Free Orthopedics Review | Dr Hutaif General Orthopedics -...

Question 1

Which of the following correctly pairs the recombinant human bone morphogenetic protein (rhBMP) with its FDA-approved indication in orthopedic trauma?

Explanation

The FDA approved rhBMP-2 (Infuse) for the treatment of acute open tibial shaft fractures treated with an intramedullary nail, as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 (OP-1) was historically approved under a Humanitarian Device Exemption for recalcitrant tibial nonunions (defined as a nonunion present for at least 9 months with no radiographic signs of healing for 3 months) and posterolateral lumbar fusion, though it is currently largely unavailable.

Question 2

According to Perren’s strain theory, what is the maximum strain environment that allows for secondary bone healing via endochondral ossification (callus formation)?

Explanation

Perren's strain theory dictates that specific tissues can only form under certain strain conditions. Primary bone healing (direct osteonal remodeling) requires absolute stability with strain less than 2%. Secondary bone healing (callus formation via endochondral ossification) requires relative stability with a strain environment between 2% and 10%. Fibrocartilage tolerates up to 10-15% strain, while granulation tissue can tolerate up to 100% strain.

Question 3

On a stress-strain curve for an orthopedic biomaterial, the total area under the curve up to the point of structural failure represents which of the following mechanical properties?

Explanation

The area under the entire stress-strain curve up to the point of failure represents the material's 'toughness,' which is the total amount of energy a material can absorb before it breaks. 'Stiffness' (Young's modulus) is the slope of the linear elastic portion. 'Yield strength' is the point where plastic deformation begins. 'Ductility' is the amount of plastic strain a material can sustain before failure.

Question 4

A 25-year-old male presents with a slow-growing, painful mass near his knee joint. Biopsy reveals a biphasic tumor with both epithelial and spindle cell components. Which of the following chromosomal translocations is diagnostic for this malignancy?

Explanation

The clinical and histological presentation (biphasic components near a joint) is classic for Synovial Sarcoma. The pathognomonic chromosomal translocation for synovial sarcoma is t(X;18), which creates the SYT-SSX fusion gene. t(11;22) is found in Ewing sarcoma. t(12;16) is seen in myxoid liposarcoma. t(2;13) is characteristic of alveolar rhabdomyosarcoma. t(12;22) is seen in clear cell sarcoma.

Question 5

A 4-month-old infant with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the parents note that the infant has stopped kicking with the affected leg. On examination, the hip is found to be in excessive flexion. Which of the following physical exam findings is most likely to be present?

Explanation

A known complication of treating DDH with a Pavlik harness in excessive hip flexion is femoral nerve palsy. This manifests as a loss of quadriceps function, leading to the inability to actively extend the knee. The treatment is temporary removal of the harness or adjustment to decrease the degree of hip flexion. Excessive abduction, conversely, increases the risk of avascular necrosis (AVN) of the femoral head.

Question 6

In the cascade of aseptic loosening following a total hip arthroplasty, the primary biological response to ultra-high-molecular-weight polyethylene (UHMWPE) wear debris is initiated by which of the following cell types?

Explanation

The primary effector cells in the biological cascade of particle-induced osteolysis (aseptic loosening) are tissue macrophages. Macrophages phagocytose particulate UHMWPE wear debris (especially particles 0.1 to 1.0 micrometers in size). This triggers the release of pro-inflammatory cytokines such as TNF-alpha, IL-1, and IL-6, which subsequently upregulate RANKL expression, leading to osteoclast activation and bone resorption.

Question 7

A 32-year-old male is admitted after a high-energy tibial plateau fracture. He complains of increasing leg pain that is out of proportion to his injury. His blood pressure is 130/80 mmHg. Direct compartment pressure measurement of the anterior compartment reveals a pressure of 45 mmHg. What is the calculated Delta P, and what is the next appropriate step in management?

Explanation

Delta P is defined as the diastolic blood pressure minus the intracompartmental pressure (Delta P = Diastolic BP - Compartment Pressure). In this patient, 80 mmHg - 45 mmHg = 35 mmHg. The generally accepted threshold for surgical intervention (fasciotomy) for acute compartment syndrome is a Delta P of 30 mmHg or less. Since the Delta P is >30 mmHg, close clinical observation and serial neurovascular checks are indicated.

Question 8

Which of the following layers of articular cartilage contains the highest concentration of water and has collagen fibers oriented parallel to the joint surface?

Explanation

Articular cartilage is divided into distinct zones. The superficial (tangential) zone has the highest water content (approx. 80%), the lowest proteoglycan concentration, and Type II collagen fibers that run parallel to the articular surface to resist shear forces. The deep zone has the lowest water content, the highest proteoglycan content, and collagen fibers oriented perpendicular to the joint surface to resist compressive loads.

Question 9

A 70-year-old male presents with isolated elevation of serum alkaline phosphatase. Calcium and phosphorus levels are normal. Radiographs of the pelvis reveal coarsened trabeculae and cortical thickening. A bone biopsy would most likely show large, multinucleated osteoclasts containing viral inclusion bodies. Which virus is most commonly implicated in the pathogenesis of this disease?

Explanation

The clinical presentation is classic for Paget's disease of bone (osteitis deformans), characterized by normal serum calcium and phosphorus with an elevated alkaline phosphatase. The primary cellular defect is in the osteoclast. Paramyxoviruses (such as Respiratory Syncytial Virus and measles virus) have been implicated in its pathogenesis, supported by the presence of paramyxovirus-like nucleocapsid inclusion bodies within the enlarged, multinucleated osteoclasts.

Question 10

Which of the following is the primary source of nutrition for flexor tendons within Zone II of the hand (the 'no man's land')?

Explanation

In Zone II of the hand, flexor tendon nutrition is biphasic, relying on both extrinsic and intrinsic sources. However, synovial fluid diffusion (extrinsic) is the primary and most important source of nutrition for the flexor tendons in this avascular zone. The intrinsic vascular supply comes from the vincula, but diffusion via synovial fluid is predominantly responsible for tendon healing and maintenance, which is enhanced by early active motion protocols.

Question 11

During the physical examination of a patient's knee, the pivot-shift test is utilized to assess rotatory instability. Which specific bundle of the anterior cruciate ligament (ACL) is primarily responsible for resisting internal rotation and is assessed during this maneuver?

Explanation

The ACL is composed of two primary bundles: the anteromedial (AM) and posterolateral (PL) bundles. The AM bundle is tight in flexion and primarily controls anterior-posterior translation. The PL bundle is tight in extension and primarily controls rotatory stability (resists internal rotation). The pivot-shift test examines rotatory instability near full extension, thus specifically testing the integrity of the PL bundle.

Question 12

A surgeon is performing a total knee arthroplasty (TKA). After making the initial bone cuts and inserting trial components, she notes that the knee is tight in extension (with a lack of full extension) but perfectly balanced in 90 degrees of flexion. What is the most appropriate next step to balance the knee?

Explanation

In TKA gap balancing, if the extension gap is tight (knee lacks full extension) but the flexion gap is well-balanced, the appropriate step is to resect more bone from the distal femur. Distal femoral resection increases the extension gap without affecting the flexion gap. Resecting more proximal tibia would erroneously increase both the flexion and extension gaps. Downsizing the femoral component increases the flexion gap.

Question 13

A 12-year-old girl with a history of severe hypothyroidism presents with a limp and left hip pain. Radiographs reveal a slipped capital femoral epiphysis (SCFE) of the left hip. What is the most appropriate definitive management?

Explanation

While unilateral SCFE is typically treated with single-screw in situ pinning, prophylactic pinning of the contralateral asymptomatic hip is strongly recommended in patients with specific risk factors. These high-risk factors include underlying endocrine disorders (such as hypothyroidism, panhypopituitarism), renal osteodystrophy, and a history of previous pelvic radiation. Given her severe hypothyroidism, prophylactic pinning of the right hip is indicated.

Question 14

Denosumab has revolutionized the medical management of unresectable or recurrent Giant Cell Tumor (GCT) of bone. What is the specific cellular target of denosumab in the microenvironment of a GCT?

Explanation

Giant cell tumor of bone consists of neoplastic mononuclear stromal cells and reactive multinucleated giant cells. The true neoplastic cells are the mononuclear stromal cells, which highly express RANK Ligand (RANKL). RANKL binds to the RANK receptor on the surface of osteoclast precursors, causing them to fuse into reactive multinucleated giant cells. Denosumab is a monoclonal antibody that binds to RANKL, preventing it from interacting with RANK, thereby halting giant cell formation and bone resorption.

Question 15

During fracture fixation, combining a 316L stainless steel plate with titanium screws in an electrolytic physiological environment can lead to implant failure. Which biomechanical phenomenon best describes this process?

Explanation

Galvanic corrosion occurs when two dissimilar metals with different anodic indices (electronegativities) are placed in direct physical contact within an electrically conductive fluid (such as blood or interstitial body fluid). In the case of stainless steel and titanium, the less noble metal (stainless steel) acts as the anode and undergoes accelerated corrosion, while the titanium acts as the cathode. Fretting corrosion is caused by micromotion between components, while crevice corrosion occurs in shielded areas with oxygen depletion.

Question 16

A 45-year-old female is prescribed an antibiotic for a urinary tract infection. Two weeks later, she sustains an acute, spontaneous Achilles tendon rupture while walking up a flight of stairs. Which of the following classes of antibiotics did she most likely receive, and what is its primary mechanism of inducing tendinopathy?

Explanation

Fluoroquinolones (such as ciprofloxacin or levofloxacin) carry a black box warning for tendinopathy and spontaneous tendon rupture, most commonly affecting the Achilles tendon. The pathophysiological mechanism involves the upregulation of matrix metalloproteinases (MMPs), which leads to excessive degradation of Type I collagen, alongside a direct cytotoxic effect on tenocytes and decreased synthesis of new collagen.

Question 17

In evaluating a patient with a traumatic nerve injury to the forearm, the electrodiagnostic study reveals innervation of the intrinsic hand muscles (such as the first dorsal interosseous) despite a complete transection of the ulnar nerve at the elbow. Which of the following anatomical variants is responsible for this finding?

Explanation

The Martin-Gruber anastomosis is a common anatomical variant (present in about 15-30% of the population) involving a motor nerve connection from the median nerve (or its anterior interosseous branch) to the ulnar nerve in the proximal forearm. It carries motor fibers that ultimately supply the intrinsic muscles of the hand (typically ulnar-innervated). The Riche-Cannieu anastomosis occurs in the palm (deep ulnar branch to recurrent median branch). Marinacci is the reverse Martin-Gruber (ulnar to median in forearm). Berrettini is a sensory communication in the palm.

Question 18

Which of the following prophylactic systemic antibiotics exerts its bactericidal effect by binding directly to the D-alanyl-D-alanine terminus of cell wall precursor units?

Explanation

Vancomycin is a glycopeptide antibiotic that inhibits cell wall synthesis by binding tightly to the D-alanyl-D-alanine terminus of peptidoglycan precursors, preventing their cross-linking. Cefazolin (a beta-lactam) inhibits cross-linking by binding to penicillin-binding proteins (PBPs). Gentamicin binds the 30S ribosomal subunit. Clindamycin binds the 50S ribosomal subunit. Rifampin inhibits DNA-dependent RNA polymerase.

Question 19

A 55-year-old male with severe spinal stenosis complains of progressive leg pain, heaviness, and weakness that worsens with walking. To differentiate neurogenic claudication from vascular claudication, a bicycle test (van Gelderen test) is performed. Which of the following responses is characteristic of neurogenic claudication?

Explanation

The bicycle test (van Gelderen test) is used to differentiate neurogenic from vascular claudication. In neurogenic claudication (due to lumbar spinal stenosis), symptoms are exacerbated by spinal extension (which narrows the spinal canal and neuroforamina) and relieved by spinal flexion. Therefore, cycling while leaning forward (flexion) is well tolerated, whereas cycling sitting straight up (extension) reproduces the pain. Vascular claudication is dependent on muscle work (oxygen demand) regardless of spinal posture.

Question 20

Gustilo-Anderson classification is crucial for decision-making in open fractures. A 30-year-old male sustains an open midshaft tibia fracture with a 12 cm laceration, extensive periosteal stripping, and exposed diaphyseal bone. Following aggressive debridement, the plastic surgeon determines that the wound cannot be closed primarily and will require a rotational gastrocnemius flap. Intravenous antibiotics are initiated. According to Gustilo-Anderson, how is this fracture classified?

Explanation

The Gustilo-Anderson classification categorizes open fractures based on wound size, contamination, and soft-tissue injury. A Type IIIA fracture involves extensive soft-tissue stripping but maintains adequate soft-tissue coverage of the fractured bone (primary closure or skin grafting is possible). A Type IIIB fracture involves extensive soft-tissue injury with periosteal stripping and bone exposure, requiring a local or free soft-tissue flap for coverage. Type IIIC involves an arterial injury requiring repair for limb salvage.

Question 21

A 19-year-old male presents with dull, aching thigh pain that is distinctly worse at night and reliably relieved by ibuprofen. Imaging reveals a 1.2 cm radiolucent nidus with surrounding sclerosis in the proximal femoral diaphysis. What is the primary molecular mechanism responsible for this patient's pain?

Explanation

Osteoid osteomas classically present with night pain relieved by NSAIDs. This is due to the high concentration of cyclooxygenase (COX) enzymes within the nidus, which produce copious amounts of Prostaglandin E2 (PGE2). PGE2 lowers the threshold of local nociceptors. NSAIDs block COX, halting PGE2 production and rapidly relieving the pain.

Question 22

An adult male is brought to the trauma bay following a high-speed motorcycle collision. He is hemodynamically unstable with a mechanically unstable anteroposterior compression (APC-III) pelvic ring injury. A commercial pelvic binder is applied. To optimize mechanical closure of the pelvic volume and minimize the risk of iatrogenic complications, the binder should be centered strictly over which anatomic landmarks?

Explanation

Pelvic binders must be centered directly over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume, particularly in "open book" (APC) injuries. Placement over the iliac crests or ASIS is anatomically too high and can paradoxically widen the pelvic floor, exacerbating bleeding and instability.

Question 23

A 55-year-old female undergoes knee arthroscopy for a complete radial tear at the bony attachment of the posterior horn of the medial meniscus (root tear). If left untreated, this injury alters the biomechanics of the knee compartment in a manner most equivalent to which of the following?

Explanation

A medial meniscus posterior root tear results in complete loss of meniscal hoop stresses, allowing the meniscus to extrude peripherally under axial load. Biomechanical studies demonstrate that a complete root tear drastically increases peak articular contact pressures, functionally equating to the biomechanical state of a total meniscectomy.

Question 24

A 12-year-old obese male is diagnosed with a severe slipped capital femoral epiphysis (SCFE) of the left hip. Contralateral prophylactic pinning of the asymptomatic right hip is most strongly indicated if the patient has a history of which of the following conditions?

Explanation

Prophylactic pinning of the contralateral hip in SCFE is debated for idiopathic cases but is highly recommended for patients with endocrine or metabolic disorders, as they have a significantly higher rate of bilateral involvement (approaching 100% in some cohorts). Hypothyroidism, renal osteodystrophy, and panhypopituitarism are major indications for prophylactic fixation.

Question 25

A 35-year-old carpenter presents with a swollen, painful index finger 3 days after a puncture wound. Which of the following Kanavel's signs is typically the earliest and most reliable indicator of acute suppurative flexor tenosynovitis?

Explanation

Kanavel's four cardinal signs of flexor tenosynovitis are: 1) flexed resting posture, 2) fusiform swelling (sausage digit), 3) tenderness along the flexor sheath, and 4) pain with passive extension. Exquisite pain with passive extension of the affected digit is widely considered the earliest, most sensitive, and most reliable clinical sign.

Question 26

A 24-year-old football player sustains an axial load to a plantarflexed foot. Weight-bearing radiographs show widening of the interval between the first and second metatarsal bases. A "fleck sign" is noted. This osseous avulsion typically originates from which of the following structures?

Explanation

The Lisfranc ligament is a stout interosseous ligament connecting the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. The "fleck sign" represents a bony avulsion of this ligament, which most commonly avulses from the base of the second metatarsal into the intermetatarsal space.

Question 27

A traumatic spondylolisthesis of the axis (Hangman's fracture) most commonly occurs via which of the following injury mechanisms?

Explanation

A Hangman's fracture (traumatic spondylolisthesis of C2 with bilateral pars interarticularis fractures) classically occurs due to a hyperextension and axial loading mechanism. This is often seen in motor vehicle accidents where an unbelted victim's chin strikes the dashboard.

Question 28

In the biomechanical evaluation of tendons and ligaments, which of the following best defines the viscoelastic phenomenon of "creep"?

Explanation

Creep is a viscoelastic property defined as the progressive increase in strain (deformation) over time when a material is subjected to a constant stress (load). Option A describes stress relaxation. Option C describes hysteresis. Option D describes strain-rate dependency. Option E describes fatigue failure.

Question 29

The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is utilized to stratify the risk of necrotizing soft tissue infection. Which of the following laboratory parameters is NOT a component of the LRINEC score?

Explanation

The LRINEC score consists of six variables: CRP, WBC count, Hemoglobin, Serum sodium, Serum creatinine, and Serum glucose. Serum potassium is not a part of the scoring system. A score of 6 or greater is highly suspicious for necrotizing fasciitis.

Question 30

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction during fracture healing. Following the binding of a BMP ligand to its cell surface serine/threonine kinase receptor, the intracellular signal is primarily propagated to the nucleus via which family of proteins?

Explanation

BMPs act through transmembrane serine/threonine kinase receptors. Upon activation, these receptors phosphorylate intracellular Smad proteins (specifically R-Smads 1, 5, and 8), which then complex with Co-Smad 4 and translocate to the nucleus to regulate the transcription of osteogenic genes like Runx2.

Question 31

According to the Ponseti method for the conservative management of congenital talipes equinovarus (clubfoot), which component of the deformity must be addressed first during serial casting?

Explanation

The Ponseti method corrects the deformities of a clubfoot in a specific sequence, remembered by the acronym CAVE: Cavus, Adductus, Varus, Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot. Equinus is corrected last.

Question 32

Delamination of ultra-high-molecular-weight polyethylene (UHMWPE) components in total knee arthroplasty is predominantly a consequence of which type of wear mechanism?

Explanation

Fatigue wear occurs due to cyclic loading that generates maximum shear stresses slightly below the articulating surface. Over time, these subsurface stresses cause microcracks that propagate and coalesce, eventually leading to gross delamination and pitting of the polyethylene component. This is common in TKA due to non-conforming surface contact stresses.

Question 33

What is the initiating pathophysiological event in the development of acute compartment syndrome?

Explanation

The cascade of acute compartment syndrome begins when an increase in intracompartmental pressure overcomes the low-pressure venous system. This obstruction of venous outflow leads to venous pooling, increased capillary hydrostatic pressure, and transudation of fluid. This creates a vicious cycle of increasing tissue pressure that eventually compromises capillary perfusion and arterial inflow.

Question 34

A 28-year-old male is admitted after a severe cervical spine fracture. He is hypotensive, bradycardic, and warm to the touch. This physiologic state is best described as:

Explanation

Neurogenic shock is characterized by hypotension, bradycardia, and warm extremities. It is a distributive shock caused by the loss of sympathetic tone following a high spinal cord injury (typically above T6), leaving the parasympathetic tone unopposed. Spinal shock refers to a temporary physiologic areflexia and flaccid paralysis below the level of injury.

Question 35

Multiple myeloma is frequently associated with severe osteolytic lesions that classically lack reactive bone formation. Which of the following molecules, secreted by myeloma cells, is primarily responsible for inhibiting osteoblast differentiation and preventing bone repair in these patients?

Explanation

Myeloma cells secrete Dickkopf-1 (DKK-1), which binds to LRP5/6 and competitively inhibits the Wnt/beta-catenin signaling pathway. This profoundly suppresses osteoblast differentiation and activity, explaining why myeloma lesions are purely osteolytic and lack a sclerotic rim on radiographs.

Question 36

A 22-year-old collegiate baseball pitcher presents with posterior shoulder pain during the late cocking phase of throwing. Magnetic resonance imaging reveals a partial articular-sided tear of the supraspinatus and posterosuperior labral fraying. These findings are the hallmark of which of the following conditions?

Explanation

Internal impingement occurs in overhead throwing athletes during the late cocking phase (abduction and maximal external rotation). The articular surface of the supraspinatus/infraspinatus footprint impinges physically against the posterosuperior glenoid and labrum, leading to articular-sided cuff tears and labral pathology.

Question 37

A 58-year-old poorly controlled diabetic patient presents with a red, hot, swollen foot without systemic signs of infection. Radiographs reveal prominent periarticular fragmentation, joint subluxation, and bony debris at the midfoot. According to the Eichenholtz classification of Charcot arthropathy, this patient is in which stage?

Explanation

Eichenholtz Stage I (Development/Fragmentation) is characterized clinically by a red, hot, swollen foot and radiographically by osteopenia, joint subluxation, bony fragmentation, and debris. Stage II (Coalescence) shows decreased swelling and radiographic absorption of debris. Stage III (Reconstruction) shows consolidated remodeling. Stage 0 features erythema/swelling but normal radiographs.

Question 38

During a nerve conduction study for suspected carpal tunnel syndrome, the neurologist identifies a Martin-Gruber anastomosis. This anatomic variant involves a neural communication in the forearm transferring fibers from the:

Explanation

A Martin-Gruber anastomosis is an anomalous neural connection in the forearm where motor fibers cross from the median nerve (often via the anterior interosseous nerve branch) to the ulnar nerve. This can result in intrinsic hand muscles being innervated by fibers that originated from the median nerve, complicating the clinical evaluation of nerve injuries.

Question 39

A 30-year-old male sustains a vertically oriented (Pauwels Type III) femoral neck fracture. To maximize biomechanical stability and resist shear forces, which of the following internal fixation constructs is most appropriate?

Explanation

In young adults with high-shear, vertically oriented femoral neck fractures (Pauwels Type III), biomechanical studies have consistently demonstrated that a fixed-angle device, such as a sliding hip screw (dynamic hip screw, DHS) combined with a derotation screw, provides superior construct stiffness and failure load compared to parallel cannulated screws.

Question 40

Demineralized bone matrix (DBM) is widely utilized in spinal fusion surgery. Based on its biologic properties, DBM is best classified as possessing which of the following combinations?

Explanation

Demineralized bone matrix (DBM) contains a collagen scaffold (providing osteoconductivity) and exposes naturally occurring bone morphogenetic proteins (BMPs) (providing osteoinductivity). However, because the processing kills all viable cells, DBM lacks living bone-forming cells and is therefore NOT osteogenic.

Question 41

A viscoelastic material is subjected to a constant load over a prolonged period, resulting in a progressive increase in deformation. Which biomechanical property does this describe?

Explanation

Creep is defined as the progressive deformation of a viscoelastic material when subjected to a constant load. Stress relaxation, conversely, is the decrease in stress over time when a material is held at a constant deformation.

Question 42

A 12-year-old boy presents with an aggressive diaphyseal lesion in his femur with an 'onion skin' periosteal reaction. A biopsy is planned. Which specific chromosomal translocation is most characteristically associated with this pathology?

Explanation

Ewing sarcoma is classically associated with the t(11;22)(q24;q12) translocation, resulting in the EWS-FLI1 fusion protein. Synovial sarcoma is associated with t(X;18), and alveolar rhabdomyosarcoma with t(2;13).

Question 43

In total joint arthroplasty, which sterilization method for ultra-high-molecular-weight polyethylene (UHMWPE) is most closely associated with in vivo oxidation and accelerated wear due to the creation of free radicals?

Explanation

Gamma irradiation in air causes chain scission and the formation of free radicals that react with oxygen over time, leading to oxidation, embrittlement, and accelerated wear. Modern cross-linking processes mitigate this issue by melting or annealing.

Question 44

A 4-year-old child presents with a limp, fever, and refusal to bear weight on the right leg. According to the Kocher criteria, which of the following is NOT one of the four primary predictors for differentiating septic arthritis from transient synovitis?

Explanation

The four original Kocher criteria are non-weight-bearing, ESR > 40, Fever > 38.5 C (101.3 F), and WBC > 12,000. While CRP is highly sensitive and utilized in modified criteria, it was not one of the original four parameters.

Question 45

A 65-year-old male presents with bilateral leg pain that worsens with walking. Which finding on history or examination most reliably differentiates neurogenic claudication from vascular claudication?

Explanation

Neurogenic claudication typically improves with lumbar flexion, which increases the cross-sectional area of the spinal canal. Vascular claudication improves simply with rest (standing still) and is exacerbated by any exertion, including stationary cycling.

Question 46

Which of the following laboratory profiles (Calcium, Phosphate, Alkaline Phosphatase, PTH) is most indicative of osteomalacia rather than osteoporosis?

Explanation

Osteomalacia is characterized by defective mineralization, often due to Vitamin D deficiency, resulting in low/normal Calcium, low Phosphate, elevated Alkaline Phosphatase, and secondary hyperparathyroidism. Osteoporosis typically has normal laboratory values.

Question 47

When evaluating a patient for acute compartment syndrome of the leg following a tibial fracture, which pressure measurement best correlates with the need for emergent fasciotomy?

Explanation

A Delta P (diastolic blood pressure minus compartment pressure) of less than 30 mmHg is the most reliable threshold for diagnosing acute compartment syndrome. Absolute pressures can be misleading, especially in hypotensive patients.

Question 48

A solid intramedullary nail has a radius of 'r'. If a new solid nail is manufactured with a radius of '2r', how much will its bending rigidity increase?

Explanation

The bending rigidity (area moment of inertia) of a solid cylinder is proportional to the radius raised to the fourth power (r^4). Therefore, doubling the radius (2r)^4 results in a 16-fold increase in bending rigidity.

Question 49

A patient sustains a laceration to the volar aspect of the hand, resulting in an inability to flex both the PIP and DIP joints of the index finger. The injury is located between the distal palmar crease and the middle of the middle phalanx. What zone of flexor tendon injury is this?

Explanation

Zone II, often called 'no man's land', extends from the A1 pulley (distal palmar crease) to the insertion of the FDS on the middle phalanx. It contains both the FDS and FDP tendons within a tight fibro-osseous sheath.

Question 50

Which zone of articular cartilage contains the highest concentration of proteoglycans and the lowest concentration of water?

Explanation

The deep (radial) zone of articular cartilage has the highest concentration of proteoglycans, the lowest water content, and collagen fibers oriented perpendicular to the joint surface to resist compressive loads. The superficial zone has the highest water content.

Question 51

In an anterior-posterior compression (APC) type III pelvic ring injury, which of the following ligaments is disrupted, causing severe rotational and vertical instability?

Explanation

An APC III injury involves complete disruption of the symphysis pubis along with the anterior and posterior sacroiliac, sacrotuberous, and sacrospinous ligaments. This leads to complete pelvic dissociation and profound hemodynamic instability.

Question 52

A 13-year-old obese boy presents with knee pain and an antalgic gait. Examination reveals obligatory external rotation of the hip with passive flexion. What is the most appropriate initial treatment if radiographs confirm a stable Slipped Capital Femoral Epiphysis (SCFE)?

Explanation

The standard of care for a stable SCFE is in situ pinning with a single, partially threaded cannulated screw placed centrally in the epiphysis. Closed reduction is contraindicated due to the high risk of disrupting the blood supply and causing osteonecrosis.

Question 53

A 19-year-old male complains of severe night pain in his proximal tibia that is dramatically relieved by NSAIDs. Radiographs show a small radiolucent nidus surrounded by dense sclerotic bone. What is the primary mechanism by which this lesion causes pain?

Explanation

Osteoid osteomas produce high levels of prostaglandins (specifically PGE2) which cause severe, localized pain, characteristically worse at night. This is why nonsteroidal anti-inflammatory drugs (NSAIDs) provide dramatic symptomatic relief.

Question 54

When a titanium alloy femoral stem is coupled with a cobalt-chromium modular femoral head in total hip arthroplasty, what type of corrosion is most likely to occur at the trunnion interface due to the difference in electrochemical potential?

Explanation

Galvanic corrosion occurs when two dissimilar metals are in physical contact within an electrolytic solution like body fluid. The less noble metal acts as an anode and corrodes, often compounded by mechanical fretting at the trunnion.

Question 55

During the pathogenesis of periprosthetic joint infection, bacteria form a biofilm. Which phase of biofilm formation is characterized by the irreversible attachment of bacteria to the implant surface and production of an extracellular polymeric substance (EPS) matrix?

Explanation

The sessile (maturation) phase involves irreversible attachment, phenotypic changes, and the secretion of an EPS matrix that protects the bacteria from antibiotics and the host immune system. The planktonic phase is the free-floating state.

Question 56

A patient presents with inability to actively extend the wrist and digits, and loss of sensation over the dorsal first web space following a mid-shaft humerus fracture. Which cord of the brachial plexus gives rise to the nerve responsible for these deficits?

Explanation

The patient has a radial nerve palsy, which commonly complicates mid-shaft humerus fractures (Holstein-Lewis type). The radial nerve is a terminal branch of the posterior cord of the brachial plexus.

Question 57

Which signaling pathway is essential for the differentiation of mesenchymal stem cells into osteoblasts, and is classically inhibited by sclerostin?

Explanation

The Wnt/beta-catenin pathway promotes osteoblast differentiation and bone formation. Sclerostin, produced by osteocytes, binds to LRP5/6 receptors to inhibit Wnt signaling, making it a target for osteoporosis treatments like romosozumab.

Question 58

In the Eichenholtz classification of Charcot arthropathy, which stage is characterized clinically by a warm, swollen, erythematous foot, and radiographically by periarticular fragmentation, debris, and subluxation?

Explanation

Eichenholtz Stage I is the developmental or fragmentation phase, marked by acute inflammation and radiographic evidence of bone debris, fragmentation, and joint subluxation. Stage II involves coalescence, while Stage III represents reconstruction and consolidation.

Question 59

During knee flexion, which bundle of the Anterior Cruciate Ligament (ACL) is the primary restraint to anterior tibial translation?

Explanation

The anteromedial (AM) bundle of the ACL is tight in flexion and acts as the primary restraint to anterior tibial translation at 90 degrees. The posterolateral (PL) bundle is tight in extension and provides rotational stability.

Question 60

According to the Gustilo-Anderson classification, an open tibial shaft fracture with a 6 cm laceration, extensive periosteal stripping, and adequate soft-tissue coverage without the need for a flap is classified as:

Explanation

A Type IIIA fracture is defined as an open fracture with extensive soft tissue damage and periosteal stripping, but adequate soft tissue coverage remains. Type IIIB requires a flap for coverage, and Type IIIC involves an arterial injury requiring repair.

Question 61

Which of the following wear mechanisms is primarily responsible for the generation of polyethylene debris in total hip arthroplasty, ultimately leading to osteolysis?

Explanation

Adhesive wear occurs when two surfaces slide against each other, forming microscopic welds that subsequently break off to form particulate debris. This is the primary mode of wear generating polyethylene particles in THA, leading to macrophage activation and osteolysis.

Question 62

A 32-year-old male sustains a closed tibial shaft fracture. Which of the following is the most sensitive early clinical indicator of developing acute compartment syndrome?

Explanation

Pain out of proportion to the injury and exacerbated by passive stretch of the muscles in the involved compartment is the most reliable and earliest clinical sign of acute compartment syndrome. Pulselessness and paresis are late and irreversible signs.

Question 63

A 13-year-old obese boy presents with progressive left knee pain and an antalgic gait. Examination reveals obligatory external rotation of the hip during passive flexion. Which of the following is the most appropriate initial management?

Explanation

The clinical presentation is classic for a Slipped Capital Femoral Epiphysis (SCFE). The standard of care is immediate non-weight bearing to prevent further slippage, followed by in situ percutaneous screw fixation.

Question 64

A 28-year-old female presents with knee pain. Radiographs reveal an eccentric, lytic, epiphyseal-metaphyseal lesion in the distal femur without a sclerotic border. Biopsy shows multinucleated giant cells in a stroma of mononuclear cells. Denosumab therapy is considered. What is the mechanism of action of Denosumab?

Explanation

Denosumab is a monoclonal antibody that binds to RANKL, preventing it from activating RANK on the surface of osteoclasts and their precursors. This is highly effective in Giant Cell Tumor of bone, which is driven by RANKL-expressing stromal cells.

Question 65

A 65-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Six weeks postoperatively, she sustains a posterior dislocation. Which of the following acetabular cup orientations most significantly increases the risk of posterior dislocation?

Explanation

Poster dislocation in THA is strongly associated with acetabular retroversion (decreased anteversion) and inadequate abduction. The safe zone generally targets 15 (+/- 10) degrees of anteversion and 40 (+/- 10) degrees of abduction.

Question 66

A 45-year-old pregnant woman in her third trimester presents with severe numbness and tingling in the radial three and a half digits of her right hand, awakening her at night. Nerve conduction studies confirm severe carpal tunnel syndrome. What is the most appropriate initial management?

Explanation

Pregnancy-induced carpal tunnel syndrome typically resolves postpartum. Nocturnal splinting is the safest and most appropriate initial management, with surgical release reserved for refractory cases or signs of severe motor denervation lasting after delivery.

Question 67

According to the modified Gustilo-Anderson classification, a 4 cm laceration over a tibia fracture with extensive periosteal stripping requiring a local rotational flap for coverage is classified as:

Explanation

A Gustilo-Anderson Type IIIB fracture is defined by extensive soft tissue injury, periosteal stripping, and bone exposure requiring a local or free flap for soft tissue coverage. Type IIIA has adequate periosteal coverage despite extensive lacerations.

Question 68

A 40-year-old weekend warrior presents with acute heel pain and weakness in plantarflexion after playing basketball. The Thompson test is positive. Which of the following describes the most common location of this pathology?

Explanation

Achilles tendon ruptures most commonly occur in the watershed area, which is located 2 to 6 cm proximal to the calcaneal insertion. This region has a relatively precarious blood supply, making it susceptible to degeneration and rupture.

Question 69

Which of the following bone grafting materials possesses osteogenic, osteoinductive, and osteoconductive properties?

Explanation

Autograft (such as from the iliac crest) is the only graft material that provides all three properties: osteoconduction (scaffold), osteoinduction (growth factors), and osteogenesis (live cells). Allografts and DBM lack live cells, providing no osteogenesis.

Question 70

A 55-year-old male presents with acute onset of severe lower back pain, bilateral sciatica, saddle anesthesia, and urinary retention with overflow incontinence. MRI reveals a massive L4-L5 central disc herniation. What is the maximum recommended timeframe for surgical decompression to optimize neurological recovery?

Explanation

Cauda equina syndrome is a surgical emergency. Decompression should ideally be performed within 24 to 48 hours of symptom onset to maximize the chances of full neurological recovery, particularly for bladder and bowel function.

Question 71

During a pivot-shift test for an anterior cruciate ligament (ACL) deficient knee, the tibia reduces at approximately 20-30 degrees of flexion. Which structure is primarily responsible for generating the force that reduces the tibia?

Explanation

The pivot-shift test demonstrates a subluxated tibia in extension that reduces in flexion. The iliotibial band (ITB) changes from an extensor to a flexor at 20-30 degrees of flexion, creating a posterior force vector that reduces the anteriorly subluxated lateral tibial plateau.

Question 72

A 4-month-old female infant is diagnosed with developmental dysplasia of the hip (DDH) that is reducible. A Pavlik harness is prescribed. Which of the following represents the most serious complication of excessive hyperflexion of the hips in the harness?

Explanation

Excessive hyperflexion in a Pavlik harness can lead to femoral nerve palsy. Avascular necrosis is typically a complication of excessive rigid abduction, while femoral nerve palsy is the classic risk of excessive flexion.

Question 73

A hypotensive trauma patient with a mechanically unstable anterior-posterior compression (APC-III) pelvic ring injury is resuscitated and a pelvic binder is applied. To be biomechanically effective and safely reduce pelvic volume, the binder must be centered over which anatomical landmarks?

Explanation

To effectively reduce pelvic volume and control venous bleeding in an open-book pelvic fracture, a pelvic binder or sheet must be centered at the level of the greater trochanters. Placing it over the iliac crests is less effective and can paradoxically open the pelvis further.

Question 74

A 70-year-old male presents with a painful total knee arthroplasty 2 years after index surgery. Synovial fluid aspiration reveals a WBC count of 45,000 cells/uL with 92% neutrophils. He is hemodynamically stable with well-fixed implants on radiographs. Which is the most appropriate definitive management?

Explanation

Chronic periprosthetic joint infections (presenting >4 weeks postoperatively or >3 weeks from symptom onset) with well-fixed components are definitively managed with a two-stage revision arthroplasty. Open irrigation and debridement with poly exchange is reserved for acute infections.

Question 75

A 25-year-old soccer player sustains a bucket-handle tear of the medial meniscus in the "red-red" zone. He undergoes an inside-out meniscal repair. Which nerve is at greatest risk of injury during the passage of sutures for this specific repair?

Explanation

The saphenous nerve is at the greatest risk of injury during an inside-out repair of the medial meniscus, particularly the infrapatellar branch. The common peroneal nerve is at risk during lateral meniscus repairs.

Question 76

A 15-year-old boy presents with progressive distal thigh pain. Imaging shows a sunburst periosteal reaction and Codman's triangle in the distal femur. A biopsy confirms high-grade intramedullary osteosarcoma. What is the standard treatment protocol?

Explanation

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

Question 77

A 65-year-old woman sustains a volar-angulated extra-articular distal radius fracture (Smith's fracture). Following closed reduction and volar locked plating, the patient develops an inability to flex the interphalangeal joint of her thumb. Which tendon is most likely ruptured?

Explanation

The Flexor Pollicis Longus (FPL) tendon is at high risk for irritation and rupture following volar plate fixation of distal radius fractures. This occurs especially if the plate is positioned too distally, projecting beyond the watershed line.

Question 78

A 22-year-old football player presents with midfoot pain after his foot was axially loaded while plantarflexed. Weight-bearing radiographs show widening of the interval between the first and second metatarsal bases. The Lisfranc ligament connects which two osseous structures?

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 provides critical stability to the midfoot arch.

Question 79

Following rigid open reduction and internal fixation (ORIF) of a transverse radial shaft fracture with absolute stability, what is the primary mode of bone healing?

Explanation

Rigid internal fixation with absolute stability (strain < 2%) bypasses callus formation, leading to primary (direct) bone healing. This process relies on osteoclastic cutting cones crossing the fracture site followed by osteoblast-mediated bone deposition.

Question 80

When comparing titanium alloys (Ti-6Al-4V) to 316L stainless steel for orthopedic implants, which of the following is a primary biomechanical advantage of the titanium alloy?

Explanation

Titanium alloys have a lower modulus of elasticity than stainless steel, making them biomechanically closer to cortical bone. This reduces stress shielding and subsequent bone resorption around the implant.

Question 81

A 32-year-old female presents with a destructive, expansile lytic lesion in the distal femur. Biopsy confirms a Giant Cell Tumor of Bone. If medical therapy is considered, Denosumab targets which of the following?

Explanation

Denosumab is a monoclonal antibody that binds directly to RANKL, preventing it from activating RANK on the surface of osteoclasts and their precursors. This inhibits osteoclast-mediated bone destruction characteristic of Giant Cell Tumor.

Question 82

In the context of Slipped Capital Femoral Epiphysis (SCFE), prophylactic pinning of the contralateral asymptomatic hip is most strongly indicated for a patient with which of the following underlying conditions?

Explanation

Prophylactic pinning of the contralateral hip is recommended in patients with endocrine disorders (like hypothyroidism) or renal osteodystrophy. These conditions significantly increase the risk of bilateral and sequential slips compared to idiopathic cases.

Question 83

A patient presents with a severe open tibia fracture after a motorcycle collision. The Mangled Extremity Severity Score (MESS) is used to help determine the need for amputation versus limb salvage. Which of the following variables is NOT a component of the MESS criteria?

Explanation

The MESS criteria include skeletal/soft tissue injury, limb ischemia, shock, and patient age. Degree of contamination is part of the Gustilo-Anderson classification but is not a formally scored variable in the MESS system.

Question 84

The alpha-defensin immunoassay is a highly sensitive and specific diagnostic test for periprosthetic joint infection (PJI). Alpha-defensin is an antimicrobial peptide primarily secreted by which of the following cells?

Explanation

Alpha-defensin is released by activated neutrophils in response to infection. Its presence in synovial fluid serves as an accurate biomarker for PJI, remaining reliable even in the presence of systemic antibiotics.

Question 85

A trauma patient presents with acute spinal cord injury following a fall. Which of the following clinical findings most accurately differentiates neurogenic shock from spinal shock?

Explanation

Neurogenic shock is a hemodynamic phenomenon caused by loss of sympathetic tone, resulting in hypotension and bradycardia. Spinal shock refers to the temporary physiological loss of all spinal cord function and reflexes below the injury level.

Question 86

Bone morphogenetic proteins (BMPs) initiate intracellular signaling through transmembrane serine/threonine kinase receptors. Which family of intracellular proteins is directly phosphorylated to translocate into the nucleus and regulate target gene transcription?

Explanation

BMPs signal primarily through the canonical Smad pathway. Upon receptor activation, Smad 1, 5, and 8 are phosphorylated, form a complex with Smad 4, and translocate to the nucleus to induce osteogenic gene expression.

Question 87

During the 'ligamentization' process of a bone-patellar tendon-bone autograft used for ACL reconstruction, at which postoperative time frame is the graft biomechanically at its weakest?

Explanation

The graft is weakest during the remodeling/necrotic phase, typically around 6-8 weeks postoperatively. During this time, the graft undergoes revascularization and cellular repopulation, significantly decreasing its structural properties.

Question 88

Nitrogen-containing bisphosphonates, such as alendronate, inhibit osteoclast-mediated bone resorption by disrupting the mevalonate pathway. Which specific enzyme is inhibited by these medications?

Explanation

Nitrogenous bisphosphonates inhibit farnesyl pyrophosphate synthase within the mevalonate pathway. This prevents the prenylation of small GTPase proteins (like Rho and Rab), ultimately leading to osteoclast apoptosis.

Question 89

A 45-year-old male presents with a painful midshaft femur nonunion 8 months after intramedullary nailing. Radiographs show abundant callus formation around the fracture site with a visible radiolucent line. What is the most appropriate definitive management?

Explanation

The presence of abundant callus (hypertrophic nonunion) indicates adequate biology but insufficient mechanical stability. Exchange nailing provides increased stiffness and stability, which is the primary treatment requirement.

Question 90

A 4-week-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). Excessive hyperflexion of the hips in the harness most commonly risks injury to which of the following nerves?

Explanation

Excessive flexion in a Pavlik harness (greater than 100-120 degrees) can compress the femoral nerve against the inguinal ligament, leading to transient femoral nerve palsy. Excessive abduction, on the other hand, risks avascular necrosis.

Question 91

A 22-year-old male presents with a slow-growing soft tissue mass in his foot. Biopsy reveals a biphasic tumor pattern. Cytogenetic analysis shows a t(X;18)(p11;q11) translocation. What is the most likely diagnosis?

Explanation

The t(X;18) translocation is the diagnostic hallmark of synovial sarcoma, resulting in the SYT-SSX fusion gene. Despite its name, this aggressive soft tissue sarcoma rarely arises within actual joint spaces.

Question 92

In normal articular cartilage, the highest concentration of proteoglycans and the lowest concentration of water are found in which histologic zone?

Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its collagen fibers are oriented perpendicular to the joint surface to resist compressive forces.

Question 93

A traumatic spondylolisthesis of the axis (Hangman's fracture) typically involves bilateral fractures through the pars interarticularis of C2. In modern clinical practice (e.g., motor vehicle accidents), what is the most common mechanism of injury?

Explanation

While the historical mechanism (judicial hanging) involves hyperextension and axial distraction, modern Hangman's fractures usually result from motor vehicle accidents involving hyperextension combined with axial loading.

Question 94

According to current consensus guidelines, chronic suppressive antibiotic therapy for a periprosthetic joint infection is most appropriate for a patient meeting which of the following criteria?

Explanation

Chronic suppressive antibiotics are indicated for patients with a retained, well-fixed prosthesis who are unfit for revision surgery. The pathogen must be of low virulence, highly susceptible to an oral antibiotic, and there should be no loosening or draining sinus.

Self Assessment Examination Adult S Review | Dr Hutaif - ...

Free Orthopedics Review | Dr Hutaif General Orthopedics -...

Key Takeaway

Free Orthopedics Review | Dr Hutaif General Orthopedics -...

Chapter Index