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Arab Orthopaedic Board MCQs - Part 21

27 Apr 2026 48 min read 80 Views
Arab Ortho Board MCQs - Part 20

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Here are the crucial details you must know about Arab Orthopaedic Board MCQs - Part 21. Practice Arab Orthopaedic Board MCQs Part 21. Review orthopedic surgery questions 1001 to 1050 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 21

Comprehensive 100-Question Exam


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Question 1

A 35-year-old male sustains an APC-III pelvic ring injury. During the ilioinguinal approach for anterior ring fixation, massive hemorrhage is encountered as the surgeon dissects near the superior pubic ramus. Which vascular anastomosis was most likely injured?





Explanation

The 'corona mortis' (crown of death) is a vascular anastomosis between the external iliac or inferior epigastric vessels and the obturator vessels. It is located over the superior pubic ramus, typically 4-9 cm from the pubic symphysis, and is at high risk of injury during the ilioinguinal approach or placement of superior pubic ramus screws, leading to massive hemorrhage.

Question 2

A 12-year-old obese boy presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE). Intraoperatively, an intracapsular hematoma is evacuated. What is the primary blood supply to the femoral head that is at greatest risk of injury in this condition?





Explanation

The lateral epiphyseal artery is the terminal branch of the medial femoral circumflex artery (MFCA) and provides the predominant blood supply to the femoral head in children and adolescents. It is uniquely vulnerable to stretching, kinking, or tearing in SCFE, which can result in avascular necrosis (AVN).

Question 3

A 60-year-old man presents with progressive hand clumsiness and gait imbalance. Neurological examination reveals an inverted brachioradialis reflex. What is the neuroanatomic significance of this specific physical finding?





Explanation

An inverted brachioradialis reflex occurs when tapping the brachioradialis tendon (C5-C6) produces finger flexion (C8) rather than elbow flexion/supination. This finding indicates a lower motor neuron lesion at the level of the reflex (C5/C6, causing loss of the normal reflex) combined with an upper motor neuron lesion below that level (hyperreflexia of the C8 finger flexors), classic for cervical spondylotic myelopathy at C5-C6.

Question 4

Articular cartilage relies on a highly organized extracellular matrix for its biomechanical properties. Which zone of articular cartilage is characterized by the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers oriented perpendicular to the articular surface?





Explanation

The deep (radial) zone of articular cartilage has the highest proteoglycan content, the lowest water content, and thick type II collagen fibers arranged perpendicular to the joint surface. This structural arrangement is critical for resisting compressive forces.

Question 5

A 65-year-old woman undergoes total hip arthroplasty using a highly cross-linked polyethylene liner. What is the primary negative biomechanical consequence of increasing the radiation dose during the cross-linking process of the polyethylene?





Explanation

Highly cross-linked polyethylene (HXLPE) is manufactured by irradiating the material, which creates cross-links that significantly reduce volumetric wear. However, this process decreases the material's mechanical properties, specifically reducing its fatigue strength, ductility, and fracture toughness, making it more susceptible to rim fractures.

Question 6

A 28-year-old female presents with a lytic lesion in the distal femur. Biopsy confirms a Giant Cell Tumor (GCT) of bone. She is treated with Denosumab prior to planned surgical curettage to facilitate joint preservation. What is the precise mechanism of action of Denosumab?





Explanation

Denosumab is a fully human monoclonal antibody that binds to the Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By binding to RANKL, it prevents RANKL from interacting with the RANK receptor on the surface of osteoclasts and their precursors, thereby inhibiting osteoclastogenesis and downregulating bone resorption. Giant cell tumors are rich in RANKL-expressing stromal cells.

Question 7

A 10-year-old boy (Tanner stage I) sustains an acute ACL tear. A physeal-sparing ACL reconstruction is planned using an iliotibial band autograft (MacIntosh procedure). Which of the following best describes the anatomical routing of the graft to minimize physeal injury?





Explanation

In prepubescent children (Tanner stage I or II) with significant remaining growth, a fully physeal-sparing technique is often indicated. The modified MacIntosh (or Kocher) technique involves routing the IT band graft 'over-the-top' of the lateral femoral condyle (avoiding a femoral tunnel) and under the intermeniscal ligament (avoiding a tibial tunnel), suturing it to the tibial periosteum.

Question 8

A 45-year-old male sustains a posteromedial tibial plateau fracture. During a posteromedial surgical approach to the knee, the dissection plane is developed to access the fracture. Which two anatomical structures define the interval for this approach?





Explanation

The posteromedial approach to the tibial plateau uses the internervous/intermuscular interval between the medial head of the gastrocnemius (retracted posteriorly/laterally) and the pes anserinus tendons, specifically the semimembranosus (retracted anteriorly/medially). This provides direct access to the posteromedial buttress of the tibia.

Question 9

In adolescent idiopathic scoliosis (AIS), curve progression is a primary concern guiding treatment. Based on natural history studies, which of the following patients has the highest statistical risk of curve progression?





Explanation

The risk of curve progression in AIS is highest in patients who are female, have a lower Risser stage (indicating significant remaining skeletal growth), and present with larger initial curves (>20 degrees) before skeletal maturity. A 12-year-old female at Risser 0 with a 25-degree curve has a progression risk exceeding 60-80%.

Question 10

A 55-year-old female presents with progressive flattening of her left foot, pain along the medial ankle, and inability to perform a single-leg heel raise. Clinical examination reveals a positive 'too many toes' sign. Which tendon is primarily dysfunctional in the early stages of this condition?





Explanation

The clinical scenario describes Adult Acquired Flatfoot Deformity (AAFD), most commonly caused by posterior tibial tendon dysfunction (PTTD). The tibialis posterior is the primary dynamic stabilizer of the medial longitudinal arch; its failure leads to hindfoot valgus, midfoot abduction (positive 'too many toes' sign), and forefoot supination.

Question 11

A 30-year-old carpenter sustains a laceration to the volar aspect of his index finger at the level of the proximal phalanx. Surgical exploration confirms both the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) are severed. According to the Strickland/Verdan classification, which zone of flexor tendon injury is this?





Explanation

Zone II of the flexor tendon system, historically known as 'no man's land', extends from the proximal aspect of the A1 pulley (distal palmar crease) to the insertion of the FDS on the middle phalanx. Injuries here are notoriously difficult to treat due to the complex interaction between the FDS, FDP, and the fibro-osseous sheath.

Question 12

Bone morphogenetic proteins (BMPs) play a critical role in osteoinduction and are heavily utilized in spinal fusion. Recombinant human BMP-2 acts primarily through binding to cell surface receptors, initiating an intracellular signaling cascade. Which of the following molecules act as the primary intracellular signaling pathway for BMP-2?





Explanation

Bone morphogenetic proteins (BMPs) are members of the TGF-beta superfamily. They bind to serine/threonine kinase receptors on the cell surface, which then phosphorylate the receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. These complex with Smad 4 to enter the nucleus and regulate the transcription of osteogenic genes like Runx2.

Question 13

A 25-year-old male sustains an open tibia fracture. The wound is a 5 cm laceration with moderate soft tissue damage, but there is adequate periosteal coverage of the bone and no massive contamination. According to the Gustilo-Anderson classification, what type of fracture is this, and what is the standard recommended initial antibiotic prophylaxis?





Explanation

A Gustilo-Anderson Type II open fracture is characterized by a wound between 1 and 10 cm in length, moderate soft tissue damage, and adequate bone coverage, without the high-energy periosteal stripping seen in Type III injuries. The standard of care for initial antibiotic prophylaxis in a Type II open fracture is a first-generation cephalosporin (e.g., Cefazolin).

Question 14

A 14-year-old gymnast presents with lower back pain exacerbated by extension. Lateral lumbar radiographs show a pars interarticularis defect at L5 with a 30% anterior translation of L5 on S1. According to the Meyerding classification, what grade of spondylolisthesis does this patient have?





Explanation

The Meyerding classification grades the severity of spondylolisthesis based on the percentage of anterior translation of the superior vertebral body over the inferior one. Grade I is 0-25%, Grade II is 26-50%, Grade III is 51-75%, Grade IV is 76-100%, and Grade V (spondyloptosis) is >100%. A 30% slip falls into Grade II.

Question 15

A 22-year-old baseball pitcher presents with deep shoulder pain during the late cocking phase of throwing. MRI arthrogram reveals a Type II SLAP (Superior Labrum Anterior to Posterior) tear. What is the defining anatomical characteristic of a Type II SLAP lesion?





Explanation

Snyder's classification for SLAP lesions: Type I is degenerative fraying with an intact biceps anchor. Type II is detachment of the superior labrum and biceps anchor from the glenoid rim. Type III is a bucket-handle tear of the labrum with an intact biceps anchor. Type IV is a bucket-handle tear extending into the biceps tendon.

Question 16

When diagnosing a periprosthetic joint infection (PJI), clinicians often rely on the Musculoskeletal Infection Society (MSIS) criteria. Which of the following findings is considered one of the 'major' criteria, which by itself is definitively diagnostic for a PJI?





Explanation

According to the internationally recognized MSIS criteria for PJI, there are two 'major' criteria: 1) A sinus tract communicating with the prosthesis, and 2) Two positive periprosthetic cultures with phenotypically identical organisms. The presence of either definitively diagnoses a PJI. The other options are minor criteria.

Question 17

A 16-year-old male complains of severe night pain in his right mid-thigh that is dramatically relieved by aspirin. Radiographs show a thickened cortical diaphyseal area with a 7 mm radiolucent nidus. What is the most appropriate initial definitive treatment for this condition?





Explanation

The clinical presentation (night pain relieved by NSAIDs/aspirin) and radiographic findings (cortical thickening with a <1.5 cm radiolucent nidus) are classic for an osteoid osteoma. The standard of care for definitive treatment, if conservative medical management fails or is undesired, is minimally invasive CT-guided Radiofrequency Ablation (RFA).

Question 18

The Ponseti method is the internationally recognized gold standard for the conservative management of idiopathic clubfoot (talipes equinovarus). What is the correct sequence of deformity correction during serial casting in this technique?





Explanation

The Ponseti method sequentially corrects the deformities of clubfoot using the acronym CAVE: first Cavus (by elevating the first ray to align the forefoot with the midfoot), then Adductus and Varus (simultaneously by abducting the midfoot around the talar head), and finally Equinus (usually requiring a percutaneous Achilles tenotomy).

Question 19

A 32-year-old man sustains a closed tibial shaft fracture and presents to the ER complaining of severe pain out of proportion to the injury. His blood pressure is 120/80 mmHg. Intracompartmental pressure testing is performed to evaluate for acute compartment syndrome. Which measurement strongly indicates the need for an emergent four-compartment fasciotomy?





Explanation

Acute compartment syndrome is definitively diagnosed using the delta pressure, which is calculated as the Diastolic Blood Pressure minus the Absolute Compartment Pressure. A delta pressure of < 30 mmHg indicates critically impaired tissue perfusion and is an absolute indication for emergent fasciotomy. A delta P of 20 mmHg (e.g., Diastolic 80 - Compartment 60 = 20) falls well below this critical threshold.

Question 20

A 24-year-old football player presents with midfoot pain after a hyper-plantarflexion injury. Radiographs reveal widening of the space between the bases of the first and second metatarsals, raising suspicion for a Lisfranc injury. What is the true anatomical path of the intact Lisfranc ligament?





Explanation

The Lisfranc ligament is a strong interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is critical for midfoot stability because there is no direct intermetatarsal ligament connecting the first and second metatarsal bases.

Question 21

Which of the following defines the "safe zone" for acetabular component positioning in total hip arthroplasty as classically described by Lewinnek?





Explanation

Lewinnek classically described the safe zone for acetabular cup placement as 40 +/- 10 degrees of abduction (inclination) and 15 +/- 10 degrees of anteversion to minimize the risk of dislocation.

Question 22

A 35-year-old male sustains a "terrible triad" injury of the elbow. Which of the following is the generally recommended surgical sequence for repairing these injuries?





Explanation

The standard inside-out sequence for repairing a terrible triad injury of the elbow is first fixing the coronoid, followed by addressing the radial head (fixation or replacement), and finally repairing the lateral collateral ligament (LCL) complex. MCL repair or hinged external fixation may be added if instability persists.

Question 23

A 12-year-old obese male presents with a slipped capital femoral epiphysis (SCFE). Which of the following best describes the anatomical direction of the epiphyseal displacement relative to the metaphysis?





Explanation

In SCFE, the epiphysis actually remains relatively housed in the acetabulum while the femoral neck (metaphysis) displaces anteriorly and superiorly. Therefore, relative to the metaphysis, the epiphysis slips posteriorly and inferiorly.

Question 24

During reconstruction of the posterior cruciate ligament (PCL), recreating the anterolateral (AL) bundle is crucial. At what degree of knee flexion is the AL bundle of the native PCL most taut?





Explanation

The PCL consists of two main bundles: the anterolateral (AL) and posteromedial (PM) bundles. The AL bundle is larger and is most taut in flexion (typically reaching maximum tension around 90 degrees), whereas the PM bundle is most taut in extension.

Question 25

According to Perren's strain theory of fracture healing, what is the maximum strain tolerated by lamellar bone before failure?





Explanation

According to Perren's strain theory, different tissues tolerate different amounts of strain before tearing. Granulation tissue can tolerate up to 100% strain, fibrous tissue and cartilage tolerate around 10-15% strain, while lamellar bone is rigid and can only tolerate about 2% strain before failing.

Question 26

A 60-year-old male presents with clumsy hands and a broad-based gait. Examination reveals an inverted brachioradialis reflex. This clinical finding most specifically localizes the compressive pathology to which cervical spinal level?





Explanation

An inverted brachioradialis reflex (striking the brachioradialis tendon produces finger flexion rather than elbow flexion/supination) indicates a lower motor neuron lesion at C5 or C6 (absent normal reflex) and an upper motor neuron lesion below that level (hyperactive finger flexors, C8). It specifically localizes spinal cord compression to the C5-C6 level.

Question 27

In a patient undergoing a dorsal approach to the wrist for a distal radius fracture, Lister's tubercle serves as a key anatomical landmark. Which extensor compartment lies immediately ulnar to Lister's tubercle?





Explanation

The extensor pollicis longus (EPL) tendon is housed in the third extensor compartment, which runs immediately ulnar to Lister's tubercle before crossing over the second extensor compartment tendons (ECRL and ECRB) to insert on the thumb.

Question 28

In the evaluation of a suspected Lisfranc injury, which radiographic finding is considered the most reliable indicator of instability on a weight-bearing AP view of the foot?





Explanation

The hallmark radiographic sign of a Lisfranc injury on a weight-bearing AP radiograph is a step-off or widening between the medial border of the second metatarsal base and the medial border of the middle cuneiform. A gap of >2mm between the bases of the 1st and 2nd metatarsals is also highly indicative.

Question 29

During a total knee arthroplasty, after making the initial bone cuts and inserting trial components, the surgeon notes that the knee is symmetric and stable in extension, but tight symmetrically in flexion. What is the most appropriate corrective step?





Explanation

A knee that is symmetric and stable in extension but symmetrically tight in flexion indicates an isolated tight flexion gap. The most appropriate and direct step is to decrease the anteroposterior (AP) dimension of the femoral component by downsizing it, which increases the flexion gap without altering the extension gap.

Question 30

A 25-year-old male sustains an APC-III pelvic ring injury. During the surgical approach via the ilioinguinal approach, massive bleeding is encountered posterior to the superior pubic ramus. Which vascular structure is most likely injured?





Explanation

The corona mortis (crown of death) is a vascular anastomosis between the external iliac (or inferior epigastric) and obturator vessels. It is located posterior to the superior pubic ramus, roughly 4-6 cm from the symphysis pubis, and is at significant risk of iatrogenic injury during an ilioinguinal or modified Stoppa approach.

Question 31

A 4-month-old female is diagnosed with developmental dysplasia of the hip (DDH) and treated with a Pavlik harness. Two weeks later, the parents report she has stopped kicking her right leg. Examination reveals an inability to actively extend the knee. This complication is most directly related to which improper fitting of the harness?





Explanation

The patient has a femoral nerve palsy, a known complication of the Pavlik harness. It is caused by excessive hip flexion, which stretches or compresses the femoral nerve against the inguinal ligament. By contrast, excessive abduction is associated with avascular necrosis (AVN) of the femoral head.

Question 32

Which of the following bacteria is most classically associated with the production of a dense glycocalyx (biofilm) that facilitates adhesion to orthopedic implants and resistance to antibiotics?





Explanation

Staphylococcus epidermidis (a coagulase-negative staphylococcus) is notorious for producing a thick exopolysaccharide layer known as a glycocalyx or biofilm. This slime layer allows it to adhere strongly to foreign bodies (such as arthroplasty components) and protects the bacteria from host immune responses and systemic antibiotics.

Question 33

In the Wiltse classification of spondylolisthesis, a slip secondary to an elongated but intact pars interarticularis is classified as:





Explanation

The Wiltse classification defines Type II as Isthmic. It is subdivided into IIA (lytic fatigue fracture of the pars), IIB (elongated but intact pars, due to repeated healed microfractures), and IIC (acute pars fracture). Type I is dysplastic, Type III is degenerative, and Type IV is traumatic (fracture other than pars).

Question 34

In the treatment of osteosarcoma, which of the following is the most important prognostic factor for long-term overall survival?





Explanation

The most powerful predictor of long-term survival in patients with non-metastatic osteosarcoma is the histologic response of the tumor to neoadjuvant chemotherapy, defined by the percentage of tumor necrosis at the time of definitive resection. A good response is typically defined as >= 90% necrosis.

Question 35

A 22-year-old overhead athlete is diagnosed with a superior labrum anterior to posterior (SLAP) tear. Which of the following physical exam tests is most specific for identifying a SLAP lesion?





Explanation

O'Brien's active compression test is classically described for identifying SLAP lesions when deep pain is elicited with the arm forward flexed, adducted, and internally rotated (thumb down), and the pain is relieved when the test is repeated with the arm externally rotated (thumb up). Speed's and Yergason's tests evaluate the long head of the biceps.

Question 36

During the classic volar Henry approach to the radius, the superficial surgical internervous plane lies between which two muscles?





Explanation

The superficial internervous plane for the volar Henry approach is between the brachioradialis (innervated by the radial nerve) and the flexor carpi radialis (innervated by the median nerve).

Question 37

A 40-year-old male sustains a high-energy Schatzker VI tibial plateau fracture. Which of the following findings makes the utilization of a dual-incision (anterolateral and posteromedial) approach mandatory rather than a single lateral approach?





Explanation

A displaced posteromedial fragment is a classic indication for a posteromedial approach because it cannot be adequately reduced or buttressed from an anterolateral approach. A posteromedial buttress plate is typically required to resist the deforming shear forces during weight-bearing.

Question 38

A 55-year-old male presents with painful, limited dorsiflexion of the great toe. Radiographs show dorsal osteophytes at the first metatarsophalangeal joint with preserved joint space on the plantar aspect. What is the most appropriate initial surgical management if non-operative measures fail?





Explanation

The patient has Coughlin and Shurnas Grade 1 or 2 hallux rigidus (preserved plantar joint space with dorsal osteophytes causing mechanical block). A cheilectomy (excision of the dorsal osteophytes and the dorsal third of the metatarsal head) is the procedure of choice. Arthrodesis is reserved for advanced (Grade 3 or 4) disease.

Question 39

In Legg-Calve-Perthes disease, the lateral pillar classification of Herring is optimally assessed during which phase of the disease process?





Explanation

The Herring lateral pillar classification is ideally applied during the early fragmentation stage of Legg-Calve-Perthes disease. This provides the most accurate prognostication based on the maintenance of the height of the lateral pillar of the capital femoral epiphysis.

Question 40

Galvanic corrosion is most likely to occur in orthopedic surgery when which of the following combinations of metals are in direct physical contact within a conductive body fluid environment?





Explanation

Galvanic corrosion occurs when two dissimilar metals with significantly different anodic indices are placed in contact within an electrolytic solution. The combination of stainless steel and titanium alloy leads to rapid galvanic corrosion of the stainless steel and should be avoided. Cobalt-chromium and titanium are closer on the galvanic series and are frequently used together safely.

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