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Arab Orthopaedic Board MCQs - Part 18

27 Apr 2026 52 min read 75 Views
Arab Ortho Board MCQs - Part 17

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Your ultimate guide to Arab Orthopaedic Board MCQs - Part 18 starts here. Practice Arab Orthopaedic Board MCQs Part 18. Review orthopedic surgery questions 851 to 900 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 18

Comprehensive 100-Question Exam


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Question 1

A 10-year-old boy presents with an established idiopathic right clubfoot that is being treated with the Ponseti method. According to the Ponseti principles of serial casting, which of the following describes the correct initial maneuver to correct the cavus deformity?





Explanation

In the Ponseti method, the first step in correcting a clubfoot deformity is addressing the cavus. The cavus is primarily caused by plantarflexion of the first ray relative to the hindfoot. To correct this, the forefoot must be supinated (to match the hindfoot supination) by elevating the first metatarsal. Once the cavus is corrected and the forefoot is aligned with the hindfoot, the entire foot can be gradually abducted around the talus to correct the adductus and varus.

Question 2

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction during fracture healing. Which of the following intracellular signaling pathways is primarily activated by BMP receptor binding?





Explanation

Bone morphogenetic proteins (BMPs) are members of the TGF-beta superfamily. When a BMP binds to its cell surface serine-threonine kinase receptors, it induces the phosphorylation of receptor-regulated SMADs, specifically SMAD 1, 5, and 8. These phosphorylated SMADs form a complex with the common-mediator SMAD 4, which then translocates into the nucleus to regulate the transcription of osteogenic genes like Runx2.

Question 3

A 65-year-old female presents with groin pain and swelling three years after undergoing a primary total hip arthroplasty utilizing a metal head on a highly cross-linked polyethylene liner with a titanium femoral stem. Metal ion analysis and MRI are suggestive of trunnionosis (mechanically assisted crevice corrosion). Which of the following serum metal ion profiles is most characteristic of this specific complication?





Explanation

Trunnionosis, or mechanically assisted crevice corrosion at the head-neck junction of a total hip arthroplasty, typically involves a cobalt-chromium (CoCr) head on a titanium (Ti) alloy stem. Corrosion at this modular junction leads to the preferential release of cobalt ions. Consequently, patients with trunnionosis characteristically present with an elevated serum cobalt-to-chromium ratio (Co > Cr), distinguishing it from wear at a metal-on-metal articular surface where Co and Cr are typically elevated more equally.

Question 4

A 68-year-old male is evaluated for isolated anterior knee pain with a palpable 'catching' sensation when extending his knee from a flexed position. He underwent a posterior-stabilized total knee arthroplasty 18 months ago. Examination reveals a painful snap at approximately 30 to 40 degrees of knee flexion during active extension. What is the most definitive and appropriate treatment for this condition?





Explanation

The patient's presentation is classic for 'patellar clunk syndrome,' a complication most commonly associated with posterior-stabilized total knee arthroplasty designs. It is caused by the formation of a fibrous nodule at the superior pole of the patella or distal quadriceps tendon. During knee extension, this nodule catches in the intercondylar box of the femoral component, producing a painful clunk. The definitive and highly successful treatment is arthroscopic debridement/excision of the fibrous nodule.

Question 5

In Kienböck's disease, the Lichtman classification is used to guide surgical decision-making. Which of the following radiographic findings definitively differentiates Stage IIIB from Stage IIIA?





Explanation

The Lichtman classification for Kienböck's disease stages the progression of lunate avascular necrosis. Stage IIIA exhibits lunate collapse but normal carpal alignment. Stage IIIB is distinguished by lunate collapse accompanied by fixed carpal instability, characteristically manifesting as fixed scaphoid rotatory subluxation (scaphoid ring sign, radioscaphoid angle > 60 degrees, or scapholunate angle > 60 degrees). Stage IV involves pancarpal arthritis.

Question 6

A 22-year-old elite baseball pitcher presents with posterior shoulder pain during the late cocking and early acceleration phases of throwing. MRI arthrogram reveals a partial articular-sided supraspinatus tendon tear and superior labral fraying. The pathophysiology of this internal impingement is characterized by pathologic abutment between which of the following structures?





Explanation

Internal impingement (posterosuperior impingement) typically affects overhead athletes. During the extreme abduction and external rotation of the late cocking phase of throwing, the articular-sided junction of the supraspinatus and infraspinatus tendons abuts against the posterosuperior glenoid rim and labrum. This repetitive contact leads to articular-sided 'kissing' lesions of the rotator cuff and posterosuperior labral fraying.

Question 7

A 28-year-old male presents with a deep, slow-growing soft tissue mass in his thigh near the knee joint. Biopsy reveals a biphasic tumor with both epithelial and spindle cell components. Molecular testing of the biopsy specimen is most likely to identify which of the following chromosomal translocations?





Explanation

The clinical and histological description is classic for a synovial sarcoma (a deep soft tissue mass near a joint in a young adult, with biphasic histology). Synovial sarcoma is uniquely characterized by the t(X;18)(p11;q11) chromosomal translocation, which results in the SYT-SSX fusion gene. The t(11;22) is seen in Ewing sarcoma, t(12;16) in myxoid liposarcoma, t(9;22) in extraskeletal myxoid chondrosarcoma, and t(2;13) in alveolar rhabdomyosarcoma.

Question 8

A 4-month-old infant is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. During a follow-up visit, the orthopedist notices an absence of active knee extension on the affected side. This complication is most directly related to which of the following harness fitting errors?





Explanation

Femoral nerve palsy is a known complication of the Pavlik harness and presents as an inability to actively extend the knee. It is caused by excessive flexion of the hip (typically > 120 degrees), which compresses the femoral nerve against the rim of the pelvis or the inguinal ligament. Excessive abduction is associated with avascular necrosis of the femoral head.

Question 9

A surgeon decides to exchange a solid 10 mm diameter intramedullary tibial nail for a solid 12 mm diameter intramedullary tibial nail. According to biomechanical principles of cylindrical structures, by approximately what factor will the bending rigidity of the nail increase?





Explanation

The bending rigidity (stiffness) of a solid cylinder is proportional to the area moment of inertia, which scales with the radius to the fourth power (r^4). Increasing the diameter from 10 mm to 12 mm increases the radius from 5 mm to 6 mm. The factor of increase is (6/5)^4 = 1.2^4 = 2.0736. Thus, the bending rigidity increases by approximately a factor of 2.07.

Question 10

A 55-year-old female presents with an inability to actively flex the interphalangeal joint of her thumb 8 months after undergoing volar plate fixation of a distal radius fracture. Radiographs show a healed fracture but the distal edge of the volar plate is positioned anterior to the watershed line. Which tendon is most likely ruptured due to attritional wear against the plate?





Explanation

Placement of a volar plate distal to the watershed line of the distal radius places the prominent hardware in direct contact with the flexor tendons. The Flexor Pollicis Longus (FPL) tendon runs intimately over this area and is at the highest risk for attritional rupture when the plate is positioned too distally or stands proud of the bone (Soong Grade 2).

Question 11

In a patient presenting with cervical spondylotic myelopathy (CSM), which of the following preoperative magnetic resonance imaging (MRI) findings is most strongly correlated with a poor postoperative clinical outcome?





Explanation

In the context of cervical spondylotic myelopathy, MRI signal changes provide prognostic information. While a faint T2-weighted hyperintensity may indicate reversible edema or gliosis and has a variable prognosis, a focal T1-weighted hypointensity indicates permanent cystic necrosis or myelomalacia of the spinal cord. Studies have consistently shown that T1 hypointensity is a strong independent predictor of poor neurologic recovery postoperatively.

Question 12

The primary stabilizing ligament of the tarsometatarsal articulation, commonly referred to as the Lisfranc ligament, connects which of the following specific osseous structures?





Explanation

The Lisfranc ligament is an intra-articular interosseous ligament that serves as the primary restraint to dorsal and lateral displacement of the second metatarsal base. Anatomically, it originates from the lateral surface of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal. It lacks a true dorsal component and is thickest on its plantar aspect.

Question 13

During the anterior intrapelvic (modified Stoppa) approach for acetabular fracture fixation, the surgeon must be mindful of the 'corona mortis'. This vascular anastomosis most commonly connects the obturator vessels with which of the following vascular systems?





Explanation

The 'corona mortis' (crown of death) is a highly variable but clinically significant vascular anastomosis located over the superior pubic ramus, typically 4 to 6 cm from the pubic symphysis. It represents an anastomotic connection between the external iliac vascular system (often the inferior epigastric artery/vein) and the obturator vascular system (which arises from the internal iliac system). Injury to it can cause catastrophic bleeding retracting into the pelvis.

Question 14

A 35-year-old male presents with chronic hip pain. Radiographs demonstrate a lytic lesion with intralesional calcifications located strictly in the epiphysis of the proximal femur. Biopsy reveals cells with abundant clear cytoplasm and central nuclei, arranged in a lobular pattern. Based on the clinical demographic and location, what is the most likely diagnosis?





Explanation

Clear cell chondrosarcoma is a rare, low-grade malignant bone tumor that characteristically arises in the epiphysis of long bones (most commonly the proximal femur or proximal humerus). It often clinically and radiographically mimics chondroblastoma. However, chondroblastoma typically occurs in patients with open physes or under the age of 20, whereas clear cell chondrosarcoma usually presents in adults aged 20 to 50 years. The histology featuring cells with clear cytoplasm confirms the diagnosis.

Question 15

A 9-year-old girl (Tanner stage I) sustains a complete anterior cruciate ligament (ACL) tear while playing soccer. Non-operative management fails due to recurrent instability. To minimize the risk of physeal arrest, which of the following surgical techniques is most appropriate?





Explanation

In a skeletally immature patient with significant remaining growth (Tanner stage 1 or 2, open physes), standard transphyseal ACL drilling carries a high risk of growth arrest or angular deformity. The recommended surgical approach for recurrent instability in this demographic is a completely physeal-sparing technique, such as the Micheli-Kocher method, which utilizes a strip of the iliotibial band routed extra-articularly and intra-articularly over the top of the lateral femoral condyle.

Question 16

The introduction of highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) has significantly reduced volumetric wear rates in total hip arthroplasty. However, the radiation cross-linking process introduces a clinically relevant trade-off by reducing which of the following material properties?





Explanation

Irradiation of UHMWPE creates free radicals that form cross-links, heavily increasing the material's resistance to adhesive and abrasive wear. However, this process alters the crystalline structure and polymer chain mobility, which results in a reduction of mechanical properties, specifically yield strength, ultimate tensile strength, and fatigue resistance. This makes it more susceptible to fracture, particularly in thin liners or high-stress applications.

Question 17

Historically, the arcuate branch of the anterior circumflex humeral artery was considered the primary blood supply to the humeral head. However, modern quantitative cadaveric studies have demonstrated that the predominant blood supply to the humeral head actually arises from which of the following vessels?





Explanation

A landmark quantitative study by Hettrich et al. (JBJS Am 2010) demonstrated that the posterior circumflex humeral artery (PCHA) provides the majority (approximately 64%) of the blood supply to the humeral head, specifically supplying the posterior, inferior, and medial aspects. The anterior circumflex humeral artery provides only about 36%. This shifted the traditional paradigm that the arcuate artery (from the ACHA) was the dominant supply.

Question 18

According to the Thoracolumbar Injury Classification and Severity Score (TLICS), a patient presents with an L1 burst fracture, intact neurology, and an MRI indicating a confirmed disruption of the posterior ligamentous complex (PLC). What is the patient's total TLICS score and the recommended management?





Explanation

The TLICS system scores three categories: Morphology, Neurologic Status, and PLC Integrity. A burst fracture = 2 points. Intact neurologic status = 0 points. Confirmed disruption of the PLC = 3 points. Total score = 2 + 0 + 3 = 5 points. A TLICS score of > 4 represents an indication for operative management. A score of < 4 indicates non-operative management, and a score of exactly 4 is indeterminate (surgeon preference).

Question 19

A 12-year-old boy is diagnosed with a unilateral slipped capital femoral epiphysis (SCFE) of the left hip. The orthopaedic surgeon recommends prophylactic in situ pinning of the contralateral right hip due to a high risk of subsequent slip. Which of the following underlying conditions most strongly warrants prophylactic contralateral pinning in SCFE?





Explanation

While idiopathic SCFE is common in obese adolescents, endocrinopathies are strong indications for prophylactic contralateral pinning due to the exceedingly high risk of bilateral involvement. Hypothyroidism, panhypopituitarism, and growth hormone deficiency are the most common endocrine disorders associated with atypical or early/late presentation of SCFE, and prophylactic pinning of the asymptomatic hip is strongly recommended in these patients.

Question 20

A 58-year-old male with poorly controlled diabetes mellitus presents with a swollen, erythematous, and warm left foot. Radiographs reveal marked osteopenia, periarticular fragmentation, and joint subluxation at the midfoot. According to the Eichenholtz classification for Charcot arthropathy, which stage does this represent and what is the standard of care?





Explanation

The patient's clinical and radiographic presentation is consistent with Stage 1 (Developmental/Fragmentation stage) of the Eichenholtz classification for Charcot arthropathy. Radiographically, this is characterized by osteopenia, bony fragmentation, joint subluxation/dislocation, and debris. Stage 2 is Coalescence (absorption of fine debris, early sclerosis). Stage 3 is Consolidation (remodeling, rounding of bone ends, solid fusion). The gold standard treatment for Stage 1 acute Charcot is offloading, most effectively achieved with a total contact cast (TCC).

Question 21

The primary blood supply to the femoral head in an adolescent with a slipped capital femoral epiphysis (SCFE) is derived from the:





Explanation

The lateral epiphyseal artery, a terminal branch of the medial circumflex femoral artery (MCFA), provides the predominant blood supply to the femoral head in older children and adolescents. Disruption of these retinacular vessels during a SCFE or its surgical treatment can lead to avascular necrosis.

Question 22

The 'Corona Mortis' is an important vascular anastomosis encountered during the ilioinguinal approach to the pelvis. It typically connects which two vascular systems?





Explanation

The Corona Mortis is a vascular anastomosis between the external iliac or inferior epigastric vessels and the obturator vessels. It crosses the superior pubic ramus and is highly susceptible to injury during pelvic approaches or screw placement, leading to severe hemorrhage.

Question 23

Trunnionosis, observed at the head-neck modular junction in total hip arthroplasty, is predominantly initiated by which of the following mechanisms?





Explanation

Trunnionosis is primarily an example of mechanically assisted crevice corrosion, initiated by fretting corrosion. Micromotion at the modular head-neck taper (fretting) mechanically breaks down the protective passive oxide layer of the metal, exposing raw metal to the body fluids and leading to accelerated localized crevice corrosion.

Question 24

When performing a primary repair of a flexor tendon laceration in Zone II, the ultimate tensile strength of the repair before healing is most directly proportional to the:





Explanation

Biomechanical studies have consistently shown that the initial tensile strength of a flexor tendon repair is most directly proportional to the number of core suture strands that cross the repair site (e.g., a 4-strand repair is stronger than a 2-strand repair).

Question 25

A 14-year-old boy presents with a painful scoliosis that is worse at night and relieved by NSAIDs. Imaging reveals a radiolucent nidus with surrounding sclerosis in the pedicle of T8 on the right side. How will this scoliotic deformity most likely present clinically?





Explanation

Spinal osteoid osteomas typically present in the posterior elements and cause asymmetric muscle spasm, leading to a non-structural scoliosis. The concavity of the curve is typically directed toward the side of the lesion (the right side in this scenario).

Question 26

During trialing in a primary total knee arthroplasty, the knee is found to be well-balanced and symmetric in full extension, but the flexion gap is unacceptably tight. Which of the following maneuvers is the most appropriate next step to balance the knee?





Explanation

A knee that is balanced in extension but tight in flexion requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component (with anterior referencing) resects more posterior femoral condylar bone, opening the flexion gap. Increasing posterior tibial slope would also work, but decreasing it would make flexion tighter.

Question 27

A 45-year-old heavy laborer presents with persistent anterior shoulder pain. MR arthrogram confirms an isolated Type II SLAP tear. Nonoperative management has failed. Which of the following surgical interventions is most likely to yield the best functional outcome and lowest revision rate in this specific patient profile?





Explanation

In older patients (typically >40 years) or heavy laborers/workers' compensation patients, biceps tenodesis has been shown to have superior clinical outcomes, better pain relief, and lower revision rates compared to arthroscopic SLAP repair.

Question 28

An Evans osteotomy is frequently utilized in the surgical correction of adult acquired flatfoot deformity (Stage IIb) to address severe forefoot abduction. At which precise anatomical location is this lateral column lengthening osteotomy performed?





Explanation

The Evans osteotomy is a lateral column lengthening procedure performed through the anterior calcaneus, typically 1 to 1.5 cm proximal to the calcaneocuboid joint. A bone graft is inserted to lengthen the lateral column and correct forefoot abduction.

Question 29

A 35-year-old patient sustains a coronal shear fracture of the lateral femoral condyle (Hoffa fracture). When planning internal fixation with lag screws, which screw trajectory provides the greatest biomechanical strength?





Explanation

Biomechanical studies have demonstrated that lag screws placed from posterior-to-anterior are significantly stronger for fixing Hoffa fractures because they allow the screw threads to engage the denser anterior cortical bone of the distal femur, providing superior compression.

Question 30

During an ulnar nerve transposition, a surgeon must release several potential sites of compression. The Arcade of Struthers is one such site and is defined as a fascial band extending from the:





Explanation

The Arcade of Struthers is a fascial band located approximately 8 cm proximal to the medial epicondyle, extending from the medial intermuscular septum to the medial head of the triceps. It is a potential site of ulnar nerve compression. Do not confuse it with the ligament of Struthers, which can compress the median nerve.

Question 31

A 6-year-old boy falls from monkey bars and sustains a widely displaced, extension-type supracondylar humerus fracture. On initial presentation in the emergency department, his hand is pale and pulseless. What is the most appropriate next step in management?





Explanation

A pale, pulseless hand in the setting of a displaced supracondylar humerus fracture is a surgical emergency. The immediate next step is urgent closed reduction and percutaneous pinning in the OR. Often, realignment of the fracture unkinks the brachial artery and restores perfusion. Routine angiography delays necessary reduction.

Question 32

A 28-year-old female presents with a slowly enlarging, painful soft tissue mass near her knee joint. Biopsy reveals a biphasic spindle cell neoplasm. Cytogenetic analysis is most likely to demonstrate which of the following translocations?





Explanation

Synovial sarcoma is characterized by the t(X;18) translocation, leading to the SYT-SSX fusion gene. It often presents in young adults as a painful mass near a joint (though rarely intra-articular) and can exhibit biphasic (epithelial and spindle cell) histology.

Question 33

The scapholunate interosseous ligament is the primary stabilizer of the scapholunate articulation. Which anatomical subregion of this ligament possesses the greatest tensile strength and is biomechanically the most important to repair?





Explanation

The scapholunate interosseous ligament has three distinct regions: dorsal, proximal (membranous), and volar. The dorsal portion is the thickest and biomechanically the strongest, being the most critical region to repair to restore normal kinematics. Conversely, the volar portion is the strongest for the lunotriquetral ligament.

Question 34

The introduction of highly cross-linked polyethylene (HXLPE) in total hip arthroplasty has significantly reduced volumetric wear rates. However, the radiation cross-linking process detrimentally affects which of the following material properties?





Explanation

While high doses of gamma radiation induce cross-linking that improves wear resistance, it compromises mechanical properties such as ductility, fatigue crack propagation resistance, and ultimate tensile strength. This makes the material more susceptible to fracture, particularly in thin sections or constrained designs.

Question 35

A 55-year-old man with advanced ankylosing spondylitis presents with a severe, rigid cervicothoracic kyphosis ('chin-on-chest' deformity) causing difficulty with forward gaze and swallowing. An extension osteotomy is planned. Which anatomical level is generally preferred for this corrective osteotomy to maximize safety and correction?





Explanation

The C7-T1 level is preferred for an extension osteotomy in ankylosing spondylitis because the spinal canal is relatively wide at this level, reducing the risk of spinal cord compression. Additionally, the vertebral artery usually enters the transverse foramen at C6, so operating below this level (C7-T1) helps avoid vertebral artery injury.

Question 36

When treating a proximal third extra-articular tibia fracture with an intramedullary nail, the fracture typically drifts into apex anterior (procurvatum) and valgus deformity. To prevent this, blocking (Poller) screws should be placed in the proximal segment in which position relative to the planned path of the nail?





Explanation

Proximal tibia fractures treated with IM nails tend to deform into procurvatum (apex anterior) and valgus (apex medial). Blocking screws are placed on the concave side of the expected deformity to keep the nail centered in the wide metaphysis. The concavity for procurvatum is posterior, and for valgus is lateral. Therefore, blocking screws in the proximal segment go posterior and lateral to the nail path.

Question 37

A 30-year-old sustains a Hawkins Type II talar neck fracture. Which of the following arteries provides the predominant blood supply to the body of the talus, placing it at risk in this injury?





Explanation

The artery of the tarsal canal, a branch of the posterior tibial artery, is the most important blood supply to the body of the talus. Talar neck fractures (especially displaced ones like Hawkins II-IV) often disrupt this vessel, leading to high rates of avascular necrosis.

Question 38

During the physical examination of a knee with a suspected multi-ligamentous injury, the Dial test is performed. The patient demonstrates 15 degrees of increased external rotation at 30 degrees of knee flexion compared to the contralateral side. At 90 degrees of flexion, the external rotation is symmetric bilaterally. This finding indicates an isolated injury to the:





Explanation

A positive Dial test (asymmetry of >10 degrees of external rotation) at 30 degrees of flexion, but negative at 90 degrees, is indicative of an isolated posterolateral corner (PLC) injury. If the test is positive at both 30 and 90 degrees, it suggests a combined injury of the PLC and PCL.

Question 39

Chondrolysis is a devastating complication following the surgical treatment of Slipped Capital Femoral Epiphysis (SCFE). The development of chondrolysis is most strongly associated with which of the following factors?





Explanation

Unrecognized intra-articular hardware penetration is the most common iatrogenic cause of chondrolysis in SCFE treatment. It causes severe mechanical damage to the articular cartilage, leading to rapid joint space narrowing, stiffness, and pain.

Question 40

Articular cartilage is divided into four distinct structural zones. Which zone is characterized by having the highest concentration of water, the lowest concentration of proteoglycans, and collagen fibrils aligned parallel to the joint surface?





Explanation

The superficial (tangential) zone of articular cartilage comprises 10-20% of articular cartilage thickness. It possesses the highest water content, the lowest proteoglycan concentration, and collagen fibrils (mostly Type II) oriented parallel to the joint surface to resist shear forces.

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