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Orthopedics Hyperguide Review | Dr Hutaif General Ortho -...

23 Apr 2026 53 min read 124 Views
Orthopedic MCqs

Key Takeaway

This interactive board review contains 100 randomly selected orthopedic surgery questions with clinical images, immediate feedback, and detailed references.

Orthopedics Hyperguide Review | Dr Hutaif General Ortho -...

Comprehensive 100-Question Exam


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Question 1

A 35-year-old male smoker presents 6 months after a closed tibial shaft fracture treated initially with a cast. Radiographs demonstrate a hypertrophic nonunion with an 'elephant foot' appearance. What is the primary underlying cause of this specific type of nonunion and the ideal treatment strategy?





Explanation

Hypertrophic nonunions ('elephant foot' or 'horse hoof') are primarily caused by mechanical instability in the presence of adequate biological healing potential (good blood supply and callus formation). The definitive treatment is to provide rigid mechanical stability, usually through intramedullary nailing or compression plating, which allows the abundant callus to consolidate. Bone grafting is typically unnecessary because the biological potential is already robust.

Question 2

Which of the following genetic alterations is most closely associated with a markedly increased risk of developing both osteosarcoma and bilateral retinoblastoma?





Explanation

The RB1 (retinoblastoma) gene is a tumor suppressor gene. Inactivation or loss of heterozygosity of RB1 is the hallmark of hereditary retinoblastoma. Patients with this mutation have a significantly increased risk (often 500-fold) of developing secondary primary malignancies, most notably osteosarcoma. EWS-FLI1 is associated with Ewing sarcoma, MDM2 with low-grade central osteosarcoma and parosteal osteosarcoma, GNAS with fibrous dysplasia, and APC with familial adenomatous polyposis and Gardner syndrome.

Question 3

A 3-month-old infant is currently being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the routine weekly follow-up, the infant is noted to have an absence of active knee extension on the treated side. What is the most likely cause of this physical finding?





Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, usually caused by excessive hip flexion (typically >120 degrees). It presents as decreased or absent active knee extension. The harness must be adjusted to reduce flexion or temporarily discontinued if the palsy persists. Excessive abduction in a Pavlik harness is associated with an increased risk of avascular necrosis (AVN) of the femoral head.

Question 4

A 45-year-old male is brought into the trauma bay after a severe motorcycle crash. A pelvic binder is applied, and radiographs demonstrate an anteroposterior compression (APC) type III pelvic ring injury. He remains hemodynamically unstable despite receiving 2 units of packed red blood cells. The Focused Assessment with Sonography for Trauma (FAST) exam is negative. What is the most appropriate immediate orthopedic intervention to address his pelvic hemorrhage?





Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic fracture (APC III) and a negative FAST (ruling out massive intra-abdominal hemorrhage), the source of bleeding is presumed to be the pelvis (venous plexus or arterial). Once pelvic volume is reduced (via binder), the next algorithmic step for persistent hemodynamic instability is either preperitoneal pelvic packing (PPP) or pelvic angiography with embolization, depending on institutional protocols and immediate availability.

Question 5

In the biomechanics of metal-on-polyethylene total hip arthroplasty, which of the following wear mechanisms is primarily responsible for the generation of submicron polyethylene debris that ultimately leads to macrophage activation and periprosthetic osteolysis?





Explanation

Adhesive wear is the primary mechanism of polyethylene wear in total hip arthroplasty. It occurs when two articulating surfaces come into contact, causing micro-adhesions to form. As the surfaces slide against each other, these micro-adhesions break off, generating millions of submicron polyethylene particles. These specific sized particles (0.1 to 1.0 micrometers) are readily phagocytosed by macrophages, inciting a cytokine cascade (TNF-alpha, IL-1, IL-6) that stimulates osteoclasts and causes osteolysis.

Question 6

A 65-year-old male presents with difficulty buttoning his shirt, deteriorating handwriting, and frequent tripping. Physical examination reveals a positive Hoffman's sign and an inverted brachioradialis reflex. An inverted brachioradialis reflex specifically indicates spinal cord compression at which of the following levels?





Explanation

An inverted brachioradialis reflex is characterized by an absent or diminished brachioradialis reflex with simultaneous hyperactive finger flexion. It is a highly specific upper motor neuron sign for cervical myelopathy localizing to the C5-C6 spinal level. Compression at this level disrupts the lower motor neurons for the C6 reflex arc (diminished BR reflex) while exhibiting upper motor neuron disinhibition of the C8 reflex arc (hyperactive finger flexors).

Question 7

When evaluating graft choices for anterior cruciate ligament (ACL) reconstruction, how do the biomechanical properties of a 10mm bone-patellar tendon-bone (BPTB) autograft compare to those of the native intact ACL?





Explanation

A 10mm bone-patellar tendon-bone (BPTB) autograft is biomechanically stronger and stiffer than the native ACL. The native ACL has an ultimate load to failure of approximately 2160 N and a stiffness of 242 N/mm. A 10mm BPTB graft has an ultimate load to failure of approximately 2977 N and a stiffness of 620 N/mm. Therefore, it has both higher ultimate load to failure and higher stiffness than the native ACL.

Question 8

Following a Zone II flexor tendon repair, preventing adhesions while protecting the integrity of the repair is paramount. Which of the following rehabilitation protocols utilizes early true active flexion to achieve this?





Explanation

The Indiana (or Strickland) protocol is an early active motion protocol for flexor tendon repairs. It utilizes a tenodesis splint that allows the wrist to hinge into slight extension, facilitating early active flexion of the fingers to decrease tendon gliding resistance and prevent adhesions. The Kleinert protocol uses active extension with rubber band-assisted passive flexion. The Duran protocol focuses strictly on passive flexion and extension.

Question 9

A 55-year-old male with poorly controlled type II diabetes presents with a unilaterally swollen, warm, and erythematous foot without ulceration. Radiographs show periarticular fragmentation, bony debris, and early subluxation of the midfoot joints, but no significant sclerosis or consolidation. According to the Eichenholtz classification, what is the stage and the most appropriate initial management?





Explanation

The patient is presenting with acute Charcot arthropathy. The clinical and radiographic findings of fragmentation, debris, and subluxation characterize Eichenholtz Stage 1 (Developmental/Fragmentation stage). Stage 0 (prodromal) has clinical swelling but normal radiographs. Stage 2 (Coalescence) shows early healing and sclerosis. Stage 3 (Reconstruction) shows consolidation and remodeling. The gold standard initial treatment for acute Stage 1 Charcot is immobilization with a total contact cast (TCC) to prevent further deformity until the acute inflammatory phase resolves.

Question 10

Within the microanatomy of articular cartilage, which zone possesses the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils that are oriented perpendicular to the joint surface?





Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans and the lowest concentration of water. The collagen fibrils (Type II) in this zone are large in diameter and oriented strictly perpendicular to the joint surface to resist compressive loads. Conversely, the superficial zone has the highest water content, lowest proteoglycan content, and collagen fibrils oriented parallel to the joint surface to resist shear forces.

Question 11

Which of the following clinical scenarios serves as the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a patient who presents with a unilateral slipped capital femoral epiphysis (SCFE)?





Explanation

Prophylactic pinning of the contralateral hip in unilateral SCFE is highly recommended in patients with specific risk factors that predispose them to bilateral involvement. The strongest indications include an underlying endocrine disorder (e.g., hypothyroidism, panhypopituitarism, renal osteodystrophy), previous pelvic radiation, and very young age at presentation (typically < 10 years for boys and < 9 for girls). Endocrine disorders carry an extremely high risk of bilateral SCFE, justifying prophylactic fixation.

Question 12

A 42-year-old male sustains a high-energy trauma to his right knee. Radiographs demonstrate a bicondylar tibial plateau fracture with dissociation of the metaphysis from the diaphysis. What is the correct Schatzker classification for this fracture, and what is the most critical associated soft tissue emergency?





Explanation

A bicondylar tibial plateau fracture with metaphyseal-diaphyseal dissociation is classified as a Schatzker VI fracture. Because of the high-energy nature of this injury, severe soft-tissue compromise is the rule rather than the exception. The most critical and immediate limb-threatening complication is acute compartment syndrome, which occurs in a significant percentage of Schatzker VI fractures and requires high clinical suspicion and potential four-compartment fasciotomy.

Question 13

Denosumab has revolutionized the medical management of unresectable or locally advanced Giant Cell Tumors of bone. What is the specific cellular mechanism of action of this monoclonal antibody?





Explanation

Giant Cell Tumor (GCT) of bone consists of neoplastic mononuclear stromal cells that express high levels of RANK Ligand (RANKL), which recruits and activates normal multinucleated giant cells (osteoclasts) that cause the massive bone destruction seen in the tumor. Denosumab is a fully human monoclonal antibody that binds directly to RANKL, preventing it from binding to the RANK receptor on osteoclast precursors. This effectively halts osteoclast activation and bone destruction.

Question 14

In a posterior-stabilized (PS) total knee arthroplasty, the posterior cruciate ligament (PCL) is resected. What is the primary biomechanical function of the implanted cam-and-post mechanism during knee flexion?





Explanation

In a native knee, the posterior cruciate ligament (PCL) is responsible for posterior femoral rollback during deep knee flexion, which clears the posterior femur from impinging on the posterior tibia and allows for high flexion angles. When the PCL is excised in a PS total knee arthroplasty, the interaction between the tibial post and the femoral cam engages in mid-to-deep flexion to mechanically force the femur posteriorly, recreating femoral rollback and enabling deep flexion.

Question 15

A 15-year-old female gymnast complains of an insidious onset of lower back pain, exacerbated by extension. Radiographs confirm an L5-S1 isthmic spondylolisthesis (Meyerding Grade II). Which of the following classic radiographic findings is specifically associated with the defect causing this condition?





Explanation

Isthmic spondylolisthesis is most commonly caused by a pars interarticularis defect (spondylolysis), typically at L5. On oblique lumbar radiographs, the posterior elements of the vertebra resemble a 'Scotty dog'. A defect or fracture in the pars interarticularis appears as a radiolucent line across the neck of the dog, often described as a 'Scotty dog with a collar'. Dysplastic spondylolisthesis features an elongated pars, and degenerative spondylolisthesis is often associated with sagittally oriented facets or a facet fluid sign.

Question 16

In a patient presenting with classic symptoms of Carpal Tunnel Syndrome, electromyography (EMG) and nerve conduction studies (NCS) are ordered for confirmation and severity staging. Which of the following electrodiagnostic findings is typically the earliest indicator of median nerve compression at the wrist?





Explanation

Nerve conduction studies detect demyelination early in the disease process. The sensory fibers are typically affected before the motor fibers in compressive neuropathies like Carpal Tunnel Syndrome. Therefore, an increased sensory distal latency (which corresponds to a decreased sensory nerve conduction velocity) is the earliest detectable electrodiagnostic abnormality. Motor latencies increase later, and amplitude changes or fibrillations (EMG findings) indicate advanced disease with axonal loss.

Question 17

In the principles of orthopedic internal fixation, the pull-out strength of a cortical bone screw is most significantly and directly proportional to which of the following screw characteristics?





Explanation

The pull-out strength of a bone screw is a measure of its resistance to being pulled out of the bone axially. The primary formula for pull-out strength incorporates the shear strength of the bone, the length of thread engagement, and the outer diameter of the screw. Therefore, increasing the outer diameter directly and linearly increases the pull-out strength. The core diameter determines the bending strength of the screw, not the pull-out strength.

Question 18

A 50-year-old male sustains a traumatic anterior shoulder dislocation. After reduction, he continues to have severe anterior shoulder pain and significant weakness in internal rotation. Examination demonstrates a positive lift-off test. Given this specific injury pattern, which adjacent structure is at the highest risk for subluxation or instability?





Explanation

The patient has a traumatic subscapularis tear, indicated by weakness in internal rotation and a positive lift-off test. The subscapularis tendon insertion forms the medial wall of the bicipital groove and, together with the coracohumeral ligament, creates the biceps pulley. A tear of the upper border of the subscapularis profoundly destabilizes this pulley system, allowing the long head of the biceps tendon (LHBT) to subluxate or dislocate medially.

Question 19

During a volar fasciotomy for acute forearm compartment syndrome, releasing all fascial compartments is imperative. Which of the following structures is contained within the 'mobile wad of Henry', representing a specific compartment that must be addressed?





Explanation

The 'mobile wad of Henry' is an anatomic muscle group in the lateral aspect of the forearm consisting of three muscles: the brachioradialis, the extensor carpi radialis longus (ECRL), and the extensor carpi radialis brevis (ECRB). In the setting of forearm compartment syndrome, it is considered a separate functional compartment (along with the volar and dorsal compartments) that requires specific evaluation and potential fascial release.

Question 20

A 45-year-old female presents with a painful bunion. Weight-bearing radiographs reveal a Hallux Valgus Angle (HVA) of 42 degrees and an Intermetatarsal Angle (IMA) of 18 degrees. Clinical examination reveals no hypermobility at the first tarsometatarsal (TMT) joint. What is the most appropriate surgical intervention for this deformity?





Explanation

This patient has a severe hallux valgus deformity, defined by an HVA > 40 degrees and an IMA > 15 degrees. Distal osteotomies (like the Chevron) cannot achieve enough translation to correct an IMA > 15 degrees. For severe deformities without TMT hypermobility or degenerative arthritis, a proximal metatarsal osteotomy (e.g., Ludloff, proximal crescentic) combined with a distal soft tissue release (modified McBride) is the most appropriate procedure. A Lapidus is favored if there is documented TMT hypermobility or arthritis.

Question 21

Which recombinant human bone morphogenetic protein (rhBMP) is FDA-approved for use as an adjunct in acute open tibial shaft fractures treated with an intramedullary nail?





Explanation

rhBMP-2 (Infuse) is FDA-approved for the treatment of acute open tibial shaft fractures stabilized with intramedullary nailing, as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 (OP-1) was previously approved under a humanitarian device exemption for recalcitrant tibial nonunions.

Question 22

In which zone of mature articular cartilage are the collagen fibers oriented perpendicular to the joint surface and the proteoglycan concentration highest?





Explanation

The deep (radial) zone of articular cartilage contains collagen fibers that are oriented perpendicular to the articular surface. This zone provides the greatest resistance to compressive forces because it contains the highest concentration of proteoglycans and the lowest concentration of water.

Question 23

According to the Young-Burgess classification, an Anteroposterior Compression Type III (APC III) pelvic ring injury represents complete disruption of the symphysis pubis and which of the following posterior ligamentous complexes?





Explanation

An APC III injury implies a complete anterior and posterior disruption of the hemipelvis. This includes the symphysis pubis anteriorly, and the anterior SI, posterior SI, sacrotuberous, and sacrospinous ligaments posteriorly, resulting in a completely unstable hemipelvis.

Question 24

The primary blood supply to the adult femoral head is derived from the medial circumflex femoral artery (MCFA). Which specific branch of the MCFA is the main contributor to the weight-bearing dome?





Explanation

The lateral epiphyseal artery, a terminal branch of the medial circumflex femoral artery (MCFA), provides the vast majority of the blood supply to the weight-bearing dome of the adult femoral head.

Question 25

Prophylactic in situ pinning of the asymptomatic contralateral hip in a patient with a slipped capital femoral epiphysis (SCFE) is most strongly indicated in a patient with which of the following underlying conditions?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is indicated for patients with a high risk of subsequent bilateral slip. Endocrine and metabolic disorders, such as renal osteodystrophy, hypothyroidism, and prior pelvic radiation, are strong indications for prophylactic fixation due to the high incidence of bilaterality.

Question 26

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The parents note that the infant has stopped kicking her right leg and appears unable to actively extend her right knee. What is the most likely cause?





Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by hyperflexion of the hips compressing the nerve against the rim of the pelvis. It presents with decreased active knee extension. Treatment involves adjusting the anterior straps to decrease hip flexion, which usually leads to spontaneous recovery.

Question 27

During a total knee arthroplasty for a severe varus deformity, the knee is found to be tight medially in both flexion and extension. After releasing the deep medial collateral ligament (MCL), what is the next appropriate step in the medial soft tissue release sequence?





Explanation

In a varus knee, the standard sequential medial release to balance both the flexion and extension gaps starts with osteophyte removal and deep MCL release. If the knee remains tight in both flexion and extension, the next structure released is the posteromedial corner and capsule, followed by the superficial MCL, and finally the pes anserinus if further balancing is required.

Question 28

Following an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BPTB) autograft, at what time point postoperative is the graft substance structurally at its weakest mechanics due to remodeling?





Explanation

The autograft undergoes a process of necrosis, revascularization, and remodeling (ligamentization). During the 6-12 week postoperative window, the graft substance undergoes significant cellular repopulation and collagen remodeling, making it mechanically at its weakest point and most vulnerable to elongation or rupture.

Question 29

A 65-year-old man presents with bilateral leg pain that worsens with walking and prolonged standing. Which of the following physical examination findings or clinical tests best differentiates neurogenic claudication from vascular claudication?





Explanation

The bicycle test helps differentiate neurogenic from vascular claudication. Patients with neurogenic claudication (lumbar spinal stenosis) experience relief when flexed forward, opening the spinal canal and neuroforamina, allowing them to pedal indefinitely. Those with vascular claudication experience ischemic pain related to muscle exertion regardless of posture.

Question 30

Which of the following scenarios best describes the mechanism of primary bone healing (direct bone healing)?





Explanation

Primary (direct) bone healing occurs with absolute stability (e.g., rigid compression plating) and anatomic reduction. It bypasses soft callus formation entirely. Osteoclasts create cutting cones that cross the fracture line, followed by osteoblasts laying down lamellar bone directly via intramembranous ossification.

Question 31

A 14-year-old boy presents with knee pain. Radiographs show a sunburst periosteal reaction in the distal femur. Biopsy confirms osteosarcoma. Mutations in which two tumor suppressor genes are most commonly associated with the pathogenesis of this tumor?





Explanation

Osteosarcoma is strongly associated with mutations in the retinoblastoma (Rb) gene (as seen in hereditary retinoblastoma) and the p53 gene (as seen in Li-Fraumeni syndrome). Both are critical tumor suppressor genes that regulate the cell cycle.

Question 32

A 25-year-old athlete sustains a midfoot injury. Radiographs reveal a 'fleck sign.' The ligament whose avulsion creates this radiographic finding originates on which bone and inserts onto which bone?





Explanation

The Lisfranc ligament is an interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. A 'fleck sign' represents a bony avulsion of this ligament, usually from the base of the 2nd metatarsal, and indicates a severe Lisfranc injury.

Question 33

A 32-year-old man sustains a closed tibial shaft fracture. His blood pressure is 140/80 mmHg. What is the highest absolute intracompartmental pressure at which surgical fasciotomy is NOT yet strictly indicated based on the delta P concept?





Explanation

The delta P is defined as the diastolic blood pressure minus the compartment pressure. A delta P of less than or equal to 30 mmHg is the classic indication for fasciotomy. With a diastolic BP of 80 mmHg, a compartment pressure of 50 mmHg would give a delta P of 30 mmHg. Therefore, 45 mmHg (Delta P = 35 mmHg) is the highest pressure listed where fasciotomy is not yet strictly indicated by the delta P rule.

Question 34

In severe carpal tunnel syndrome, sensation over the thenar eminence is typically spared. This occurs because the palmar cutaneous branch of the median nerve arises at which anatomical location?





Explanation

The palmar cutaneous branch of the median nerve arises approximately 5 to 6 cm proximal to the transverse carpal ligament and travels superficial to the flexor retinaculum between the flexor carpi radialis (FCR) and palmaris longus tendons to supply sensation to the base of the palm (thenar eminence). Thus, it escapes compression in carpal tunnel syndrome.

Question 35

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within an electrolytic environment. Which of the following combinations of orthopedic implants is most likely to undergo severe galvanic corrosion and is strictly contraindicated?





Explanation

Mixing 316L stainless steel and titanium alloy creates a strong galvanic cell due to their disparate positions on the anodic/cathodic index. Titanium is highly noble (cathodic) and stainless steel is relatively anodic, leading to rapid, severe corrosion of the stainless steel.

Question 36

A 22-year-old baseball pitcher presents with vague anterior shoulder pain. An MRI arthrogram reveals a SLAP tear. Which type of SLAP lesion involves detachment of both the superior labrum and the origin of the long head of the biceps tendon from the supraglenoid tubercle?





Explanation

Type II SLAP tears are characterized by the detachment of the superior labrum and the long head of the biceps anchor from the supraglenoid tubercle. Type I is degenerative fraying; Type III is a bucket-handle tear with an intact biceps anchor; Type IV is a bucket-handle tear extending into the biceps tendon.

Question 37

Following a displaced distal radius fracture, the lateral radiograph reveals that the lunate is tilted dorsally relative to the radius, and the scaphoid is flexed volarly. The scapholunate angle is measured at 75 degrees. Which of the following carpal instability patterns does this represent?





Explanation

A scapholunate angle > 60 degrees (typically > 70 in frank pathology) with the lunate extended (tilted dorsally) relative to the radius and the scaphoid flexed (tilted volarly) is the hallmark of Dorsal Intercalated Segment Instability (DISI), commonly resulting from scapholunate ligament disruption.

Question 38

In the Ponseti method for the treatment of congenital talipes equinovarus (clubfoot), what is the correct sequence of correction of the deformities?





Explanation

The mnemonic CAVE dictates the rigid sequence of correction in the Ponseti method: Cavus (corrected first by elevating the first ray), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy to fully correct).

Question 39

A 70-year-old woman undergoes a primary total hip arthroplasty via a posterior approach. Postoperatively, she has a profound foot drop and absent sensation over the anterolateral leg and dorsum of the foot. Plantar flexion and foot inversion are completely intact. Which specific nerve branch was most likely injured?





Explanation

The sciatic nerve has two distinct divisions. The common peroneal (fibular) division is lateral and more firmly tethered, making it significantly more susceptible to stretch or retractor injury during hip surgery. Injury results in foot drop (weak dorsiflexion/eversion) and sensory loss on the foot dorsum. Intact plantar flexion and inversion indicate the tibial division is spared.

Question 40

The 'fallen leaf' (or 'fallen fragment') sign on a plain radiograph is virtually pathognomonic for which of the following benign bone lesions?





Explanation

The 'fallen leaf' sign occurs when a portion of the cortical bone fractures and falls into the fluid-filled cavity of a Unicameral (simple) bone cyst. Because it is a single fluid-filled cavity lacking internal septations or solid tissue, the bone fragment settles at the dependent portion of the cyst, which is pathognomonic for a UBC.

Question 41

The pullout strength of a pedicle screw is most significantly increased by increasing which of the following screw parameters?





Explanation

Pullout strength is determined by the formula: F = S * L * pi * D, where S is the shear strength of the bone, L is the length of thread engagement, and D is the outer (thread) diameter. Thus, increasing the outer diameter has the most profound effect on increasing pullout strength.

Question 42

A 65-year-old man with Paget's disease of bone is started on alendronate. Which of the following describes the primary cellular mechanism of action of this medication?





Explanation

Nitrogen-containing bisphosphonates (like alendronate) inhibit farnesyl pyrophosphate (FPP) synthase in the mevalonate pathway. This disrupts osteoclast intracellular signaling, impairs their ruffled border formation, and induces osteoclast apoptosis.

Question 43

A 6-week-old female infant is brought in for a screening hip ultrasound due to breech presentation. Which of the following ultrasound findings indicates a normal, mature hip?





Explanation

According to Graf's classification of developmental dysplasia of the hip (DDH), a normal Type I hip has an alpha angle greater than 60 degrees and a beta angle less than 55 degrees.

Question 44

In a hemodynamically unstable patient with an anteroposterior compression (APC) type III pelvic ring injury, at which precise anatomical landmark should a pelvic binder be applied to optimally reduce pelvic volume?





Explanation

A pelvic circumferential compression device (binder or sheet) must be placed at the level of the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is incorrect and can act as a fulcrum to worsen pelvic displacement.

Question 45

A 32-year-old woman presents with knee pain. Radiographs reveal an eccentric, lytic epiphyseal lesion of the distal femur. Biopsy confirms Giant Cell Tumor of bone. Which of the following represents the neoplastic cell population and its characteristic mutation?





Explanation

In Giant Cell Tumor (GCT) of bone, the true neoplastic cells are the mononuclear spindle-like stromal cells, not the multinucleated giant cells (which are reactive osteoclasts). The neoplastic mononuclear cells characteristically harbor a mutation in the H3F3A gene and express RANKL to recruit the giant cells.

Question 46

A 2-year-old boy presents with a 2-day history of refusal to bear weight on his right leg, a fever of 38.5°C, and an ESR of 55 mm/hr. Joint aspiration yields purulent fluid. Culturing the fluid on traditional solid agar fails to grow organisms, but growth is observed in liquid BACTEC blood culture bottles. What is the most likely pathogen?





Explanation

Kingella kingae is a fastidious Gram-negative organism that is increasingly recognized as a leading cause of septic arthritis in children aged 6 months to 4 years. It is difficult to grow on standard solid media and requires inoculation into liquid blood culture vials (e.g., BACTEC) for optimal detection.

Question 47

Which of the following structural zones of articular cartilage contains the highest concentration of water and predominantly parallel-aligned collagen fibers?





Explanation

The superficial (tangential) zone of articular cartilage contains the highest water content (approx. 80%), the lowest proteoglycan content, and densely packed collagen fibers aligned parallel to the joint surface to resist shear forces.

Question 48

During reconstruction of the anterior cruciate ligament (ACL), the surgeon must be aware of the native ligament's vascular supply to optimize graft incorporation. The primary blood supply to the native ACL arises from which vessel?





Explanation

The primary blood supply to the ACL is the middle genicular artery, which branches from the popliteal artery and pierces the posterior joint capsule to supply the cruciate ligaments.

Question 49

A 24-year-old male is brought to the ED after a motorcycle collision. He has flaccid paralysis below the C6 level, a blood pressure of 80/50 mmHg, and a heart rate of 52 bpm. His extremities are warm and well-perfused. Which of the following is the primary mechanism for his hemodynamic instability?





Explanation

The patient is exhibiting neurogenic shock, characterized by hypotension and bradycardia. This occurs due to the loss of descending sympathetic tone in high spinal cord injuries (above T6), leading to unchecked parasympathetic (vagal) activity, peripheral vasodilation, and warm extremities.

Question 50

A 28-year-old carpenter sustains a laceration to his volar index finger at the level of the proximal phalanx, transecting both the FDS and FDP tendons. This injury falls into which flexor tendon zone?





Explanation

Zone II (historically called 'no man's land') extends from the proximal edge of the A1 pulley to the insertion of the Flexor Digitorum Superficialis (FDS). Injuries here involve both FDS and FDP within the tight fibro-osseous sheath, complicating repair and rehabilitation.

Question 51

The pathophysiology of acute compartment syndrome involves an initial cascade leading to tissue ischemia. Which of the following best describes the critical initiating hemodynamic event?





Explanation

Acute compartment syndrome begins with an increase in tissue pressure that eventually exceeds venous pressure, leading to venous outflow obstruction (venous hypertension). This decreases the local arteriovenous (AV) gradient, leading to diminished capillary perfusion and subsequent cellular ischemia.

Question 52

During the proliferative phase of secondary fracture healing, the differentiation of mesenchymal stem cells into chondrocytes to form a soft callus is primarily driven by which environmental factor?





Explanation

Secondary fracture healing occurs via endochondral ossification, which is driven by an environment of relative hypoxia and higher mechanical strain. Hypoxia induces Hypoxia-Inducible Factor 1-alpha (HIF-1a), which promotes chondrogenesis and angiogenesis.

Question 53

A 55-year-old male with a metal-on-metal total hip arthroplasty presents with groin pain and a large cystic mass. Aspiration yields cloudy, non-purulent fluid with a negative culture. Tissue biopsy shows a dense perivascular infiltrate of lymphocytes. What type of hypersensitivity reaction is occurring?





Explanation

Adverse local tissue reactions (ALTR) or Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL) in metal-on-metal implants are characterized by a delayed, T-cell mediated Type IV hypersensitivity reaction to metal wear debris (specifically cobalt and chromium ions).

Question 54

A 12-year-old boy with a BMI of 35 is diagnosed with a unilateral slipped capital femoral epiphysis (SCFE). Which of the following is an accepted indication for prophylactic in situ pinning of the contralateral, asymptomatic hip?





Explanation

Prophylactic pinning of the contralateral hip in SCFE is indicated in patients with underlying metabolic or endocrine disorders (e.g., renal osteodystrophy, hypothyroidism, panhypopituitarism) due to the exceedingly high risk of bilateral progression.

Question 55

Guyon's canal serves as the passageway for the ulnar nerve and artery into the hand. What structure forms the floor of this canal?





Explanation

The floor of Guyon's canal is formed by the transverse carpal ligament (flexor retinaculum) and the pisohamate ligament. The roof is the volar carpal ligament. The medial border is the pisiform, and the lateral border is the hook of the hamate.

Question 56

In the use of bone graft materials, demineralized bone matrix (DBM) possesses which of the following biological properties?





Explanation

Demineralized bone matrix (DBM) provides a collagenous scaffold for new bone growth (osteoconductive) and contains bone morphogenetic proteins (BMPs) that stimulate the differentiation of osteoprogenitor cells (osteoinductive). It lacks live viable cells, so it is not osteogenic.

Question 57

A 40-year-old weekend warrior sustains an acute Achilles tendon rupture. The tear occurs in the typical 'watershed' region. This area of relative hypovascularity is located approximately how far proximal to the calcaneal insertion?





Explanation

The 'watershed' area of the Achilles tendon, which is most susceptible to rupture due to decreased vascularity, is located approximately 2 to 6 cm proximal to its insertion on the calcaneus.

Question 58

Polymethylmethacrylate (PMMA) bone cement is commonly used in total joint arthroplasty. The addition of barium sulfate to PMMA serves what specific purpose?





Explanation

Barium sulfate (or zirconium dioxide) is added to PMMA to act as a radiopacifier, allowing the cement mantle to be visualized on postoperative radiographs. Its addition actually slightly decreases the mechanical strength of the cement.

Question 59

A 68-year-old man presents with diffuse bone pain and a pathological fracture of the proximal humerus. Laboratory testing shows anemia, hypercalcemia, and a monoclonal spike on serum protein electrophoresis. Which of the following imaging modalities is notoriously insensitive for detecting the skeletal lesions associated with this condition?





Explanation

The patient has multiple myeloma. The lytic lesions of multiple myeloma are characterized by pure osteoclastic overactivity with virtually no osteoblastic response. Therefore, a Technetium-99m bone scan (which relies on osteoblastic activity) is typically 'cold' or falsely negative.

Question 60

During an arthroscopic Bankart repair, the surgeon places a suture anchor at the 5 o'clock position on the anterior glenoid rim. Which nerve is most at risk of injury if the drill penetrates too deeply at this location?





Explanation

The axillary nerve courses directly inferior and anterior to the shoulder joint capsule. It is located closest to the inferior glenoid rim (near the 6 o'clock position), making it highly vulnerable during anteroinferior anchor placement (e.g., 5 o'clock position) for a Bankart repair.

Question 61

A 24-year-old male presents with a slowly enlarging, painless mass around his knee joint. MRI shows a soft tissue mass adjacent to, but not within, the joint space. Biopsy reveals a biphasic pattern of spindle and epithelial cells. Which specific chromosomal translocation is characteristic of this pathology?





Explanation

Synovial sarcoma is characterized by the t(X;18) translocation, which leads to the SYT-SSX fusion gene. It commonly presents in young adults as an extra-articular soft tissue mass near a large joint.

Question 62

During bone healing, various bone morphogenetic proteins (BMPs) play crucial roles in osteoinduction. Which of the following recombinant human BMPs is currently FDA-approved for use in acute, open tibial shaft fractures treated with an intramedullary nail?





Explanation

rhBMP-2 is FDA-approved for acute, open tibial shaft fractures and anterior lumbar interbody fusion (ALIF). While rhBMP-7 (OP-1) was previously used for long bone nonunions, rhBMP-2 is the correct indication for acute open tibias.

Question 63

A 2-week-old infant is brought to the clinic for management of congenital idiopathic clubfoot (talipes equinovarus) using the Ponseti method. What is the correct sequence of deformity correction during the casting process?





Explanation

The Ponseti method corrects clubfoot deformities in the specific order of the acronym CAVE: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by elevating the first ray.

Question 64

A 45-year-old female presents with numbness and tingling in her thumb, index, and long fingers. Examination reveals weakness in thumb opposition but normal sensation over the thenar eminence. Which of the following anatomical structures is most directly responsible for the preservation of her thenar sensation?





Explanation

The palmar cutaneous branch of the median nerve branches off proximal to the carpal tunnel and travels superficial to the transverse carpal ligament. Therefore, it is spared in carpal tunnel syndrome, preserving sensation over the thenar eminence.

Question 65

A major advantage of using titanium alloy (Ti-6Al-4V) over cobalt-chromium (Co-Cr) for the femoral stem in cementless total hip arthroplasty is related to its mechanical properties. Which of the following best describes this advantage?





Explanation

Titanium alloy has a lower modulus of elasticity (closer to that of cortical bone) compared to cobalt-chromium. This decreases the stiffness mismatch between the implant and bone, significantly minimizing stress shielding.

Question 66

A 65-year-old male is involved in a high-speed motor vehicle collision and sustains a burst fracture of L1 with retropulsion of bone fragments occupying 50% of the spinal canal. He has isolated weakness in his bilateral extensor hallucis longus (EHL). Which of the following nerve root levels is most likely compromised?





Explanation

The extensor hallucis longus (EHL) is primarily innervated by the L5 nerve root. Impairment of great toe extension strongly indicates an L5 neurologic deficit.

Question 67

A 60-year-old female presents with chronic shoulder pain and inability to actively elevate her arm above 60 degrees. Radiographs show superior migration of the humeral head and an acromiohumeral interval of 3 mm. Which surgical intervention provides the most reliable restoration of active forward elevation in this patient?





Explanation

This patient has rotator cuff arthropathy with pseudoparalysis. A reverse total shoulder arthroplasty (RTSA) alters the center of rotation, recruiting the deltoid to effectively restore active forward elevation.

Question 68

A 14-year-old boy presents with knee pain. Radiographs demonstrate a mixed lytic and sclerotic lesion in the distal femoral metaphysis with periosteal reaction forming a Codman's triangle. Following biopsy confirming high-grade classic osteosarcoma, what is the most appropriate next step in management?





Explanation

The standard of care for high-grade classic osteosarcoma includes neoadjuvant chemotherapy followed by wide surgical resection (limb salvage if possible), and then adjuvant chemotherapy. Osteosarcoma is generally radioresistant.

Question 69

A 28-year-old male is brought to the trauma bay in hemorrhagic shock following a motorcycle crash. Pelvic radiographs reveal a wide pubic symphysis diastasis (>2.5 cm) and disruption of the anterior sacroiliac ligaments. Where is the most mechanically effective location to place a pelvic circumferential compression device (binder)?





Explanation

Pelvic binders are most effective at reducing pelvic volume and controlling hemorrhage when placed accurately at the level of the greater trochanters. Placement higher over the iliac crests can paradoxically worsen the deformity.

Question 70

A 22-year-old football player sustains a hyperplantarflexion injury to his midfoot. Weight-bearing radiographs show a 3 mm widening between the base of the first and second metatarsals. What is the precise anatomic attachment of the Lisfranc ligament?





Explanation

The Lisfranc ligament is a strong interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is critical for the structural stability of the midfoot.

Question 71

Articular cartilage is primarily composed of water, collagen, and proteoglycans. Which type of collagen constitutes the vast majority of the collagenous framework in normal, healthy adult hyaline articular cartilage?





Explanation

Type II collagen accounts for 90-95% of the collagen in healthy hyaline articular cartilage, providing its necessary tensile strength. Fibrocartilage, which often forms after microfracture procedures, is predominantly composed of Type I collagen.

Question 72

A 25-year-old male falls onto an outstretched hand and sustains a proximal pole scaphoid fracture. Which specific artery is the primary contributor to the retrograde blood supply of the scaphoid, predisposing this fracture pattern to avascular necrosis?





Explanation

The dorsal carpal branch of the radial artery supplies 70-80% of the scaphoid, entering distally and perfusing the bone in a retrograde fashion. Proximal pole fractures disrupt this vascular flow, creating a high risk of avascular necrosis.

Question 73

A 12-year-old overweight boy presents with groin pain and an obligatory external rotation of the hip during active flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following is the most significant risk factor for the development of avascular necrosis (AVN) in this patient?





Explanation

The inability to bear weight defines an unstable SCFE. Unstable SCFE has a substantially higher risk of avascular necrosis (up to 47%) compared to stable SCFE, which has an AVN rate of less than 10%.

Question 74

A 30-year-old male sustains an isolated midshaft femur fracture and is treated with a retrograde intramedullary nail. Postoperatively, what is the most commonly reported complication unique to the retrograde approach compared to antegrade nailing?





Explanation

Anterior knee pain is the most frequent complication specific to retrograde femoral nailing, often due to the intra-articular starting point or hardware prominence. Antegrade nailing is more commonly associated with hip pain or heterotopic ossification of the abductors.

Question 75

During an acute knee injury, an avulsion fracture of the anterolateral proximal tibia is visible on an AP radiograph (Segond fracture). This pathognomonic sign represents an avulsion of which structure?





Explanation

A Segond fracture is a bony avulsion of the anterolateral ligament (ALL) and the meniscotibial attachment of the lateral capsule. It is considered pathognomonic for an anterior cruciate ligament (ACL) tear.

Question 76

A 7-year-old girl is diagnosed with acute hematogenous osteomyelitis of the proximal tibia. In children, why is the metaphysis the most common initial location for hematogenous bacterial seeding?





Explanation

The metaphyseal vasculature adjacent to the physis features sharp capillary loops that transition into large venous sinusoids. This creates an area of sluggish blood flow and lower oxygen tension, acting as an ideal nidus for bacterial settling and proliferation.

Question 77

A 40-year-old male undergoes open reduction and internal fixation of a transverse radial shaft fracture using a dynamic compression plate (DCP) with absolute stability. Which type of bone healing will predominantly occur?





Explanation

Absolute stability achieved through rigid internal fixation prevents interfragmentary motion, suppressing callus formation. This leads to primary (Haversian) bone healing, where osteoclasts form cutting cones directly across the fracture, followed by osteoblast deposition.

Question 78

A 72-year-old female presents with severe neurogenic claudication secondary to lumbar spinal stenosis. Her symptoms improve when she leans forward over a shopping cart. What is the primary anatomical rationale for this positional relief?





Explanation

Lumbar flexion widens the spinal canal and neural foramina while simultaneously stretching the ligamentum flavum, reducing its inward buckling. This transient increase in canal volume mechanically relieves compression on the cauda equina and nerve roots.

Question 79

Which of the following bone graft options possesses purely osteoconductive properties without any osteoinductive or osteogenic capabilities?





Explanation

Calcium phosphate ceramics act merely as a scaffold for new bone growth, meaning they are strictly osteoconductive. Autograft is osteogenic, osteoinductive, and osteoconductive, while DBM and BMP-2 are primarily osteoinductive.

Question 80

A 14-year-old boy presents with a diaphyseal femur tumor exhibiting an 'onion-skin' periosteal reaction. A biopsy is performed. Which specific chromosomal translocation is most likely responsible for this malignancy?





Explanation

The clinical and radiographic presentation is classic for Ewing sarcoma. Ewing sarcoma is characteristically driven by the t(11;22) translocation, which results in the EWS-FLI1 fusion protein.

Question 81

During routine follow-up of a 12-year-old obese male who underwent in situ pinning for a stable Slipped Capital Femoral Epiphysis (SCFE) 6 months ago, he complains of severe global hip stiffness. Radiographs show joint space narrowing without femoral head collapse. What is the most likely complication?





Explanation

Chondrolysis presents with severe stiffness and diffuse joint space narrowing on radiographs without initial head collapse. It is a known complication of SCFE, particularly associated with unrecognized pin penetration into the joint.

Question 82

A 28-year-old male sustains a closed tibial shaft fracture. Two hours post-admission, he develops severe pain out of proportion to the injury. Which intracompartmental pressure measurement strategy dictates an absolute indication for emergency fasciotomy?





Explanation

A Delta P (diastolic blood pressure minus compartment pressure) of less than 30 mmHg is the most reliable threshold for diagnosing acute compartment syndrome. Absolute pressure thresholds are less reliable due to variations in patient perfusion pressures.

Question 83

In a patient presenting with aseptic loosening 10 years after an uncemented total hip arthroplasty, the primary driver of periprosthetic osteolysis is the activation of macrophages. Which signaling molecule is ultimately overexpressed by these cells to induce bone resorption?





Explanation

Phagocytosis of polyethylene wear debris by macrophages stimulates the release of pro-inflammatory cytokines like TNF-alpha and IL-1. This leads to the overexpression of RANKL, which drives osteoclast differentiation and subsequent periprosthetic osteolysis.

Question 84

A 22-year-old rugby player presents with an inability to actively flex the distal interphalangeal (DIP) joint of his ring finger after grabbing an opponent's jersey. Radiographs reveal a bony avulsion retracted into the palm. According to the Leddy and Packer classification, what type of injury is this?





Explanation

This is a Type I Leddy-Packer flexor digitorum profundus (FDP) avulsion, where the tendon retracts into the palm (Zone II), compromising the vincula and blood supply. It requires urgent surgical repair (within 7-10 days) to prevent tendon necrosis.

Question 85

A 25-year-old skier presents with acute knee swelling after a twisting fall. Plain radiographs reveal an avulsion fracture of the lateral tibial plateau (Segond fracture). This radiographic finding is pathognomonic for an injury to which of the following structures?





Explanation

A Segond fracture is an avulsion fracture of the anterolateral proximal tibia, representing an avulsion of the anterolateral ligament (ALL) or lateral capsular attachment. It is highly pathognomonic for an anterior cruciate ligament (ACL) tear.

Question 86

Regarding the ultrastructural composition of normal articular cartilage, how does the organization of Type II collagen fibers and chondrocyte morphology change in the deep (radial) zone compared to the superficial (tangential) zone?





Explanation

In the deep (radial) zone of articular cartilage, Type II collagen fibers are oriented perpendicularly to the joint surface to resist compressive loads. The chondrocytes in this zone are typically arranged in vertical columns.

Question 87

A 7-year-old boy is diagnosed with Legg-Calve-Perthes disease. According to the Herring Lateral Pillar Classification, which of the following radiographic findings places the patient in Group C and carries a worse prognosis?





Explanation

In the Herring Lateral Pillar Classification, Group C is defined by greater than 50% loss of height of the lateral pillar of the femoral head. This indicates significant structural collapse and carries a poor prognosis, often leading to early osteoarthritis.

Question 88

A 45-year-old male arrives in the trauma bay in hemorrhagic shock following a severe crush injury to the pelvis. Radiographs show an Anteroposterior Compression (APC) Type III pelvic ring injury. What is the most common anatomical source of massive hemorrhage in this specific injury pattern?





Explanation

In the majority of pelvic ring injuries (approximately 80%), massive hemorrhage is venous in origin, primarily from the presacral venous plexus or fractured cancellous bone surfaces. While arterial bleeding (e.g., superior gluteal artery) can occur, the presacral venous plexus is the most common source overall.

Question 89

Which of the following physical examination findings is the most sensitive indicator of early cauda equina syndrome in a patient presenting with acute low back pain and bilateral radiculopathy?





Explanation

Urinary retention is the most sensitive and often the earliest sign of cauda equina syndrome, leading to overflow incontinence as the bladder overfills. Post-void residual ultrasound showing > 100-200 mL strongly supports the diagnosis in the acute setting.

Question 90

A 32-year-old female presents with a destructive, eccentrically located lytic lesion in the distal femur epimetaphysis. Biopsy confirms a Giant Cell Tumor of bone. If medical therapy is considered, denosumab may be used. What is its specific mechanism of action?





Explanation

Denosumab is a monoclonal antibody that binds to RANKL, preventing it from binding to the RANK receptor on the surface of osteoclast precursors. This inhibits the recruitment and activation of the reactive multinucleated giant cells responsible for the aggressive osteolysis in Giant Cell Tumors.

Question 91

According to current guidelines, what is the most appropriate initial prophylactic antibiotic regimen for a 25-year-old male with a Gustilo-Anderson Type IIIb open tibia fracture occurring in a highly contaminated agricultural setting?





Explanation

For a Gustilo Type III open fracture, standard prophylaxis includes a first-generation cephalosporin and an aminoglycoside. The addition of high-dose penicillin is specifically indicated for farm/agricultural injuries to cover Clostridium species.

Question 92

During a primary total knee arthroplasty for severe varus osteoarthritis, the knee remains tight medially in both flexion and extension after initial bony cuts. Which sequence of soft tissue release is most appropriate to balance the knee?





Explanation

To correct a fixed varus deformity, step-wise medial release is performed starting with osteophytes, followed by the deep medial collateral ligament (MCL). If it remains tight, the release progresses to the posteromedial corner/capsule, and finally the superficial MCL and pes anserinus if necessary.

Question 93

When treating an infant with congenital talipes equinovarus (clubfoot) using the Ponseti method, the initial casts specifically target the correction of which deformity?





Explanation

The Ponseti method follows the CAVE sequence: Cavus, Adductus, Varus, and finally Equinus. The first cast addresses the cavus deformity by elevating the first ray to align the forefoot with the midfoot.

Question 94

A 20-year-old athlete undergoes arthroscopic evaluation for recurrent anterior shoulder instability. An 'engaging' Hill-Sachs lesion is identified. What is the most appropriate concurrent procedure to perform alongside an arthroscopic Bankart repair?





Explanation

An engaging Hill-Sachs lesion can lever the humeral head out of the glenoid during external rotation and abduction. The Remplissage procedure, which involves tenodesis of the infraspinatus and capsule into the defect, converts an intra-articular defect into an extra-articular one, preventing engagement.

Question 95

A 30-year-old male sustains a hyperplantarflexion injury to his midfoot. Radiographs demonstrate a widening of the space between the 1st and 2nd metatarsal bases with a small avulsion fragment ('fleck sign'). The disrupted ligament in this injury originates from which bone?





Explanation

The Lisfranc ligament is a stout interosseous ligament that anchors the second metatarsal to the midfoot. It originates on the lateral surface of the medial cuneiform and inserts onto the medial base of the second metatarsal.

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