Figure 7 shows the radiograph of a 64-year-old man who has neck pain and weakness of the upper and lower extremities following a motor vehicle accident. Examination reveals 3/5 quadriceps and 4/5 hip flexors but no ankle dorsiflexion or plantar flexi

Gardner-Wells tongs and closed reduction.

The Lisfranc ligament connects the base of the

second metatarsal and the medial cuneiform.

With the arm abducted 90 degrees and fully externally rotated, which of the following glenohumeral ligaments resists anterior translation of the humerus?

Anterior band of the inferior glenohumeral ligament complex

A 52-year-old woman has a 60-degree extensor lag following a right total knee arthroplasty performed 16 months ago. Since the time of her primary total knee arthroplasty she has undergone primary repair of a patellar tendon rupture that occurred afte

revision of the tibial and femoral components and reconstruction of the patellar tendon using an extensor mechanism allograft tensioned tightly in full extension.

A 52-year-old man sustained the left elbow injury shown in Figure A while playing basketball 2.5 months ago. He underwent the procedure shown in Figure B. Post-operatively he was mobilized in a hinged brace. On examination today, his arc of elbow fle

Continuous passive motion device

belowshowtheradiographs,andtheMRIsobtainedfromayear-oldmanwithworseningleftkneepain.Afoothip-to-ankleradiographshowsadegreevaruskneedeformity.Thepatient sustainedamajorleftkneeinjury5yearsagoandaconfirmedcompleteanteriorcruciateligament(ACL) tear.Hem

Proximal tibial osteotomy with subsequent ACL reconstruction

Dr Hutaif General Orthopedics Review: Online MCQ Quiz

Question 1

Which of the following orthopedic procedures relies primarily on intramembranous ossification for bone formation?

Explanation

Distraction osteogenesis primarily occurs via intramembranous ossification, which is characterized by the direct differentiation of mesenchymal stem cells into osteoblasts without a cartilaginous intermediate. Rigid fixation undergoes primary bone healing (cutting cones), while cast immobilization and IM nailing undergo secondary bone healing via endochondral ossification.

Question 2

A 35-year-old male presents with a pelvic ring injury after a high-speed motor vehicle collision. Radiographs reveal an APC-III (Anteroposterior Compression) injury. Which of the following neurologic structures is at the highest risk of injury in this specific fracture pattern?

Explanation

APC (Anteroposterior compression) injuries, particularly APC-III with anterior and posterior sacroiliac joint disruption, most commonly injure the L5 nerve root as it passes over the sacral ala. Sacral fractures, which are more classically seen in lateral compression (LC) injuries, more commonly injure the S1 and S2 nerve roots.

Question 3

A 12-year-old obese male presents with a left-sided Slipped Capital Femoral Epiphysis (SCFE). Which of the following factors represents the strongest indication for prophylactic pinning of the contralateral, asymptomatic hip?

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly indicated in patients with underlying endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency), as well as in patients outside the typical age range (girls <10, boys <11, or older teens), because they have a significantly higher rate of subsequent bilateral involvement.

Question 4

In a 15-year-old patient diagnosed with a high-grade intramedullary osteosarcoma of the distal femur, what is the most important prognostic factor for long-term overall survival?

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the single most important prognostic factor for overall survival in patients with localized high-grade osteosarcoma. A 'good response' is typically defined as greater than 90% tumor necrosis upon histologic examination of the resected specimen.

Question 5

When comparing a bone-patellar tendon-bone (BPTB) autograft to a quadrupled hamstring autograft for ACL reconstruction, the BPTB graft is most closely associated with which of the following post-operative outcomes?

Explanation

BPTB autografts are historically associated with an increased incidence of anterior knee pain and kneeling pain due to the harvest of the central third of the patellar tendon and the creation of bone defects in the patella and tibial tubercle. Hamstring grafts are associated with increased tunnel widening and potential loss of deep hamstring strength, but less anterior knee pain.

Question 6

Which of the following factors most significantly increases the rate of volumetric wear of conventional ultra-high molecular weight polyethylene (UHMWPE) in total hip arthroplasty?

Explanation

Volumetric wear of conventional UHMWPE increases with larger femoral head sizes due to the increased sliding distance per step. Conversely, linear wear may increase with smaller heads due to higher focal contact pressures. Highly cross-linked polyethylene significantly reduces both volumetric and linear wear. Ceramic heads also reduce wear rates compared to cobalt-chrome.

Question 7

A 65-year-old male presents with deteriorating handwriting, frequent stumbling, and diffuse hand numbness. On examination, flicking the nail of his middle finger results in involuntary flexion of his thumb and index finger. This specific physical exam finding is indicative of a lesion in which of the following tracts?

Explanation

The described test is Hoffmann's sign, which is indicative of an upper motor neuron lesion, specifically involving the corticospinal tract. It is a hallmark sign of cervical spondylotic myelopathy. The corticospinal tract is responsible for voluntary motor control.

Question 8

A patient sustains a deep laceration to the volar aspect of the finger precisely at the distal interphalangeal (DIP) joint crease, resulting in an inability to actively flex the distal phalanx. This injury is located in which flexor tendon zone?

Explanation

Flexor tendon Zone I extends from the distal insertion of the flexor digitorum superficialis (FDS) on the middle phalanx to the insertion of the flexor digitorum profundus (FDP) on the distal phalanx. An injury at the DIP joint level isolates the FDP tendon and falls strictly into Zone I.

Question 9

A 28-year-old male sustains a closed tibia fracture. Which of the following pressure measurements is the most accurate diagnostic threshold for indicating an acute compartment syndrome requiring fasciotomy?

Explanation

The delta pressure (ΔP) is defined as the diastolic blood pressure minus the absolute compartment pressure. A ΔP of less than 30 mmHg is considered the most reliable threshold for diagnosing acute compartment syndrome because it accounts for the patient's systemic perfusion pressure, mitigating false positives seen with absolute pressure measurements.

Question 10

In normal articular cartilage, which structural zone contains the highest concentration of proteoglycans and the lowest concentration of water?

Explanation

The deep (radial) zone of articular cartilage has the highest concentration of proteoglycans and the lowest water content. The collagen fibers here are oriented vertically to resist compressive forces. In contrast, the superficial zone has the highest water content, highest collagen content, and lowest proteoglycan content.

Question 11

A 55-year-old patient with long-standing diabetes presents with a swollen, erythematous, and warm foot. Radiographs show periarticular fragmentation, debris, and subluxation at the tarsometatarsal joints. According to the Eichenholtz classification, what stage is this Charcot arthropathy?

Explanation

Eichenholtz Stage I (Development/Fragmentation) is characterized clinically by a red, hot, swollen foot and radiographically by bone fragmentation, joint debris, subluxation/dislocation, and loss of joint space. Stage 0 is characterized by clinical warmth/swelling with normal radiographs. Stage II is coalescence, and Stage III is consolidation/remodeling.

Question 12

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

Explanation

The correct sequence of correction in the Ponseti method follows the acronym CAVE: Cavus (corrected first by supinating the forefoot to align with the midfoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy as the final step).

Question 13

During a total knee arthroplasty using a posterior referencing system, the surgeon notes that the trial components result in a knee that is tight in flexion but perfectly balanced in extension. Which of the following is the most appropriate step to balance the knee?

Explanation

A knee that is tight in flexion but balanced in extension indicates a flexion gap that is too small relative to the extension gap. When using posterior referencing, downsizing the femoral component reduces the anterior-posterior dimension of the femur, increasing the flexion gap without altering the distal cut (which dictates the extension gap).

Question 14

A 45-year-old female presents with a wrist injury after a fall. Radiographs demonstrate a displaced shear fracture of the volar articular margin of the distal radius with volar subluxation of the carpus. What is the correct eponym for this fracture pattern?

Explanation

A volar Barton fracture is defined as an intra-articular shear fracture of the volar lip of the distal radius that is associated with volar subluxation or dislocation of the radiocarpal joint. A Smith fracture is classically an extra-articular distal radius fracture with volar angulation.

Question 15

Tranexamic acid (TXA) is frequently used in orthopedic surgery to minimize perioperative blood loss. What is the primary mechanism of action of TXA?

Explanation

Tranexamic acid is a synthetic lysine analog that acts as an antifibrinolytic agent. It competitively binds to the lysine-binding sites on plasminogen, preventing its activation to plasmin, thereby inhibiting the degradation of fibrin clots.

Question 16

According to the Denis three-column classification of spinal fractures, which anatomical structure is considered the most posterior boundary of the middle column?

Explanation

In the Denis classification, the anterior column contains the ALL and anterior half of the vertebral body/annulus. The middle column comprises the posterior half of the body/annulus and the Posterior Longitudinal Ligament (PLL). The posterior column includes all structures posterior to the PLL (pedicles, facets, lamina, spinous processes, ligamentum flavum).

Question 17

A 60-year-old male presents with shoulder pain and weakness. On physical examination, the patient has a positive 'horn blower's' sign. This finding is most specific for pathology involving which of the following muscles?

Explanation

The horn blower's sign evaluates for teres minor weakness or a massive rotator cuff tear involving the teres minor. It is positive when the patient is unable to maintain external rotation with the arm abducted to 90 degrees, causing the arm to fall into internal rotation, often forcing the patient to elevate their arm to bring their hand to their mouth.

Question 18

A 70-year-old female presents with severe, atraumatic back pain. Radiographs reveal multiple 'punched-out' lytic lesions in the skull and a compression fracture of L2. Serum protein electrophoresis shows a monoclonal spike. Which of the following laboratory findings is also most characteristically associated with this patient's underlying disease?

Explanation

The patient's presentation is highly characteristic of multiple myeloma, the most common primary malignancy of bone in adults. Characteristic laboratory findings include hypercalcemia (not hypocalcemia), normal alkaline phosphatase (unless there is a healing fracture), M-spike on SPEP, positive Rouleaux formation, and the presence of Bence Jones proteins (free light chains) in the urine.

Question 19

A 3-month-old female is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During a follow-up visit, the physician notes an absence of active knee extension on the treated side. Which of the following is the most likely cause of this complication?

Explanation

The most common nerve palsy associated with the Pavlik harness is a femoral nerve palsy. This complication results from excessive hip flexion caused by over-tightening of the anterior straps, which stretches or compresses the femoral nerve. It presents clinically as a loss of active knee extension.

Question 20

Based on the principles of biomechanics, if the outer radius of a solid cylindrical intramedullary nail is doubled while maintaining the same material, by what factor does its bending stiffness (area moment of inertia) increase?

Explanation

Bending stiffness of a solid cylinder is proportional to its area moment of inertia, which is calculated by the formula (π * r^4) / 4. Because the radius (r) is raised to the fourth power, doubling the radius (2^4) results in a 16-fold increase in the bending stiffness of the nail.

Question 21

A surgeon performing a posterior-stabilized total knee arthroplasty evaluates the flexion and extension gaps with trial components in place. The extension gap is symmetric and perfectly balanced. The flexion gap is symmetric but significantly tight. What is the most appropriate next step to balance the knee?

Explanation

A tight flexion gap with a balanced extension gap indicates the anteroposterior (AP) dimension of the femoral component is too large. By downsizing the femoral component, more posterior condylar bone is resected, which enlarges the flexion gap without affecting the extension gap. Using the same polyethylene thickness maintains the already balanced extension gap. Releasing the PCL is incorrect because a posterior-stabilized design already sacrifices the PCL. Resecting more tibia would symmetrically enlarge both flexion and extension gaps.

Question 22

A 68-year-old female presents with recurrent posterior dislocations of her total hip arthroplasty. Radiographs reveal the acetabular cup is placed in 45 degrees of abduction and 5 degrees of anteversion. The femoral stem is in 15 degrees of anteversion. What is the most likely primary cause of her instability?

Explanation

The 'safe zone' for acetabular cup placement, as originally described by Lewinnek, is 15 +/- 10 degrees of anteversion and 40 +/- 10 degrees of abduction. A cup placed in only 5 degrees of anteversion is retroverted relative to the ideal position, predisposing the patient to posterior instability, particularly when hip flexion and internal rotation occur.

Question 23

A 55-year-old female presents with medial foot pain and inability to perform a single-leg heel rise. Examination shows a flexible hindfoot valgus and forefoot abduction. AP radiographs show 40% uncoverage of the talonavicular joint head. Which of the following surgical interventions is most appropriate for this stage IIb adult-acquired flatfoot deformity?

Explanation

The patient has a Stage IIb adult-acquired flatfoot deformity (tibialis posterior tendon dysfunction). Stage II indicates a flexible deformity. Stage IIb specifically denotes significant forefoot abduction (typically >30% talonavicular uncoverage). Treatment requires a soft tissue reconstruction (FDL transfer), correction of hindfoot valgus (MDCO), and correction of forefoot abduction (lateral column lengthening, such as an Evans osteotomy). A triple arthrodesis is reserved for Stage III (rigid) deformity.

Question 24

A 45-year-old female presents with a painful bunion. Weight-bearing radiographs reveal a hallux valgus angle (HVA) of 38 degrees and an intermetatarsal angle (IMA) of 18 degrees. Clinical examination reveals hypermobility of the first tarsometatarsal (TMT) joint. What is the most appropriate surgical management?

Explanation

The Lapidus procedure (arthrodesis of the 1st TMT joint) is indicated for moderate to severe hallux valgus (IMA > 15 degrees) associated with first ray hypermobility. A distal chevron is inadequate for an IMA of 18 degrees. While a proximal osteotomy can correct a large IMA, it does not address the TMT hypermobility, leading to a high recurrence rate. First MTP arthrodesis is typically reserved for severe deformity with osteoarthritis or rheumatoid arthritis.

Question 25

A 22-year-old male rugby player presents with recurrent anterior shoulder dislocations. A pre-operative 3D CT scan demonstrates 25% anterior glenoid bone loss. Which of the following is the most appropriate surgical treatment?

Explanation

Anterior glenoid bone loss greater than 20-25% in a contact athlete (referred to as a critical bone defect) is a contraindication to an isolated arthroscopic or open soft-tissue Bankart repair due to unacceptably high recurrence rates. A bony augmentation procedure, most commonly the Latarjet procedure (transfer of the coracoid process with the attached conjoined tendon to the anterior glenoid), is the gold standard for restoring stability in this scenario.

Question 26

A 50-year-old female felt a sudden 'pop' in the back of her knee while squatting. MRI reveals a complete tear of the medial meniscus posterior root. If left untreated, this injury results in a biomechanical state most equivalent to which of the following?

Explanation

The meniscal roots anchor the meniscus to the tibia, converting axial loads into circumferential 'hoop stresses.' A complete root tear disrupts this mechanism, allowing the meniscus to extrude. Biomechanically, this results in a complete loss of hoop stresses, significantly reducing contact area and increasing peak contact pressures in the medial compartment, functioning identically to a total meniscectomy.

Question 27

Which zone of articular cartilage contains the highest concentration of proteoglycans and features chondrocytes aligned perpendicular to the articular surface?

Explanation

Articular cartilage is divided into distinct zones. The deep (radial) zone has the highest proteoglycan content, the lowest water content, and chondrocytes/collagen fibers that are aligned perpendicular to the joint surface to resist compressive loads. The superficial zone has the highest water content and collagen fibers aligned parallel to the surface to resist shear stress.

Question 28

The primary blood supply to the proximal pole of the scaphoid enters the bone at which of the following anatomic locations?

Explanation

The blood supply to the scaphoid is predominantly retrograde. Approximately 70-80% of the bone, including the entire proximal pole, is supplied by the dorsal carpal branch of the radial artery, which enters at the non-articular dorsal ridge and flows proximally. This retrograde blood supply explains the high rate of avascular necrosis (AVN) seen in proximal pole scaphoid fractures.

Question 29

A 19-year-old male sustains an L2 flexion-distraction injury (Chance fracture) during a motor vehicle collision while wearing a lap belt. Which of the following associated injuries has the highest incidence in this patient profile?

Explanation

Chance fractures (flexion-distraction injuries of the spine) are classic 'seatbelt injuries' caused by the body flexing over a lap belt acting as a fulcrum. They are highly associated with intra-abdominal injuries, most commonly hollow viscus injuries (e.g., bowel perforation or mesenteric tearing), occurring in up to 40-50% of cases. A high index of suspicion and general surgery consultation is mandatory.

Question 30

According to Perren's strain theory of bone healing, what is the maximum percentage of tissue strain that permits the direct formation of lamellar bone without an intermediate cartilaginous or fibrous phase?

Explanation

Perren's strain theory dictates that tissues dictate the type of healing based on the strain they can tolerate. Lamellar bone can only tolerate <2% strain. Therefore, primary (direct) bone healing requires absolute stability (strain <2%). Woven bone can tolerate up to 10% strain, while cartilage tolerates 10-30% strain, and granulation tissue tolerates up to 100% strain, which defines the secondary (callus) healing pathway under relative stability.

Question 31

When compared to a quadrupled hamstring autograft, which of the following is considered a primary biological advantage of using a bone-patellar tendon-bone (BPTB) autograft in anterior cruciate ligament (ACL) reconstruction?

Explanation

The major biological advantage of a BPTB autograft is bone-to-bone healing at the tunnel sites, which occurs much faster (approximately 6 weeks) and provides more rigid initial fixation than the soft tissue-to-bone healing (Sharpey's fibers) required for hamstring autografts (which takes 8-12 weeks). BPTB grafts have a higher incidence of anterior knee pain. At time zero, a quadrupled hamstring graft is actually stronger (approx 4000 N) than a 10mm BPTB graft (approx 2900 N).

Question 32

A 72-year-old female treated with alendronate for 8 years presents with a 3-month history of progressive left thigh pain. Radiographs reveal lateral cortical thickening and a transverse radiolucent line in the subtrochanteric region of the left femur. What is the most appropriate management?

Explanation

This patient has an impending atypical femur fracture (AFF) associated with long-term bisphosphonate use, characterized by lateral cortical beaking, transverse radiolucency, and thigh pain. Because she has a symptomatic impending fracture with radiographic changes, prophylactic intramedullary nailing (cephalomedullary preferred in the subtrochanteric region) is indicated. Bisphosphonates must be discontinued immediately. Plating is biomechanically inferior for AFFs.

Question 33

A 30-year-old male sustains a closed tibia fracture. The surgical team is concerned about acute compartment syndrome and measures the intracompartmental pressures. The 'delta P' is used to determine the need for fasciotomy. Delta P is defined as the difference between the compartment pressure and which of the following systemic values?

Explanation

Delta P is calculated as the Diastolic Blood Pressure minus the Intracompartmental Pressure. A Delta P of less than 30 mm Hg is an absolute indication for emergency fasciotomy. Using absolute compartment pressures alone can be misleading, especially in hypotensive trauma patients, whereas Delta P accounts for the driving perfusion pressure of the limb.

Question 34

A 14-year-old male presents with a permeative lytic lesion in the diaphysis of the femur with an 'onion skin' periosteal reaction. Biopsy reveals sheets of small, round, blue cells. Which of the following chromosomal translocations is most characteristic of this malignancy?

Explanation

The clinical and histological presentation describes Ewing sarcoma. The most common defining chromosomal translocation in Ewing sarcoma is t(11;22), which results in the EWSR1-FLI1 fusion protein (found in about 85% of cases). t(X;18) is seen in synovial sarcoma. t(2;13) is seen in alveolar rhabdomyosarcoma.

Question 35

A 65-year-old male presents with progressive clumsiness of the hands and an unsteady, broad-based gait. Examination reveals a positive Hoffmann sign and hyperreflexia. MRI shows severe cervical stenosis at C4-C5. Which of the following MRI findings of the spinal cord is most predictive of a poor prognosis for neurologic recovery postoperatively?

Explanation

In cervical spondylotic myelopathy, intrinsic spinal cord signal changes carry prognostic value. High T2 signal alone indicates edema or gliosis and can be reversible. However, a high T2 signal accompanied by a focal low T1 signal indicates myelomalacia (cystic necrosis or permanent cavitary changes of the cord) and is strongly correlated with a poor potential for clinical recovery after surgical decompression.

Question 36

A 30-year-old carpenter sustains a zone II laceration of the flexor digitorum profundus (FDP). During repair, the surgeon chooses a 4-strand core suture over a 2-strand core suture. What is the primary biomechanical advantage of increasing the number of strands crossing the repair site in the context of an early active motion rehabilitation protocol?

Explanation

In flexor tendon repairs, the tensile strength and gap resistance of the repair are directly proportional to the number of core suture strands crossing the repair site. A minimum of a 4-strand repair is required to safely withstand the forces generated during early active motion protocols without gapping. A 2-strand repair risks gapping or rupture with early active motion, while increasing strands beyond 4 may increase bulk and friction (work of flexion).

Question 37

A 12-year-old male presents with a unilateral left Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the most widely accepted absolute indication for prophylactic in situ pinning of the asymptomatic contralateral right hip?

Explanation

Contralateral prophylactic pinning in SCFE is universally recommended for patients with atypical or secondary SCFE, which most commonly includes those with underlying endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or radiation therapy, as the risk of contralateral slip is extremely high (up to 100%). While age (especially <10), obesity, and open triradiate cartilage are relative indications in idiopathic SCFE, an endocrine disorder is a definitive indication.

Question 38

A 45-year-old heavy smoker is seen 9 months after a closed midshaft tibia fracture treated with an intramedullary nail. He complains of persistent pain. Radiographs demonstrate a visible fracture line with tapered, sclerotic bone ends and absent callus formation. What is the most appropriate surgical management for this complication?

Explanation

The patient has an atrophic nonunion, characterized radiographically by sclerotic, tapered bone ends and a lack of callus, which implies a failure of biology (poor vascularity and osteogenic potential). Management of atrophic nonunions requires optimizing both biology and stability. This involves debridement of the sclerotic bone ends down to bleeding bone, addition of bone graft (to stimulate biology), and ensuring rigid stabilization (e.g., exchange nailing or plating). Dynamization or simply exchange nailing alone is insufficient because it does not address the lack of biological activity.

Question 39

A 50-year-old female presents with persistent, unchanged numbness and tingling in her thumb, index, and middle fingers 6 months after an open carpal tunnel release. Postoperative EMG confirms severe, ongoing median neuropathy across the wrist. What is the most common cause of persistent carpal tunnel syndrome when symptoms have remained unchanged since surgery?

Explanation

The most common cause of persistent carpal tunnel syndrome (symptoms that never resolved after surgery) is incomplete release of the transverse carpal ligament (typically the distal extent). Recurrent carpal tunnel syndrome (symptoms that improved but returned months to years later) is most commonly caused by perineural fibrosis or reconstitution of the ligament. Palmar cutaneous branch injury causes pain/numbness at the base of the palm, not in the median nerve digital distribution.

Question 40

Highly cross-linked polyethylene (HXLPE) is the standard bearing surface used in modern total hip arthroplasty due to its significantly decreased volumetric wear. However, the process of cross-linking and subsequent melting or annealing to eliminate free radicals leads to a clinically relevant decrease in which of the following mechanical properties?

Explanation

Irradiation of polyethylene creates cross-links that drastically reduce abrasive and adhesive volumetric wear. However, irradiation also breaks polymer chains, creating free radicals. Subsequent thermal treatments (melting or annealing) are required to eliminate these free radicals to prevent oxidation. This thermal treatment reduces the crystallinity of the polyethylene, which decreases its fatigue resistance, yield strength, ductility, and ultimate tensile strength. This is why highly cross-linked polyethylene must be used cautiously in high-stress, non-conforming joints like the knee or in very thin liners.

Question 41

A 45-year-old male undergoes a posterolateral lumbar fusion using recombinant human bone morphogenetic protein-2 (rhBMP-2). Through which specific intracellular signaling pathway does this biologic agent primarily promote osteoblast differentiation?

Explanation

rhBMP-2 binds to serine/threonine kinase receptors, causing phosphorylation of SMAD 1, 5, and 8. These molecules then complex with SMAD 4 to enter the nucleus and upregulate osteogenic genes like Runx2.

Question 42

A 30-year-old trauma patient presents in hemorrhagic shock with an "open book" pelvic fracture. A pelvic binder is to be applied. What is the optimal anatomic landmark for centering the binder to effectively reduce pelvic volume?

Explanation

Pelvic binders should be centered directly over the greater trochanters to effectively compress the pelvic ring and reduce pelvic volume. Placement over the iliac crests is incorrect and can paradoxically open the pelvis in certain fracture patterns.

Question 43

A 6-month-old female with developmental dysplasia of the hip (DDH) has failed 6 weeks of Pavlik harness treatment for a persistently dislocated left hip. What is the most appropriate next step in management?

Explanation

For a persistently dislocated hip at 6 months of age after failed Pavlik harness treatment, closed reduction and spica casting under anesthesia is the standard next step. Prolonging harness use in a dislocated hip increases the risk of "Pavlik harness disease" (posterior acetabular erosion).

Question 44

A 25-year-old female presents with a destructive, expansile lytic lesion in the distal femur. Biopsy confirms a Giant Cell Tumor of bone. If medical therapy with denosumab is initiated, what is its primary mechanism of action?

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to RANKL, preventing it from activating RANK on osteoclasts and their precursors. This effectively inhibits osteoclast-mediated bone destruction characteristic of giant cell tumors.

Question 45

During the physical examination of a 65-year-old male with progressive hand clumsiness and gait instability, the examiner sharply flicks the distal phalanx of the middle finger, resulting in reflex flexion of the thumb and index finger. What does this specific clinical test indicate?

Explanation

This describes the Hoffmann sign, which is indicative of upper motor neuron dysfunction, commonly seen in conditions like cervical spondylotic myelopathy. It is considered the upper extremity equivalent of the Babinski sign.

Question 46

A 55-year-old male undergoes a total hip arthroplasty. To minimize the risk of galvanic corrosion, the surgeon must be cautious about metal combinations. Which combination of stem and head materials is most strongly associated with galvanic and fretting corrosion at the trunnion?

Explanation

The combination of a titanium alloy stem with a cobalt-chromium head introduces dissimilar metals at the modular junction, increasing the risk of galvanic and fretting corrosion (trunnionosis). Ceramic heads are electrically insulating and do not cause galvanic corrosion.

Question 47

A 22-year-old football player sustains a non-contact pivoting knee injury. Radiographs reveal an avulsion fracture of the lateral tibial plateau (Segond fracture). This radiographic finding is virtually pathognomonic for an injury to which of the following structures?

Explanation

The Segond fracture is an avulsion of the anterolateral capsular attachments (often involving the anterolateral ligament) from the lateral tibial plateau. Its presence on an AP radiograph is highly specific and virtually pathognomonic for an anterior cruciate ligament (ACL) tear.

Question 48

A 24-year-old male falls onto an outstretched hand and sustains a displaced fracture through the proximal pole of the scaphoid. Why is this specific fracture pattern at an exceptionally high risk for avascular necrosis (AVN)?

Explanation

The primary blood supply to the scaphoid is derived from branches of the radial artery that enter distally and flow in a retrograde direction to perfuse the proximal pole. Fractures through the proximal pole disrupt this tenuous supply, leading to high rates of AVN.

Question 49

A 30-year-old female sustains a midfoot crush injury. Radiographs show widening of the space between the bases of the 1st and 2nd metatarsals, with a small bony avulsion fragment in this interval ("fleck sign"). The torn ligament responsible for this finding typically connects which two structures?

Explanation

The primary Lisfranc ligament connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. A "fleck sign" in this interval represents an avulsion of this critical stabilizing ligament.

Question 50

In the context of orthopedic biomechanics and materials science, what does the "yield point" on a stress-strain curve specifically represent?

Explanation

The yield point marks the end of elastic deformation (where a material returns to its original shape) and the onset of plastic deformation (resulting in permanent shape change). Beyond this specific point, Hooke's Law is no longer applicable.

Question 51

A 32-year-old male sustains a severely comminuted tibial plateau fracture. Six hours later, he reports intractable pain out of proportion to the injury. Compartment pressures are measured. What is the currently accepted clinical threshold for diagnosing acute compartment syndrome requiring fasciotomy?

Explanation

A delta pressure (diastolic blood pressure minus absolute compartment pressure) of less than 30 mmHg is considered the most reliable threshold for diagnosing acute compartment syndrome. Absolute pressure alone is less accurate as it fails to account for the patient's systemic perfusion pressure.

Question 52

An 8-year-old boy is diagnosed with Legg-Calvé-Perthes disease. According to the Herring lateral pillar classification, a Type C hip is characterized by what degree of height loss in the lateral pillar of the femoral head?

Explanation

In the Herring lateral pillar classification, Type A indicates no height loss, Type B indicates less than 50% height loss, and Type C denotes greater than 50% height loss of the lateral pillar. Type C is associated with a poor clinical prognosis.

Question 53

A 16-year-old male presents with distal femoral pain. Imaging reveals a mixed lytic/sclerotic lesion with a "sunburst" periosteal reaction. Biopsy confirms high-grade osteosarcoma. Which of the following laboratory markers, when elevated at presentation, serves as an independent negative prognostic indicator for survival?

Explanation

Elevated levels of serum alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) at the time of initial diagnosis are recognized as independent negative prognostic factors in osteosarcoma. They generally correlate with a higher tumor burden and poorer overall survival.

Question 54

According to Perren's strain theory, what is the maximum amount of interfragmentary strain that permits primary bone healing?

Explanation

Primary bone healing occurs without callus formation and requires absolute stability. According to Perren's strain theory, the interfragmentary strain must be less than 2% to allow osteoclasts to form cutting cones across the fracture site.

Question 55

A 14-year-old boy presents with a diaphyseal femur lesion showing an onion-skin periosteal reaction. Histology reveals small blue round cells. Which of the following cytogenetic abnormalities is most characteristic of this tumor?

Explanation

The clinical and histologic picture describes Ewing sarcoma. The most common translocation associated with this tumor is t(11;22)(q24;q12), which results in the EWS-FLI1 fusion protein.

Question 56

A 28-year-old male sustains a closed tibial shaft fracture. Clinical suspicion for acute compartment syndrome is high. Which of the following pressure measurements is the most reliable threshold for emergent fasciotomy?

Explanation

Delta pressure (diastolic blood pressure minus compartment pressure) is the most accurate indicator for compartment syndrome. A delta pressure of less than 30 mmHg is the widely accepted threshold indicating the need for emergent fasciotomy.

Question 57

The direct anterior approach (Smith-Petersen) to the hip utilizes a true internervous plane. This plane is located between muscles innervated by which of the following nerve pairs?

Explanation

The superficial internervous plane of the direct anterior approach is between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The deep plane is between the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).

Question 58

A 45-year-old female presents with acute severe lower back pain and bilateral sciatica. Which of the following clinical findings has the highest sensitivity for diagnosing Cauda Equina Syndrome?

Explanation

Urinary retention is the most consistent and sensitive finding in Cauda Equina Syndrome. A post-void residual volume of less than 100-200 mL effectively rules out the diagnosis in most cases.

Question 59

A 6-year-old girl sustains a Gartland type III extension-type supracondylar humerus fracture. Which of the following peripheral nerves is most commonly injured in this specific fracture pattern?

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. Clinically, this presents as an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (the 'A-OK' sign).

Question 60

Following an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, the graft undergoes 'ligamentization'. During which phase is the graft mechanically at its weakest?

Explanation

The revascularization and cellular proliferation phase (typically 6-12 weeks post-op) is characterized by significant enzymatic degradation and collagen turnover. This renders the graft mechanically at its weakest point and highly susceptible to elongation or rupture.

Question 61

A 35-year-old recreational athlete is undergoing percutaneous repair of an acute Achilles tendon rupture. Which of the following neurovascular structures is at the highest risk of iatrogenic injury during this procedure?

Explanation

The sural nerve crosses from medial to lateral along the posterior aspect of the calf and runs intimately close to the lateral border of the Achilles tendon. It is highly vulnerable to entrapment or laceration during percutaneous or minimally invasive Achilles repairs.

Question 62

In hand surgery, the flexor tendon 'Zone II' (historically known as no man's land) is defined proximally by which of the following anatomical landmarks?

Explanation

Flexor tendon Zone II extends from the proximal edge of the A1 pulley to the insertion of the flexor digitorum superficialis (FDS) tendon. Because both the FDS and FDP tendons run tightly together within the fibro-osseous sheath here, repairs are prone to adhesions.

Question 63

Which of the following terms best describes the viscoelastic property where a biological material continues to slowly deform over time when subjected to a constant, sustained load?

Explanation

Creep is the progressive deformation of a material over time under a constant load. Stress relaxation, conversely, is the decrease in stress over time when a material is held at a constant strain (length).

Question 64

During a primary total knee arthroplasty, the surgeon assesses the gap kinematics and notes that the knee is tight in full extension but perfectly balanced in 90 degrees of flexion. Which of the following is the most appropriate corrective maneuver?

Explanation

A tight extension gap with a balanced flexion gap indicates that the distal femoral resection was insufficient. Resecting more distal femur will increase the extension gap without altering the already balanced flexion gap.

Question 65

A 25-year-old male sustains a traumatic spondylolisthesis of the axis (Hangman's fracture) following a motor vehicle accident. What is the classic mechanism of injury for this fracture pattern?

Explanation

A Hangman's fracture is a traumatic spondylolisthesis of C2, typically resulting from a combined hyperextension and axial loading mechanism. This leads to bilateral fractures through the pars interarticularis of the axis.

Question 66

An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The harness is incorrectly adjusted, forcing the hip into excessive abduction. Which of the following complications is most closely associated with this positioning error?

Explanation

Excessive abduction in a Pavlik harness places the medial circumflex femoral artery under tension, significantly increasing the risk of avascular necrosis of the femoral head. Excessive flexion, on the other hand, is associated with femoral nerve palsy.

Question 67

A 65-year-old male presents with bone pain, anemia, and hypercalcemia. Radiographs show multiple 'punched-out' lytic lesions in the skull and pelvis. The primary mechanism of bone destruction in this disease is driven by the upregulation of which of the following?

Explanation

The patient has Multiple Myeloma. The myeloma cells secrete factors (like MIP-1 alpha) that upregulate RANKL and downregulate OPG, leading to massive osteoclast activation and the characteristic lytic bone lesions.

Question 68

During preoperative planning for a patient with recurrent anterior shoulder instability, the concept of the 'glenoid track' is evaluated. A Hill-Sachs lesion is considered 'off-track' if it:

Explanation

An 'off-track' Hill-Sachs lesion extends medial to the medial margin of the glenoid track. This makes it an engaging lesion during abduction and external rotation, which often requires a concurrent Remplissage procedure in addition to Bankart repair.

Question 69

The primary stabilizing ligament of the tarsometatarsal articulation (Lisfranc ligament) connects which two osseous structures?

Explanation

The Lisfranc ligament is an intra-articular ligament that connects the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is critical for the stability of the midfoot arch.

Question 70

Which of the following bone morphogenetic proteins (BMPs) is considered to have osteo-inhibitory effects rather than osteoinductive effects?

Explanation

While most BMPs (such as BMP-2 and BMP-7) are strongly osteoinductive and promote bone formation, BMP-3 is unique as it acts as an antagonist to osteogenic BMPs, thereby inhibiting bone formation.

Question 71

A 45-year-old farmer sustains a severe open tibia fracture with extensive soft tissue stripping and soil contamination (Gustilo-Anderson IIIB). In addition to a first-generation cephalosporin and an aminoglycoside, which antibiotic is most critical to add to the regimen?

Explanation

Farm injuries or wounds heavily contaminated with soil or standing water have a high risk of Clostridium perfringens infection. High-dose penicillin should be added to the standard open fracture antibiotic regimen to provide adequate anaerobic coverage.

Question 72

In the surgical treatment of Carpal Tunnel Syndrome, the transverse carpal ligament is incised. This ligament attaches ulnarly to the hook of the hamate and the pisiform, and radially to the scaphoid tuberosity and which other carpal bone?

Explanation

The transverse carpal ligament (flexor retinaculum) attaches radially to the scaphoid tuberosity and the crest of the trapezium. Ulnarly, it attaches to the pisiform and the hook of the hamate.

Question 73

Which of the following muscles of the posterior thigh is uniquely innervated by the common peroneal division of the sciatic nerve?

Explanation

The short head of the biceps femoris is the only muscle in the posterior compartment of the thigh innervated by the common peroneal division of the sciatic nerve. All other hamstring muscles are innervated by the tibial division.

Question 74

A 30-year-old male sustains a closed tibia fracture. Several hours later, he develops severe pain out of proportion to the injury, exacerbated by passive stretch of the toes. His diastolic blood pressure is 80 mm Hg, and an intra-compartmental pressure monitor reads 55 mm Hg. What is the most appropriate next step in management?

Explanation

A delta pressure (diastolic blood pressure minus compartment pressure) of less than 30 mm Hg is an absolute indication for emergent fasciotomy. A four-compartment release is the standard of care for acute compartment syndrome of the leg.

Question 75

During a primary total hip arthroplasty using a posterior approach, the surgeon performs an inferior capsular release. Which vascular structure is at the highest risk of injury during this specific step near the quadratus femoris?

Explanation

The medial circumflex femoral artery (MCFA) courses near the superior border of the quadratus femoris. It is the primary blood supply to the femoral head and is highly vulnerable during inferior capsular releases in the posterior approach.

Question 76

A 2-week-old infant is undergoing serial casting using the Ponseti method for congenital talipes equinovarus (clubfoot). According to the Ponseti principles, what is the final component of the deformity to be corrected?

Explanation

The Ponseti method sequentially corrects the clubfoot deformity in a specific order: Cavus, Adductus, Varus, and finally Equinus (CAVE mnemonic). Equinus is corrected last, frequently requiring a percutaneous Achilles tenotomy.

Question 77

In total joint arthroplasty, highly cross-linking ultra-high-molecular-weight polyethylene (UHMWPE) is performed primarily to alter its material properties. How does this manufacturing process alter the polyethylene compared to conventional UHMWPE?

Explanation

Highly cross-linked polyethylene significantly improves wear resistance, thereby reducing osteolysis in total joint arthroplasty. However, the cross-linking and subsequent thermal treatments reduce mechanical properties such as fatigue strength and fracture toughness.

Question 78

A 25-year-old athlete sustains a knee injury. On examination, the dial test reveals 15 degrees of increased external rotation on the injured side compared to the normal side when tested at 30 degrees of knee flexion. However, at 90 degrees of knee flexion, the external rotation is symmetrical bilaterally. What is the most likely diagnosis?

Explanation

An isolated posterolateral corner (PLC) injury is indicated by increased external rotation at 30 degrees of flexion but not at 90 degrees. If external rotation asymmetry is present at both 30 and 90 degrees, a combined PLC and PCL injury is diagnosed.

Question 79

A 12-year-old boy presents with progressive thigh pain. Radiographs demonstrate an aggressive, permeative lytic lesion in the diaphysis of the femur with an "onion-skin" periosteal reaction. A biopsy is obtained. Which of the following genetic translocations is most characteristic of this tumor?

Explanation

Ewing sarcoma typically presents in the diaphysis of long bones in children and is associated with a characteristic "onion-skin" periosteal reaction. It is defined molecularly by the t(11;22) chromosomal translocation, resulting in the EWS-FLI1 fusion protein.

Question 80

A 28-year-old male sustains a Hawkins Type II talar neck fracture. Which of the following vascular structures, responsible for providing the majority of the blood supply to the talar body, is most severely compromised in this injury pattern?

Explanation

The artery of the tarsal canal, a major branch of the posterior tibial artery, supplies the majority of the blood to the talar body. It is highly susceptible to disruption in displaced talar neck fractures, leading to a high risk of avascular necrosis.

Question 81

A 22-year-old rugby player presents with an inability to actively flex the distal interphalangeal (DIP) joint of his right ring finger. MRI confirms an avulsion of the flexor digitorum profundus (FDP) tendon with complete retraction into the palm. What is the optimal time frame for surgical repair to prevent permanent muscle contracture and preserve the remaining blood supply?

Explanation

This is a Leddy-Packer Type I FDP avulsion (Jersey finger) where the tendon retracts into the palm, rupturing both the long and short vincula. Due to the severely compromised blood supply and rapid muscle contraction, repair should be performed within 7-10 days.

Question 82

A 45-year-old female presents with severe right-sided neck pain radiating down her arm. Neurological examination reveals marked weakness in wrist extension and a diminished brachioradialis reflex. Sensation to light touch is decreased over the dorsal aspect of her thumb and index finger. A herniated disc at which cervical level is most likely responsible?

Explanation

The patient's presentation of wrist extension weakness, diminished brachioradialis reflex, and sensory deficits in the thumb and index finger is classic for a C6 radiculopathy. In the cervical spine, the exiting nerve root corresponds to the lower vertebra of the motion segment, so a C5-C6 disc herniation affects the C6 nerve.

Question 83

When utilizing a locking plate to fix a severely comminuted diaphyseal fracture in osteoporotic bone, what is the primary biomechanical advantage of the fixed-angle construct?

Explanation

Locking plates utilize a threaded interface between the screw head and the plate, creating a fixed-angle construct that functions as a single load-bearing beam. They do not rely on plate-to-bone friction, which preserves periosteal blood supply and prevents screw toggle or pull-out in osteoporotic bone.

Question 84

A 4-month-old female with developmental dysplasia of the hip (DDH) is being treated in a Pavlik harness. During a follow-up visit, the mother notes the child is not actively moving her leg. Examination reveals an inability to actively extend the knee on the affected side. This complication is most directly related to which improper harness setting?

Explanation

The most common nerve injury associated with the Pavlik harness is transient femoral nerve palsy, which manifests as an inability to extend the knee. This is typically caused by excessive hip flexion in the anterior straps, compressing the nerve against the inguinal ligament.

Question 85

A 6-year-old boy sustains a completely displaced extension-type supracondylar fracture of the humerus. Radiographs demonstrate posteromedial displacement of the distal fragment. Which of the following peripheral nerves is at the highest risk of tethering or injury due to the sharply displaced proximal fragment?

Explanation

In an extension-type supracondylar humerus fracture with posteromedial displacement of the distal fragment, the proximal fragment naturally displaces anterolaterally. This anterolateral spike of bone places the radial nerve at the highest risk of injury.

Question 86

In the workup for a suspected chronic periprosthetic joint infection (PJI) of a total knee arthroplasty, joint aspiration is performed. Which of the following synovial fluid biomarkers is an antimicrobial peptide released by neutrophils and is highly specific for diagnosing PJI?

Explanation

Alpha-defensin is an antimicrobial peptide produced by neutrophils in response to pathogens. It is an extremely sensitive and highly specific synovial fluid biomarker utilized in the major criteria for diagnosing periprosthetic joint infections.

Question 87

A 24-year-old male presents with severe midfoot pain after falling from a horse with his foot caught in the stirrup. Examination reveals marked plantar ecchymosis. Radiographs show widening of the space between the first and second metatarsal bases. The primary ligament injured connects which two anatomical structures?

Explanation

The Lisfranc ligament is an essential interosseous stabilizing structure of the midfoot. It originates on the lateral aspect of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal.

Question 88

A 16-year-old boy presents with aching pain in his proximal tibia that is significantly worse at night and is dramatically relieved by taking ibuprofen. Radiographs reveal a cortical sclerosis surrounding a small radiolucent nidus. The pathophysiology of this lesion's pain mechanism is primarily driven by high levels of which substance?

Explanation

The classic presentation describes an osteoid osteoma. The nidus of an osteoid osteoma produces high concentrations of Prostaglandin E2 (PGE2) due to elevated cyclooxygenase-2 (COX-2) expression, which mediates the characteristic night pain that responds well to NSAIDs.

Question 89

When combining orthopedic implant components made of different metals, galvanic corrosion may occur. Which of the following combinations of metals carries the highest risk of clinically significant galvanic corrosion when placed in direct contact in vivo?

Explanation

Galvanic corrosion occurs when two dissimilar metals with significantly different anodic indices are placed in contact in an electrolyte fluid. The coupling of stainless steel and titanium creates a strong galvanic cell, leading to rapid corrosion, and should be avoided in orthopedic constructs.

Question 90

A 21-year-old collegiate wrestler suffers his fourth anterior shoulder dislocation. Advanced imaging reveals an anterior inferior glenoid bone defect measuring 28% of the glenoid width. Which of the following surgical procedures is considered the gold standard to restore stability in this patient?

Explanation

In the setting of recurrent anterior shoulder instability with critical anterior glenoid bone loss (typically greater than 20-25%), soft tissue repairs like a Bankart repair have unacceptably high failure rates. The Latarjet procedure (coracoid process transfer) is required to restore the bony architecture and provide a dynamic sling effect.

Question 91

A 24-year-old male falls onto an outstretched hand and sustains a non-displaced fracture of the scaphoid waist. A key factor in the high rate of nonunion for this fracture is the bone's retrograde blood supply. Which vessel serves as the primary source of intraosseous vascularity to the proximal pole of the scaphoid?

Explanation

The scaphoid receives 70-80% of its blood supply from the dorsal carpal branch of the radial artery. This vessel enters at the dorsal ridge near the scaphoid waist and supplies the proximal pole in a retrograde fashion, placing proximal fractures at a high risk of avascular necrosis.

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