Following insertion of a cementless femoral component into the total hip arthroplasty construct, the amount of femoral stress shielding is most associated with

presurgical bone mineral density.

Hippainofmonthdurationhasdevelopedinayear-oldmanwithaprevioustotalhiparthroplasty. Heunderwentdentalwork6weeksago.Aspirationshowsawhitebloodcellcountofmorethan6,000cells/μL(referencerange4,500to11,000cells/μL)andthepresenceofgram-positivecocciinclust

Poor because it is a late infection

Following an acute dislocation of the patella, the risk of a recurrent dislocation is greater if the patient has which of the following findings?

Passive lateral hypermobility of the unaffected knee

-What factor is most commonly associated with malignant transformation of a giant cell tumor?

previous treatment of the tumor with radiation therapy

A 50-year-old man fell from a ladder onto his left shoulder and sustained the injury shown in the radiographs in Figures 71a and 71b. He underwent surgery with repair of the coracoclavicular ligaments and deltotrapezial fascia with coracoclavicular s

Acromioclavicular arthritis is more likely than with nonsurgical management.

When planning scoliosis surgery for a patient with a 50-degree thoracolumbar curve and spinal muscular atrophy, it is most important to include

an evaluation for lower extremity muscle contractures.

Dr. Hutaif's General Orthopedics Review & Practice MCQs

Question 1

Distraction osteogenesis (Ilizarov technique) is a powerful method utilized in orthopedics for limb lengthening and deformity correction. This process primarily relies on which of the following biological mechanisms of bone formation?

Explanation

Distraction osteogenesis is characterized by direct bone formation without a cartilaginous intermediate, which is the definition of intramembranous ossification. The mechanical tension applied across the osteotomy site directly stimulates osteoblastic activity from the periosteum and endosteum.

Question 2

A 28-year-old male sustains an isolated, high-energy closed midshaft tibia fracture. He is obtunded due to a concurrent closed head injury. Which of the following parameters is widely considered the most reliable threshold to diagnose acute compartment syndrome requiring emergent fasciotomy?

Explanation

The delta pressure (Diastolic BP minus absolute compartment pressure) of less than 30 mmHg is the most reliable objective indicator for acute compartment syndrome. Absolute pressures can be misleading, especially in hypotensive or hypertensive patients, making delta pressure the standard indication for fasciotomy, particularly in obtunded patients.

Question 3

An infant is being treated for Developmental Dysplasia of the Hip (DDH) using a Pavlik harness. During a follow-up visit, the infant is noted to have decreased active knee extension on the treated side. This complication is most commonly associated with which of the following positioning errors?

Explanation

In a Pavlik harness, excessive flexion of the hips (>120 degrees) can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy (manifesting as decreased active quadriceps extension). Conversely, excessive hyperabduction is associated with avascular necrosis (AVN) of the femoral head.

Question 4

A 14-year-old patient is diagnosed with localized, high-grade osteosarcoma of the distal femur. Following wide surgical resection and reconstruction, the pathology report is reviewed. What is the single most significant prognostic factor for this patient's long-term overall survival?

Explanation

The degree of tumor necrosis after neoadjuvant chemotherapy is the single most important prognostic indicator for overall survival in patients with localized, high-grade osteosarcoma. A good response is typically defined as greater than 90% tumor necrosis.

Question 5

In the manufacturing of highly cross-linked polyethylene (HXLPE) for total joint arthroplasty, gamma irradiation is used to induce cross-linking to improve wear resistance. However, this process creates free radicals. Which of the following subsequent steps is utilized to eliminate these free radicals and reduce long-term oxidation, despite causing a slight decrease in the material's fatigue strength?

Explanation

Remelting the polyethylene above its melting point (typically around 150°C) allows free radicals created during the irradiation process to recombine and be eliminated. This prevents long-term oxidative degradation. However, it alters the crystalline structure, which slightly reduces the material's ultimate tensile strength and fatigue properties.

Question 6

A 45-year-old male presents following a high-speed motor vehicle collision with a T6 burst fracture and complete paraplegia. In the trauma bay, his blood pressure is 80/50 mmHg, heart rate is 55 bpm, and his extremities are warm and flushed. Which of the following best describes the pathophysiology of his current hemodynamic state?

Explanation

The patient is exhibiting classic signs of neurogenic shock, which occurs in spinal cord injuries typically at or above the T6 level. It is characterized by a loss of descending sympathetic outflow to the splanchnic bed and heart, leading to unopposed vagal (parasympathetic) tone, profound vasodilation, bradycardia, hypotension, and warm extremities.

Question 7

Normal articular cartilage is a highly specialized connective tissue. Which component of the extracellular matrix is primarily responsible for providing compressive stiffness by drawing water into the tissue via the Donnan osmotic effect?

Explanation

Aggrecan is the most abundant large proteoglycan in articular cartilage. Its highly negatively charged glycosaminoglycan (GAG) side chains repel each other and attract cations and water into the matrix, providing the tissue with its characteristic compressive stiffness. Type II collagen network provides the tensile strength to resist this swelling pressure.

Question 8

During the surgical exploration of a flexor tendon laceration in Zone II of the hand, it is critical to handle the tendons delicately. The primary nutritional supply to the flexor digitorum profundus (FDP) within this fibro-osseous digital sheath is known to be derived from which of the following mechanisms?

Explanation

While the vincula (longa and brevia) provide some segmental blood supply to the dorsal aspect of the flexor tendons, the primary source of nutrition for the flexor tendons within the relatively avascular digital sheaths (Zone II) is via imbibition and diffusion from the surrounding synovial fluid.

Question 9

A 22-year-old athlete sustains a non-contact knee injury with a reported 'pop'. Initial radiographs reveal a small avulsion fracture of the lateral aspect of the proximal tibial plateau. This radiographic finding (Segond fracture) is virtually pathognomonic for an injury to which of the following structures?

Explanation

A Segond fracture is an avulsion fracture of the anterolateral tibial plateau, specifically involving the insertion of the anterolateral ligament (ALL) or lateral capsular ligament. It is highly specific (pathognomonic) for a tear of the anterior cruciate ligament (ACL).

Question 10

According to the Gustilo-Anderson classification, a highly contaminated open diaphyseal tibia fracture presenting with extensive soft tissue stripping, but maintaining adequate local soft tissue coverage for the bone without requiring a flap, is classified as which of the following?

Explanation

A Type IIIA open fracture involves extensive soft tissue laceration or stripping, often associated with high-energy trauma or severe contamination, but the bone is adequately covered by local soft tissue, precluding the need for a local or free flap. Type IIIB requires a rotational or free flap for coverage, and Type IIIC involves an arterial injury requiring repair.

Question 11

The 'watershed area' of the Achilles tendon is the most frequent anatomical site for tendinopathy and acute rupture due to its relative hypovascularity. This susceptible zone is typically located at what distance proximal to the tendon's insertion on the calcaneal tuberosity?

Explanation

The watershed zone of the Achilles tendon is a relatively hypovascular region located approximately 2 to 6 cm proximal to its insertion on the calcaneus. This poor intrinsic blood supply contributes to its susceptibility to degeneration and rupture.

Question 12

On a standard stress-strain curve representing the biomechanical properties of an orthopedic implant material, what specific mechanical behavior does the 'yield point' denote?

Explanation

The yield point on a stress-strain curve marks the limit of linear elastic behavior. Beyond this specific stress level, the material begins to undergo plastic (permanent) deformation and will not return to its original shape when the load is removed.

Question 13

A 9-year-old boy presents with an insidious onset of a limp, thigh pain, and obligatory external rotation of the hip with flexion. He is noted to be significantly shorter than his peers, plotting below the 5th percentile for height. Radiographs confirm a bilateral Slipped Capital Femoral Epiphysis (SCFE). Given his age and presentation, which of the following underlying systemic conditions must be highly suspected?

Explanation

SCFE typically occurs during the adolescent growth spurt (males 12-16 years, females 10-14 years). When it presents in a patient outside this typical age range (e.g., <10 years), with bilateral involvement, or in a patient with short stature, an underlying endocrine abnormality should be strongly suspected, with hypothyroidism being the most common association.

Question 14

A 65-year-old female presents with progressive back pain and fatigue. Radiographs demonstrate multiple 'punched-out' lytic lesions in her skull and lumbar vertebral bodies without a sclerotic rim. Laboratory analysis reveals hypercalcemia, anemia, and an elevated serum creatinine. The primary neoplastic cells involved in this disease process are derived from which of the following cellular lineages?

Explanation

The clinical presentation (CRAB criteria: Calcium elevation, Renal insufficiency, Anemia, Bone lesions) and radiographic findings are classic for Multiple Myeloma, the most common primary malignancy of bone in adults. It is characterized by the neoplastic clonal proliferation of plasma cells, which are terminally differentiated B-lymphocytes.

Question 15

A 48-year-old typist complains of night-time awakening with numbness and tingling in her thumb, index, and long fingers. Which of the following clinical tests or signs is considered the most sensitive modality for detecting early sensory nerve fiber compression in Carpal Tunnel Syndrome?

Explanation

Semmes-Weinstein monofilament testing assesses thresholds of touch/pressure sensation, mediated by slowly adapting nerve fibers. It is considered the most sensitive clinical physical exam test for detecting early nerve compression in carpal tunnel syndrome, turning positive before changes in two-point discrimination (which measures innervation density) occur.

Question 16

A 35-year-old male arrives hemodynamically unstable following a motorcycle crash. Pelvic radiographs demonstrate an Anteroposterior Compression Type III (APC-III) pelvic ring disruption with a completely widened symphysis and completely disrupted sacroiliac joints. What is statistically the most common anatomical source of the massive retroperitoneal hemorrhage in this injury pattern?

Explanation

Despite the dramatic nature of arterial bleeding, approximately 80-90% of massive hemorrhage in severe pelvic fractures is venous in origin, primarily arising from the disrupted presacral venous plexus and the large surfaces of exposed cancellous bone at the fracture sites. Arterial bleeding accounts for the minority of cases.

Question 17

Titanium alloys (e.g., Ti-6Al-4V) are extensively utilized in modern orthopaedic implants due to excellent biocompatibility and osseointegration properties. Compared to Cobalt-Chromium (CoCr) alloys, Titanium alloys possess which of the following distinct biomechanical profiles?

Explanation

Titanium alloys have a lower modulus of elasticity (closer to that of cortical bone) compared to CoCr or stainless steel, which beneficially reduces stress shielding. However, titanium is highly notch-sensitive and has notoriously poor wear properties, making it entirely unsuitable for use as an articular bearing surface in joint arthroplasty.

Question 18

During a primary total knee arthroplasty utilizing a posterior-stabilized (PS) implant design, a central cam-and-post mechanism is incorporated. This specific design feature is intended to primarily substitute for which of the following native knee kinematic functions?

Explanation

In the native knee, the posterior cruciate ligament (PCL) forces the femur to slide posteriorly (rollback) on the tibia during deep flexion, which improves clearance and maximizes the flexion arc. In a PCL-substituting (PS) total knee arthroplasty, the interaction between the polyethylene tibial post and the femoral cam engages during mid-flexion to artificially replicate this posterior femoral rollback.

Question 19

A 55-year-old male presents with acute onset of severe low back pain, bilateral flaccid lower extremity weakness, absent ankle reflexes, and overflow urinary incontinence. Examination reveals decreased perianal sensation. The underlying pathophysiology of this specific neurologic syndrome represents compression of which of the following nervous system elements?

Explanation

This patient is presenting with Cauda Equina Syndrome, caused by compression of the lumbosacral nerve roots below the termination of the spinal cord (conus medullaris, usually at L1-L2). Because these nerve roots have already exited the spinal cord, the syndrome represents a peripheral, lower motor neuron (LMN) lesion, characterized by flaccid paralysis, areflexia, and loss of sphincter tone.

Question 20

A 4-year-old girl is brought to the emergency department for refusal to bear weight on her right leg and low-grade fever. To differentiate between transient synovitis and septic arthritis, the Kocher criteria are utilized. Which of the following sets of clinical findings, if all present, provides a 99% predictive probability for a diagnosis of septic arthritis?

Explanation

The classic Kocher criteria are used to differentiate septic arthritis from transient synovitis in children. The four criteria are: 1) Non-weight-bearing on the affected side, 2) Erythrocyte sedimentation rate (ESR) > 40 mm/hr, 3) Fever > 38.5°C (101.3°F), and 4) Serum white blood cell (WBC) count > 12,000/mm³. The presence of all four criteria yields a 99% predicted probability of septic arthritis.

Question 21

A 15-year-old male presents with a painful mass around his right knee. Radiographs reveal a sunburst periosteal reaction in the distal femur. Biopsy confirms high-grade osteosarcoma. Which of the following genetic syndromes is most strongly associated with an increased risk of developing this specific primary bone tumor?

Explanation

Osteosarcoma is strongly associated with retinoblastoma (Rb gene), Li-Fraumeni syndrome (p53 mutation), and Rothmund-Thomson syndrome (RECQL4 helicase mutation). EXT1 is associated with osteochondromas and secondary chondrosarcoma. GNAS1 is seen in fibrous dysplasia and McCune-Albright syndrome. NF1 is associated with malignant peripheral nerve sheath tumors.

Question 22

A 48-year-old female with a history of celiac disease presents with generalized, diffuse bone pain and muscle weakness. Radiographs reveal bilateral pseudo-fractures (Looser zones) in the femoral neck. Which of the following serum laboratory profiles is most characteristic of her underlying condition?

Explanation

The patient has osteomalacia, likely secondary to malabsorption from celiac disease leading to Vitamin D deficiency. The classic laboratory profile for osteomalacia features low-to-normal serum calcium, low phosphorus, elevated alkaline phosphatase, and elevated parathyroid hormone (secondary hyperparathyroidism).

Question 23

When utilizing the 'delta pressure' concept to diagnose acute compartment syndrome, which of the following calculations is used to determine the threshold for fasciotomy?

Explanation

The delta pressure is calculated as the Diastolic Blood Pressure minus the Compartment Pressure. A delta pressure of 30 mmHg or less is highly indicative of acute compartment syndrome and is a standard indication for emergent fasciotomy.

Question 24

A patient is prescribed rivaroxaban for deep vein thrombosis prophylaxis following total hip arthroplasty. What is the specific mechanism of action of this medication?

Explanation

Rivaroxaban and Apixaban are direct oral anticoagulants (DOACs) that act by directly inhibiting Factor Xa in the coagulation cascade. Dabigatran is a direct thrombin inhibitor. Warfarin inhibits Vitamin K epoxide reductase. Low-molecular-weight heparin primarily activates antithrombin III to inhibit Factor Xa.

Question 25

During the reparative phase of tendon healing, fibroblasts synthesize a temporary extracellular matrix. Which type of collagen predominates in this early provisional matrix before being remodeled into the mature tendon structure?

Explanation

In the early proliferative/reparative phase of tendon healing, fibroblasts rapidly synthesize Type III collagen. During the remodeling phase, this weaker, disorganized Type III collagen is gradually replaced by stronger, highly organized Type I collagen, which makes up the bulk of mature healthy tendons.

Question 26

A 45-year-old malnourished male presents with generalized joint aches, perifollicular hemorrhages, and poor wound healing. He is diagnosed with a severe vitamin deficiency. At a cellular level, this deficiency primarily impairs which step of collagen synthesis?

Explanation

The patient has scurvy (Vitamin C deficiency). Vitamin C is an essential cofactor for prolyl hydroxylase and lysyl hydroxylase. Without it, the hydroxylation of proline and lysine residues in the rough endoplasmic reticulum is impaired, preventing proper hydrogen bonding and stabilization of the collagen triple helix.

Question 27

According to Perren's strain theory of fracture healing, which of the following tissues is capable of tolerating the highest percentage of interfragmentary strain before rupturing?

Explanation

Perren's strain theory dictates that tissues will only form in a fracture gap if the interfragmentary strain is lower than the strain tolerance of that specific tissue. Granulation tissue can tolerate up to 100% strain, fibrocartilage tolerates roughly 10-15%, and solid bone (woven/lamellar) tolerates very little strain (<2%).

Question 28

A 32-year-old female with an aggressive giant cell tumor of the distal radius is started on denosumab therapy prior to surgical intervention. This monoclonal antibody exerts its therapeutic effect by directly binding to and inhibiting which of the following?

Explanation

Denosumab is a monoclonal antibody that mimics the action of osteoprotegerin (OPG) by binding directly to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). This prevents RANKL from binding to the RANK receptor on osteoclast precursors, thereby inhibiting osteoclast formation, function, and survival.

Question 29

During the incorporation of a massive structural cortical allograft, the process by which osteoclasts resorb the dead bone graft while osteoblasts simultaneously lay down new viable host bone is termed:

Explanation

Creeping substitution is the histomorphologic process of bone graft incorporation where simultaneous osteoclastic resorption of the graft and osteoblastic deposition of new viable host bone occurs. Cortical grafts undergo this process much slower than cancellous grafts.

Question 30

A 68-year-old male is evaluated for an enlarging hat size and right hip pain. Radiographs reveal cortical thickening and coarse trabeculae in the pelvis. A bone biopsy is obtained. Which of the following histologic findings is the hallmark of the mixed phase of this disease?

Explanation

The patient has Paget's disease of bone. The classic histologic hallmark of the mixed (intermediate) phase of Paget's disease is a 'mosaic' or 'jigsaw puzzle' pattern of lamellar bone with prominent, disorganized cement lines, reflecting chaotic and rapid cycles of osteoclastic resorption and osteoblastic bone formation.

Question 31

A patient undergoing an orthopedic procedure under general anesthesia develops generalized muscle rigidity, tachycardia, and a rapid rise in core body temperature. The underlying pathophysiology of this life-threatening event involves a genetic mutation in which of the following?

Explanation

Malignant hyperthermia is an autosomal dominant pharmacogenetic disorder most commonly caused by a mutation in the Ryanodine receptor 1 (RYR1) gene on chromosome 19. Exposure to triggering agents causes massive, uncontrolled calcium release from the sarcoplasmic reticulum.

Question 32

In an effort to prevent the development of Complex Regional Pain Syndrome (CRPS) following a conservatively managed distal radius fracture, the American Academy of Orthopaedic Surgeons (AAOS) recommends which of the following oral prophylactic therapies?

Explanation

The daily administration of 500 mg of Vitamin C for 50 days following a distal radius fracture has been shown to significantly reduce the risk of developing CRPS, primarily through its antioxidant and free radical scavenging properties.

Question 33

A 9-year-old boy living in Connecticut presents with an acute effusion of his right knee. A joint aspiration demonstrates 45,000 WBCs/mm3. Serologic testing is positive for Borrelia burgdorferi. What is the primary vector responsible for transmitting this pathogen?

Explanation

Lyme disease is caused by the spirochete Borrelia burgdorferi and is transmitted by the bite of the black-legged tick, Ixodes scapularis (in the northeastern and midwestern US) or Ixodes pacificus (on the West Coast).

Question 34

Slipped capital femoral epiphysis (SCFE) typically occurs in overweight adolescents undergoing a rapid growth spurt. Which of the following patient profiles should prompt an immediate and thorough laboratory workup for an underlying endocrine or renal abnormality?

Explanation

Atypical SCFE presentations that warrant an endocrine workup (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency) include age of onset less than 10 years or greater than 16 years, and weight less than the 50th percentile.

Question 35

A 65-year-old patient presents with acute, severe pain and swelling in the right knee. Joint fluid aspiration reveals weakly positively birefringent, rhomboid-shaped crystals under compensated polarized light microscopy. Which of the following is the most likely composition of these crystals?

Explanation

Calcium pyrophosphate dihydrate (CPPD) crystals, the causative agent in pseudogout, are classically rhomboid-shaped and exhibit weakly positive birefringence. Monosodium urate crystals (gout) are needle-shaped and negatively birefringent.

Question 36

Osteogenesis Imperfecta (OI) is a genetic disorder of Type I collagen biosynthesis. According to the Sillence classification, which type of OI is characterized as the perinatal lethal form, often presenting with multiple intrauterine fractures and an under-mineralized calvarium?

Explanation

Sillence Type II Osteogenesis Imperfecta is the most severe and is typically lethal in the perinatal period due to severe pulmonary hypoplasia and massive skeletal fragility. Type I is the mildest form.

Question 37

Rituximab is a biologic disease-modifying antirheumatic drug (DMARD) occasionally utilized in patients with refractory Rheumatoid Arthritis. What is the specific cellular target of Rituximab?

Explanation

Rituximab is a chimeric monoclonal antibody directed against the CD20 antigen found on the surface of B lymphocytes, leading to B-cell depletion. Adalimumab targets TNF-alpha, Tocilizumab targets IL-6, and Abatacept targets CTLA-4.

Question 38

A patient presents with a deep forearm laceration. On physical examination, they are completely unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (unable to make an 'OK' sign). Which of the following nerve branches and corresponding muscles are paralyzed?

Explanation

The inability to make the 'OK' sign implies loss of flexion at the IP joint of the thumb and DIP joint of the index finger. These movements are controlled by the Flexor Pollicis Longus (FPL) and the radial half of the Flexor Digitorum Profundus (FDP), both innervated by the Anterior Interosseous Nerve (AIN).

Question 39

In total joint arthroplasty, early generations of ultra-high-molecular-weight polyethylene (UHMWPE) components were sterilized with gamma irradiation in the presence of air. This process introduced free radicals, leading to a specific structural degradation and subsequent failure mode. Which type of wear was most significantly accelerated by this process?

Explanation

Gamma irradiation of UHMWPE in an oxygen-rich environment (air) leads to the creation of free radicals that combine with oxygen, causing chain scission and subsurface oxidation. This degradation severely lowers the mechanical strength of the polyethylene, heavily predisposing it to fatigue wear (delamination and pitting).

Question 40

Electrodiagnostic testing is often used to evaluate peripheral nerve injuries. During nerve conduction studies (NCS), what specific physiologic parameter does the F-wave primarily assess?

Explanation

The F-wave is a late motor response that evaluates conduction along the entire length of the nerve, particularly the proximal segments and nerve roots. It occurs when a supramaximal stimulus travels antidromically to the anterior horn cell, causing a backfire that travels orthodromically down to the muscle, making it highly useful for detecting radiculopathies.

Question 41

In biomechanical evaluation of tendons, the phenomenon where a tendon subjected to a constant displacement demonstrates a gradual decrease in measured tension over time is best described by which of the following terms?

Explanation

Stress relaxation occurs when a viscoelastic material experiences a decrease in stress under constant deformation. Creep is the progressive deformation of a material under constant load.

Question 42

A 12-year-old boy presents with a painful, permeative diaphyseal lesion in his femur with an associated soft tissue mass. Biopsy confirms small blue round cells. Which of the following genetic translocations is most pathognomonic for this tumor?

Explanation

Ewing sarcoma is classically associated with the t(11;22) translocation, leading to the EWS-FLI1 fusion protein. Synovial sarcoma is associated with t(X;18), and alveolar rhabdomyosarcoma with t(2;13).

Question 43

In the acute management of a hemodynamically unstable patient with an anteroposterior compression (APC) pelvic ring injury, what is the anatomically correct placement level for a circumferential pelvic binder?

Explanation

Pelvic binders must be centered over the greater trochanters to effectively reduce the pelvic volume and stabilize the fracture. Placement over the iliac crests or ASIS can paradoxically open the pelvic ring.

Question 44

During a posterior-stabilized total knee arthroplasty, the surgeon notes that the knee is well-balanced in extension but excessively tight in flexion. Which of the following adjustments is most appropriate to correct this specific mismatch?

Explanation

Downsizing the femoral component utilizing anterior referencing will decrease the posterior condylar offset, effectively increasing the flexion gap without altering the extension gap. Increasing the tibial slope also affects the flexion gap but alters the tibial cut geometry.

Question 45

According to the Ponseti method for treating idiopathic clubfoot, which deformity must be addressed first during the serial casting phase?

Explanation

The components of clubfoot are corrected in the specific order of CAVE: Cavus, Adductus, Varus, then Equinus. The cavus is corrected first by supinating the forefoot to align it with the hindfoot.

Question 46

A 45-year-old male presents to the emergency department with severe lower back pain and bilateral sciatica. Which of the following clinical findings has the highest sensitivity for diagnosing cauda equina syndrome?

Explanation

Urinary retention (typically with a post-void residual volume > 200 mL) is the most sensitive finding in cauda equina syndrome. Its absence has a high negative predictive value for ruling out the condition.

Question 47

A 32-year-old carpenter sustains a puncture wound to his index finger and presents 48 hours later with swelling. Which of Kanavel's four cardinal signs is typically the earliest and most sensitive indicator of infectious flexor tenosynovitis?

Explanation

Pain with passive extension of the affected digit is generally considered the earliest and most sensitive of Kanavel's cardinal signs for infectious flexor tenosynovitis. The other signs typically develop as the infection progresses.

Question 48

In evaluating a patient with recurrent anterior shoulder instability, the concept of the "glenoid track" is utilized to determine the risk of an engaging Hill-Sachs lesion. The glenoid track width is calculated based on which of the following?

Explanation

The glenoid track is approximately 83% of the width of the intact inferior glenoid. To calculate the patient's specific track, the width of the anterior glenoid bone defect is subtracted from this value.

Question 49

Based on current Level 1 evidence comparing operative versus non-operative management of acute Achilles tendon ruptures utilizing an early functional rehabilitation protocol, non-operative management is associated with which of the following outcomes compared to operative treatment?

Explanation

Recent randomized controlled trials utilizing early functional weight-bearing rehabilitation show equivalent re-rupture rates between operative and non-operative groups. However, non-operative management avoids surgical soft-tissue complications and infections.

Question 50

Demineralized bone matrix (DBM) is widely used in orthopedic surgery to augment fracture healing and spinal fusion. DBM relies primarily on which of the following biological properties?

Explanation

DBM provides osteoinduction via bone morphogenetic proteins (BMPs) exposed during the demineralization process, and osteoconduction through its collagen matrix. It lacks live cells, so it is not osteogenic.

Question 51

A 65-year-old male presents with a pathologic fracture of the proximal humerus. Radiographs show a distinct "punched-out" lytic lesion. Laboratory tests reveal an M-spike on serum protein electrophoresis. Which of the following imaging modalities is the most appropriate next step for staging the skeletal extent of this disease?

Explanation

Whole-body low-dose CT is now the standard for staging the skeletal involvement of multiple myeloma, replacing the traditional radiographic skeletal survey. Technetium-99m bone scans rely on osteoblastic activity and often produce false negatives in purely lytic myeloma lesions.

Question 52

A 25-year-old male sustains a vertically oriented (Pauwels Type III) basicervical femoral neck fracture. To maximize biomechanical stability and reduce the risk of shear-induced nonunion, which of the following fixation constructs is biomechanically superior?

Explanation

Vertical femoral neck fractures (Pauwels Type III) experience high shear forces. A fixed-angle device like a sliding hip screw provides superior biomechanical resistance to shear and varus collapse compared to multiple cancellous screws.

Question 53

During the process of secondary bone healing, which type of collagen is predominantly synthesized during the soft callus (chondrogenic) phase before being replaced by hard callus?

Explanation

The soft callus is composed primarily of cartilage, which relies on the synthesis of Type II collagen. As endochondral ossification progresses to hard callus, chondrocytes hypertrophy (producing Type X collagen) and are replaced by osteoblasts producing Type I collagen.

Question 54

The introduction of highly cross-linked polyethylene in total hip arthroplasty has dramatically reduced wear rates. However, the process of cross-linking using irradiation negatively impacts the mechanical properties of the polyethylene. Which step is most commonly added to the manufacturing process to eliminate free radicals and prevent in vivo oxidation?

Explanation

Irradiation creates cross-links but leaves behind free radicals that can cause oxidative degradation over time. Thermal treatments like remelting or annealing are used to quench these free radicals and stabilize the polyethylene.

Question 55

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

Explanation

Patients with an underlying endocrine disorder (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) have a significantly higher risk of bilateral SCFE. Prophylactic pinning of the contralateral side is strongly recommended in these individuals.

Question 56

Traumatic spondylolisthesis of the axis (Hangman's fracture) typically involves bilateral fractures of the C2 pars interarticularis. The classic mechanism of injury leading to a Type I Hangman's fracture is:

Explanation

A Type I Hangman's fracture classically results from hyperextension and axial loading, commonly seen in motor vehicle accidents when the chin strikes the dashboard.

Question 57

A 24-year-old male sustains a proximal pole scaphoid fracture. The risk of avascular necrosis (AVN) is exceptionally high due to the retrograde blood supply to the scaphoid. The predominant blood supply enters the scaphoid at which of the following anatomic locations?

Explanation

The scaphoid receives 70-80% of its blood supply from the dorsal carpal branch of the radial artery. This vessel enters at the dorsal ridge near the waist and flows retrogradely to the proximal pole.

Question 58

A 30-year-old football player presents with midfoot pain after his foot was axially loaded while plantarflexed. Weight-bearing radiographs demonstrate a widening between the first and second metatarsals. The primary Lisfranc ligament connects which two structures?

Explanation

The Lisfranc ligament is a strong interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is critical for the stability of the tarsometatarsal articulation.

Question 59

According to the Gustilo-Anderson classification, a highly comminuted open tibia fracture resulting from a high-velocity gunshot wound with a 2-cm soft tissue laceration and adequate periosteal coverage is best classified as:

Explanation

High-energy injuries, highly comminuted fractures, and high-velocity gunshot wounds are automatically classified as Type III injuries regardless of the size of the wound. Because it has adequate periosteal coverage, it is classified as Type IIIA.

Question 60

Following Anterior Cruciate Ligament (ACL) reconstruction using a Bone-Patellar Tendon-Bone (BPTB) autograft, the graft undergoes a process of "ligamentization". During which phase of this process is the graft mechanically at its weakest?

Explanation

The graft undergoes a phase of revascularization and necrosis known as the early remodeling or proliferation phase, typically around 6 to 12 weeks post-operatively. During this time, the structural properties decrease significantly, making the graft mechanically at its weakest.

Question 61

A surgeon plans to use a stainless steel screw with a titanium plate for fracture fixation. Which of the following best describes the primary mechanism of early implant failure associated with this specific metallurgical combination?

Explanation

Galvanic corrosion occurs when two dissimilar metals are placed in contact within an electrolytic medium, such as body fluid. The less noble metal (stainless steel) acts as an anode and corrodes rapidly in the presence of titanium.

Question 62

Absolute stability with interfragmentary compression is achieved in a transverse radial shaft fracture using a dynamic compression plate. Which of the following histological processes is predominantly responsible for the subsequent bone healing?

Explanation

Absolute stability without a fracture gap leads to primary bone healing, which occurs via direct Haversian remodeling. Osteoclasts at the tips of cutting cones cross the fracture site, followed immediately by osteoblasts depositing osteoid.

Question 63

A 65-year-old male presents with increasing head size and bowing of his tibiae. Radiographs show thickened cortices and a "cotton wool" appearance of the skull. Which of the following describes the primary cellular defect initiating this condition?

Explanation

Paget's disease of bone is primarily driven by hyperactive, multinucleated osteoclasts leading to chaotic and excessive bone resorption. This initial lytic phase is later followed by a disorganized, excessive osteoblastic response.

Question 64

A 14-year-old boy presents with thigh pain and a low-grade fever. Radiographs reveal a permeative diaphyseal lesion in the femur with a laminated periosteal reaction. A biopsy shows small round blue cells. Which of the following chromosomal translocations is most strongly associated with this diagnosis?

Explanation

The clinical and histologic picture describes Ewing sarcoma, classically presenting as a permeative diaphyseal lesion with small round blue cells. It is strongly associated with the t(11;22) chromosomal translocation, resulting in the EWS-FLI1 fusion protein.

Question 65

In normal articular cartilage, which zone contains the highest concentration of collagen, with fibrils specifically arranged parallel to the joint surface to resist shear forces?

Explanation

The superficial (tangential) zone of articular cartilage has the highest collagen content and the lowest proteoglycan content. The collagen fibrils in this zone are arranged parallel to the articular surface to primarily resist shear stress.

Question 66

A patient sustains a severe stretch injury to a peripheral nerve resulting in loss of axonal continuity and endoneurial tube disruption, but preservation of the perineurium and epineurium. According to Sunderland's classification, what grade is this injury?

Explanation

A Sunderland third-degree nerve injury involves disruption of the axon and endoneurium, with an intact perineurium. A second-degree injury involves only the axon (axonotmesis), while a fourth-degree injury includes perineurial disruption.

Question 67

In the pathogenesis of orthopedic implant-related infections, which of the following describes the crucial step mediating the irreversible attachment of Staphylococcus aureus to an implant surface?

Explanation

Following initial reversible attachment, S. aureus uses MSCRAMMs (like fibronectin-binding protein) to irreversibly bind to host proteins that quickly coat the implant. This crucial step precedes the production of the protective biofilm matrix.

Question 68

A 68-year-old woman is prescribed rivaroxaban for postoperative venous thromboembolism prophylaxis following a total hip arthroplasty. Which of the following represents the specific mechanism of action of this medication?

Explanation

Rivaroxaban is an oral anticoagulant that acts by directly and reversibly inhibiting Factor Xa, thereby preventing the conversion of prothrombin to thrombin. Unlike low-molecular-weight heparins, it does not require antithrombin III for its activity.

Question 69

A 4-year-old child presents with multiple recurrent fractures, blue sclerae, and early hearing loss. This condition is most commonly caused by a genetic mutation directly affecting the synthesis of which of the following structural components?

Explanation

Osteogenesis Imperfecta is most commonly an autosomal dominant disorder caused by mutations in the COL1A1 or COL1A2 genes. These mutations result in quantitative or qualitative defects in Type I collagen, the major structural protein of bone.

Question 70

In total joint arthroplasty, using highly cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) significantly reduces volumetric wear. However, this cross-linking process is known to adversely affect which of the following mechanical properties?

Explanation

While high levels of radiation cross-linking drastically improve the wear resistance of UHMWPE, it concomitantly reduces its fatigue strength, ductility, and fracture toughness. This trade-off makes the material more susceptible to fatigue-related mechanical failure, such as rim cracking.

Question 71

A 19-year-old male complains of severe, aching pain in his right proximal tibia that is worse at night and dramatically relieved by NSAIDs. Imaging shows a 1 cm radiolucent nidus surrounded by dense sclerotic bone. What is the most appropriate definitive management if medical therapy fails?

Explanation

The clinical presentation is classic for an osteoid osteoma. If medical management with NSAIDs fails or is poorly tolerated, percutaneous radiofrequency ablation is the gold standard definitive treatment due to its high success rate and low morbidity.

Question 72

A 45-year-old woman with untreated celiac disease presents with diffuse bone pain and proximal muscle weakness. Laboratory studies reveal low serum calcium, low phosphorus, elevated alkaline phosphatase, and elevated parathyroid hormone. Which of the following is the most likely diagnosis?

Explanation

Osteomalacia is characterized by a defect in bone mineralization, often due to severe Vitamin D deficiency from malabsorption. Laboratory findings typically demonstrate low calcium and phosphorus, high alkaline phosphatase, and compensatory secondary hyperparathyroidism.

Question 73

During the biological repair process of a surgically repaired flexor tendon, at which time point post-repair does the site typically reach its lowest tensile strength, rendering it most susceptible to iatrogenic rupture?

Explanation

Tendon repair strength initially drops as the inflammatory phase peaks and early degradation of damaged local tissue occurs. The repair site is mechanically weakest around 5 to 7 days post-surgery, just before the proliferative phase significantly increases collagen deposition.

Question 74

A 55-year-old male presents with a severely painful, swollen first metatarsophalangeal joint. Joint aspiration yields negatively birefringent, needle-shaped crystals under polarized light microscopy. Which of the following medications is most appropriate for the acute management of his symptoms?

Explanation

The patient has acute gouty arthritis, characterized by negatively birefringent monosodium urate crystals. Acute flares are best managed with NSAIDs (like indomethacin), colchicine, or corticosteroids; urate-lowering agents like allopurinol should not be initiated during an acute attack.

Question 75

When evaluating a clinically suspected occult scaphoid fracture with negative plain radiographs, which of the following MRI sequences is most sensitive for detecting the early bone marrow edema associated with the injury?

Explanation

STIR sequences suppress fat signal and are highly sensitive for detecting increased water content. This makes them excellent for identifying early bone marrow edema associated with occult fractures, stress responses, or early avascular necrosis.

Question 76

A 24-year-old male sustains bilateral closed femur fractures. On post-injury day 2, he acutely develops confusion, profound hypoxia, and a petechial rash over his axillae. Which of the following is the most appropriate initial management strategy?

Explanation

The classic triad of hypoxemia, neurologic compromise, and petechial rash strongly indicates Fat Embolism Syndrome (FES). The mainstay of treatment is supportive care, prioritizing the maintenance of adequate oxygenation and hemodynamics.

Question 77

During a voluntary concentric muscle contraction, calcium ions are released from the sarcoplasmic reticulum into the sarcoplasm. To initiate the sliding filament mechanism, these calcium ions must directly bind to which of the following proteins?

Explanation

Muscle contraction is initiated when calcium ions bind specifically to Troponin C on the thin filaments. This binding causes a conformational shift that moves tropomyosin away from the myosin-binding sites on actin, allowing cross-bridge cycling.

Question 78

Which of the following lower extremity amputation levels is generally associated with the highest increase in metabolic energy expenditure during ambulation compared to a healthy, non-amputee baseline?

Explanation

The metabolic energy required for ambulation increases exponentially as the level of lower extremity amputation becomes more proximal. A transfemoral amputation requires a significantly higher metabolic energy increase (approximately 60-65%) than a transtibial amputation.

Question 79

A 32-year-old female presents with progressive knee pain. Radiographs reveal an eccentric, lytic, epiphyseal lesion in the distal femur. Biopsy shows mononuclear cells and numerous multinucleated giant cells. Which targeted medical therapy is most appropriate for an unresectable lesion of this type?

Explanation

The presentation describes a Giant Cell Tumor of bone, where the neoplastic stromal cells express high levels of RANKL. Denosumab, a monoclonal antibody against RANKL, is highly effective in treating unresectable lesions by inhibiting the recruitment and activation of osteoclast-like giant cells.

Question 80

According to Wolff's Law, bone remodels in response to mechanical stress. Which of the following mechanical properties accurately describes bone's ability to exhibit different stiffness and strength depending on the speed (rate) at which a load is applied?

Explanation

Bone is a viscoelastic material, meaning its mechanical properties are highly dependent on the rate of loading. Because of this, bone exhibits greater stiffness and can absorb more energy before failing when it is loaded rapidly compared to when it is loaded slowly.

Question 81

Which of the following bone graft substitutes relies strictly on osteoinduction for its contribution to bone healing?

Explanation

DBM provides osteoinduction due to the retained bone morphogenetic proteins (BMPs). It lacks the structural integrity required for osteoconduction and contains no live cells, thus providing no osteogenesis.

Question 82

In a young, highly active patient undergoing total hip arthroplasty, which of the following bearing surface combinations demonstrates the lowest volumetric wear rate?

Explanation

Ceramic-on-ceramic bearings have the lowest volumetric wear rate among all combinations, making them appealing for young patients. However, they carry unique risks such as squeaking and catastrophic ceramic fracture.

Question 83

A hemodynamically unstable patient with an anteroposterior compression type III (APC III) pelvic ring injury is brought to the trauma bay. A pelvic binder is applied. What is the next most appropriate orthopedic intervention if the patient remains persistently hypotensive despite fluid resuscitation?

Explanation

Preperitoneal pelvic packing (PPP) or pelvic angiography are the appropriate next steps for persistent hemodynamic instability. PPP is increasingly favored for rapid control of venous bleeding, which is the most common source of pelvic hemorrhage.

Question 84

In a 12-year-old male presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following factors is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

Explanation

Endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these patients to prevent a secondary slip.

Question 85

Which of the following autografts used for anterior cruciate ligament (ACL) reconstruction possesses the highest initial ultimate tensile load compared to the native ACL?

Explanation

A quadrupled hamstring autograft has an initial ultimate tensile load exceeding 4000 N. This is the highest among common graft choices and significantly stronger than the native ACL, which has an ultimate tensile load of approximately 2160 N.

Question 86

A 30-year-old sustains a knife laceration over the volar proximal phalanx of the index finger, resulting in a complete loss of active flexion at both the proximal and distal interphalangeal joints. Which flexor tendon zone is injured?

Explanation

Zone II (historically termed no man's land) extends from the proximal A1 pulley to the insertion of the flexor digitorum superficialis. Injuries in this zone typically involve both the superficialis and profundus tendons.

Question 87

A patient presents with a traumatic spondylolisthesis of the axis (Hangman's fracture) demonstrating 4 mm of translation and 15 degrees of angulation on lateral radiographs. According to the Levine-Edwards classification, what is the injury type and optimal management?

Explanation

A Levine-Edwards Type II fracture is characterized by greater than 3 mm of translation and significant angulation. It is typically managed with careful closed reduction and halo vest immobilization.

Question 88

A 15-year-old presents with knee pain. Radiographs reveal a mixed lytic and sclerotic lesion in the distal femur with an associated Codman triangle. Prior to definitive surgical resection, what is the most critical orthopedic purpose of obtaining a whole-bone MRI of the affected femur?

Explanation

Whole-bone MRI is mandatory in the staging of primary bone sarcomas to identify skip lesions within the same long bone. The presence of a skip metastasis directly alters the required level of surgical resection or amputation.

Question 89

A 70-year-old female on long-term bisphosphonate therapy sustains a minimal-trauma subtrochanteric femur fracture. Which radiographic feature is classically associated with this specific type of atypical femur fracture?

Explanation

Atypical femur fractures related to long-term bisphosphonate use characteristically exhibit lateral cortical thickening (beaking) and a transverse or short oblique fracture line that originates on the lateral tension side.

Question 90

During the pathogenesis of a prosthetic joint infection, which phase of biofilm formation is characterized by the down-regulation of bacterial metabolic activity, rendering the organisms highly resistant to systemic antibiotics?

Explanation

During the maturation phase, bacteria deep within the biofilm decrease their metabolic rate and enter a stationary growth phase. This dormancy makes them highly resistant to most bactericidal antibiotics, which typically target actively dividing cells.

Question 91

A 45-year-old patient presents with numbness in the thumb and index finger. Which of the following physical examination findings best differentiates a C6 cervical radiculopathy from severe carpal tunnel syndrome?

Explanation

Wrist extensors are innervated by the C6 nerve root via the radial nerve, which is unaffected in carpal tunnel syndrome. Weakness in wrist extension therefore indicates a more proximal lesion, such as a C6 radiculopathy.

Question 92

A 6-year-old boy sustains a completely displaced posteromedial supracondylar humerus fracture. Which nerve is at the highest risk of injury secondary to this specific direction of fracture displacement?

Explanation

In a posteromedial displacement, the proximal fracture fragment is driven anterolaterally, impaling the lateral structures and placing the radial nerve at highest risk. Conversely, posterolateral displacement places the anterior interosseous nerve at highest risk.

Question 93

Which of the following radiographic findings is the most reliable indicator of a subtle Lisfranc ligament disruption on a weight-bearing anteroposterior view of the foot?

Explanation

Widening of more than 2 mm between the bases of the first and second metatarsals on a weight-bearing AP radiograph is highly indicative of a Lisfranc injury. The classic fleck sign represents an avulsion from the base of the second metatarsal, not the first.

Question 94

During a primary total knee arthroplasty, the surgeon uses trial components and notes that the knee is tight in flexion but well-balanced in full extension. Which of the following surgical adjustments is the most appropriate next step?

Explanation

A knee that is tight in flexion but balanced in extension requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component using an anterior referencing system effectively increases the flexion gap.

Question 95

A 25-year-old overhead athlete is diagnosed with a Type II SLAP lesion following an MRI arthrogram. According to the Snyder classification, which of the following accurately describes a Type II SLAP tear?

Explanation

A Type II SLAP tear involves the detachment of both the superior labrum and the origin of the long head of the biceps tendon from the supraglenoid tubercle. It is the most common variant requiring surgical repair in overhead athletes.

Question 96

According to Sorensen's criteria, the strict radiographic diagnosis of classic Scheuermann's kyphosis requires anterior wedging of at least 5 degrees in a minimum of how many consecutive vertebrae?

Explanation

Sorensen's diagnostic criteria for Scheuermann's disease strictly require the presence of anterior wedging of 5 degrees or more in at least three consecutive vertebral bodies on a lateral radiograph.

Question 97

Which of the following vascular structures provides the predominant blood supply to the adult femoral head?

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) provides the vast majority of the blood supply to the adult femoral head. Injury to this vessel significantly increases the risk of avascular necrosis.

Question 98

In the context of a displaced proximal humerus fracture, which of the following radiographic predictors carries the highest risk for the development of avascular necrosis of the humeral head?

Explanation

According to the Hertel criteria, a metaphyseal head extension (calcar segment) of less than 8 mm and the disruption of the medial capsular hinge are the most reliable predictors of ischemia and subsequent avascular necrosis.

Question 99

A 40-year-old female complains of severe, pinpoint pain in her long finger that worsens significantly upon exposure to cold water. Physical examination reveals exquisite point tenderness beneath the nail plate. What is the most likely diagnosis?

Explanation

A glomus tumor classically presents with the triad of severe pinpoint pain, cold hypersensitivity, and subungual point tenderness. It is a benign hamartoma originating from the neuromyoarterial glomus body.

Question 100

In a 7-year-old boy diagnosed with Legg-Calve-Perthes disease, which of the following radiographic findings is considered a head-at-risk sign indicating a poorer prognosis and potential need for surgical containment?

Explanation

Catterall's head-at-risk signs include the Gage sign, lateral calcification, lateral subluxation of the femoral head, and a horizontal physis. These signs indicate a loss of containment and a higher risk for permanent femoral head deformation.

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