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Arab Orthopaedic Board MCQs - Part 22

27 Apr 2026 79 min read 72 Views
Arab Ortho Board MCQs - Part 21

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In this comprehensive guide, we discuss everything you need to know about Arab Orthopaedic Board MCQs - Part 22. Practice Arab Orthopaedic Board MCQs Part 22. Review orthopedic surgery questions 1051 to 1100 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 22

Comprehensive 100-Question Exam


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Question 1

A 14-year-old boy presents with a rapidly enlarging soft tissue mass in his forearm. Biopsy reveals small round blue cells. Cytogenetic analysis demonstrates a t(2;13) chromosomal translocation. What is the most likely diagnosis?





Explanation

The t(2;13) chromosomal translocation is characteristic of alveolar rhabdomyosarcoma, resulting in the PAX3-FOXO1 fusion gene. Ewing sarcoma is associated with t(11;22), synovial sarcoma with t(X;18), clear cell sarcoma with t(12;22), and myxoid liposarcoma with t(12;16).

Question 2

What is the primary biological advantage of using highly cross-linked polyethylene (HXLPE) compared to conventional polyethylene in total hip arthroplasty?





Explanation

The primary advantage of highly cross-linked polyethylene is the significant reduction in volumetric wear and the consequent decrease in the generation of submicron wear debris, which is the primary driver of macrophage-induced osteolysis. However, the cross-linking and subsequent remelting processes decrease its fatigue crack resistance, ductility, and ultimate tensile strength.

Question 3

In an anteroposterior compression (APC) type II pelvic ring injury (Young-Burgess classification), which of the following ligaments are typically ruptured?





Explanation

APC II injuries involve a 'subluxed' sacroiliac joint characterized by rupture of the anterior sacroiliac ligament, as well as the sacrotuberous and sacrospinous ligaments. The posterior sacroiliac ligament complex remains intact, which maintains vertical stability despite rotational instability (open book pelvis).

Question 4

A 12-year-old boy undergoes in situ pinning for a unilateral slipped capital femoral epiphysis (SCFE). Which of the following is the strongest indication for prophylactic pinning of the contralateral, currently asymptomatic hip?





Explanation

Patients with underlying endocrinopathies (such as hypothyroidism, growth hormone deficiency, or renal osteodystrophy) have an exceptionally high risk (up to 100% in some series) of developing bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly indicated in this population. Age < 10 or > 16 is also a relative indication, but endocrinopathy is the strongest.

Question 5

In a patient with an irreversible high radial nerve palsy, a common tendon transfer to restore wrist extension and finger extension utilizes the Pronator Teres (PT) to Extensor Carpi Radialis Brevis (ECRB) and Flexor Carpi Radialis (FCR) to Extensor Digitorum Communis (EDC). Which of the following is an absolute prerequisite for using the FCR for this transfer?





Explanation

Before transferring the FCR to restore finger extension, the surgeon must ensure the FCU is intact and functional. If the FCR is transferred and the FCU is weak or absent, the patient will lose significant active wrist flexion capability, leading to severe functional impairment.

Question 6

An 82-year-old man presents with neck pain following a ground-level fall. Imaging reveals a Type II odontoid fracture with 3 mm of posterior displacement. He is neurologically intact but suffers from severe osteoporosis and frailty. What is the most appropriate management?





Explanation

In frail elderly patients (>80 years) with Type II odontoid fractures, both surgery and halo vest immobilization carry very high morbidity and mortality rates. The current standard of care for these patients often leans toward a hard cervical collar, accepting a stable fibrous nonunion, which is typically asymptomatic and allows for early mobilization with significantly fewer complications.

Question 7

During an anatomical reconstruction of the posterolateral corner (PLC) of the knee, the surgeon aims to recreate the three primary static stabilizing structures. Which of the following correctly identifies these three structures?





Explanation

The three major static stabilizers of the posterolateral corner (PLC) of the knee are the fibular collateral ligament (also known as the lateral collateral ligament), the popliteus tendon, and the popliteofibular ligament. Anatomical PLC reconstructions (such as the LaPrade technique) specifically reconstruct these three distinct structures.

Question 8

A 28-year-old woman presents with a symptomatic cavovarus foot deformity secondary to Charcot-Marie-Tooth disease. A Coleman block test is performed, and her hindfoot varus corrects completely to neutral. Which of the following procedures is most appropriate to address the skeletal driver of her deformity?





Explanation

The Coleman block test distinguishes a flexible hindfoot varus from a rigid hindfoot varus. If the hindfoot varus corrects to neutral when the first ray is allowed to drop off the block, the varus is flexible and primarily driven by a rigid, plantarflexed first ray (forefoot driven). The appropriate skeletal treatment is a dorsiflexion osteotomy of the 1st metatarsal, usually accompanied by soft tissue balancing (e.g., plantar fascia release, peroneus longus to brevis transfer).

Question 9

Bone morphogenetic proteins (BMPs) play a crucial role in bone healing and osteoinduction. Following the binding of BMP to its cell surface receptor, which intracellular signaling molecules are directly phosphorylated to translocate to the nucleus and regulate gene expression?





Explanation

BMPs signal primarily through a Smad-dependent pathway. Binding of BMP to its specific serine/threonine kinase receptors leads to the phosphorylation of receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. These R-Smads then form a complex with the common-mediator Smad (Smad 4) and translocate into the nucleus to activate the transcription of osteogenic target genes.

Question 10

In Legg-Calve-Perthes disease, which of the following is considered the most significant and reliable prognostic factor regarding the long-term development of premature osteoarthritis?





Explanation

Age at clinical onset is the most consistently reported prognostic factor in Legg-Calve-Perthes disease. Children who develop the disease at a younger age (especially <6 years) have a significantly better prognosis for remodeling the femoral head and a lower risk of premature osteoarthritis, as they have more remaining growth potential.

Question 11

Biomechanical studies evaluating the fixation of coronal shear fractures of the lateral femoral condyle (Hoffa fractures) have demonstrated that the most stable construct is achieved with which of the following techniques?





Explanation

Biomechanical studies have shown that posterior-to-anterior (PA) directed lag screws provide superior biomechanical stability for Hoffa fractures compared to anterior-to-posterior (AP) directed screws. The PA trajectory places the screws more perpendicular to the coronal fracture plane, providing superior compression against the typical shear forces of joint loading.

Question 12

During a total knee arthroplasty for a severe varus deformity, the knee remains tight medially in both flexion and extension after making the initial bone cuts and removing all medial osteophytes. Which of the following medial structures should be released next to balance the gaps symmetrically?





Explanation

In a stepwise medial release for a varus knee, osteophytes are removed first. If the joint remains tight in both flexion and extension, the deep MCL (which is often inherently released during a standard medial tibial exposure) and the posteromedial capsule are addressed next. The superficial MCL (sMCL) is preserved initially and is only progressively released off its tibial insertion if tightness persists after deep MCL/posteromedial corner release.

Question 13

A 42-year-old carpenter presents with chronic dorsal wrist pain. Radiographs demonstrate sclerosis of the lunate, normal carpal height, and negative ulnar variance. An MRI confirms avascular necrosis of the lunate without fragmentation. What is the most appropriate surgical intervention?





Explanation

The patient has Lichtman Stage II Kienbock's disease (sclerosis, intact lunate anatomy, no carpal collapse) with negative ulnar variance. Joint-leveling procedures, such as a radial shortening osteotomy, are the treatment of choice. This mechanically unloads the lunate fossa, allowing for potential revascularization or halting of disease progression prior to carpal collapse.

Question 14

According to the Wiltse classification of spondylolisthesis, which subtype is characterized by an elongation or attenuation of the pars interarticularis without a frank bony defect or acute fracture?





Explanation

The Wiltse classification categorizes spondylolisthesis by etiology. Type II is isthmic (involving the pars interarticularis). Type IIa involves a pars fatigue fracture (lytic). Type IIb involves an elongated, attenuated pars without a complete separation, believed to result from repeated microfractures that heal in an elongated state. Type IIc is an acute traumatic pars fracture.

Question 15

A 65-year-old male with a symptomatic SLAP tear and an intact rotator cuff is undergoing arthroscopy. The surgeon opts for a biceps procedure. Which of the following is a recognized distinct disadvantage of performing a biceps tenotomy compared to a biceps tenodesis?





Explanation

Biceps tenotomy is simpler, avoids hardware, and allows for faster rehabilitation. However, its primary disadvantages compared to tenodesis are a higher incidence of cosmetic 'Popeye' muscle deformity and a higher rate of localized cramping or fatigue pain in the biceps muscle belly due to the loss of length-tension relationship.

Question 16

Which of the following orthopedic implant combinations is most likely to result in clinically significant galvanic corrosion if placed in direct physical contact within the human body?





Explanation

Galvanic corrosion occurs when two dissimilar metals with significantly different electrochemical potentials (anodic index) are placed in direct physical contact within an electrolytic solution like body fluids. Stainless steel and titanium have a large difference in their electrochemical potentials, making them highly susceptible to severe galvanic corrosion when mixed. Titanium and Co-Cr have closer potentials and are routinely mixed safely in modular arthroplasty components.

Question 17

A 25-year-old male is admitted with a highly comminuted midshaft tibia fracture. The clinical concern for acute compartment syndrome is high. Which of the following intracompartmental pressure measurements is considered the most reliable threshold for diagnosing acute compartment syndrome?





Explanation

The differential pressure (delta P) between the patient's diastolic blood pressure and the measured intracompartmental pressure is the most reliable and validated parameter for diagnosing acute compartment syndrome. A delta P of less than 30 mmHg (meaning the compartment pressure is within 30 mmHg of the diastolic pressure) is an absolute indication for emergency fasciotomy.

Question 18

According to Mirels' criteria for predicting the risk of a pathologic fracture through a metastatic bone lesion, which of the following scenarios yields the highest possible score (3 points) for its respective category?





Explanation

Mirels' scoring system evaluates Site, Pain, Lesion type, and Size (1 to 3 points each). Pain: Mild (1), Moderate (2), Severe/Functional (3). Site: Upper extremity (1), Lower extremity (2), Peritrochanteric (3). Lesion type: Blastic (1), Mixed (2), Lytic (3). Size: <1/3 cortex (1), 1/3 to 2/3 (2), >2/3 (3). Therefore, severe pain yields 3 points. Diaphyseal lower extremity yields 2 points.

Question 19

An 18-month-old girl is evaluated for developmental dysplasia of the hip (DDH). An anteroposterior pelvic radiograph is obtained. Which of the following radiographic parameters is the most reliable metric to evaluate acetabular coverage/dysplasia at this specific age?





Explanation

The acetabular index (or Tonnis angle) is the standard radiographic measure of acetabular roof inclination and dysplasia in children from birth up to approximately 5 to 8 years of age. Wiberg's center-edge angle is used for older children when the femoral head center can be accurately identified. The alpha angle is an ultrasound metric for infants (<6 months).

Question 20

In the Lauge-Hansen classification of ankle fractures, a Supination-External Rotation (SER) injury follows a specific, sequential pattern of structural failure. Which of the following accurately represents Stage III of an SER injury?





Explanation

The Lauge-Hansen SER sequence is: Stage I - Anterior inferior tibiofibular ligament (AITFL) rupture; Stage II - Spiral/oblique fracture of the lateral malleolus; Stage III - Posterior inferior tibiofibular ligament (PITFL) rupture or posterior malleolus fracture; Stage IV - Medial malleolus transverse fracture or deltoid ligament rupture.

Question 21

Which method of cross-linking and sterilization for ultra-high-molecular-weight polyethylene (UHMWPE) components is most associated with late oxidative degradation, subsurface delamination, and premature failure in total hip arthroplasty?





Explanation

Gamma irradiation in air produces free radicals within the polyethylene. When exposed to oxygen in vivo or during shelf storage, these free radicals lead to chain scission and oxidative degradation. This process severely weakens the mechanical properties of the polyethylene, causing subsurface delamination, pitting, and premature wear.

Question 22

A 32-year-old female presents with a recurrent Giant Cell Tumor (GCT) of the distal femur. Surgical curettage is deemed highly morbid, and she is started on Denosumab. What is the mechanism of action of this medication?





Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to the Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By binding to RANKL, it prevents RANKL from activating the RANK receptor on the surface of osteoclasts and their precursors, thereby inhibiting osteoclastogenesis and drastically reducing bone resorption in conditions like GCT and osteoporosis.

Question 23

A 45-year-old male sustains a high-energy subtrochanteric femur fracture. Due to the muscular attachments on the proximal fracture fragment, what is the expected clinical deformity of the proximal segment?





Explanation

The proximal fragment in a subtrochanteric fracture is characteristically displaced into flexion (by the iliopsoas muscle attaching to the lesser trochanter), abduction (by the gluteus medius and minimus attaching to the greater trochanter), and external rotation (by the short external rotators attaching to the posteromedial greater trochanter).

Question 24

A 55-year-old male undergoes a total hip arthroplasty utilizing a ceramic-on-ceramic bearing surface. One year later, he complains of a highly audible 'squeaking' noise when walking. Which of the following factors is most strongly associated with this phenomenon?





Explanation

Squeaking in ceramic-on-ceramic THA is a recognized complication and is most strongly associated with edge loading. Edge loading occurs due to component malpositioning, particularly acetabular cup retroversion, excessive anteversion, or steep inclination (abduction angle). This causes stripe wear and loss of fluid-film lubrication, resulting in the characteristic squeak.

Question 25

According to the Denis classification of sacral fractures, which zone has the highest incidence of associated neurological injury (e.g., cauda equina syndrome, bowel/bladder dysfunction)?





Explanation

The Denis classification divides sacral fractures into three zones. Zone I (alar) involves the sacral ala lateral to the foramina. Zone II (foraminal) involves the neural foramina and is often associated with isolated nerve root injuries (e.g., L5, S1). Zone III (central) involves the sacral spinal canal and has the highest rate of severe neurologic injury (>50%), including saddle anesthesia and bowel/bladder incontinence.

Question 26

A 30-year-old male sustains a Hawkins Type II talar neck fracture. At the 6-week follow-up radiograph, a subchondral radiolucent band is noted in the dome of the talus (Hawkins sign). What does this radiographic finding indicate?





Explanation

Hawkins sign is a subchondral radiolucency in the talar dome typically seen 6 to 8 weeks after a talar neck fracture. It represents subchondral atrophy due to disuse osteopenia, which requires an intact blood supply to occur. Therefore, the presence of Hawkins sign is a highly reliable indicator of talar body viability and virtually excludes the development of complete avascular necrosis (AVN).

Question 27

During a physical examination of a patient with a suspected multiligamentous knee injury, the Dial test is performed. The patient exhibits 15 degrees of increased external rotation compared to the contralateral knee at 30 degrees of flexion, but symmetric external rotation at 90 degrees of flexion. What is the most likely diagnosis?





Explanation

The Dial test evaluates external rotation of the tibia. Increased external rotation (>10 degrees compared to the normal side) at 30 degrees of knee flexion, but NOT at 90 degrees, indicates an isolated Posterolateral Corner (PLC) injury. If increased external rotation is present at both 30 and 90 degrees, it suggests a combined injury to both the PLC and the Posterior Cruciate Ligament (PCL).

Question 28

When treating congenital talipes equinovarus (clubfoot) using the Ponseti method, what is the correct anatomical sequence for correcting the deformity?





Explanation

The Ponseti method dictates a specific sequence of correction remembered by the mnemonic CAVE: Cavus, Adductus, Varus, and Equinus. The cavus deformity is corrected first by elevating the first metatarsal (supinating the forefoot). This unlocks the transverse tarsal joint, allowing subsequent correction of adductus and varus by abducting the foot around the fixed talar head. Equinus is corrected last, typically requiring a percutaneous Achilles tenotomy.

Question 29

Based on the Lauge-Hansen classification for ankle fractures, what is the defining structural failure in Stage III of a Supination-External Rotation (SER) injury mechanism?





Explanation

The Supination-External Rotation (SER) mechanism has four stages. Stage I: Rupture of the AITFL. Stage II: Spiral/oblique fracture of the distal fibula. Stage III: Rupture of the PITFL or avulsion fracture of its tibial attachment (posterior malleolus). Stage IV: Transverse fracture of the medial malleolus or rupture of the deltoid ligament.

Question 30

A surgeon is performing a Direct Anterior Approach (Smith-Petersen) to the hip for a primary total hip arthroplasty. What muscles define the deep internervous plane in this approach?





Explanation

The Smith-Petersen (Direct Anterior) approach exploits true internervous planes. The superficial plane is between the Sartorius (femoral nerve) and the Tensor Fasciae Latae (superior gluteal nerve). The deep plane lies between the Rectus femoris (femoral nerve) and the Gluteus medius (superior gluteal nerve).

Question 31

A 25-year-old male is brought to the trauma bay after a motorcycle accident with a severe C5 burst fracture and profound quadriplegia. His blood pressure is 80/50 mmHg and his heart rate is 48 beats per minute. His extremities are warm and pink. What is the primary pathophysiologic mechanism responsible for his hemodynamic state?





Explanation

The patient is in neurogenic shock, typical of severe cervical or high thoracic spinal cord injuries. The mechanism is a loss of sympathetic descending tone, which leads to unopposed parasympathetic tone (vagal nerve remains intact). This results in profound peripheral vasodilation (hypotension with warm extremities) and an inability to mount a tachycardic response (bradycardia).

Question 32

Which of Kanavel's cardinal signs is generally considered the most sensitive and earliest indicator of acute pyogenic flexor tenosynovitis?





Explanation

Kanavel's four cardinal signs of flexor tenosynovitis are: 1) Flexed resting posture of the digit, 2) Fusiform swelling (sausage digit), 3) Tenderness along the flexor tendon sheath, and 4) Severe pain with passive extension. Pain with passive extension stretches the inflamed synovium and is widely recognized as the earliest and most sensitive sign of the condition.

Question 33

A 55-year-old female presents with stage IIB adult acquired flatfoot deformity (posterior tibial tendon dysfunction). Clinical and radiographic examination reveals a flexible flatfoot with significant forefoot abduction (talonavicular uncoverage of 45%). What surgical intervention is most appropriate to specifically address the excessive forefoot abduction?





Explanation

Stage II posterior tibial tendon dysfunction indicates a flexible flatfoot deformity. Stage IIA has no significant forefoot abduction and is typically treated with an FDL transfer and MDCO. Stage IIB is defined by significant forefoot abduction (typically >30-40% talonavicular uncoverage). To correct this, a lateral column lengthening (such as an Evans calcaneal osteotomy) must be added to the FDL transfer and MDCO.

Question 34

A 14-year-old boy presents with an aggressive diaphyseal lesion of the femur. Biopsy reveals small round blue cells. Molecular testing is positive for the t(11;22)(q24;q12) chromosomal translocation. Which fusion gene product is characteristic of this tumor?





Explanation

The clinical presentation and histology are classic for Ewing sarcoma. Over 85% of Ewing sarcomas exhibit the t(11;22)(q24;q12) translocation, which fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11, resulting in the EWS-FLI1 fusion protein. SYT-SSX is found in synovial sarcoma, PAX3-FOXO1 in alveolar rhabdomyosarcoma, and TLS-CHOP in myxoid liposarcoma.

Question 35

Normal articular cartilage is divided into distinct structural zones. Which of the following best describes the histologic and biochemical characteristics of the superficial (tangential) zone?





Explanation

The superficial (tangential) zone of articular cartilage represents 10-20% of the thickness. It has the highest water content (up to 80%), lowest proteoglycan content, and features densely packed collagen fibers aligned parallel to the joint surface to resist shear forces. The deep zone features vertically aligned collagen fibers, lowest water content, and highest proteoglycan content to resist compressive loads.

Question 36

Which of the following is considered an absolute indication for prophylactic in situ pinning of the contralateral, asymptomatic hip in a patient diagnosed with a unilateral Slipped Capital Femoral Epiphysis (SCFE)?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended and considered essentially absolute in patients with underlying metabolic or endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy), as their risk of bilateral disease can approach 100%. Other relative indications include young age (e.g., modified Oxford bone age score), prior radiation therapy, and inability to follow up, but endocrinopathy remains the strongest indication.

Question 37

In the process of bone remodeling, what is the primary biochemical role of osteoprotegerin (OPG)?





Explanation

Osteoprotegerin (OPG) is a glycoprotein produced by osteoblasts that acts as a soluble decoy receptor. It competitively binds to RANK Ligand (RANKL), preventing RANKL from binding to the RANK receptor on the surface of osteoclast precursors. This interaction strongly inhibits the differentiation, activation, and survival of osteoclasts, thereby decreasing bone resorption.

Question 38

A 13-year-old female sustains a juvenile Tillaux fracture of the ankle. What is the characteristic mechanism of injury and the specific anatomic structure responsible for the avulsion?





Explanation

A juvenile Tillaux fracture is a Salter-Harris type III fracture of the anterolateral portion of the distal tibial epiphysis. It occurs during early adolescence when the medial and central aspects of the distal tibial physis have closed, but the anterolateral portion remains open. An external rotation force causes the Anterior Inferior Tibiofibular Ligament (AITFL) to avulse the unfused anterolateral epiphysis.

Question 39

In the surgical management of the 'terrible triad' of the elbow (elbow dislocation, radial head fracture, and coronoid fracture), restoring posterolateral rotatory stability is critical. Which ligamentous structure must be meticulously repaired to address this specific instability?





Explanation

The Lateral Ulnar Collateral Ligament (LUCL) is the primary restraint to posterolateral rotatory instability (PLRI) of the elbow. In a terrible triad injury, the standard surgical algorithm involves fixing or replacing the radial head, addressing the coronoid/anterior capsule, and rigorously repairing the LUCL to restore lateral stability and prevent subluxation.

Question 40

A 22-year-old male presents with chronic, painful scoliosis. Radiographs demonstrate a 3.0 cm expansile, lytic lesion with a sclerotic rim in the pedicle of the L3 vertebra. The patient reports that his pain is dull, aching, and not reliably relieved by nonsteroidal anti-inflammatory drugs (NSAIDs). What is the most likely diagnosis?





Explanation

Osteoblastoma is a benign bone-forming tumor that is histologically identical to an osteoid osteoma but is distinguished clinically and radiographically. Osteoblastomas are typically larger than 2 cm, frequently involve the posterior elements of the spine (causing painful scoliosis), tend to be progressive, and characteristically do NOT have the dramatic pain relief with NSAIDs seen in osteoid osteomas.

Question 41

A 35-year-old male falls from a height and sustains a U-shaped sacral fracture with spinopelvic dissociation. On examination, he has bilateral lower extremity weakness and perianal numbness. Which of the following is the most appropriate surgical stabilization technique to restore spinopelvic continuity?





Explanation

Spinopelvic dissociation (such as a U-shaped sacral fracture) disconnects the axial spine from the pelvis. Lumbopelvic fixation (triangular osteosynthesis) bridging the lower lumbar spine to the ilium is biomechanically necessary to restore the weight-bearing axis and allow early mobilization, especially when combined with decompression for neurologic deficits. Iliosacral screws alone are insufficient to resist the shear forces in complete spinopelvic dissociation.

Question 42

A 6-week-old infant with developmental dysplasia of the hip (DDH) is treated with a Pavlik harness. During a follow-up visit, the parents report that the infant is no longer kicking the right leg. On examination, the right knee is extended, and there is an absence of active knee extension. Which of the following adjustments to the Pavlik harness is required?





Explanation

The infant presents with femoral nerve palsy, a known complication of excessive hip flexion in a Pavlik harness. The anterior straps control the degree of hip flexion. Loosening the anterior straps reduces hyperflexion, which typically relieves the compression on the femoral nerve, leading to spontaneous recovery.

Question 43

Which of the following zones of articular cartilage has the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils oriented strictly perpendicular to the joint surface?





Explanation

Articular cartilage is divided into distinct zones. The deep (radial) zone contains the highest concentration of proteoglycans and the lowest concentration of water. The large-diameter collagen fibrils in this zone are oriented perpendicularly to the articular surface to provide maximal resistance to compressive forces.

Question 44

In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced wear rates compared to conventional polyethylene. Which of the following mechanical properties is most likely decreased as a direct result of the high-dose irradiation process used to create HXLPE?





Explanation

The process of highly cross-linking polyethylene through high-dose irradiation significantly improves wear resistance but compromises its mechanical properties, resulting in a decrease in fatigue strength, yield strength, and ultimate tensile strength. Free radicals generated during irradiation must be quenched (e.g., via remelting or annealing) to prevent oxidation.

Question 45

A 65-year-old male presents with worsening clumsiness in his hands and difficulty walking. Examination reveals hyperreflexia in both lower extremities, a positive Hoffmann's sign bilaterally, and intrinsic hand muscle wasting. What does the presence of a positive 'finger escape sign' (Wartenberg's sign of the hand) in this patient specifically indicate?





Explanation

The 'finger escape sign' is the inability to hold the ulnar digits in extension and adduction. In the setting of cervical spondylotic myelopathy (CSM), it is caused by central weakness of the intrinsic hand muscles (specifically the palmar interossei) and hypertonicity of the extensor muscles. It is a classic upper motor neuron finding in CSM.

Question 46

A 28-year-old carpenter lacerates his index finger with a utility knife. Surgical exploration reveals a complete laceration of both the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) within Zone II. Which of the following correctly describes the anatomical boundaries of flexor tendon Zone II?





Explanation

Flexor tendon Zone II (historically referred to as 'no man's land') extends from the proximal edge of the A1 pulley (at the level of the metacarpophalangeal joint) to the insertion of the FDS on the middle phalanx. It is characterized by the presence of both FDS and FDP tendons tightly enclosed within the same fibro-osseous sheath.

Question 47

A 14-year-old boy presents with knee pain and a palpable mass in the distal femur. Radiographs show a permeative, destructive lesion in the metaphysis with a 'sunburst' periosteal reaction. Biopsy reveals sheets of uniform, small round blue cells. Immunohistochemistry is strongly positive for CD99 (MIC2). Which chromosomal translocation is most characteristic of this tumor?





Explanation

The patient has Ewing sarcoma, characterized by small round blue cells and CD99 positivity. The most common chromosomal translocation is t(11;22)(q24;q12), which results in the EWS-FLI1 fusion protein. t(X;18) is seen in synovial sarcoma. t(2;13) is seen in alveolar rhabdomyosarcoma. t(12;16) is seen in myxoid liposarcoma.

Question 48

A 24-year-old football player sustains a hyperplantarflexion injury to his midfoot. Weight-bearing radiographs demonstrate a 3 mm widening of the interval between the bases of the first and second metatarsals. Which of the following ligaments is primarily disrupted in this classic injury pattern?





Explanation

The Lisfranc ligament is an oblique interosseous ligament that connects the lateral aspect of the medial (first) cuneiform to the medial base of the second metatarsal. It is the strongest and most critical ligament for the stability of the tarsometatarsal joint complex. There is no direct transverse ligamentous connection between the bases of the first and second metatarsals.

Question 49

In secondary fracture healing, the cartilaginous soft callus is eventually replaced by woven bone. Which of the following physiological processes predominantly facilitates this specific transformation?





Explanation

Secondary fracture healing occurs in stages: hematoma, soft callus (cartilage), hard callus (woven bone), and remodeling (lamellar bone). The transition from a cartilaginous soft callus to a woven bone hard callus occurs exclusively via endochondral ossification. Intramembranous ossification occurs directly subperiosteally without a cartilage intermediate.

Question 50

A 68-year-old female presents with an audible and palpable 'clunk' in her knee 9 months after a posterior-stabilized total knee arthroplasty. The clunk occurs as the knee actively extends from 45 degrees of flexion. What is the most likely pathophysiologic cause of this phenomenon?





Explanation

Patellar clunk syndrome is a complication unique to posterior-stabilized TKA. It is caused by the formation of a fibrotic nodule on the undersurface of the distal quadriceps tendon. During knee flexion, the nodule falls into the intercondylar box of the femoral component. As the knee actively extends, the nodule catches on the superior edge of the box and 'clunks' as it snaps out.

Question 51

A 35-year-old skier sustains a Schatzker type II tibial plateau fracture (split-depression of the lateral plateau). Which of the following is the most commonly associated intra-articular soft-tissue injury in this fracture pattern?





Explanation

Schatzker type II fractures (split-depression of the lateral tibial plateau) are caused by valgus and axial loading forces. The lateral meniscus is frequently torn or incarcerated within the fracture fragments (particularly the depressed articular fragment) in up to 50% of cases and must be addressed during surgical fixation.

Question 52

A 13-year-old obese boy undergoes in situ single-screw fixation for a mild, stable slipped capital femoral epiphysis (SCFE). During follow-up, he demonstrates limited hip internal rotation and pain with combined flexion, adduction, and internal rotation. Which of the following is the most likely long-term complication explaining his symptoms?





Explanation

Following in situ fixation of a SCFE, the residual prominent anterior metaphysis can abut the anterior acetabular rim during hip flexion and internal rotation. This biomechanical mismatch leads to cam-type femoroacetabular impingement (FAI), causing pain and restricted range of motion. AVN and chondrolysis are less common in mild, stable slips treated with a single screw.

Question 53

A 29-year-old male sustains a midshaft humerus fracture and presents with a complete radial nerve palsy. He is managed conservatively in a functional brace. At 12 weeks, there is no clinical or electromyographic (EMG) evidence of nerve recovery. Tendon transfers are planned. Which of the following is the most commonly used donor tendon to restore active wrist extension?





Explanation

In standard radial nerve palsy tendon transfers, the pronator teres (PT) is the most commonly used donor muscle to restore wrist extension by transferring it to the extensor carpi radialis brevis (ECRB). The ECRB is chosen as the recipient because its central insertion provides balanced wrist extension without severe radial deviation.

Question 54

A 75-year-old male is evaluated after a low-energy fall. Cervical spine CT reveals a displaced Type II odontoid fracture. He has no neurologic deficits. His past medical history is significant for severe COPD and osteoporosis. Which of the following is the most appropriate definitive management?





Explanation

Type II odontoid fractures in the elderly have an unacceptably high rate of nonunion. Halo vest immobilization is poorly tolerated and carries high morbidity/mortality, especially with severe COPD. Anterior odontoid screw fixation requires good bone quality and is often contraindicated in severe osteoporosis. Posterior C1-C2 fusion provides the highest union rates and immediate stability, making it the preferred surgical choice for elderly patients.

Question 55

A 22-year-old male athlete undergoes arthroscopic stabilization for recurrent anterior shoulder instability. The surgeon identifies a bony Bankart lesion involving 25% of the anterior glenoid width. What is the most appropriate management of this bony defect?





Explanation

In the setting of recurrent anterior shoulder instability, a critical anterior glenoid bone loss of greater than 20-25% results in an unacceptably high failure rate for isolated arthroscopic soft-tissue repair. The most appropriate management to restore anterior stability is a bony augmentation procedure, most commonly the Latarjet procedure.

Question 56

The anterior approach (Smith-Petersen) to the hip utilizes a true internervous plane. Which of the following best describes the specific internervous plane used in the superficial dissection of this surgical approach?





Explanation

The superficial internervous plane of the anterior (Smith-Petersen) approach to the hip lies between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). The deep plane is between the rectus femoris (femoral nerve) and the gluteus medius (superior gluteal nerve).

Question 57

A 45-year-old male is scheduled for open reduction and internal fixation of a closed tibial shaft fracture. He has a documented history of MRSA colonization and a severe anaphylactic allergy to penicillin (hives and shock). Which of the following is the most appropriate preoperative prophylactic antibiotic?





Explanation

For patients with a severe, IgE-mediated (anaphylactic) penicillin allergy, cephalosporins (like cefazolin and ceftriaxone) are generally avoided due to the small risk of cross-reactivity. Given the patient's documented history of MRSA colonization, Vancomycin is the definitive choice for preoperative prophylaxis to provide adequate coverage while avoiding an anaphylactic reaction.

Question 58

A 55-year-old male with poorly controlled type 2 diabetes presents with a swollen, warm, and erythematous right foot. There are no open ulcers, and his systemic inflammatory markers are normal. Radiographs reveal fragmentation and early subluxation of the talonavicular and calcaneocuboid joints. According to the Eichenholtz classification, what stage of Charcot arthropathy is this patient currently in, and what is the mainstay of treatment?





Explanation

The patient is in Eichenholtz Stage 1 (Developmental/Fragmentation), characterized by erythema, warmth, swelling, and radiographic evidence of bone debris, fragmentation, and joint subluxation. The mainstay of treatment in the acute fragmentation phase is strict offloading, typically achieved with total contact casting (TCC) to prevent further deformity until the active inflammatory phase resolves.

Question 59

During surgical release of a severe trigger finger, a surgeon inadvertently incises the entire A2 pulley of the middle finger. What biomechanical consequence is most likely to occur as a direct result of this specific iatrogenic injury?





Explanation

The A2 and A4 pulleys are the critical biomechanical pulleys in the flexor tendon sheath of the digits, holding the flexor tendons close to the phalanx. Laceration or incompetence of the A2 or A4 pulley leads to bowstringing of the flexor tendons during active flexion, decreasing mechanical efficiency (excursion) and causing flexion contractures and weakness.

Question 60

Macrophage-induced osteolysis is a primary cause of aseptic loosening in total joint arthroplasty. Which of the following specific wear particles is considered the most biologically active in stimulating the macrophage response leading to osteolysis?





Explanation

The size and volume of wear particles dictate their biological activity. Macrophages preferentially phagocytose particles in the submicron range (0.1 to 1.0 micrometers). UHMWPE particles within this specific size range are the most numerous and most biologically active culprits in stimulating macrophages to release pro-inflammatory cytokines, ultimately leading to osteoclast activation and osteolysis.

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