Orthopedic Review | Dr Hutaif General Orthopedics Revie -...

Question 1

According to Perren's strain theory, what type of bone healing occurs in a fracture environment with absolute stability (strain less than 2%) and no gap?

Explanation

Under conditions of absolute stability (strain < 2%) and anatomic reduction, primary bone healing occurs. This process is mediated by osteoclastic cutting cones crossing the fracture site, followed by osteoblastic bone deposition, without the formation of an intermediate fracture callus.

Question 2

A 14-year-old boy presents with a painful diaphyseal femur lesion. Radiographs demonstrate an ill-defined destructive lesion with 'onion-skin' periosteal reaction. A biopsy is performed. Which of the following is the most common cytogenetic translocation and resulting fusion protein associated with this diagnosis?

Explanation

The clinical presentation and radiographic findings are classic for Ewing sarcoma. Approximately 85% of Ewing sarcomas are characterized by the t(11;22)(q24;q12) translocation, which fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11, acting as an aberrant transcription factor.

Question 3

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 parents note she has stopped kicking her leg on the affected side. On exam, she has an absent patellar reflex and cannot actively extend the knee. Which of the following positioning errors most likely caused this complication?

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive hip flexion (hyperflexion), which compresses the femoral nerve against the inguinal ligament. It presents as an inability to actively extend the knee. Excessive abduction is associated with avascular necrosis of the femoral head.

Question 4

A 35-year-old male is brought to the trauma bay following a high-speed motorcycle collision. Pelvic radiographs show an Anterior Posterior Compression Type III (APC-III) pelvic ring injury. He remains hypotensive despite initial resuscitation, and a pelvic binder is applied. What is the most common anatomical source of massive hemorrhage in this fracture pattern?

Explanation

In severe pelvic ring disruptions, particularly open-book (APC) types, 80-90% of bleeding is of venous origin. The presacral venous plexus and prevesical veins are the most common sources. Arterial bleeding (e.g., superior gluteal, internal pudendal) accounts for only 10-20% of cases and is more common in lateral compression or severe vertical shear injuries.

Question 5

During a primary total knee arthroplasty (TKA), the surgeon places the trial components. The evaluation reveals a symmetric tight extension gap and a symmetric, well-balanced flexion gap. Which of the following is the most appropriate surgical step to correct this mismatch?

Explanation

In gap balancing for TKA, a tight extension gap with a normal flexion gap indicates that the distal femur is 'too long' (under-resected). The correct intervention is to resect additional distal femur. Resecting additional tibia would loosen both the extension and flexion gaps.

Question 6

A 22-year-old soccer player undergoes an anterior cruciate ligament (ACL) reconstruction. The surgeon debates between a Bone-Patellar Tendon-Bone (BPTB) autograft and a quadrupled hamstring autograft. Regarding the biomechanical properties at 'time zero' (implantation), which of the following statements is true?

Explanation

At time zero, a quadrupled hamstring graft has the highest ultimate tensile load (approx. 4000 N), which is higher than both the native ACL (approx. 2160 N) and the central third BPTB graft (approx. 2977 N). However, clinical stability also depends heavily on graft fixation and biologic incorporation over time.

Question 7

In patients with cervical spondylotic myelopathy (CSM), direct compression and subsequent ischemia contribute to progressive spinal cord dysfunction. Which vascular structure is most susceptible to direct compression from anterior disc osteophyte complexes, leading to ischemia of the lateral corticospinal tracts?

Explanation

The anterior spinal artery supplies the anterior two-thirds of the spinal cord, including the lateral corticospinal tracts and anterior horn cells. In CSM, anterior compression from disc osteophyte complexes directly impinges upon this artery, causing focal ischemia that contributes heavily to myelopathic symptoms.

Question 8

A 35-year-old manual laborer presents with a swollen, painful index finger three days after a puncture wound to the volar aspect of the digit. The physician evaluates for pyogenic flexor tenosynovitis. Which of Kanavel's four cardinal signs is generally considered the most reliable, earliest to appear, and last to resolve?

Explanation

Kanavel's four cardinal signs for flexor tenosynovitis are fusiform (sausage-like) swelling, the digit resting in a flexed posture, tenderness along the flexor tendon sheath, and severe pain with passive extension. Pain on passive extension is widely regarded as the most sensitive and earliest sign to appear.

Question 9

A 24-year-old gymnast lands awkwardly and sustains an acute midfoot injury. Radiographs show a 'fleck sign' in the first intermetatarsal space. This indicates an avulsion of the Lisfranc ligament. What is the precise anatomical origin and insertion of the intact Lisfranc ligament?

Explanation

The Lisfranc ligament is an interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the largest and most critical ligament stabilizing the tarsometatarsal joint complex. The 'fleck sign' represents an avulsion fracture at its attachment.

Question 10

A 6-year-old child presents with multiple unexplained fractures and severe anemia. Radiographs display symmetrically thickened, hyperdense bones ('marble bone') with an absence of normal medullary cavities. The pathogenesis of this condition (osteopetrosis) most commonly involves a defect in Carbonic Anhydrase II. This primarily disrupts which cellular process?

Explanation

Osteopetrosis is caused by defective osteoclast function, specifically the inability to acidify Howship's lacuna at the ruffled border. Mutations in Carbonic Anhydrase II (CAII) or the TCIRG1 gene prevent the necessary generation and transport of protons (H+) to dissolve bone mineral, leading to dense, brittle bones and obliterated marrow spaces.

Question 11

A surgeon utilizes the Smith-Petersen (anterior) approach for an open reduction of a developmental hip dysplasia. The superficial internervous plane lies between the sartorius and the tensor fasciae latae (TFL). What muscles define the deep internervous plane of this approach?

Explanation

The Smith-Petersen (anterior) approach uses a true internervous plane superficially between the sartorius (femoral nerve) and TFL (superior gluteal nerve), and deeply between the rectus femoris (femoral nerve) and gluteus minimus (superior gluteal nerve).

Question 12

A 13-year-old obese male undergoes in-situ percutaneous pinning for a stable Slipped Capital Femoral Epiphysis (SCFE). Over the next 5 years, he develops progressively worsening anterior hip pain and a decrease in hip internal rotation. What is the most common long-term mechanical complication of an unreduced SCFE pinned in-situ?

Explanation

In-situ pinning of a SCFE arrests slip progression but leaves a residual proximal femoral deformity (the metaphysis remains prominent anteriorly and superiorly). This abnormal morphology frequently results in cam-type femoroacetabular impingement (FAI), causing labral damage and early-onset hip osteoarthritis.

Question 13

A 25-year-old male is admitted with a comminuted tibia fracture. He complains of excruciating leg pain out of proportion to the injury. His blood pressure is 115/70 mmHg, and his Mean Arterial Pressure (MAP) is 85 mmHg. Intracompartmental pressure monitoring is performed. The anterior compartment pressure is 45 mmHg. Which of the following formulas represents the most widely accepted threshold (Delta P) for diagnosing acute compartment syndrome requiring fasciotomy?

Explanation

The most widely accepted and specific criterion for diagnosing acute compartment syndrome is a Delta P (Diastolic Blood Pressure minus the highest compartment pressure) of less than 30 mmHg. Relying solely on absolute pressures often leads to overdiagnosis and unnecessary fasciotomies, particularly in hypertensive patients.

Question 14

During a total hip arthroplasty, the surgeon opts to use a high-offset femoral stem to lateralize the greater trochanter. According to standard hip biomechanics, how does this modification primarily affect the abductor mechanism and the joint reaction force?

Explanation

Increasing the femoral offset lateralizes the greater trochanter, which increases the abductor moment arm. With a longer lever arm, the abductor muscles must generate less force to balance the pelvis during single-leg stance. Consequently, the overall joint reaction force across the hip is decreased, reducing wear on the bearing surfaces.

Question 15

A patient with a laceration at the wrist presents with severe clawing of the ring and small fingers. Interestingly, a patient with a laceration of the same nerve near the medial epicondyle at the elbow presents with a much less pronounced claw deformity. What is the anatomical basis for this 'ulnar paradox' in the higher injury?

Explanation

The 'ulnar paradox' states that a high ulnar nerve injury produces a less severe claw deformity than a low ulnar nerve injury. This is because in a high injury, the ulnar half of the Flexor Digitorum Profundus (FDP) is denervated, eliminating the unopposed flexion of the DIP joints of the 4th and 5th digits that exacerbates clawing when the interossei and lumbricals are paralyzed.

Question 16

A 24-year-old collegiate baseball pitcher complains of anterior shoulder pain and a 'dead arm' sensation. MRI arthrogram demonstrates a Type II SLAP (Superior Labrum Anterior Posterior) lesion. Based on Snyder's classification, which of the following accurately describes a Type II SLAP lesion?

Explanation

In Snyder's classification of SLAP tears: Type I is degenerative fraying. Type II involves detachment of the superior labrum and the biceps anchor from the superior glenoid (the most common type requiring repair in young athletes). Type III is a bucket-handle tear with an intact anchor. Type IV is a bucket-handle tear that extends into the biceps tendon.

Question 17

Articular cartilage is a highly specialized tissue divided into four distinct zones. Which zone is characterized by having the highest concentration of water, the lowest concentration of proteoglycans, and collagen fibers oriented parallel to the articular surface?

Explanation

The superficial (tangential) zone comprises 10-20% of articular cartilage thickness. It has the highest water content (up to 80%), the lowest proteoglycan content, and densely packed collagen type II fibers aligned parallel to the joint surface to resist shear and tensile stresses.

Question 18

A 16-year-old male complains of severe, aching leg pain that awakens him at night but is reliably completely relieved by ibuprofen. Radiographs reveal a thickened anterior tibial cortex surrounding a 5-mm radiolucent nidus. If this nidus were excised and examined histologically, what would be the classic finding?

Explanation

The clinical presentation is classic for an osteoid osteoma, which secretes high levels of prostaglandins (relieved by NSAIDs). Histologically, the nidus consists of interlacing trabeculae of osteoid and woven bone lined by benign, prominent osteoblasts in a loose, highly vascularized connective tissue stroma.

Question 19

An 80-year-old female sustains an un-displaced, transcervical femoral neck fracture. Despite non-operative or pinning treatment, she remains at significant risk for avascular necrosis (AVN) of the femoral head. Disruption of which primary blood vessel is the most significant cause of AVN in this injury?

Explanation

The primary blood supply to the adult femoral head is the deep branch of the medial femoral circumflex artery (MFCA), which gives rise to the lateral epiphyseal vessels. These vessels run along the superior-posterior aspect of the femoral neck and are highly susceptible to disruption or kinking in femoral neck fractures.

Question 20

During a percutaneous or minimally invasive repair of an acute Achilles tendon rupture, the sural nerve is at significant risk of iatrogenic entrapment. At approximately what distance proximal to the superior calcaneal tuberosity does the sural nerve typically cross the lateral border of the Achilles tendon?

Explanation

Anatomical studies show that the sural nerve crosses the lateral border of the Achilles tendon approximately 9.8 cm (roughly 10 cm) proximal to its calcaneal insertion. Sutures placed percutaneously or blindly into the lateral paratenon in this specific zone carry a high risk of tethering or directly injuring the nerve.

Question 21

A 35-year-old male undergoes a structural allograft reconstruction following tumor resection. Which of the following best describes the incorporation process of a massive cortical bone allograft compared to a cancellous bone autograft?

Explanation

Cortical bone grafts incorporate via creeping substitution, which is initiated by osteoclastic resorption of the existing Haversian canals. This leads to a temporary decrease in the mechanical strength of the graft before osteoblastic new bone formation occurs. In contrast, cancellous autografts incorporate via early osteoblastic apposition on the trabeculae, initially increasing in strength.

Question 22

A 30-year-old female presents with a deep, painless mass in the plantar aspect of her foot. Biopsy reveals a malignant proliferation of cells, and cytogenetic analysis demonstrates a t(12;22)(q13;q12) chromosomal translocation. Which of the following fusion genes is most likely associated with this lesion?

Explanation

Clear cell sarcoma (melanoma of soft parts) is classically characterized by the t(12;22)(q13;q12) translocation, resulting in the EWS-ATF1 fusion gene. EWS-FLI1 is associated with Ewing sarcoma t(11;22); SYT-SSX1 with synovial sarcoma t(X;18); PAX3-FKHR with alveolar rhabdomyosarcoma t(2;13); and TLS-CHOP with myxoid liposarcoma t(12;16).

Question 23

In a polytraumatized patient with severe bilateral lower extremity open fractures, closed head injury, and pulmonary contusions, the decision to proceed with damage control orthopedics (DCO) rather than early total care (ETC) is often guided by the systemic inflammatory state. Which of the following serum markers peaks early (within 12-24 hours) and is most predictive of the development of multiple organ dysfunction syndrome (MODS)?

Explanation

IL-6 is a highly potent pro-inflammatory cytokine that peaks around 12-24 hours post-injury. Elevated IL-6 levels correlate strongly with the severity of tissue injury, the magnitude of the physiological 'second hit' from surgery, and the risk of developing MODS and ARDS in polytrauma patients.

Question 24

A 24-year-old male sustains a burst fracture of C5. On examination, he has no voluntary motor function below the C5 level. However, he has preserved pinprick and light touch sensation in the S4-S5 dermatomes, as well as deep anal pressure. What is his ASIA Impairment Scale (AIS) grade?

Explanation

ASIA B describes a sensory incomplete spinal cord injury where sensory function (but not motor function) is preserved below the neurological level and must include the sacral segments S4-S5. ASIA A is a complete injury. ASIA C and D are motor incomplete injuries differentiated by muscle strength.

Question 25

A 12-year-old boy presents with a unilateral slipped capital femoral epiphysis (SCFE) of the left hip. He is scheduled for in situ screw fixation. Which of the following factors is the strongest indication for prophylactic pinning of the contralateral, asymptomatic hip?

Explanation

Patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) have a significantly higher risk of developing bilateral SCFE, approaching 100% in some series. Prophylactic pinning of the contralateral hip is highly recommended in these cases.

Question 26

When calculating the 'glenoid track' to evaluate a patient with recurrent anterior shoulder instability and an engaging Hill-Sachs lesion, which of the following formulas is used to determine the width of the glenoid track?

Explanation

The glenoid track width is calculated as 83% of the inferior true intact glenoid width minus the width of the anterior glenoid bone defect. If the Hill-Sachs Interval (HSI) is greater than the glenoid track width, the lesion is considered 'off-track' and is at high risk of engaging over the anterior glenoid rim.

Question 27

A 65-year-old male presents with severe groin pain 5 years after undergoing a total hip arthroplasty with a large-diameter metal-on-polyethylene bearing. Aspiration is negative for infection. Serum cobalt levels are significantly elevated, while chromium levels are normal. MRI reveals a large solid pseudotumor. Which of the following is the most likely source of the elevated metal ions?

Explanation

Elevated serum cobalt levels with normal or only mildly elevated chromium levels in the setting of a metal head on a polyethylene liner indicate mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck taper junction. Unlike metal-on-metal bearings where both Co and Cr are elevated, trunnionosis typically presents with a disproportionately high Co/Cr ratio.

Question 28

During the early stages of flexor tendon healing in Zone II of the hand, the tendon utilizes both intrinsic and extrinsic mechanisms for repair. Which of the following is the primary clinical disadvantage of healing that relies predominantly on extrinsic mechanisms?

Explanation

Extrinsic tendon healing relies on cellular infiltration and capillary ingrowth from the surrounding sheath and tissues. While it provides rapid biological healing, its primary disadvantage is the formation of dense peritendinous adhesions that restrict tendon excursion and normal gliding. Intrinsic healing is preferred to optimize functional outcomes.

Question 29

Which of the following descriptions accurately characterizes the metabolic and physiologic profile of Type I (slow-twitch) skeletal muscle fibers compared to Type II (fast-twitch) fibers?

Explanation

Type I muscle fibers (slow-twitch) are oxidative fibers. They have a high mitochondrial density, high myoglobin content (giving them a red appearance), and high oxidative capacity, making them highly resistant to fatigue and ideal for sustained posture and endurance. Type II fibers are fast-twitch, highly glycolytic, fatigue easily, and appear pale.

Question 30

A 55-year-old diabetic male presents with a swollen, erythematous, and warm foot. Radiographs reveal prominent periarticular fragmentation, subluxation of the tarsometatarsal joints, and bony debris. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent, and what is the hallmark radiographic finding of the subsequent stage?

Explanation

The patient is in Eichenholtz Stage 1 (Development/Fragmentation), characterized clinically by acute inflammation and radiographically by periarticular fragmentation, debris, and subluxation. The subsequent stage is Stage 2 (Coalescence), where the hallmark is the absorption of fine debris, early fusion of larger fragments, and sclerosis.

Question 31

An orthopedic surgeon performing an ilioinguinal approach for open reduction of an anterior column acetabular fracture encounters brisk arterial bleeding while dissecting over the superior pubic ramus. This bleeding is most likely originating from the 'corona mortis', which is an anastomosis between which two vascular territories?

Explanation

The 'corona mortis' (crown of death) is a highly variable vascular anastomosis between the external iliac system (inferior epigastric artery/vein) and the internal iliac system (obturator artery/vein). It crosses over the superior pubic ramus and is highly susceptible to injury during anterior approaches to the pelvis and acetabulum.

Question 32

A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. According to the Herring Lateral Pillar Classification, which of the following radiographic criteria places the hip in Group B?

Explanation

In the Herring Lateral Pillar Classification for Perthes disease: Group A has no involvement of the lateral pillar. Group B has >50% maintenance of lateral pillar height. Group C has <50% maintenance of lateral pillar height. The classification strongly correlates with long-term sphericity of the femoral head.

Question 33

A 50-year-old male undergoes wide resection of a proximal femur lesion. Pathology describes a cartilaginous tumor with abundant myxoid stroma, high cellularity, marked nuclear atypia, and prominent mitotic figures. Which grade of chondrosarcoma does this best represent, and what is its expected metastatic potential?

Explanation

The presence of abundant myxoid stroma, high cellularity, marked nuclear atypia, and prominent mitotic figures points to a Grade 3 chondrosarcoma. Unlike low-grade (Grade 1) chondrosarcomas which rarely metastasize, Grade 3 tumors have a very high metastatic potential (up to 70%) and a significantly lower overall survival rate.

Question 34

A 68-year-old male with pre-existing cervical spondylosis presents after a hyperextension injury. He exhibits significant weakness in his bilateral hands and arms, with relative sparing of his lower extremities. Sensation is variably diminished. This clinical presentation is best explained by injury to which aspect of the spinal cord?

Explanation

This is Central Cord Syndrome, the most common incomplete spinal cord injury pattern. It typically occurs in older patients with spondylosis who suffer a hyperextension injury. Damage to the central grey matter and the medial aspect of the corticospinal tracts (which carry cervical motor fibers) leads to upper extremity weakness being far greater than lower extremity weakness.

Question 35

During the single-leg stance phase of gait, the hip abductor muscles must generate significant force to maintain a level pelvis. Based on standard free-body diagram principles of the hip, if the body's center of gravity is displaced further laterally away from the center of rotation of the hip joint, what is the effect on the required abductor force and the overall hip joint reaction force?

Explanation

The hip acts as a class 1 lever. The moment arm of body weight is counterbalanced by the moment arm of the abductor muscles. If the center of gravity moves further away from the hip (increasing the body weight moment arm), the abductors must generate more force to maintain equilibrium. This increased abductor muscle force, combined with the body weight, results in a substantially increased overall joint reaction force.

Question 36

According to Perren's strain theory of fracture healing, which type of tissue can tolerate the highest amount of interfragmentary strain before failing, thereby acting as the necessary initial bridging tissue in secondary bone healing?

Explanation

Granulation tissue can tolerate up to 100% strain before failing. Fibrous tissue tolerates ~17%, cartilage ~2-10%, and lamellar bone only 2%. Therefore, in the high-strain environment immediately following a fracture, only granulation tissue can form. As the callus builds, stiffness increases, strain decreases, and subsequent tissue types can form.

Question 37

Low-molecular-weight heparin (LMWH) is frequently used for venous thromboembolism prophylaxis. What is its primary mechanism of action compared to unfractionated heparin?

Explanation

LMWH complexes with antithrombin III, primarily inhibiting Factor Xa, with a much lower affinity for inhibiting thrombin (Factor IIa) compared to unfractionated heparin. This selective anti-Xa activity provides a more predictable anticoagulant dose-response and a lower risk of Heparin-Induced Thrombocytopenia (HIT).

Question 38

A 42-year-old mechanic presents with vague volar forearm pain and an inability to make an 'OK' sign with his thumb and index finger. Sensation in his hand is completely normal. Which of the following muscles is most likely paralyzed in this patient?

Explanation

The patient has Anterior Interosseous Nerve (AIN) syndrome. The AIN is a pure motor branch of the median nerve innervating the Flexor Pollicis Longus (FPL), the radial half of the Flexor Digitorum Profundus (FDP), and the Pronator Quadratus. Paralysis of the FPL and FDP prevents flexion of the thumb IP joint and index DIP joint, preventing a proper 'OK' sign.

Question 39

Following an ACL reconstruction using a bone-patellar tendon-bone autograft, the graft undergoes 'ligamentization'. During which post-operative time frame is the graft biomechanically at its weakest due to ongoing revascularization and cellular repopulation?

Explanation

The ligamentization process includes initial necrosis, revascularization/cellular repopulation (remodeling), and maturation. Biomechanically, the graft is at its weakest during the early remodeling phase, typically around 6 to 12 weeks post-operatively, making it highly susceptible to rupture if exposed to excessive stress or premature return to sport.

Question 40

A 28-year-old male sustains a high-energy dorsiflexion injury. Radiographs show a displaced fracture of the talar neck with subluxation of the subtalar joint, but the tibiotalar and talonavicular joints remain concentrically reduced. According to the Hawkins classification, what is the approximate risk of developing avascular necrosis (AVN) of the talar body?

Explanation

This describes a Hawkins Type II fracture (talar neck fracture with subtalar subluxation/dislocation). The risk of AVN for Type II fractures is historically cited as 20% to 50%. Type I (nondisplaced) carries a 0-10% risk. Type III (subtalar and tibiotalar dislocation) and Type IV (Type III plus talonavicular dislocation) carry a very high risk of AVN, approaching 70-100%.

Question 41

In normal articular cartilage, which zone is characterized by chondrocytes flattened parallel to the joint surface and primarily functions to resist shear forces?

Explanation

The superficial (tangential) zone contains flattened chondrocytes and collagen fibrils oriented parallel to the joint surface. It is specifically adapted to resist shear stresses and has the highest concentration of water and collagen.

Question 42

A 15-year-old female is diagnosed with conventional high-grade intramedullary osteosarcoma of the distal femur. Staging reveals no macroscopic metastatic disease. What is the most standard, evidence-based treatment algorithm for this patient?

Explanation

The standard of care for conventional high-grade osteosarcoma is neoadjuvant (preoperative) chemotherapy, followed by wide surgical resection with limb salvage, and concluding with adjuvant chemotherapy. Osteosarcoma is considered generally radioresistant.

Question 43

A 13-year-old obese male presents to the emergency department with severe right hip pain after a minor fall. He is completely unable to bear weight on the right leg. Radiographs reveal a slipped capital femoral epiphysis (SCFE). According to the Loder classification, what is the primary clinical significance of this presentation?

Explanation

The Loder classification divides SCFE into stable (able to bear weight) and unstable (unable to bear weight, even with crutches). Unstable SCFE has a significantly higher risk of avascular necrosis (nearly 50%) compared to stable SCFE.

Question 44

A 19-year-old male complains of severe, progressively worsening pain in his left thigh that is notably worse at night. The pain is rapidly relieved by ibuprofen. A CT scan reveals a 0.8 cm radiolucent nidus surrounded by reactive sclerosis in the femoral diaphysis. What is the primary mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) relieve this patient's pain?

Explanation

The classic presentation of an osteoid osteoma is night pain exquisitely relieved by NSAIDs. This is due to the high concentration of Prostaglandin E2 (PGE2) produced by the central nidus, which is inhibited by NSAIDs via cyclooxygenase blockade.

Question 45

A 25-year-old manual laborer presents with dorsal wrist pain, decreased grip strength, and limited range of motion. Radiographs demonstrate sclerosis and fragmentation of the lunate. Which of the following anatomic variants is most strongly associated with the development of this condition?

Explanation

Kienbock's disease (avascular necrosis of the lunate) is strongly associated with negative ulnar variance. A relatively short ulna increases the radiolunate contact stress, predisposing the lunate to microtrauma and ischemia.

Question 46

During the physical examination of a 62-year-old male with suspected cervical spondylotic myelopathy, you sharply flick the distal phalanx of the middle finger into flexion. In response, you observe reflex flexion of the patient's thumb and index finger. What is the name of this pathologic reflex?

Explanation

The Hoffmann sign is elicited by flicking the distal phalanx of the middle finger, resulting in reflex flexion of the thumb and index finger. It indicates upper motor neuron dysfunction and is a classic finding in cervical myelopathy.

Question 47

A 68-year-old female undergoes a total hip arthroplasty via a posterior approach. Postoperatively, she is unable to actively dorsiflex her ankle or extend her great toe, and has numbness over the dorsum of her foot. Which division of the sciatic nerve was most likely injured, and what is its anatomic position relative to the main nerve bundle?

Explanation

The patient has a foot drop, indicating injury to the peroneal (fibular) division of the sciatic nerve. The peroneal division is more susceptible to injury during hip surgery because it is located laterally and posteriorly, with less protective connective tissue.

Question 48

A 24-year-old professional baseball pitcher presents with vague anterior shoulder pain, a "dead arm" sensation, and clicking during the late cocking phase of throwing. MRI arthrogram reveals a tear of the superior labrum with detachment of the biceps anchor from the superior glenoid tubercle. According to the Snyder classification, what type of SLAP lesion is this?

Explanation

A Snyder Type II SLAP lesion involves detachment of the superior labrum and the origin of the long head of the biceps tendon from the glenoid. It is the most common type of SLAP tear and frequently causes "dead arm" syndrome in overhead athletes.

Question 49

A 75-year-old man undergoes a cemented hemiarthroplasty for a displaced femoral neck fracture. During cement pressurization and stem insertion, his blood pressure acutely drops, and his oxygen saturation falls to 82%. Which of the following is the primary pathophysiological mechanism responsible for this acute intraoperative event?

Explanation

Bone cement implantation syndrome is primarily caused by the embolization of fat, marrow, and air into the pulmonary circulation during cement pressurization. While monomer toxicity was historically suspected, transesophageal echocardiography has repeatedly demonstrated massive embolic showers during stem insertion.

Question 50

A 32-year-old woman presents with knee pain. Radiographs reveal an eccentric, lytic epiphyseal lesion extending into the subchondral bone of the distal femur. A biopsy confirms a giant cell tumor of bone. If medical therapy is indicated to shrink the tumor prior to intralesional curettage, which of the following mechanisms best describes the action of the most appropriate drug?

Explanation

Denosumab is a monoclonal antibody used to treat giant cell tumors of bone by binding to RANKL, preventing the activation of RANK on osteoclasts and osteoclast-like giant cells. This halts bone resorption and allows the stroma to form woven bone, facilitating easier surgical curettage.

Question 51

A 12-year-old boy with a BMI in the 99th percentile presents to the emergency department with acute-on-chronic hip pain and is unable to bear weight on the affected limb. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following defines an 'unstable' SCFE according to the Loder classification, and what is its most devastating complication?

Explanation

According to the Loder classification, an unstable SCFE is defined by the patient's inability to bear weight, even with assistive devices. Unstable slips carry a significantly higher risk (up to 50%) of developing avascular necrosis (AVN) of the femoral head compared to stable slips.

Question 52

A 28-year-old man sustains a closed tibial shaft fracture. Two hours post-admission, he develops severe pain out of proportion to the injury. Which of the following physiological pressure parameters is the most reliable threshold to definitively diagnose acute compartment syndrome and indicate emergency fasciotomy?

Explanation

The delta pressure, calculated as diastolic blood pressure minus absolute compartment pressure, is the most reliable indicator for compartment syndrome. A delta pressure of less than 30 mmHg indicates inadequate tissue perfusion and is a strict indication for emergent fasciotomy.

Question 53

A 22-year-old athlete is recovering from an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft. During which phase of graft healing is the structural integrity of the graft at its weakest point, making it highly susceptible to rupture?

Explanation

The revascularization phase occurs typically between 6 to 12 weeks postoperatively. During this time, the graft undergoes remodeling and cell repopulation, which transiently decreases its mechanical strength and represents the weakest point of the graft.

Question 54

A 65-year-old man presents with progressive clumsiness in his hands, difficulty buttoning his shirt, and a wide-based gait. Physical examination reveals a positive Hoffmann sign and hyperreflexia in both lower extremities. What is the most sensitive early clinical symptom of this condition?

Explanation

The patient has cervical spondylotic myelopathy (CSM). The most sensitive and earliest clinical symptom of CSM is a loss of fine motor skills, often described by patients as clumsiness in their hands or difficulty with tasks like buttoning a shirt or writing.

Question 55

A 55-year-old active female undergoes a total hip arthroplasty with a ceramic-on-ceramic bearing surface. Two years later, she complains of a loud squeaking noise from her hip with deep flexion and pivoting. What is the most likely biomechanical cause of this phenomenon?

Explanation

Squeaking is a specific complication associated with ceramic-on-ceramic total hip arthroplasties. It is primarily caused by edge loading and microseparation of the femoral head from the liner, which leads to 'stripe wear' on the ceramic head and alters the fluid lubrication film.

Question 56

A 40-year-old mechanic presents with severe pain and swelling in his right index finger after a puncture wound 2 days ago. You suspect flexor tenosynovitis. Which of Kanavel's four cardinal signs is considered the most specific, eliciting the earliest and most severe pain?

Explanation

Kanavel's signs indicate pyogenic flexor tenosynovitis. Pain with passive extension is considered the most sensitive, specific, and often the earliest sign of this infection, as it maximally stretches the inflamed tendon sheath.

Question 57

A 24-year-old football player sustains a hyper-plantarflexion injury to his foot. Radiographs show a widened interval between the first and second metatarsal bases. The primary ligament injured in this condition connects which two anatomical structures?

Explanation

The Lisfranc ligament is an interosseous ligament that is essential for the stability 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 58

Bone Morphogenetic Proteins (BMPs) are used clinically to enhance bone healing. Recombinant human BMP-2 (rhBMP-2) has FDA approval for which of the following specific orthopedic applications?

Explanation

rhBMP-2 (Infuse) is FDA-approved specifically for acute, open tibial shaft fractures stabilized with an intramedullary nail and for single-level anterior lumbar interbody fusion (ALIF) using an approved interbody cage.

Question 59

A 30-year-old man undergoes excision of a deep-seated, slow-growing soft tissue mass in his thigh. Histopathology reveals a biphasic pattern of spindle cells and epithelial cells. Molecular testing identifies a t(X;18)(p11;q11) chromosomal translocation. What is the diagnosis?

Explanation

Synovial sarcoma is uniquely characterized by the t(X;18)(p11;q11) translocation, which results in the SYT-SSX fusion gene. It often presents in young adults as a deep soft-tissue mass near joints, though it rarely involves the synovium directly.

Question 60

A 25-year-old man sustains a highly vertical femoral neck fracture (Pauwels Type III) in a motor vehicle accident. Biomechanically, which fixation construct provides the highest resistance to the vertical shear forces inherent to this fracture pattern?

Explanation

Pauwels Type III femoral neck fractures in young patients have high vertical shear forces, leading to a high rate of varus collapse and nonunion. A sliding hip screw combined with a derotational screw provides superior biomechanical stability against vertical shear compared to multiple cancellous screws.

Question 61

A 2-week-old infant is being treated for congenital idiopathic clubfoot (talipes equinovarus) using the Ponseti method. According to this technique, what is the very first deformity that must be corrected through manipulation and casting?

Explanation

The Ponseti method follows the acronym CAVE (Cavus, Adductus, Varus, Equinus) for the order of correction. The first step is to correct the midfoot cavus by elevating the first ray to align the forefoot with the hindfoot.

Question 62

A 35-year-old man is involved in a high-speed motor vehicle collision resulting in a hyperextension-axial loading injury to his cervical spine. Radiographs show bilateral fractures through the pars interarticularis of C2. This injury is best described as which of the following?

Explanation

A Hangman's fracture is a traumatic spondylolisthesis of the axis (C2), characterized by bilateral fractures through the pars interarticularis. It is classically caused by a hyperextension and axial loading mechanism.

Question 63

A 21-year-old man sustains a fall onto an outstretched hand and is diagnosed with a proximal pole scaphoid fracture. Why is this specific fracture location at an extraordinarily high risk for developing avascular necrosis and nonunion?

Explanation

The scaphoid receives its primary blood supply from the dorsal carpal branch of the radial artery, which enters at the distal pole and flows retrograde to the proximal pole. Fractures at the proximal pole sever this retrograde supply, resulting in a high rate of avascular necrosis.

Question 64

To reduce polyethylene wear in total hip arthroplasty, manufacturers utilize highly cross-linked ultra-high-molecular-weight polyethylene (UHMWPE). While cross-linking successfully decreases abrasive and adhesive wear, it negatively alters which mechanical property of the polyethylene?

Explanation

Irradiation to create highly cross-linked polyethylene significantly reduces adhesive and abrasive wear. However, it compromises the material's mechanical properties, specifically reducing its ultimate tensile strength, fatigue resistance, and fracture toughness.

Question 65

A 45-year-old construction worker sustains an open midshaft tibia fracture after a beam falls on his leg. There is an 8 cm soft tissue defect with exposed bone, massive muscle crush injury, and an absent dorsalis pedis pulse that requires surgical arterial repair to salvage the limb. What is the correct Gustilo-Anderson classification for this injury?

Explanation

The Gustilo-Anderson Type IIIC classification is defined by any open fracture associated with an arterial injury that requires surgical repair for limb viability, regardless of the size of the soft tissue defect.

Question 66

A 5-year-old boy presents after falling from the monkey bars with a significantly swollen, deformed elbow. Radiographs show an extension-type Gartland III supracondylar humerus fracture. Which of the following physical exam findings indicates the most commonly injured nerve in this 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. Injury to the AIN results in weakness of the flexor pollicis longus and flexor digitorum profundus to the index finger, presenting as an inability to form the "A-OK" sign.

Question 67

A 24-year-old rugby player with recurrent anterior shoulder instability is undergoing preoperative evaluation. The 'glenoid track' concept is used to determine his risk of recurrent postoperative dislocation. An 'off-track' Hill-Sachs lesion is best managed by arthroscopic Bankart repair with which concurrent procedure?

Explanation

An 'off-track' Hill-Sachs lesion indicates that the humeral head defect engages the anterior glenoid rim during abduction and external rotation. To prevent this engagement and recurrent dislocation, a remplissage (filling the defect with the infraspinatus tendon) is performed concurrently with a Bankart repair.

Question 68

A 60-year-old patient with long-standing poorly controlled diabetes presents with a unilaterally red, hot, swollen foot without an open ulcer. Radiographs reveal prominent periarticular fragmentation, debris, and subluxation of the midfoot joints. This represents Eichenholtz Stage I Charcot arthropathy. What is the most appropriate initial management?

Explanation

The patient is in the acute fragmentation phase (Stage I) of Charcot arthropathy, mimicking an infection. The gold standard for initial management is immediate offloading and immobilization using a total contact cast to halt progressive deformity while waiting for the inflammatory phase to coalesce (Stage II).

Question 69

A 15-year-old girl presents with a distal femur osteosarcoma. Which of the following tumor suppressor genes, frequently mutated in osteosarcoma, directly controls the G1 to S phase transition in the cell cycle?

Explanation

The Retinoblastoma (Rb) gene product is a tumor suppressor that prevents the cell from progressing from the G1 to the S phase of the cell cycle. Mutations in the Rb gene are strongly associated with the development of osteosarcoma.

Question 70

In a polytraumatized patient, which of the following physiologic markers is the most reliable early biochemical indicator of adequate resuscitation to allow clearance for definitive early total care (ETC) fracture fixation?

Explanation

Serum lactate levels below 2.0 mmol/L and a normalizing base deficit are critical indicators of adequate tissue perfusion and end-organ resuscitation. Normalizing lactate is heavily relied upon to safely transition a patient from damage control orthopedics to definitive early total care.

Question 71

A 65-year-old man presents with groin pain 5 years after a metal-on-polyethylene total hip arthroplasty. Aspiration yields fluid with numerous macrophages containing metallic debris. Which of the following implant factors most significantly increases the risk of mechanically assisted crevice corrosion (trunnionosis)?

Explanation

Increased femoral head size increases the frictional torque and toggling forces at the head-neck junction (trunnion). This excess mechanical stress disrupts the passivation layer of the metal, leading to mechanically assisted crevice corrosion.

Question 72

Bone morphogenetic proteins (BMPs) initiate osteoinductive signaling pathways. Upon BMP binding to its surface receptor, which intracellular signaling molecules are directly phosphorylated to translocate to the nucleus?

Explanation

BMPs bind to serine-threonine kinase receptors, which then phosphorylate receptor-regulated Smads (Smad 1, 5, and 8). These form a complex with co-Smad 4 and translocate to the nucleus to regulate target gene transcription for osteoblast differentiation.

Question 73

A 12-year-old obese male undergoes in-situ percutaneous pinning for a stable slipped capital femoral epiphysis (SCFE). Postoperatively, he develops severe hip pain and restriction of all hip movements. Radiographs show joint space narrowing without a joint effusion. What is the most likely diagnosis?

Explanation

Chondrolysis is a devastating complication of SCFE characterized by acute loss of articular cartilage and diffuse joint space narrowing. It presents with severe stiffness and pain, often linked to unrecognized intra-articular hardware penetration.

Question 74

Denosumab is increasingly used as a neoadjuvant treatment for large, marginally resectable Giant Cell Tumors (GCT) of bone. What is the specific mechanism of action of this medication?

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). This prevents RANKL from binding to RANK on osteoclasts and giant cells, halting osteoclast-mediated bone destruction.

Question 75

Biomechanical studies of the flexor tendon sheath in the hand demonstrate that isolated rupture of which two annular pulleys will result in the greatest degree of flexor tendon bowstringing and loss of active interphalangeal joint flexion?

Explanation

The A2 and A4 pulleys arise from the periosteum of the proximal and middle phalanges, respectively. They are the most critical biomechanical pulleys for preventing flexor tendon bowstringing and maintaining the excursion efficiency of digit flexion.

Question 76

Following a complete peripheral nerve transection (neurotmesis) and primary epineural repair, at what approximate rate does the regenerating axonal cone advance down the distal nerve sheath?

Explanation

After Wallerian degeneration and a brief latent period, axonal regeneration proceeds at an average rate of approximately 1 mm/day (or 1 inch/month). This rate is highly dependent on patient age, nerve type, and the local injury environment.

Question 77

During normal knee flexion, the femoral contact point translates posteriorly on the tibial plateau, a phenomenon known as femoral rollback. Which ligament is the primary driver of this kinematic movement?

Explanation

The Posterior Cruciate Ligament (PCL) tightens during deep knee flexion, drawing the femoral condyles posteriorly on the tibia. This femoral rollback improves the extensor mechanism lever arm and prevents posterior impingement to maximize flexion.

Question 78

The Lisfranc ligament is a critical stabilizing structure of the midfoot. Between which two osseous structures does the primary, strongest interosseous band of the Lisfranc ligament course?

Explanation

The Lisfranc ligament complex consists of dorsal, plantar, and interosseous bands. The interosseous band is the strongest and courses obliquely from the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal.

Question 79

The lateral pillar classification (Herring) is widely used for prognostication in Legg-Calvé-Perthes disease. In a Herring Group C hip, what is the radiographic appearance of the lateral pillar of the femoral head?

Explanation

The Herring classification evaluates the height of the lateral portion of the femoral head on an AP radiograph during the fragmentation phase. Group C is defined as less than 50% maintenance of normal lateral pillar height, and it carries the worst prognosis.

Question 80

In the Thoracolumbar Injury Classification and Severity (TLICS) score, which of the following morphologic patterns is assigned the highest point value for injury morphology?

Explanation

According to the TLICS system, distraction injuries receive 4 points for morphology, making them the highest weighted morphologic injury pattern. Translation/rotation receives 3 points, burst receives 2 points, and compression receives 1 point.

Question 81

Ligaments and tendons exhibit viscoelastic properties. Which of the following terms describes the phenomenon where a tissue is held at a constant length over time, resulting in a gradual decrease in the force required to maintain that length?

Explanation

Stress relaxation is a viscoelastic property where the stress (force) required to maintain a tissue at a constant strain (length) decreases over time. Creep, conversely, is the continued deformation of a tissue over time when subjected to a constant load.

Question 82

Scaphoid nonunion advanced collapse (SNAC) progresses through predictable stages of radiocarpal and midcarpal arthritis. Which articulation is classically spared in a stage III SNAC wrist?

Explanation

In both SNAC and SLAC wrist patterns, the radiolunate articulation is classically spared from degenerative changes. This is due to the concentric, spherical congruency of the radiolunate joint, which maintains stable load distribution despite altered carpal kinematics.

Question 83

A 10-year-old boy presents with a diaphysial tibial lesion and systemic symptoms. A biopsy confirms Ewing sarcoma. Which of the following immunohistochemical markers is most characteristically strongly positive in this tumor?

Explanation

Ewing sarcoma is a small round blue cell tumor that characteristically shows diffuse, strong membranous staining for CD99 (MIC2). This tumor is molecularly driven by the t(11;22) translocation, creating the EWS-FLI1 fusion protein.

Question 84

In a patient with suspected acute compartment syndrome of the lower leg, what is the generally accepted critical delta pressure (Delta P) threshold that mandates emergency fasciotomy?

Explanation

The Delta P is calculated as the diastolic blood pressure minus the measured intracompartmental pressure. A Delta P of less than 30 mmHg indicates inadequate tissue perfusion and is an absolute indication for emergent fasciotomy.

Question 85

When applying a circumferential pelvic binder for a hemodynamically unstable patient with an open-book pelvic ring injury (APC-III), over which specific anatomic landmarks should the binder be centered to maximize reduction force?

Explanation

To be mechanically effective, a pelvic binder or sheet must be centered directly over the greater trochanters. Placing it too cephalad (over the iliac crests) is a common error that fails to adequately close the pelvic volume and can actually paradoxically open the posterior ring.

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Orthopedic Review | Dr Hutaif General Orthopedics Revie -...

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