This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 10641
Topic: Infection, Pharmacology & VTE
According to the Kocher criteria, which of the following is NOT one of the classic four predictors for distinguishing septic arthritis from transient synovitis in a pediatric hip?
Correct Answer & Explanation
. C-reactive protein (CRP) > 2.0 mg/dL
Explanation
The original Kocher criteria include non-weight-bearing, ESR > 40, WBC > 12,000, and fever > 38.5 C. While CRP is an excellent inflammatory marker used extensively today, it was not part of the original four parameters defined by Kocher.
Question 10642
Topic: 1. General Principles & Basic Science
A patient undergoes a cemented total hip arthroplasty. During cement pressurization, the patient abruptly develops hypoxia, hypotension, and right heart strain. What is the most likely pathophysiologic mechanism?
Correct Answer & Explanation
. Bone cement implantation syndrome (BCIS)
Explanation
Bone cement implantation syndrome (BCIS) is characterized by hypoxia, hypotension, and potential cardiac arrest during cementation. It is primarily driven by high intramedullary pressure forcing fat, marrow, and cement particles into the venous circulation, leading to right ventricular failure.
Question 10643
Topic: Biology, Genetics & Bone Healing
When utilizing a plate for absolute stability in a transverse diaphyseal forearm fracture, the principle of dynamic compression achieves primary bone healing by which of the following mechanisms?
Correct Answer & Explanation
. Generating interfragmentary compression to allow direct Haversian remodeling
Explanation
Dynamic compression plating achieves absolute stability by applying interfragmentary compression across a simple fracture. This eliminates micromotion and abolishes the fracture gap, allowing primary (direct) bone healing via Haversian remodeling without callus formation.
Question 10644
Topic: 1. General Principles & Basic Science
A 30-year-old runner presents with lateral knee pain. Physical examination reveals tenderness over the lateral femoral epicondyle when the knee is cyclically flexed and extended. Which structure is most likely implicated?
Correct Answer & Explanation
. Iliotibial band
Explanation
Iliotibial (IT) band syndrome is characterized by pain over the lateral femoral epicondyle, where the IT band rubs during knee flexion and extension. It is a common overuse injury in runners and cyclists caused by friction at the epicondyle.
Question 10645
Topic: 1. General Principles & Basic Science
In the context of peripheral nerve injury, a Sunderland third-degree injury corresponds to which of the following anatomical descriptions?
Correct Answer & Explanation
. Axonal and endoneurial disruption with intact perineurium
Explanation
A Sunderland third-degree nerve injury involves the loss of continuity of the axons and the endoneurial tubes, but the perineurium remains intact. Recovery is unpredictable and often incomplete due to intrafascicular scarring disrupting axonal pathfinding.
Question 10646
Topic: Biology, Genetics & Bone Healing
Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction. Following the binding of BMP-2 to its cell surface receptor, which of the following intracellular signaling molecules is directly phosphorylated to propagate the osteogenic signal to the nucleus?
Correct Answer & Explanation
. Smad 1/5/8
Explanation
BMPs act through serine/threonine kinase cell surface receptors. Upon binding, the receptor phosphorylates receptor-regulated Smads (R-Smads), specifically Smad 1, 5, and 8. These then form a complex with the common-mediator Smad (Smad 4) and translocate to the nucleus to regulate target gene transcription. Beta-catenin is primarily involved in the Wnt signaling pathway, while JAK/STAT is utilized by cytokine receptors.
Question 10647
Topic: Biology, Genetics & Bone Healing
An 68-year-old man presents with progressive bowing of his tibiae and increasing head size. Radiographs demonstrate cortical thickening, trabecular coarsening, and mixed lytic-sclerotic lesions. Which of the following best describes the initial cellular event in the pathogenesis of this condition?
Correct Answer & Explanation
. Paramyxovirus-induced formation of abnormal, multinucleated osteoclasts
Explanation
Paget's disease of bone (osteitis deformans) begins with a markedly active osteoclastic (lytic) phase, characterized by massive, multinucleated osteoclasts containing viral-like inclusion bodies suspected to be paramyxovirus (such as RSV or measles). This intense resorption triggers a subsequent mixed osteoblastic/osteoclastic phase, and finally a dense but mechanically weak sclerotic phase. Monoclonal plasma cell proliferation describes Multiple Myeloma.
Question 10648
Topic: Biomechanics & Biomaterials
In orthopedic biomaterials, Young's modulus is a measure of a material's intrinsic stiffness. Which of the following lists represents the correct sequence of materials from highest to lowest Young's modulus (greatest to least stiffness)?
Young's modulus (elastic modulus) defines material stiffness in the linear elastic region. The correct order from stiffest to least stiff is: Ceramic (Alumina, ~380 GPa) > Cobalt-Chromium (~210 GPa) > Stainless Steel (~200 GPa) > Titanium alloy (~110 GPa) > Cortical bone (~15-20 GPa) > PMMA (~3 GPa) > Cancellous bone (0.1-2 GPa).
Question 10649
Topic: 1. General Principles & Basic Science
In evaluating normal articular cartilage, the distinct zones vary significantly in composition. Which of the following best characterizes the deep (radial) zone of normal articular cartilage?
Correct Answer & Explanation
. Highest concentration of proteoglycans and collagen fibers oriented perpendicular to the joint line
Explanation
Articular cartilage consists of four zones: superficial, middle (transitional), deep (radial), and calcified. The deep zone possesses the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers oriented perpendicular to the joint surface to effectively resist compressive forces. The superficial zone has the highest water content, lowest proteoglycan content, and parallel collagen fibers to resist shear.
Question 10650
Topic: Biology, Genetics & Bone Healing
A 10-year-old boy presents with progressive lower extremity varus bowing. Laboratory testing reveals low serum calcium, low serum phosphate, markedly elevated alkaline phosphatase, and elevated parathyroid hormone (PTH) levels. Which of the following is the primary physiological mechanism leading to this specific set of laboratory abnormalities?
Correct Answer & Explanation
. Inadequate dietary intake of Vitamin D leading to secondary hyperparathyroidism
Explanation
These laboratory findings are diagnostic for nutritional rickets (Vitamin D deficiency). The lack of Vitamin D reduces intestinal calcium absorption, triggering hypocalcemia and secondary hyperparathyroidism (elevated PTH). The high PTH initially corrects calcium levels via bone resorption but causes severe phosphaturia, leading to hypophosphatemia. PHEX mutation (X-linked hypophosphatemia) typically presents with normal serum calcium and normal PTH levels.
Question 10651
Topic: Surgical Anatomy & Approaches
During a volar approach to the forearm (Henry approach), the internervous plane in the proximal third of the forearm is developed between which of the following muscles?
Correct Answer & Explanation
. Brachioradialis and Pronator Teres
Explanation
The proximal Henry approach to the radius utilizes the internervous plane between the Brachioradialis (innervated by the Radial nerve) and the Pronator Teres (innervated by the Median nerve). Distally, the plane shifts to run between the Brachioradialis and the Flexor Carpi Radialis (Median nerve).
Question 10652
Topic: Infection, Pharmacology & VTE
Staphylococcus aureus is a predominant pathogen in periprosthetic joint infections. Its ability to form a robust biofilm is a key virulence factor. Which of the following molecules mediates the initial phase of biofilm formation, allowing S. aureus to adhere directly to host extracellular matrix proteins on the implant surface?
Biofilm formation involves initial attachment, accumulation/maturation, and dispersal. The initial attachment to biomaterials is mediated by MSCRAMMs, which bind to host proteins (like fibronectin and fibrinogen) that immediately coat the implant upon insertion. Polysaccharide intercellular adhesin (PIA) is crucial for the subsequent accumulation phase. Autoinducers regulate quorum sensing during the dispersal phase.
Question 10653
Topic: Biology, Genetics & Bone Healing
Osteolysis following total hip arthroplasty is primarily driven by a macrophage-induced foreign body reaction to particulate wear debris. Following phagocytosis of ultra-high molecular weight polyethylene (UHMWPE) particles, macrophages secrete cytokines that stimulate osteolysis via which of the following direct mechanisms?
Correct Answer & Explanation
. Upregulation of RANKL by osteoblasts leading to osteoclast activation
Explanation
Polyethylene wear particles are phagocytosed by local macrophages, which subsequently release pro-inflammatory cytokines such as TNF-alpha, IL-1, and IL-6. These cytokines stimulate local osteoblasts and fibroblasts to upregulate the expression of RANKL. RANKL then binds to RANK on osteoclast precursors, leading to aggressive osteoclast differentiation and massive localized bone resorption (osteolysis).
Question 10654
Topic: Biology, Genetics & Bone Healing
A 72-year-old female with severe postmenopausal osteoporosis is started on Romosozumab. This monoclonal antibody increases bone mass primarily by targeting and inhibiting which of the following proteins?
Correct Answer & Explanation
. Sclerostin
Explanation
Romosozumab is a monoclonal antibody that specifically binds to and inhibits sclerostin. Sclerostin is a glycoprotein secreted by mature osteocytes that normally inhibits the Wnt/beta-catenin signaling pathway, thereby reducing bone formation. By inhibiting sclerostin, Romosozumab exerts a unique dual effect: profoundly stimulating bone formation (osteoanabolic) while mildly decreasing bone resorption.
Question 10655
Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is widely used in orthopedic surgery to safely reduce perioperative blood loss. Which of the following best describes its pharmacological mechanism of action?
Correct Answer & Explanation
. Competitive inhibition of plasminogen activation to plasmin
Explanation
Tranexamic acid (TXA) is a synthetic analog of the amino acid lysine. It functions as an antifibrinolytic by reversibly and competitively binding to the lysine-binding sites on plasminogen. This prevents plasminogen from converting into active plasmin, thereby inhibiting the degradation of fibrin clots (fibrinolysis) and significantly reducing surgical bleeding.
Question 10656
Topic: Surgical Anatomy & Approaches
Following a closed humerus fracture, a patient develops a radial nerve palsy. Electromyography at 4 weeks shows active fibrillation potentials, and the nerve injury is determined to be a Sunderland Grade III. Which of the following neural connective tissue structures remains intact in this specific grade of injury?
Correct Answer & Explanation
. Perineurium
Explanation
In the Sunderland classification of nerve injury: Grade I = Neuropraxia (local myelin damage, no axon disruption). Grade II = Axonotmesis (axon disrupted, endoneurium intact). Grade III = Axon and endoneurium disrupted, perineurium intact. Grade IV = Axon, endoneurium, and perineurium disrupted, epineurium intact. Grade V = Neurotmesis (complete transection, epineurium disrupted). Thus, in Grade III, the perineurium remains intact.
Question 10657
Topic: Biomechanics & Biomaterials
Galvanic corrosion is a significant concern when dissimilar metals are implanted in the same physiological environment. If a stainless steel screw is placed through a titanium plate in an orthopedic construct, which of the following best describes the resulting electrochemical process?
Correct Answer & Explanation
. The stainless steel screw acts as the anode and corrodes rapidly
Explanation
Galvanic corrosion occurs when two dissimilar metals are in contact within an electrolyte solution (in vivo fluids). The less noble metal (lower on the galvanic series) becomes the anode and undergoes oxidation (corrosion), while the more noble metal becomes the protected cathode. Because titanium is more noble (more cathodic) than stainless steel, the stainless steel screw acts as the anode and will corrode.
Question 10658
Topic: Biology, Genetics & Bone Healing
Primary (direct) bone healing, characterized by cutting cones crossing the fracture site, requires an environment with which of the following biomechanical characteristics?
Correct Answer & Explanation
. Low strain (<2%) and absolute stability.
Explanation
Primary (direct) bone healing relies on Haversian remodeling with cutting cones. This mechanism requires absolute stability and an extremely low strain environment (<2%). If strain is higher, primary bone healing cannot occur, and the fracture will either undergo secondary healing with callus formation (if strain is between 2-10% and relative stability is provided) or go on to nonunion (if strain >10%).
Question 10659
Topic: Infection, Pharmacology & VTE
A 28-year-old farmer sustains a low-velocity gunshot wound to the thigh while hunting. The bullet did not hit the femur, but the entry wound is heavily contaminated with soil. According to orthopaedic principles for gunshot wounds, what is the most appropriate antibiotic prophylaxis?
Correct Answer & Explanation
. Intravenous Penicillin, Cefazolin, and Gentamicin
Explanation
For gunshot wounds heavily contaminated with soil, particularly in farm environments, there is a high risk of Clostridium infection. The standard antibiotic protocol for heavily contaminated or farm-related open fractures/GSWs is a first-generation cephalosporin (Cefazolin) plus an aminoglycoside (Gentamicin) for gram-negative coverage, with the mandatory addition of high-dose Penicillin to cover Clostridium species.
Question 10660
Topic: Biology, Genetics & Bone Healing
Bone Morphogenetic Proteins (BMPs) are utilized in orthopaedic surgery to stimulate bone healing. BMPs primarily exert their osteoinductive effects by binding to serine-threonine kinase receptors on the cell surface, which then directly phosphorylate and activate which of the following intracellular signaling pathways?
Correct Answer & Explanation
. Smad 1/5/8 pathway
Explanation
BMPs are members of the TGF-beta superfamily. They bind to type I and type II serine/threonine kinase receptors. Upon activation, these receptors phosphorylate intracellular receptor-regulated Smad proteins, specifically Smad 1, Smad 5, and Smad 8. These then form a complex with the co-Smad (Smad 4) and translocate to the nucleus to initiate transcription of osteogenic genes.
Test Yourself
Switch to an interactive, timed exam simulation to truly master this topic.