion. Edge loading leads to loss of fluid film lubrication and stripe wear on the femoral head.

Question 13

A 22-year-old rugby player has recurrent anterior shoulder instability. CT arthrogram reveals a glenoid bone loss of 12% and a large Hill-Sachs lesion. Applying the glenoid track concept, the Hill-Sachs lesion is calculated to be 'off-track.' Which of the following surgical strategies is most appropriate to restore stability?





Explanation

An 'off-track' Hill-Sachs lesion means the lesion engages the anterior glenoid rim during abduction and external rotation. If glenoid bone loss is subcritical (<15-20%) but the lesion is off-track, an arthroscopic Bankart repair combined with a Remplissage (infraspinatus tenodesis and capsulodesis into the defect) converts it to an on-track lesion and prevents engagement. Latarjet is generally reserved for glenoid bone loss >15-20%.

Question 14

Following a zone II flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) repair using a 4-strand core suture and epitendinous repair, what is the primary advantage of utilizing an early active motion rehabilitation protocol compared to immobilization or passive-only protocols?





Explanation

Early active motion protocols (using multi-strand robust repairs) promote tendon gliding and excursion. The primary functional advantage of increased tendon excursion is the prevention of peritendinous adhesions, which are notorious in Zone II ('no man/'s land'), resulting in superior final range of motion. It does not necessarily decrease the absolute risk of rupture compared to strict immobilization.

Question 15

A 40-year-old recreational athlete sustains an acute, closed Achilles tendon rupture. In discussing operative versus non-operative management with a functional rehabilitation protocol, which of the following accurately reflects the current evidence from randomized controlled trials?





Explanation

Recent high-quality RCTs (such as Willits et al.) have demonstrated that when an early functional rehabilitation protocol (weight-bearing and early ROM in a boot) is employed, non-operative management of acute Achilles tendon ruptures yields a re-rupture rate that is not statistically different from operative management, whilst entirely avoiding surgical risks like infection, wound breakdown, and sural nerve injury.

Question 16

A 60-year-old male presents with deep hip pain. Radiographs show a large, purely lytic lesion in the periacetabular ilium with endosteal scalloping and focal cortical breakthrough. Biopsy confirms a Grade II (intermediate-grade) conventional chondrosarcoma. What is the treatment of choice?





Explanation

Conventional chondrosarcomas are notoriously resistant to both chemotherapy and radiation therapy. For intermediate (Grade II) and high-grade (Grade III) lesions, as well as any conventional chondrosarcoma with aggressive imaging features (cortical breakthrough, large size in pelvis), the definitive treatment is wide surgical resection alone to achieve negative margins.

Question 17

A 68-year-old male complains of bilateral posterior leg pain that worsens with walking and is relieved by sitting. Which of the following historical or physical examination findings is most specific for differentiating neurogenic claudication (lumbar spinal stenosis) from vascular claudication?





Explanation

The bicycle test of van Gelderen classically differentiates neurogenic from vascular claudication. Patients with neurogenic claudication lean forward while cycling, which flexes the spine, increases the spinal canal cross-sectional area, and prevents symptoms. Vascular claudication is worsened by the metabolic demand of cycling regardless of posture, and is classically relieved by simply standing still.

Question 18

A 32-year-old male is admitted with a comminuted tibia fracture. He develops increasing pain out of proportion to the injury. His blood pressure is 110/70 mmHg. Intracompartmental pressure monitoring of the anterior compartment yields a pressure of 45 mmHg. What is his Delta P, and what is the indicated management?





Explanation

Delta P is calculated as Diastolic Blood Pressure minus Compartment Pressure (70 - 45 = 25 mmHg). A Delta P of less than 30 mmHg (or an absolute compartment pressure within 30 mmHg of the diastolic pressure) is the widely accepted threshold indicating acute compartment syndrome, which mandates emergent fasciotomy.

Question 19

A 2-week-old infant is diagnosed with idiopathic congenital talipes equinovarus (clubfoot). The treating orthopedic surgeon initiates the Ponseti method of serial casting. In what sequential order are the components of the deformity corrected?





Explanation

The Ponseti method systematically corrects the deformities of clubfoot in a specific sequence, remembered by the mnemonic CAVE: Cavus (corrected first by elevating the first ray to align the forefoot with the hindfoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy as the final step).

Question 20

Articular cartilage is divided into four distinct structural zones. Which of the following accurately describes the properties of the superficial (tangential) zone?





Explanation

The superficial (tangential) zone of articular cartilage comprises the top 10-20% of thickness. It uniquely possesses the highest water content, the lowest proteoglycan content, and type II collagen fibers that are densely packed and oriented parallel to the joint surface. This parallel alignment provides maximum tensile strength to resist shear forces.

Question 21

A 35-year-old male is brought to the emergency department after falling from a 15-foot scaffold. He complains of severe back pain. Neurological examination reveals 4/5 weakness in the extensor hallucis longus bilaterally, with intact bowel and bladder function. CT of the lumbar spine shows an L1 burst fracture with 40% loss of anterior vertebral body height and retropulsion of a bone fragment into the spinal canal. MRI confirms high T2 signal indicating complete disruption of the posterior ligamentous complex. According to the Thoracolumbar Injury Classification and Severity (TLICS) score, what is this patient's total score?





Explanation

The TLICS system scores injuries based on three categories: 1) Morphology: Burst fracture = 2 points. 2) Neurologic status: Incomplete spinal cord or nerve root injury = 3 points. 3) Posterior Ligamentous Complex (PLC) integrity: Disrupted = 3 points. The patient has a burst morphology (2), an incomplete neurological deficit (3), and a disrupted PLC (3). Total score = 2 + 3 + 3 = 8. A score > 4 is considered a strong indication for surgical intervention.

Question 22

A 24-year-old professional rugby player presents with a history of five anterior shoulder dislocations. A 3D CT scan of the shoulder reveals 28% anterior glenoid bone loss and a concomitant engaging Hill-Sachs lesion. He wishes to return to professional contact sports. What is the most appropriate surgical intervention?





Explanation

Anterior glenoid bone loss greater than 20-25% in the setting of recurrent anterior instability, especially in a collision athlete with an engaging Hill-Sachs lesion, is an absolute indication for a bony augmentation procedure. The open Latarjet procedure (coracoid transfer) is the gold standard in this scenario. Soft tissue procedures (Arthroscopic or Open Bankart, even with Remplissage) have an unacceptably high failure rate when critical glenoid bone loss (>20-25%) is present.

Question 23

A 28-year-old male presents with a slowly enlarging, painful mass deep in the thigh near the knee joint. Biopsy reveals a biphasic tumor with both epithelial and spindle cell components. Cytogenetic analysis is ordered. Which of the following chromosomal translocations is highly specific for this diagnosis?





Explanation

The clinical scenario and biopsy describe a Synovial Sarcoma. The highly specific chromosomal translocation for synovial sarcoma is t(X;18)(p11.2;q11.2), which results in the SYT-SSX fusion gene. t(11;22) is Ewing's sarcoma; t(9;22) is Extraskeletal myxoid chondrosarcoma; t(2;13) is Alveolar rhabdomyosarcoma; t(12;16) is Myxoid liposarcoma.

Question 24

A 55-year-old manual laborer presents with chronic progressive wrist pain and limited range of motion. Radiographs demonstrate advanced degenerative changes involving the radioscaphoid joint and the capitolunate joint. The radiolunate joint is perfectly preserved. This radiographic pattern is best described as Stage III Scapholunate Advanced Collapse (SLAC). What is the most appropriate surgical treatment to relieve pain while preserving some wrist motion?





Explanation

Stage III SLAC wrist involves arthritis of the radioscaphoid and capitolunate joints while sparing the radiolunate joint. Proximal row carpectomy (PRC) is contraindicated in Stage III SLAC because the capitate articular surface is compromised, which would lead to painful capitoradial articulation. The procedure of choice to maintain motion and relieve pain when the capitolunate joint is arthritic (Stage III SLAC) is a four-corner arthrodesis (capitate, hamate, lunate, triquetrum) with scaphoid excision, which relies on the preserved radiolunate joint.

Question 25

During a primary Total Knee Arthroplasty (TKA), the surgeon inserts trial components. Assessment of the gaps reveals that the knee is symmetrically excessively tight in both full extension and 90 degrees of flexion. Which of the following is the most appropriate next step to balance the knee?





Explanation

When a TKA is symmetrically tight in BOTH flexion and extension, the problem lies on the tibial side, as the tibial cut affects both gaps equally. The correct action is to either use a thinner tibial polyethylene insert (if not already at the minimum thickness) or resect more proximal tibia. Resecting more distal femur would only loosen the extension gap. Decreasing the femoral component size would only loosen the flexion gap.

Question 26

A 2-week-old infant is brought to the clinic with an idiopathic clubfoot. The treating orthopedic surgeon plans to initiate the Ponseti method of serial casting. According to the principles of the Ponseti method, what is the first step in correcting the complex deformity of the foot?





Explanation

The Ponseti method addresses clubfoot deformities in a specific sequence summarized by the acronym CAVE: Cavus, Adductus, Varus, Equinus. The very first step is to correct the cavus deformity. This is achieved by supinating the forefoot and elevating (dorsiflexing) the first ray to align the forefoot with the hindfoot.

Question 27

A 35-year-old unrestrained driver is involved in a motor vehicle collision. Radiographs and CT imaging reveal an intra-articular distal femur fracture with a separate, displaced fracture of the posterior aspect of the lateral femoral condyle. This posterior condylar fracture (Hoffa fracture) occurs most commonly in which plane?





Explanation

A Hoffa fracture is a tangential, unicondylar fracture of the posterior aspect of the distal femur. It occurs classically in the coronal plane. It is often missed on plain AP and lateral radiographs and usually requires a CT scan for accurate diagnosis and surgical planning. Fixation generally involves anterior-to-posterior or posterior-to-anterior lag screws.

Question 28

Which of the following calcium-based bone graft substitutes possesses the highest compressive strength but has the slowest rate of resorption in vivo?





Explanation

Calcium phosphate cements have the highest compressive strength among the common synthetic bone graft substitutes, making them useful for filling metaphyseal voids where structural support is temporarily needed (e.g., tibial plateau fractures). However, they are resorbed very slowly by osteoclasts (months to years). Calcium sulfate resorbs very rapidly (4-8 weeks) but has low structural strength. Tricalcium phosphate has intermediate properties.

Question 29

A 56-year-old female presents with an acquired flatfoot deformity. Examination shows a flexible hindfoot but an inability to perform a single-leg heel rise. Standing AP radiographs of the foot reveal that more than 40% of the talar head is uncovered by the navicular, indicating significant forefoot abduction. What is her posterior tibial tendon dysfunction (PTTD) stage and most appropriate surgical management?





Explanation

The patient has a flexible hindfoot, placing her in Stage II PTTD. Stage II is subdivided into IIA and IIB. Stage IIB is characterized by significant forefoot abduction (>40% talonavicular uncoverage on AP radiograph). A medial displacement calcaneal osteotomy (MDCO) alone does not sufficiently correct severe forefoot abduction. Therefore, Stage IIB requires a lateral column lengthening (e.g., Evans osteotomy) in addition to an FDL transfer and MDCO.

Question 30

A 42-year-old male presents to the emergency department with acute lower back pain radiating down both legs after lifting a heavy box. Which of the following is considered the most consistent and earliest clinical sign of cauda equina syndrome?





Explanation

Urinary retention is the most sensitive and often the earliest clinical symptom of cauda equina syndrome (CES). The post-void residual (PVR) volume will be abnormally high (typically >100-200 mL). Bowel incontinence and frank saddle anesthesia may develop slightly later as the sacral roots are further compressed. The absence of urinary retention makes CES highly unlikely.

Question 31

A 9-year-old boy (Tanner stage 1) sustains a midsubstance ACL tear while playing soccer. Non-operative management fails, and he experiences recurrent instability. Surgical intervention is planned. To minimize the risk of growth arrest and angular deformity, which of the following techniques is considered the most appropriate standard of care?





Explanation

In a skeletally immature patient with wide-open physes (Tanner stage 1), drilling standard transphyseal tunnels risks significant growth arrest and angular deformity. The best accepted surgical technique to minimize physeal injury while restoring intra-articular stability is a physeal-sparing all-epiphyseal reconstruction (or an extra-articular Iliotibial band tenodesis such as the MacIntosh procedure, though all-epiphyseal is an intra-articular choice). BTB and standard transphyseal interference screws are contraindicated due to the high risk of physeal damage.

Question 32

A 'floating shoulder' injury consists of ipsilateral fractures of the clavicular shaft and the scapular neck. Surgical fixation of the clavicle is often recommended to stabilize the shoulder girdle. Which of the following criteria is an absolute indication for operative fixation of the scapula body/neck in this scenario?





Explanation

Operative indications for scapular neck fractures (with or without a clavicle fracture) include a Glenoid Polar Angle (GPA) of < 20 degrees (normal is 30-45 degrees), medialization of the glenoid > 20 mm (not 5 mm), and angular deformity > 40 degrees. A GPA < 20 degrees severely alters the rotator cuff biomechanics and represents a strong indication for ORIF.

Question 33

Recombinant human bone morphogenetic proteins (rhBMPs) are utilized in orthopedics to promote bone healing. Which specific rhBMP is currently FDA-approved as an adjunct to intramedullary nail fixation for acute, open tibial shaft fractures?





Explanation

rhBMP-2 (Infuse) is FDA-approved for acute open tibial shaft fractures treated with an intramedullary nail (within 14 days of injury), as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 (OP-1) was previously approved under a humanitarian device exemption for recalcitrant tibial nonunions, not acute fractures. BMP-3 actually inhibits osteogenesis.

Question 34

A 13-year-old boy is diagnosed with a stable Slipped Capital Femoral Epiphysis (SCFE) of the left hip. He undergoes in situ percutaneous pinning. What is the ideal position of the single screw in the epiphysis to provide maximum stability and minimize the risk of joint penetration?





Explanation

The ideal starting point and trajectory for in situ pinning of a SCFE is on the anterior aspect of the femoral neck, directed perpendicular to the physis, to end in the center-center position of the epiphysis. This position reduces the risk of in-out-in joint penetration and provides the most biomechanically stable construct for the displaced epiphysis.

Question 35

A 30-year-old mechanic presents with a swollen, painful index finger 3 days after a minor puncture wound to the volar aspect of his hand. You suspect pyogenic flexor tenosynovitis. Which of Kanavel's four cardinal signs is generally considered the most sensitive and often the earliest finding in this condition?





Explanation

Kanavel's four cardinal signs of flexor tenosynovitis are: 1) Fusiform swelling of the digit, 2) Flexed resting posture, 3) Tenderness along the entire course of the flexor tendon sheath, and 4) Pain with passive extension. Pain with passive extension is considered the most sensitive and earliest sign of infectious flexor tenosynovitis.

Question 36

A 48-year-old man who underwent a primary Total Hip Arthroplasty (THA) 3 years ago presents to the clinic complaining of an audible 'squeaking' sound coming from his hip during ambulation. He denies pain, and radiographs show well-fixed components. This complication is exclusively associated with which of the following bearing surface combinations?





Explanation

Squeaking is a unique complication primarily associated with Ceramic-on-Ceramic (CoC) bearing surfaces in THA. The exact etiology is multifactorial but is strongly linked to component malposition (e.g., steep acetabular cup causing edge loading), stripe wear, or third-body wear. It rarely occurs with other bearing combinations.

Question 37

A 29-year-old female presents with knee pain. Radiographs reveal an eccentric, lytic, expansile lesion in the distal femoral epiphysis extending to the subchondral bone. Biopsy confirms Giant Cell Tumor of Bone (GCT). If medical management is considered prior to surgery, what is the mechanism of action of the preferred targeted therapeutic agent (Denosumab)?





Explanation

Denosumab is a fully human monoclonal antibody that binds to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL), preventing RANKL from activating RANK on the surface of osteoclasts and their precursors. In Giant Cell Tumor of bone, the neoplastic mononuclear cells express RANKL, which recruits reactive osteoclast-like giant cells that cause bone destruction. Denosumab blocks this process.

Question 38

A 25-year-old athlete sustains a hyperplantarflexion injury to his midfoot. Weight-bearing radiographs demonstrate widening of the interval between the first and second metatarsal bases without associated fractures (purely ligamentous Lisfranc injury). According to current literature, what surgical treatment is associated with the most predictable, best long-term outcome for a purely ligamentous Lisfranc injury?





Explanation

For primarily ligamentous Lisfranc injuries, multiple prospective randomized studies (e.g., Ly and Coetzee, 2006) have shown that primary arthrodesis of the medial column (1st, 2nd, and 3rd TMT joints) results in superior functional outcomes, less pain, and lower revision rates compared to ORIF. ORIF relies on ligamentous healing, which is unpredictable and often leads to secondary midfoot collapse and arthritis in purely ligamentous injuries.

Question 39

A 22-year-old male suffers a highly comminuted closed tibia fracture. In the emergency department, he complains of severe pain out of proportion to the injury. The clinical exam is equivocal for compartment syndrome. You decide to measure intracompartmental pressures. What is the generally accepted threshold defining the critical 'delta P' that indicates a need for emergency fasciotomy?





Explanation

The delta P (ΔP) is calculated as the Diastolic Blood Pressure minus the Intracompartmental Pressure. A ΔP of less than 30 mmHg signifies that the tissue perfusion pressure is inadequate, and it is the most reliable threshold for diagnosing acute compartment syndrome and indicating the need for emergency fasciotomy. Absolute pressure measurements are less reliable as they do not account for patient hypotension.

Question 40

A 16-year-old elite female gymnast presents with insidious onset lower back pain that worsens with extension activities. Oblique radiographs of the lumbar spine demonstrate a 'collar on the Scotty dog'. According to the Wiltse classification of spondylolisthesis, what type of defect does this patient have?





Explanation

The patient has a pars interarticularis defect (spondylolysis), classically seen as a 'collar on the Scotty dog' on oblique radiographs. In the Wiltse classification of spondylolisthesis, a pars defect (often a stress/fatigue fracture common in gymnasts) is classified as Type II (Isthmic). Type I is Dysplastic (congenital abnormality of the upper sacrum or L5 arch), Type III is Degenerative, Type IV is Traumatic (fractures of the posterior arch other than the pars), and Type V is Pathologic.

Question 41

A 65-year-old Asian male presents with progressive clumsiness in his hands, difficulty fastening buttons, and an unsteady gait. Radiographs and MRI demonstrate continuous ossification of the posterior longitudinal ligament (OPLL) from C3 to C6, causing >60% canal stenosis. His cervical spine alignment demonstrates rigid kyphosis (K-line negative). Which of the following surgical strategies is the most appropriate?





Explanation

In patients with severe OPLL and a kyphotic cervical alignment (K-line negative), posterior decompression alone (laminectomy or laminoplasty) is inadequate because the spinal cord will remain draped over the anterior pathology and will not drift backward. Anterior decompression alone for massive, multi-level OPLL carries a high risk of dural tears, construct failure, and graft dislodgment. Therefore, a combined anterior-posterior approach (or an anterior approach with posterior instrumentation for stability) is the most reliable strategy to adequately decompress the cord and stabilize the spine in a K-line negative patient.

Question 42

During a primary posterior-stabilized total knee arthroplasty (TKA), the surgeon evaluates the joint gaps after making the initial bony cuts. The knee is perfectly balanced and symmetric in full extension, but the flexion gap is unacceptably tight. What is the most appropriate surgical step to balance the knee?





Explanation

A knee that is balanced in extension but tight in flexion requires an intervention that selectively increases the flexion gap. Decreasing the size of the femoral component (when using an anterior referencing system) will take more posterior condylar bone, thereby increasing the flexion gap without affecting the extension gap. Alternatively, increasing the posterior slope of the tibial cut increases the flexion gap more than the extension gap. Releasing the posterior capsule or cutting more distal femur would primarily affect the extension gap.

Question 43

A 6-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the left hip (DDH). At the routine 2-week follow-up, the parents report that the child has stopped kicking the left leg. On examination, the infant exhibits absent active knee extension on the left side, although foot and ankle movements are intact. What is the most likely iatrogenic cause of this complication?





Explanation

The clinical presentation describes a femoral nerve palsy, which is a known complication of the Pavlik harness. It is typically caused by excessive hyperflexion of the hips, which compresses the femoral nerve against the inguinal ligament. Treatment involves adjusting the harness to decrease hip flexion or temporarily discontinuing the harness until nerve function returns. Hyperabduction of the hips, conversely, is associated with avascular necrosis (AVN) of the femoral head.

Question 44

A 35-year-old male arrives at the trauma bay with hemodynamic instability following a crush injury to the pelvis. AP pelvis radiograph demonstrates an anteroposterior compression (APC III) injury with an "open book" pelvic ring disruption. A pelvic binder is ordered. To most effectively reduce the pelvic volume and provide a tamponade effect, the binder should be centered precisely over which of the following anatomic landmarks?





Explanation

Pelvic binders and sheets are most effective at reducing pelvic volume and closing an "open book" pelvic ring disruption when they are centered over the greater trochanters. A common error is placing the binder too high over the iliac crests, which is mechanically inferior and can inadvertently force the inferior aspect of the pelvis wider.

Question 45

A 32-year-old male carpenter presents with chronic dorsal wrist pain and weak grip strength. Radiographs reveal sclerosis, fragmentation, and collapse of the lunate. The radioscaphoid angle is measured at 65 degrees, indicating fixed scaphoid rotation, and carpal height is decreased. Ulnar variance is neutral. According to the Lichtman classification, this represents Stage IIIB Kienbock's disease. What is the most appropriate surgical treatment?





Explanation

The patient has Lichtman Stage IIIB Kienbock's disease, characterized by lunate fragmentation/collapse, carpal collapse, and fixed scaphoid rotation (scaphoid angle > 60 degrees). At this advanced stage with altered carpal kinematics, joint-leveling procedures (like radial shortening osteotomy, which are excellent for Stage II/IIIA with ulnar minus variance) are no longer effective. Salvage procedures such as Proximal Row Carpectomy (PRC) or limited intercarpal fusions (e.g., STT or SC fusion) are indicated to address the collapse and provide a stable, pain-free wrist.

Question 46

A 24-year-old elite baseball pitcher complains of deep shoulder pain that worsens during the late cocking phase of throwing. MRI arthrogram reveals a Superior Labrum Anterior to Posterior (SLAP) tear that extends substantially into the long head of the biceps tendon, with more than 50% of the tendon detached and frayed. According to the Snyder classification, what is this injury type, and what is the generally recommended treatment in symptomatic adults?





Explanation

A Snyder Type IV SLAP tear involves a bucket-handle tear of the superior labrum that extends into the long head of the biceps tendon. When there is significant involvement (>30-50% tearing) of the biceps tendon, biceps tenodesis (or tenotomy in older/lower demand patients) is the treatment of choice to relieve pain and remove the damaged tendon. Type II is detachment of the superior labrum and biceps anchor from the glenoid (treated with repair). Type III is a bucket-handle tear of the labrum with an intact biceps anchor (treated with excision of the tear).

Question 47

Ligaments and tendons exhibit viscoelastic behavior. Which of the following statements best defines the mechanical concept of "stress relaxation" in an orthopedic biologic tissue?





Explanation

Stress relaxation is a classic viscoelastic property where the stress (internal force) within a material decreases over time when it is stretched and held at a constant length (constant deformation/strain). Creep (Option A) is the gradual increase in length (deformation) when a constant load/stress is applied. Hysteresis (Option C) refers to the energy dissipated (usually as heat) during the loading and unloading cycle. Strain-rate dependency (Option D) explains why tissues become stiffer when loaded rapidly.

Question 48

A 23-year-old running back sustains a severe axial load to his foot while plantarflexed. Weight-bearing radiographs reveal a 3 mm diastasis between the bases of the first and second metatarsals. He is diagnosed with a Lisfranc injury. The primary stabilizing ligament that has been disrupted connects which two structures?





Explanation

The Lisfranc ligament is an oblique, stout interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the largest and most critical soft tissue stabilizer of the tarsometatarsal joint complex. There is notably no direct ligamentous connection between the base of the first and second metatarsals, which makes this joint structurally vulnerable.

Question 49

A 66-year-old female with a known history of multiple myeloma complains of progressively worsening pain in her right thigh. Radiographs demonstrate a purely lytic lesion in the peritrochanteric region of her right femur. The lesion spans 60% of the bone's cross-sectional diameter. She rates her pain as moderate, occurring mainly with weight-bearing. Applying Mirels' criteria, what is her cumulative score and the appropriate clinical recommendation?





Explanation

Mirels' scoring system determines the risk of pathologic fracture and the need for prophylactic fixation. It is based on 4 categories (1 to 3 points each): Site (Upper extremity=1, Lower extremity=2, Peritrochanteric=3); Pain (Mild=1, Moderate=2, Severe=3); Size (<1/3=1, 1/3-2/3=2, >2/3=3); and Radiographic nature (Blastic=1, Mixed=2, Lytic=3). For this patient: Site = Peritrochanteric (3); Pain = Moderate (2); Size = 60%, which is between 1/3 and 2/3 (2); Nature = Lytic (3). Total Score = 3 + 2 + 2 + 3 = 10. A score >= 9 dictates prophylactic internal fixation.

Question 50

A 50-year-old female who underwent open reduction and internal fixation of a distal radius fracture with a volar locking plate 4 months ago presents with the sudden inability to bend the tip of her thumb. She experienced a snapping sensation earlier that day without significant trauma. The most likely cause of this complication is:





Explanation

Attritional rupture of the flexor pollicis longus (FPL) tendon is a well-recognized complication of volar plate fixation for distal radius fractures. It usually occurs when the plate is placed distally beyond the watershed line of the distal radius, creating friction against the FPL tendon during thumb motion. EPL rupture is common in non-operatively managed distal radius fractures, but FPL rupture is the classic complication of prominent volar hardware.

Question 51

When evaluating an adolescent idiopathic scoliosis (AIS) patient using the Lenke classification system, structural characteristics of the curves dictate the curve type (1-6). If a patient has a structural main thoracic curve and a structural proximal thoracic curve, but the thoracolumbar curve bends out to 10 degrees on side-bending films (non-structural), what is the correct Lenke curve type?





Explanation

The Lenke classification for AIS is based on identifying structural curves (defined as a curve >= 25 degrees on coronal side-bending films or > 20 degrees of kyphosis on the sagittal film). Lenke Type 1 is a structural main thoracic curve only. Lenke Type 2 (Double Thoracic) has a structural proximal thoracic curve and a structural main thoracic curve, while the thoracolumbar curve is non-structural. Lenke Type 3 is a structural MT and structural TL/L. Lenke 4 has all three structural. Lenke 5 is structural TL/L only.

Question 52

To minimize the risk of dislocation following primary total hip arthroplasty (THA), Lewinnek defined a "safe zone" for the orientation of the acetabular component. Which of the following represents the classic Lewinnek safe zone parameters for cup placement?





Explanation

Lewinnek's classic 'safe zone' for acetabular cup orientation is defined as 40 +/- 10 degrees of inclination (abduction angle) and 15 +/- 10 degrees of anteversion. Therefore, the range is 30 to 50 degrees of inclination and 5 to 25 degrees of anteversion. Implants placed outside this zone have traditionally been associated with a significantly higher risk of dislocation, though modern literature emphasizes combined anteversion and spinopelvic mobility as well.

Question 53

A patient is admitted for an elective primary total hip arthroplasty. He is currently taking Rivaroxaban, which needs to be managed perioperatively. What is the specific mechanism of action by which Rivaroxaban exerts its anticoagulant effect?





Explanation

Rivaroxaban and Apixaban are direct oral anticoagulants (DOACs) that work by directly and reversibly inhibiting Factor Xa, preventing the conversion of prothrombin to thrombin. Dabigatran directly inhibits Factor IIa (Thrombin). Warfarin inhibits Vitamin K epoxide reductase. Heparins work by enhancing Antithrombin III.

Question 54

A 22-year-old male is diagnosed with a displaced fracture of the proximal pole of the scaphoid. He is informed that this specific fracture pattern carries a high risk of avascular necrosis and nonunion. What anatomical feature of the scaphoid's blood supply accounts for this vulnerability?





Explanation

The major blood supply to the scaphoid is derived from the radial artery, primarily via the dorsal carpal branch. The vessels enter the scaphoid at the distal pole and dorsal ridge, flowing in a retrograde direction to supply the proximal pole. Because the blood supply travels from distal to proximal, a fracture across the waist or proximal pole severs the blood supply to the proximal fragment, leading to a high rate of avascular necrosis and nonunion.

Question 55

A 13-year-old obese male presents with left groin pain and a limp. Examination reveals obligate external rotation with hip flexion. Radiographs demonstrate a severe Slipped Capital Femoral Epiphysis (SCFE) on the left side. The right hip is asymptomatic and radiographically normal. Under which of the following circumstances is prophylactic in situ pinning of the contralateral (right) hip most strongly indicated?





Explanation

While the decision to perform prophylactic contralateral pinning in SCFE is debated in idiopathic cases, the absolute indication universally recognized is the presence of an underlying endocrine or metabolic disorder (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or previous radiation therapy. These patients have an extremely high risk (>50-80%) of bilateral involvement. Other relative indications often include young age (e.g., <10 for boys) or inability to follow up reliably.

Question 56

A 25-year-old male sustains a twisting knee injury during a rugby match. On physical examination, the dial test reveals 20 degrees of increased external rotation of the tibia compared to the contralateral leg when the knee is flexed to 30 degrees. However, when the knee is flexed to 90 degrees, the external rotation is symmetric bilaterally. This physical exam finding is most consistent with an isolated injury to which structure(s)?





Explanation

The dial test assesses the integrity of the posterolateral corner (PLC) and posterior cruciate ligament (PCL). Increased external rotation (>10 degrees difference compared to the normal side) at 30 degrees of flexion, but symmetric rotation at 90 degrees, indicates an isolated injury to the PLC. If the dial test demonstrates increased external rotation at both 30 degrees and 90 degrees of flexion, it indicates a combined injury to both the PLC and the PCL.

Question 57

A 28-year-old male presents with a femoral neck fracture sustained in a fall from height. Radiographs show a vertically oriented fracture line with an angle of 75 degrees relative to the horizontal (Pauwels Type III). He undergoes urgent surgical fixation. Biomechanically, what is the most appropriate fixation construct to neutralize the predominantly high shear forces in this fracture pattern?





Explanation

Pauwels Type III femoral neck fractures are vertically oriented (>50 degrees), which subjects the fracture site to high shear forces and varus displacing moments, leading to higher failure rates with traditional parallel cannulated screws. Biomechanical studies indicate that fixed-angle constructs, such as a sliding hip screw (SHS) combined with an anti-rotation screw, or a proximal femoral locking plate, provide significantly greater stability against shear forces and are preferred for this vertical fracture pattern in young adults.

Question 58

A 40-year-old male undergoes percutaneous repair of an acute, mid-substance Achilles tendon rupture. Postoperatively, he complains of burning pain and numbness along the lateral aspect of his foot and lateral heel. Which nerve is most likely at risk and potentially injured during a percutaneous or minimally invasive Achilles repair?





Explanation

The sural nerve is at high risk during percutaneous or minimally invasive repairs of the Achilles tendon. It courses down the posterolateral aspect of the calf, crossing the lateral border of the Achilles tendon from lateral to medial, typically about 10 to 12 cm proximal to the calcaneal insertion. Blind passage of sutures or needles in this proximal region frequently captures or injures the sural nerve.

Question 59

In the field of orthopedic biomaterials, implant failure can occasionally be traced to corrosion. Galvanic corrosion is most accurately described by which of the following scenarios?





Explanation

Galvanic corrosion occurs when two different metals with differing anodic indices (e.g., stainless steel and titanium) are placed in direct electrical contact within a conductive fluid (such as serum or interstitial fluid), creating an electrochemical cell where the less noble metal corrodes rapidly. Option B describes crevice corrosion (low oxygen tension). Option A describes fretting corrosion.

Question 60

A 16-year-old male presents with severe pain and swelling in his distal thigh. Radiographs display a destructive metaphyseal lesion with a "sunburst" periosteal reaction and Codman's triangle. MRI suggests an intramedullary osteosarcoma. You plan to perform an open biopsy. Which of the following is an essential surgical oncology principle regarding the biopsy technique?





Explanation

The biopsy tract in a suspected malignant bone tumor is considered contaminated with tumor cells. A fundamental principle of orthopedic oncology is that the biopsy tract must be meticulously planned (usually longitudinally) so that it lies directly within the planned definitive surgical incision. This allows the entire tract to be completely excised en bloc with the tumor during the definitive wide resection. Transverse incisions or traversing clean compartments drastically complicates future limb-salvage surgery and may necessitate amputation.

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