Full Question & Answer Text (for Search Engines)
Question 1:
Which of the following is the strongest indication for prophylactic pinning of the asymptomatic contralateral hip in a patient presenting with unilateral Slipped Capital Femoral Epiphysis (SCFE)?
Options:
- Male gender
- Age greater than 14 years at presentation
- Underlying hypothyroidism
- Body Mass Index (BMI) greater than the 95th percentile
- Grade III severe slip on the symptomatic side
Correct Answer: Underlying hypothyroidism
Explanation:
Prophylactic pinning of the contralateral hip in SCFE is generally indicated in patients with underlying endocrinopathies (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency) or those undergoing radiation therapy, because their risk of developing bilateral SCFE approaches 50-100%. While obesity is a risk factor for SCFE, it alone is not an absolute indication for prophylactic pinning. Younger age (e.g., less than 10 years) or an open triradiate cartilage are also considered relative indications for prophylaxis due to the longer remaining growth and time at risk.
Question 2:
A surgeon is performing a posteromedial approach to the tibia to fix a Schatzker IV tibial plateau fracture involving a posteromedial shear fragment. Between which two anatomical structures is the primary surgical interval developed?
Options:
- Tibialis posterior and Flexor digitorum longus
- Medial head of the gastrocnemius and the pes anserinus
- Popliteus and Soleus
- Semimembranosus and Semitendinosus
- Medial collateral ligament and medial meniscus
Correct Answer: Medial head of the gastrocnemius and the pes anserinus
Explanation:
The posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (which is retracted posteriorly) and the pes anserinus (which is retracted anteriorly). This provides excellent exposure to the posteromedial corner of the tibial plateau, allowing for buttress plating of posteromedial shear fragments often seen in Schatzker IV and bicondylar tibial plateau fractures.
Question 3:
A 55-year-old male presents with a destructive lesion of the proximal femur. Biopsy reveals areas of low-grade hyaline cartilage directly adjacent to a high-grade pleomorphic spindle cell sarcoma with no osteoid formation. What is the most likely diagnosis?
Options:
- Clear cell chondrosarcoma
- Mesenchymal chondrosarcoma
- Dedifferentiated chondrosarcoma
- Chondroblastic osteosarcoma
- Secondary chondrosarcoma
Correct Answer: Dedifferentiated chondrosarcoma
Explanation:
Dedifferentiated chondrosarcoma is characterized by a bimorphic histological appearance featuring a low-grade cartilaginous component abruptly transitioning into a high-grade, non-cartilaginous sarcoma (e.g., osteosarcoma, fibrosarcoma, or undifferentiated pleomorphic sarcoma). The abrupt transition and absence of osteoid in the high-grade spindle cell area differentiate it from chondroblastic osteosarcoma, which typically shows malignant osteoid production mixed with malignant cartilage. Dedifferentiated chondrosarcomas carry a very poor prognosis.
Question 4:
In the context of bearing surfaces in total hip arthroplasty, which of the following best describes the toughening mechanism utilized in Zirconia-Toughened Alumina (ZTA) ceramics?
Options:
- Phase transformation from tetragonal to monoclinic structure
- Cross-linking via gamma irradiation
- Increased grain size leading to crack deflection
- Transformation from monoclinic to cubic structure
- Sacrificial surface oxidation preventing crack propagation
Correct Answer: Phase transformation from tetragonal to monoclinic structure
Explanation:
Zirconia-Toughened Alumina (ZTA) ceramics utilize a mechanism known as 'phase transformation toughening'. When a micro-crack begins to propagate through the material, the localized stress at the crack tip induces the metastable tetragonal zirconia particles to transform into a monoclinic phase. This transformation is accompanied by a 4-5% volume expansion, which places the crack tip under compressive stress and halts its propagation, significantly increasing the fracture toughness of the bearing.
Question 5:
A 65-year-old male undergoes a multi-level posterior cervical laminectomy and fusion (C3-C7) for severe cervical spondylotic myelopathy. On post-operative day 2, he develops isolated, profound weakness in right shoulder abduction and elbow flexion. Sensation and lower extremity function remain unchanged. What is the most widely accepted primary etiology for this complication?
Options:
- Direct intraoperative injury to the C5 nerve root
- Posterior spinal cord drift causing tethering of the C5 nerve root
- Epidural hematoma compressing the hemicord
- Spinal cord ischemia due to radicular artery injury
- Inadequate foraminal decompression at C6-C7
Correct Answer: Posterior spinal cord drift causing tethering of the C5 nerve root
Explanation:
The patient is experiencing a C5 palsy, a well-known complication following cervical decompression (more common after posterior approaches). The most widely accepted mechanism is the 'tethering effect'. Posterior drift of the spinal cord after decompression places tension on the cervical nerve roots. The C5 root is particularly vulnerable because it has a short, horizontal course and is tethered by the superior articular process. Most cases are motor-dominant and typically recover spontaneously over 6 months.
Question 6:
A patient with carpal tunnel syndrome reports that her symptoms are severely exacerbated when she tightly grips tools for prolonged periods. This is attributed to 'lumbrical incursion'. In what finger position do the lumbrical muscles travel furthest proximally into the carpal tunnel?
Options:
- Full composite extension of the digits
- Metacarpophalangeal joint flexion with interphalangeal joint extension
- Full composite flexion of the digits
- Isolated distal interphalangeal joint flexion
- Radial deviation with thumb opposition
Correct Answer: Full composite flexion of the digits
Explanation:
Lumbrical incursion occurs when the lumbrical muscle bellies slide proximally into the carpal tunnel, increasing intracarpal pressure and compressing the median nerve. This proximal excursion is maximal during full composite flexion of the digits (making a tight fist). This phenomenon explains why tasks requiring prolonged or repetitive tight gripping can significantly exacerbate carpal tunnel syndrome symptoms.
Question 7:
During a posterolateral corner (PLC) reconstruction of the knee, accurate anatomical placement of the fibular collateral ligament (FCL) femoral tunnel is critical. What is the correct relationship of the FCL femoral origin relative to the lateral epicondyle?
Options:
- Proximal and posterior
- Distal and anterior
- Directly over the lateral epicondyle
- Proximal and anterior
- Distal and posterior
Correct Answer: Proximal and posterior
Explanation:
The femoral origin of the Fibular Collateral Ligament (FCL) is located slightly proximal (1.4 mm) and posterior (3.1 mm) to the lateral epicondyle. The origin of the popliteus tendon is located anterior and distal to the FCL origin. Recreating this anatomic footprint is vital for restoring normal knee kinematics during posterolateral corner reconstruction.
Question 8:
Romosozumab is a monoclonal antibody utilized in the treatment of osteoporosis. It exerts its anabolic effect on bone by directly inhibiting Sclerostin. What is the primary mechanism by which Sclerostin normally acts to decrease bone formation?
Options:
- It stimulates RANKL expression by osteoblasts
- It inhibits the differentiation of osteoclast precursors
- It binds to osteoprotegerin (OPG), preventing its action
- It activates the BMP signaling pathway in osteocytes
- It binds to LRP5/6, inhibiting the Wnt/beta-catenin signaling pathway
Correct Answer: It binds to LRP5/6, inhibiting the Wnt/beta-catenin signaling pathway
Explanation:
Sclerostin, a glycoprotein encoded by the SOST gene and produced primarily by osteocytes, acts as a negative regulator of bone formation. It does this by binding to the LRP5/6 coreceptors on osteoblasts, which competitively inhibits the canonical Wnt/beta-catenin signaling pathway necessary for osteoblast differentiation and bone formation. Romosozumab blocks Sclerostin, thereby disinhibiting Wnt signaling and promoting bone formation.
Question 9:
In the surgical harvest of the Flexor Hallucis Longus (FHL) tendon for an Achilles tendon reconstruction, the dissection often proceeds to the 'Master Knot of Henry' in the midfoot to gain extra length. At this anatomical landmark, what is the relationship of the FHL tendon to the Flexor Digitorum Longus (FDL) tendon?
Options:
- FHL crosses plantar (superficial) to the FDL
- FHL crosses dorsal (deep) to the FDL
- FHL runs strictly medial and parallel to the FDL without crossing
- FHL runs strictly lateral and parallel to the FDL without crossing
- FHL merges completely with the FDL to form a common tendon
Correct Answer: FHL crosses dorsal (deep) to the FDL
Explanation:
The Master Knot of Henry is a decussation point located in the plantar midfoot just posterior to the navicular tuberosity. At this location, the Flexor Hallucis Longus (FHL) tendon crosses dorsal (deep) to the Flexor Digitorum Longus (FDL) tendon as it courses from lateral (fibula origin) to medial (great toe insertion). Understanding this relationship is crucial when harvesting the FHL to maximize length without injuring the medial plantar nerve, which lies adjacent.
Question 10:
According to the Herring Lateral Pillar Classification for Legg-Calve-Perthes disease, which of the following radiographic findings defines a Lateral Pillar Group C classification?
Options:
- No loss of height in the lateral pillar
- Less than 50% maintenance of lateral pillar height
- Greater than 50% maintenance of lateral pillar height but some lucency
- Less than 50% of the original lateral pillar height remains (greater than 50% collapse)
- Complete fragmentation of the medial pillar only
Correct Answer: Less than 50% of the original lateral pillar height remains (greater than 50% collapse)
Explanation:
The Herring Lateral Pillar classification assesses the height of the lateral pillar of the femoral head on an AP pelvis radiograph during the fragmentation stage of Perthes disease. Group A: No loss of height. Group B: Greater than 50% of lateral pillar height is maintained. Group C: Less than 50% of lateral pillar height is maintained (i.e., greater than 50% collapse). The B/C border group maintains exactly 50% height or has a narrow, depressed lateral pillar. Group C has the poorest prognosis.
Question 11:
During the anterior intrapelvic (modified Stoppa) approach for an acetabular fracture, an aberrant vessel traversing the superior pubic ramus is encountered and ligated. This 'corona mortis' represents an anastomosis between which two vascular systems?
Options:
- External iliac (or inferior epigastric) artery and the obturator artery
- Internal iliac artery and the superior gluteal artery
- External pudendal artery and the obturator artery
- Femoral artery and the inferior gluteal artery
- Inferior epigastric artery and the deep circumflex iliac artery
Correct Answer: External iliac (or inferior epigastric) artery and the obturator artery
Explanation:
The corona mortis ('crown of death') is an important anatomical variant consisting of a vascular anastomosis between the external iliac (or its branch, the inferior epigastric) system and the internal iliac (obturator) system. It lies on the posterior aspect of the superior pubic ramus, approximately 4-9 cm from the pubic symphysis. It can be arterial, venous, or both, and is highly susceptible to injury during anterior pelvic approaches, necessitating careful identification and ligation.
Question 12:
A 16-year-old female with distal femoral osteosarcoma undergoes neoadjuvant chemotherapy followed by surgical resection. The pathology report notes a Huvos Grade III response. What percentage of tumor necrosis does this grade represent?
Options:
- Less than 50% necrosis
- 50% to 90% necrosis
- 90% to 99% necrosis
- 100% necrosis (no viable tumor cells)
- Increased tumor volume with no necrosis
Correct Answer: 90% to 99% necrosis
Explanation:
The Huvos grading system assesses the histologic response of osteosarcoma to neoadjuvant chemotherapy, which is an important prognostic indicator. Grade I: Little to no response (<50% necrosis). Grade II: 50% to 90% necrosis. Grade III: 90% to 99% necrosis (predominant necrosis with scattered viable cells). Grade IV: 100% necrosis (no viable cells). A good response is typically defined as 90% or greater necrosis (Huvos Grades III and IV), which correlates with improved overall survival.
Question 13:
During a total knee arthroplasty for a severe varus deformity, the knee remains tight medially in both flexion and extension after removal of the osteophytes. According to standard sequential medial release techniques, which structure should be released first?
Options:
- Pes anserinus
- Deep medial collateral ligament (MCL)
- Superficial medial collateral ligament (MCL)
- Posteromedial corner capsule
- Semimembranosus insertion
Correct Answer: Deep medial collateral ligament (MCL)
Explanation:
In the standard sequential release for a varus knee during TKA, osteophytes are removed first. If the knee remains tight in both flexion and extension, the deep MCL (meniscotibial ligament) is typically the first structure released off the proximal medial tibia. If further release is needed, the posteromedial capsule is released (tight in extension), followed by the semimembranosus. The superficial MCL is released last, usually starting from its distal insertion, if severe varus persists. The pes anserinus is generally preserved unless extreme release is required.
Question 14:
A 35-year-old male is involved in a high-speed motor vehicle collision and sustains a 'Hangman's fracture' (traumatic spondylolisthesis of the axis). What is the classic mechanism of injury for this specific fracture pattern?
Options:
- Hyperextension and axial loading
- Hyperflexion and distraction
- Lateral bending and axial loading
- Pure rotational shear
- Axial distraction and hyperflexion
Correct Answer: Hyperextension and axial loading
Explanation:
A Hangman's fracture involves bilateral fractures through the pars interarticularis of C2 (axis). The classic mechanism of injury in modern trauma (such as an unrestrained passenger striking the dashboard/windshield) is hyperextension and axial loading. This differs from the original 'hangman's' mechanism of judicial hanging, which involves extreme hyperextension combined with sudden distraction.
Question 15:
The scaphoid bone is highly susceptible to avascular necrosis due to its tenuous blood supply. The primary vascular supply to the proximal pole of the scaphoid is derived from the dorsal carpal branch of the radial artery. Where does this branch typically enter the scaphoid?
Options:
- Directly into the proximal pole articular cartilage
- Through the volar tubercle
- Along the dorsal ridge, distal to the waist
- Via the scapholunate interosseous ligament
- At the distal articular surface near the trapezium
Correct Answer: Along the dorsal ridge, distal to the waist
Explanation:
The primary blood supply to the scaphoid comes from the dorsal carpal branch of the radial artery, which accounts for 70-80% of the bone's vascularity. This vessel enters the scaphoid through a series of foramina located along the dorsal ridge, which is distal to the waist of the scaphoid. The blood then flows in a retrograde fashion to supply the proximal pole. Fractures through the waist interrupt this retrograde flow, putting the proximal pole at high risk for avascular necrosis.
Question 16:
A 45-year-old male sustains a complete radial tear at the posterior horn root attachment of the medial meniscus. Biomechanical studies have demonstrated that this specific injury alters knee joint contact pressures in a manner most similar to which of the following?
Options:
- A partial medial meniscectomy
- A bucket-handle medial meniscus tear
- An anterior cruciate ligament rupture
- A total medial meniscectomy
- A normal, intact knee due to secondary restraints
Correct Answer: A total medial meniscectomy
Explanation:
The meniscal roots are essential for converting axial loads into hoop stresses within the meniscus. A complete tear of the posterior root of the medial meniscus completely disrupts this ability to generate hoop stresses, allowing the meniscus to extrude radially. Biomechanical studies have consistently shown that a medial meniscus posterior root tear results in a significant increase in peak contact pressures and a decrease in contact area, which are biomechanically equivalent to the derangements seen in a total medial meniscectomy.
Question 17:
In evaluating the biochemical changes in articular cartilage, how does early osteoarthritis (OA) uniquely differ from the changes seen in normal aging?
Options:
- Early OA exhibits increased water content, whereas aging exhibits decreased water content
- Early OA exhibits increased chondroitin sulfate, whereas aging exhibits increased water content
- Early OA exhibits decreased collagen synthesis, whereas aging exhibits increased collagen synthesis
- Early OA exhibits an increase in total proteoglycan content, whereas aging exhibits a decrease
- Early OA exhibits decreased keratin sulfate, whereas aging exhibits increased water content
Correct Answer: Early OA exhibits increased water content, whereas aging exhibits decreased water content
Explanation:
A hallmark of early osteoarthritis (OA) is the disruption of the collagen meshwork, leading to increased permeability and swelling of the cartilage matrix, thereby increasing the water content. Conversely, normal aging of cartilage is characterized by a decrease in water content due to changes in proteoglycan size and aggregation. In both aging and OA, the total proteoglycan content generally decreases and the modulus of elasticity changes, but the divergent direction of water content change is a classic differentiating factor.
Question 18:
The Lisfranc ligament complex is critical for midfoot stability. Which of the following accurately describes the attachments of the primary (strongest) component of the Lisfranc ligament?
Options:
- Dorsal surface of the medial cuneiform to the dorsal base of the 2nd metatarsal
- Plantar-lateral aspect of the medial cuneiform to the plantar-medial base of the 2nd metatarsal
- Plantar aspect of the middle cuneiform to the base of the 2nd metatarsal
- Plantar aspect of the lateral cuneiform to the base of the 3rd metatarsal
- Medial cuneiform to the base of the 1st metatarsal
Correct Answer: Plantar-lateral aspect of the medial cuneiform to the plantar-medial base of the 2nd metatarsal
Explanation:
The Lisfranc ligament complex consists of dorsal, interosseous, and plantar ligaments. The plantar (and interosseous) components are the thickest and strongest. The classic 'Lisfranc ligament' refers specifically to the strong interosseous/plantar band connecting the plantar-lateral aspect of the medial cuneiform to the plantar-medial aspect of the base of the second metatarsal. Notably, there is no intermetatarsal ligament connecting the bases of the 1st and 2nd metatarsals, making this articulation entirely dependent on the Lisfranc ligament.
Question 19:
A 4-month-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At the follow-up appointment, the parents report that the baby has stopped actively extending the knee on the treated side. Physical exam confirms absent active knee extension and a diminished patellar reflex. What was the most likely error in the application of the harness?
Options:
- Excessive hip flexion
- Excessive hip abduction
- Inadequate hip flexion
- Excessive hip extension
- Inadequate hip abduction
Correct Answer: Excessive hip flexion
Explanation:
The infant has developed a femoral nerve palsy, a known complication of Pavlik harness treatment. This is typically caused by hyperflexion of the hips, which compresses the femoral nerve against the inguinal ligament or pubis. The treatment is to temporarily remove the harness or adjust the anterior straps to reduce flexion. Excessive abduction is associated with a different, severe complication: avascular necrosis (AVN) of the femoral head.
Question 20:
A 65-year-old female sustains a nondisplaced distal radius fracture and is treated non-operatively in a short arm cast. Six weeks later, she presents with an inability to actively extend her thumb interphalangeal joint. What is the most widely accepted mechanism for this specific complication following a nondisplaced distal radius fracture?
Options:
- Sharp mechanical attrition of the tendon against a displaced dorsal cortical fragment
- Ischemic necrosis of the tendon secondary to hematoma and increased pressure within the intact third extensor compartment
- Direct injury to the posterior interosseous nerve during the initial trauma
- Iatrogenic tethering of the tendon by a poorly molded cast
- Avulsion of the extensor pollicis longus muscle belly at the musculotendinous junction
Correct Answer: Ischemic necrosis of the tendon secondary to hematoma and increased pressure within the intact third extensor compartment
Explanation:
The patient has experienced an Extensor Pollicis Longus (EPL) tendon rupture. In the setting of a non-displaced or minimally displaced distal radius fracture treated non-operatively, the prevailing theory for EPL rupture is vascular watershed ischemia. The intact extensor retinaculum confines the third dorsal compartment. Bleeding and edema from the fracture increase compartment pressure, compressing the precarious vascular supply to the EPL as it wraps around Lister's tubercle, leading to focal ischemic necrosis and delayed rupture (often around 4-8 weeks). Mechanical attrition is the usual cause after volar plating with prominent dorsal screws.
Question 21:
A 35-year-old male presents with indolent pain in his lower leg. Radiographs reveal a multi-lobulated, lytic, eccentric lesion in the anterior tibial diaphysis. Biopsy reveals islands of epithelial cells in a fibrous stroma. Which of the following immunohistochemical markers is most likely positive?
Options:
- S-100
- Cytokeratin
- Vimentin only
- CD99
- Desmin
Correct Answer: Cytokeratin
Explanation:
Adamantinoma is a low-grade malignant bone tumor that typically occurs in the anterior diaphysis of the tibia. It is characterized by biphasic histology (epithelial and osteofibrous components) and stains positive for epithelial markers such as cytokeratin, distinguishing it from osteofibrous dysplasia.
Question 22:
In the surgical management of a 'terrible triad' injury of the elbow (elbow dislocation, radial head fracture, coronoid fracture), which of the following is the standard recommended sequence of repair to restore stability?
Options:
- Lateral collateral ligament repair, coronoid fixation, radial head fixation/replacement
- Radial head fixation, coronoid fixation, lateral collateral ligament repair
- Coronoid fixation, radial head fixation/replacement, lateral collateral ligament repair
- Lateral collateral ligament repair, radial head fixation, coronoid fixation
- Coronoid fixation, lateral collateral ligament repair, radial head fixation/replacement
Correct Answer: Coronoid fixation, radial head fixation/replacement, lateral collateral ligament repair
Explanation:
The standard surgical sequence for a terrible triad injury of the elbow begins with deep to superficial repair: 1. Fixation of the coronoid fracture (or anterior capsule), 2. Fixation or replacement of the radial head, and 3. Repair of the lateral collateral ligament (LCL) complex.
Question 23:
A 24-year-old male is involved in a motor vehicle collision and sustains a traumatic spondylolisthesis of C2 (Hangman's fracture). Radiographs show a C2-C3 angulation of 15 degrees and translation of 4 mm, with severe disruption of the C2-C3 disc space. According to the Levine-Edwards classification, this is a Type IIA fracture. What is the most appropriate initial management?
Options:
- Immediate halo-gravity traction with 15 lbs of weight
- Application of a halo vest in slight distraction
- Application of a halo vest in slight compression and extension
- Anterior C2-C3 cervical discectomy and fusion
- Posterior C1-C3 fusion
Correct Answer: Application of a halo vest in slight compression and extension
Explanation:
Levine-Edwards Type IIA fractures involve severe angulation with minimal translation and indicate a flexion-distraction injury with an intact anterior longitudinal ligament. Traction is strictly contraindicated as it can cause over-distraction and neurologic injury. Treatment consists of closed reduction in extension and slight compression under fluoroscopy, followed by halo vest application.
Question 24:
The spring ligament (plantar calcaneonavicular ligament) is a primary static stabilizer of the medial longitudinal arch of the foot. It spans from the sustentaculum tali to the navicular. Which of the following tendons provides the most significant dynamic support to this ligament and the medial arch?
Options:
- Tibialis anterior
- Peroneus longus
- Tibialis posterior
- Flexor hallucis longus
- Flexor digitorum longus
Correct Answer: Tibialis posterior
Explanation:
The tibialis posterior tendon is the primary dynamic stabilizer of the medial longitudinal arch. Its dysfunction (Posterior Tibial Tendon Dysfunction) leads to increased stress and subsequent failure of the static stabilizers, particularly the spring ligament, resulting in adult acquired flatfoot deformity.
Question 25:
A 28-year-old football player sustains a twisting injury to his knee. On physical examination, the dial test is performed. The examiner notes 15 degrees of increased external rotation of the tibia compared to the contralateral normal knee at 30 degrees of knee flexion. However, at 90 degrees of knee flexion, the external rotation is equal bilaterally. Which of the following structures is most likely injured?
Options:
- Anterior cruciate ligament and posterolateral corner
- Isolated posterior cruciate ligament
- Isolated posterolateral corner
- Posterior cruciate ligament and posterolateral corner
- Medial collateral ligament and posterior oblique ligament
Correct Answer: Isolated posterolateral corner
Explanation:
The dial test evaluates for posterolateral instability. An increase of >10 degrees of external rotation at 30 degrees of flexion, but not at 90 degrees, indicates an isolated posterolateral corner (PLC) injury. Increased external rotation at both 30 and 90 degrees suggests a combined PCL and PLC injury.
Question 26:
A 40-year-old male arrives at the trauma bay with hemodynamic instability following a crush injury to the pelvis. AP pelvis radiograph demonstrates an APC-III pelvic ring injury. An emergent pelvic binder is to be applied. At what anatomic level should the binder be centered for optimal reduction of the pelvic volume?
Options:
- Over the iliac crests
- Midway between the iliac crests and the pubic symphysis
- Centered over the greater trochanters
- Directly over the lower lumbar spine and sacrum
- Centered over the proximal femoral shafts
Correct Answer: Centered over the greater trochanters
Explanation:
Pelvic binders must be centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is a common error and is less effective at closing the symphysis pubis; it can even paradoxically worsen inferior ring displacement.
Question 27:
A 13-year-old girl sustains an ankle injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibia. Which of the following best describes the pathoanatomy and mechanism of this specific injury?
Options:
- Plantar flexion injury causing avulsion via the anterior talofibular ligament
- External rotation injury causing avulsion via the anterior inferior tibiofibular ligament
- Supination-inversion injury causing avulsion via the calcaneofibular ligament
- Axial loading causing impaction of the lateral tibial plafond
- Pronation-abduction injury causing a compression fracture of the lateral physis
Correct Answer: External rotation injury causing avulsion via the anterior inferior tibiofibular ligament
Explanation:
A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia. It occurs in adolescents (usually 12-14 years old) because the distal tibial physis closes from central to anteromedial to posteromedial, and finally the anterolateral portion closes last. An external rotation force causes the anterior inferior tibiofibular ligament (AITFL) to avulse this unfused anterolateral fragment.
Question 28:
In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced the rate of osteolysis compared to conventional polyethylene. Which of the following manufacturing processes is utilized to eliminate free radicals and improve the oxidation resistance of HXLPE, albeit at the cost of decreasing its fatigue strength?
Options:
- Cold irradiation in an oxygen-rich environment
- Remelting the polyethylene above its melting temperature
- Annealing the polyethylene below its melting temperature
- Addition of barium sulfate during extrusion
- Ethylene oxide sterilization
Correct Answer: Remelting the polyethylene above its melting temperature
Explanation:
Irradiation of polyethylene causes cross-linking, which improves wear resistance but also generates free radicals that can lead to oxidation and degradation. To eliminate these free radicals, the polyethylene is thermally treated. Remelting (heating above the melting point, ~135 degrees Celsius) eliminates all free radicals but decreases crystallinity and fatigue strength. Annealing (heating below the melting point) preserves fatigue strength but leaves some trapped free radicals.
Question 29:
Recombinant human bone morphogenetic proteins (rhBMPs) are used clinically to enhance bone healing. BMPs belong to the TGF-beta superfamily. They initiate intracellular signaling primarily by binding to transmembrane receptors that activate which of the following downstream molecules?
Options:
- JAK/STAT pathway
- cAMP/PKA pathway
- Smad proteins
- Wnt/beta-catenin
- MAP kinases
Correct Answer: Smad proteins
Explanation:
Bone morphogenetic proteins (BMPs) bind to serine/threonine kinase receptors (Type I and Type II) on the cell surface. This binding phosphorylates and activates receptor-regulated Smads (R-Smads, specifically Smad 1, 5, and 8), which then complex with Co-Smad (Smad 4) and translocate to the nucleus to regulate the transcription of osteogenic genes.
Question 30:
Following surgical repair of a zone II flexor tendon injury, early active motion protocols are frequently utilized to prevent adhesion formation. What is the primary biological mechanism by which these protocols promote intrinsic tendon healing over extrinsic healing?
Options:
- By increasing the invasion of fibroblasts from the surrounding tendon sheath
- By stimulating epitenon cells to migrate and proliferate into the repair site
- By enhancing the vascular ingrowth from the vincular system
- By promoting the deposition of type III collagen rather than type I collagen
- By completely halting the inflammatory phase of wound healing
Correct Answer: By stimulating epitenon cells to migrate and proliferate into the repair site
Explanation:
Tendon healing occurs via intrinsic and extrinsic pathways. Extrinsic healing relies on cells from the surrounding sheath and leads to adhesions. Intrinsic healing is mediated by epitenon and endotenon cells. Early controlled mobilization stimulates the intrinsic healing pathway, causing epitenon cells to migrate into the repair site and synthesize collagen, while simultaneously mechanically preventing extrinsically derived tissue adhesions from stabilizing.
Question 31:
A 28-year-old male sustains a closed spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture). On initial examination, he is noted to have a complete radial nerve palsy. He is managed non-operatively in a functional brace. At what time point should an EMG and nerve conduction study be ordered if there is no clinical evidence of radial nerve recovery?
Options:
- 2 weeks post-injury
- 6 weeks post-injury
- 12 weeks post-injury
- 6 months post-injury
- 1 year post-injury
Correct Answer: 12 weeks post-injury
Explanation:
Radial nerve palsy associated with closed humeral shaft fractures (including Holstein-Lewis types) is usually a neuropraxia or axonotmesis that recovers spontaneously. Initial management is observation. If there is no clinical evidence of nerve recovery (e.g., return of brachioradialis or extensor carpi radialis longus function) at 3 to 4 months (12-16 weeks) post-injury, EMG and nerve conduction studies are indicated to evaluate for reinnervation or the need for surgical exploration.
Question 32:
A 14-year-old boy presents with a painful mass in his left thigh. Radiographs demonstrate an aggressive, permeative diaphyseal lesion in the femur with a prominent 'onion-skin' periosteal reaction. Core needle biopsy confirms the diagnosis of Ewing sarcoma. Which of the following chromosomal translocations is most characteristic of this tumor?
Options:
- t(11;22)(q24;q12)
- t(X;18)(p11;q11)
- t(12;16)(q13;p11)
- t(2;13)(q35;q14)
- t(9;22)(q34;q11)
Correct Answer: t(11;22)(q24;q12)
Explanation:
Ewing sarcoma is characterized by the t(11;22)(q24;q12) translocation in approximately 85-90% of cases, leading to the fusion of the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11. t(X;18) is seen in synovial sarcoma. t(12;16) is seen in myxoid liposarcoma. t(2;13) is seen in alveolar rhabdomyosarcoma.
Question 33:
A 55-year-old male with long-standing, poorly controlled type 2 diabetes presents with a swollen, erythematous, and warm right foot without open ulceration. Radiographs demonstrate periarticular fragmentation, subluxation, and debris at the tarsometatarsal joints. According to the Eichenholtz classification, what stage of Charcot arthropathy does this represent, and what is the standard initial treatment?
Options:
- Stage 0; treated with broad-spectrum intravenous antibiotics
- Stage 1; treated with a total contact cast and non-weight bearing
- Stage 2; treated with an ankle-foot orthosis (AFO) and weight bearing as tolerated
- Stage 3; treated with primary arthrodesis of the midfoot
- Stage 1; treated with immediate surgical debridement and external fixation
Correct Answer: Stage 1; treated with a total contact cast and non-weight bearing
Explanation:
Eichenholtz Stage 1 is the developmental/fragmentation phase, characterized clinically by a red, hot, swollen foot and radiographically by bony fragmentation, joint dislocation, and debris. The cornerstone of treatment in Stage 1 Charcot arthropathy is immobilization and offloading, typically using a total contact cast (TCC) to prevent further deformity until the acute inflammatory phase resolves (Stage 2: coalescence).
Question 34:
A 65-year-old female presents with bilateral leg pain and cramping that worsens with walking and prolonged standing. She states that the pain is relieved when she sits down or leans forward over a shopping cart. The stationary bicycle test is performed to differentiate neurogenic claudication from vascular claudication. Which of the following responses on the stationary bicycle test strongly supports a diagnosis of neurogenic claudication?
Options:
- Leg pain occurs at the same distance regardless of spinal posture
- Leg pain is delayed or prevented when cycling with the spine flexed compared to cycling with the spine extended
- Calf pain occurs rapidly and is accompanied by diminished pedal pulses after cycling
- Leg pain is reproduced only when pedaling against high resistance in a flexed posture
- Leg pain is completely unaffected by either cycling or walking
Correct Answer: Leg pain is delayed or prevented when cycling with the spine flexed compared to cycling with the spine extended
Explanation:
The stationary bicycle test (van Gelderen bicycle test) differentiates neurogenic from vascular claudication. In neurogenic claudication (due to lumbar spinal stenosis), spinal flexion increases the cross-sectional area of the spinal canal and neural foramina, relieving compression on the nerve roots. Therefore, the patient can pedal a stationary bicycle longer and with less pain when leaning forward (flexed spine) compared to pedaling in an upright/extended posture. Vascular claudication is exertion-dependent and not posture-dependent.
Question 35:
A 22-year-old collegiate baseball pitcher presents with deep shoulder pain and decreased throwing velocity. MR arthrogram demonstrates detachment of the superior labrum and the origin of the long head of the biceps tendon from the glenoid, with an intact labral margin elsewhere. This corresponds to a Snyder Type II SLAP tear. After failed conservative management, what is the most appropriate surgical treatment for this young overhead athlete?
Options:
- Debridement of the superior labrum with intact biceps anchor
- Biceps tenodesis and labral debridement
- Biceps tenotomy
- Arthroscopic repair of the superior labrum to the glenoid
- Open Latarjet procedure
Correct Answer: Arthroscopic repair of the superior labrum to the glenoid
Explanation:
A Snyder Type II SLAP tear involves detachment of the superior labrum and biceps anchor from the superior glenoid. In young, active patients, especially overhead athletes (like pitchers), arthroscopic repair of the superior labrum back to the glenoid is the standard of care to restore normal anatomy and shoulder mechanics. In older patients (>40-45 years), biceps tenodesis is generally preferred due to higher stiffness and failure rates associated with SLAP repairs in that age group.
Question 36:
Articular cartilage is highly specialized to withstand compressive and shear forces. It is structurally divided into four distinct zones. Which of the following zones contains the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers oriented perpendicular to the articular surface?
Options:
- Superficial (tangential) zone
- Middle (transitional) zone
- Deep (radial) zone
- Calcified cartilage zone
- Subchondral bone plate
Correct Answer: Deep (radial) zone
Explanation:
The deep (radial) zone of articular cartilage contains the largest diameter collagen fibrils arranged perpendicular to the articular surface, which provides the greatest resistance to compressive forces. It also has the highest concentration of proteoglycans and the lowest water content of the uncalcified zones. The superficial zone has collagen parallel to the joint surface and the highest water content.
Question 37:
A 6-week-old female is diagnosed with Developmental Dysplasia of the Hip (DDH) and placed in a Pavlik harness. During a follow-up visit, the orthopaedic surgeon notes decreased spontaneous movement of the patient's knee and an absent patellar reflex on the affected side. This complication is most likely due to which of the following mechanical positioning errors in the harness?
Options:
- Excessive abduction of the hips
- Inadequate abduction of the hips
- Excessive flexion of the hips
- Inadequate flexion of the hips
- Excessive internal rotation of the hips
Correct Answer: Excessive flexion of the hips
Explanation:
The complication described is a femoral nerve palsy, which manifests as decreased active knee extension and an absent patellar reflex. In a Pavlik harness, this is classically caused by hyperflexion of the hips (typically > 120 degrees), which compresses the femoral nerve against the inguinal ligament. Excessive abduction is associated with avascular necrosis (AVN) of the femoral head.
Question 38:
During a posterior-stabilized total knee arthroplasty (TKA), after making the initial bone cuts, the surgeon uses spacer blocks to assess the gaps. The knee is found to be balanced and symmetrical in extension, but it is unacceptably tight in flexion. Which of the following is the most appropriate surgical step to balance the knee?
Options:
- Recut the distal femur to remove more bone
- Downsize the femoral component and use a thicker polyethylene insert
- Decrease the posterior slope of the tibial cut
- Upsize the femoral component to increase the posterior offset
- Recut the posterior femur to remove more bone or use a smaller femoral component
Correct Answer: Recut the posterior femur to remove more bone or use a smaller femoral component
Explanation:
If a TKA is balanced in extension but tight in flexion, the flexion gap needs to be increased without altering the extension gap. The flexion gap is primarily determined by the posterior femoral condyles and the tibial cut. Since the extension gap is fine, the tibial cut should not be altered (as it affects both gaps equally). Therefore, the solution is to remove more posterior femoral bone. This is accomplished by downsizing the femoral component (which shifts the posterior cut anteriorly) or recutting the posterior femur with an anterior referencing system.
Question 39:
Nonunion is a recognized complication of scaphoid waist fractures, largely due to its tenuous blood supply. The primary blood supply to the proximal pole of the scaphoid enters the bone at which anatomical location and is derived from which artery?
Options:
- Enters the proximal pole directly from the ulnar artery
- Enters the distal pole and waist primarily from the dorsal carpal branch of the radial artery and flows in a retrograde fashion
- Enters the proximal pole directly from the superficial palmar arch
- Enters the volar aspect of the waist from the anterior interosseous artery and flows in an antegrade fashion
- Enters the distal pole from the deep palmar arch and flows in an antegrade fashion
Correct Answer: Enters the distal pole and waist primarily from the dorsal carpal branch of the radial artery and flows in a retrograde fashion
Explanation:
Approximately 70-80% of the scaphoid's blood supply comes from the dorsal carpal branch of the radial artery, which enters the bone distally at the dorsal ridge (distal to the waist) and flows in a retrograde fashion to supply the proximal pole. This retrograde blood supply explains the high incidence of avascular necrosis and nonunion in fractures of the scaphoid waist and proximal pole.
Question 40:
A 32-year-old male sustains a severe closed tibial shaft fracture. Two hours later in the emergency department, he complains of severe leg pain out of proportion to the injury, unrelieved by intravenous opioids. His blood pressure is 110/70 mmHg. Intracompartmental pressure monitoring of the anterior compartment yields a value of 45 mmHg. Which of the following calculations is the most reliable indicator for emergency fasciotomy?
Options:
- Absolute compartment pressure > 30 mmHg regardless of blood pressure
- Delta pressure (Mean Arterial Pressure - Compartment Pressure) < 30 mmHg
- Delta pressure (Diastolic Blood Pressure - Compartment Pressure) < 30 mmHg
- Delta pressure (Systolic Blood Pressure - Compartment Pressure) < 30 mmHg
- The ratio of Compartment Pressure to Diastolic Blood Pressure > 0.5
Correct Answer: Delta pressure (Diastolic Blood Pressure - Compartment Pressure) < 30 mmHg
Explanation:
The most reliable objective criteria for diagnosing acute compartment syndrome is a delta pressure (ΔP) of less than 30 mmHg. Delta pressure is defined as the Diastolic Blood Pressure minus the Compartment Pressure (ΔP = DBP - CP). In this scenario, DBP is 70 and CP is 45. ΔP = 70 - 45 = 25 mmHg. Since this is less than 30 mmHg, emergent four-compartment fasciotomy is indicated. Absolute pressure thresholds (e.g., > 30 mmHg) are less accurate as they do not account for patient perfusion pressure, which fluctuates.
Question 41:
A 13-year-old boy sustains an ankle injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis. Which of the following describes the most likely deforming force and the ligamentous structure attached to this avulsed fragment?
Options:
- Inversion, calcaneofibular ligament
- External rotation, anterior inferior tibiofibular ligament
- Plantar flexion, anterior talofibular ligament
- Internal rotation, posterior inferior tibiofibular ligament
- Eversion, deltoid ligament
Correct Answer: External rotation, anterior inferior tibiofibular ligament
Explanation:
This is a classic juvenile Tillaux fracture, which is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It occurs due to an external rotation force. The anterior inferior tibiofibular ligament (AITFL) is intact and avulses the anterolateral epiphysis because, in this age group, the physis closes from central to anteromedial to posteromedial, leaving the anterolateral portion open and vulnerable last.
Question 42:
A 55-year-old active man presents with a high-pitched 'squeaking' sound coming from his hip during ambulation. He underwent a primary total hip arthroplasty 3 years ago. What bearing surface combination is most classically associated with this specific phenomenon?
Options:
- Metal-on-polyethylene
- Ceramic-on-polyethylene
- Ceramic-on-ceramic
- Metal-on-metal
- Oxinium-on-highly cross-linked polyethylene
Correct Answer: Ceramic-on-ceramic
Explanation:
Squeaking is a well-documented and specific complication associated with ceramic-on-ceramic bearing surfaces in total hip arthroplasty. It is thought to be caused by microseparation, stripe wear, component malposition (e.g., edge loading), or third-body debris altering the fluid film lubrication.
Question 43:
During the surgical management of a 'terrible triad' injury of the elbow (elbow dislocation, radial head fracture, and coronoid fracture), repair of the lateral ulnar collateral ligament (LUCL) is a critical step to restore stability. What are the correct anatomical origin and insertion of the LUCL?
Options:
- Lateral epicondyle to the radial neck
- Lateral epicondyle to the supinator crest of the ulna
- Capitellum to the annular ligament
- Lateral epicondyle to the coronoid process
- Radial head to the supinator crest of the ulna
Correct Answer: Lateral epicondyle to the supinator crest of the ulna
Explanation:
The lateral ulnar collateral ligament (LUCL) is the primary restraint to posterolateral rotatory instability. It originates on the lateral epicondyle of the humerus and inserts distally onto the supinator crest of the proximal ulna.
Question 44:
During a posterior cruciate ligament (PCL) reconstruction, understanding the biomechanics of the native bundles is essential to reproduce normal knee kinematics. Which of the following best describes the tensioning pattern of the anterolateral (AL) and posteromedial (PM) bundles of the native PCL?
Options:
- AL bundle is tight in extension; PM bundle is tight in flexion
- AL bundle is tight in flexion; PM bundle is tight in extension
- Both bundles are equally tight in deep flexion
- Both bundles are equally tight in full extension
- AL bundle is tight in internal rotation; PM bundle is tight in external rotation
Correct Answer: AL bundle is tight in flexion; PM bundle is tight in extension
Explanation:
The PCL is composed of two main bundles: the larger anterolateral (AL) bundle and the smaller posteromedial (PM) bundle. The AL bundle is tight in flexion and lax in extension, while the PM bundle is tight in extension and lax in flexion. This reciprocal relationship is crucial when tensioning grafts during PCL reconstruction.
Question 45:
Imaging reveals a traumatic spondylolisthesis of the axis (Hangman's fracture) in a 24-year-old male following a motor vehicle accident. The lateral radiograph demonstrates severe angulation but minimal translation at the C2-C3 junction, indicative of a Levine-Edwards Type IIa fracture. What is the classic contraindication in the acute management of this specific fracture pattern?
Options:
- Rigid cervical collar
- Halo vest immobilization
- Cervical traction
- Anterior C2-C3 discectomy and fusion
- Posterior C2-C3 pedicle screw fixation
Correct Answer: Cervical traction
Explanation:
A Levine-Edwards Type IIa Hangman's fracture features severe angulation with minimal translation. It is caused by a flexion-distraction injury, and the C2-C3 disc space is significantly disrupted. Cervical traction is strictly contraindicated as it can cause catastrophic distraction at the C2-C3 space and subsequent neurologic injury. Treatment usually involves gentle compression/extension in a Halo vest.
Question 46:
A 30-year-old male presents with a slowly enlarging, painless mass deep in the soft tissues near his knee joint. Biopsy reveals a biphasic tumor with both epithelial and spindle cell components. Molecular testing is ordered. Which of the following chromosomal translocations is diagnostic of this neoplasm?
Options:
- t(11;22)(q24;q12)
- t(X;18)(p11;q11)
- t(12;16)(q13;p11)
- t(2;13)(q35;q14)
- t(9;22)(q22;q12)
Correct Answer: t(X;18)(p11;q11)
Explanation:
The patient has a synovial sarcoma, which characteristically demonstrates the t(X;18)(p11;q11) translocation, resulting in the SYT-SSX fusion gene. t(11;22) is seen in Ewing sarcoma; t(12;16) in myxoid liposarcoma; t(2;13) in alveolar rhabdomyosarcoma; and t(9;22) in extraskeletal myxoid chondrosarcoma.
Question 47:
A 55-year-old patient with poorly controlled diabetes mellitus presents with a red, hot, swollen right foot. Radiographs demonstrate periarticular debris, fragmentation of the tarsal bones, and early joint subluxation. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent?
Options:
- Stage 0 (prodromal)
- Stage 1 (developmental/fragmentation)
- Stage 2 (coalescence)
- Stage 3 (reconstruction/consolidation)
- Stage 4 (ankylosis)
Correct Answer: Stage 1 (developmental/fragmentation)
Explanation:
Eichenholtz Stage 1 (developmental/fragmentation stage) is characterized clinically by a red, hot, swollen foot and radiographically by bone fragmentation, periarticular debris, and joint subluxation/dislocation. Stage 2 (coalescence) shows absorption of fine debris and early fusion. Stage 3 (consolidation) shows remodeling and rounding of bone ends.
Question 48:
A 40-year-old patient sustained a high radial nerve palsy following a humerus shaft fracture 12 months ago with no clinical or EMG signs of recovery. Which of the following tendon transfer combinations represents the classic modified Green transfer to restore wrist, finger, and thumb extension?
Options:
- Pronator teres to extensor carpi radialis brevis; flexor carpi radialis to extensor digitorum communis; palmaris longus to extensor pollicis longus
- Pronator teres to extensor carpi radialis longus; flexor carpi radialis to extensor digitorum communis; flexor digitorum superficialis to extensor pollicis longus
- Pronator teres to extensor carpi radialis brevis; flexor carpi ulnaris to extensor digitorum communis; palmaris longus to extensor pollicis longus
- Brachioradialis to extensor carpi radialis brevis; flexor carpi ulnaris to extensor digitorum communis; flexor carpi radialis to extensor pollicis longus
- Pronator teres to extensor carpi ulnaris; flexor digitorum superficialis to extensor digitorum communis; palmaris longus to extensor pollicis longus
Correct Answer: Pronator teres to extensor carpi radialis brevis; flexor carpi ulnaris to extensor digitorum communis; palmaris longus to extensor pollicis longus
Explanation:
The classic modified Green transfer for radial nerve palsy uses the Pronator Teres (PT) to Extensor Carpi Radialis Brevis (ECRB) for wrist extension, the Flexor Carpi Ulnaris (FCU) to the Extensor Digitorum Communis (EDC) for finger extension, and the Palmaris Longus (PL) to the Extensor Pollicis Longus (EPL) for thumb extension. (The Boyes transfer traditionally utilizes the FDS rather than the FCU for finger extension).
Question 49:
Articular cartilage exhibits viscoelastic properties during mechanical loading. Which of the following statements best defines the biomechanical phenomenon of 'stress relaxation'?
Options:
- A constant load is applied, leading to a slow, progressive increase in deformation over time.
- A constant deformation is applied, leading to a slow, progressive decrease in the internal stress over time.
- The energy lost as heat during a single continuous loading and unloading cycle.
- The point at which a material transitions from elastic to plastic deformation.
- The application of cyclic loading causing failure at a stress lower than the ultimate tensile strength.
Correct Answer: A constant deformation is applied, leading to a slow, progressive decrease in the internal stress over time.
Explanation:
Stress relaxation occurs when a viscoelastic material is subjected to a constant deformation (strain), resulting in a gradual decrease in internal stress over time as the fluid within the matrix redistributes. Creep, by contrast, is the gradual increase in deformation when a constant load (stress) is applied.
Question 50:
A 12-year-old boy presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE) of the left hip. Prophylactic pinning of the contralateral right hip is discussed with the family. Which of the following patient factors is considered the strongest absolute indication for prophylactic fixation of the asymptomatic contralateral hip?
Options:
- Patient age over 14 years
- Male sex
- Anteroposterior alpha angle > 55 degrees
- Presence of an underlying endocrine disorder
- Body Mass Index (BMI) greater than the 95th percentile
Correct Answer: Presence of an underlying endocrine disorder
Explanation:
Patients with underlying endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) have an exceptionally high rate (up to 100% in some series) of developing bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly indicated in these cases. The other options are relative considerations but not as definitive as a diagnosed endocrinopathy.
Question 51:
A 72-year-old woman undergoes revision total hip arthroplasty for recurrent instability due to severe abductor deficiency. A constrained acetabular liner is placed to prevent further dislocations. Which of the following is the most frequent mode of failure associated with constrained liners?
Options:
- Aseptic loosening at the bone-implant interface of the acetabular shell
- Accelerated polyethylene wear leading to severe pelvic osteolysis
- Fatigue fracture of the modular femoral neck
- Dislocation of the femoral head from the constrained locking mechanism
- Dissociation of the constrained liner from the metal acetabular shell
Correct Answer: Aseptic loosening at the bone-implant interface of the acetabular shell
Explanation:
While constrained liners prevent the femoral head from dislocating, they do so by transferring the impaction and impingement forces directly to the acetabular shell-bone interface. This increased stress most commonly leads to aseptic loosening of the acetabular component. Dislocation from the mechanism or liner dissociation are less common modes of failure.
Question 52:
A 30-year-old man sustains a Pauwels type III (70-degree) femoral neck fracture. Biomechanically, what is the primary deforming force at the fracture site that surgical fixation must overcome, and what is the preferred characteristic of the construct to achieve optimal stability?
Options:
- Compressive forces; screws placed perpendicular to the femoral shaft
- Shear forces; construct designed to neutralize shear (e.g., length-stable device or screws placed perpendicular to the fracture line)
- Tensile forces; tension band wiring combined with cancellous screws
- Rotational forces; a single large diameter dynamic hip screw
- Distraction forces; an intramedullary nail with dynamic interlocking
Correct Answer: Shear forces; construct designed to neutralize shear (e.g., length-stable device or screws placed perpendicular to the fracture line)
Explanation:
A Pauwels type III fracture is characterized by a vertical fracture line (angle > 50 degrees). Biomechanically, this creates extraordinarily high shear forces at the fracture site, which promote varus displacement and nonunion. Standard sliding hip screws without derotation components may allow excessive sliding and collapse. Fixation must primarily neutralize these shear forces, often through length-stable constructs (like a fixed-angle blade plate or proximal femoral locking plate) or multiple screws placed to cross the vertical fracture orthogonally.
Question 53:
A 19-year-old female collegiate swimmer presents with bilateral shoulder pain and a feeling of the shoulders 'slipping.' Examination shows a positive sulcus sign bilaterally that does not decrease with external rotation, and a positive apprehension test. Initial management with 6 months of targeted physical therapy has failed. If surgery is performed, which anatomical structure is the primary target for plication or shift?
Options:
- Superior glenohumeral ligament (SGHL)
- Middle glenohumeral ligament (MGHL)
- Rotator interval
- Inferior glenohumeral ligament (IGHL) complex
- Coracoacromial ligament
Correct Answer: Inferior glenohumeral ligament (IGHL) complex
Explanation:
The patient has Multidirectional Instability (MDI) of the shoulder, characterized by generalized laxity and a sulcus sign that persists in external rotation. When extensive conservative management fails, the surgical procedure of choice is an inferior capsular shift. The target of this shift is the redundant inferior capsular pouch, formed by the inferior glenohumeral ligament (IGHL) complex, which is the primary restraint to inferior translation in abduction.
Question 54:
A 75-year-old male presents with neck pain after a low-energy ground-level fall. CT scan reveals a Type II odontoid fracture. Which of the following factors is most strongly associated with an increased risk of nonunion if this fracture is treated non-operatively with rigid cervical orthosis?
Options:
- Fracture displacement of 2 mm
- Anterior angulation of 5 degrees
- Patient age > 65 years
- Delay in treatment of 3 days
- Associated isolated posterior arch fracture of C1
Correct Answer: Patient age > 65 years
Explanation:
Risk factors for nonunion of Type II odontoid fractures include patient age > 50-65 years, fracture displacement > 5 mm, posterior displacement, and a delay in diagnosis/treatment of > 1 week. Among the options provided, age > 65 is an established strong independent risk factor for nonunion, often prompting consideration for early surgical stabilization in suitable candidates.
Question 55:
A 60-year-old man presents with a painful mass in his right pelvis. Biopsy reveals a primary conventional chondrosarcoma, grade II. What is the most appropriate definitive management for this patient?
Options:
- Neoadjuvant chemotherapy followed by wide surgical resection
- Wide surgical resection alone
- Intralesional curettage with local adjuvant therapy (e.g., phenol, argon beam)
- Definitive radiation therapy
- Wide surgical resection followed by adjuvant chemotherapy
Correct Answer: Wide surgical resection alone
Explanation:
Conventional chondrosarcomas are generally poorly responsive to both chemotherapy and radiation therapy. The mainstay of treatment for intermediate to high-grade (Grade II or III) and pelvic chondrosarcomas is wide surgical resection with negative margins. Intralesional curettage is reserved only for benign or specific low-grade (Grade I) cartilaginous tumors in the appendicular skeleton.
Question 56:
A 25-year-old rugby player sustains a purely ligamentous Lisfranc injury with 3 mm of diastasis between the medial and middle cuneiforms and bases of the 1st and 2nd metatarsals. Based on recent prospective randomized controlled trials, how does primary arthrodesis compare to open reduction and internal fixation (ORIF) for this specific injury pattern?
Options:
- ORIF provides superior functional outcomes at 2 years.
- Primary arthrodesis has a higher rate of hardware-related complications.
- Primary arthrodesis results in fewer unplanned secondary surgeries.
- ORIF is associated with a lower rate of post-traumatic osteoarthritis.
- There is no difference in the rate of secondary surgeries between the two groups.
Correct Answer: Primary arthrodesis results in fewer unplanned secondary surgeries.
Explanation:
For purely ligamentous Lisfranc injuries, studies (such as the landmark trial by Ly and Coetzee) have demonstrated that primary arthrodesis of the medial columns leads to better short- to medium-term functional outcomes and significantly fewer unplanned secondary surgeries compared to ORIF. ORIF is associated with a high rate of hardware removal and subsequent progressive post-traumatic arthritis requiring salvage arthrodesis.
Question 57:
A 35-year-old skier presents with pain and weakness in the right thumb after a fall. Examination demonstrates significant laxity of the ulnar collateral ligament (UCL) of the metacarpophalangeal joint. An MRI reveals a 'Stener lesion.' What is the exact anatomical arrangement that defines a Stener lesion?
Options:
- The torn proximal stump of the UCL is displaced superficial to the adductor pollicis aponeurosis.
- The torn distal stump of the UCL is trapped deep to the abductor pollicis brevis tendon.
- The UCL is avulsed with a bony fragment that is trapped within the joint space.
- The torn proximal stump of the UCL is displaced deep to the extensor pollicis longus tendon.
- The torn distal stump of the UCL is displaced superficial to the flexor pollicis longus tendon.
Correct Answer: The torn proximal stump of the UCL is displaced superficial to the adductor pollicis aponeurosis.
Explanation:
A Stener lesion occurs when the ulnar collateral ligament (UCL) of the thumb MCP joint tears (usually distal avulsion) and the torn proximal stump displaces superficially and becomes trapped outside of the adductor aponeurosis. Because the aponeurosis is interposed between the torn ends, conservative management fails and surgical repair is required.
Question 58:
Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is utilized in spine surgery to enhance arthrodesis. When used off-label in anterior cervical discectomy and fusion (ACDF), what is the most significant and potentially life-threatening complication associated with its use?
Options:
- High rates of recalcitrant pseudarthrosis
- Malignant transformation of surrounding soft tissues
- Severe prevertebral soft tissue swelling and airway compromise
- Dural erosion leading to high-flow cerebrospinal fluid leak
- Accelerated adjacent segment disease within 6 months
Correct Answer: Severe prevertebral soft tissue swelling and airway compromise
Explanation:
The use of rhBMP-2 in the anterior cervical spine has been associated with a massive, exaggerated inflammatory response leading to severe prevertebral soft tissue swelling, dysphagia, and potentially lethal airway compromise. Consequently, the FDA issued a warning regarding its use in the anterior cervical spine.
Question 59:
In the Ponseti method for the conservative treatment of idiopathic clubfoot, sequential correction of the specific deformity components is essential to avoid creating a rocker-bottom foot. Which of the following represents the correct order of deformity correction?
Options:
- Cavus, Adductus, Varus, Equinus
- Varus, Cavus, Equinus, Adductus
- Equinus, Varus, Adductus, Cavus
- Adductus, Varus, Cavus, Equinus
- Cavus, Varus, Adductus, Equinus
Correct Answer: Cavus, Adductus, Varus, Equinus
Explanation:
The Ponseti method dictates a specific sequence of correction remembered by the acronym CAVE: Cavus (corrected by elevating the first ray), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy). Correcting equinus before the midfoot is corrected can result in a rocker-bottom deformity.
Question 60:
According to the 2018 International Consensus Meeting (ICM) criteria for Periprosthetic Joint Infection (PJI), which of the following findings is considered a 'major' criterion, meaning it is diagnostic in itself of a PJI in a total knee arthroplasty?
Options:
- Elevated serum C-reactive protein (CRP) > 10 mg/L
- Synovial fluid white blood cell (WBC) count > 3,000 cells/µL
- Positive alpha-defensin test
- Two positive periprosthetic cultures with phenotypically identical organisms
- Elevated synovial fluid polymorphonuclear (PMN) percentage > 80%
Correct Answer: Two positive periprosthetic cultures with phenotypically identical organisms
Explanation:
According to the ICM criteria, there are two major criteria that definitively diagnose a PJI: 1) A sinus tract communicating with the joint, or 2) Two positive periprosthetic tissue/fluid cultures with phenotypically identical organisms. The other options are considered 'minor' criteria that contribute points toward the diagnostic scoring system but are not independently diagnostic.
