Full Question & Answer Text (for Search Engines)
Question 1:
A 25-year-old male sustains a high-energy Pauwels type III femoral neck fracture. In a young adult with this vertical fracture pattern, which of the following internal fixation constructs biomechanically offers the greatest resistance to vertical shear forces and varus collapse?
Options:
- Three parallel partially threaded cancellous screws
- Sliding hip screw with a supplemental derotational screw
- Dynamic condylar screw
- Cephalomedullary nail
- Three fully threaded cortical screws placed in a divergent pattern
Correct Answer: Sliding hip screw with a supplemental derotational screw
Explanation:
Pauwels type III femoral neck fractures have a vertical orientation (>50 degrees) and are subjected to high shear forces rather than compressive forces. Biomechanical studies have consistently demonstrated that a fixed-angle device, such as a sliding hip screw (SHS) with a supplemental derotational screw, provides superior stability against vertical shear and varus collapse compared to multiple cancellous screws in these specific high-angle fractures.
Question 2:
A 13-year-old obese male presents with acute-on-chronic hip and knee pain and an inability to bear weight on the affected limb. Radiographs confirm an unstable slipped capital femoral epiphysis (SCFE). He is taken to the operating room for urgent in-situ pinning. What is the most significant complication associated with attempting a forceful, intentional closed reduction of this deformity prior to hardware placement?
Options:
- Chondrolysis of the hip joint
- Femoral head osteonecrosis (avascular necrosis)
- Premature closure of the greater trochanteric apophysis
- Progression of the slip post-operatively
- Anterior labral tear
Correct Answer: Femoral head osteonecrosis (avascular necrosis)
Explanation:
An unstable SCFE (defined as the inability to bear weight even with crutches) already carries a high risk of osteonecrosis. Attempting a forceful closed reduction further disrupts the fragile retinacular vascular supply to the femoral epiphysis, significantly increasing the risk of iatrogenic avascular necrosis. Gentle reduction by positioning may occur naturally, but intentional forceful reduction is contraindicated.
Question 3:
A 22-year-old soccer player sustains a twisting injury to his knee during a match. Radiographs reveal a small elliptical bone fragment adjacent to the lateral tibial plateau (Segond fracture). Based on this radiographic finding, which physical exam maneuver is most likely to be positive in this patient?
Options:
- Positive dial test at 30 and 90 degrees
- Positive pivot shift test
- Increased posterior translation on posterior drawer testing
- Pain with varus stress testing at zero degrees
- Inability to actively extend the knee
Correct Answer: Positive pivot shift test
Explanation:
A Segond fracture is an avulsion fracture of the anterolateral ligament (ALL) and lateral capsule from the lateral tibial plateau. It is highly pathognomonic (up to 75-100% predictive value) for an anterior cruciate ligament (ACL) tear. The pivot shift test is the most specific physical examination finding for assessing rotational laxity associated with an ACL-deficient knee.
Question 4:
In the context of orthopedic implant design, utilizing a material with a Young's modulus (modulus of elasticity) that closely approximates that of human cortical bone primarily reduces the incidence of which of the following phenomena?
Options:
- Galvanic corrosion
- Fretting wear
- Stress shielding
- Third-body wear
- Macrophage-induced osteolysis
Correct Answer: Stress shielding
Explanation:
Stress shielding occurs when a stiff implant takes the majority of the mechanical load, depriving the surrounding bone of the stress required to maintain its mass (per Wolff's law), leading to bone resorption and potential implant loosening. Using a material with a Young's modulus closer to cortical bone (such as titanium alloy compared to stiffer cobalt-chromium) allows better load sharing with the bone, thereby reducing stress shielding.
Question 5:
A 32-year-old female presents with progressive knee pain. Imaging reveals an eccentric, lytic, epiphyseal lesion in the proximal tibia extending to the subchondral bone without a sclerotic margin. Biopsy confirms multinucleated giant cells intermixed with mononuclear stromal cells. If targeted medical therapy is initiated prior to surgical curettage, what is the primary mechanism of action of the preferred agent?
Options:
- Inhibition of the tyrosine kinase domain of VEGFR
- Monoclonal antibody binding to RANK ligand (RANKL)
- Inhibition of the mammalian target of rapamycin (mTOR)
- Binding to the intracellular domain of the HER2 receptor
- Direct alkylation of DNA causing cross-linking
Correct Answer: Monoclonal antibody binding to RANK ligand (RANKL)
Explanation:
The clinical and radiographic presentation is classic for a Giant Cell Tumor (GCT) of bone. Denosumab is a monoclonal antibody frequently used as neoadjuvant or primary medical therapy for aggressive or unresectable GCTs. It binds specifically to RANKL, preventing it from interacting with RANK receptors on osteoclast precursors and the giant cells themselves, thereby profoundly inhibiting osteoclastogenesis and tumor-associated bone destruction.
Question 6:
A 65-year-old man presents with deteriorating handwriting, difficulty buttoning his shirt, and gait instability. Exam reveals hyperreflexia in the lower extremities and a positive "Finger Escape Sign." What does this specific physical examination finding indicate?
Options:
- Inability to maintain the ulnar digits in extension and adduction due to intrinsic weakness from cervical myelopathy
- Electric shock sensation radiating down the spine upon active neck flexion
- Hyperextension of the thumb interphalangeal joint during a pinch maneuver
- Numbness in the little finger during sustained wrist flexion
- Weakness of the flexor digitorum profundus to the index finger causing the "OK" sign to collapse
Correct Answer: Inability to maintain the ulnar digits in extension and adduction due to intrinsic weakness from cervical myelopathy
Explanation:
The Finger Escape Sign is a clinical manifestation of cervical spondylotic myelopathy. When the patient is asked to hold their fingers in active extension and adduction, the little and ring fingers spontaneously drift into abduction and flexion within 30 to 60 seconds due to intrinsic muscle weakness and loss of upper motor neuron control.
Question 7:
A 24-year-old football player sustains a midfoot injury after an axial load to a plantarflexed foot. Weight-bearing radiographs reveal a 3 mm diastasis between the base of the first and second metatarsals. Where does the primary interosseous Lisfranc ligament normally originate and insert?
Options:
- Medial cuneiform to the base of the first metatarsal
- Lateral aspect of the medial cuneiform to the medial base of the second metatarsal
- Middle cuneiform to the base of the second metatarsal
- Lateral cuneiform to the base of the third metatarsal
- Navicular to the medial cuneiform
Correct Answer: Lateral aspect of the medial cuneiform to the medial base of the second metatarsal
Explanation:
The Lisfranc ligament is the critical interosseous ligament providing stability to the tarsometatarsal joint complex. It runs obliquely from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. Rupture of this ligament leads to diastasis between the first and second metatarsal bases (the 'fleck sign' is an avulsion of this ligament).
Question 8:
In modern total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced the incidence of wear-related osteolysis compared to traditional ultra-high-molecular-weight polyethylene (UHMWPE). Which of the following manufacturing processes is primarily responsible for generating the cross-links that increase the wear resistance of HXLPE?
Options:
- High-dose gamma or electron beam irradiation
- Sterilization with ethylene oxide gas
- Addition of Vitamin E prior to consolidation
- Calcium phosphate surface coating
- Cold working the polyethylene sheet under high pressure
Correct Answer: High-dose gamma or electron beam irradiation
Explanation:
Highly cross-linked polyethylene (HXLPE) is created by subjecting standard UHMWPE to high doses of gamma or electron beam irradiation (typically 50-100 kGy). The irradiation cleaves polymer chains, creating free radicals that subsequently bond to form a dense network of cross-links, vastly improving wear resistance. This is typically followed by a thermal treatment (annealing or remelting) to extinguish residual free radicals and prevent long-term oxidation.
Question 9:
A surgeon utilizes a non-vascularized cancellous autograft to augment fixation of a tibial nonunion. Which of the following best describes the primary biological process by which this specific graft incorporates into the host bone?
Options:
- Osteoinduction driven exclusively by exogenous bone morphogenetic proteins
- Endochondral ossification mediated by hypertrophic chondrocytes
- Creeping substitution where host osteoclasts resorb graft trabeculae while osteoblasts lay down new woven bone
- Intramembranous ossification originating entirely from the overlying muscle fascia
- Angiogenesis followed by the direct metabolic revival of all donor graft osteocytes
Correct Answer: Creeping substitution where host osteoclasts resorb graft trabeculae while osteoblasts lay down new woven bone
Explanation:
Cancellous autografts incorporate primarily via a process called 'creeping substitution.' The graft acts as an osteoconductive scaffold. Over time, host-derived osteoclasts slowly resorb the dead graft trabeculae, while host-derived osteoblasts follow closely behind to deposit new woven (and eventually lamellar) bone onto the scaffold.
Question 10:
A 45-year-old male sustains a high-energy Schatzker IV tibial plateau fracture. Given the classic displacement pattern of this specific injury, which of the following is the most appropriate surgical approach and fixation strategy to properly neutralize the deforming forces?
Options:
- Anterolateral approach with a single lateral locking plate
- Posteromedial approach with a medial buttress (anti-glide) plate
- Direct midline anterior approach with dual locking plates
- Anterolateral approach with an anterior buttress plate
- Arthroscopic-assisted percutaneous lateral screw fixation
Correct Answer: Posteromedial approach with a medial buttress (anti-glide) plate
Explanation:
A Schatzker IV fracture involves the medial tibial plateau and is typically the result of high-energy varus forces, often combined with an axial load. The primary deforming force drives the medial fragment into varus and posterior subluxation. The biomechanically sound treatment requires a posteromedial approach with a medial buttress (or anti-glide) plate to physically resist the varus and posterior displacement.
Question 11:
A 4-month-old infant with developmental dysplasia of the hip (DDH) has been treated with a Pavlik harness for exactly 4 weeks. Serial ultrasounds show the left hip remains persistently dislocated and irreducible in the harness. What is the most appropriate next step in the management of this patient?
Options:
- Continue the Pavlik harness for an additional 4 weeks to allow further remodeling
- Transition immediately to a rigid hip abduction orthosis (e.g., Ilfeld splint)
- Discontinue the harness and proceed with closed reduction and spica casting under general anesthesia
- Open reduction via an anterior approach with a Salter pelvic osteotomy
- Varus derotational osteotomy of the proximal femur
Correct Answer: Discontinue the harness and proceed with closed reduction and spica casting under general anesthesia
Explanation:
If a hip remains dislocated after 3 to 4 weeks of strict Pavlik harness use, it is deemed a failure of the harness. The harness must be discontinued immediately to prevent 'Pavlik harness disease' (erosion of the posterior acetabular wall and increased risk of avascular necrosis). The standard next step is an exam under anesthesia, arthrogram, and closed reduction with spica casting.
Question 12:
A 30-year-old carpenter sustains a sharp laceration over the dorsal aspect of his proximal interphalangeal (PIP) joint, completely severing the central slip of the extensor mechanism. If this injury is misdiagnosed and left untreated, what classic finger deformity will predictably develop over the ensuing weeks?
Options:
- Swan neck deformity
- Boutonniere deformity
- Mallet finger
- Pseudo-boutonniere deformity
- Intrinsic plus hand
Correct Answer: Boutonniere deformity
Explanation:
Disruption of the central slip at the PIP joint initially results in a subtle extension lag. Over time, the lateral bands subluxate volarly. Once the lateral bands fall volar to the axis of rotation of the PIP joint, they act as flexors of the PIP joint and hyperextensors of the DIP joint, creating the classic Boutonniere deformity.
Question 13:
A 68-year-old male presents with severe, chronic shoulder pain and pseudoparalysis of active elevation. MRI reveals a massive, retracted tear of the supraspinatus and infraspinatus tendons with severe fatty infiltration (Goutallier stage 4) and superior migration of the humeral head. He has an intact, functioning deltoid muscle. Which surgical intervention provides the most reliable restoration of active elevation and pain relief?
Options:
- Arthroscopic primary rotator cuff repair with margin convergence
- Latissimus dorsi tendon transfer
- Reverse total shoulder arthroplasty (RTSA)
- Anatomic total shoulder arthroplasty (TSA)
- Superior capsular reconstruction (SCR)
Correct Answer: Reverse total shoulder arthroplasty (RTSA)
Explanation:
In an older patient with an irreparable massive rotator cuff tear, pseudoparalysis, and severe fatty atrophy (Goutallier 3 or 4), a reverse total shoulder arthroplasty (RTSA) is the gold standard treatment. RTSA relies on the deltoid muscle to restore arm elevation by medializing and distalizing the center of rotation, effectively bypassing the deficient rotator cuff. Anatomic TSA is contraindicated due to the 'rocking horse' phenomenon, which leads to early glenoid component loosening in cuff-deficient shoulders.
Question 14:
A 72-year-old female presents with bilateral leg and buttock pain that worsens predictably with walking and standing, but improves rapidly when she leans forward over a shopping cart. She has normal palpable peripheral pulses. On advanced imaging, an absolute measurement below what threshold for the anteroposterior (AP) dimension of the lumbar spinal canal is classically diagnostic of absolute spinal stenosis?
Options:
- 10 mm
- 14 mm
- 18 mm
- 22 mm
- 26 mm
Correct Answer: 10 mm
Explanation:
The patient's clinical history is classic for neurogenic claudication secondary to lumbar spinal stenosis. While relative stenosis is typically defined as an AP canal diameter of less than 12 mm, absolute spinal stenosis is defined as an AP canal diameter of less than 10 mm on a mid-sagittal MRI or CT scan.
Question 15:
A 14-year-old boy presents with a painful mass in his distal femur. Radiographs display a "sunburst" periosteal reaction and Codman's triangle. Core needle biopsy confirms high-grade intramedullary osteosarcoma. Following a standard protocol of multi-agent neoadjuvant chemotherapy and wide surgical resection, what is the single most important prognostic factor for this patient's long-term survival?
Options:
- Initial tumor volume exceeding 200 cubic centimeters
- The specific histologic subtype of the tumor (e.g., chondroblastic vs. telangiectatic)
- The percentage of tumor necrosis observed in the resected specimen
- Presence of a t(11;22) chromosomal translocation
- Patient age at the time of diagnosis
Correct Answer: The percentage of tumor necrosis observed in the resected specimen
Explanation:
In patients with localized, high-grade osteosarcoma, the histologic response to neoadjuvant chemotherapy is the single most reliable prognostic factor for long-term survival. A 'good responder' is typically defined as having greater than 90% tumor necrosis in the final resected specimen, which correlates with significantly higher overall survival rates.
Question 16:
A 28-year-old male is admitted after a motorcycle accident with a closed, comminuted midshaft tibial fracture. Four hours post-injury, he develops severe, escalating leg pain out of proportion to his injury and pain with passive stretch of his great toe. Intracompartmental pressure monitoring is performed. What is the most widely accepted objective pressure criterion indicating the need for an emergent four-compartment fasciotomy?
Options:
- Absolute anterior compartment pressure > 20 mmHg
- Absolute anterior compartment pressure > 25 mmHg
- Delta pressure (Diastolic blood pressure minus compartment pressure) < 30 mmHg
- Delta pressure (Mean arterial pressure minus compartment pressure) < 45 mmHg
- Delta pressure (Systolic blood pressure minus compartment pressure) < 50 mmHg
Correct Answer: Delta pressure (Diastolic blood pressure minus compartment pressure) < 30 mmHg
Explanation:
Acute compartment syndrome is a surgical emergency. The most reliable objective measure is the delta pressure, calculated as the patient's diastolic blood pressure minus the measured intracompartmental pressure. A delta pressure of less than 30 mmHg (meaning the compartment pressure is approaching the diastolic pressure) is an absolute indication for emergent fasciotomy to prevent irreversible muscle and nerve necrosis.
Question 17:
Articular cartilage is structurally divided into four distinct zones, each with unique biomechanical properties. Which zone contains the highest concentration of collagen, with fibrils oriented strictly parallel to the joint surface to maximally resist shear forces?
Options:
- Superficial (tangential) zone
- Middle (transitional) zone
- Deep (radial) zone
- Calcified cartilage zone
- Tidemark
Correct Answer: Superficial (tangential) zone
Explanation:
The superficial (tangential) zone of articular cartilage makes up the top 10-20% of the cartilage thickness. It contains the highest concentration of collagen (primarily Type II) and the lowest concentration of proteoglycans. The collagen fibrils in this zone are tightly packed and aligned parallel to the articular surface, which provides the cartilage with its high tensile strength and ability to resist shear forces during joint articulation.
Question 18:
A 45-year-old female pedestrian is struck by a bus and presents hemodynamically unstable in the trauma bay. A pelvic radiograph shows a severely displaced anterior-posterior compression (APC-III) pelvic ring injury with a widened pubic symphysis. A pelvic binder is immediately applied to reduce pelvic volume. To maximize biomechanical efficacy and achieve optimal reduction of the symphysis, the binder should be centered exactly over which anatomic landmark?
Options:
- The iliac crests
- The anterior superior iliac spines (ASIS)
- The greater trochanters
- The pubic symphysis
- The umbilicus
Correct Answer: The greater trochanters
Explanation:
In the emergent management of open-book pelvic fractures (APC injuries), a pelvic binder or sheet must be centered directly over the greater trochanters of the femur. This placement efficiently translates compressive forces across the pelvic ring, closing the pubic symphysis and reducing pelvic volume to help tamponade venous and cancellous bone bleeding. Placing the binder too high (over the iliac crests) can paradoxically widen the pelvic outlet or fail to compress the true pelvis.
Question 19:
A 65-year-old female is 6 months status post a posterior-stabilized total knee arthroplasty (TKA). She presents complaining of a painful "catching" or "popping" sensation at the anterior aspect of her knee specifically when she actively extends her knee from a flexed position. What is the most likely etiology of this complication?
Options:
- Patellar maltracking due to internal rotation of the tibial component
- Fibrous nodule formation at the posterior aspect of the quadriceps tendon just proximal to the superior pole of the patella
- Aseptic loosening of the femoral component
- Accelerated polyethylene wear of the articular tibial insert
- Popliteus tendon impingement on the lateral femoral condyle
Correct Answer: Fibrous nodule formation at the posterior aspect of the quadriceps tendon just proximal to the superior pole of the patella
Explanation:
This presentation is classic for 'patellar clunk syndrome,' a complication most frequently associated with posterior-stabilized TKA designs. It is caused by the formation of a fibrous or fibrosynovial nodule on the posterior aspect of the quadriceps tendon just above the superior pole of the patella. During flexion, the nodule drops into the intercondylar box of the femoral component. As the knee extends, it gets trapped and then suddenly 'clunks' out, causing a painful catching sensation.
Question 20:
A 6-year-old child sustains a completely displaced Gartland Type III extension-type supracondylar humerus fracture. The anterior interosseous nerve (AIN) is anatomically at the highest risk for injury in this specific fracture pattern. Which of the following physical exam findings definitively confirms an isolated AIN palsy?
Options:
- Inability to forcefully abduct the fingers
- Numbness over the dorsal aspect of the first web space
- Inability to flex the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger
- Inability to actively extend the wrist and metacarpophalangeal joints
- Loss of two-point discrimination on the volar aspect of the little finger
Correct Answer: Inability to flex the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger
Explanation:
The anterior interosseous nerve (AIN) is a purely motor branch of the median nerve that is frequently stretched or tethered over the proximal fracture fragment in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index (and sometimes middle) finger, and the pronator quadratus. An isolated AIN palsy manifests as the inability to form an 'OK' sign, presenting as a 'pinch' posture with the thumb IP and index DIP joints extended.
