+967-774203774 [email protected]
Partner Portal Staff Login
العربية
Part of the Master Guide

Orthopedic Surgery Mock Exam - Set B29D06

Orthopedic Surgery Mock Exam - Set EE0B0A

27 Apr 2026 141 min read 75 Views
Orthopedic Surgery Mock Exam - Set EE0B0A

Key Takeaway

This mock exam provides 50 randomized questions derived from Arab Board and FRCS databanks to perfectly simulate testing environments.

Orthopedic Surgery Mock Exam - Set EE0B0A

Comprehensive 100-Question Exam


00:00

Start Quiz

Question 1

A 25-year-old male presents after a motor vehicle collision. Imaging reveals a traumatic spondylolisthesis of the axis.

Radiographs show a fracture through the pars interarticularis of C2 with severe angulation and minimal translation, without facet dislocation. Applying axial traction causes the fracture gap to widen. Based on the Levine and Edwards classification, what is the most appropriate management?





Explanation

The patient has a Levine-Edwards Type IIA Hangman's fracture, characterized by severe angulation and minimal translation without facet dislocation. Because the mechanism involves flexion-distraction, applying axial traction is contraindicated as it will widen the fracture gap and potentially cause neurologic injury. The appropriate treatment is gentle compression in extension, followed by placement in a halo vest.

Question 2

A 32-year-old male is brought to the trauma bay in hemorrhagic shock after a motorcycle crash. An anteroposterior radiograph of the pelvis demonstrates an APC-III injury.

A pelvic binder is applied. To maximize reduction of the pelvic volume, at what anatomical landmark should the binder be centered?





Explanation

Pelvic binders should be centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests or ASIS can paradoxically widen the true pelvis or fail to achieve adequate reduction in an open-book pelvic injury.

Question 3

Teriparatide is utilized in the management of osteoporosis to stimulate bone formation. Intermittent administration of this parathyroid hormone (PTH) analog exerts its primary anabolic effect by binding to receptors on which of the following cell types?





Explanation

Intermittent administration of parathyroid hormone (PTH) or its analog (teriparatide) exerts a paradoxical anabolic effect on bone by directly binding to PTH1 receptors on osteoblasts, stimulating their proliferation, increasing their lifespan by preventing apoptosis, and increasing bone formation.

Question 4

A 12-year-old obese male presents with left thigh pain and an antalgic gait for 4 weeks. He has been entirely unable to bear weight on the left leg for the past 2 days. Radiographs show a slipped capital femoral epiphysis (SCFE) with a slip angle of 60 degrees.

What is the most significant risk factor for the development of avascular necrosis (AVN) in this patient?





Explanation

The clinical inability to bear weight, even with crutches, defines an unstable SCFE according to the Loder classification. Unstable SCFE carries a significantly higher risk of avascular necrosis (AVN), historically up to 50%, compared to stable SCFE where AVN is rare. While a severe slip angle increases the technical difficulty of fixation, stability is the primary predictor of AVN.

Question 5

A 28-year-old carpenter sustains a volar laceration to his dominant index finger at the level of the proximal phalanx. He is unable to flex the proximal or distal interphalangeal joints. During surgical exploration, the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) are found to be completely transected in Zone II. What is the most appropriate management?





Explanation

In Zone II flexor tendon injuries, the standard of care is primary repair of both the FDP and FDS tendons. Repairing both tendons helps preserve the vincula (blood supply), maintains a smooth gliding surface, reduces the risk of postoperative bowstringing, and generally leads to superior functional outcomes compared to isolated FDP repair.

Question 6

A 72-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Postoperatively, she experiences recurrent posterior dislocations. Radiographic evaluation demonstrates an anteverted cup at 15 degrees and an abduction angle of 40 degrees, with the femoral stem in 5 degrees of retroversion. What is the most likely cause of her instability?





Explanation

Stability in total hip arthroplasty is largely dependent on the combined anteversion of the acetabular and femoral components, which should optimally be between 25 and 35 degrees (Widmer's criteria). In this case, the acetabular cup is anteverted 15 degrees, but the femoral stem is retroverted 5 degrees, resulting in a combined anteversion of only 10 degrees. This relative retroversion significantly increases the risk of posterior dislocation.

Question 7

A 24-year-old football player sustains a hyperplantarflexion injury to his midfoot. Radiographs demonstrate widening of the space between the base of the first and second metatarsals.

Which of the following best describes the anatomy of the primary ligament disrupted in this injury?





Explanation

The Lisfranc ligament is an interosseous ligament located plantarly. It extends from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the largest and strongest of the ligaments supporting the first tarsometatarsal articulation, and its disruption is the hallmark of a Lisfranc injury. There is no direct intermetatarsal ligament between the bases of the first and second metatarsals.

Question 8

A 14-year-old boy presents with right thigh pain and swelling. Radiographs show a permeative, diaphyseal lesion with an 'onion-skin' periosteal reaction. Biopsy reveals uniform small round blue cells. Cytogenetic analysis of this tumor is most likely to demonstrate which of the following translocations?





Explanation

The clinical presentation, radiographic findings ('onion-skin' periostitis), and histology (small round blue cells) are diagnostic of Ewing sarcoma. Over 90% of Ewing sarcomas are characterized by the t(11;22)(q24;q12) chromosomal translocation, which results in the EWS-FLI1 fusion protein. t(X;18) is seen in synovial sarcoma, t(2;13) in alveolar rhabdomyosarcoma, and t(12;16) in myxoid liposarcoma.

Question 9

Sclerostin is a protein that negatively regulates bone formation. Monoclonal antibodies targeting sclerostin (e.g., romosozumab) are utilized in the treatment of severe osteoporosis. Sclerostin exerts its inhibitory effect on osteoblasts primarily by antagonizing which of the following intracellular signaling pathways?





Explanation

Sclerostin is secreted by osteocytes and inhibits bone formation by binding to LRP5/6 receptors on osteoblasts. This binding blocks the coreceptor function of LRP5/6, thereby antagonizing the canonical Wnt/β-catenin signaling pathway, which is essential for osteoblast differentiation and survival.

Question 10

According to recent quantitative anatomical studies utilizing MRI and gadolinium, which of the following vessels provides the principal intraosseous blood supply to the humeral head, challenging historical teachings regarding proximal humerus vascularity?





Explanation

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

Question 11

A 2-week-old infant is undergoing the Ponseti method for the treatment of idiopathic clubfoot. The deformity consists of cavus, adductus, varus, and equinus. In the Ponseti casting technique, the correction of the cavus deformity is achieved first. Which of the following maneuvers is mechanically correct to accomplish this initial step?





Explanation

The cavus deformity in clubfoot is primarily driven by pronation of the forefoot relative to the hindfoot. The first and most critical step in the Ponseti method is to correct the cavus by elevating the first ray (dorsiflexing the first metatarsal), which effectively supinates the forefoot to align it with the midfoot and hindfoot. Subsequent casts correct the adductus and varus by abducting the supinated foot around the stabilized head of the talus.

Question 12

A 25-year-old overhead athlete is diagnosed with a superior labrum anterior and posterior (SLAP) tear after failing nonoperative management.

During diagnostic arthroscopy, which of the following intraoperative findings specifically defines a Type II SLAP tear according to the Snyder classification?





Explanation

In the Snyder classification of SLAP tears: Type I is degenerative fraying of the labrum with an intact biceps anchor. Type II is a frank detachment of the superior labrum and the 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. Type V (an extension of the classification) involves an anteroinferior Bankart lesion extending to the superior labrum.

Question 13

A 55-year-old female undergoes volar locked plating for a comminuted intra-articular distal radius fracture.

Six months postoperatively, she suddenly loses the ability to actively flex the interphalangeal joint of her thumb. What is the most likely pathophysiologic cause of this complication?





Explanation

The inability to actively flex the thumb IP joint several months after volar plating of the distal radius is most commonly due to attritional rupture of the flexor pollicis longus (FPL) tendon. This typically occurs when the volar plate is placed too distally, crossing the 'watershed line' of the distal radius, leading to mechanical friction between the plate edge and the FPL tendon during wrist motion.

Question 14

A 16-year-old gymnast complains of chronic low back pain exacerbated by extension. Radiographs and subsequent MRI show a unilateral pars interarticularis defect at L5 without evidence of spondylolisthesis.

She has failed 6 months of structured conservative management including bracing and physical therapy. She strongly wishes to return to competitive gymnastics. What is the most appropriate surgical intervention?





Explanation

In young, active patients (like athletes) with symptomatic spondylolysis (pars defect) who fail nonoperative treatment and do not have a significant spondylolisthesis, direct pars repair is the procedure of choice. Techniques include the Buck procedure (direct lag screw), Scott wiring, or a pedicle screw-laminar hook construct. This preserves the motion segment and allows a higher rate of return to sports compared to fusion.

Question 15

During the flexion arc of a normal native human knee, the center of rotation of the femur relative to the tibia changes dynamically. Which of the following statements best describes the kinematic phenomenon known as 'femoral rollback'?





Explanation

Femoral rollback is asymmetrical in the native knee. As the knee flexes, the lateral femoral condyle rolls back (translates posteriorly) significantly on the lateral tibial plateau, while the medial femoral condyle remains relatively stationary, acting as a pivot point. This differential rollback inherently couples knee flexion with internal rotation of the tibia relative to the femur.

Question 16

A 19-year-old male presents with severe right thigh pain that is classically worse at night and dramatically relieved by NSAIDs. A CT scan reveals a 7 mm radiolucent nidus surrounded by dense reactive sclerosis in the femoral cortex. What is the most definitive and minimally invasive treatment modality for this condition?





Explanation

The clinical history of night pain relieved by NSAIDs, combined with the CT finding of a radiolucent nidus with surrounding sclerosis, is diagnostic of an osteoid osteoma. CT-guided radiofrequency ablation (RFA) is the standard of care, offering a highly successful, minimally invasive, and definitive treatment, replacing the historical need for surgical en bloc resection.

Question 17

A 55-year-old male with long-standing, poorly controlled type 2 diabetes presents with a warm, swollen, and erythematous left foot.

He denies any recent trauma, fevers, or systemic signs of infection. Plain radiographs show early fragmentation and subluxation of the tarsometatarsal joints. His inflammatory markers are mildly elevated. What is the most appropriate initial management?





Explanation

This patient is presenting with acute Eichenholtz stage I Charcot neuroarthropathy. The foot is acutely inflamed, and initial radiographs show fragmentation. The mainstay of treatment in the acute fragmentation phase is immobilization and strict offloading, ideally utilizing a total contact cast (TCC), to arrest progression of the deformity until the acute inflammatory phase subsides and the bones coalesce.

Question 18

Bone morphogenetic proteins (BMPs) are critical members of the TGF-beta superfamily that induce the differentiation of mesenchymal stem cells into osteoblasts. Which of the following recombinant BMPs is FDA-approved specifically for use in anterior lumbar interbody fusion (ALIF) with a metallic interbody cage?





Explanation

Recombinant human BMP-2 (rhBMP-2, trade name Infuse) is FDA-approved for use in single-level anterior lumbar interbody fusion (ALIF) when used with an approved interbody fusion device. rhBMP-7 (OP-1) was previously approved for recalcitrant long bone nonunions under an HDE but is generally no longer commercially available in the US.

Question 19

A 28-year-old male undergoes reamed intramedullary nailing for a closed comminuted tibial shaft fracture.

In the recovery room, he complains of severe leg pain out of proportion to the injury, unremitting despite high-dose intravenous opioids. Passive stretch of his toes elicits excruciating pain. Intracompartmental pressure testing yields an anterior compartment pressure of 45 mmHg, and his diastolic blood pressure is 65 mmHg. What is the most appropriate next step in management?





Explanation

The patient exhibits classic clinical signs of acute compartment syndrome. The objective threshold for emergent fasciotomy is a delta P (diastolic blood pressure minus compartment pressure) of less than 30 mmHg. In this case, delta P is 20 mmHg (65 - 45 = 20), which is an absolute indication for emergent four-compartment fasciotomy. Elevating the leg above the heart is contraindicated as it reduces arterial perfusion pressure and exacerbates ischemia.

Question 20

A 6-year-old girl falls from monkey bars and sustains a widely displaced extension-type supracondylar fracture of the distal humerus.

On physical examination prior to reduction, she is unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger, resulting in an inability to make an 'A-OK' sign. Which nerve is most likely injured?





Explanation

The anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus (FPL) and the flexor digitorum profundus (FDP) to the index and middle fingers. Injury results in the inability to flex the IP joint of the thumb and DIP joint of the index finger, preventing the patient from making an 'OK' sign.

Question 21

A 58-year-old female presents with groin pain and swelling three years after undergoing a metal-on-metal total hip arthroplasty. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) is suspected.

Which of the following immunologic mechanisms is primarily responsible for the pathogenesis of this condition?





Explanation

ALVAL (Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion) is a classic complication of metal-on-metal implants or corrosion at modular junctions (trunnionosis). It is driven by a Type IV (delayed, T-cell mediated) hypersensitivity reaction to metal ions (like cobalt and chromium). Histologically, it is characterized by a perivascular lymphocytic infiltrate. This distinguishes it from classic polyethylene wear debris, which is characterized by a macrophage-mediated foreign body response.

Question 22

An 8-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During the weekly clinical check, the orthopedic surgeon assesses the harness fit to prevent complications. Which of the following strap misadjustments most directly places the infant at risk for avascular necrosis (AVN) of the femoral head?





Explanation

In the Pavlik harness, excessive abduction (too tight posterior straps) forces the femoral head into rigid abduction, creating high pressure that compresses the epiphyseal blood vessels (primarily branches of the medial circumflex femoral artery), leading to AVN of the femoral head. Conversely, excessive flexion (too tight anterior straps) puts the infant at risk for transient femoral nerve palsy.

Question 23

A 35-year-old male is involved in a high-speed motor vehicle collision. Lateral cervical spine radiographs and CT reveal a Levine-Edwards Type IIA traumatic spondylolisthesis of the axis (Hangman's fracture).

What is the primary mechanism of injury for this specific fracture subtype?





Explanation

The Levine-Edwards classification for Hangman's fractures (traumatic spondylolisthesis of the axis) is based on mechanism. Type I is hyperextension-axial loading. Type II is hyperextension-axial loading followed by severe flexion. Type IIA is flexion-distraction, characterized by minimal translation but severe angulation, and the disc space is often widened posteriorly. Type IIA fractures are unstable in traction, which is a critical clinical pearl; traction will exacerbate the deformity. Type III is flexion-compression.

Question 24

The posterior cruciate ligament (PCL) is composed of two primary bundles. Which of the following accurately describes the biomechanical behavior of the anterolateral (AL) and posteromedial (PM) bundles during knee range of motion?





Explanation

The PCL consists of the larger anterolateral (AL) bundle and the smaller posteromedial (PM) bundle. Biomechanically, the AL bundle is tightest in knee flexion and lax in extension. Conversely, the PM bundle is tightest in knee extension and lax in flexion. This reciprocal relationship is vital to understanding PCL reconstruction biomechanics.

Question 25

A 40-year-old gymnast falls on an outstretched hand, sustaining a 'Terrible Triad' injury of the elbow.

According to standard surgical protocols (e.g., Pugh and McKee), which of the following is the generally recommended sequence of surgical reconstruction to restore stability?





Explanation

The classic 'Terrible Triad' of the elbow includes an elbow dislocation, radial head fracture, and coronoid fracture. The standard inside-out surgical algorithm established by Pugh et al. starts deep/anterior and moves lateral: 1) Fixation or reconstruction of the coronoid process, 2) Fixation or replacement of the radial head, 3) Repair of the lateral collateral ligament (LCL) complex to the lateral epicondyle. If the elbow remains unstable after these steps, 4) Repair of the medial collateral ligament (MCL) or application of a hinged external fixator is indicated.

Question 26

A 55-year-old male presents with deep thigh pain. Radiographs reveal a permeative radiolucent lesion in the proximal femur with 'popcorn' calcifications. Core needle biopsy demonstrates a hypercellular hyaline cartilage tumor with nuclear atypia and binucleated cells, consistent with Grade II conventional chondrosarcoma. What is the most appropriate management?





Explanation

Conventional chondrosarcoma is notably resistant to both chemotherapy and radiation therapy due to its poor vascularity, slow division rate, and extracellular matrix properties. The mainstay of treatment for intermediate-grade (Grade II) and high-grade (Grade III) chondrosarcoma is wide local excision (en bloc resection) with negative margins. Intralesional curettage is only acceptable for Grade I (atypical cartilaginous tumors) in the appendicular skeleton.

Question 27

A 60-year-old male with poorly controlled diabetes presents with a swollen, warm, and minimally painful foot. Radiographs are obtained to evaluate for Charcot neuroarthropathy.

According to the Eichenholtz classification, which of the following clinical and radiographic findings is characteristic of Stage II (Coalescence)?





Explanation

The Eichenholtz classification of Charcot neuroarthropathy includes: Stage 0 (Pre-radiographic): erythema, swelling, warmth, normal X-rays. Stage I (Development/Fragmentation): joint destruction, subluxation, fragmentation, and debris. Stage II (Coalescence): decreased warmth/swelling, absorption of fine debris, early sclerosis, and fracture healing. Stage III (Remodeling): consolidated fractures, rounded bone ends, osteophyte formation, and fixed residual deformity.

Question 28

During a primary total knee arthroplasty, trial components are placed, and gap balancing is assessed. The knee is found to be tight in 90 degrees of flexion but perfectly balanced in full extension. Which of the following femoral component adjustments will best correct this specific imbalance?





Explanation

In TKA gap balancing, the flexion gap is primarily controlled by the anteroposterior (AP) dimension of the femoral component, while the extension gap is controlled by the distal femoral resection. If the knee is tight in flexion but balanced in extension, the flexion gap needs to be increased without affecting the extension gap. Downsizing the femoral component decreases its AP dimension (specifically taking more posterior condyle), which opens up the flexion gap while leaving the extension gap unchanged.

Question 29

Bone morphogenetic proteins (BMPs) play a critical role in osteoinduction and bone healing. Recombinant human BMP-2 (rhBMP-2) is utilized in various spine and orthopedic trauma procedures. Upon binding to its transmembrane serine/threonine kinase receptor, which intracellular signaling pathway is primarily activated by BMP-2?





Explanation

BMP-2 and BMP-7 act via cell surface receptors that have intrinsic serine/threonine kinase activity. Once activated, these receptors phosphorylate the intracellular R-Smads (Receptor-regulated Smads), specifically Smad 1, Smad 5, and Smad 8. These complex with Co-Smad (Smad 4) to translocate to the nucleus and induce osteogenic gene transcription. Smad 2 and 3 are primarily associated with the TGF-beta signaling pathway, not BMP.

Question 30

A 45-year-old male is struck by a vehicle and sustains a complex tibial plateau fracture.

The injury is classified as a Schatzker Type IV fracture. What is the classic mechanism of injury, and which surgical approach is most commonly required for anatomic reduction and buttressing of this specific pattern?





Explanation

Schatzker Type IV represents a medial tibial plateau fracture, classically caused by a high-energy varus force combined with axial loading. Because the medial plateau is dense and strong, this fracture implies high energy and often subluxation/dislocation of the knee joint. The optimal surgical approach involves buttressing the medial fragment, which is best achieved via a posteromedial approach to place an anti-glide or buttress plate.

Question 31

An infant is born with idiopathic congenital talipes equinovarus (clubfoot) and is referred for Ponseti serial casting. According to the Ponseti method, what is the first step in the manual manipulation and casting sequence to correct the deformities?





Explanation

The Ponseti method corrects clubfoot deformities in a specific sequence remembered by the acronym CAVE: Cavus, Adductus, Varus, Equinus. The very first step is to correct the cavus deformity by supinating the forefoot and elevating the first metatarsal (first ray) to align the forefoot with the hindfoot. Abduction of the midfoot with counter-pressure on the head of the talus (not calcaneocuboid joint) then corrects the adductus and varus simultaneously.

Question 32

A 28-year-old male presents after an unprovoked seizure. He complains of right shoulder pain and is unable to externally rotate his arm. Imaging confirms a posterior shoulder dislocation. Further evaluation reveals an impaction fracture of the humeral head known as a reverse Hill-Sachs lesion. Where is this articular defect classically located?





Explanation

A posterior shoulder dislocation commonly results in an impaction fracture of the humeral head as it is driven against the posterior glenoid rim. This defect is known as a reverse Hill-Sachs lesion and is classically located on the anteromedial aspect of the humeral head. In contrast, an anterior dislocation produces a standard Hill-Sachs lesion, which is located on the posterolateral aspect of the humeral head.

Question 33

A 24-year-old carpenter sustains a volar laceration to the index finger at the level of the proximal phalanx, resulting in a Zone II flexor tendon injury. During primary repair, the surgeon carefully preserves the flexor tendon sheath pulleys. Which two pulleys are most biomechanically critical to prevent bowstringing of the flexor tendons?





Explanation

In the flexor tendon pulley system of the fingers, there are 5 annular (A) and 3 cruciform (C) pulleys. The A2 pulley (located over the proximal phalanx) and the A4 pulley (located over the middle phalanx) are the major mechanical pulleys. Preservation or reconstruction of the A2 and A4 pulleys is absolutely critical to prevent bowstringing of the flexor tendons, which would cause significant loss of mechanical advantage and active range of motion.

Question 34

A 45-year-old male presents with severe, radiating leg pain. An MRI of the lumbar spine is obtained.

Imaging demonstrates a 'far lateral' (extraforaminal) disc herniation at the L4-L5 level. Which nerve root is most likely to be directly compressed by this specific type of herniation?





Explanation

In the lumbar spine, a classic posterolateral (paracentral) disc herniation affects the traversing nerve root (e.g., L4-L5 disc affects the L5 root). However, a 'far lateral' or extraforaminal disc herniation affects the exiting nerve root at that same level. Therefore, a far lateral disc herniation at L4-L5 will compress the exiting L4 nerve root, causing weakness in knee extension and anterior thigh pain.

Question 35

During normal human gait, the muscles of the lower extremity exhibit highly coordinated, phased activity. Peak concentric contraction and maximal electromyographic (EMG) activity of the gastrocnemius-soleus complex occurs during which specific phase of the gait cycle?





Explanation

The gastrocnemius-soleus complex is crucial for ankle plantarflexion. During mid stance, the triceps surae contracts eccentrically to control the forward progression of the tibia over the fixed foot (controlling ankle dorsiflexion). Its peak electrical activity and maximal concentric contraction occur during terminal stance (heel off) to provide the active push-off required for forward propulsion, right before pre-swing.

Question 36

A 22-year-old male is brought to the trauma bay after a motorcycle accident. Pelvic radiographs demonstrate significant widening of the pubic symphysis, indicative of an anteroposterior compression (APC) injury.

To classify this as an APC Type III injury (Young-Burgess classification), which of the following combinations of posterior pelvic ring ligaments must be completely disrupted?





Explanation

In the Young-Burgess classification, APC I involves symphysis widening <2.5 cm with intact posterior ligaments. APC II involves symphysis widening >2.5 cm, disruption of the anterior sacroiliac, sacrospinous, and sacrotuberous ligaments, but the critical posterior sacroiliac (SI) ligaments remain intact (rotationally unstable, vertically stable). APC III indicates complete disruption of the anterior SI, sacrospinous, sacrotuberous, AND the posterior SI ligaments, resulting in a completely unstable hemipelvis (both rotationally and vertically).

Question 37

A 35-year-old recreational athlete undergoes percutaneous repair of an acute Achilles tendon rupture. During passage of the proximal transverse sutures, a nerve is inadvertently entrapped. Which nerve is at greatest risk during this procedure, and what is its normal anatomic relationship to the Achilles tendon insertion?





Explanation

The sural nerve is at the greatest risk of iatrogenic injury during percutaneous or minimally invasive Achilles tendon repair, particularly during the placement of proximal, lateral sutures. Anatomically, the sural nerve travels distally in the posterior calf and classically crosses the lateral border of the Achilles tendon from medial to lateral at an average of 9.8 cm (approximately 10 cm) proximal to the calcaneal insertion.

Question 38

A 16-year-old male presents with a persistent, dull ache in his right tibia that is significantly worse at night. The pain is rapidly and completely relieved by ibuprofen. Imaging demonstrates a cortical thickening with a small (<1.5 cm) radiolucent nidus. What is the primary biochemical mechanism driving this patient's nocturnal pain?





Explanation

The clinical presentation is classic for an osteoid osteoma. The pathognomonic symptom is severe, unrelenting night pain that is exquisitely responsive to nonsteroidal anti-inflammatory drugs (NSAIDs) or salicylates. This is because the cells within the nidus (active osteoblasts) contain very high levels of cyclooxygenase-2 (COX-2) and produce massive amounts of prostaglandin E2 (PGE2). PGE2 induces intense local vasodilation and directly stimulates local nerve endings.

Question 39

A 65-year-old patient complains of an audible "squeaking" sound from her total hip arthroplasty, which utilizes a ceramic-on-ceramic bearing surface. What surgical or mechanical factor is most strongly associated with the initiation of squeaking in modern ceramic-on-ceramic hips?





Explanation

Squeaking is a known complication unique to hard-on-hard bearing surfaces, most notably alumina ceramic-on-ceramic THA. The primary mechanical etiology is stripe wear caused by micro-separation during the swing phase of gait, leading to edge-loading when the head re-engages the rim of the cup. This is strongly associated with component malpositioning (particularly excessive cup anteversion or high inclination angles) that disrupts fluid film lubrication.

Question 40

A healthy, highly active 40-year-old male falls from a ladder and sustains a displaced intracapsular fracture of the femoral neck (Garden IV). He is brought to the emergency department within 4 hours of the injury. What is the most appropriate surgical management for this specific patient?





Explanation

In a young, physiologically active patient (generally <60-65 years old), a displaced femoral neck fracture is an orthopedic urgency. The goal is head preservation despite the high risk of avascular necrosis (AVN) and nonunion. The standard of care is urgent closed or open reduction and internal fixation (using cannulated screws or a sliding hip screw device) to restore the native anatomy. Arthroplasty (hemi or THA) is reserved for older, lower-demand patients or cases of delayed presentation where head salvage is impossible.

Question 41

A 72-year-old male presents with recurrent posterior dislocations following a right total hip arthroplasty performed 2 months ago via a posterior approach. Radiographs show a well-fixed femoral stem and an acetabular component with 10 degrees of anteversion and 45 degrees of abduction. During revision surgery, the acetabular component is found to be solidly ingrown. Which of the following is the most appropriate surgical intervention to prevent further posterior dislocations?





Explanation

The ideal acetabular cup position in total hip arthroplasty is generally considered to be 15 to 20 degrees of anteversion and 40 to 45 degrees of abduction. An anteversion of 10 degrees is relatively retroverted, especially when a posterior approach is used, predisposing the patient to posterior instability. Since the cup is malpositioned, the most appropriate treatment is revision of the acetabular shell to correct the anteversion.

Question 42

A 45-year-old male sustains a Schatzker IV tibial plateau fracture with a large posteromedial shear fragment.

He is scheduled for open reduction and internal fixation. A posteromedial surgical approach is planned. To safely access the fracture fragment, the surgical interval is developed between which of the following structures?





Explanation

The posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (which is retracted laterally/posteriorly) and the pes anserinus tendons (which are retracted anteriorly/medially). This provides excellent direct access to posteromedial shear fragments for buttress plating.

Question 43

A 68-year-old male presents with progressive hand clumsiness and gait imbalance over the past year. Examination reveals a positive Hoffmann sign bilaterally and hyperreflexia in the lower extremities. MRI of the cervical spine demonstrates severe spinal canal stenosis at C4-C5 and C5-C6. Which of the following specific MRI findings in the spinal cord is most strongly associated with a poor prognosis for neurologic recovery following surgical decompression?





Explanation

In cervical spondylotic myelopathy, the presence of T1 hypointensity combined with T2 hyperintensity in the spinal cord indicates myelomalacia (permanent cystic necrosis/gliosis of the cord). This finding is strongly correlated with a poor prognosis for neurologic recovery even after adequate surgical decompression. T2 hyperintensity alone may indicate reversible edema.

Question 44

A 24-year-old man sustains a proximal pole scaphoid fracture after a fall on an outstretched hand. He is counseled regarding the high risk of nonunion and avascular necrosis associated with this specific fracture pattern. Which of the following accurately describes the primary blood supply to the proximal pole of the scaphoid?





Explanation

The scaphoid receives its primary blood supply from the dorsal carpal branch of the radial artery, which enters the bone distally and provides retrograde blood flow to the proximal pole. This retrograde supply makes proximal pole fractures particularly vulnerable to avascular necrosis and nonunion.

Question 45

A 12-year-old boy with a BMI of 32 presents with a 4-week history of vague left knee pain and an antalgic gait. Radiographs reveal a mild, stable slipped capital femoral epiphysis (SCFE) of the left hip.

He is taken to the operating room for in situ pinning. To minimize the risk of joint penetration and adequately stabilize the epiphysis, the starting point for the screw should be located on the:





Explanation

In a slipped capital femoral epiphysis, the epiphysis displaces posteriorly and inferiorly relative to the femoral neck. To correctly trajectory a single screw perpendicular to the physis and into the center of the displaced epiphysis without violating the posterior cortex of the femoral neck, an anterior and superior starting point on the metaphysis/neck is required.

Question 46

A 35-year-old male sustains a transverse midshaft radius fracture. He undergoes open reduction and internal fixation with a 3.5 mm dynamic compression plate placed in absolute stability. Which of the following best describes the predominant mechanism of bone healing expected in this scenario?





Explanation

Absolute stability (rigid fixation with anatomic reduction and no gap) eliminates interfragmentary strain, bypassing callus formation. It leads to primary (direct) bone healing, which occurs via Haversian remodeling driven by osteoclast-led cutting cones followed immediately by osteoblasts laying down new bone.

Question 47

A 42-year-old recreational athlete sustains an acute, complete rupture of the Achilles tendon. He opts for non-operative management and is enrolled in a functional rehabilitation protocol featuring early weight-bearing in a functional brace. Compared to traditional management involving prolonged non-weight-bearing cast immobilization, functional rehabilitation is associated with:





Explanation

Recent high-level evidence demonstrates that for acute Achilles tendon ruptures, non-operative management utilizing an early functional rehabilitation protocol (early weight-bearing and controlled range of motion in a brace) provides similar rerupture rates to surgical repair and traditional casting, while improving early functional outcomes, reducing DVT risk, and expediting return to work compared to prolonged immobilization.

Question 48

A 20-year-old collegiate female basketball player undergoes an anterior cruciate ligament reconstruction using a bone-patellar tendon-bone (BTB) autograft. She successfully completes rehabilitation and returns to play at 9 months. Which of the following is the most commonly reported complication specifically associated with this choice of graft compared to hamstring autograft?





Explanation

The most common and specific complication associated with the use of a bone-patellar tendon-bone (BTB) autograft is donor site morbidity, manifesting primarily as anterior knee pain and pain with kneeling. Saphenous nerve injury and hamstring weakness are more commonly associated with hamstring autografts.

Question 49

A 14-year-old boy presents with worsening knee pain and swelling. Radiographs demonstrate a mixed lytic and sclerotic lesion in the distal femoral metaphysis with a 'sunburst' periosteal reaction. Biopsy confirms a high-grade intramedullary osteosarcoma. Which of the following represents the standard, most appropriate treatment algorithm for this patient?





Explanation

The standard of care for high-grade conventional intramedullary osteosarcoma is multi-agent neoadjuvant chemotherapy, followed by definitive surgical local control (limb-salvage wide resection or amputation), and concluding with adjuvant chemotherapy. Osteosarcoma is generally considered radioresistant, so radiation therapy is not a primary modality unless the tumor is unresectable.

Question 50

A 28-year-old motorcyclist is involved in a high-speed collision and sustains an anterior-posterior compression (APC) type III pelvic ring injury. According to the Young-Burgess classification, this injury pattern is characterized by the complete disruption of the symphysis pubis and which of the following posterior ligamentous complexes?





Explanation

An APC III pelvic injury involves complete disruption of both the anterior and posterior pelvic rings. This includes the symphysis pubis anteriorly, and all of the posterior ligamentous structures: the anterior sacroiliac ligaments, the pelvic floor ligaments (sacrospinous and sacrotuberous), and the strong posterior sacroiliac ligaments, leading to complete global instability of the hemipelvis.

Question 51

A 58-year-old male with a history of a metal-on-metal total hip arthroplasty performed 8 years ago presents with progressive groin pain and swelling. Laboratory evaluation reveals significantly elevated serum cobalt and chromium ion levels. MRI demonstrates a large, thick-walled fluid collection. Histologic analysis of the periprosthetic tissue is most likely to show an adverse local tissue reaction (ALVAL) characterized by:





Explanation

Adverse Local Tissue Reaction (ALTR) or Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL) in response to metal wear debris from metal-on-metal implants is histologically characterized by a dense perivascular lymphocytic infiltrate. This represents a Type IV (cell-mediated) delayed hypersensitivity reaction to metal ions.

Question 52

A 30-year-old carpenter sustains a laceration to his dominant index finger, resulting in a Zone II injury of both the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP). Postoperatively, the hand therapist initiates an early active motion rehabilitation protocol. The primary rationale for utilizing early active motion over prolonged immobilization in this specific scenario is to:





Explanation

Early active or passive motion protocols following flexor tendon repair in Zone II are critical to facilitate intrinsic tendon healing and promote tendon glide. This movement helps prevent the formation of restrictive peritendinous adhesions (which limit excursion) while providing enough controlled stress to stimulate healing without rupturing the repair.

Question 53

A 75-year-old male with severe neurogenic claudication secondary to multilevel lumbar spinal stenosis is considering surgical intervention after failing 6 months of conservative treatment. Which of the following preoperative clinical features is most predictive of a highly successful outcome following a lumbar laminectomy and decompression?





Explanation

In patients with lumbar spinal stenosis, decompression surgery (laminectomy) is highly effective at relieving radicular leg pain and neurogenic claudication. Patients whose primary complaint is axial back pain often have poorer outcomes, as decompression alone does not address back pain reliably.

Question 54

A 7-month-old female infant is evaluated for developmental dysplasia of the hip (DDH). She was initially treated with a Pavlik harness starting at 6 weeks of age, but the hip remained irreducible. Subsequent attempts at weaning and re-application have failed. Radiographs show a persistently dislocated left hip with acetabular dysplasia. What is the most appropriate next step in management?





Explanation

If Pavlik harness treatment fails to achieve or maintain a reduction in an infant with DDH, the harness should be discontinued to avoid 'Pavlik harness disease' (damage to the posterior acetabular wall) and AVN. The next definitive step in management for a child typically between 6 and 18 months of age is closed reduction under general anesthesia followed by spica casting.

Question 55

A 25-year-old athlete sustains a midfoot injury after a forceful plantarflexion mechanism.

Radiographs demonstrate widening of the space between the base of the first and second metatarsals. MRI confirms a complete rupture of the Lisfranc ligament. Anatomically, the Lisfranc ligament is an interosseous ligament that connects the:





Explanation

The Lisfranc ligament is a strong interosseous ligament that originates from the lateral aspect of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal. It is a critical stabilizer of the tarsometatarsal joint complex.

Question 56

Articular cartilage is a highly specialized tissue designed to withstand significant compressive loads. The mechanical properties of cartilage vary across its depth. Which of the following correctly describes the biochemical composition of the deep zone of articular cartilage?





Explanation

Articular cartilage composition varies by zone. The superficial zone has the highest water content and lowest proteoglycan content. In contrast, the deep zone has the lowest water content and the highest concentration of proteoglycans, allowing it to provide maximal resistance to compressive forces.

Question 57

A 22-year-old male undergoes arthroscopic evaluation of the knee for a medial meniscus tear. The surgeon must decide between meniscal repair and partial meniscectomy. The potential for meniscal healing is primarily dictated by its vascular supply. Which area of the meniscus possesses the greatest intrinsic potential for healing following surgical repair?





Explanation

The vascular supply to the meniscus originates from the perimeniscal capillary plexus, which supplies only the peripheral 10% to 30% of the meniscus. Tears in this peripheral third (the 'red-red' zone) have robust blood supply and the highest potential for healing following surgical repair.

Question 58

A 32-year-old female presents with a 3-month history of progressive left knee pain. Radiographs reveal an expansile, purely lytic lesion in the epiphysis of the proximal tibia, extending to the subchondral bone. A biopsy confirms the diagnosis of a Giant Cell Tumor (GCT) of bone. Staging workup is negative for metastases. Which of the following is the most appropriate primary surgical treatment?





Explanation

Giant cell tumors of bone are locally aggressive benign tumors. The standard treatment to minimize the risk of local recurrence while preserving joint function is extended intralesional curettage (using a high-speed burr), followed by the application of local adjuvants (such as phenol, argon beam, or hydrogen peroxide) to kill remaining microscopic disease, and filling the defect with bone graft or PMMA cement.

Question 59

A 26-year-old male is admitted after sustaining a severely comminuted, closed fracture of the tibial shaft. He develops escalating leg pain out of proportion to his injury. Examination reveals tense compartments and pain with passive stretch of the toes. Intracompartmental pressure testing is performed. Which of the following pressure measurements (Delta P = Diastolic Blood Pressure - Compartment Pressure) is widely considered the absolute indication for emergent fasciotomy?





Explanation

The diagnosis of acute compartment syndrome is primarily clinical, but when objective measurements are needed, the 'Delta P' is used. A Delta P (diastolic blood pressure minus intracompartmental pressure) of less than 30 mmHg indicates inadequate tissue perfusion and is a universally accepted absolute indication for emergent fasciotomy.

Question 60

A 68-year-old female is undergoing a primary posterior-stabilized total knee arthroplasty. During trialing, the surgeon notes that the knee is perfectly balanced in full extension, but the flexion gap is unacceptably tight, limiting flexion to 80 degrees and causing posterior lift-off of the tibial tray. Which of the following surgical adjustments is the most appropriate maneuver to balance the knee?





Explanation

A tight flexion gap with a balanced extension gap means the AP dimension of the femoral component is too large, or the posterior tibial slope is inadequate. Downsizing the femoral component (when using an anterior referencing system) reduces the posterior condylar offset, thereby specifically opening the flexion gap without affecting the extension gap. Increasing (not decreasing) the posterior tibial slope would also be an option.

Question 61

A 65-year-old male is undergoing a total hip arthroplasty via the direct anterior approach. Which of the following best describes the deep internervous plane utilized during this approach?





Explanation

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

Question 62

A 45-year-old male sustains a complex tibial plateau fracture involving a displaced posteromedial fragment. The surgeon elects to use a posteromedial approach for open reduction and internal fixation. This approach utilizes an interval between which of the following structures?





Explanation

The posteromedial approach to the proximal tibia is the standard approach for addressing posteromedial shear fragments in tibial plateau fractures. The surgical interval exploits the space between the medial head of the gastrocnemius (which is retracted laterally) and the pes anserinus tendons (which are retracted medially and anteriorly).

Question 63

Bone morphogenetic proteins (BMPs) are members of the TGF-beta superfamily. Recombinant human BMP-2 (rhBMP-2) has been approved by the FDA for specific clinical applications. Which of the following is an FDA-approved indication for the use of rhBMP-2?





Explanation

rhBMP-2 (Infuse) is FDA-approved for the treatment of acute, open tibial shaft fractures stabilized with an intramedullary nail within 14 days of injury, as well as for anterior lumbar interbody fusion (ALIF). Recombinant human BMP-7 (OP-1) was historically approved for long bone nonunions and revision posterolateral lumbar fusion, though its availability has changed.

Question 64

A 9-year-old boy presents with right hip pain and a limp. Radiographs confirm a slipped capital femoral epiphysis (SCFE). His weight is in the 40th percentile for his age. In addition to in situ pinning of the right hip, which of the following is the most appropriate next step in management?





Explanation

SCFE typically affects obese adolescents between the ages of 10 and 16. Atypical presentations include patients younger than 10 or older than 16, those with a weight less than the 50th percentile, and those with bilateral involvement at presentation. These atypical presentations strongly warrant an endocrine and metabolic workup to rule out underlying disorders such as hypothyroidism or renal osteodystrophy.

Question 65

A 24-year-old man falls onto an outstretched hand and sustains an acute, minimally displaced fracture of the proximal pole of the scaphoid. Because of the specific vascular anatomy of the scaphoid, which of the following is the most widely recommended treatment for this injury?





Explanation

The blood supply to the scaphoid enters distally via branches of the radial artery and flows retrograde to the proximal pole. Because of this tenuous vascular supply, proximal pole fractures have a very high rate of nonunion and avascular necrosis. Operative fixation (percutaneous or open) is recommended even for non-displaced proximal pole fractures to optimize the biomechanical environment for healing.

Question 66

Following an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, a patient exhibits a lack of full knee flexion but achieves full extension. The physical examination reveals a tight graft in flexion. Which of the following technical errors during graft placement most likely accounts for this finding?





Explanation

Placement of the femoral tunnel in ACL reconstruction is critical for graft isometry. If the femoral tunnel is placed too anteriorly, the distance between the femoral and tibial origins increases as the knee flexes. This results in a graft that is tight in flexion (causing loss of flexion) and lax in extension.

Question 67

A 16-year-old female with a diagnosis of Charcot-Marie-Tooth disease presents with a progressive, symptomatic cavovarus foot deformity. During clinical evaluation, her first ray is noted to be rigidly plantarflexed. This specific component of her deformity is primarily driven by the unopposed action of which muscle?





Explanation

In Charcot-Marie-Tooth (CMT) disease, the classic cavovarus foot deformity is driven by specific muscle imbalances. The tibialis anterior and peroneus brevis weaken early. The relatively preserved strength of the peroneus longus, which is unopposed by the weak tibialis anterior, powerfully plantarflexes the first ray, causing the forefoot-driven cavus deformity.

Question 68

A 65-year-old male presents with deteriorating hand dexterity and gait imbalance. On physical examination, tapping the distal brachioradialis tendon results in diminished reflex elbow flexion, but elicits spontaneous flexion of the ipsilateral fingers. This physical exam finding localizes the spinal cord pathology to which of the following levels?





Explanation

The inverted brachioradialis reflex is a specific clinical sign for cervical spondylotic myelopathy. It consists of an absent or diminished brachioradialis reflex (a lower motor neuron finding at C5-C6) coupled with hyperactive finger flexion (an upper motor neuron finding for levels below C6). This combination localizes the primary compressive pathology to the C5-C6 level.

Question 69

A 14-year-old boy presents with progressive knee pain and swelling. Radiographs reveal a poorly marginated, bone-forming lesion in the distal femoral metaphysis with elevation of the periosteum forming a Codman's triangle.

A biopsy confirms conventional osteosarcoma. Mutations in which of the following pairs of tumor suppressor genes are most commonly implicated in the pathogenesis of this condition?





Explanation

Conventional osteosarcoma is highly malignant and characterized by the production of osteoid by tumor cells. The pathogenesis is strongly associated with mutations in the RB1 (retinoblastoma) and TP53 (p53) tumor suppressor genes. Patients with hereditary retinoblastoma or Li-Fraumeni syndrome (germline TP53 mutation) have a significantly increased risk of developing osteosarcoma.

Question 70

In the context of wear mechanisms in total joint arthroplasty, the generation of wear debris between the non-articulating backside of a polyethylene acetabular liner and the inner surface of a metallic acetabular shell is classified as which of the following?





Explanation

Wear in total joint arthroplasty is categorized into four modes. Mode I occurs between two intended bearing surfaces (e.g., femoral head and polyethylene liner). Mode II occurs when a primary bearing surface rubs against a non-intended secondary surface (e.g., femoral head against metallic shell after liner wear-through). Mode III is third-body wear caused by loose particles. Mode IV wear occurs between two non-primary bearing surfaces rubbing against each other, such as backside wear between the polyethylene liner and the metallic acetabular shell.

Question 71

A trauma surgeon is performing an ilioinguinal approach to the anterior pelvis for the fixation of an anterior column acetabular fracture. During dissection over the superior pubic ramus, brisk arterial bleeding is encountered. This bleeding is most likely originating from an anastomosis between the obturator vessels and branches of which of the following?





Explanation

The 'corona mortis' (crown of death) is an important vascular anastomosis located over the posterior aspect of the superior pubic ramus, approximately 5-6 cm lateral to the pubic symphysis. It connects the obturator system (internal iliac system) with the external iliac or inferior epigastric vessels. It is vulnerable to injury during anterior pelvic approaches and can cause significant hemorrhage.

Question 72

A 2-week-old infant is brought to the clinic for management of a rigid idiopathic clubfoot using the Ponseti method. What is the essential first maneuver performed during the application of the initial corrective cast?





Explanation

The Ponseti method addresses clubfoot deformity in a specific sequence (CAVE: Cavus, Adductus, Varus, Equinus). The first step is to correct the cavus deformity. This is achieved by supinating the forefoot (specifically elevating the first ray) to align the forefoot with the already pronated hindfoot. Subsequent casts correct adductus and varus by laterally directing the forefoot against the talar head, and equinus is corrected last (often requiring a percutaneous Achilles tenotomy).

Question 73

The 'glenoid track' concept is utilized to evaluate bipolar bone loss in anterior shoulder instability. A Hill-Sachs lesion is considered 'off-track' and at risk for engaging the anterior glenoid rim if its medial margin is located where?





Explanation

The glenoid track represents the contact zone of the glenoid on the humeral head during shoulder abduction and external rotation. Its width is determined by the native glenoid width minus the anterior glenoid bone loss. A Hill-Sachs lesion is 'off-track' (meaning it will engage the anterior glenoid rim, leading to dislocation) if the medial margin of the lesion extends medial to the medial margin of the calculated glenoid track.

Question 74

A 32-year-old mechanic sustains a volar laceration to his middle finger at the level of the proximal phalanx, resulting in a loss of active flexion at both the proximal and distal interphalangeal joints. This injury is located within which flexor tendon zone?





Explanation

Verdan's flexor tendon zones classify the anatomical locations of flexor tendon injuries. Zone II (historically called 'no man's land' due to historically poor surgical outcomes) extends from the proximal aspect of the A1 pulley (distal palmar crease) to the insertion of the flexor digitorum superficialis (FDS) on the middle phalanx. Lacerations here frequently involve both the FDS and flexor digitorum profundus (FDP) tendons within the tight fibro-osseous sheath.

Question 75

The Lisfranc ligament is a critical stabilizing structure of the tarsometatarsal joint complex. Which of the following best describes its anatomic origin and insertion?





Explanation

The Lisfranc ligament is an intra-articular interosseous ligament that provides vital stability to the midfoot. It originates from the lateral aspect of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal. Notably, there is no direct intermetatarsal ligament connecting the bases of the first and second metatarsals, making this link crucial for structural integrity.

Question 76

In a posterior-stabilized total knee arthroplasty (TKA), the posterior cruciate ligament is resected. Which specific design feature of the implant is intended to substitute for the function of the posterior cruciate ligament by facilitating femoral rollback during knee flexion?





Explanation

In a posterior-stabilized (PS) TKA, the native posterior cruciate ligament (PCL) is excised. To replicate its biomechanical role, the implant incorporates a central polyethylene post on the tibial insert and a metallic cam on the femoral component. As the knee flexes, the femoral cam engages the tibial post, forcibly driving the femur posteriorly (femoral rollback). This increases knee flexion clearance and improves the lever arm of the extensor mechanism.

Question 77

A 28-year-old male falls from a height and sustains a thoracolumbar spinal fracture. A CT scan confirms a burst fracture at L1. According to the Denis three-column theory of spinal stability, a burst fracture is characterized by the biomechanical failure of which columns under an axial load?





Explanation

According to the Denis classification system, spinal stability is assessed using a three-column model. The anterior column consists of the anterior longitudinal ligament and the anterior half of the vertebral body/disc. The middle column comprises the posterior half of the body/disc and the posterior longitudinal ligament. The posterior column includes the pedicles, facets, and posterior ligamentous complex. A burst fracture, resulting from axial loading, involves failure of both the anterior and middle columns, potentially retropulsing bone fragments into the spinal canal.

Question 78

A 5-year-old girl falls off monkey bars and presents with a Gartland type III extension-type supracondylar humerus fracture. The hand is pink, well-perfused, but she is unable to flex the interphalangeal joint of her thumb and the distal interphalangeal joint of her index finger. Which of the following nerve structures has most likely been injured?





Explanation

The anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus, the lateral half of the flexor digitorum profundus (index and middle fingers), and the pronator quadratus. Clinically, AIN function is assessed by having the patient form an 'OK' sign. Failure to do so (resulting in a flattened pinch mechanism) indicates an AIN palsy.

Question 79

Articular cartilage is a complex tissue structured into distinct zones. Which zone contains chondrocytes arranged in vertical columns, has collagen fibers oriented perpendicular to the joint surface, and possesses the highest concentration of proteoglycans?





Explanation

Articular cartilage consists of four structural zones. The deep (or radial) zone contains chondrocytes organized in vertical columns parallel to the collagen fibers, which are themselves oriented perpendicular to the articular surface. This architecture provides maximum resistance to compressive forces. The deep zone also contains the highest concentration of proteoglycans and the lowest water content of the uncalcified layers.

Question 80

A 15-year-old boy presents with localized pain and swelling in his left mid-thigh, accompanied by a low-grade fever. Radiographs display a permeative, destructive diaphyseal lesion of the femur with a lamellated 'onion-skin' periosteal reaction. Histology shows sheets of uniform, small round blue cells. The most characteristic cytogenetic abnormality associated with this tumor is:





Explanation

The clinical presentation, radiographic findings (diaphyseal lesion, onion-skin periosteal reaction), and histology (small round blue cells) are diagnostic for Ewing sarcoma. The hallmark cytogenetic abnormality is the t(11;22)(q24;q12) chromosomal translocation, which is present in over 85% of cases and results in the formation of the EWS-FLI1 fusion transcript.

Question 81

Review the clinical image.

What is the earliest radiographic change expected in the natural progression of Scaphoid Nonunion Advanced Collapse (SNAC) if left untreated?





Explanation

Scaphoid Nonunion Advanced Collapse (SNAC) follows a predictable pattern of degenerative changes. Stage I involves arthritis isolated to the articulation between the scaphoid and the radial styloid. Stage II progresses to involve the entire radioscaphoid joint. Stage III involves the capitolunate joint. The radiolunate joint is characteristically spared because the lunate fossa cartilage remains concentric with the lunate.

Question 82

A 65-year-old female undergoes a posterior approach total hip arthroplasty as shown in the postoperative radiograph.

She suffers a posterior dislocation 3 weeks postoperatively while rising from a low chair. Which of the following component positions increases the risk of posterior dislocation?





Explanation

Posterior instability in total hip arthroplasty is exacerbated by positions of flexion, internal rotation, and adduction. Component malpositions that predispose to posterior dislocation include decreased acetabular anteversion (retroversion), decreased femoral anteversion, and insufficient femoral offset.

Question 83

An 11-year-old boy presents with a painful mass on his thigh and fever. Radiographs show a permeative diaphyseal lesion with an 'onion skin' periosteal reaction. Biopsy reveals small round blue cells.

Which chromosomal translocation is most characteristic of this tumor?





Explanation

Ewing sarcoma is characterized by small, round, blue cells and classically presents in the diaphysis of long bones with an 'onion skin' periosteal reaction. It is associated with the t(11;22)(q24;q12) translocation, resulting in the EWS-FLI1 fusion protein in approximately 85% of cases.

Question 84

According to the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following is considered a major criterion?





Explanation

The ICM criteria state that the presence of either a sinus tract communicating with the joint or two positive periprosthetic tissue/fluid cultures with phenotypically identical organisms serves as definitive (major) evidence of PJI. The other options are considered minor criteria.

Question 85

A 35-year-old male sustains a severe pelvic injury in an MVA. A spur sign, which is pathognomonic for a both-column acetabular fracture, is identified.

This sign is best visualized on which of the following radiographic views?





Explanation

The spur sign represents the inferior portion of the intact superior ilium that has been left behind when the articular segment is displaced medially. It is pathognomonic for a both-column fracture of the acetabulum and is best visualized on the obturator oblique radiograph of the Judet series.

Question 86

A 24-year-old pitcher undergoes arthroscopic repair of a type II SLAP lesion. Postoperatively, he notes significant weakness with external rotation and a vague, aching pain in the posterior shoulder. Physical examination reveals atrophy of the infraspinatus. Which of the following is the most likely cause?





Explanation

Repair of SLAP lesions, specifically when placing posterior anchors or passing sutures at the posterosuperior labrum, places the suprascapular nerve at risk as it passes through the spinoglenoid notch. Injury here predominantly causes isolated denervation and atrophy of the infraspinatus, sparing the supraspinatus.

Question 87

Which zone of articular cartilage has the highest concentration of proteoglycans and the lowest concentration of water?





Explanation

The deep (radial) zone of articular cartilage contains the lowest water content, highest proteoglycan concentration, and the largest diameter collagen fibrils which are oriented perpendicular to the joint surface to resist compressive forces.

Question 88

During surgical decompression of the ulnar nerve at the elbow, an anatomical release is planned.

What is the most proximal potential site of ulnar nerve compression that must be evaluated?





Explanation

The potential sites of ulnar nerve compression around the elbow from proximal to distal include: the Arcade of Struthers (about 8 cm proximal to the medial epicondyle), the medial intermuscular septum, the medial epicondyle itself, Osborne's ligament (cubital tunnel), and the deep aponeurosis of the FCU.

Question 89

A 55-year-old diabetic male presents with back pain, fever, and progressive bilateral lower extremity weakness. MRI reveals a spinal epidural abscess compressing the thoracic spinal cord. What is the most common causative organism?





Explanation

Staphylococcus aureus is the most common organism isolated in spinal epidural abscesses, accounting for more than 60% of cases. Immediate surgical decompression and targeted intravenous antibiotics are standard of care, especially when neurological deficits are present.

Question 90

A 14-year-old boy presents with rigid flat feet and lateral ankle pain. Radiographs demonstrate a 'C sign'.

This finding is most strongly indicative of which of the following conditions?





Explanation

The 'C sign' on a lateral radiograph of the foot is formed by the continuous outline of the medial talar dome and the inferior sustentaculum tali. It indicates the presence of a talocalcaneal (subtalar) coalition. Calcaneonavicular coalition is typically identified by the 'anteater nose' sign on an oblique view.

Question 91

Denosumab is an effective pharmacological agent used in the management of osteoporosis. What is its specific mechanism of action?





Explanation

Denosumab is a fully human monoclonal antibody that binds to RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand), preventing it from interacting with RANK on osteoclasts and their precursors. This inhibits osteoclast formation, function, and survival. Bisphosphonates inhibit farnesyl pyrophosphate synthase.

Question 92

When performing a reverse total shoulder arthroplasty for rotator cuff tear arthropathy, moving the center of rotation medially and inferiorly relative to the native anatomy accomplishes which of the following mechanical advantages?





Explanation

Grammont's principles for reverse total shoulder arthroplasty involve distalizing the humerus (to tension the deltoid) and medializing the center of rotation. Medialization increases the deltoid moment arm, improving its mechanical efficiency, and simultaneously reduces shear forces (torque) on the glenosphere, reducing the risk of aseptic loosening.

Question 93

When performing an anatomic single-bundle anterior cruciate ligament (ACL) reconstruction, improper tunnel placement can lead to graft failure.

Positioning the femoral tunnel too anterior (shallow in the notch) will result in a graft that is:





Explanation

In ACL reconstruction, if the femoral tunnel is placed too anteriorly (high in the notch with the knee flexed), the distance between the femoral and tibial attachments will increase as the knee goes into flexion. This causes the graft to be inappropriately tight in flexion and excessively loose in extension.

Question 94

A patient presents with an acute monoarticular swelling of the first metatarsophalangeal joint. Joint aspiration is performed. Under polarized light microscopy, the synovial fluid is expected to demonstrate:





Explanation

The patient is presenting with podagra, classic for gout. Gout is caused by monosodium urate crystals, which appear as negatively birefringent, needle-shaped crystals under polarized light microscopy. Pseudogout (CPPD) presents with weakly positively birefringent, rhomboid-shaped crystals.

Question 95

A 4-month-old female is being treated for developmental dysplasia of the hip (DDH) using a Pavlik harness.

What is the most common nerve palsy associated with excessive hyperflexion of the hips in this device?





Explanation

Excessive flexion of the hips in a Pavlik harness can cause impingement of the femoral nerve against the inguinal ligament, leading to a femoral nerve palsy (typically presenting as decreased active knee extension). Excessive abduction, conversely, increases the risk of avascular necrosis of the femoral head.

Question 96

During evaluation of an ankle fracture, a syndesmotic injury is suspected.

On standard mortise radiographs of a normal ankle, the tibiofibular clear space should measure:





Explanation

The tibiofibular clear space is measured 1 cm proximal to the tibial plafond. On both AP and mortise views, it should be less than 6 mm in a normal ankle. A measurement greater than 6 mm suggests a syndesmotic injury. Tibiofibular overlap should be >1 mm on the mortise view.

Question 97

A 32-year-old female falls on an outstretched hand and sustains a 'terrible triad' injury of the elbow.

This injury pattern classically includes an elbow dislocation, a radial head fracture, and a fracture of which of the following structures?





Explanation

The 'terrible triad' of the elbow is defined by the presence of a posterior or posterolateral elbow dislocation, a radial head fracture, and a fracture of the coronoid process. It is highly unstable and typically requires surgical intervention to restore the bony stabilizers (coronoid, radial head) and lateral collateral ligament complex.

Question 98

A patient presents with a midshaft humerus fracture and a concomitant complete radial nerve palsy. The fracture is closed and treated nonoperatively in a functional brace. At 12 weeks, there is no clinical or electromyographic (EMG) evidence of radial nerve recovery, and the fracture is healing well. What is the most appropriate next step in management?





Explanation

Radial nerve palsy associated with a closed humeral shaft fracture is initially managed expectantly. If there are no clinical or electromyographic signs of spontaneous recovery by 3 to 4 months post-injury, surgical exploration of the radial nerve is indicated.

Question 99

Osteogenesis imperfecta (OI) type I is a connective tissue disorder characterized by brittle bones and blue sclerae. It is most commonly caused by a mutation in which of the following genes?





Explanation

Osteogenesis imperfecta is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode the alpha-1 and alpha-2 chains of type I collagen. FGFR3 mutations cause achondroplasia. COMP mutations are seen in pseudoachondroplasia and multiple epiphyseal dysplasia. COL2A1 mutations cause type II collagenopathies (e.g., Kniest dysplasia). RUNX2 mutations cause cleidocranial dysplasia.

Question 100

A 72-year-old female who has been taking a medication for osteoporosis for 8 years presents with a low-energy fracture of the femoral shaft.

What is the primary mechanism by which bisphosphonates increase the risk of these atypical femur fractures?





Explanation

Long-term bisphosphonate therapy heavily suppresses osteoclast activity, which severely blunts normal targeted bone remodeling. Over time, normal physiological microdamage in the cortical bone is not repaired and accumulates. This leads to altered biomechanical properties and eventually the propagation of microcracks into a stress fracture and completed atypical femur fracture.

Previous ChapterOrthopedic Surgery Mock Exam - Set 7868C9 Next Chapter Orthopedic Surgery Mock Exam - Set FF5036
Dr. Mohammed Hutaif
Medically Verified Content by
Prof. Dr. Mohammed Hutaif
Consultant Orthopedic & Spine Surgeon
Chapter Index
    Back to Master Guide