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Advanced Orthopedic MCQs: ACL Cysts, Biceps Dislocation, Olecranon Fractures & Sports Injuries

27 Apr 2026 144 min read 141 Views
Can You Answer These Sports Med Questions? Orthopedic Quiz

Key Takeaway

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

ORTHOPEDIC MCQS ONLINE QUESTION BANK H3D

Comprehensive 100-Question Exam


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Question 1

A 68-year-old female is undergoing primary total hip arthroplasty. Preoperative standing and seated lateral spinopelvic radiographs reveal a change in pelvic tilt of only 4 degrees between standing and sitting, secondary to prior long-segment lumbar fusion. To minimize her risk of postoperative dislocation, how should the acetabular component positioning be adjusted relative to the standard Lewinnek 'safe zone'?





Explanation

Patients with a stiff spinopelvic junction (change in pelvic tilt < 10 degrees from stand to sit) fail to undergo the normal posterior pelvic tilt when sitting. Normally, posterior tilt increases functional acetabular anteversion, allowing clearance for the flexed femur. Without this compensatory mechanism, the patient is at a high risk for anterior impingement and subsequent posterior dislocation when seated. To compensate for a stiff spinopelvic junction, the acetabular component must be placed in relatively higher anteversion and inclination than the standard safe zone.

Question 2

A 24-year-old male presents with a deep, slow-growing soft tissue mass in his popliteal fossa. Core needle biopsy demonstrates a biphasic tumor with both epithelial and spindle cell components. Molecular analysis of this tissue is most likely to reveal which of the following characteristic chromosomal translocations?





Explanation

The clinical and histological picture describes a synovial sarcoma. Synovial sarcomas are characterized by the t(X;18) translocation, which results in the fusion of the SYT gene on chromosome 18 with one of the SSX genes on the X chromosome. The t(11;22) translocation is characteristic of Ewing sarcoma. The t(12;16) is seen in myxoid liposarcoma, and t(2;13) is seen in alveolar rhabdomyosarcoma.

Question 3

What defines an 'unstable' slipped capital femoral epiphysis (SCFE) according to the Loder classification, and what is its primary prognostic significance?





Explanation

The Loder classification divides SCFE into stable and unstable based on the patient's ability to bear weight. An unstable SCFE is defined by the inability to ambulate, even with the assistance of crutches. The primary prognostic significance of this classification is the high rate of osteonecrosis associated with unstable slips (up to 47%), compared to a nearly 0% rate in stable slips.

Question 4

A 35-year-old male is brought to the emergency department after a high-speed motorcycle collision. He is hypotensive with a systolic blood pressure of 75 mmHg. Primary survey reveals an anteroposterior compression type III (APC-III) pelvic ring injury. A pelvic binder is applied, but his hemodynamics do not improve. A FAST exam is negative for intraperitoneal fluid. What is the most appropriate next step in management according to ATLS algorithms?





Explanation

In a hemodynamically unstable patient with a severe pelvic ring fracture, initial stabilization includes a pelvic binder. If the patient remains unstable and intra-abdominal hemorrhage has been ruled out (negative FAST or DPL), the primary source of bleeding is assumed to be the retroperitoneal pelvic space (venous plexus or arterial injury). The appropriate next step is pre-peritoneal pelvic packing and/or pelvic angiography with embolization. Ex-fix application is secondary to initial volume and packing/angio protocols in the persistently hypotensive patient.

Question 5

In the evaluation of anterior shoulder instability, the 'glenoid track' concept is utilized to determine the risk of an engaging Hill-Sachs lesion. The normal width of the glenoid track is calculated as what percentage of the native inferior glenoid diameter (assuming no anterior bone loss)?





Explanation

The glenoid track concept describes the contact zone between the glenoid and the humeral head during abduction and external rotation. The native glenoid track represents 83% of the width of the inferior glenoid. If there is anterior glenoid bone loss, the width of the track is calculated as 83% minus the width of the anterior bone defect. A Hill-Sachs lesion that extends medially beyond this track is termed 'off-track' and has a high risk of engagement.

Question 6

A 60-year-old male undergoes a C3-C6 posterior laminectomy and instrumented fusion for cervical spondylotic myelopathy. On postoperative day 3, he develops new-onset unilateral deltoid and biceps weakness (grade 2/5). Sensation and lower extremity function remain unchanged. What is the most widely accepted primary pathophysiology for this delayed complication?





Explanation

Postoperative C5 palsy is a known complication following cervical decompression, particularly posterior laminectomy. The most widely accepted mechanism is the 'tethering effect.' After removing the posterior elements, the spinal cord drifts backward. Because the C5 nerve roots are short and run a transverse course, this posterior cord shift can stretch and tether the C5 root, leading to delayed motor weakness (typically deltoid and biceps). Direct surgical injury usually presents immediately, not in a delayed fashion.

Question 7

In Lichtman's classification of Kienböck disease, what specific finding differentiates Stage IIIA from Stage IIIB?





Explanation

Lichtman's classification for Kienböck disease (avascular necrosis of the lunate) divides stage III into IIIA and IIIB. Both stages feature lunate fragmentation and collapse. However, Stage IIIA maintains normal carpal alignment, while Stage IIIB is defined by fixed scaphoid rotary subluxation and a decrease in carpal height ratio. Stage IV involves widespread radiocarpal and midcarpal secondary arthritis.

Question 8

The true Lisfranc ligament is a critical stabilizer of the midfoot. Which of the following describes its exact anatomical attachments?





Explanation

The true Lisfranc ligament is a strong interosseous ligament that connects the lateral surface of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the strongest and most important stabilizing structure of the tarsometatarsal joint complex. There is notably no direct ligamentous connection between the bases of the first and second metatarsals.

Question 9

Articular cartilage relies on a precise microscopic architecture to withstand compressive and shear forces. Which zone of normal articular cartilage contains the highest concentration of proteoglycans, the lowest water content, and collagen fibers arranged perpendicular to the joint surface?





Explanation

The deep (radial) zone of articular cartilage is responsible for providing resistance to compressive forces. It is characterized by having the largest diameter collagen fibers oriented perpendicular to the joint surface, the highest concentration of proteoglycans (which provide compressive strength), and the lowest water content. The superficial zone has collagen parallel to the surface to resist shear, the highest water content, and the lowest proteoglycan content.

Question 10

A 71-year-old female who has been taking oral alendronate for 9 years presents with atraumatic lateral thigh pain. Radiographs demonstrate focal lateral cortical thickening of the proximal femoral diaphysis with a subtle transverse radiolucent line. What is the mechanism of action of the medication most strongly associated with this fracture pattern?





Explanation

The patient has a classic atypical femur fracture (AFF) associated with long-term bisphosphonate use. Bisphosphonates (like alendronate) are endocytosed by osteoclasts during bone resorption and act by inhibiting farnesyl pyrophosphate synthase (FPPS), an enzyme in the mevalonate pathway. This disrupts small GTPase signaling, ultimately causing osteoclast apoptosis. Denosumab blocks RANKL. Long-term osteoclast inhibition prevents targeted remodeling of microdamage, leading to AFFs.

Question 11

A 6-year-old male sustains a Gartland type III supracondylar humerus fracture. On presentation, his hand is pink and warm, but the radial pulse is absent. After a successful closed reduction and percutaneous pinning, the hand remains pink and warm with brisk capillary refill, but the radial pulse remains unpalpable. What is the most appropriate next step in management?





Explanation

The management of the 'pink, pulseless hand' following reduction of a supracondylar humerus fracture is a well-tested topic. If the hand remains well-perfused (pink, warm, capillary refill < 2 seconds) despite the absence of a palpable pulse, the collateral circulation is sufficient. The most appropriate next step is observation with close monitoring. Open vascular exploration or angiography is reserved for the 'white, pulseless hand' that remains dysvascular after fracture reduction.

Question 12

A 72-year-old female presents with a complete disruption of her patellar tendon 4 years following a primary total knee arthroplasty. The components remain well-fixed and there is no evidence of infection. Which of the following is the most reliable reconstructive technique with the lowest long-term failure rate?





Explanation

Extensor mechanism rupture after TKA is a catastrophic complication. Primary repair has an unacceptably high failure rate. Historically, whole extensor mechanism allografts were used but suffered from high rates of lag, stretching, and failure. Current literature strongly supports the use of synthetic mesh reconstruction (e.g., Marlex mesh) as it provides rigid fixation, does not stretch out over time, allows tissue ingrowth, and has superior long-term survival rates compared to allograft and primary repair.

Question 13

What is the optimal timing for surgical reconstruction of a multi-ligament knee injury (e.g., Schenck KD-III) in a hemodynamically stable patient with normal vascular status and no open wounds?





Explanation

The optimal timing for multi-ligament knee reconstruction in a stable patient is typically delayed 2 to 3 weeks post-injury. This delay allows for the initial inflammatory phase to subside, recovery of range of motion, and healing of the capsular tissue, which significantly decreases the risk of postoperative arthrofibrosis compared to acute (<1 week) surgery. Delaying beyond 3 weeks makes recognizing and anatomically reconstructing tissue planes more difficult due to extensive scar tissue.

Question 14

A patient presents with progressive weakness of the interosseous muscles and an inability to cross their index and middle fingers. Sensory examination reveals normal two-point discrimination over the entire little finger and the ulnar half of the ring finger. A focal compressive lesion is suspected. In which anatomical location is the lesion most likely located?





Explanation

This patient has an isolated motor deficit of the ulnar nerve without sensory deficits. Guyon's canal is divided into three zones. Zone 1 contains the combined motor and sensory branches; compression here causes mixed symptoms. Zone 2 contains only the deep motor branch; compression here causes isolated weakness of the ulnar innervated intrinsic muscles. Zone 3 contains only the superficial sensory branch; compression here causes isolated sensory deficits. Cubital tunnel syndrome typically causes both motor and sensory findings.

Question 15

According to the Brodsky classification of diabetic Charcot neuroarthropathy, a Type 1 injury primarily involves which of the following anatomic joint complexes?





Explanation

The Brodsky classification categorizes Charcot neuroarthropathy of the foot based on anatomic location. Type 1 involves the midfoot (tarsometatarsal and naviculocuneiform joints) and is the most common presentation (60%). Type 2 involves the hindfoot (subtalar, talonavicular, or calcaneocuboid joints). Type 3A involves the tibiotalar joint, and Type 3B involves the calcaneus (tuberosity fracture).

Question 16

In the Lenke classification for adolescent idiopathic scoliosis, a proximal thoracic curve is defined as a 'structural' minor curve if its side-bending Cobb angle fails to correct below what threshold?





Explanation

The Lenke classification system dictates that a minor curve is considered 'structural' if the Cobb angle remains greater than or equal to 25 degrees on coronal side-bending radiographs. If it reduces to less than 25 degrees, it is considered nonstructural. For proximal thoracic curves, a T2-T5 kyphosis of >20 degrees is also a criterion for structural definition, but the coronal bending threshold is 25 degrees.

Question 17

Highly cross-linked polyethylene (HXLPE) is standardly used in total hip arthroplasty to minimize particulate wear debris. While high-dose gamma irradiation followed by remelting decreases wear rates, it results in a clinically relevant decrease in which of the following mechanical properties compared to conventional ultra-high-molecular-weight polyethylene (UHMWPE)?





Explanation

Increasing the radiation dose to highly cross-link polyethylene reduces abrasive wear, which significantly lowers osteolysis rates. However, the process of cross-linking and subsequent thermal treatment (remelting to eliminate free radicals) adversely affects the bulk mechanical properties. Specifically, it significantly decreases ultimate tensile strength, yield strength, and fatigue crack propagation resistance, making the liner theoretically more susceptible to fracture, especially in thinner liners.

Question 18

Which of the following features most reliably distinguishes an osteoblastoma from an osteoid osteoma on advanced imaging and histologic review?





Explanation

Osteoid osteoma and osteoblastoma are both benign bone-forming tumors that share very similar, often indistinguishable, histological features (woven bone trabeculae lined by osteoblasts in a vascular stroma). The primary distinguishing feature is size. An osteoid osteoma has a nidus < 2 cm in diameter. A lesion > 2 cm is classified as an osteoblastoma. Osteoblastomas also typically do not have the classic dramatic response to NSAIDs seen in osteoid osteomas, and they tend to grow progressively.

Question 19

A 32-year-old male sustains a proximal third tibia fracture. He develops severe leg pain out of proportion and diminished two-point discrimination on the plantar aspect of his foot. Intracompartmental pressure testing indicates an isolated acute compartment syndrome of the deep posterior compartment. Which of the following anatomic structures are located within this specific compartment?





Explanation

The deep posterior compartment of the leg contains the tibialis posterior, flexor digitorum longus, flexor hallucis longus, the posterior tibial artery and vein, and the tibial nerve. Compression here leads to ischemia of the tibial nerve, causing sensory deficits on the plantar aspect of the foot. The anterior compartment contains the deep peroneal nerve and anterior tibial artery. The lateral compartment contains the superficial peroneal nerve.

Question 20

According to current cerebral palsy hip surveillance guidelines, what is the most critical radiographic metric used to dictate the need for surgical intervention to prevent hip dislocation, and at what threshold is the hip considered 'at risk' for displacement?





Explanation

The Reimers migration percentage is the standard measurement used in hip surveillance for children with cerebral palsy. It measures the percentage of the femoral head extruded laterally past the edge of the acetabulum (Perkin's line). A migration percentage > 30% defines a hip that is 'subluxated' or at significant risk for progressive displacement, triggering closer surveillance and often soft-tissue or bony surgical intervention.

Question 21

A 13-year-old boy presents with an inability to bear weight on his right leg after a minor fall. Radiographs show a slipped capital femoral epiphysis (SCFE). He is unable to walk even with the assistance of crutches. What is the most significant prognostic factor for the subsequent development of avascular necrosis (AVN) in this patient?





Explanation

According to the Loder classification, an unstable SCFE is defined strictly by the patient's inability to bear weight, even with crutches. Unstable slips have a drastically higher rate of AVN (up to 47-50%) compared to stable slips, where the AVN rate approaches zero. While time to surgery is debated, stability is the most definitively proven prognostic factor for AVN.

Question 22

A 14-year-old boy presents with a painful, swollen thigh. Radiographs reveal a permeative diaphyseal lesion with an 'onion skin' periosteal reaction. Core needle biopsy shows sheets of small round blue cells. Which of the following genetic translocations is most characteristic of this patient's underlying diagnosis?





Explanation

The clinical and radiographic presentation is classic for Ewing sarcoma. The t(11;22)(q24;q12) translocation, which creates the EWS-FLI1 fusion protein, is present in approximately 85% of Ewing sarcoma cases. t(X;18) is associated with synovial sarcoma; t(12;16) with myxoid liposarcoma; t(9;22) with extraskeletal myxoid chondrosarcoma (and CML); and t(2;13) with alveolar rhabdomyosarcoma.

Question 23

Six months following an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, a patient complains of a progressive loss of terminal knee extension accompanied by an audible clunk at the end of range of motion. MRI reveals a nodular mass in the anterior intercondylar notch. Histological examination of this mass would most likely show:





Explanation

The scenario describes 'Cyclops syndrome', a form of localized anterior arthrofibrosis that mechanically blocks terminal knee extension after ACL reconstruction. The 'cyclops lesion' itself is composed primarily of fibrovascular scar tissue, which proliferates in the anterior notch.

Question 24

A 65-year-old man presents with deteriorating handwriting, frequent dropping of objects, and a broad-based, unsteady gait. Physical examination reveals a positive Hoffmann sign bilaterally. Elicitation of the brachioradialis reflex results in spontaneous flexion of the fingers without normal wrist extension or radial deviation. This specific reflex finding indicates spinal cord compression at which anatomical level?





Explanation

The patient exhibits an inverted brachioradialis reflex, a classic localizing sign in cervical spondylotic myelopathy. It indicates compression at the C5-C6 level. The reflex tests the C6 nerve root; compression at this level causes a lower motor neuron lesion at C6 (absent brachioradialis jerk) and an upper motor neuron lesion below this level (hyperactive finger flexion mediated by C8).

Question 25

A 68-year-old man who underwent a metal-on-polyethylene total hip arthroplasty 6 years ago presents with new-onset groin pain. Radiographs show well-fixed components. Inflammatory markers (ESR, CRP) and hip aspiration are normal. Metal ion analysis reveals significantly elevated serum cobalt levels with normal serum chromium levels. MRI with metal artifact reduction sequence (MARS) demonstrates a solid/cystic periarticular mass. What is the most likely source of this failure?





Explanation

Disproportionately elevated cobalt relative to chromium in a patient with a metal-on-polyethylene (or ceramic-on-polyethylene) total hip arthroplasty is the hallmark of mechanically assisted crevice corrosion (MACC), also known as trunnionosis, occurring at the modular head-neck taper junction. This generates metal wear debris, leading to an adverse local tissue reaction (ALTR).

Question 26

During the repair of a zone II flexor digitorum profundus (FDP) laceration, the surgeon must choose an appropriate suture configuration. Biomechanical studies indicate that the overall ultimate tensile strength of a flexor tendon repair and its resistance to gap formation are most directly proportional to which of the following?





Explanation

Extensive biomechanical studies have proven that the strength of a flexor tendon repair and its resistance to gap formation are directly proportional to the number of core suture strands that cross the repair site. For example, a 4-strand repair is significantly stronger than a 2-strand repair, and a 6-strand is stronger than a 4-strand.

Question 27

A 25-year-old athlete sustains a purely ligamentous Lisfranc injury. Nonoperative management is unsuccessful, and surgical intervention is planned. Based on high-quality prospective literature comparing open reduction internal fixation (ORIF) to primary arthrodesis for purely ligamentous Lisfranc injuries, which of the following is true regarding primary arthrodesis?





Explanation

Prospective randomized trials (such as Ly and Coetzee, JBJS 2006) comparing ORIF to primary arthrodesis for primarily ligamentous Lisfranc injuries have shown that primary arthrodesis results in better or comparable short- and long-term functional outcomes and significantly lowers the rate of secondary surgeries (such as hardware removal or salvage fusion for post-traumatic arthritis).

Question 28

A 42-year-old man is struck by a motor vehicle and sustains a closed, displaced transverse acetabular fracture. Examination reveals a large, fluctuant area over the greater trochanter and lateral thigh. Aspiration of the collection yields serosanguinous fluid with fat droplets. What is the most appropriate management of this soft tissue lesion in the context of planned surgical fracture fixation?





Explanation

The patient has a Morel-Lavallée lesion, a closed internal degloving injury where subcutaneous tissue is sheared off the underlying fascia, creating a cavity filled with blood, lymph, and necrotic fat. If large and situated in the surgical field for a planned fracture fixation (e.g., Kocher-Langenbeck approach), it carries a very high risk of infection. Standard management is formal incision, extensive debridement of necrotic tissue, and dead-space management.

Question 29

Bone morphogenetic proteins (BMPs) play a crucial role in bone repair and osteoinduction. Following the binding of a BMP molecule to its specific cell surface receptor, which of the following intracellular signaling proteins is primarily phosphorylated to translocate to the nucleus and promote osteoblast differentiation?





Explanation

BMP signaling is primarily mediated through the canonical Smad pathway. When BMP binds to its heterodimeric serine/threonine kinase receptor, it phosphorylates receptor-regulated Smads (Smad 1, 5, and 8). These then form a complex with the co-Smad (Smad 4), which translocates to the nucleus to regulate the transcription of osteogenic genes, including Runx2.

Question 30

A 4-month-old girl is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. At her 2-week follow-up, the parents note that she is no longer actively kicking her left leg. On examination, the infant lacks active knee extension on the left side, though distal perfusion and other movements are intact. What is the most appropriate next step in management?





Explanation

The infant has developed a femoral nerve palsy, a known complication of Pavlik harness treatment, usually caused by excessive hip hyperflexion compressing the femoral nerve against the inguinal ligament. The standard of care is to immediately discontinue the harness to allow the nerve to recover, which usually occurs within days to weeks, before reassessing treatment options.

Question 31

Denosumab has emerged as an effective medical therapy for locally advanced or unresectable giant cell tumors of bone (GCTB). What is the specific cellular target and mechanism of action of this medication?





Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). In GCTB, RANKL is excessively secreted by the neoplastic mononuclear stromal cells. By neutralizing RANKL, denosumab prevents it from binding to the RANK receptor on osteoclast precursors, dramatically inhibiting osteoclast-mediated bone destruction.

Question 32

A 22-year-old rugby player undergoes evaluation for recurrent anterior shoulder instability. Advanced imaging and 3D reconstruction reveal an anterior inferior labral tear and a Hill-Sachs lesion that actively engages the anterior glenoid rim when the arm is placed in abduction and external rotation. The glenoid bone loss is calculated at 12%. Which of the following surgical procedures is most appropriate?





Explanation

For recurrent anterior shoulder instability with an 'engaging' (or off-track) Hill-Sachs lesion but subcritical glenoid bone loss (typically <20-25%), adding a Remplissage (tenodesis of the infraspinatus tendon into the Hill-Sachs defect) to an arthroscopic Bankart repair is the standard of care. This prevents the humeral head defect from engaging the glenoid rim. A Latarjet or structural grafting is generally reserved for critical glenoid bone loss (>20-25%).

Question 33

In the evaluation of an infant presenting with infantile idiopathic scoliosis, which of the following radiographic measurements is widely considered the most reliable predictor of curve progression versus spontaneous resolution?





Explanation

In infantile idiopathic scoliosis, the Rib-Vertebra Angle Difference (RVAD), described by Min Mehta, is the most crucial prognostic indicator. An RVAD greater than 20 degrees is strongly associated with a high likelihood of curve progression (progressive phase), whereas an RVAD of less than 20 degrees usually suggests the curve will spontaneously resolve (resolving phase).

Question 34

During a cruciate-retaining total knee arthroplasty (TKA), the trial components are placed. On examination of the joint spaces, the knee is found to be tight in extension but perfectly balanced in flexion. Assuming standard alignment has been achieved, which of the following is the most appropriate corrective action?





Explanation

In TKA balancing, if a knee is symmetrically tight in extension but balanced in flexion, the extension gap needs to be increased without altering the flexion gap. Resecting additional bone from the distal femur exclusively increases the extension gap. Modifying the tibia or the polyethylene thickness would affect both gaps, while downsizing the femoral component or releasing the PCL primarily affects the flexion gap.

Question 35

A 45-year-old woman is scheduled for an open carpal tunnel release. The surgeon is mindful of the anatomical variations of the recurrent motor branch of the median nerve to avoid iatrogenic injury. According to the Lanz classification, which of the following represents the most common anatomical course of the recurrent motor branch?





Explanation

According to the Lanz classification of the median nerve at the wrist, the most common course of the recurrent motor branch is extraligamentous with recurrent branching (Group 1, occurring in approximately 46-90% of individuals). In this pattern, the branch arises distal to the transverse carpal ligament and curls back to innervate the thenar musculature.

Question 36

A 35-year-old recreational basketball player suffers an acute, closed Achilles tendon rupture. He is evaluating treatment options and asks about the risk of re-rupture. Based on recent high-quality randomized controlled trials, which of the following statements comparing nonoperative and operative management is most accurate?





Explanation

Multiple modern, high-quality randomized controlled trials (such as Willits et al., JBJS 2010) have demonstrated that when an early functional rehabilitation protocol (involving early weight-bearing and active range of motion) is employed, the re-rupture rates between nonoperative and operative treatment of acute Achilles tendon ruptures are statistically equivalent. Operative treatment, however, carries a higher risk of soft-tissue complications.

Question 37

A 62-year-old woman is treated in a short arm cast for a minimally displaced, extra-articular fracture of the distal radius. Four weeks later, her cast is removed, but she suddenly loses the ability to actively extend her thumb interphalangeal joint. She has no sensory deficits. What is the most likely etiology of this complication?





Explanation

EPL tendon rupture is a well-documented complication following nondisplaced or minimally displaced distal radius fractures treated conservatively. It occurs due to localized ischemia within the third dorsal compartment (a watershed area for the tendon as it angles around Lister's tubercle), compounded by mechanical attrition from the fracture hematoma or callus.

Question 38

During the biomechanical evaluation of a ligament's viscoelastic properties, researchers observe that when the ligament is subjected to a constant, sustained mechanical load over a period of time, it experiences a gradual, continuous increase in length. This specific phenomenon is defined as:





Explanation

'Creep' is a fundamental viscoelastic property of biological tissues like ligaments and tendons. It is defined as the progressive deformation (elongation) of a material over time when it is subjected to a constant load or stress. 'Stress relaxation' is the gradual decrease in stress when a material is held at a constant length. 'Hysteresis' is the loss of energy (as heat) between the loading and unloading curves.

Question 39

When utilizing the Ponseti method for the serial casting and correction of idiopathic clubfoot (talipes equinovarus), which of the following sequences correctly represents the order in which the deformity components are addressed?





Explanation

The Ponseti method dictates correcting the components of a clubfoot in a strict sequence, classically remembered by the mnemonic CAVE: Cavus, Adductus, Varus, Equinus. The first step involves elevating the first ray to correct the cavus. Next, the forefoot adductus and hindfoot varus are corrected simultaneously by abducting the foot around the fixed talar head. Finally, the equinus is corrected, which often necessitates a percutaneous Achilles tenotomy.

Question 40

A 15-year-old girl is diagnosed with conventional, high-grade osteosarcoma of the distal femur. She completes a course of neoadjuvant chemotherapy and subsequently undergoes wide surgical resection. Pathological analysis of the resected specimen evaluates the percentage of tumor necrosis. According to the Rosen/Huvos grading system, what percentage of tumor necrosis is the established threshold to classify her as having a 'good response' to chemotherapy?





Explanation

In the histological grading of osteosarcoma's response to neoadjuvant chemotherapy (the Rosen or Huvos grading system), a 'good response' is defined by >= 90% tumor necrosis (Grade 3 is 90-99% necrosis, Grade 4 is 100% necrosis). Patients achieving >= 90% necrosis have a significantly better long-term survival prognosis compared to 'poor responders' (< 90% necrosis).

Question 41

In the context of galvanic corrosion in orthopedic implants, which of the following combinations of metals has the highest risk of severe galvanic corrosion when in direct contact in a saline environment?





Explanation

Galvanic corrosion occurs when two dissimilar metals are in direct electrical contact within an electrolytic solution (like body fluids). Stainless steel is more anodic (less noble) compared to Titanium, which is highly cathodic (noble). When mixed, the stainless steel acts as the anode and corrodes rapidly. Mixing Stainless Steel 316L and Titanium is a classic contraindication in orthopedics.

Question 42

Which of the following chromosomal translocations is diagnostic for Synovial Sarcoma?





Explanation

Synovial sarcoma is characterized by the t(X;18)(p11;q11) translocation, which leads to the SYT-SSX fusion gene. t(11;22) is seen in Ewing Sarcoma; t(12;16) is seen in myxoid liposarcoma; t(2;13) in alveolar rhabdomyosarcoma; and t(9;22) in extraskeletal myxoid chondrosarcoma (as well as CML).

Question 43

During the incorporation process of a bone-patellar tendon-bone (BPTB) autograft used for ACL reconstruction, what is the weakest point of the construct at 6 to 8 weeks postoperatively?





Explanation

The autograft undergoes a process of 'ligamentization' which involves early necrosis, followed by revascularization and cellular repopulation. At 6 to 8 weeks postoperatively, the graft is undergoing extensive remodeling, and its mid-substance becomes the weakest link, rather than the initial fixation sites (bone plugs) which usually incorporate by 6 weeks.

Question 44

Biomechanical optimization during Total Hip Arthroplasty (THA) is crucial for longevity and function. Increasing the femoral offset during a THA has which of the following mechanical effects?





Explanation

Increasing the femoral offset increases the moment arm of the hip abductors. Because the abductor moment arm is longer, less force is required by the abductor muscles to maintain pelvic level during the single-leg stance phase of gait. The decreased necessary muscle force translates directly into a decreased overall joint reaction force on the hip.

Question 45

A 35-year-old male sustains a vertical, shear-type (Pauwels Type III) femoral neck fracture. Biomechanically, what is the most stable fixation strategy to resist vertical shear forces while preserving the native hip?





Explanation

Pauwels Type III fractures (>50 degrees to horizontal) experience high vertical shear forces. Biomechanical studies have shown that a fixed-angle device, such as a sliding hip screw (SHS), combined with an anti-rotation screw provides superior resistance to vertical shear and a higher load to failure compared to multiple parallel cancellous screws in young adults with high-angle femoral neck fractures.

Question 46

In a severe, stable slipped capital femoral epiphysis (SCFE) treated with in situ single screw fixation, what is the most significant consequence of unrecognized pin penetration into the anterior-superior quadrant of the joint?





Explanation

Unrecognized intra-articular hardware penetration during SCFE pinning is the leading iatrogenic cause of chondrolysis. While avascular necrosis (AVN) is a devastating complication, it is more often associated with the initial severity/instability of the slip or aggressive attempted reduction rather than isolated pin penetration.

Question 47

A 45-year-old patient presents with cervical radiculopathy. Physical examination reveals weakness in triceps extension, wrist flexion, and finger extension, along with a diminished triceps reflex. Sensation is decreased over the palmar aspect of the middle finger. Which cervical nerve root is most likely affected?





Explanation

A C7 radiculopathy classically presents with weakness in the triceps, wrist flexors (FCR, FCU), and finger extensors (EDC). The triceps reflex is typically diminished, and there is sensory loss in the C7 dermatome, which uniquely includes the middle finger.

Question 48

In flexor tendon injury topography, Bunnell's historic "no man's land" of the hand corresponds to Zone II. This zone is anatomically defined as the region between which of the following structures?





Explanation

Flexor tendon Zone II, historically known as "no man's land" due to poor surgical outcomes prior to modern techniques, extends from the A1 pulley (approximately at the distal palmar crease) to the insertion of the flexor digitorum superficialis (FDS) tendon on the middle phalanx. Both FDS and FDP travel tightly together in the fibro-osseous sheath here.

Question 49

The primary stabilizing ligament of the Lisfranc joint complex is crucial for maintaining the integrity of the midfoot. This ligament connects which two osseous structures?





Explanation

The Lisfranc ligament is an intra-articular ligament that originates on the lateral aspect of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal. There is no direct ligamentous connection between the bases of the first and second metatarsals, making the Lisfranc ligament essential for stability.

Question 50

According to the delta pressure criteria for diagnosing acute compartment syndrome, emergency fasciotomy is universally indicated when the difference between the patient's diastolic blood pressure and the measured compartment pressure falls below what threshold?





Explanation

The delta pressure is calculated as Diastolic Blood Pressure (DBP) minus the intracompartmental pressure. A delta pressure of less than 30 mmHg indicates inadequate perfusion to the tissue capillary beds and is the universally accepted threshold indicating the need for emergent fasciotomy.

Question 51

In the management of anterior shoulder instability with a concurrent osseous defect on the posterolateral humeral head (Hill-Sachs lesion), whether the lesion is "engaging" is best conceptualized and predicted using which of the following biomechanical paradigms?





Explanation

The Glenoid Track concept, described by Itoi et al., states that if a Hill-Sachs lesion remains within the 'track' of the glenoid during external rotation and abduction, it is 'on-track' and will not engage the anterior glenoid rim. If it extends medially outside this track, it is 'off-track' and is considered an engaging lesion, often necessitating a Remplissage or structural graft.

Question 52

A patient with a metal-on-metal total hip arthroplasty presents with deep groin pain 5 years postoperatively. MRI demonstrates a large, complex solid-to-cystic periprosthetic mass. Blood work reveals elevated serum cobalt and chromium ions. Histologically, this Adverse Local Tissue Reaction (ALTR/ALVAL) is primarily mediated by which immunologic mechanism?





Explanation

Adverse Local Tissue Reactions (ALTR), particularly Aseptic Lymphocytic Vasculitis Associated Lesions (ALVAL) seen in metal-on-metal implants, are characterized by a profound perivascular lymphocytic infiltrate. This represents a Type IV (delayed-type, T-cell mediated) hypersensitivity reaction to metal wear debris (specifically cobalt and chromium).

Question 53

Following an acute traumatic spinal cord injury, the patient enters a phase of spinal shock, characterized by flaccid paralysis, areflexia, and loss of autonomic tone below the level of injury. The resolution of this spinal shock phase is clinically marked by the return of which of the following reflexes?





Explanation

The bulbocavernosus reflex is an S2-S4 reflex. Its return signifies the end of the spinal shock phase. Once it returns, any neurologic deficit remaining is usually considered the baseline incomplete or complete spinal cord injury.

Question 54

The Ponseti method for the conservative management of congenital talipes equinovarus (clubfoot) emphasizes a specific sequence of deformity correction during serial casting. What is the correct sequence of correction?





Explanation

The correct sequence of correction in the Ponseti method follows the acronym CAVE: Cavus (corrected by supinating the forefoot and elevating the first ray), Adductus, Varus (corrected together by abducting the midfoot with counter-pressure on the talar head), and finally Equinus (which often requires a percutaneous Achilles tenotomy).

Question 55

Articular cartilage is structurally divided into four distinct zones. Which zone possesses the highest concentration of water and the lowest concentration of proteoglycans, primarily providing tensile strength to the articular surface?





Explanation

The superficial (tangential) zone makes up the top 10-20% of articular cartilage. It contains the highest water content (up to 80%) and the lowest proteoglycan concentration. The collagen fibers (mostly Type II) are oriented parallel to the joint surface to resist shear and provide maximum tensile strength.

Question 56

During an anterior transposition of the ulnar nerve at the elbow, the surgeon dissects proximally to resect the medial intermuscular septum, preventing nerve kinking. Which artery, traveling with the ulnar nerve in the posterior compartment of the arm, provides its primary blood supply and must be carefully managed?





Explanation

The superior ulnar collateral artery branches from the brachial artery and pierces the medial intermuscular septum to enter the posterior compartment of the arm. It travels closely with the ulnar nerve and provides its primary extrinsic vascular supply in this region. The inferior ulnar collateral artery also contributes but typically anastomoses more distally.

Question 57

A 55-year-old poorly controlled diabetic patient presents with a swollen, warm, and erythematous left foot with a bounding pulse. Plain radiographs reveal severe osseous fragmentation, periarticular debris, and joint subluxation at the midfoot. According to the Eichenholtz classification for Charcot neuroarthropathy, what stage does this represent?





Explanation

Eichenholtz Stage I is the Development/Fragmentation phase, characterized clinically by acute swelling and erythema, and radiographically by bony fragmentation, joint subluxation/dislocation, and debris. Stage 0 shows soft tissue swelling with normal radiographs. Stage II is Coalescence (absorption of debris, early fusion). Stage III is Consolidation (remodeling).

Question 58

According to the Schatzker classification system for tibial plateau fractures, a fracture pattern involving the lateral tibial plateau that is uniquely associated with metaphyseal-diaphyseal dissociation (where the entire condyle or condyles separate from the shaft) is classified as:




Explanation

A Schatzker Type VI fracture is defined by metaphyseal-diaphyseal dissociation. It can involve either one or both condyles separating completely from the diaphyseal shaft, representing a high-energy injury pattern often associated with severe soft tissue compromise and a higher risk of compartment syndrome. Type V is bicondylar but without the complete transverse separation of metaphysis from diaphysis.

Question 59

A 25-year-old female presents with a lytic, eccentrically located, expansile lesion in the distal femur epiphysis extending to the subchondral bone. Core needle biopsy histology shows sheets of multinucleated giant cells in a stroma of plump mononuclear cells. Neoadjuvant therapy with Denosumab is considered. What is the precise mechanism of action of Denosumab?





Explanation

Giant Cell Tumor of Bone (GCTB) stromal cells express RANK Ligand (RANKL), which recruits and activates the reactive multinucleated osteoclast-like giant cells that cause bone destruction. Denosumab is a fully human monoclonal antibody that binds to RANKL, preventing it from binding to the RANK receptor on osteoclasts, thus halting osteolysis.

Question 60

When optimizing the fixation strength of a cortical or cancellous bone screw, the pull-out strength of the screw is most directly and linearly proportional to which of the following design parameters?





Explanation

Screw pull-out strength is directly proportional to the outer (thread) diameter, the length of thread engagement in the bone, and the shear strength of the bone. Increasing the outer diameter provides more surface area of thread engaging the bone, substantially increasing pull-out strength. Conversely, increasing the core diameter (while keeping outer diameter the same) decreases thread depth and can lower pull-out strength.

Question 61

A 25-year-old athlete undergoes an ACL reconstruction with a hamstring autograft. The surgeon applies a constant 20 N tension to the graft for 10 minutes prior to fixation. The graft elongates over this time without an increase in the applied force. This viscoelastic phenomenon is best described as:





Explanation

Creep is a viscoelastic property defined as progressive deformation (elongation) of a material over time when subjected to a constant load. In contrast, stress relaxation is the decrease in stress (tension) within a material over time when it is held at a constant length (deformation). Pre-tensioning an ACL graft utilizes both creep and stress relaxation to minimize post-implantation elongation.

Question 62

A 68-year-old woman presents with an audible and palpable 'clunk' in her knee when extending from a flexed position, 1 year after a posterior-stabilized (PS) total knee arthroplasty. Her radiographs are unremarkable and the components appear well-fixed. What is the most common underlying cause of this specific condition?





Explanation

Patellar clunk syndrome is a known complication of posterior-stabilized (PS) total knee arthroplasties. It is caused by the formation of a fibrous nodule at the superior pole of the patella. As the knee extends from a flexed position, this nodule catches in the intercondylar box of the femoral component and then abruptly releases with a palpable and audible 'clunk'.

Question 63

During a medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability, the surgeon uses fluoroscopy to determine the anatomic femoral attachment site. According to Schöttle's method, where should the femoral tunnel be placed on a true lateral radiograph?





Explanation

Schöttle's point is a radiographic landmark on a true lateral radiograph of the knee used to identify the anatomic femoral origin of the MPFL. It is located 1 mm anterior to the posterior femoral cortical line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the posterior extension of Blumensaat's line.

Question 64

A 45-year-old male is brought to the ED after a motorcycle accident. He has a systolic blood pressure of 75 mmHg. Radiographs show an anteroposterior compression type III (APC-III) pelvic fracture. A pelvic binder is applied, and 2 liters of crystalloid and 2 units of packed RBCs are given. His BP improves to 85 mmHg but remains tenuous. FAST exam is negative. What is the most appropriate next step in management?





Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury (like APC-III), initial management includes mechanical stabilization (binder) and resuscitation. If the patient remains unstable and intra-abdominal bleeding is ruled out (negative FAST), the bleeding is presumed to be retroperitoneal from the pelvic fracture. The next most appropriate step is pelvic angiography with embolization or preperitoneal pelvic packing.

Question 65

A 32-year-old male sustains a traumatic spondylolisthesis of the axis (Hangman's fracture). Radiographs demonstrate an oblique fracture through the pars interarticularis with severe angulation and minimal translation. The C2-C3 disc space is widened posteriorly. According to the Levine-Edwards classification (Type IIA), which of the following is the most appropriate initial non-operative management?





Explanation

Levine-Edwards Type IIA Hangman's fractures show significant angulation with minimal translation and denote a flexion-distraction injury with an incompetent C2-C3 disc. Cervical traction is strictly contraindicated as it will worsen the deformity and cause over-distraction. The treatment is reduction under fluoroscopy with gentle extension and compression, followed by application of a halo vest.

Question 66

A 13-year-old boy who underwent in-situ pinning for a stable, severe slipped capital femoral epiphysis (SCFE) 6 months ago now presents with severe hip stiffness and a painful limp. Radiographs demonstrate a concentric loss of joint space in the affected hip of greater than 50% accompanied by periarticular osteopenia. What is the most likely diagnosis?





Explanation

Chondrolysis is a severe complication of SCFE, characterized clinically by progressive stiffness and pain, and radiographically by a concentric loss of joint space (greater than 50% compared to the contralateral side) and regional osteopenia. Risk factors include severe slips, unrecognised pin penetration, and spica cast immobilization. AVN typically presents with subchondral collapse and sclerosis rather than concentric joint space narrowing.

Question 67

A 35-year-old male sustained a midshaft humerus fracture resulting in a permanent radial nerve palsy. He is undergoing tendon transfer surgery to restore function. To restore functional and balanced wrist extension without inducing significant radial deviation, which of the following is the most preferred tendon transfer?





Explanation

The most widely accepted and reliable tendon transfer to restore wrist extension in a radial nerve palsy is the Pronator Teres (PT) to the Extensor Carpi Radialis Brevis (ECRB). The ECRB is chosen over the ECRL because its insertion is more central (base of the 3rd metacarpal), which provides pure wrist extension without the radial deviation that occurs when using the ECRL.

Question 68

A 28-year-old female presents with a slow-growing, painful mass in her right foot. MRI reveals a deep soft tissue mass that is lobulated and shows inhomogeneous enhancement. Core biopsy demonstrates a biphasic tumor with spindle cells and epithelial components. Which of the following chromosomal translocations is most characteristic of this diagnosis?





Explanation

The clinical and histologic description (biphasic tumor in the foot of a young adult) is classic for Synovial Sarcoma. The hallmark cytogenetic abnormality for synovial sarcoma is the t(X;18)(p11;q11) translocation, which results in the SYT-SSX fusion gene. t(11;22) is seen in Ewing sarcoma; t(12;16) in myxoid liposarcoma; t(2;13) in alveolar rhabdomyosarcoma; and t(9;22) in extraskeletal myxoid chondrosarcoma.

Question 69

A 55-year-old poorly controlled diabetic patient presents with a swollen, warm, and erythematous left foot. Peripheral pulses are bounding. Radiographs show periarticular debris, subluxation of the tarsometatarsal joints, and active fragmentation of the bone without signs of coalescence. According to the Eichenholtz classification, what is the current stage of this patient's Charcot arthropathy and what is the primary treatment?





Explanation

This patient is in Eichenholtz Stage I (Developmental/Fragmentation) of Charcot arthropathy, characterized clinically by the 'hot, swollen' foot and radiographically by bony fragmentation, joint dislocation, and debris. The standard of care during this active phase is strict offloading and immobilization, most effectively achieved with a total contact cast (TCC) to prevent further deformity until the active inflammatory process subsides.

Question 70

A 45-year-old active male is undergoing a total hip arthroplasty. The surgeon opts for a ceramic-on-ceramic bearing surface to minimize wear. Which of the following is a known disadvantage or complication specifically associated with this bearing couple?





Explanation

Ceramic-on-ceramic (CoC) bearings offer extremely low wear rates and are highly biologically inert, negating the risk of massive osteolysis or systemic metal ion release. However, unique disadvantages include an audible 'squeaking' during gait (occurring in up to 10% of patients) and the rare but severe risk of catastrophic brittle fracture of the ceramic head or liner.

Question 71

Which of the following molecules, produced by osteoblasts, acts as a critical decoy receptor for the receptor activator of nuclear factor-kappa B ligand (RANKL), thereby preventing its binding to RANK and inhibiting osteoclast differentiation and bone resorption?





Explanation

Osteoprotegerin (OPG) is secreted by osteoblasts and binds to RANKL, preventing it from binding to the RANK receptor on osteoclast precursors. This acts as a negative regulator of osteoclastogenesis. The balance between RANKL and OPG is the primary determinant of bone resorption rate.

Question 72

Recent anatomic studies have challenged historical teachings regarding the vascularity of the proximal humerus. Based on current evidence, which of the following arteries provides the predominant blood supply to the humeral head?





Explanation

Historically, the arcuate artery (the ascending branch of the anterior humeral circumflex artery) was thought to be the primary blood supply to the humeral head. However, modern quantitative anatomic studies (e.g., Brooks et al., and Hettrich et al.) have demonstrated that the posterior humeral circumflex artery provides the vast majority (approximately 64%) of the blood supply to the humeral head.

Question 73

A 45-year-old manual laborer presents with progressive wrist pain following an untreated scaphoid fracture 5 years ago. Radiographs demonstrate a scaphoid non-union advanced collapse (SNAC) pattern. Degenerative changes are noted at the radial styloid and the entire radioscaphoid joint, but the capitolunate and radiolunate joints are preserved. What is the correct SNAC stage for this patient?





Explanation

The SNAC (Scaphoid Nonunion Advanced Collapse) classification outlines the progression of arthritis. Stage I: Arthritis localized to the radial styloid. Stage II: Arthritis extending to involve the entire radioscaphoid joint. Stage III: Arthritis progresses to involve the capitolunate joint. Stage IV: Pancarpal arthritis (though the radiolunate joint is often remarkably spared until very late). Because the entire radioscaphoid joint is involved but the capitolunate is spared, this is Stage II.

Question 74

A 68-year-old male complains of bilateral leg and buttock pain that worsens with walking and prolonged standing. Which of the following clinical findings most strongly suggests neurogenic claudication secondary to lumbar spinal stenosis rather than vascular claudication?





Explanation

Neurogenic claudication is exacerbated by lumbar extension (which decreases canal volume) and relieved by lumbar flexion (which increases canal volume). The 'shopping cart sign' (relief upon leaning forward) and better tolerance of walking uphill compared to downhill are classic for neurogenic claudication. Vascular claudication is typically relieved simply by stopping and standing still, radiates distal to proximal, and is associated with diminished pulses and skin changes.

Question 75

An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the 2-week follow-up, the mother notices that the infant is no longer kicking her right leg, and the quadriceps muscle appears flaccid. Which of the following harness positioning errors is the most likely cause of this complication?





Explanation

A femoral nerve palsy in an infant treated with a Pavlik harness is typically caused by excessive flexion of the hips (hyperflexion), which compresses the femoral nerve against the inguinal ligament. Excessive abduction is associated with a different severe complication: avascular necrosis (AVN) of the femoral head.

Question 76

A 24-year-old overhead throwing athlete presents with deep shoulder pain and clicking. MRI arthrogram shows a detachment of the superior labrum and the origin of the long head of the biceps tendon from the glenoid. The labral tissue itself is not torn in a bucket-handle fashion, and the biceps tendon is intact but detached at its anchor. According to the Snyder classification, what type of SLAP lesion is this?





Explanation

The Snyder classification of SLAP (Superior Labrum Anterior to Posterior) tears: Type I is fraying of the superior labrum with an intact biceps anchor. Type II is detachment of the superior labrum and biceps anchor from the superior glenoid. Type III is a bucket-handle tear of the labrum with an intact biceps anchor. Type IV is a bucket-handle tear of the labrum that extends into the biceps tendon.

Question 77

A 35-year-old male falls from a height and sustains a femoral neck fracture. The fracture line makes an angle of 65 degrees with the horizontal on the anteroposterior radiograph. According to the Pauwels classification, what is the main biomechanical consequence of this vertical fracture pattern compared to a more horizontal fracture?





Explanation

The Pauwels classification for femoral neck fractures is based on the angle the fracture line makes with the horizontal. Type I is <30 degrees, Type II is 30-50 degrees, and Type III is >50 degrees. Higher angles (more vertical fractures) experience immensely increased shear forces rather than compressive forces, predisposing them to a high rate of nonunion, fixation failure, and varus collapse.

Question 78

A 62-year-old male presents with new-onset groin pain and a swelling over his lateral thigh 5 years after a primary metal-on-polyethylene total hip arthroplasty. The implant consists of a large-diameter cobalt-chromium femoral head on a titanium stem. Blood work reveals elevated serum cobalt levels, while chromium levels are relatively low. Aspiration of the hip yields clear fluid with a normal cell count. What is the most likely diagnosis?





Explanation

Trunnionosis refers to wear and corrosion at the modular head-neck junction (the trunnion). It is particularly noted in implants using large-diameter cobalt-chromium heads on titanium stems. This mechanically assisted crevice corrosion releases cobalt ions, which can lead to an adverse local tissue reaction (ALTR/ALVAL), presenting as pain and an aseptic pseudotumor, even in metal-on-polyethylene hips.

Question 79

A 22-year-old football player sustains a hyperplantarflexion injury to his midfoot. Radiographs show a small avulsion fracture fragment in the intercuneiform space (the 'fleck sign'). This bony fragment represents an avulsion of the Lisfranc ligament from its attachment on which of the following structures?





Explanation

The Lisfranc ligament is an intraosseous ligament that runs from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. The 'fleck sign' pathognomonic for a Lisfranc injury represents a bony avulsion of this ligament from the base of the second metatarsal.

Question 80

During the normal human gait cycle, at which specific phase is the gluteus maximus muscle most active to prevent forward pitching of the trunk and to initiate hip extension?





Explanation

The gluteus maximus reaches its peak activity during initial contact and the loading response phase of the gait cycle. Its primary function during this time is to decelerate the forward momentum of the trunk (preventing a forward pitch) and to initiate hip extension, absorbing the shock of weight acceptance.

Question 81

A 62-year-old female presents with persistent groin pain two years after undergoing a primary total hip arthroplasty using a modular neck cobalt-chromium femoral stem and a titanium acetabular cup. Aspiration of the hip yields clear fluid with a WBC count of 800 cells/uL and a high percentage of macrophages, while serum cobalt and chromium levels are significantly elevated. Revision surgery is performed. Histological analysis of the periprosthetic tissue is most likely to reveal which of the following?





Explanation

This clinical scenario describes adverse local tissue reaction (ALTR) or Aseptic Lymphocytic Vasculitis-Associated Lesion (ALVAL) secondary to trunnionosis (fretting and crevice corrosion at the modular neck-stem junction). ALVAL is characterized histologically by a type IV delayed hypersensitivity reaction, featuring extensive perivascular lymphocytic infiltrates, tissue necrosis, and a loss of normal synovial architecture. Polymorphonuclear leukocytes would suggest acute infection.

Question 82

A 35-year-old male receives systemic denosumab therapy prior to surgical resection of a large, recurrent giant cell tumor of the distal femur. By what mechanism does denosumab alter the histological appearance of this tumor?





Explanation

Denosumab is a fully human monoclonal antibody that binds directly to RANK-Ligand (RANKL), not the RANK receptor. In Giant Cell Tumor (GCT) of bone, the neoplastic mononuclear stromal cells secrete high levels of RANKL, which recruits and activates the reactive multinucleated giant cells. By neutralizing RANKL, denosumab halts giant cell formation and activity, leading to a marked histological depletion of giant cells and replacement with dense woven bone and fibrous stroma.

Question 83

During biomechanical testing of the knee's posterolateral corner (PLC), sequential sectioning of the structures is performed. Which of the following describes the primary restraint to varus angulation at 30 degrees of knee flexion?





Explanation

The fibular collateral ligament (FCL), also known as the lateral collateral ligament (LCL), is the primary restraint to varus opening of the knee, particularly at 30 degrees of knee flexion. The popliteus tendon and popliteofibular ligament primarily act as the primary restraints to external tibial rotation. Understanding these specific biomechanical contributions is critical for diagnosing and reconstructing PLC injuries.

Question 84

A 72-year-old female presents with aseptic loosening of her left total hip arthroplasty. Preoperative radiographs and CT scan demonstrate an extensive acetabular defect with complete separation of the superior and inferior halves of the hemipelvis (pelvic discontinuity). The remaining superior iliac bone stock is adequate. Which of the following surgical strategies is most appropriate for establishing long-term durable fixation in this patient?





Explanation

Pelvic discontinuity (Paprosky type 3B variant) occurs when the superior aspect of the pelvis is separated from the inferior aspect. To achieve durable fixation and healing of the discontinuity, modern techniques emphasize biological fixation via "distraction arthroplasty." This involves placing an oversized, highly porous multi-hole hemispherical cup (often tantalum) under tension across the defect, supplemented with multi-screw fixation. Custom triflange components and cup-cage constructs are also viable options, but isolated jumbo cups without treating the discontinuity, impaction grafting, or standard cups with allograft have unacceptably high failure rates in this setting.

Question 85

A 55-year-old patient of Japanese descent presents with progressive clumsiness of the hands and broad-based gait. Cervical imaging confirms ossification of the posterior longitudinal ligament (OPLL). The 'K-line' is determined to be negative. Which of the following surgical approaches is most appropriate for this patient?





Explanation

The K-line is a line drawn from the mid-point of the spinal canal at C2 to the mid-point of the spinal canal at C7 on a lateral radiograph. A "K-line negative" cervical spine means the OPLL mass crosses (extends posterior to) this line, typically due to a massive OPLL or cervical kyphosis. In a K-line negative spine, posterior decompression (laminectomy or laminoplasty) will fail because the spinal cord remains draped over the anterior pathology and cannot adequately shift posteriorly. Therefore, an anterior approach (such as corpectomy and fusion) or a combined anterior-posterior approach is required.

Question 86

In the surgical management of a 'terrible triad' injury of the elbow (elbow dislocation, radial head fracture, and coronoid fracture), standard algorithmic principles dictate a specific sequence of repair. Following surgical approach, which of the following is the generally recommended sequence for reconstruction?





Explanation

The standard surgical algorithm for a terrible triad of the elbow proceeds from deep to superficial, or medial/anterior to lateral, via a lateral approach. The correct sequence is: 1) Coronoid fracture fixation (or anterior capsule repair if the fragment is too small), 2) Radial head fixation or arthroplasty, and 3) LCL complex repair to the lateral epicondyle. If the elbow remains unstable after this sequence, MCL repair or a hinged external fixator is considered.

Question 87

A 6-year-old child with a known diagnosis of Morquio syndrome (Mucopolysaccharidosis type IV) presents for orthopedic evaluation prior to tonsillectomy. Which of the following cervical spine abnormalities is the most critical to evaluate with flexion-extension radiographs in this patient?





Explanation

Morquio syndrome (MPS IV) is caused by a deficiency in N-acetylgalactosamine-6-sulfatase. Patients have severe skeletal dysplasia but normal intelligence. The most lethal orthopedic manifestation is atlantoaxial instability secondary to odontoid hypoplasia (and ligamentous laxity). They are at high risk of sudden myelopathy or death, particularly during intubation/anesthesia, making preoperative flexion-extension radiographs and potential prophylactic fusion critical.

Question 88

The spring ligament complex is a critical static stabilizer of the medial longitudinal arch of the foot. Which of its distinct anatomic fascicles is the strongest and provides the most significant structural support to the talar head?





Explanation

The spring ligament (plantar calcaneonavicular ligament) complex has three main distinct components: superomedial, inferoplantar, and medioplantar. The superomedial calcaneonavicular ligament is the thickest, widest, and most important fascicle. It provides the primary hammock-like support beneath the talar head and is commonly attenuated or ruptured in adult acquired flatfoot deformity (posterior tibial tendon dysfunction).

Question 89

A 28-year-old male sustains a vertically oriented (Pauwels type III) femoral neck fracture. Biomechanical studies have shown that in comparison to three parallel cancellous screws, fixation with a sliding hip screw (fixed-angle device) with a derotational screw offers which primary mechanical advantage?





Explanation

Pauwels type III fractures are high-angle, vertically oriented femoral neck fractures commonly seen in young adults after high-energy trauma. They are highly unstable and subject to significant vertical shear forces during weight-bearing. A sliding hip screw (SHS), combined with a derotational screw, provides a mechanically superior construct by converting shear forces into compressive forces, whereas multiple cancellous screws are more prone to failure (varus collapse) under shear stress.

Question 90

A patient with Marfan syndrome presents with severe back pain and progressive deformity. This condition is caused by a mutation in the FBN1 gene. Which of the following spinal or pelvic conditions is most uniquely characteristic of this specific connective tissue disorder?





Explanation

Marfan syndrome is an autosomal dominant disorder caused by mutations in the fibrillin-1 (FBN1) gene. Classic orthopedic manifestations include arachnodactyly, scoliosis, protrusio acetabuli, and dural ectasia. Dural ectasia (widening of the dural sac, often causing scalloping of the posterior vertebral bodies in the lumbosacral spine) is highly characteristic of Marfan syndrome and is included in the Ghent criteria for its diagnosis.

Question 91

A 45-year-old active male underwent a primary total hip arthroplasty using a ceramic-on-ceramic bearing surface 4 years ago. He now presents with a loud 'squeaking' noise originating from the hip during walking. There is no pain, and inflammatory markers are normal. Radiographic evaluation is most likely to show which of the following component positioning errors?





Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is most strongly associated with component malposition that leads to edge loading and stripe wear. Specifically, excessive cup inclination (steep cup) and excessive anteversion cause the femoral head to load on the edge of the ceramic liner, disrupting fluid film lubrication and generating the characteristic squeaking sound.

Question 92

A 24-year-old cyclist presents with isolated weakness in finger abduction and adduction. Sensation over the entire palmar and dorsal aspects of the small finger and the ulnar half of the ring finger is perfectly preserved. Examination of the wrist flexors is normal. Which zone of Guyon's canal is the most likely site of ulnar nerve compression?





Explanation

Guyon's canal is divided into three zones. Zone 1 is proximal to the bifurcation of the ulnar nerve; compression here causes both motor (intrinsic muscle) and sensory (volar ulnar digits) deficits. Zone 2 surrounds the deep motor branch after it bifurcates; compression here results in isolated motor weakness of the ulnar-innervated intrinsic muscles with NORMAL sensation. Zone 3 surrounds the superficial sensory branch; compression here causes isolated sensory loss. Therefore, this pure motor deficit suggests Zone 2 compression.

Question 93

A 22-year-old female presents with a slowly enlarging, painless mass at the posterior aspect of the distal femur. Radiographs reveal a heavily ossified, dense mass arising from the surface of the bone with a radiolucent 'string sign' separating the mass from the underlying cortex. Biopsy confirms a low-grade malignant bone-forming tumor. Genetic analysis of this tumor is most likely to show amplification of which of the following genes?





Explanation

The clinical and radiographic presentation is classic for a parosteal osteosarcoma (posterior distal femur, dense ossification, low-grade, 'string sign' separating the tumor from the host cortex). Parosteal osteosarcoma and low-grade central osteosarcoma are characterized by supernumerary ring chromosomes leading to the amplification of MDM2 and CDK4 genes on chromosome 12q13-15.

Question 94

An infant is undergoing treatment for developmental dysplasia of the hip (DDH) with a Pavlik harness. During follow-up, the physician notices that the hips have been placed in approximately 130 degrees of flexion. Which of the following complications is most likely to result directly from this specific positioning error?





Explanation

In a Pavlik harness, extreme or excessive hyperflexion (greater than 120 degrees) risks compressing the femoral nerve against the edge of the inguinal ligament, leading to transient femoral nerve palsy (manifesting as decreased active knee extension). Conversely, excessive abduction (not flexion) is the primary risk factor for avascular necrosis of the femoral head. Note: Inferior dislocation can also occur with extreme flexion, but femoral nerve palsy is a highly tested direct neurological consequence of hyperflexion.

Question 95

During the late cocking phase of throwing, a baseball pitcher experiences significant torsional forces at the superior labrum-biceps anchor complex. The biomechanical shift of the biceps vector posteriorly, creating a direct torsional force that detached the labrum, is known as the 'peel-back' mechanism. In a Type II SLAP tear resulting from this mechanism, what is the most significant biomechanical consequence for the glenohumeral joint?





Explanation

The superior labrum and the biceps anchor serve as important stabilizers of the glenohumeral joint. A Type II SLAP tear (detachment of the superior labrum and biceps anchor) secondary to the peel-back mechanism results in loss of this stabilization. Biomechanically, this leads to significantly increased anterior translation (strain on the anterior band of the inferior glenohumeral ligament) when the arm is in the abducted, externally rotated (late cocking) position.

Question 96

A 32-year-old male sustains a high-energy motor vehicle accident resulting in a displaced fracture of the talar neck with associated dislocation of the subtalar, ankle, and talonavicular joints. According to the Hawkins classification, what is the risk of developing avascular necrosis (AVN) of the talar body in this specific injury pattern?





Explanation

This injury is a Hawkins Type III talar neck fracture (fracture with dislocation of the subtalar, tibiotalar/ankle, and talonavicular joints). Because all three primary sources of blood supply to the talar body (artery of the tarsal canal, branches from the dorsalis pedis, and branches from the peroneal artery via the sinus tarsi) are disrupted, the risk of avascular necrosis (AVN) of the talar body is extremely high, nearly always exceeding 90% in large series.

Question 97

In evaluating the long-term survivorship of a new total knee arthroplasty implant via a Kaplan-Meier survivorship curve, how are patients statistically managed if they die from an unrelated myocardial infarction 5 years postoperatively without having required revision surgery?





Explanation

In Kaplan-Meier survival analysis, 'censoring' is used for patients who drop out of the study, are lost to follow-up, or die from causes unrelated to the primary endpoint (e.g., revision surgery). A censored patient contributes to the survival data (denominator) only up to their last known event-free follow-up point. This statistically accounts for their success up to that time without falsely inflating or deflating the overall long-term survival rate.

Question 98

A 40-year-old male sustains a closed, spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture). On initial examination in the emergency department, his radial nerve function is fully intact. A closed reduction and coaptation splinting are performed. Following reduction, the patient presents with an inability to extend his wrist or fingers. What is the most appropriate management regarding the radial nerve?





Explanation

While primary radial nerve palsies present at the time of injury in closed humeral shaft fractures are typically observed, a secondary radial nerve palsy that develops after closed reduction is an absolute indication for immediate surgical exploration. The nerve is at high risk of being entrapped or lacerated within the fracture fragments (particularly in Holstein-Lewis fractures where the nerve is tethered by the lateral intermuscular septum).

Question 99

A 25-year-old patient falls from a height and sustains a vertical sacral fracture. The fracture line passes medial to the sacral foramina, directly involving the central sacral canal. According to the Denis classification, what is the anatomical zone and the corresponding risk of neurologic deficit?





Explanation

The Denis classification of sacral fractures divides them into three zones. Zone I is lateral to the foramina (alar), with the lowest risk of neuro deficit (~5%, typically L5 nerve root). Zone II involves the neural foramina, with an intermediate risk (~28%, typically sciatica/radiculopathy). Zone III involves the central sacral canal (medial to the foramina); these fractures have the highest risk of neurologic deficit (>50%), frequently involving the cauda equina and resulting in bowel, bladder, and sexual dysfunction.

Question 100

A 15-year-old patient with multiple enchondromatosis presents with extensive cartilaginous lesions primarily localized to one side of the body, sparing the soft tissues. Recent literature has identified that the pathogenesis of this syndrome (Ollier disease) is most closely linked to a somatic mosaic mutation in which of the following genes?





Explanation

Ollier disease (multiple enchondromatosis) and Maffucci syndrome (multiple enchondromatosis with soft tissue hemangiomas) are both non-hereditary somatic mosaic disorders. They have been shown to be heavily driven by mutations in the isocitrate dehydrogenase 1 or 2 (IDH1 or IDH2) genes. EXT1 is associated with Multiple Hereditary Exostoses (osteochondromas). GNAS is associated with Fibrous Dysplasia (McCune-Albright). FGFR3 is associated with achondroplasia.

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