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Arab Orthopaedic Board MCQs - Part 9

27 Apr 2026 101 min read 73 Views
Arab Ortho Board MCQs - Part 8

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Learn more about Arab Orthopaedic Board MCQs - Part 9 and how to manage it. Practice Arab Orthopaedic Board MCQs Part 9. Review orthopedic surgery questions 401 to 450 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 9

Comprehensive 100-Question Exam


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Question 1

A 45-year-old male presents with chronic wrist pain and a known scaphoid nonunion. Radiographs show arthritic changes involving the radioscaphoid joint and midcarpal joint (capitolunate), but the radiolunate joint is preserved. What is the most appropriate surgical treatment?





Explanation

This patient has Scaphoid Nonunion Advanced Collapse (SNAC) stage 3, which involves arthritis of the radioscaphoid and capitolunate joints, while sparing the radiolunate joint. Proximal row carpectomy (PRC) relies on a pristine capitate head articulating with the lunate fossa; therefore, PRC is contraindicated when the capitate is arthritic. Four-corner fusion (capitate, lunate, triquetrum, hamate) with scaphoid excision is the treatment of choice as it relies on the preserved radiolunate articulation.

Question 2

A 14-year-old boy presents with a diaphyseal femur lesion showing an 'onion skin' periosteal reaction. Biopsy shows small round blue cells. Which chromosomal translocation is most classically associated with this diagnosis?





Explanation

The clinical and radiographic presentation is classic for Ewing sarcoma. Ewing sarcoma is classically associated with the t(11;22) translocation, creating the EWS-FLI1 fusion protein (found in about 85% of cases). t(X;18) is associated with synovial sarcoma. t(12;16) is associated with myxoid liposarcoma. t(2;13) is associated with alveolar rhabdomyosarcoma. t(9;22) is the Philadelphia chromosome seen in CML and ALL.

Question 3

A 25-year-old soccer player sustains a knee injury. On physical examination, the Dial test shows 15 degrees of increased external rotation at 30 degrees of knee flexion compared to the contralateral side, but symmetric external rotation at 90 degrees. What structure is primarily injured?





Explanation

Increased external rotation of the tibia on the femur at 30 degrees of knee flexion, which reduces at 90 degrees, is indicative of an isolated posterolateral corner (PLC) injury. The primary stabilizers of the PLC are the LCL, popliteus tendon, and popliteofibular ligament. If external rotation were increased at both 30 and 90 degrees of flexion, it would suggest a combined injury of the PLC and the posterior cruciate ligament (PCL).

Question 4

A 30-year-old male sustains a midfoot injury after falling from a height. Radiographs show a widening between the bases of the 1st and 2nd metatarsals. What is the primary stabilizing structure of the affected joint complex?





Explanation

The patient has a Lisfranc injury. The Lisfranc ligament complex consists of dorsal, interosseous, and plantar ligaments. The interosseous Lisfranc ligament is the strongest and primary stabilizer of the Lisfranc complex, connecting the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. The plantar ligament is the second strongest, and the dorsal ligament is the weakest, which is why most dislocations occur dorsally.

Question 5

A 22-year-old male is involved in a high-speed motor vehicle collision while wearing a lap belt. Radiographs reveal a flexion-distraction injury of the L2 vertebra extending through the pedicles and posterior elements. Which concomitant injury is most likely to be found in this patient?





Explanation

Chance fractures (flexion-distraction injuries) sustained with seatbelts have a high association (up to 50%) with intra-abdominal injuries. Specifically, hollow viscus injuries (e.g., small bowel laceration or mesenteric avulsion) are extremely common due to the lap belt compressing the abdomen against the spine during deceleration. Immediate general surgery consultation and abdominal imaging are warranted.

Question 6

Following a primary total hip arthroplasty via a posterior approach, a patient experiences recurrent posterior dislocations. The acetabular component is found to be positioned in 45 degrees of abduction and 15 degrees of retroversion. What is the primary cause of instability?





Explanation

Lewinnek described the 'safe zone' for acetabular cup placement as 15 +/- 10 degrees of anteversion and 40 +/- 10 degrees of abduction. In this scenario, the cup is in 15 degrees of retroversion (insufficient anteversion). A retroverted acetabular component strongly predisposes the hip to posterior dislocation, particularly when the hip is placed in flexion and internal rotation.

Question 7

A 12-year-old obese male presents with left groin pain and an obligate external rotation of the hip during passive flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). Which of the following accurately describes the anatomic displacement in SCFE?





Explanation

In SCFE, the femoral head (epiphysis) actually remains anatomically seated in the acetabulum. The deformity is created by the femoral neck (metaphysis) displacing anteriorly and externally rotating relative to the epiphysis. Consequently, it appears as though the epiphysis has slipped posteriorly and medially. Klein's line (drawn along the superior femoral neck) will intersect LESS of the epiphysis on the affected side.

Question 8

Which of the following biomechanical terms best describes the phenomenon where a constant force applied to a viscoelastic material over a prolonged period results in increasing deformation?





Explanation

Creep is the progressive deformation of a material under a constant load over time. Stress relaxation is the decrease in stress over time when the material is held at a constant strain (constant deformation). Hysteresis relates to the loss of energy (usually as heat) during the loading and unloading cycles of a viscoelastic material. Orthopedic tissues like ligaments and cartilage exhibit both creep and stress relaxation.

Question 9

A 28-year-old carpenter sustains a laceration over the volar aspect of the proximal phalanx of the index finger, dividing both the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons. This injury corresponds to which flexor tendon zone?





Explanation

Zone II (historically known as 'No Man's Land') extends from the distal palmar crease (level of the A1 pulley) to the FDS insertion on the middle phalanx. It contains both FDS and FDP tendons coursing together within the narrow fibro-osseous sheath. Injuries here are notorious for adhesion formation. Zone I is distal to the FDS insertion. Zone III is the palm (lumbrical origin), Zone IV is the carpal tunnel, and Zone V is proximal to the carpal tunnel.

Question 10

A 35-year-old male sustains a closed tibial shaft fracture. Two hours post-admission, he complains of severe leg pain out of proportion to the injury, unrelieved by opioids. His blood pressure is 110/70 mmHg. What intracompartmental pressure reading would mandate immediate fasciotomy?





Explanation

The diagnosis of acute compartment syndrome is supported by a Delta P (Diastolic Blood Pressure minus Compartment Pressure) of 30 mmHg or less. Therefore, a compartment pressure within 30 mmHg of the diastolic blood pressure is indicative of compartment syndrome and an absolute indication for fasciotomy. Absolute pressures (e.g., >30 mmHg) are less reliable due to variations in systemic perfusion pressure.

Question 11

A 32-year-old female presents with knee pain. Radiographs reveal an eccentric, lytic, epiphyseal-metaphyseal lesion of the distal femur extending to the subchondral bone without a sclerotic rim. Biopsy shows multinucleated giant cells and mononuclear stromal cells. If treating with Denosumab, what is the precise cellular target of the drug?





Explanation

In Giant Cell Tumor (GCT) of bone, the actual neoplastic cells are the mononuclear spindle-like stromal cells. These cells express excess RANK Ligand (RANKL). This RANKL binds to the RANK receptors on the non-neoplastic multinucleated giant cells (which are osteoclast-like), recruiting them and causing massive bone resorption. Denosumab is a monoclonal antibody that targets and binds RANKL, effectively halting this destructive process.

Question 12

A 55-year-old patient with poorly controlled diabetes presents with a warm, swollen, erythematous left foot. Radiographs show midfoot joint subluxation, osteopenia, and periarticular bony fragmentation/debris. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent?





Explanation

Eichenholtz Stage 1 (Fragmentation) is the acute developmental phase characterized by clinical inflammation (erythema, warmth, swelling) and radiographic findings of osteopenia, joint subluxation/dislocation, bony fragmentation, and debris. Stage 2 (Coalescence) shows absorption of fine debris and early fusion/sclerosis. Stage 3 (Consolidation) shows remodeling and stable deformity. Stage 0 is the inflammatory prodrome with normal radiographs.

Question 13

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following provides definitive evidence (Major Criteria) for the diagnosis of a periprosthetic joint infection (PJI)?





Explanation

Under the widely accepted MSIS and 2018 ICM criteria, Major Criteria (either of which definitively diagnoses PJI) are: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. The other options (elevated CRP, positive LE, a single positive culture, and elevated synovial WBC) are minor criteria that contribute points to the diagnostic algorithm but are not independently definitive.

Question 14

A 3-year-old girl is diagnosed with late-presenting developmental dysplasia of the hip (DDH). She undergoes an open reduction and a pelvic osteotomy. The surgeon performs a redirectional, complete innominate osteotomy that hinges on the pubic symphysis to provide anterolateral coverage of the femoral head. Which osteotomy was performed?





Explanation

The Salter osteotomy is a complete, trans-iliac redirectional osteotomy that hinges on the pubic symphysis to provide primarily anterolateral coverage for DDH. The Pemberton is an incomplete osteotomy that hinges on the triradiate cartilage, reducing acetabular volume. The Dega is also incomplete, hinging on the triradiate, but focuses on lateral and posterior coverage. The Chiari is a salvage capsular interposition osteotomy. Steel is a triple osteotomy (ilium, ischium, pubis).

Question 15

During secondary fracture healing, the process transitions through several distinct phases. Which type of collagen is synthesized primarily during the soft callus (cartilaginous) phase?





Explanation

Secondary fracture healing relies on endochondral ossification. During the soft callus phase, chondrocytes proliferate and synthesize a cartilaginous matrix rich in Type II collagen. Later, during the hard callus phase, these chondrocytes hypertrophy (secreting Type X collagen) and undergo apoptosis, while osteoblasts move in and deposit woven bone, which is primarily Type I collagen.

Question 16

A 19-year-old female basketball player undergoes ACL reconstruction using a bone-patellar tendon-bone (BTB) autograft. Six months postoperatively, her knee is stable, but she complains of focal pain at the harvest site. What is the most common complication specifically associated with BTB autograft harvest compared to hamstring autograft?





Explanation

Anterior knee pain (patellofemoral pain) is the most common morbidity specifically associated with harvest of the bone-patellar tendon-bone autograft, occurring in 10-30% of patients. Other risks specific to BTB include patellar tendon rupture or patella fracture. Hamstring graft harvest is more commonly associated with injury to the infrapatellar branch of the saphenous nerve and temporary knee flexion/internal rotation weakness.

Question 17

A 65-year-old woman sustains a 3-part proximal humerus fracture involving the surgical neck and greater tuberosity. The greater tuberosity fragment is severely displaced superiorly and posteriorly. What muscle forces are primarily responsible for the displacement of this specific fragment?





Explanation

The greater tuberosity serves as the insertion site for the supraspinatus, infraspinatus, and teres minor. A fracture fragment of the greater tuberosity is classically pulled superiorly by the supraspinatus and posteriorly by the infraspinatus and teres minor. The lesser tuberosity is pulled medially by the subscapularis. The humeral shaft is pulled anteromedially by the pectoralis major.

Question 18

A 40-year-old female undergoes an open carpal tunnel release. Postoperatively, her nocturnal paresthesias resolve, but she reports an inability to oppose her thumb to her little finger. Which structure was most likely iatrogenically injured during the procedure?





Explanation

The recurrent motor branch of the median nerve supplies the thenar intrinsic muscles (opponens pollicis, abductor pollicis brevis, and the superficial head of the flexor pollicis brevis), which are responsible for thumb opposition. Its iatrogenic injury is a classic and devastating complication if the dissection strays too far radially during a carpal tunnel release.

Question 19

Evaluating a post-reduction radiograph for a distal radius fracture, the surgeon measures the radial inclination to determine if criteria for acceptable alignment are met. What is the normal anatomic range for radial inclination on a PA radiograph of the wrist?





Explanation

Normal radiographic parameters of the distal radius are crucial for evaluating fracture reduction. They include: Radial inclination of 21-25 degrees (average 22 degrees), Radial height of 10-13 mm (average 11 mm), and Volar tilt of 10-12 degrees (average 11 degrees). Loss of these parameters alters load transmission across the radiocarpal and distal radioulnar joints.

Question 20

During a complex primary total knee arthroplasty (TKA), the surgeon inadvertently resects an excessive amount of the distal femur and compensates by using a thicker polyethylene insert, thereby elevating the joint line. What is the primary biomechanical consequence of elevating the joint line in TKA?





Explanation

Elevating the joint line in TKA leads to relative (pseudo) patella baja. This alters patellofemoral kinematics, leading to increased patellofemoral contact forces, anterior knee pain, and restricted range of motion (impingement of the patella against the tibial insert). It also commonly leads to mid-flexion instability due to alterations in the collateral ligament isometry.

Question 21

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The parents report that the child has stopped actively kicking the knee on the affected side. On examination, there is decreased active knee extension, but the patellar reflex is absent. Which of the following is the most likely cause of this complication?





Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive hip flexion causing compression of the femoral nerve against the inguinal ligament. It presents with decreased active knee extension. Treatment involves loosening the anterior straps or temporarily discontinuing the harness until nerve function recovers.

Question 22

During a posterior-stabilized total knee arthroplasty, the trial components are placed. The surgeon notes that the knee is tight in flexion, causing lift-off, but symmetric and well-balanced in extension. Which of the following is the most appropriate next step to balance the knee?





Explanation

A knee that is tight in flexion and balanced in extension indicates an isolated tight flexion gap. Appropriate interventions include downsizing the femoral component (with an anterior referencing system) to decrease the posterior condylar offset, translating the femoral component anteriorly, or increasing the posterior slope of the tibial cut.

Question 23

A 28-year-old male sustains a vertically oriented, highly displaced femoral neck fracture (Pauwels type III). What is the preferred fixation strategy to maximize biomechanical stability and minimize the risk of varus collapse?





Explanation

Pauwels type III fractures have a high vertical angle, subjecting the fracture to high shear forces. Biomechanical studies have shown that a fixed-angle device, such as a sliding hip screw (often supplemented with a derotational screw), provides superior resistance to varus collapse and shear compared to multiple parallel cancellous screws.

Question 24

A 14-year-old boy presents with pain and swelling in his mid-thigh. Radiographs show a diaphyseal permeative lesion with an 'onion skin' periosteal reaction. Biopsy reveals small round blue cells. Which chromosomal translocation is most characteristically associated with this tumor?





Explanation

The clinical and radiographic presentation describes Ewing's sarcoma. The pathognomonic translocation is t(11;22)(q24;q12), which fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11. t(X;18) is associated with synovial sarcoma; t(12;16) with myxoid liposarcoma; and t(2;13) with alveolar rhabdomyosarcoma.

Question 25

A 30-year-old carpenter sustains a laceration over the volar aspect of the proximal phalanx of the index finger, dividing both the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons. This injury corresponds to which flexor tendon zone?





Explanation

Zone II extends from the proximal edge of the A1 pulley to the insertion of the FDS on the middle phalanx. It contains both FDS and FDP tendons tightly enclosed within the fibro-osseous flexor sheath. Due to the high risk of adhesions and traditionally poor surgical outcomes, Bunnell historically termed this area 'no man's land'.

Question 26

A 65-year-old male complains of deteriorating handwriting and clumsiness in his hands. Neurological examination reveals a positive Hoffman's sign and the inability to rapidly adduct and abduct his ulnar digits, causing the small finger to rest in an abducted position. This specific spontaneous abduction of the small finger is known as:





Explanation

The 'finger escape sign' is a clinical finding in cervical spondylotic myelopathy (part of the 'myelopathy hand'). The patient is unable to hold the ulnar digits adducted and extended, causing them to drift into abduction and flexion. While Wartenberg's sign also involves abduction of the small finger, it is classically due to ulnar nerve palsy (loss of third palmar interosseous muscle with unopposed EDQ).

Question 27

In posterior cruciate ligament (PCL) reconstruction, the tibial inlay technique is often advocated over the transtibial tunnel technique. What is the primary biomechanical advantage of the tibial inlay technique?





Explanation

The tibial inlay technique secures the graft directly to the posterior facet of the tibia. This avoids the sharp angle (the 'killer turn') that the graft must negotiate when exiting a transtibial tunnel to reach the femoral attachment. This turn has been associated with graft attenuation, abrasion, and failure in traditional transtibial PCL reconstructions.

Question 28

A 55-year-old diabetic patient presents with a swollen, erythematous, right foot. Radiographs reveal extensive periarticular fragmentation, bony debris, and subluxation at the tarsometatarsal joints. According to the Eichenholtz classification of Charcot arthropathy, this represents:





Explanation

Eichenholtz Stage I (Developmental/Fragmentation) is characterized clinically by a red, hot, swollen foot, and radiographically by bony fragmentation, debris formation, subluxation, and dislocation. Stage II (Coalescence) involves absorption of fine debris and early fusion. Stage III (Reconstruction) shows rounding of bone ends and decreased sclerosis.

Question 29

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is FDA-approved for which of the following specific orthopedic applications?





Explanation

rhBMP-2 (Infuse) is FDA-approved for single-level Anterior Lumbar Interbody Fusion (ALIF) from L4-S1 within an LT-CAGE, as well as for acute open tibial shaft fractures stabilized with an IM nail within 14 days of injury. It is not approved for closed tibial fractures, pediatric use, or general posterolateral fusion without a specific off-label justification.

Question 30

In the emergency management of a hemodynamically unstable patient with an open-book pelvic ring injury (APC-II or III), a circumferential pelvic sheet or binder must be applied. For optimal biomechanical reduction of the symphysis, the binder should be centered precisely over which anatomical landmark?





Explanation

Pelvic binders must be centered over the greater trochanters to effectively close the pelvic ring and reduce the pubic symphysis. Placing the binder too high (over the iliac crests) can paradoxically widen the true pelvis by pushing the iliac wings inward at the top, acting as a fulcrum.

Question 31

Prophylactic pinning of the contralateral hip is most strongly indicated and routinely recommended for which of the following patients presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE)?





Explanation

Prophylactic pinning of the contralateral hip is indicated in patients at high risk for a sequential slip. Endocrine or metabolic disorders (such as renal osteodystrophy, hypothyroidism, or panhypopituitarism) carry a very high risk of bilateral involvement. Open triradiate cartilage (indicating young age) is another relative indication.

Question 32

In total hip arthroplasty, which of the following best describes the wear characteristics of ceramic-on-ceramic bearing surfaces compared to traditional metal-on-polyethylene bearings?





Explanation

Ceramic-on-ceramic bearings exhibit the lowest volumetric wear of all bearing combinations. The wear particles generated are extremely small (in the nanometer range) and provoke a much lower biological macrophage response compared to polyethylene particles, significantly reducing the risk of osteolysis. A notable disadvantage is the risk of squeaking and ceramic fracture.

Question 33

Denosumab is highly effective in the treatment of unresectable or recurrent Giant Cell Tumor of bone (GCT). What is its precise mechanism of action?





Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to RANK Ligand (RANKL), which is overexpressed by the mononuclear neoplastic stromal cells of GCT. By binding RANKL, denosumab prevents it from activating the RANK receptor on the reactive osteoclast-like giant cells, thereby halting bone resorption and tumor progression.

Question 34

The recurrent motor branch of the median nerve innervates the thenar muscles. According to anatomical studies, this branch most commonly arises from the median nerve at which location relative to the transverse carpal ligament (TCL)?





Explanation

The most common branching pattern of the recurrent motor branch of the median nerve is extraligamentous (approx 50-90% depending on the study), branching distal to the TCL and recurring back to innervate the thenar musculature. Subligamentous and transligamentous variations occur and are critical to recognize during carpal tunnel release to avoid iatrogenic injury.

Question 35

Which of the following clinical features most reliably differentiates neurogenic claudication from vascular claudication in an elderly patient with leg pain?





Explanation

The 'shopping cart sign' indicates relief of claudication symptoms with lumbar flexion, which is a hallmark of neurogenic claudication from lumbar spinal stenosis. Lumbar flexion increases the cross-sectional area of the spinal canal. Vascular claudication is worsened by walking uphill (increased metabolic demand) and typically occurs at a predictable, fixed distance.

Question 36

In a severe midfoot injury, radiographs reveal a 'Fleck sign' in the first intermetatarsal space, pathognomonic for a Lisfranc ligament avulsion. The Lisfranc ligament structurally connects which two bones?





Explanation

The Lisfranc ligament is a strong interosseous ligament that runs obliquely from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the primary stabilizer of the second tarsometatarsal joint; there is no direct ligamentous connection between the first and second metatarsal bases.

Question 37

Biomechanical studies have demonstrated that an un-repaired complete posterior root tear of the medial meniscus results in which of the following alterations in knee mechanics?





Explanation

Complete radial tears of the meniscus at its posterior root cause a loss of hoop stresses, leading to medial extrusion of the meniscus during axial loading. Biomechanically, this failure mechanism results in articular contact pressures equivalent to a knee that has undergone a total medial meniscectomy, accelerating the onset of osteoarthritis.

Question 38

In normal articular cartilage, the collagen fibrils in the superficial zone (lamina splendens) are oriented in which direction relative to the joint surface?





Explanation

In the superficial zone of articular cartilage, collagen fibers (predominantly Type II) are arranged parallel to the articular surface. This orientation provides maximum tensile strength to resist shear forces within the joint. In the deep zone, fibers are perpendicular to resist compressive forces, and in the middle zone, they are oblique/random.

Question 39

A 60-year-old woman returns to the clinic 6 months after open reduction and internal fixation of a distal radius fracture with a volar locking plate. She suddenly lost the ability to actively flex the interphalangeal joint of her thumb. Which of the following is the most likely cause?





Explanation

Placement of a volar locking plate distal to the watershed line of the radius increases the risk of the flexor tendons rubbing against the prominent distal edge of the plate. The Flexor Pollicis Longus (FPL) tendon is most intimately associated with this region and is highly susceptible to attritional rupture, a classic late complication of volar plating.

Question 40

According to the Ponseti method for the conservative treatment of congenital talipes equinovarus (clubfoot), what is the correct sequence of deformity correction during serial casting?





Explanation

The Ponseti method sequentially corrects the components of the clubfoot deformity in the specific order represented by the acronym CAVE: Cavus (corrected by elevating the first ray to supinate the forefoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy for full correction).

Question 41

A 45-year-old man presents with chronic wrist pain. Radiographs reveal a scaphoid non-union with advanced collapse (SNAC). There is arthritic involvement of the radioscaphoid and capitolunate joints. Which of the following joints is classically SPARED in this condition, making the patient a suitable candidate for a four-corner fusion?





Explanation

In both SNAC (scaphoid nonunion advanced collapse) and SLAC (scapholunate advanced collapse) wrists, the radiolunate joint is classically spared from osteoarthritis. This is due to the concentric, spherical articulation of the lunate fossa and the lunate, which maintains congruence and avoids abnormal shear forces even when carpal kinematics are altered. This sparing allows for motion-preserving salvage procedures such as proximal row carpectomy (if the capitate head is intact) or four-corner fusion.

Question 42

A 12-year-old boy is diagnosed with a severe left slipped capital femoral epiphysis (SCFE) and undergoes in-situ pinning. Which of the following factors is the strongest absolute indication for performing a prophylactic pinning of the contralateral asymptomatic hip?





Explanation

Patients with an underlying endocrinopathy (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) have an extremely high risk of bilateral SCFE (up to 100% in some series) and often present at an atypical age. Prophylactic pinning of the contralateral hip is strongly indicated in these patients. A low Modified Oxford Bone Age score (<16) also predicts higher risk, while a score of 18 implies skeletal maturity with minimal risk.

Question 43

A 35-year-old trauma patient has a pelvic ring injury classified as a Day Type 1 crescent fracture (Young-Burgess LC-2). Which of the following best describes the optimal surgical approach and fixation for this specific fracture pattern?





Explanation

The Day classification describes lateral compression type II (crescent) fractures. Type 1 represents a large crescent fragment where the fracture exits anterior to the SI joint, leaving the SI joint predominantly intact. The optimal fixation for this large iliac wing fragment is an anterior approach with open reduction and internal fixation (ORIF) using plates and screws. Type 2 exits into the SI joint, and Type 3 is a small crescent exiting posterior to the joint (best treated with posterior iliosacral screws).

Question 44

In orthopaedic biomechanics, which of the following terms describes the time-dependent increase in strain (deformation) of a viscoelastic material when subjected to a constant stress (load)?





Explanation

Creep is the progressive deformation (strain) of a viscoelastic material over time when it is subjected to a constant force (stress). This is a foundational concept in the serial casting of deformities (e.g., clubfoot). Stress relaxation, conversely, is the decrease in stress over time when a material is held at a constant strain.

Question 45

A 28-year-old woman undergoes a biopsy of a slow-growing, deep soft-tissue mass in her thigh. Cytogenetics reveal a t(X;18)(p11;q11) chromosomal translocation. Which of the following is the most likely diagnosis?





Explanation

Synovial sarcoma is classically associated with the t(X;18)(p11;q11) translocation, which results in the SYT-SSX fusion gene. This molecular marker is highly specific and sensitive for synovial sarcoma, a high-grade soft tissue sarcoma commonly found near (but rarely within) large joints of young adults.

Question 46

According to the Resnick criteria for diagnosing Diffuse Idiopathic Skeletal Hyperostosis (DISH), all of the following are required EXCEPT:





Explanation

DISH is diagnosed radiographically using the Resnick criteria: 1) Flowing ossification over at least 4 contiguous vertebral bodies, 2) Preservation of disc space height without signs of degenerative disc disease, and 3) Absence of apophyseal joint ankylosis and sacroiliac joint erosion/sclerosis. Unlike Ankylosing Spondylitis, DISH is not strongly associated with the HLA-B27 antigen.

Question 47

A 65-year-old woman complains of an audible 'clunk' and catching sensation when extending her knee from a flexed position, 18 months following a posterior-stabilized total knee arthroplasty. At what approximate degree of knee flexion does this phenomenon most commonly occur during active extension?





Explanation

Patellar clunk syndrome is a known complication of posterior-stabilized (PS) total knee arthroplasties. It occurs due to the formation of a fibrous nodule at the superior pole of the patella. As the knee extends from a deep flexed position, the nodule catches within the intercondylar box of the femoral component and suddenly pops out ('clunks') typically between 30 to 45 degrees of flexion.

Question 48

A 22-year-old football player sustains a multi-ligament knee injury. A dial test is performed. There is 15 degrees of increased external rotation at 30 degrees of knee flexion compared to the contralateral side, but symmetric external rotation at 90 degrees of knee flexion. This physical examination finding is indicative of an isolated injury to which of the following?





Explanation

The Dial test evaluates external rotation asymmetry. An increase of >10 degrees of external rotation at 30 degrees of flexion, but not at 90 degrees, indicates an isolated injury to the posterolateral corner (PLC). If the asymmetry is present at both 30 and 90 degrees, it suggests a combined injury to the PLC and the posterior cruciate ligament (PCL).

Question 49

A 14-year-old boy with Charcot-Marie-Tooth disease presents with bilateral pes cavovarus deformities. A Coleman block test is performed and completely corrects the hindfoot varus to neutral. What does this physical examination finding dictate regarding the surgical management?





Explanation

The Coleman block test evaluates hindfoot flexibility in cavovarus feet. By placing the lateral border of the foot on a block and allowing the plantarflexed first ray to drop, the test negates the forefoot's effect on hindfoot position. If the hindfoot varus corrects, the deformity is primarily forefoot-driven (a plantarflexed 1st ray) and the hindfoot is flexible. The primary bony treatment should therefore target the forefoot (e.g., 1st metatarsal dorsiflexion osteotomy).

Question 50

A 30-year-old man sustains a Pauwels Type III (vertical) femoral neck fracture. Biomechanically, which of the following forces primarily contributes to the high rate of failure and non-union in this fracture pattern?





Explanation

Pauwels Type III femoral neck fractures have an orientation >50 degrees from the horizontal. Biomechanically, this highly vertical orientation converts physiological weight-bearing loads into large shear forces across the fracture site. Shear forces disrupt the delicate healing process, leading to high rates of non-union and fixation failure, unlike compressive forces which generally promote bone healing.

Question 51

A patient presents with an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger, failing to make an 'OK' sign. Sensation over the hand is completely normal. Which of the following muscles is most likely ALSO affected by this nerve palsy?





Explanation

The clinical presentation is classic for Anterior Interosseous Nerve (AIN) syndrome. The AIN is a purely motor branch of the median nerve that innervates the flexor pollicis longus (FPL), the radial half of the flexor digitorum profundus (FDP to index and middle fingers), and the pronator quadratus. Sensation is spared. Loss of FPL and index FDP prevents the 'OK' sign.

Question 52

A 2-year-old child presents with bilateral genu varum. Radiographs show medial beaking of the proximal tibial metaphysis. Which of the following radiographic measurements is the most reliable predictor that the deformity will progress (infantile Blount's disease) rather than resolve (physiologic bowing)?





Explanation

The metaphyseal-diaphyseal angle (Drennan angle) is critical in distinguishing physiologic bowing from infantile Blount's disease. An angle > 16 degrees has a high predictive value (up to 95%) that the varus deformity will progress (Blount's disease), warranting intervention such as bracing. Angles < 10 degrees typically indicate physiologic bowing, which resolves spontaneously.

Question 53

A 40-year-old man sustains a traumatic spondylolisthesis of C2 (Hangman's fracture) following a motor vehicle accident. Radiographs reveal severe angulation (>15 degrees) with minimal translation (Levine-Edwards Type IIA). What is the primary mechanism of injury for this specific fracture subtype, and what is the absolute contraindication in its management?





Explanation

A Levine-Edwards Type IIA Hangman's fracture is characterized by severe angulation and minimal translation, occurring via a flexion-distraction mechanism. Because the posterior longitudinal ligament and disc space are severely disrupted, applying cervical traction will over-distract the injury and is strictly contraindicated. Treatment typically involves a halo vest applied with gentle compression and slight extension.

Question 54

A 65-year-old man is diagnosed with an acute staphylococcal periprosthetic joint infection (PJI) of his total hip arthroplasty. He is treated with irrigation, debridement, and modular exchange. His post-operative antibiotic regimen includes Rifampin. What is the primary reason for including Rifampin, and what is its mechanism of action?





Explanation

Rifampin is utilized in the treatment of staphylococcal periprosthetic joint infections due to its exceptional ability to penetrate established bacterial biofilms and eradicate sessile organisms. Its mechanism of action is the inhibition of DNA-dependent RNA polymerase, which disrupts bacterial RNA transcription.

Question 55

Ceramic-on-ceramic (CoC) bearing surfaces in total hip arthroplasty are known for extremely low wear rates. Which of the following lubrication regimes primarily governs the tribology of a well-functioning CoC articulation?





Explanation

Ceramic-on-ceramic (CoC) bearings typically operate under a fluid-film lubrication regime. Because ceramic is highly hydrophilic and has excellent surface smoothness and hardness, joint fluid creates a continuous film that separates the articulating surfaces, resulting in exceptionally low friction and minimal wear under optimal conditions.

Question 56

A 25-year-old overhead athlete undergoes shoulder arthroscopy and is diagnosed with a Type IV SLAP (Superior Labrum Anterior Posterior) lesion. The tear extends into the long head of the biceps tendon, involving 60% of the tendon substance. What is the most appropriate surgical management?





Explanation

A Type IV SLAP tear is a bucket-handle tear of the superior labrum that extends into the biceps tendon. When greater than 50% of the biceps tendon is involved, the recommended treatment is biceps tenodesis (or tenotomy, depending on age and activity level) along with debridement of the labral tear. Repair of the biceps tendon itself is generally not recommended due to poor healing and continued pain.

Question 57

A 42-year-old male sustains a high-energy Schatzker Type IV tibial plateau fracture. Imaging demonstrates a coronally oriented posteromedial fracture fragment. What is the optimal surgical approach and internal fixation strategy for this specific fragment?





Explanation

Schatzker Type IV (medial plateau) fractures often result from high-energy trauma. The classic variant involves a coronally oriented posteromedial fragment. To effectively resist the sheer forces during knee flexion, this fragment must be buttressed from behind. The optimal technique is a posteromedial approach with the application of an anti-glide or buttress plate to the posterior aspect of the medial tibial condyle.

Question 58

Giant Cell Tumor (GCT) of bone is a locally aggressive benign tumor. Which of the following accurately describes the cellular pathophysiology and the targeted mechanism of the biological agent Denosumab in treating this condition?





Explanation

In Giant Cell Tumor (GCT) of bone, the actual neoplastic cells are the mononuclear spindle-like stromal cells. These cells express high levels of RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand). The multinucleated giant cells are reactive (osteoclast-like) and express RANK. Denosumab is a human monoclonal antibody that binds and inhibits RANKL, effectively halting the recruitment and activation of the destructive giant cells.

Question 59

An infant is born with a unilateral radial clubhand (radial longitudinal deficiency). The consulting geneticist suspects a systemic syndrome. Physical examination reveals an absent thumb on the affected side. Which of the following syndromes is strictly characterized by the PRESENCE of a thumb despite radial deficiency, making it clinically distinguishable from the others?





Explanation

Thrombocytopenia-absent radius (TAR) syndrome is unique among the conditions associated with radial longitudinal deficiency because the thumb is classically PRESENT, whereas in Holt-Oram syndrome, Fanconi anemia, and VACTERL association, the thumb is typically hypoplastic or absent.

Question 60

A 35-year-old recreational basketball player undergoes a percutaneous repair of an acute Achilles tendon rupture. Post-operatively, he reports numbness along the lateral aspect of his foot. Injury to which nerve most likely occurred, and at what anatomical location is this nerve most vulnerable during percutaneous repair?





Explanation

The sural nerve is at highest risk during percutaneous or minimally invasive Achilles tendon repair. It courses along the posterolateral aspect of the leg and crosses the lateral border of the Achilles tendon from medial to lateral at approximately 9.8 cm (roughly 10 cm) proximal to its insertion on the calcaneus. Sutures placed blindly in the proximal stump run a significant risk of entrapping this nerve.

Question 61

A 45-year-old male presents with chronic, progressive wrist pain. Radiographs demonstrate a scaphoid nonunion with advanced arthritic changes at the radioscaphoid and capitolunate joints. The radiolunate joint is spared. Which of the following is the most appropriate surgical treatment?





Explanation

The patient has Scaphoid Nonunion Advanced Collapse (SNAC) Stage III, which involves arthritis of the radioscaphoid and capitolunate joints with a preserved radiolunate joint. Proximal row carpectomy (PRC) is contraindicated because the capitate head is arthritic (it would articulate with the lunate fossa). Four-corner fusion (capitate, hamate, lunate, triquetrum) with scaphoid excision is the standard bone-preserving salvage procedure for SNAC III.

Question 62

During a primary total knee arthroplasty, the surgeon checks the trial components. The knee demonstrates a symmetric and stable extension gap, but is excessively tight in flexion. Which of the following is the most appropriate step to balance the knee?





Explanation

A knee that is tight in flexion but well-balanced in extension requires isolated enlargement of the flexion gap. Downsizing the femoral component (with an anterior referencing system) will resect more posterior femoral condyle, thereby increasing the flexion gap without altering the extension gap. Recutting the tibia would inappropriately increase the extension gap as well.

Question 63

Which of the following factors is the most significant clinical predictor for the development of avascular necrosis (AVN) following a slipped capital femoral epiphysis (SCFE)?





Explanation

The stability of the SCFE, defined by Loder as the ability or inability to bear weight (even with crutches), is the most important prognostic factor for AVN. Unstable SCFE has an AVN rate approaching 20-50%, whereas stable SCFE has an AVN rate of nearly 0%.

Question 64

A 65-year-old female undergoes open reduction and internal fixation of a distal radius fracture using a volar locking plate. Six months postoperatively, she suddenly loses the ability to actively extend her thumb interphalangeal joint. What is the most likely cause?





Explanation

Loss of active thumb IP extension is the hallmark of Extensor Pollicis Longus (EPL) rupture. When a volar locking plate is used, screws that are too long and penetrate the dorsal cortex (especially near Lister's tubercle) can cause attrition and secondary rupture of the EPL tendon.

Question 65

A 62-year-old male presents with severe thigh pain. Imaging reveals a large, destructive lytic lesion in the proximal femur with an impending fracture (Mirels score of 10). Biopsy confirms multiple myeloma. He undergoes prophylactic intramedullary nailing. What is the most critical next step in the local management of this extremity?





Explanation

Plasmacytoma and multiple myeloma lesions are highly radiosensitive. Following prophylactic stabilization of an impending or actual pathologic fracture from myeloma, post-operative radiation therapy is indicated to control local disease progression, alleviate pain, and prevent eventual hardware failure.

Question 66

When evaluating a patient with suspected cervical spondylotic myelopathy, which of the following physical examination findings represents an upper motor neuron (UMN) sign?





Explanation

Cervical myelopathy presents with upper motor neuron signs below the level of the lesion and potentially lower motor neuron signs at the level of the lesion. A positive Hoffmann sign, hyperreflexia, inverted radial reflex, clonus, and Babinski sign are UMN signs. Atrophy, absent reflexes, and fasciculations are lower motor neuron signs.

Question 67

A 22-year-old professional athlete undergoes anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BPTB) autograft. What is the most common postoperative complication directly associated with this specific donor site?





Explanation

Anterior knee pain, especially pain with kneeling, is the most common complication and chief complaint following ACL reconstruction with a BPTB autograft, occurring in up to 10-20% of patients. Patellar fractures and tendon ruptures are severe but rare complications.

Question 68

In a purely ligamentous Lisfranc injury, what is the classic primary mechanism of injury?





Explanation

The classic indirect mechanism for a Lisfranc (tarsometatarsal) injury is an axial load applied to a plantarflexed foot (e.g., a football player falling forward onto a planted, plantarflexed foot). This leads to hyperplantarflexion and subsequent dorsal displacement of the metatarsal bases.

Question 69

Which of the following mechanical and biological conditions is absolutely required to promote primary (direct) bone healing without callus formation?





Explanation

Primary (direct) bone healing occurs via cutting cones and requires absolute stability (no motion) and direct contact between fracture fragments, typically achieved through interfragmentary compression. Secondary bone healing involves callus formation (endochondral ossification) and is promoted by relative stability and controlled micromotion.

Question 70

A 4-month-old female infant is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip (DDH). After 3-4 weeks of verified, continuous proper harness wear, ultrasound confirms the hip remains completely dislocated. What is the most appropriate next step in management?





Explanation

If a hip remains dislocated after 3 to 4 weeks of proper Pavlik harness treatment, the harness must be abandoned. Continuing it increases the risk of 'Pavlik harness disease' (posterior acetabular damage) and AVN. The next standard step is closed reduction and spica casting, possibly preceded by rigid orthosis trial or traction, but closed reduction is the definitive next step.

Question 71

A 25-year-old male sustains a vertically oriented, displaced intracapsular femoral neck fracture (Pauwels type III). What is the preferred method of internal fixation to best counteract the high vertical shear forces inherent to this fracture pattern?





Explanation

Pauwels type III fractures are highly vertical and subject to significant shear forces, predisposing to nonunion and varus collapse. Biomechanical studies demonstrate that a fixed-angle device, such as a sliding hip screw (dynamic hip screw) supplemented with a derotation screw, provides superior resistance to vertical shear compared to multiple cancellous screws.

Question 72

A 68-year-old female presents with progressive groin pain 10 years after a primary metal-on-polyethylene total hip arthroplasty. Radiographs reveal eccentric wear of the polyethylene liner and a large proximal femoral osteolytic lesion. What is the primary biologic mediator directly activated by wear debris to cause this osteolysis?





Explanation

Aseptic loosening and osteolysis are driven by a macrophage-mediated foreign body response to particulate wear debris (e.g., polyethylene particles). Macrophages phagocytose the debris and release pro-inflammatory cytokines, most notably TNF-a, IL-1, and IL-6, which stimulate osteoclast differentiation and bone resorption.

Question 73

In Dupuytren's disease, the spiral cord can cause proximal interphalangeal (PIP) joint contracture and central displacement of the neurovascular bundle, putting it at risk during surgery. Which of the following normal fascial structures does NOT contribute to the formation of the spiral cord?





Explanation

The spiral cord in Dupuytren's contracture is composed of the pretendinous band, the spiral band, the lateral digital sheet, and Grayson's ligament. Cleland's ligament is dorsal to the neurovascular bundle and is characteristically spared (not involved) in Dupuytren's disease.

Question 74

A 35-year-old female falls from a height and sustains an L1 burst fracture. She is neurologically intact. MRI demonstrates an intact posterior ligamentous complex (PLC). Radiographs show 25% loss of anterior vertebral body height and CT shows 30% canal compromise. Based on the Thoracolumbar Injury Classification and Severity (TLICS) score, what is the score and the recommended management?





Explanation

The TLICS score is calculated as follows: Morphology (Burst = 2 points), Neurologic status (Intact = 0 points), PLC status (Intact = 0 points). The total score is 2. A score of 3 or less is an indication for non-operative management (e.g., orthosis/bracing). A score of 4 is indeterminate, and 5 or more indicates surgery.

Question 75

A 19-year-old collision athlete is undergoing an open Latarjet procedure for recurrent anterior shoulder instability associated with 25% anterior glenoid bone loss. During the approach, which muscle is typically split to allow passage of the coracoid bone block to the anterior glenoid neck?





Explanation

The Latarjet procedure involves transferring the coracoid process with its attached conjoined tendon to the anterior glenoid. To expose the anterior glenoid and pass the graft, the subscapularis muscle is classically split longitudinally (in line with its fibers), creating a 'sling' effect with the conjoined tendon.

Question 76

According to the Ponseti method for the conservative management of idiopathic clubfoot, what is the correct sequence of deformity correction during serial casting?





Explanation

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

Question 77

In a hemodynamically unstable patient with a high-energy Anteroposterior Compression (APC) Type III pelvic ring injury, what is the most common anatomical source of the life-threatening retroperitoneal hemorrhage?





Explanation

While arterial bleeding (e.g., from branches of the internal iliac like the superior gluteal or internal pudendal arteries) can cause rapid demise, 80-90% of pelvic hemorrhage in pelvic ring disruptions originates from venous sources (presacral plexus) and the exposed cancellous bone surfaces at fracture sites.

Question 78

A 30-year-old female presents with a biologically active Giant Cell Tumor (GCT) of the distal femur. She is scheduled for curettage but is treated preoperatively with Denosumab to consolidate the tumor margins. What is the mechanism of action of this medication?





Explanation

Denosumab is a fully human monoclonal antibody that binds to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By inhibiting RANKL, it prevents the activation of the RANK receptor on osteoclast-like giant cells, thereby profoundly reducing osteolysis and promoting ossification of the tumor matrix.

Question 79

A 40-year-old recreational athlete sustains an acute Achilles tendon rupture. If he chooses non-operative management utilizing an early functional rehabilitation protocol instead of open surgical repair, what outcome is most supported by recent high-level clinical trials?





Explanation

Recent level-1 evidence (randomized controlled trials) indicates that when early functional rehabilitation (early weight-bearing and ROM in a boot) is utilized, non-operative management yields similar functional outcomes, strength, and re-rupture rates compared to surgical repair, while avoiding surgical wound complications.

Question 80

Which type of collagen is the predominant structural protein found in the extracellular matrix of normal mature articular (hyaline) cartilage?





Explanation

Type II collagen makes up 90-95% of the collagen in normal articular (hyaline) cartilage, providing tensile strength. Type I is found in bone, tendon, and fibrocartilage (such as the meniscus or scar cartilage). Type X is specific to the hypertrophic zone of the growth plate during endochondral ossification.

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