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Arab Orthopaedic Board MCQs - Part 34

27 Apr 2026 75 min read 84 Views
Arab Ortho Board MCQs - Part 33

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Arab Orthopaedic Board MCQs - Part 34

Comprehensive 100-Question Exam


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Question 1

Which of the following Bone Morphogenetic Proteins (BMPs) is FDA-approved for use in acute, open tibial shaft fractures?





Explanation

Recombinant human BMP-2 (rhBMP-2) is FDA-approved for acute, open tibial shaft fractures treated with an intramedullary nail. rhBMP-7 was previously approved under a Humanitarian Device Exemption for recalcitrant nonunions but is no longer commercially available. BMP-3 is an antagonist to osteogenesis.

Question 2

In which of the following patients presenting with a unilateral slipped capital femoral epiphysis (SCFE) is prophylactic pinning of the contralateral asymptomatic hip most strongly indicated?





Explanation

Prophylactic pinning of the contralateral hip is strongly recommended in patients with endocrine disorders (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) due to the high risk of bilateral involvement. It is also considered in patients presenting at a very young age (males <12, females <10) or those undergoing prior radiation therapy.

Question 3

During a primary total knee arthroplasty, the surgeon evaluates the gaps after initial bone cuts. The knee is balanced and symmetric in extension, but it is tight symmetrically in flexion. Which of the following is the most appropriate next step to balance the knee?





Explanation

A knee that is tight in flexion but symmetric and balanced in extension requires an increase in the flexion gap without altering the extension gap. This can be achieved by downsizing the femoral component (which removes more posterior condylar bone) or by releasing the posterior cruciate ligament (PCL) if a cruciate-retaining technique is being used. Recutting the distal femur would affect the extension gap, and increasing the posterior slope of the tibia alters both gaps but risks altering joint biomechanics excessively.

Question 4

A 24-year-old overhead throwing athlete presents with deep shoulder pain and clicking. MR arthrogram reveals a SLAP tear. Arthroscopy demonstrates detachment of the superior labrum and biceps anchor from the superior glenoid, but the biceps tendon itself is intact. Which SLAP tear classification does this represent?





Explanation

This describes a Type II SLAP tear, the most common type. Type I involves fraying of the superior labrum with an intact biceps anchor. Type III is a bucket-handle tear of the superior labrum with an intact biceps anchor. Type IV is a bucket-handle tear of the superior labrum that extends into the biceps tendon.

Question 5

In the repair of Zone II flexor tendon lacerations, which of the following biomechanical factors most significantly increases the ultimate tensile strength of the repair, allowing for early active motion?





Explanation

The most significant factor in increasing the tensile strength of a flexor tendon repair is the number of core suture strands crossing the repair site. A 4-strand or 6-strand repair is significantly stronger than a 2-strand repair, allowing for safe early active motion protocols. While locking configurations also provide some strength benefits, the strand count is the primary determinant of ultimate strength.

Question 6

A 14-year-old male presents with a painful, swollen thigh. Radiographs show a permeative, diaphyseal lesion with an 'onion skin' periosteal reaction. A biopsy is performed. Which of the following cytogenetic abnormalities is most characteristic of this patient's likely diagnosis?





Explanation

The patient's presentation is classic for Ewing sarcoma. The most common chromosomal translocation associated with Ewing sarcoma is t(11;22)(q24;q12), which results in the EWS-FLI1 fusion protein. t(X;18) is seen in Synovial Sarcoma. t(12;16) is seen in Myxoid Liposarcoma. t(2;13) is seen in Alveolar Rhabdomyosarcoma.

Question 7

A 60-year-old Asian male presents with progressive clumsiness in his hands and difficulty walking. Radiographs and CT of the cervical spine reveal a continuous band of ossification along the posterior aspect of the C3-C6 vertebral bodies. MRI shows spinal cord compression with T2 signal change. Which of the following is the most appropriate surgical approach, assuming neutral cervical sagittal alignment?





Explanation

The diagnosis is Ossification of the Posterior Longitudinal Ligament (OPLL). For multi-level (>3 levels) OPLL with neutral or lordotic cervical alignment, a posterior approach such as laminoplasty (or laminectomy with fusion) is preferred to avoid the high complication rates (e.g., dural tears, CSF leak) associated with anterior resection of the ossified mass.

Question 8

The Lisfranc ligament is a critical stabilizing structure of the midfoot. Between which two osseous structures does the primary, strongest band of the Lisfranc ligament course?





Explanation

The Lisfranc ligament courses from the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is the strongest of the tarsometatarsal ligaments and is crucial for the stability of the second tarsometatarsal joint and the midfoot arch. There is no direct transverse ligamentous connection between the first and second metatarsal bases.

Question 9

When applying the Ponseti method for the correction of idiopathic congenital talipes equinovarus (clubfoot), which of the following represents the correct sequence of deformity correction?





Explanation

The Ponseti method corrects the deformities of clubfoot in a specific sequence, remembered by the acronym CAVE: Cavus (corrected by elevating the first ray to supinate the forefoot), Adductus, Varus, and finally Equinus. Equinus is corrected last, often requiring a percutaneous Achilles tenotomy once the foot is abducted to about 60 degrees.

Question 10

Osteoclasts are multinucleated cells responsible for bone resorption. Which of the following signaling molecules directly binds to its receptor on the osteoclast precursor to stimulate its differentiation and activation?





Explanation

RANKL (Receptor activator of nuclear factor kappa-B ligand) is secreted by osteoblasts and binds to the RANK receptor on osteoclast precursors, stimulating their differentiation, activation, and survival. OPG acts as a decoy receptor for RANKL, inhibiting osteoclastogenesis. M-CSF is also required for osteoclast survival but it acts on the c-fms receptor earlier in the lineage.

Question 11

A 45-year-old male sustains a knee injury after a fall from a height. Radiographs reveal a fracture of the medial tibial plateau with associated depression and a separate fracture line extending into the intercondylar eminence. According to the Schatzker classification, which type of fracture is this?





Explanation

A fracture of the medial tibial plateau is classified as a Schatzker Type IV. These fractures are typically higher energy than types I-III (which involve the lateral plateau) and are often associated with knee dislocation or subluxation, meniscal tears, and neurovascular injuries. They occur secondary to varus and axial loading forces.

Question 12

A 65-year-old male presents with groin pain and a palpable mass three years after undergoing a primary total hip arthroplasty using a metal-on-polyethylene bearing with a large-diameter cobalt-chromium femoral head. Aspiration is negative for infection, but MRI shows a fluid collection with a thick pseudocapsule. Blood tests reveal elevated serum cobalt levels with normal chromium levels. Which of the following is the most likely etiology of his symptoms?





Explanation

Elevated cobalt levels out of proportion to chromium levels, combined with an adverse local tissue reaction (ALTR) in a metal-on-polyethylene total hip arthroplasty, strongly suggests trunnionosis. This is mechanically assisted crevice corrosion occurring at the modular head-neck junction. Bearing surface wear in MoP would not cause significantly elevated serum metal ions.

Question 13

A 32-year-old manual laborer presents with chronic, progressive dorsal wrist pain and decreased grip strength. Radiographs reveal sclerosis and early collapse of the lunate, but the overall carpal height is maintained, and there is no scaphoid ring sign. Ulnar variance is negative (-2 mm). What is the most appropriate surgical intervention?





Explanation

The patient has Kienböck's disease (avascular necrosis of the lunate), Lichtman Stage II or early IIIa (collapse without fixed scaphoid rotation or significant carpal height loss). In the presence of negative ulnar variance, a joint-leveling procedure such as a radial shortening osteotomy is the preferred treatment to decrease the compressive forces on the lunate, allowing for possible revascularization.

Question 14

The anterior cruciate ligament (ACL) is composed of two primary bundles. Which of the following statements accurately describes the biomechanical function of the posterolateral (PL) bundle?





Explanation

The ACL consists of the anteromedial (AM) and posterolateral (PL) bundles. The PL bundle is tightest in full extension and serves as the primary restraint to rotatory loads (e.g., resisting the pivot shift). The AM bundle is tightest in flexion (e.g., 90 degrees) and is the primary restraint to anterior tibial translation at that angle.

Question 15

In evaluating an AP pelvis radiograph of a 6-month-old female for Developmental Dysplasia of the Hip (DDH), you draw Hilgenreiner's line and Perkin's line. In a normal, properly developing hip, the ossific nucleus of the femoral head should be located in which quadrant formed by these intersecting lines?





Explanation

On an AP pelvis radiograph, Hilgenreiner's line is drawn horizontally through the triradiate cartilages, and Perkin's line is drawn perpendicular to it at the lateral margin of the ossified acetabulum. In a normal hip, the femoral head ossific nucleus (or the medial beak of the metaphysis if unossified) should lie in the inferomedial quadrant. A subluxated or dislocated hip typically lies in the superolateral quadrant.

Question 16

Articular cartilage is highly specialized and avascular. In which zone of articular cartilage are the collagen fibers oriented perpendicular to the joint surface, providing the highest resistance to compressive forces?





Explanation

In the deep (radial) zone of articular cartilage, the collagen fibers (primarily Type II) are arranged perpendicular to the articular surface. This orientation, along with a high concentration of proteoglycans, provides the greatest resistance to compressive loads. The superficial zone has fibers parallel to the surface to resist shear stress.

Question 17

A 28-year-old female twists her ankle. Radiographs show a short oblique fracture of the lateral malleolus at the level of the syndesmosis and a transverse fracture of the medial malleolus. According to the Lauge-Hansen classification, what is the mechanism of injury?





Explanation

The injury described is a Supination-External Rotation (SER) type fracture, which is the most common ankle fracture pattern. It progresses in stages: (1) Anterior inferior tibiofibular ligament rupture, (2) Short oblique/spiral fracture of the distal fibula at the syndesmosis, (3) Posterior inferior tibiofibular ligament rupture or posterior malleolus fracture, (4) Medial malleolus transverse fracture or deltoid ligament rupture.

Question 18

A 40-year-old male falls from a ladder and sustains an L1 burst fracture. Neurological examination is completely normal. MRI reveals a completely intact posterior ligamentous complex (PLC). Using the Thoracolumbar Injury Classification and Severity Score (TLICS), what is the total score and the most appropriate recommendation for treatment?





Explanation

The TLICS system assigns points based on morphology, neurologic status, and integrity of the PLC. A burst fracture gets 2 points. A normal neurologic exam gets 0 points. An intact PLC gets 0 points. Total score = 2. A score of 3 or less indicates non-operative management is recommended. A score of 4 is indeterminate, and 5 or more suggests operative intervention.

Question 19

A 55-year-old overweight female presents with medial foot pain and a progressive flatfoot deformity. On examination, she is unable to perform a single-leg heel rise on the affected side. Her hindfoot is in valgus, but the deformity is flexible and passively correctable. According to the Johnson and Strom classification for posterior tibial tendon dysfunction (PTTD), what stage does this represent?





Explanation

The patient has Stage II PTTD. Stage I is characterized by tenosynovitis with pain but no deformity, and a preserved single-leg heel rise. Stage II involves a flexible flatfoot deformity, and the patient is unable to perform a single-leg heel rise. Stage III is a rigid, fixed flatfoot deformity. Stage IV involves deltoid ligament compromise with ankle joint involvement (valgus tilt of the talus).

Question 20

A 30-year-old female presents with knee pain. Radiographs reveal an eccentric, lytic, expansile lesion in the distal femoral epiphysis extending to the articular surface without a sclerotic margin. Biopsy shows multinucleated giant cells uniformly distributed among mononuclear stromal cells. Which of the following targeted medical therapies acts by binding to RANKL and is FDA-approved for unresectable or recurrent cases of this tumor?





Explanation

The diagnosis is a Giant Cell Tumor (GCT) of bone. The mononuclear stromal cells in GCT express RANKL, which recruits and activates the osteoclast-like multinucleated giant cells responsible for the aggressive osteolysis. Denosumab is a monoclonal antibody that binds to RANKL, preventing osteoclast activation, and is highly effective in treating advanced or unresectable GCTs.

Question 21

An infant being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness is noted by the parents to have decreased spontaneous movement of the right leg. On examination, the infant has an absent active knee extension but intact sensation over the leg. Which of the following nerve palsies is the most likely cause?





Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, typically resulting from hyperflexion of the hips, which compresses the femoral nerve against the inguinal ligament. It manifests as decreased active quadriceps function (absent knee extension). The treatment is modifying the harness to decrease flexion or temporarily discontinuing it.

Question 22

A 14-year-old boy presents with severe bone pain in his right thigh. Radiographs reveal a diaphyseal lytic lesion with an 'onion skin' periosteal reaction. Biopsy confirms Ewing sarcoma. Which of the following chromosomal translocations is the classic genetic hallmark of this tumor?





Explanation

Ewing sarcoma is classically associated with the t(11;22)(q24;q12) translocation, which occurs in over 85% of cases and results in the EWS-FLI1 fusion protein. t(9;22) is seen in CML or mesenchymal chondrosarcoma; t(12;16) in myxoid liposarcoma; t(X;18) in synovial sarcoma; and t(2;13) in alveolar rhabdomyosarcoma.

Question 23

During a cruciate-retaining total knee arthroplasty (CR-TKA), the surgeon uses spacer blocks to check gap balancing. The extension gap is perfectly balanced, but the knee is significantly too tight in flexion. Which of the following is the most appropriate next step to balance the knee?





Explanation

If a knee is tight in flexion but balanced in extension, the flexion gap must be increased without affecting the extension gap. Options to specifically increase the flexion gap include downsizing the femoral component (which resects more posterior femoral condylar bone), increasing the posterior tibial slope, or recessing the PCL. Resecting more distal femur would inappropriately increase the extension gap.

Question 24

During an extensile ilioinguinal approach for a complex acetabular fracture, massive hemorrhage occurs while dissecting over the superior pubic ramus. This bleeding is most likely originating from the 'Corona Mortis'. This structure is classically an anastomosis between which two vascular systems?





Explanation

The Corona Mortis (Crown of Death) is a critical anatomical variant defined as a vascular anastomosis between the external iliac system (or inferior epigastric vessels) and the obturator vessels. It rests on the posterior aspect of the superior pubic ramus and is highly vulnerable during the ilioinguinal approach.

Question 25

A 25-year-old athlete undergoes a physical examination after a knee injury. The dial test demonstrates 15 degrees of increased external rotation of the tibia compared to the contralateral side when tested at 30 degrees of knee flexion. However, at 90 degrees of knee flexion, the external rotation is symmetric bilaterally. What is the most likely diagnosis?





Explanation

The dial test assesses tibial external rotation. Asymmetry of greater than 10 degrees at 30 degrees of flexion, which reduces to symmetry at 90 degrees of flexion, indicates an isolated posterolateral corner (PLC) injury. If the asymmetry persists or worsens at 90 degrees, it indicates a combined PLC and posterior cruciate ligament (PCL) injury.

Question 26

A 55-year-old manual laborer presents with advanced Stage III SLAC wrist (scapholunate advanced collapse). Radiographs show complete loss of articular cartilage on the proximal head of the capitate, as well as radioscaphoid arthritis. The radiolunate joint is preserved. What is the most appropriate surgical treatment?





Explanation

Stage III SLAC wrist involves arthritis of the radioscaphoid and capitolunate joints. Because the proximal capitate articular surface is diseased, a Proximal Row Carpectomy (PRC) is strictly contraindicated (as it relies on a healthy capitate head articulating with the lunate fossa). Therefore, scaphoid excision and four-corner fusion (capitate, hamate, lunate, triquetrum) is the procedure of choice.

Question 27

A patient sustains a traumatic spondylolisthesis of the axis (Hangman fracture) classified as Levine-Edwards Type IIA. What is the classic mechanism of injury, and what is the appropriate initial closed management?





Explanation

Type IIA Hangman fractures exhibit minimal translation but severe angulation and are caused by a flexion-distraction mechanism. Crucially, they worsen with traction (unlike standard Type II fractures). The correct initial management is gentle reduction via extension, followed by placement in a halo vest under slight compression.

Question 28

A 24-year-old male presents with midfoot pain after a twisting injury. AP radiographs demonstrate a small bony avulsion between the medial and middle cuneiforms, commonly referred to as the 'fleck sign'. The primary ligament avulsed in this injury connects which two osseous structures?





Explanation

The Lisfranc ligament is an interosseous ligament that runs from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is vital for midfoot stability. Its avulsion frequently produces the classic 'fleck sign' on radiographs.

Question 29

In a patient with a permanent high radial nerve palsy, a standard Boyes tendon transfer is planned. To restore thumb extension (extensor pollicis longus), which of the following muscles is most classically transferred?





Explanation

In standard tendon transfers for radial nerve palsy (e.g., Jones or Boyes), the Pronator Teres (PT) is transferred to the Extensor Carpi Radialis Brevis (ECRB) for wrist extension. For thumb extension, the Palmaris Longus (PL) is most commonly transferred to the Extensor Pollicis Longus (EPL). Finger extension is usually restored by transferring FCU or FDS to the EDC.

Question 30

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized in orthopaedic surgery for its potent osteoinductive properties. For which of the following scenarios is rhBMP-2 specifically FDA-approved?





Explanation

The FDA-approved indications for rhBMP-2 (Infuse) are highly specific: anterior lumbar interbody fusion (ALIF) using an LT-Cage, acute open tibial shaft fractures stabilized with an IM nail (within 14 days of injury), and certain maxillofacial/dental alveolar procedures. Anterior cervical fusion has a black-box warning due to potentially fatal soft tissue swelling.

Question 31

A 10-year-old boy presents with a unilateral slipped capital femoral epiphysis (SCFE). Which of the following patient profiles represents the strongest absolute indication for prophylactic percutaneous pinning of the contralateral, asymptomatic hip?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is universally recommended in patients with underlying endocrinopathies (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency) or prior pelvic radiation therapy, as their risk of bilateral involvement approaches 100%. While obesity and young age are risk factors, endocrine disorders are the strongest indication.

Question 32

A 35-year-old male sustains a severe bicondylar tibial plateau fracture. CT imaging reveals a large, displaced posteromedial coronal split fragment. Through which surgical interval is this specific fragment most safely and directly accessed for buttress plate fixation?





Explanation

The posteromedial approach to the proximal tibia is performed by developing the internervous/intermuscular interval between the medial head of the gastrocnemius (retracted posteriorly/laterally) and the pes anserinus tendons (semitendinosus, gracilis, sartorius - retracted anteriorly/medially). This provides excellent exposure of the posteromedial tibial plateau.

Question 33

A 62-year-old woman with a history of breast cancer presents with moderate thigh pain. Radiographs reveal a purely lytic lesion in the femoral diaphysis that occupies approximately half (1/2) of the bone diameter. Using Mirels' criteria, what is her score, and what is the recommended management?





Explanation

Mirels' criteria determine the risk of pathologic fracture. Site: Lower extremity (2 points). Pain: Moderate (2 points). Lesion: Lytic (3 points). Size: 1/3 to 2/3 of cortex (2 points). Total = 2 + 2 + 3 + 2 = 9. A score of 9 or greater indicates a high risk of fracture (>30%) and serves as an indication for prophylactic internal fixation.

Question 34

A 75-year-old male presents with neck pain after a ground-level fall. CT scan demonstrates a Type II odontoid fracture. Which of the following factors most significantly increases his risk of fracture nonunion if he is treated non-operatively with a rigid cervical collar?





Explanation

Risk factors for nonunion in Type II odontoid fractures include initial displacement > 5 mm, angulation > 10 degrees, advanced age (typically > 65 years), and delayed diagnosis. Initial displacement greater than 5 mm significantly reduces the chance of healing with external immobilization, often warranting surgical intervention (such as posterior C1-C2 fusion) if the patient can tolerate surgery.

Question 35

A surgeon incorrectly utilizes a stainless steel plate and secures it with titanium screws for a femur fracture. The patient subsequently develops implant failure and localized reaction due to corrosion. What specific type of corrosion has predominantly occurred?





Explanation

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within an electrolytic solution (like human body fluid). An electrochemical cell is created; the less noble metal (stainless steel) acts as the anode and corrodes, while the more noble metal (titanium) acts as the cathode.

Question 36

A 58-year-old male with poorly controlled diabetes mellitus presents with a swollen, warm, and erythematous left foot. X-rays show pronounced osteopenia, extensive periarticular bony fragmentation, subluxation of the tarsometatarsal joints, and debris. According to the Eichenholtz classification, what stage of Charcot arthropathy does this represent?





Explanation

The Eichenholtz classification stages Charcot arthropathy: Stage 0 (Inflammation without radiographic changes), Stage 1 (Development/Fragmentation: osteopenia, bony fragmentation, joint subluxation/dislocation, debris), Stage 2 (Coalescence: absorption of debris, early sclerosis, fusion of fragments), and Stage 3 (Reconstruction: rounding of bone ends, decreased sclerosis, permanent deformity). This patient's fragmentation and debris indicate Stage 1.

Question 37

A 45-year-old male who underwent a total hip arthroplasty with a ceramic-on-ceramic (CoC) bearing two years ago presents with a loud, audible 'squeaking' sound coming from his hip during certain movements. Which of the following is considered the primary risk factor for this squeaking?





Explanation

Squeaking in ceramic-on-ceramic (CoC) total hip arthroplasty is overwhelmingly associated with acetabular component malposition (e.g., excessively vertical or retroverted cup). This malposition leads to loss of the fluid lubrication film, edge loading of the femoral head against the ceramic rim, and subsequent 'stripe wear', which generates the acoustic squeak.

Question 38

A 30-year-old mechanic sustains a puncture wound to the volar aspect of his index finger and presents 48 hours later with suspected pyogenic flexor tenosynovitis. Which of the following physical examination findings is clinically considered the earliest and most sensitive of Kanavel's signs?





Explanation

Kanavel's four cardinal signs of pyogenic flexor tenosynovitis are: 1) flexed resting posture, 2) fusiform (sausage-like) swelling, 3) tenderness along the flexor tendon sheath, and 4) disproportionate pain with passive extension. Pain with passive extension is historically and clinically considered the earliest and most sensitive sign.

Question 39

A 22-year-old collegiate baseball pitcher is undergoing ulnar collateral ligament (UCL) reconstruction ('Tommy John' surgery) of the elbow. Which specific anatomical component of the UCL complex serves as the primary restraint to valgus stress at 90 degrees of elbow flexion?





Explanation

The Ulnar Collateral Ligament (UCL) complex consists of three components: the anterior bundle, the posterior bundle, and the transverse ligament. Biomechanical studies have proven that the anterior bundle is the primary restraint to valgus stress of the elbow throughout the functional range of motion, particularly at 90 degrees of flexion.

Question 40

A 45-year-old female sustains a coronal shear fracture of the distal humerus. Intraoperatively, the fracture is identified as a single contiguous osteochondral fragment that involves the entirety of the capitellum and the lateral half of the trochlea. Under the expanded Bryan and Morrey classification, what type of fracture is this?





Explanation

Coronal shear fractures of the distal humerus are classified by Bryan and Morrey: Type I (Hahn-Steinthal) is a large osseous capitellum fragment; Type II (Kocher-Lorenz) is an articular cartilage sleeve with minimal bone; Type III is comminuted. McKee added Type IV, which describes a single coronal shear fragment encompassing both the capitellum and the lateral aspect of the trochlea.

Question 41

A 55-year-old Asian man presents with progressive clumsiness in his hands and difficulty walking. Lateral cervical radiographs reveal continuous ossification along the posterior aspect of the vertebral bodies from C3 to C6. What is the most common systemic condition or radiographic finding associated with this pathology?





Explanation

The clinical picture describes Ossification of the Posterior Longitudinal Ligament (OPLL), which causes cervical myelopathy. OPLL is strongly associated with Diffuse Idiopathic Skeletal Hyperostosis (DISH), with up to 50% of patients with OPLL demonstrating radiographic evidence of DISH.

Question 42

A 32-year-old male sustains a high-energy trauma resulting in an ipsilateral displaced clavicle shaft fracture and a displaced extra-articular scapular neck fracture. According to Goss, what constitutes a 'double disruption' of the superior shoulder suspensory complex (SSSC) in this scenario?





Explanation

The Superior Shoulder Suspensory Complex (SSSC) is a bony and soft-tissue ring composed of the glenoid, coracoid, coracoclavicular ligaments, distal clavicle, acromioclavicular joint, and acromion. A 'floating shoulder' represents a double disruption of this complex, classically involving a fracture of the clavicular strut and a fracture of the scapular neck, which destabilizes the suspensory mechanism of the upper extremity.

Question 43

When comparing bearing surfaces in total hip arthroplasty, which of the following combinations demonstrates the lowest volumetric wear rate in laboratory simulations?





Explanation

Ceramic-on-ceramic bearings exhibit the lowest volumetric wear rates of all available bearing couples (less than 1 cubic millimeter per year). However, they carry unique risks such as squeaking and catastrophic component fracture.

Question 44

A 12-year-old obese male presents with a left-sided stable slipped capital femoral epiphysis (SCFE). Prophylactic in situ pinning of the asymptomatic right hip is most strongly indicated if the patient has a history of which of the following underlying conditions?





Explanation

Prophylactic pinning of the contralateral, unaffected hip in SCFE is controversial for idiopathic cases but is strongly indicated in patients with underlying endocrine or metabolic disorders (such as hypothyroidism, renal osteodystrophy, or panhypopituitarism) due to a very high risk (up to 100% in some series) of bilateral involvement.

Question 45

The anterior cruciate ligament (ACL) consists of two distinct bundles. Which of the following statements accurately describes the biomechanical behavior of these bundles during knee range of motion?





Explanation

The ACL is composed of the anteromedial (AM) and posterolateral (PL) bundles. Biomechanically, the AM bundle is tightest in flexion and primarily resists anterior tibial translation in this position. The PL bundle is tightest in extension and plays a primary role in resisting rotatory loads near full extension.

Question 46

A 28-year-old male presents with a slowly enlarging, painful mass near his knee joint. MRI shows a soft tissue mass adjacent to, but not within, the joint space. Biopsy reveals a biphasic pattern of epithelial and spindle cells. Which chromosomal translocation is highly diagnostic for this tumor?





Explanation

The clinical scenario and biphasic histology are characteristic of synovial sarcoma. The pathognomonic chromosomal abnormality for synovial sarcoma is the t(X;18)(p11;q11) translocation, which creates the SYT-SSX fusion gene.

Question 47

In the evaluation of a posterior wall acetabular fracture, which of the following methods has been shown to be the most accurate in assessing true hip instability to determine the need for operative fixation?





Explanation

While historically a posterior wall fragment size greater than 50% on CT was an absolute indication for surgery, Moed et al. demonstrated that CT measurements can overestimate or incorrectly predict instability. Dynamic fluoroscopic stress testing under anesthesia is the most accurate dynamic assessment for identifying true occult hip instability.

Question 48

A 45-year-old manual laborer presents with chronic wrist pain. Radiographs reveal a scaphoid nonunion with localized osteoarthritis strictly confined to the radial styloid and the distal pole of the scaphoid. The midcarpal joint is completely spared. What is the most appropriate surgical intervention?





Explanation

This patient has Scaphoid Nonunion Advanced Collapse (SNAC) Stage 1, characterized by arthritis limited to the radial styloid. The recommended treatment for Stage 1 is radial styloidectomy combined with scaphoid nonunion takedown, bone grafting, and internal fixation. Stages 2 and 3 involve more extensive carpal arthritis, requiring salvage procedures like proximal row carpectomy or four-corner fusion.

Question 49

The primary stabilizing ligament of the Lisfranc joint complex (the Lisfranc ligament) anatomically connects which two bones?





Explanation

The Lisfranc ligament is a strong interosseous ligament that runs obliquely from the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is critical for the stability of the tarsometatarsal joint complex.

Question 50

A 4-year-old girl is diagnosed with Langenskiöld stage III infantile Blount's disease. Her metaphyseal-diaphyseal angle (Drennan's angle) is 22 degrees, and clinical bowing is progressive. What is the most appropriate management?





Explanation

For infantile Blount's disease presenting at age 4 or older with Langenskiöld stage III or higher, bracing is generally ineffective and observation will lead to progressive deformity and physeal damage. Proximal tibial corrective osteotomy is the treatment of choice to restore mechanical alignment and relieve pathologic compression on the medial physis.

Question 51

A 24-year-old female sustains a flexion-distraction injury (Chance fracture) of the L2 vertebra after a motor vehicle collision in which she was wearing a lap-belt only. Which of the following associated injuries must be most aggressively ruled out?





Explanation

Chance fractures (flexion-distraction injuries) of the thoracolumbar spine are classically associated with lap-belt use. They carry a very high association (up to 40-50%) with intra-abdominal injuries, particularly hollow viscus injuries (e.g., small bowel perforations), which must be carefully ruled out.

Question 52

During a posterior-stabilized total knee arthroplasty, trial reduction reveals the knee is tight in flexion but well-balanced and stable in extension. What is the most appropriate surgical step to correct this mismatch?





Explanation

A knee that is tight in flexion but balanced in extension has an isolated narrow flexion gap. Downsizing the femoral component decreases the anteroposterior (AP) dimension of the femur, which selectively opens the flexion gap without altering the extension gap.

Question 53

The femoral footprint of the anterolateral (AL) bundle of the posterior cruciate ligament (PCL) is anatomically located in which area of the intercondylar notch?





Explanation

The PCL originates on the lateral aspect of the medial femoral condyle. Its anterolateral (AL) bundle is located shallower (more anteriorly toward the articular cartilage edge) and higher (more proximally/superiorly), whereas the posteromedial (PM) bundle is located deeper (more posteriorly) and inferiorly.

Question 54

Which of the following benign conditions carries the highest risk of undergoing malignant transformation into a secondary chondrosarcoma?





Explanation

Hereditary multiple exostoses (HME) is an autosomal dominant condition characterized by multiple osteochondromas. It carries an estimated 1% to 5% lifetime risk of malignant transformation into secondary chondrosarcoma. Growth of an osteochondroma after skeletal maturity or a cartilage cap thickness >1.5-2.0 cm is highly suspicious for malignant transformation.

Question 55

A Hoffa fracture is a coronal shear fracture of the distal femur. Which condyle is most commonly involved, and what is the typical mechanism of injury?





Explanation

Hoffa fractures (coronal plane fractures of the femoral condyle) predominantly involve the lateral condyle. The mechanism usually involves an axial load with an anterior-to-posterior force directed to the lateral condyle while the knee is in a flexed position (e.g., striking the dashboard in an MVA).

Question 56

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized in orthopedic surgery for its osteoinductive properties. Through which primary intracellular signaling molecules does rhBMP-2 directly transmit its signal to the nucleus to upregulate osteogenic genes?





Explanation

Bone morphogenetic proteins (BMPs) bind to cell-surface serine/threonine kinase receptors. This binding causes phosphorylation and activation of the receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. These complex with the common-mediator Smad 4 and translocate to the nucleus to activate the transcription of osteogenic genes like Runx2.

Question 57

The Salter innominate osteotomy is a surgical procedure used for the treatment of developmental dysplasia of the hip (DDH) to redirect the acetabulum and improve anterior and lateral coverage. Where is the functional hinge point of rotation for this specific osteotomy?





Explanation

The Salter osteotomy is a complete, single-cut trans-iliac osteotomy extending from the sciatic notch to the anterior inferior iliac spine (AIIS). The distal segment (acetabulum) is rotated anteriorly, laterally, and inferiorly, hinging on the symphysis pubis.

Question 58

In the Levine and Edwards classification of traumatic spondylolisthesis of the axis (Hangman's fracture), a Type IIA fracture is characterized by severe angulation with minimal translation. What is the pathomechanical mechanism of this injury and the appropriate non-operative treatment?





Explanation

A Type IIA Hangman's fracture results from a flexion-distraction injury, causing severe angulation but minimal translation. Because the primary injury involves disruption of the posterior longitudinal ligament and disc space in distraction, longitudinal traction is strictly contraindicated as it can cause over-distraction and catastrophic spinal cord injury. The treatment is closed reduction with mild compression and extension using a halo vest.

Question 59

In fully porous-coated cementless femoral stems used in total hip arthroplasty, rigid biologic fixation depends on bone ingrowth. What is the optimal pore size range for the porous coating to promote maximum osteoconduction and rigid fixation?





Explanation

The optimal pore size for reliable bone ingrowth in cementless arthroplasty components is strictly between 50 and 400 micrometers. Pores smaller than 50 micrometers typically result in fibrous tissue ingrowth rather than true bone, while pores larger than 400 micrometers can compromise the structural integrity of the coating and fail to provide adequate initial mechanical stability.

Question 60

A 62-year-old male with poorly controlled type 2 diabetes presents with a swollen, warm, and erythematous foot without ulceration. Radiographs show extensive periarticular fragmentation, debris, and subluxation of the tarsometatarsal joints. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent, and what is the primary initial treatment?





Explanation

The patient is presenting with Eichenholtz Stage 1 (Developmental/Fragmentation stage) Charcot arthropathy, characterized clinically by acute inflammation (erythema, warmth, swelling) and radiographically by osteopenia, bony fragmentation, and joint subluxation/dislocation. The gold standard initial treatment is strict immobilization and offloading using a total contact cast (TCC) to prevent further deformity until the acute inflammatory phase resolves and bone consolidation begins.

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