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1. General Principles & Basic Science MCQs

Practice Set 524 of 789

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 10461

Topic: Infection, Pharmacology & VTE

A 6-year-old child presents with a painful swollen left knee and fever. Labs show elevated ESR and CRP, and a white blood cell count of 18,000/uL. Aspiration of the knee joint yields cloudy fluid with a WBC count of 75,000/uL, 90% neutrophils, and positive Gram stain for Staphylococcus aureus. What is the immediate next step in management?

. Start oral antibiotics and observe
. Apply a splint and continue observation
. Perform emergent surgical irrigation and debridement of the joint, followed by intravenous antibiotics
. Administer anti-inflammatory drugs
. Order an MRI of the knee

Correct Answer & Explanation

. Perform emergent surgical irrigation and debridement of the joint, followed by intravenous antibiotics

Explanation

This clinical scenario, lab findings, and joint fluid analysis are diagnostic of septic arthritis. Septic arthritis is an orthopedic emergency, especially in children, due to the rapid destruction of articular cartilage. The immediate next step is emergent surgical irrigation and debridement of the joint (often arthroscopic in larger joints like the knee), followed by appropriate intravenous antibiotics. Delay can lead to irreversible joint damage. Oral antibiotics are insufficient, and MRI, while helpful, is not the immediate therapeutic intervention.

Question 10462

Topic: Biology, Genetics & Bone Healing

What is the characteristic histological finding in Paget's disease of bone?

. Decreased osteoclast activity
. Increased mineralization of osteoid
. Mosaic pattern of lamellar bone
. Numerous osteophytes at joint margins
. Presence of 'brown tumors'

Correct Answer & Explanation

. Mosaic pattern of lamellar bone

Explanation

Paget's disease of bone is characterized by a disorganized and accelerated remodeling process. Histologically, this leads to a 'mosaic' or 'jigsaw puzzle' pattern of lamellar bone due to haphazard deposition of new bone. It involves increased osteoclast activity followed by increased and disorganized osteoblast activity. Brown tumors are seen in hyperparathyroidism. Osteophytes are seen in osteoarthritis.

Question 10463

Topic: Infection, Pharmacology & VTE

A 50-year-old female presents with severe pain and swelling in the first metatarsophalangeal (MTP) joint, which started suddenly last night. Examination reveals a red, hot, swollen, and exquisitely tender joint. Labs show elevated serum uric acid. What is the most appropriate initial management?

. Initiate allopurinol immediately
. Administer intra-articular steroid injection
. Start a course of colchicine or NSAIDs
. Advise rest and elevation only
. Perform surgical debridement of the joint

Correct Answer & Explanation

. Start a course of colchicine or NSAIDs

Explanation

The clinical presentation (acute monoarticular arthritis, severe inflammation, elevated uric acid) is highly suggestive of acute gout. The most appropriate initial management for an acute gout attack is to rapidly reduce inflammation and pain. This is typically achieved with colchicine, NSAIDs (e.g., indomethacin), or oral corticosteroids. Allopurinol is a uric acid-lowering therapy used for long-term management to prevent future attacks, but it should not be started during an acute attack as it can worsen symptoms. Intra-articular steroid injection can be considered for isolated joint involvement but is often used if oral medications are contraindicated. Surgical debridement is not indicated.

Question 10464

Topic: Biology, Genetics & Bone Healing

A 70-year-old female with severe osteoporosis sustains a fragility fracture of the distal radius. Which of the following is the most appropriate long-term pharmacological agent to reduce future fracture risk?

. Calcium and Vitamin D supplementation alone
. Bisphosphonates (e.g., Alendronate)
. NSAIDs
. Oral corticosteroids
. Estrogen replacement therapy (ERT) alone

Correct Answer & Explanation

. Bisphosphonates (e.g., Alendronate)

Explanation

For a patient with a fragility fracture and severe osteoporosis, bisphosphonates (e.g., Alendronate, Risedronate, Zoledronic acid) are the first-line pharmacological agents to significantly reduce the risk of future fractures by inhibiting osteoclast activity. Calcium and Vitamin D supplementation are essential adjuncts but often insufficient alone for severe osteoporosis. NSAIDs are for pain relief, not fracture prevention. Oral corticosteroids can worsen osteoporosis. ERT can be used, but bisphosphonates are generally preferred as first-line for primary osteoporosis treatment due to their efficacy and broader applicability, especially given the age and fracture history.

Question 10465

Topic: 1. General Principles & Basic Science

Which of the following describes the typical clinical presentation of a patient with a posterior hip dislocation?

. Hip adducted, internally rotated, and flexed
. Hip abducted, externally rotated, and flexed
. Hip adducted, externally rotated, and extended
. Hip abducted, internally rotated, and extended
. Hip in neutral rotation and extension

Correct Answer & Explanation

. Hip adducted, internally rotated, and flexed

Explanation

Posterior hip dislocations, the most common type, typically result from a dashboard injury in MVCs. The classic presentation is a shortened limb, with the hip held in a position of adduction, internal rotation, and flexion. Anterior hip dislocations present with abduction and external rotation.

Question 10466

Topic: Infection, Pharmacology & VTE

What is the most common organism causing osteomyelitis in healthy children?

. Escherichia coli
. Streptococcus pyogenes
. Pseudomonas aeruginosa
. Staphylococcus aureus
. Haemophilus influenzae

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is the most common causative organism for acute hematogenous osteomyelitis in healthy children and adults across all age groups. E. coli and Pseudomonas are more common in specific scenarios (e.g., genitourinary infections, IV drug users, puncture wounds through shoes). S. pyogenes is less common, and H. influenzae was more common before widespread vaccination.

Question 10467

Topic: Infection, Pharmacology & VTE

A patient presents with a painful snapping sensation on the medial side of the knee during flexion and extension. Palpation reveals tenderness over the medial tibial condyle just distal to the joint line. What is the most likely diagnosis?

. Medial meniscus tear
. MCL injury
. Pes anserine bursitis
. Patellofemoral pain syndrome
. Osteoarthritis of the medial compartment

Correct Answer & Explanation

. Pes anserine bursitis

Explanation

The symptoms (painful snapping, tenderness on the medial tibial condyle just distal to the joint line) are characteristic of pes anserine bursitis. This condition involves inflammation of the bursa located deep to the conjoined tendons of the sartorius, gracilis, and semitendinosus muscles (the pes anserinus). Medial meniscus tears usually cause pain directly at the joint line. MCL injury involves tenderness over the ligament. Patellofemoral pain is anterior knee pain. OA would have broader symptoms.

Question 10468

Topic: Biology, Genetics & Bone Healing

What is the primary role of Vitamin D in bone health?

. Directly stimulates osteoblast activity
. Increases calcium excretion by the kidneys
. Promotes intestinal absorption of calcium and phosphate
. Inhibits parathyroid hormone secretion
. Acts as a cofactor for collagen synthesis

Correct Answer & Explanation

. Promotes intestinal absorption of calcium and phosphate

Explanation

The primary role of Vitamin D (specifically its active form, calcitriol) in bone health is to promote the intestinal absorption of calcium and phosphate. This ensures adequate mineral availability for bone mineralization. It also has effects on osteoblasts and osteoclasts, and PTH regulation, but its main direct action is on gut absorption.

Question 10469

Topic: Infection, Pharmacology & VTE

A 5-year-old child presents with a high fever, refusal to bear weight on the right leg, and exquisite tenderness over the distal femur metaphysis. Blood cultures grow methicillin-sensitive Staphylococcus aureus. Radiographs are normal. What is the most appropriate next step?

. MRI of the right femur
. Bone scan
. Start intravenous antibiotics immediately
. Surgical drainage of the femur
. Repeat radiographs in 1 week

Correct Answer & Explanation

. Start intravenous antibiotics immediately

Explanation

This is a classic presentation of acute osteomyelitis in a child (fever, localized bone pain, refusal to bear weight, positive blood cultures, normal initial radiographs). Given the high suspicion and positive blood cultures, immediate initiation of appropriate intravenous antibiotics is crucial to treat the infection and prevent bone destruction. Radiographs may be normal early in the course (before 7-10 days). MRI or bone scan can help localize the lesion but starting antibiotics should not be delayed. Surgical drainage is indicated if there is an abscess or no response to antibiotics, but not as the initial step after positive blood cultures.

Question 10470

Topic: Surgical Anatomy & Approaches

Which nerve is most commonly injured with a midshaft humerus fracture?

. Median nerve
. Ulnar nerve
. Radial nerve
. Axillary nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

The radial nerve courses in the spiral groove along the posterior aspect of the humerus shaft, making it highly susceptible to injury during midshaft humerus fractures. Injury can result in wrist drop and sensory deficits on the dorsum of the hand. The median and ulnar nerves are more medially located, and the axillary nerve is more proximal.

Question 10471

Topic: Infection, Pharmacology & VTE

A patient with a history of intravenous drug use presents with acute onset fever and severe back pain localized to the lumbar spine. MRI shows signal changes consistent with discitis and osteomyelitis at L3-L4. What is the most appropriate initial management?

. Physical therapy and pain management
. Immediate surgical debridement
. Biopsy for culture and histology, followed by empiric intravenous antibiotics
. Oral NSAIDs and observation
. Spinal bracing alone

Correct Answer & Explanation

. Biopsy for culture and histology, followed by empiric intravenous antibiotics

Explanation

Given the history of IV drug use and MRI findings consistent with discitis and osteomyelitis, an infection is highly probable. The most appropriate initial management is to obtain a biopsy (either CT-guided percutaneous or open) for culture and histology to identify the causative organism, followed by empiric intravenous antibiotics. Surgical debridement may be necessary later if conservative measures fail or neurological compromise develops, but direct identification of the pathogen is crucial for targeted therapy. Physical therapy, NSAIDs, observation, or bracing alone are insufficient for an active spinal infection.

Question 10472

Topic: Infection, Pharmacology & VTE

In a patient with a displaced femoral neck fracture, what is the most significant risk associated with delaying definitive surgical fixation?

. Increased pain
. Increased risk of deep vein thrombosis (DVT)
. Increased risk of non-union and avascular necrosis (AVN) of the femoral head
. Increased blood loss
. Increased risk of infection

Correct Answer & Explanation

. Increased risk of non-union and avascular necrosis (AVN) of the femoral head

Explanation

Delayed definitive surgical fixation of a displaced femoral neck fracture significantly increases the risk of complications, particularly non-union and avascular necrosis (AVN) of the femoral head. This is because the blood supply to the femoral head, which is already tenuous, is further compromised by the fracture and prolonged displacement. While other complications like pain and DVT are also concerns, the risk to the femoral head's viability is paramount and time-sensitive.

Question 10473

Topic: Biology, Genetics & Bone Healing
During the process of secondary fracture healing, a cartilaginous soft callus forms to bridge the fracture gap. Which type of collagen is the predominant structural component of this early soft callus phase?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type II collagen

Explanation

Secondary fracture healing proceeds through hematoma formation, fibrocartilaginous (soft) callus, bony (hard) callus, and remodeling. The soft callus is primarily composed of cartilage, which is rich in Type II collagen. As endochondral ossification progresses, Type X collagen is expressed by hypertrophic chondrocytes, followed by the deposition of Type I collagen as woven bone is formed.

Question 10474

Topic: Biology, Genetics & Bone Healing

A 70-year-old woman is started on denosumab for the treatment of severe osteoporosis. What is the specific mechanism of action of this medication?

. Directly induces osteoclast apoptosis
. Binds to RANKL, preventing it from interacting with the RANK receptor
. Binds directly to the RANK receptor, antagonizing its activation
. Increases the endogenous production of osteoprotegerin (OPG)
. Inhibits the osteoclast ruffled border by targeting carbonic anhydrase II

Correct Answer & Explanation

. Binds to RANKL, preventing it from interacting with the RANK receptor

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). By binding to RANKL, it prevents RANKL from interacting with the RANK receptor on osteoclasts and their precursors, thereby inhibiting osteoclast formation, function, and survival.

Question 10475

Topic: Infection, Pharmacology & VTE

While Staphylococcus aureus is the most common overall cause of acute hematogenous osteomyelitis, patients with sickle cell disease have a uniquely higher incidence of infection caused by which of the following organisms compared to the general population?

. Staphylococcus epidermidis
. Salmonella species
. Haemophilus influenzae
. Streptococcus pneumoniae
. Pseudomonas aeruginosa

Correct Answer & Explanation

. Salmonella species

Explanation

In patients with sickle cell disease, functional asplenia and bone infarcts (which can serve as a nidus for infection) predispose them to osteomyelitis. While S. aureus is still extremely common, Salmonella species are uniquely associated with osteomyelitis in sickle cell patients and account for a significantly higher percentage of cases than in healthy individuals.

Question 10476

Topic: Biomechanics & Biomaterials

During intraoperative ACL reconstruction tensioning, the graft is held at a constant length. Over time, the surgeon notes a gradual decrease in the force required to maintain this specific length. This viscoelastic property is known as:

. Stress relaxation
. Creep
. Hysteresis
. Fatigue failure
. Anisotropy

Correct Answer & Explanation

. Stress relaxation

Explanation

Stress relaxation is the decrease in stress (force) over time when a viscoelastic material is held at a constant strain (length). Creep is the continuous deformation (increase in length) over time when a material is subjected to a constant stress (load). Hysteresis refers to the energy lost as heat during the loading and unloading cycle.

Question 10477

Topic: Biology, Genetics & Bone Healing

A 65-year-old man presents with dull, aching bone pain, increasing head size, and progressive hearing loss. A biopsy of his affected bone is shown below.

If the histology demonstrates haphazardly arranged cement lines creating a 'mosaic' pattern, what is the most likely diagnosis?

. Osteomalacia
. Paget's disease of bone
. Osteogenesis imperfecta
. Fibrous dysplasia
. Primary hyperparathyroidism

Correct Answer & Explanation

. Paget's disease of bone

Explanation

Paget's disease of bone (osteitis deformans) is characterized by a focal increase in bone remodeling. In the late (osteosclerotic) phase, disorganized woven and lamellar bone is laid down, creating a classic 'mosaic' pattern with prominent, haphazard cement lines. Clinical features include bone pain, bowing deformities, increasing skull size, and cranial nerve impingement (e.g., hearing loss).

Question 10478

Topic: 1. General Principles & Basic Science

Normal articular cartilage is highly specialized to resist compressive loads. Which zone of articular cartilage contains the highest water content, the lowest proteoglycan concentration, and collagen fibrils aligned parallel to the joint surface?

. Superficial (tangential) zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified zone
. Tidemark

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial (tangential) zone of articular cartilage has the highest water content (up to 80%) and the lowest concentration of proteoglycans. Its collagen fibers (primarily Type II) are aligned parallel to the articular surface to resist shear forces.

Question 10479

Topic: Biology, Genetics & Bone Healing

Vitamin C deficiency (scurvy) results in weakened connective tissue, bone pain, and mucosal bleeding. At a cellular level, Vitamin C acts as an essential cofactor for which of the following steps in collagen synthesis?

. Hydroxylation of proline and lysine residues
. Cleavage of registration peptides from procollagen
. Cross-linking of tropocollagen by lysyl oxidase
. Glycosylation of hydroxylysine residues
. Formation of the triple helix structure

Correct Answer & Explanation

. Hydroxylation of proline and lysine residues

Explanation

Vitamin C (ascorbic acid) is a crucial cofactor for the enzymes prolyl hydroxylase and lysyl hydroxylase, which add hydroxyl groups to proline and lysine residues on the preprocollagen chains. This hydroxylation is required for the subsequent stable formation of the collagen triple helix.

Question 10480

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman sustains a distal radius fracture after a low-energy fall. DEXA scanning reveals a T-score of -2.8 at the femoral neck. In primary osteoporosis, which of the following best describes the typical serum laboratory profile for calcium, phosphate, and alkaline phosphatase (ALP)?

. Normal Calcium, Normal Phosphate, Normal ALP
. High Calcium, Low Phosphate, High ALP
. Low Calcium, Low Phosphate, High ALP
. Normal Calcium, Normal Phosphate, High ALP
. High Calcium, Normal Phosphate, Normal ALP

Correct Answer & Explanation

. Normal Calcium, Normal Phosphate, Normal ALP

Explanation

Primary osteoporosis is characterized by low bone mass and microarchitectural deterioration, but routine serum chemistries (Calcium, Phosphate, Alkaline Phosphatase) are classically within normal limits. Abnormalities in these labs should prompt investigation for secondary causes such as osteomalacia, hyperparathyroidism, or Paget's disease.

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