Updated Orthopedic Review | Dr Hutaif General Orthopedi -...

A 65-year-old patient presents with thigh pain 15 years after a primary cementless total hip arthroplasty. Radiographs show eccentric wear of the polyethylene liner and large osteolytic lesions in the proximal femur.

Which of the following macrophage pathways is most directly responsible for the massive osteolysis seen in this condition?

Which of the following cellular events most accurately differentiates primary (direct) bone healing from secondary (indirect) bone healing?

During the treatment of a midshaft femur fracture with a solid intramedullary nail, the surgeon selects a larger diameter implant. If the working length remains constant, increasing the radius of a solid intramedullary nail by a factor of 2 will increase its torsional rigidity by a factor of:

Tranexamic acid (TXA) is widely used in orthopedic surgery to reduce perioperative blood loss. Which of the following describes its primary molecular mechanism of action?

A 25-year-old male sustains an open tibia fracture following a motorcycle accident. The wound is 12 cm long with extensive periosteal stripping, requiring a rotational flap for soft tissue coverage.

According to standard guidelines for a Gustilo-Anderson Type IIIB fracture without farm/soil contamination, what is the most appropriate initial intravenous antibiotic regimen in the emergency department?

A 45-year-old male presents with severe low back pain, bilateral sciatica, and progressive sensory loss in his perineum. MRI confirms a massive central disc herniation at L4-L5. Which of the following findings is considered the most sensitive early clinical indicator for establishing the diagnosis of Cauda Equina Syndrome?

A 4-year-old child presents with a painful limp and refusal to bear weight on the right leg. Vitals show a temperature of 38.6°C (101.5°F). Laboratory analysis reveals a WBC count of 13,000/mm³ and an ESR of 45 mm/hr. According to the Kocher criteria, what is the approximate probability that this child has septic arthritis of the hip?

A 62-year-old female with breast cancer presents with right thigh pain described as severe and limiting her mobility (functional pain). Radiographs show a purely lytic lesion in the peritrochanteric region of the right femur, occupying 75% of the cortical diameter. What is her calculated Mirels' score, and what is the standard recommendation?

A 24-year-old athlete sustains a hyper-plantarflexion injury to his midfoot.

A Lisfranc injury is suspected. The primary stabilizing ligament of the Lisfranc joint complex connects which two bones?

A 70-year-old man presents with increasing hat size, hearing loss, and deep, aching bone pain in his right tibia. Radiographs reveal cortical thickening and coarsened trabeculae. Which of the following histological findings is a hallmark of the active or mixed phase of this disease?

Which of the following compartments of the hand is most frequently involved in compartment syndrome secondary to severe crush injuries, and which nerve provides primary motor innervation to the muscles contained within it?

In Total Hip Arthroplasty (THA), ceramic-on-ceramic (CoC) bearing surfaces offer the lowest wear rates among conventional options. Which of the following is a recognized complication uniquely and specifically associated with CoC bearings compared to metal-on-polyethylene (MoP) bearings?

A patient sustains a closed midshaft humerus fracture resulting in a radial nerve palsy. According to Seddon's classification of nerve injuries, a neurapraxia is characterized by which of the following?

During the arthroscopic repair of a massive rotator cuff tear, preserving the 'suspensory cable' of the shoulder is deemed critical for mechanical function. The rotator cable is a thick, fibrous bundle that extends primarily between which two structures?

A 14-year-old boy presents with a painful, swollen distal thigh. Radiographs demonstrate a 'sunburst' periosteal reaction and a Codman's triangle in the distal femoral metaphysis. A biopsy confirms osteosarcoma. Which of the following genetic alterations is most frequently associated with the pathogenesis of this tumor?

In the Young-Burgess classification of pelvic ring injuries, an Anterior Posterior Compression Type II (APC II) injury is defined by the widening of the symphysis pubis and the disruption of which of the following posterior pelvic structures?

Osteoclasts attach tightly to the bone surface via specialized structures called sealing zones, creating an isolated acidic microenvironment for bone resorption. Which integrin is primarily responsible for osteoclast attachment to bone matrix proteins such as osteopontin?

A 13-year-old obese male presents with a 3-week history of left groin and knee pain. He walks with an antalgic limp and externally rotates the left leg during the swing phase. On physical exam, as the left hip is flexed, it obligatorily externally rotates. Radiographs confirm a Slipped Capital Femoral Epiphysis (SCFE). In which direction does the proximal femoral epiphysis anatomically displace relative to the femoral neck?

A 22-year-old male falls onto an outstretched hand and sustains a proximal pole scaphoid fracture. Which of the following anatomical features best explains the high rate of avascular necrosis (AVN) and nonunion associated with fractures in this specific region of the carpus?

During reconstruction of the Anterior Cruciate Ligament (ACL), the surgeon places the femoral tunnel too anteriorly (i.e., too high and shallow in the intercondylar notch). What is the primary clinical consequence of this specific technical error?

A 65-year-old woman presents with vague thigh pain for the past 3 weeks. She has been on alendronate for 8 years for osteoporosis. A radiograph of her femur is obtained. Which of the following radiographic findings constitutes an absolute indication for prophylactic intramedullary fixation of an impending atypical femur fracture?

A 24-year-old man presents with chronic wrist pain and weakness following a fall onto an outstretched hand 6 months ago. The corresponding MRI reveals findings consistent with avascular necrosis (AVN) of the carpal bone shown. The blood supply to the proximal pole of this bone primarily enters via which of the following structures?

A 55-year-old man undergoes a biopsy of a destructive proximal humerus lesion that demonstrated endosteal scalloping and soft tissue extension on MRI. Histopathology demonstrates hypercellular cartilage with nuclear pleomorphism and binucleate cells in a myxoid stroma. Which of the following is the most appropriate definitive management for a Grade 2 lesion of this type?

In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced the incidence of wear and subsequent osteolysis compared to conventional polyethylene. However, the radiation process used to improve cross-linking most directly results in which of the following mechanical trade-offs?

A 60-year-old man presents with severe groin pain and a large soft-tissue mass 5 years after an uncomplicated primary metal-on-polyethylene total hip arthroplasty. Laboratory studies show markedly elevated serum cobalt levels and normal chromium levels. Which of the following is the most likely source of the metal debris generating this adverse local tissue reaction?

According to the Levine and Edwards classification of traumatic spondylolisthesis of the axis (Hangman's fracture), a Type IIA fracture pattern requires extreme caution during non-operative management because it is characterized by which of the following?

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

Following an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, the graft tissue undergoes a biologic process known as creeping substitution. What is the correct chronological order of the healing phases during this incorporation process?

The Sanders classification system for intra-articular calcaneus fractures dictates prognosis and guides surgical management. This classification is primarily based on the fracture line pattern assessed using which of the following specific imaging views?

Charcot neuroarthropathy is a devastating complication in patients with long-standing diabetes mellitus. Which of the following pathophysiologic mechanisms best describes the 'neurovascular theory' of Charcot arthropathy development?

Histologically, normal articular cartilage is divided into four distinct zones. Which zone is characterized by the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers arranged perpendicular to the articular surface?

A 14-year-old boy presents with a diaphyseal mass in the femur. Radiographs reveal a permeative destructive lesion with an 'onion-skin' periosteal reaction. Genetic testing of the biopsy specimen is most likely to reveal which of the following chromosomal translocations?

In a posterior-stabilized (PS) total knee arthroplasty, the post-cam mechanism engages to substitute for the function of the excised posterior cruciate ligament (PCL). In a standard PS design, during which phase of knee range of motion does the femoral cam typically engage the tibial post?

Following a primary Zone II flexor tendon repair in the hand, the patient is started on an early active motion protocol. Which of the following technical factors has the greatest impact on the tensile strength of the repair and its resistance to gap formation during early active motion?

A 68-year-old man presents with bilateral leg pain when walking. Differentiating neurogenic claudication (lumbar spinal stenosis) from vascular claudication can be clinically challenging. Which of the following historical findings is most specific for a diagnosis of neurogenic claudication?

When correcting idiopathic clubfoot (talipes equinovarus) using the Ponseti method of serial casting, what is the correct physiological sequence in which the individual deformity components must be addressed?

A patient treated with a volar locking plate for a distal radius fracture 3 months ago now presents with the inability to actively flex the interphalangeal joint of the thumb. Which of the following technical errors during the index surgery is the most likely cause of this complication?

In the preoperative evaluation of recurrent anterior shoulder instability, the 'glenoid track' concept is utilized to predict failure of isolated soft tissue stabilization. A bipolar bone loss lesion is considered 'off-track' if which of the following is true?

Which of the following internal fixation constructs provides absolute stability, thereby predominantly resulting in primary (direct) bone healing without the formation of a visible cartilaginous fracture callus?

A 22-year-old collegiate football player sustains an acute midfoot injury when tackled with his foot plantarflexed. An AP weight-bearing radiograph reveals a small osseous avulsion in the space between the base of the first and second metatarsals ('fleck sign'). This represents an avulsion of the Lisfranc ligament, which anatomically connects which two bones?

During a revision open reduction and internal fixation of a nonunion, a surgeon considers supplementing an existing titanium alloy (Ti-6Al-4V) intramedullary nail with stainless steel (316L) cerclage wires. If these two different metals are placed in direct physical contact within the corrosive physiological environment of the human body, which of the following is the most likely biomechanical or biochemical consequence?

A 15-year-old boy presents with right knee pain and swelling for two months. Radiographs demonstrate an aggressive, mixed lytic and blastic lesion in the distal femoral metaphysis with a 'sunburst' periosteal reaction.

A biopsy is performed. Which of the following histologic features is the sine qua non for the diagnosis of this patient's most likely condition?

A surgeon utilizes a locked plating construct to bridge a highly comminuted diaphyseal fracture of the tibia. During preoperative planning, the surgeon decides to leave three empty screw holes directly over the fracture site instead of one. How does increasing the working length of this locked plate construct affect its biomechanical properties?

A 45-year-old female with a history of malabsorption secondary to Crohn's disease presents with diffuse, dull bone pain and proximal muscle weakness. Laboratory studies reveal low serum calcium, low phosphorus, and elevated alkaline phosphatase. A bone biopsy reveals thickened, unmineralized osteoid seams. Which of the following represents the primary pathophysiologic defect in this condition?

Periprosthetic joint infections caused by Staphylococcus epidermidis are notoriously difficult to eradicate due to biofilm formation. During the accumulation/proliferation phase of biofilm development, which of the following molecules mediates the critical cell-to-cell adhesion and structural integrity of the extracellular polymeric substance?

Tranexamic acid (TXA) is routinely utilized in total joint arthroplasty to reduce perioperative blood loss. Which of the following best describes the specific mechanism of action of this pharmacological agent?

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

A 4-year-old boy presents with disproportionate short stature, frontal bossing, and rhizomelic shortening of the limbs.

Genetic testing confirms a gain-of-function mutation in the FGFR3 gene. The cellular defect associated with this genetic abnormality primarily occurs in which zone of the physis?

A patient with severe right hip osteoarthritis is advised by his physical therapist to use a cane during ambulation to relieve pain.

When the cane is properly held in the contralateral (left) hand, which of the following best explains the biomechanical mechanism by which the joint reaction force across the right hip is reduced?

Romosozumab is a monoclonal antibody recently developed for the treatment of severe osteoporosis. It functions by binding to and inhibiting sclerostin, thereby activating the Wnt/β-catenin signaling pathway to stimulate bone formation. Under normal physiologic conditions, sclerostin is primarily synthesized and secreted by which of the following cell types?

Which of the following modifications to a cortical screw design will most significantly increase its pullout strength in cortical bone?

A 68-year-old osteoporotic woman is prescribed a biologic agent that mimics the body's natural osteoprotegerin (OPG). Which of the following best describes the specific mechanism of action of this medication?

During the evaluation of normal articular cartilage, which zone is characterized by the highest concentration of proteoglycans, the lowest water content, and collagen fibers oriented perpendicular to the joint surface?

A patient on long-term alendronate therapy sustains an atypical subtrochanteric femur fracture. Bisphosphonates such as alendronate reduce bone resorption primarily by inhibiting which of the following enzymes in the mevalonate pathway?

A 45-year-old malnourished patient presents with impaired wound healing and spontaneous bleeding gums. A deficiency in vitamin C is diagnosed. This deficiency directly impairs collagen synthesis by limiting the function of which of the following?

When applying a bridging locking plate for a comminuted diaphyseal fracture, increasing the 'working length' (leaving more empty screw holes over the fracture site) will have which of the following biomechanical effects on the construct?

A 14-year-old boy presents with a diaphyseal mass in his femur. Biopsy reveals small round blue cells. Molecular testing is expected to show an EWS-FLI1 fusion protein resulting from which of the following chromosomal translocations?

During a bilateral total knee arthroplasty, the surgeon administers intravenous tranexamic acid (TXA) to reduce perioperative blood loss. What is the mechanism of action of this agent?

A 10-year-old child sustains a Salter-Harris Type II fracture of the distal radius. The fracture line through the physis primarily propagates through which specific cellular layer?

To reduce wear rates in total joint arthroplasty, ultra-high molecular weight polyethylene (UHMWPE) undergoes highly cross-linking. To prevent in vivo oxidation and premature degradation, the cross-linked UHMWPE must be subjected to which of the following processes?

A surgeon applies a stainless steel plate to a femur fracture and secures it using titanium alloy screws. This mixing of dissimilar metals primarily increases the risk of which type of corrosion?

A new rapid diagnostic test for periprosthetic joint infection is evaluated in a specialized tertiary orthopedic center with a high infection rate and a community hospital with a very low infection rate. Which of the following statistical values for the test will be significantly higher at the tertiary center?

In the pathogenesis of orthopedic implant infections, bacteria form a mature biofilm that makes them highly resistant to systemic antibiotics and host immune defenses. The structural integrity and protective barrier of this biofilm are primarily provided by which of the following?

A 19-year-old male presents with night pain in his tibia that is dramatically relieved by NSAIDs. Radiographs show a small radiolucent nidus surrounded by dense sclerotic bone. The dramatic pain relief provided by NSAIDs is due to the inhibition of which molecule highly produced by this lesion?

During a spinal fusion, a surgeon decides to use demineralized bone matrix (DBM) to supplement local autograft. Which of the following best describes the bone healing properties inherent to commercially available DBM?

During skeletal muscle contraction, an action potential triggers the release of calcium ions from the sarcoplasmic reticulum. The direct binding of these calcium ions to which of the following proteins initiates the cross-bridge cycle?

A high-velocity gunshot wound to the thigh causes massive soft tissue destruction and a comminuted femur fracture. According to the principles of ballistics, which factor is most responsible for the kinetic energy transferred to the patient's tissues?

The alpha chains of Type I collagen form a rigid triple helix. This structural conformation is exclusively possible because every third amino acid in the primary sequence is universally which of the following?

Following a severe traction injury to the brachial plexus, a patient undergoes evaluation for nerve continuity. In an axonotmesis injury, distal axonal degeneration occurs over several days. Which cell type is primarily responsible for clearing the myelin debris in the peripheral nervous system during this process?

Which of the following cellular markers or transcription factors is considered the master regulator required for mesenchymal stem cells to differentiate into the osteoblast lineage?

The pullout strength of a cortical screw is a critical factor in achieving stable internal fixation. Based on the standard mathematical formula for screw pullout strength, which of the following design parameters is directly proportional to the pullout resistance?

A surgeon is revising a nonunion and plans to use a combination of implants. To minimize the risk of clinically significant galvanic corrosion, which of the following combinations of metals should be strictly avoided in direct contact?

Following the placement of a massive cortical structural allograft for a segmental bone defect, what is the primary mechanism of graft incorporation and its initial mechanical consequence?

In adult articular cartilage, which of the following statements best describes the specific biochemical and structural characteristics of the superficial (tangential) zone?

Parathyroid hormone (PTH) plays a key role in systemic calcium homeostasis. PTH stimulates osteoclastic bone resorption primarily through which of the following cellular mechanisms?

When applying a bridging plate to a highly comminuted diaphyseal fracture, how does decreasing the working length of the plate (placing the innermost screws closer to the fracture site) alter the biomechanics of the construct?

In the pathogenesis of periprosthetic joint infection, biofilm formation is a critical factor in antibiotic resistance. Which of the following best describes the function of "quorum sensing" in this process?

According to the Sunderland classification of peripheral nerve injuries, a Grade III injury is anatomically characterized by the specific disruption of which of the following structures?

The introduction of highly cross-linked polyethylene (HXLPE) in total hip arthroplasty has drastically reduced volumetric wear rates. However, increasing the radiation dose to achieve higher levels of cross-linking predominantly compromises which mechanical property?

Administration of non-steroidal anti-inflammatory drugs (NSAIDs) shortly after a fracture can impair bone healing primarily by inhibiting cyclooxygenase-2 (COX-2). Which specific stage of fracture repair is most adversely affected by this COX-2 inhibition?

Stress shielding around a stiff orthopedic implant can lead to localized osteopenia. Which of the following solid metallic implant materials possesses an elastic modulus most closely approximating that of human cortical bone?

A 65-year-old patient is prescribed rivaroxaban for deep vein thrombosis prophylaxis following a primary total knee arthroplasty. What is the precise mechanism of action of this pharmacological agent?

During a minor orthopedic procedure under local anesthesia, a 70 kg patient inadvertently receives an intravascular injection of bupivacaine. To avoid severe cardiotoxicity, what is the generally accepted maximum safe dose of bupivacaine with epinephrine for this patient?

To minimize personal scatter radiation exposure when using a C-arm fluoroscope in the lateral position during fracture fixation, where is the optimal location for the surgeon to stand?

In the destructive joint changes characteristic of osteoarthritis, which of the following matrix metalloproteinases (MMPs) is primarily recognized as the major collagenase responsible for the cleavage of Type II collagen?

An orthopedic surgeon is deciding between two plates of the same width but different thicknesses for a fracture fixation. If the thickness of the plate is doubled while the width remains constant, its bending rigidity increases by a factor of:

Which of the following accurately describes the primary mechanism by which Denosumab affects bone remodeling in the treatment of osteoporosis or giant cell tumor of bone?

What is the primary mechanical trade-off associated with the use of highly cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) compared to conventional UHMWPE in total hip arthroplasty?

A patient sustains a closed midshaft humerus fracture and presents with a dense radial nerve palsy. Electromyography at 4 weeks shows fibrillation potentials but no motor unit action potentials. If the nerve injury is classified as a Sunderland Grade II (axonotmesis), what key histological structure remains intact to allow for predictable axonal regeneration?

A 60-year-old male presents with new-onset, severe thigh pain. Radiographs reveal a central, stippled calcified lesion in the proximal femur with an associated large, radiolucent, destructive soft-tissue mass extending beyond the cortex. Biopsy of the soft-tissue mass shows a high-grade spindle cell sarcoma. What is the most likely diagnosis?

In normal adult articular cartilage, which zone is characterized by the highest concentration of proteoglycans, the largest diameter collagen fibrils oriented perpendicularly to the joint surface, and chondrocytes arranged in vertical columns?

During an anterior cruciate ligament (ACL) reconstruction, the surgeon pre-tensions the soft-tissue graft by securing it on a board and holding it at a constant length for 10 minutes. The surgeon notes that the tension required to maintain this specific length gradually decreases over time. This biomechanical phenomenon is known as:

Tranexamic acid (TXA) is frequently used in orthopedic surgery to reduce perioperative blood loss. Which of the following accurately describes the specific molecular mechanism of action of TXA?

During the pathogenesis of a periprosthetic joint infection, Staphylococcus aureus utilizes surface proteins to adhere to host proteins that have coated an orthopedic implant. What is the initial, prerequisite step in biofilm formation before irreversible attachment occurs?

A surgeon is utilizing a locking compression plate (LCP) for a highly comminuted distal femur fracture, planning for secondary bone healing. Which of the following modifications to the construct will most effectively decrease construct stiffness and promote beneficial callus formation?