Figure 1 is the MR image of a 55-year-old man who sustained an acute traumatic injury to his right shoulder with loss of active range of motion. He was initially evaluated by his primary care physician and treated with physical therapy without succes

no difference in terminal range of motion.

In a patient who has had low back pain for less than 2 weeks, which of the following findings is an indication for continued observation and symptomatic treatment rather than more aggressive evaluation and/or treatment?

Inability to participate in athletics

A 22-year-old professional baseball catcher has posterior shoulder pain and severe external rotation weakness with the arm in adduction. Radiographs are normal. MRI scans are shown in Figures 15a through 15c. Management should consist of Review Topic

arthroscopic repair and decompression.

A 45-year-old woman has idiopathic scoliosis. Surgery is to include an anterior thoracic release through an open left thoracotomy. The thoracotomy will have what effect on the patient’s pulmonary function postoperatively?

Reduced postoperatively and often remains reduced long term

open biopsy and plating

open biopsy and wide resection of the tumor

ABFigures 60a and 60b are the postmyelography CT images of a 62-year-old man who has had low-back and bilateral lower-extremity pain. His pain began approximately 1 year ago and there was no precipitating event. The location of the pain is in the low

Posterior decompression and fusion

What is the most common complication following metatarsal osteotomy for a bunion deformity in an adolescent?

Recurrence of the hallux valgus

A 28-year-old woman has a moderate hallux valgus deformity and a prominence of the medial eminence. She can participate in all activities and reports that she could wear 3-inch heels in the past, but she now notes medial eminence pain even while wear

Chevron osteotomy to correct hallux valgus

Orthopedic Review Questions & Answers | Dr Hutaif

Question 1

A 45-year-old patient is scheduled to undergo a posterolateral spinal fusion using a structural cortical autograft. What is the primary mechanism by which a cortical autograft is initially incorporated into the host bone?

Explanation

Cortical autografts incorporate via creeping substitution, which begins with osteoclastic resorption of the dense cortical bone, followed later by osteoblastic bone formation. In contrast, cancellous bone incorporates via early osteoblastic apposition on the existing trabecular scaffold before osteoclastic remodeling occurs.

Question 2

Articular cartilage is a complex tissue with varying properties across its depth. Which of the following accurately describes the composition of the deep (radial) zone of articular cartilage compared to the superficial zone?

Explanation

The deep (radial) zone of articular cartilage contains the lowest water content, the highest proteoglycan concentration, and the lowest concentration of chondrocytes. The collagen fibers in this zone are thickest and oriented perpendicularly (vertically) to the joint surface to resist compressive loads.

Question 3

A 70-year-old female treated with alendronate for 8 years presents with thigh pain and a transverse subtrochanteric fracture with lateral cortical thickening. What is the molecular mechanism of action of the medication responsible for this atypical fracture?

Explanation

Alendronate is a nitrogen-containing bisphosphonate. Its mechanism of action is the inhibition of farnesyl pyrophosphate synthase (FPPS) within the mevalonate pathway. This prevents the prenylation of small GTPases (like Ras, Rho, Rab), leading to osteoclast apoptosis and decreased bone remodeling, which over time can cause brittle bone and atypical femur fractures.

Question 4

A 15-year-old boy presents with severe, unrelenting mid-thigh pain. Radiographs reveal a permeative, destructive diaphyseal bone lesion in the femur with a prominent 'onion-skin' periosteal reaction. Biopsy demonstrates a population of small, round, blue cells. Which chromosomal translocation is most characteristically associated with this pathology?

Explanation

The clinical presentation and histology are classic for Ewing sarcoma. Ewing sarcoma is characterized by the t(11;22)(q24;q12) chromosomal translocation in about 85% of cases, resulting in the EWS-FLI1 fusion protein. Synovial sarcoma is t(X;18), myxoid liposarcoma is t(12;16), and alveolar rhabdomyosarcoma is t(2;13).

Question 5

During a cemented total knee arthroplasty, the surgeon mixes polymethylmethacrylate (PMMA) bone cement. What is the primary role of barium sulfate in the PMMA powder mixture?

Explanation

Barium sulfate (or zirconium dioxide) is added to the PMMA powder specifically to act as a radiopacifier, allowing the cement mantle to be visualized on postoperative radiographs. Benzoyl peroxide is the initiator, N,N-dimethyl-p-toluidine is the accelerator, and hydroquinone is the stabilizer.

Question 6

A 6-year-old child presents with progressive bowing of the lower extremities. Laboratory studies reveal normal serum calcium, critically low serum phosphorus, and elevated alkaline phosphatase. Genetic testing confirms a mutation in the PHEX gene. Which of the following substances is excessively produced in this patient's condition?

Explanation

The patient has X-linked hypophosphatemic rickets, the most common heritable form of rickets, caused by a mutation in the PHEX gene. This leads to an overproduction of FGF-23, which promotes renal phosphate wasting and decreases the activity of 1-alpha-hydroxylase, preventing the activation of vitamin D.

Question 7

A 32-year-old male arrives in the emergency department with a highly displaced midshaft tibia fracture. He is complaining of severe pain out of proportion to his injury. His diastolic blood pressure is 75 mmHg. Compartment pressure measurements are obtained using a solid-state transducer. According to widely accepted clinical guidelines, at what absolute compartment pressure measurement would the delta pressure strongly indicate the need for a four-compartment fasciotomy?

Explanation

Compartment syndrome is a clinical diagnosis, but pressure measurements are helpful when the diagnosis is ambiguous. The 'delta pressure' is calculated as Diastolic Blood Pressure minus Compartment Pressure. A delta pressure of less than 30 mmHg (some sources say <20-30 mmHg) is an indication for fasciotomy. With a diastolic BP of 75 mmHg, an absolute compartment pressure of 46 mmHg yields a delta pressure of 29 mmHg, which is <30 mmHg and therefore indicates fasciotomy.

Question 8

During revision of a modular metal-on-polyethylene total hip arthroplasty, the surgeon observes significant black corrosive debris and tissue staining localized specifically at the modular head-neck taper junction. Which type of corrosion is primarily responsible for this localized wear mechanism?

Explanation

The localized wear and corrosion at the modular head-neck taper junction is classically referred to as trunnionosis. This is primarily caused by mechanically assisted crevice corrosion, commonly termed fretting corrosion. Micro-motion at the interface (fretting) repeatedly disrupts the passive oxide layer of the metal, accelerating corrosive degradation in the fluid-filled crevice.

Question 9

According to Perren's strain theory of bone healing, the type of tissue that forms in a fracture gap is dictated by the amount of mechanical strain the tissue can tolerate without failing. What is the approximate maximum strain tolerance of granulation tissue?

Explanation

Perren's strain theory posits that cells can only produce a given extracellular matrix if the strain in the fracture gap does not exceed the strain tolerance of that matrix. Granulation tissue can tolerate up to 100% strain. Fibrocartilage tolerates roughly 10-15% strain, woven bone tolerates about 2% strain, and lamellar bone can tolerate <2% strain.

Question 10

In the pathogenesis of periprosthetic joint infections, bacterial biofilm formation significantly complicates non-operative eradication. Which of the following mechanisms is the primary reason biofilm-associated bacteria are highly resistant to systemic beta-lactam antibiotics?

Explanation

While biofilms utilize several mechanisms to resist clearance (including acting as a physical barrier), the most significant factor conferring profound resistance to systemic antibiotics (especially beta-lactams, which target actively dividing cell walls) is the altered metabolic state of the bacteria. Bacteria deep in the biofilm exist in a stationary, sessile phase with very low metabolic activity and virtually no division, rendering cell-wall targeting agents largely ineffective.

Question 11

When applying an external fixator for a damage-control orthopedics approach, drilling through the diaphyseal cortical bone can generate significant heat, risking thermal necrosis and subsequent pin loosening or infection. To minimize peak intraosseous temperatures, which drilling parameters are most optimal?

Explanation

Thermal necrosis occurs when bone is subjected to temperatures above 47°C for more than one minute. To minimize heat generation during drilling or pin insertion, the surgeon should use a low drill speed and high axial pressure. Low speed reduces frictional heat generation, while high pressure increases the feed rate (the 'bite' of the drill), reducing the time the drill bit spins in place.

Question 12

A patient develops severe hypocalcemia following an inadvertent resection of the parathyroid glands during thyroidectomy. Normally, parathyroid hormone (PTH) regulates serum calcium by acting directly on bone and kidney. What is a primary direct action of PTH on the renal tubules?

Explanation

Parathyroid hormone (PTH) acts on the kidneys in several ways to increase serum calcium: it significantly increases calcium reabsorption in the distal convoluted tubule, it decreases phosphate reabsorption in the proximal tubule, and it strongly stimulates 1-alpha-hydroxylase activity. This enzyme converts 25-hydroxyvitamin D into the highly active 1,25-dihydroxyvitamin D, which subsequently increases intestinal calcium absorption.

Question 13

The insertion site of a tendon or ligament into bone, known as an enthesis, typically consists of four distinct histological zones that transition mechanical stress. Which zone is immediately distal to the tidemark and provides a transitional gradient of stiffness?

Explanation

A direct ligamentous/tendinous insertion consists of 4 zones: Zone 1 (tendon/ligament), Zone 2 (uncalcified fibrocartilage), Zone 3 (calcified fibrocartilage), and Zone 4 (bone). The 'tidemark' is the basophilic line separating the uncalcified (Zone 2) and calcified (Zone 3) fibrocartilage layers. Therefore, the zone immediately distal to (or deep to) the tidemark is the calcified fibrocartilage.

Question 14

A new diagnostic imaging modality is being tested to detect scaphoid fractures. In a study of 200 patients (100 with true scaphoid fractures and 100 normal wrists), the test correctly identifies a fracture in 80 patients and correctly rules out a fracture in 90 patients. What is the sensitivity of this new imaging modality?

Explanation

Sensitivity is defined as the proportion of actual positives that are correctly identified by the test (True Positives / [True Positives + False Negatives]). In this scenario, there are 100 true fractures. The test correctly identifies 80 (True Positives). The remaining 20 fractures were missed (False Negatives). Sensitivity = 80 / (80 + 20) = 80%.

Question 15

An 8-year-old boy incidentally undergoes radiography of the humerus, revealing a centrally located, well-circumscribed, radiolucent lesion in the proximal metaphysis with a cortical fragment resting at the dependent aspect of the cyst ('fallen leaf' sign). If aspirated, what is the most likely composition of the fluid contained within this lesion?

Explanation

The 'fallen leaf' sign and the location are pathognomonic for a Unicameral Bone Cyst (UBC), also known as a simple bone cyst. Aspiration of a UBC typically yields clear, yellow, serous fluid that is biochemically characterized by high levels of prostaglandins, particularly PGE2. Aneurysmal bone cysts (ABCs), in contrast, yield blood.

Question 16

A 24-year-old athlete sustains a traction injury to the neck and shoulder. Clinical examination reveals profound weakness in shoulder abduction initiation and external rotation, with isolated atrophy of the supraspinatus and infraspinatus. Sensation over the lateral deltoid is intact. From which specific component of the brachial plexus does the affected nerve originate?

Explanation

The patient exhibits a suprascapular nerve palsy, innervating the supraspinatus (abduction initiation) and infraspinatus (external rotation). Sensation over the lateral deltoid is intact, distinguishing it from an axillary nerve injury. The suprascapular nerve originates directly from the Upper Trunk (C5, C6) of the brachial plexus.

Question 17

Fat embolism syndrome (FES) is a potentially life-threatening complication in orthopedic trauma. Among the following scenarios, which carries the highest pathophysiological risk for the release of embolic marrow fat into the venous circulation?

Explanation

Fat embolism syndrome is most commonly associated with fractures of long bones, particularly the femur. Reaming the intramedullary canal dramatically increases intramedullary pressures (often >500 mmHg), which forces marrow contents, including fat and pro-coagulant tissue factors, directly into the venous sinuses and systemic circulation. While unreamed nailing or other procedures carry risk, reamed femoral nailing has historically posed the highest discrete risk for embolic showers.

Question 18

Aseptic loosening secondary to osteolysis is a leading cause of late failure in total joint arthroplasty. Which fundamental mechanism of wear is primarily responsible for the generation of the millions of submicron-sized ultra-high-molecular-weight polyethylene (UHMWPE) particles that incite this macrophage-mediated osteolysis?

Explanation

In metal-on-polyethylene articulations, adhesive wear occurs when localized microscopic bonding/welding happens between the asperities of the metal head and the softer polymer. As the joint moves, these micro-bonds shear off, creating millions of submicron UHMWPE particles. These specific submicron particles (0.1 to 1.0 micrometers) are phagocytosed by macrophages, initiating the inflammatory cascade (TNF-a, IL-1, IL-6) leading to osteolysis.

Question 19

Platelet-rich plasma (PRP) is extensively utilized in general orthopedics to theoretically enhance soft tissue healing. The alpha granules of platelets release numerous growth factors upon degranulation. Which of the following growth factors released from PRP is the primary molecular driver of angiogenesis?

Explanation

Platelet alpha granules contain multiple growth factors including PDGF, TGF-beta, VEGF, and IGF. Vascular Endothelial Growth Factor (VEGF) is the primary and most potent signaling molecule responsible for angiogenesis (the formation of new blood vessels), which is critical for restoring blood flow during the early phases of tissue repair.

Question 20

Following a closed humerus fracture, a patient develops a complete radial nerve palsy. Electromyography (EMG) at 4 weeks shows fibrillations, but no voluntary motor unit action potentials. Pathologically, the injury involves complete disruption of the axon and myelin sheath, but the endoneurium, perineurium, and epineurium remain completely intact. According to the Seddon classification, what is this specific grade of nerve injury?

Explanation

Seddon classified nerve injuries into three main categories: Neuropraxia (conduction block without structural disruption, reversible), Axonotmesis (disruption of axon and myelin, but intact connective tissue sheaths; Wallerian degeneration occurs, but spontaneous recovery is possible along the intact endoneurial tubes), and Neurotmesis (complete transection of the nerve including connective tissue, requiring surgery). The scenario describes axonotmesis (which corresponds to Sunderland Grade II).

Question 21

A 35-year-old male undergoes open reduction and internal fixation for a tibial shaft fracture. The surgeon utilizes a recombinant human bone morphogenetic protein (rhBMP-2) to augment healing. Which of the following best describes the intracellular signaling pathway directly activated by this biologic agent?

Explanation

BMP-2 binds to serine/threonine kinase receptors on the cell surface, leading to the intracellular phosphorylation of Smad 1, 5, and 8. These complex with Smad 4 to translocate to the nucleus and promote osteogenic gene expression.

Question 22

A 24-year-old male is brought to the trauma bay following a motorcycle collision. He is hypotensive with a systolic blood pressure of 75 mmHg. Pelvic radiograph shows an APC-III pelvic ring injury. A pelvic binder is applied, and he receives 2 units of packed red blood cells, but his hemodynamics do not improve. FAST scan is negative. What is the most appropriate next step in management?

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST scan, the source of bleeding is presumed to be the pelvis. The next appropriate step is preperitoneal pelvic packing or pelvic angiography for embolization.

Question 23

A 68-year-old male presents with severe thigh pain 12 years after a cementless total hip arthroplasty. Radiographs reveal extensive endosteal scalloping and proximal femoral osteolysis. What is the primary cellular mediator responsible for this periprosthetic osteolysis?

Explanation

Periprosthetic osteolysis in total joint arthroplasty is primarily driven by a macrophage-mediated foreign body response to ultra-high-molecular-weight polyethylene (UHMWPE) wear debris. Macrophages release inflammatory cytokines like TNF-alpha and IL-1, activating osteoclasts.

Question 24

A 9-year-old obese boy presents with a 3-week history of right groin pain and a limp. Examination reveals obligate external rotation with hip flexion. Radiographs confirm a mild Slipped Capital Femoral Epiphysis (SCFE). Given the patient's age, what underlying systemic condition must be considered and screened for?

Explanation

SCFE is typically seen in early adolescence. When it occurs in children younger than 10 or older than 16 years, or in those under the 50th percentile for weight, an underlying endocrine disorder such as hypothyroidism or renal osteodystrophy should be suspected.

Question 25

A 15-year-old female presents with a distal femoral mass. MRI suggests an aggressive primary bone sarcoma. A biopsy is planned. Which of the following is an absolute principle of a musculoskeletal oncology biopsy?

Explanation

A biopsy for a suspected bone sarcoma must utilize a longitudinal incision that is perfectly in line with the planned definitive excision. This allows the entire biopsy tract to be excised en bloc with the tumor to prevent local recurrence.

Question 26

A 55-year-old male presents with bilateral hand clumsiness and broad-based gait. Examination reveals a positive Hoffmann's sign and sustained ankle clonus. MRI shows severe cervical stenosis at C5-C6 with T2 hyperintensity in the cord. The pathological progression of this condition is most directly associated with ischemia of which of the following vascular structures?

Explanation

Cervical spondylotic myelopathy is caused by direct mechanical compression and secondary ischemia. Compression of the anterior spinal artery leads to ischemic injury of the anterior and lateral funiculi, producing upper motor neuron signs.

Question 27

During an anterior cruciate ligament (ACL) reconstruction, the surgeon evaluates the femoral footprint. The ACL consists of two functional bundles. Which of the following statements accurately describes the biomechanical role of the ACL bundles?

Explanation

The anteromedial (AM) bundle of the ACL is tight in flexion and is the primary restraint to anterior tibial translation. The posterolateral (PL) bundle is tight in extension and primarily controls rotational stability.

Question 28

A 32-year-old male sustains a severe laceration to the volar wrist, completely transecting the ulnar nerve proximal to the Guyon's canal. Several months later, he presents with significant clawing of the ring and small fingers. Which of the following explains why a more distal injury would have resulted in even more severe clawing?

Explanation

The 'ulnar paradox' occurs because a more proximal ulnar nerve lesion denervates both the intrinsic hand muscles and the ulnar half of the FDP. A distal lesion spares the FDP, allowing its unopposed action on the DIP joint, which causes a more pronounced claw deformity.

Question 29

A 22-year-old football player sustains a hyperplantarflexion injury to his midfoot. Weight-bearing radiographs show 3 mm of widening between the medial cuneiform and the base of the second metatarsal. Which ligament is primarily disrupted in this classic injury?

Explanation

The Lisfranc ligament is an interosseous ligament that runs from the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is the primary stabilizer of the second tarsometatarsal joint.

Question 30

A surgeon uses a titanium alloy screw to secure a stainless steel plate in a fracture fixation. Over time, the implant site demonstrates significant corrosion and osteolysis. What specific type of corrosion is occurring due to the use of these two different metals?

Explanation

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within an electrolytic fluid environment (like human serum). The less noble metal becomes the anode and undergoes accelerated corrosion.

Question 31

A 40-year-old male sustains a high-energy varus and axial load injury to his knee, resulting in a Schatzker IV tibial plateau fracture (medial plateau). Due to the mechanism and displacement, which associated vascular structure is at the highest risk for injury?

Explanation

Schatzker IV fractures (medial plateau) are often the result of high-energy trauma (varus/axial load) and can be associated with knee subluxation or dislocation, placing the tethered popliteal artery at high risk of injury.

Question 32

During a total knee arthroplasty (TKA), the surgeon places the femoral component in excessive internal rotation relative to the transepicondylar axis. Which of the following complications is most likely to occur postoperatively?

Explanation

Internal rotation of the femoral component in TKA mediatizes the trochlear groove, which effectively increases the Q-angle and leads to lateral patellar maltracking and potential subluxation.

Question 33

A 4-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The mother notes that the child is no longer extending her knee actively on the treated side. What is the most likely cause of this complication?

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness if the hip is positioned in excessive flexion. It is typically reversible upon releasing or adjusting the harness to reduce the flexion angle.

Question 34

A 30-year-old female is diagnosed with an unresectable giant cell tumor of the sacrum. She is started on denosumab therapy. What is the exact mechanism of action of this medication?

Explanation

Denosumab is a fully human monoclonal antibody that binds to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL), preventing it from interacting with RANK on the surface of osteoclasts and their precursors, thereby halting osteoclast-mediated bone destruction.

Question 35

A 60-year-old male presents with bilateral leg pain and cramping that worsens with walking and prolonged standing, but improves when he leans forward over a shopping cart. MRI shows severe lumbar spinal stenosis at L4-L5. What anatomical structure hypertrophies and buckles into the spinal canal during extension, contributing to his symptoms?

Explanation

Neurogenic claudication is worsened by spinal extension, which causes the hypertrophied ligamentum flavum to buckle anteriorly into the spinal canal, further compressing the neural elements. Flexion stretches the ligament, increasing canal volume and relieving symptoms.

Question 36

A 28-year-old carpenter sustains a laceration to the volar aspect of his index finger at the level of the proximal phalanx, transecting both the FDS and FDP tendons. He undergoes primary flexor tendon repair. To permit a safe early active motion protocol postoperatively, the repair must rely primarily on which mechanical parameter?

Explanation

The tensile strength of a flexor tendon repair is directly proportional to the number of core suture strands crossing the repair site. A minimum of 4 strands (and ideally 4-6) is required to safely withstand the forces generated during an early active motion protocol.

Question 37

A 25-year-old elite volleyball player complains of vague posterior shoulder pain and weakness. Physical examination reveals isolated weakness in external rotation with the arm at the side, but normal forward elevation and internal rotation. MRI reveals a paralabral cyst. Where is the cyst most likely located to produce this specific deficit?

Explanation

Entrapment of the suprascapular nerve at the spinoglenoid notch affects only the infraspinatus muscle, leading to isolated external rotation weakness. Entrapment at the more proximal suprascapular notch would affect both the supraspinatus and infraspinatus.

Question 38

A 55-year-old male develops a spontaneous Achilles tendon rupture two weeks after completing a course of antibiotics for a respiratory infection. Which class of antibiotics is associated with an increased risk of tendinopathy and rupture by upregulating matrix metalloproteinases (MMPs) and decreasing type I collagen synthesis?

Explanation

Fluoroquinolones (e.g., ciprofloxacin, levofloxacin) are known to cause tendinopathy and tendon rupture. The mechanism involves toxicity to tenocytes, upregulation of MMPs, and inhibition of type I collagen synthesis.

Question 39

When choosing an intramedullary nail for a femur fracture, a surgeon decides to use a 12 mm solid nail instead of a 10 mm solid nail of the same material. According to biomechanical principles, the bending rigidity of the nail increases by a factor proportional to the radius raised to what power?

Explanation

The bending rigidity of a solid cylindrical orthopedic implant is determined by the area moment of inertia, which is proportional to the radius to the fourth power (r^4). Thus, a small increase in nail diameter yields a massive increase in bending stiffness.

Question 40

A 30-year-old farm worker sustains a severe open tibial shaft fracture (Gustilo-Anderson Grade IIIB) highly contaminated with soil. In addition to prompt surgical debridement and standard cephalosporin coverage, which antibiotic should be added to specifically cover likely soil-based pathogens like Clostridium?

Explanation

Farm injuries or severe open fractures highly contaminated with soil carry a high risk of clostridial infection. The standard antibiotic protocol involves a first-generation cephalosporin, an aminoglycoside (for gram-negatives), and high-dose Penicillin to cover anaerobes like Clostridium.

Question 41

In the context of biomechanics of ligaments and tendons, which of the following terms describes the gradual increase in deformation of a viscoelastic material over time when subjected to a constant, sustained load?

Explanation

Creep refers to the progressive deformation of a viscoelastic material when subjected to a constant load over time. This concept is utilized clinically in serial casting and traction. Stress relaxation, conversely, is the decrease in stress over time when the material is held at a constant length.

Question 42

Highly cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) is widely used in total hip arthroplasty. While cross-linking significantly reduces adhesive and abrasive wear, it has which of the following detrimental effects on the mechanical properties of the polyethylene?

Explanation

Increasing the cross-linking of UHMWPE significantly improves its wear resistance but at the cost of decreasing its mechanical properties, including fatigue strength, yield strength, and ultimate tensile strength. To mitigate oxidation, free radicals generated during cross-linking are eliminated through processes like remelting or annealing, or by adding antioxidants like Vitamin E.

Question 43

A 35-year-old male is brought to the emergency department after a high-speed motor vehicle collision. He is hemodynamically unstable with a suspected anterior-posterior compression (APC) type III pelvic ring injury. When applying a non-invasive pelvic circumferential compression device (pelvic binder), at what anatomical level should it be centered for maximum efficacy?

Explanation

A pelvic binder must be centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement higher over the iliac crests is less effective and may paradoxically open the true pelvis in certain fracture patterns.

Question 44

A 28-year-old female presents with a destructive, eccentric, lytic lesion in the distal femur that extends to the subchondral bone. Biopsy confirms Giant Cell Tumor of bone. Medical management with denosumab is considered. What is the specific molecular mechanism of action of this medication?

Explanation

Denosumab is a monoclonal antibody that binds to RANKL, preventing it from interacting with the RANK receptor on osteoclasts and their precursors. This inhibits osteoclast-mediated bone resorption, which is the primary driver of osteolysis in Giant Cell Tumor of bone.

Question 45

A 40-year-old mechanic presents with a swollen, erythematous right index finger after sustaining a puncture wound 3 days ago. Which of Kanavel's four cardinal signs of flexor tenosynovitis is typically considered the earliest and most sensitive indicator of the infection?

Explanation

Pain with passive extension of the affected digit is considered the earliest and most sensitive sign of pyogenic flexor tenosynovitis. The other cardinal signs include fusiform swelling, resting in a flexed posture, and exquisite tenderness along the flexor sheath.

Question 46

Slipped Capital Femoral Epiphysis (SCFE) is characterized by displacement of the proximal femoral epiphysis relative to the femoral neck. In this condition, the failure of the physis predominantly occurs through which specific histological zone?

Explanation

The biomechanical failure in Slipped Capital Femoral Epiphysis occurs almost exclusively through the hypertrophic zone of the physis. This zone is the weakest portion of the growth plate due to the lack of collagenous bridging and the large size of the chondrocytes.

Question 47

A 68-year-old male complains of bilateral leg pain and cramping that worsens with walking and prolonged standing, but improves when he leans forward on a shopping cart. The symptomatic relief he experiences with forward flexion is primarily due to which of the following anatomic changes in the lumbar spine?

Explanation

Forward flexion of the lumbar spine increases the cross-sectional area of the spinal canal and neural foramina. This is primarily achieved through the unbuckling (tightening) of the ligamentum flavum, providing relief in neurogenic claudication caused by lumbar spinal stenosis.

Question 48

Following anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, the graft undergoes a process of 'ligamentization'. During this biological remodeling process, at what postoperative time frame is the graft biomechanically at its weakest?

Explanation

The ACL graft is biomechanically weakest during the 'proliferation' or revascularization phase, which typically occurs around 6 to 8 weeks postoperatively. During this time, the graft tissue is undergoing significant necrosis and subsequent cellular repopulation.

Question 49

According to Perren's strain theory, the type of bone healing that occurs depends on the mechanical environment at the fracture site. For absolute stability and primary (osteonal) bone healing to occur, the strain at the fracture gap must be maintained below what threshold?

Explanation

Perren's strain theory states that primary (direct) bone healing via cutting cones requires absolute stability with a tissue strain of less than 2%. Strains between 2% and 10% typically result in secondary bone healing via callus formation.

Question 50

A 25-year-old male sustains a closed tibial shaft fracture. Two hours later, he develops severe pain out of proportion to the injury. Which of the following objective measurement criteria is the most reliable threshold for diagnosing acute compartment syndrome and indicating the need for fasciotomy?

Explanation

The most reliable parameter for diagnosing acute compartment syndrome is the delta pressure (ΔP), defined as the diastolic blood pressure minus the compartment pressure. A ΔP of less than 30 mmHg strongly indicates inadequate tissue perfusion and is a threshold for performing a fasciotomy.

Question 51

Orthopedic implant infections are notoriously difficult to eradicate due to biofilm formation. Within a mature biofilm, bacteria coordinate their behavior, alter gene expression, and increase virulence based on local population density. What is the term for this cell-to-cell communication mechanism?

Explanation

Quorum sensing is the process by which bacteria communicate chemically within a biofilm, allowing them to detect population density and coordinate gene expression. This leads to increased virulence and profound resistance to systemic antibiotics.

Question 52

A 55-year-old female presents with diffuse bone pain and proximal muscle weakness. Laboratory evaluation reveals hypocalcemia, hypophosphatemia, elevated parathyroid hormone (PTH), and elevated alkaline phosphatase. Which of the following is the most likely diagnosis?

Explanation

The laboratory profile of low calcium, low phosphorus, high alkaline phosphatase, and high PTH is characteristic of osteomalacia, typically due to severe vitamin D deficiency. In contrast, osteoporosis presents with normal serum calcium, phosphorus, and alkaline phosphatase levels.

Question 53

A 60-year-old male undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing surface. At his 1-year follow-up, he complains of an audible squeaking sound from the hip during certain movements. Which of the following surgical factors is most strongly associated with this complication?

Explanation

Squeaking in ceramic-on-ceramic THA is heavily linked to implant malposition, particularly excessive anteversion or inclination of the acetabular cup. Malposition leads to edge loading, disruption of fluid-film lubrication, and subsequent stripe wear and noise generation.

Question 54

A 6-year-old boy sustains a completely displaced supracondylar humerus fracture. Radiographs reveal the distal fragment is displaced posterolaterally. Based on this displacement pattern, which nerve is at the highest risk of injury?

Explanation

In a posterolaterally displaced supracondylar fracture, the proximal fragment is driven anteromedially, placing the median nerve (specifically the anterior interosseous nerve branch) at greatest risk. Posteromedial displacement places the radial nerve at risk, while flexion-type fractures risk ulnar nerve injury.

Question 55

In rotator cuff tear arthropathy, the massive, irreparable tearing of the supraspinatus and infraspinatus tendons leads to superior migration of the humeral head. This phenomenon is biomechanically attributed to the disruption of which of the following forces?

Explanation

Superior migration of the humeral head in rotator cuff arthropathy is due to the loss of the coronal plane force couple. Normally, the inferior pull of the rotator cuff balances the superior pull of the deltoid; loss of the cuff allows the deltoid to pull the humeral head superiorly against the acromion.

Question 56

The Lisfranc ligament is crucial for the stability of the midfoot and prevention of tarsometatarsal dissociation. What are the correct anatomical origin and insertion points of the Lisfranc ligament?

Explanation

The Lisfranc ligament is a strong interosseous ligament that runs from the plantar-lateral aspect of the medial cuneiform to the plantar-medial aspect of the base of the second metatarsal. There is no direct ligamentous connection between the 1st and 2nd metatarsal bases.

Question 57

A 14-year-old boy presents with a painful, swollen thigh. Radiographs show a permeative, 'moth-eaten' lesion in the femoral diaphysis with an 'onion-skin' periosteal reaction. Cytogenetic testing of the biopsy specimen is most likely to reveal which of the following chromosomal translocations?

Explanation

The presentation is classic for Ewing sarcoma. Over 90% of Ewing sarcomas are characterized by the t(11;22)(q24;q12) translocation, which results in the EWS-FLI1 fusion protein. Synovial sarcoma is associated with t(X;18), and myxoid liposarcoma with t(12;16).

Question 58

A 50-year-old male presents with right-sided neck pain radiating down his arm, accompanied by numbness in his thumb and index finger. On physical exam, he has weakness in wrist extension and a diminished deep tendon reflex. Which reflex is most likely diminished in this clinical scenario?

Explanation

The patient's presentation of numbness in the thumb/index finger and wrist extension weakness points to a C6 radiculopathy. The brachioradialis reflex is innervated primarily by the C6 nerve root, while the biceps reflex is C5 and the triceps is C7.

Question 59

The vascular supply to the adult femoral head is highly precarious, making displaced femoral neck fractures prone to avascular necrosis. Which of the following vessels provides the primary blood supply to the weight-bearing dome of the adult femoral head?

Explanation

The medial femoral circumflex artery (MFCA), specifically its lateral epiphyseal branches, provides the predominant blood supply to the weight-bearing portion of the adult femoral head. The artery of the ligamentum teres contributes a clinically insignificant amount in adults.

Question 60

Averaging 60% articular cartilage coverage, the talus has limited areas for vascular penetration, rendering it susceptible to avascular necrosis following a talar neck fracture. Which of the following arteries is the major contributor to the blood supply of the talar body?

Explanation

The artery of the tarsal canal, a branch of the posterior tibial artery, is the most significant source of blood to the talar body. It anastomoses with the artery of the sinus tarsi, but disruption of the tarsal canal vessel during talar neck fractures critically endangers the body's perfusion.

Question 61

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

Explanation

Titanium alloy has a highly stable passivating titanium dioxide layer, conferring excellent biocompatibility and corrosion resistance. It has a lower modulus of elasticity (closer to bone) and higher notch sensitivity compared to stainless steel.

Question 62

A 35-year-old male sustains a diaphyseal tibia fracture treated with an intramedullary nail. During the reparative phase of secondary bone healing, which collagen type predominantly transitions to Type I collagen?

Explanation

During secondary bone healing, the soft callus primarily consists of cartilage, which is rich in Type II collagen. As the soft callus undergoes endochondral ossification into a hard callus, Type II collagen is replaced by Type I collagen.

Question 63

A 14-year-old boy presents with knee pain and a destructive, sunburst periosteal reaction in the distal femur. A biopsy confirms conventional osteosarcoma. Mutation of which tumor suppressor gene, normally responsible for regulating the G1 to S phase cell cycle transition, is most strongly associated with this condition?

Explanation

The Retinoblastoma (Rb) gene is a tumor suppressor gene that regulates the G1 to S phase transition in the cell cycle. Mutations in Rb are strongly associated with both hereditary retinoblastoma and osteosarcoma.

Question 64

An infant presents with multiple fractures, hepatosplenomegaly, and cranial nerve palsies. Radiographs show a generalized "bone-in-bone" appearance. The primary cellular defect in this condition is characterized by a failure of which of the following processes?

Explanation

Osteopetrosis is caused by defective osteoclast function, often due to a failure to form the ruffled border or a defect in the carbonic anhydrase II enzyme. This prevents normal bone resorption, leading to excessively dense but brittle bones.

Question 65

A 65-year-old patient with a 15-year-old total hip arthroplasty presents with groin pain. Radiographs reveal extensive periprosthetic osteolysis. Which cytokine is primarily responsible for mediating osteoclast activation in response to polyethylene wear debris?

Explanation

Polyethylene wear debris is phagocytosed by macrophages, which then release pro-inflammatory cytokines like TNF-alpha and IL-1. These cytokines stimulate the production of RANKL, which binds to RANK on osteoclast precursors, leading to osteoclast differentiation and osteolysis.

Question 66

A 72-year-old male develops a chronic periprosthetic joint infection caused by Staphylococcus epidermidis. The pathogenesis of this infection relies heavily on bacterial adherence and biofilm formation. Which component is crucial for the initial irreversible attachment phase of this organism to the implant?

Explanation

Staphylococcus epidermidis produces polysaccharide intercellular adhesin (PIA), which is essential for cell-to-cell adhesion and the formation of the protective biofilm matrix. This makes eradication of the implant-associated infection extremely difficult without hardware removal.

Question 67

Recombinant human bone morphogenetic proteins (rhBMPs) are used to augment spinal fusions. BMPs induce osteogenesis primarily by binding to transmembrane serine/threonine kinase receptors. Which intracellular signaling molecules are subsequently phosphorylated to translocate to the nucleus and initiate transcription?

Explanation

BMPs signal through serine/threonine kinase receptors, leading to the phosphorylation of intracellular Smad proteins (primarily Smad 1, 5, and 8). These phosphorylated Smads then bind to Smad 4, translocate to the nucleus, and regulate the transcription of osteogenic genes.

Question 68

Tranexamic acid (TXA) is frequently administered during orthopedic procedures to reduce perioperative blood loss. What is the specific mechanism of action of this medication?

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It competitively inhibits the activation of plasminogen to plasmin, thereby preventing the degradation of fibrin clots (fibrinolysis).

Question 69

A 10-year-old boy sustains a Salter-Harris Type I fracture of the distal radius. The fracture line typically propagates through which layer of the physis?

Explanation

Salter-Harris fractures typically propagate through the weakest zone of the physis, which is the zone of provisional calcification (specifically the hypertrophic zone's lower part). This zone has increased cell volume and decreased matrix, making it biomechanically vulnerable.

Question 70

A 45-year-old female presents with bilateral ulnar deviation of the MCP joints and morning stiffness. Serological testing for Rheumatoid Arthritis is positive. Which autoantibody is considered the most specific for the diagnosis of this condition?

Explanation

Anti-cyclic citrullinated peptide (anti-CCP) antibodies are highly specific (up to 95-98%) for rheumatoid arthritis and can often be detected before clinical symptoms develop. While Rheumatoid Factor (RF) is sensitive, it is found in many other inflammatory conditions.

Question 71

A surgeon is performing the Smith-Petersen approach to the hip. To safely access the joint, the surgeon must utilize the internervous plane between which two muscles?

Explanation

The Smith-Petersen (anterior) approach to the hip utilizes the internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). This true internervous plane allows for safe access to the anterior capsule.

Question 72

Following a mid-shaft humerus fracture, a patient demonstrates a complete radial nerve palsy. Electromyography (EMG) is ordered to evaluate the extent of the injury. How long after the injury should the EMG be performed to reliably detect fibrillation potentials in the denervated muscles?

Explanation

Fibrillation potentials and positive sharp waves, which indicate muscle denervation following Wallerian degeneration, typically take 3 to 4 weeks to appear on an EMG. Early EMG (before 3 weeks) may yield false-negative results for denervation.

Question 73

A 68-year-old male presents with increasing head size, hearing loss, and bowing of his tibiae. Histological examination of his affected bone would most likely reveal which of the following pathognomonic features?

Explanation

Paget's disease of bone is characterized by abnormal bone remodeling. The hallmark histological finding is a 'mosaic' or 'jigsaw puzzle' pattern of lamellar bone with prominent cement lines, representing chaotic cycles of rapid bone resorption and disorganized formation.

Question 74

In the design of orthopedic plates, what is the biomechanical consequence of increasing the thickness of the plate by a factor of two?

Explanation

The bending stiffness of a plate is proportional to its area moment of inertia, which is calculated as (base x height^3)/12. Therefore, doubling the thickness (height) of the plate increases its bending stiffness by a factor of 2^3, or 8.

Question 75

During the healing process of a surgically repaired Achilles tendon, when is the repair mechanically at its weakest, making it most susceptible to re-rupture?

Explanation

A repaired tendon is mechanically weakest between days 7 and 14. During the inflammatory and early proliferative phases, collagenase activity degrades necrotic tissue, temporarily reducing the tensile strength before new collagen significantly cross-links.

Question 76

A patient undergoing total knee arthroplasty is prescribed Enoxaparin for deep vein thrombosis prophylaxis. What is the primary molecular target by which Enoxaparin exerts its anticoagulant effect?

Explanation

Enoxaparin, a low-molecular-weight heparin (LMWH), binds to antithrombin III. This complex primarily inhibits Factor Xa (with a much higher ratio of anti-Xa to anti-IIa activity compared to unfractionated heparin), effectively preventing clot formation.

Question 77

When utilizing massive structural cortical allografts in tumor reconstruction, which method of allograft processing is most detrimental to the graft's biomechanical strength, specifically decreasing its torsional strength?

Explanation

High-dose gamma irradiation (typically >25-30 kGy), while effective for sterilization, significantly alters the cross-linking of collagen. This drastically reduces the structural integrity and torsional strength of the cortical allograft.

Question 78

A 28-year-old male is evaluated for compartment syndrome of the leg following a severe crush injury. Tissue perfusion in the compartment ceases when the compartment tissue pressure approaches which of the following parameters?

Explanation

Tissue perfusion in a compartment is driven by the arteriovenous gradient. When the interstitial compartment pressure rises to within 10-30 mmHg of the diastolic blood pressure, capillary flow is obstructed, leading to ischemia.

Question 79

A patient sustains a peripheral nerve injury that exhibits Wallerian degeneration, but the endoneurium, perineurium, and epineurium remain intact. Spontaneous recovery is expected. According to Sunderland's classification, what grade is this injury?

Explanation

A second-degree injury (axonotmesis in Seddon's classification) involves disruption of the axon with Wallerian degeneration, but the supporting connective tissue remains intact. This allows the regenerating axon to use the intact endoneurial tube, predicting excellent recovery.

Question 80

A 2-year-old child presents with bowing of the legs, frontal bossing, and widened wrists. Laboratory tests reveal low serum calcium, low phosphorus, and elevated alkaline phosphatase. Which of the following defines the primary histopathologic defect at the growth plate in this patient?

Explanation

Nutritional rickets is caused by Vitamin D deficiency, leading to impaired mineralization of bone and cartilage. At the growth plate, there is a failure of mineralization of the osteoid in the zone of provisional calcification, resulting in a widened and irregular physis.

Question 81

During fracture healing, Bone Morphogenetic Proteins (BMPs) initiate the osteoinductive cascade. Which of the following intracellular signaling molecules is directly phosphorylated following BMP receptor activation?

Explanation

BMPs bind to serine/threonine kinase receptors, leading to the phosphorylation of Smad 1/5/8. These then form a complex with Smad 4 and translocate to the nucleus to regulate target gene expression for osteoblast differentiation.

Question 82

A patient undergoes anterior cruciate ligament (ACL) reconstruction with a soft tissue allograft. Tension is applied to the graft prior to fixation. Over time, the tension required to maintain the graft at a constant length decreases. This viscoelastic property is known as:

Explanation

Stress relaxation is the decrease in stress (tension) over time when a viscoelastic material is held at a constant length. Creep is the increase in deformation (length) over time under a constant load.

Question 83

A 68-year-old female with severe osteoporosis is started on teriparatide. How does the intermittent administration of this medication promote bone formation?

Explanation

Teriparatide (recombinant PTH) given intermittently has an anabolic effect by promoting osteoblast differentiation and survival, largely through modulation of the Wnt signaling pathway. Continuous PTH, conversely, promotes bone resorption.

Question 84

Which of the following components of the extracellular matrix is primarily responsible for the compressive stiffness and water-retaining capacity of articular cartilage?

Explanation

Aggrecan is the most abundant proteoglycan in articular cartilage. Its highly negatively charged glycosaminoglycan chains (chondroitin and keratan sulfate) attract water, creating a swelling pressure that resists compressive loads.

Question 85

A 2-year-old child presents with bowing of the lower extremities, hypocalcemia, and normal 25-hydroxyvitamin D levels but extremely low 1,25-dihydroxyvitamin D levels. What is the most likely underlying genetic defect?

Explanation

Vitamin D-dependent rickets type I is caused by a deficiency in 1-alpha-hydroxylase, the renal enzyme that converts 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D. Type II is caused by a defect in the vitamin D receptor.

Question 86

During longitudinal growth at the physis, which zone is primarily responsible for providing the mechanical weak point where Salter-Harris fractures most commonly occur?

Explanation

The hypertrophic zone lacks significant extracellular matrix and collagen, making it the weakest part of the physis. This zone is typically where separations occur in most Salter-Harris type I, II, and III fractures.

Question 87

A patient is prescribed rivaroxaban for deep vein thrombosis prophylaxis following a total hip arthroplasty. What is the precise mechanism of action of this pharmacological agent?

Explanation

Rivaroxaban and apixaban are direct oral anticoagulants that work by directly inhibiting Factor Xa, interrupting the common pathway of the coagulation cascade. Unlike heparins, they do not require antithrombin III for their activity.

Question 88

A 24-year-old male sustains a closed comminuted femoral shaft fracture. Forty-eight hours post-injury, he develops confusion, tachypnea, and a petechial rash over his axillae. According to Gurd's criteria, which of the following is considered a major criterion for his likely diagnosis?

Explanation

Fat embolism syndrome is diagnosed using Gurd's criteria. The major criteria include petechial rash (typically on the axillae, chest, and conjunctiva), respiratory insufficiency, and cerebral involvement (confusion).

Question 89

A 55-year-old female with breast cancer metastases to the spine is treated with a monoclonal antibody to prevent skeletal-related events. This medication mimics the physiologic action of which of the following endogenous proteins?

Explanation

Denosumab is a monoclonal antibody that binds to RANKL, preventing it from binding to RANK on osteoclasts. This mimics the action of osteoprotegerin (OPG), a natural decoy receptor produced by osteoblasts to inhibit osteoclastogenesis.

Question 90

In the pathogenesis of osteoarthritis, degradation of the type II collagen network is a critical and irreversible step. Which enzyme is primarily responsible for the cleavage of type II collagen in osteoarthritic cartilage?

Explanation

Matrix metalloproteinase-13 (MMP-13) is the primary collagenase responsible for the degradation of type II collagen in osteoarthritis. ADAMTS-4 and ADAMTS-5 are aggrecanases that primarily degrade the proteoglycan aggrecan.

Question 91

During a closed reduction and percutaneous pinning of a supracondylar humerus fracture, a 6-year-old patient develops an unexplained rise in end-tidal CO2, tachycardia, and masseter muscle rigidity. Administration of which medication is the definitive treatment?

Explanation

The patient is exhibiting signs of malignant hyperthermia, an autosomally dominant condition typically triggered by volatile anesthetics and succinylcholine. Dantrolene, a ryanodine receptor antagonist, is the specific antidote.

Question 92

A researcher is evaluating bone turnover markers in a cohort of patients with Paget's disease. Which of the following serum markers is considered the most specific indicator of bone formation and osteoblast activity?

Explanation

Osteocalcin is a non-collagenous protein secreted almost exclusively by osteoblasts, making it a highly specific marker of late osteoblast differentiation and bone formation. TRAP and NTx are markers of bone resorption.

Question 93

Malignant infantile osteopetrosis is a fatal genetic disorder characterized by dense, brittle bones and pancytopenia. The most common genetic defect in this condition impairs which of the following mechanisms?

Explanation

Malignant infantile osteopetrosis is most commonly caused by a mutation in the TCIRG1 gene, which encodes a subunit of the vacuolar proton pump (V-ATPase). This prevents osteoclasts from acidifying the resorption pit, leading to defective bone resorption.

Question 94

A patient with severe nutritional deficiencies presents with bleeding gums, perifollicular hemorrhages, and impaired wound healing. The underlying enzymatic defect impairs bone formation by disrupting which step in collagen synthesis?

Explanation

Scurvy is caused by Vitamin C deficiency. Vitamin C acts as an essential cofactor for prolyl and lysyl hydroxylases, which are required for the hydroxylation of proline and lysine residues, a critical step for stable collagen triple helix formation.

Question 95

Following a closed proximal humerus fracture, a patient exhibits a complete radial nerve palsy. Electromyography at 4 weeks shows fibrillation potentials in the brachioradialis but preserved nerve sheath integrity on imaging. What is the Sunderland classification of this injury?

Explanation

A second-degree nerve injury (Sunderland) corresponds to Seddon's axonotmesis, characterized by axonal disruption with preservation of the endoneurium, perineurium, and epineurium. Fibrillation potentials indicate axonal denervation.

Question 96

A surgeon plans to perform a revision open reduction and internal fixation utilizing both stainless steel plates and titanium screws. This combination is generally avoided due to the risk of which type of corrosion?

Explanation

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within a conductive electrolyte solution (such as body fluid). The less noble metal (anode) undergoes accelerated corrosion.

Question 97

Following the deflation of a pneumatic tourniquet that has been inflated for 90 minutes during a total knee arthroplasty, which of the following transient systemic physiological changes is expected?

Explanation

Tourniquet deflation releases ischemic, acidotic blood back into the systemic circulation. This typically causes a transient increase in end-tidal CO2, a decrease in core body temperature, and a decrease in blood pressure due to a drop in systemic vascular resistance.

Question 98

Secondary bone healing is characterized by intermediate callus formation. According to Perren's strain theory, what is the maximum tissue strain that allows for the formation of lamellar bone?

Explanation

According to Perren's strain theory, lamellar bone can only form in environments with less than 2% strain. Cartilage can form in 2-10% strain, and granulation tissue forms when strain is 10-100%.

Question 99

A 32-year-old male presents with severe pain out of proportion to exam after a tibial shaft fracture. When using continuous intracompartmental pressure monitoring, an acute compartment syndrome is diagnosed when the Delta P (diastolic blood pressure minus compartment pressure) falls below what threshold?

Explanation

A Delta P (diastolic blood pressure minus intracompartmental pressure) of less than 30 mmHg is considered the diagnostic threshold for acute compartment syndrome, necessitating emergent fasciotomies.

Question 100

During the proliferative phase of tendon healing (approximately 7 to 21 days post-injury), fibroblasts begin to synthesize a new extracellular matrix. Which collagen type predominates during this early phase of repair before being remodeled?

Explanation

During the early proliferative phase of tendon and ligament healing, the provisional matrix is primarily composed of Type III collagen. During the remodeling phase, this is gradually replaced by the stronger, more organized Type I collagen.

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