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1. General Principles & Basic Science MCQs

Practice Set 51 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 1001

Topic: Infection, Pharmacology & VTE

An 80-year-old woman undergoes urgent hemiarthroplasty for a displaced femoral neck fracture. Her past medical history is significant for end-stage renal disease (eGFR 12 mL/min). Which of the following deep vein thrombosis (DVT) prophylaxis regimens is most appropriate?

. Enoxaparin 40 mg subcutaneous daily
. Rivaroxaban 10 mg oral daily
. Unfractionated heparin 5000 units subcutaneous TID
. Fondaparinux 2.5 mg subcutaneous daily
. Dabigatran 110 mg oral daily

Correct Answer & Explanation

. Unfractionated heparin 5000 units subcutaneous TID

Explanation

Unfractionated heparin is not renally cleared and is considered safe in patients with severe renal impairment (eGFR < 15 mL/min). Low-molecular-weight heparins (like enoxaparin) and most NOACs require strict renal dose adjustment or are entirely contraindicated.

Question 1002

Topic: Biomechanics & Biomaterials

A researcher is evaluating an orthopedic implant made of a titanium alloy. During mechanical testing, the material is loaded into its elastic range and held at a constant strain. Over time, the internal force within the material progressively decreases. What biomechanical phenomenon does this describe?

. Creep
. Stress relaxation
. Fatigue
. Hysteresis
. Isotropy

Correct Answer & Explanation

. Stress relaxation

Explanation

Stress relaxation is a viscoelastic property where the stress (internal force) decreases over time when a material is held at a constant strain (deformation). Creep, conversely, is an increase in strain under constant stress.

Question 1003

Topic: Infection, Pharmacology & VTE
A 35-year-old woman develops acute shortness of breath and hypotension 3 days after internal fixation of a pelvic ring injury. A massive pulmonary embolism is suspected. Which of the following electrocardiogram (ECG) findings, though not the most common, is classically associated with right ventricular strain in this condition?
. Peaked T waves
. ST-segment elevation in leads V1-V6
. S1Q3T3 pattern
. Prolonged PR interval
. Prominent U waves

Correct Answer & Explanation

. S1Q3T3 pattern

Explanation

The S1Q3T3 pattern (prominent S wave in lead I, Q wave and inverted T wave in lead III) is a classic sign of acute right ventricular strain or cor pulmonale due to a pulmonary embolism, although sinus tachycardia is the most common overall ECG finding.

Question 1004

Topic: 1. General Principles & Basic Science

Normal articular cartilage is divided into distinct structural zones. Which zone contains the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers oriented perpendicular to the joint surface?

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

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone has the highest proteoglycan content, the lowest water content, and thick collagen fibrils arranged perpendicular to the articular surface to resist compressive loads.

Question 1005

Topic: Biology, Genetics & Bone Healing

Denosumab is a monoclonal antibody utilized in the treatment of osteoporosis and giant cell tumor of bone. It exerts its clinical effect by binding directly to which of the following molecular targets?

. Receptor activator of nuclear factor kappa-B (RANK)
. Receptor activator of nuclear factor kappa-B ligand (RANKL)
. Osteoprotegerin (OPG)
. Macrophage colony-stimulating factor (M-CSF)
. Sclerostin

Correct Answer & Explanation

. Receptor activator of nuclear factor kappa-B ligand (RANKL)

Explanation

Denosumab binds directly to RANKL, preventing it from interacting with RANK on the surface of osteoclasts and their precursors. This mechanism effectively mimics the natural inhibitory action of Osteoprotegerin (OPG).

Question 1006

Topic: Biology, Genetics & Bone Healing

During primary bone healing following rigid plate fixation (absolute stability), healing occurs primarily without cartilaginous callus formation via Haversian remodeling. Which of the following best describes the cellular arrangement of the 'cutting cone' mechanism?

. Osteoblasts at the leading edge and osteoclasts at the trailing edge
. Osteoclasts at the leading edge and osteoblasts at the trailing edge
. Chondrocytes at the leading edge and osteoblasts at the trailing edge
. Macrophages at the leading edge and fibroblasts at the trailing edge
. Osteocytes at the leading edge and osteoclasts at the trailing edge

Correct Answer & Explanation

. Osteoclasts at the leading edge and osteoblasts at the trailing edge

Explanation

In the cutting cone of primary cortical bone healing, osteoclasts are situated at the front (leading edge) to resorb dead bone, followed closely by osteoblasts at the rear (trailing edge) which lay down new osteoid to form Haversian systems.

Question 1007

Topic: Infection, Pharmacology & VTE

A 65-year-old man requires an emergency open reduction and internal fixation for a highly displaced, open tibia fracture with vascular compromise. He chronically takes warfarin for atrial fibrillation and his current INR is 4.5. Which of the following provides the most rapid and effective reversal of his anticoagulation?

. Intravenous Vitamin K alone
. Fresh frozen plasma (FFP)
. Prothrombin complex concentrate (PCC) and Vitamin K
. Cryoprecipitate
. Desmopressin (DDAVP)

Correct Answer & Explanation

. Prothrombin complex concentrate (PCC) and Vitamin K

Explanation

Prothrombin complex concentrate (PCC) provides the most rapid, low-volume reversal of Vitamin K antagonists (warfarin) by supplying concentrated factors II, VII, IX, and X. IV Vitamin K is given concurrently to sustain the reversal once the PCC half-life wanes.

Question 1008

Topic: 1. General Principles & Basic Science

Tranexamic acid (TXA) is commonly utilized to reduce perioperative blood loss in major orthopedic procedures. What is its primary mechanism of action?

. Activates the extrinsic coagulation cascade
. Competitively inhibits plasminogen activation
. Directly inhibits factor Xa
. Promotes platelet aggregation and degranulation
. Cross-links fibrin polymers

Correct Answer & Explanation

. Competitively inhibits plasminogen activation

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It reversibly binds to plasminogen, competitively inhibiting its activation into plasmin, thereby preventing the degradation of fibrin clots (antifibrinolytic effect).

Question 1009

Topic: Biomechanics & Biomaterials

A biomechanical evaluation of a new synthetic ligament reveals that the material becomes stiffer as the rate of applied tension increases. This time- and rate-dependent material behavior is best described as:

. Anisotropy
. Viscoelasticity
. Plasticity
. Creep
. Fatigue

Correct Answer & Explanation

. Viscoelasticity

Explanation

Viscoelastic materials exhibit time- and rate-dependent behavior, meaning their mechanical response (like stiffness) changes depending on how fast the load is applied. Normal ligaments and tendons are naturally viscoelastic.

Question 1010

Topic: Physiology & Rehabilitation

During the normal human gait cycle, which muscle or muscle group undergoes an essential eccentric contraction during the initial contact (heel strike) to loading response phase to prevent a 'foot slap' mechanism?

. Gastrocnemius-soleus complex
. Quadriceps femoris
. Hamstrings
. Tibialis anterior
. Gluteus maximus

Correct Answer & Explanation

. Tibialis anterior

Explanation

The tibialis anterior contracts eccentrically (lengthens under tension) immediately following heel strike to decelerate plantarflexion and gently lower the forefoot to the ground, preventing 'foot slap'.

Question 1011

Topic: Biomechanics & Biomaterials

Galvanic corrosion is an electrochemical process that occurs when two dissimilar metals are placed in physical contact within a conductive fluid environment. Which of the following metal combinations is highly susceptible to this specific type of corrosion and generally avoided in orthopedics?

. Titanium alloy and commercially pure titanium
. Cobalt-chromium and ceramic
. Titanium alloy and stainless steel
. Stainless steel and highly cross-linked polyethylene
. Zirconium and ceramic

Correct Answer & Explanation

. Titanium alloy and commercially pure titanium

Explanation

Mixing titanium alloys with stainless steel implants (e.g., a stainless steel screw in a titanium plate) in a physiological environment creates a strong electrochemical gradient, leading to rapid galvanic corrosion and potential hardware failure.

Question 1012

Topic: 1. General Principles & Basic Science
The organic extracellular matrix of normal hyaline articular cartilage is specifically designed to resist both tensile and compressive loads. Which type of collagen constitutes the vast majority (90-95%) of this collagenous matrix?
. Type I
. Type II
. Type III
. Type IV
. Type X

Correct Answer & Explanation

. Type II

Explanation

Type II collagen makes up 90-95% of the collagen in hyaline articular cartilage. Type I collagen is primarily found in bone, tendon, meniscus, and the annulus fibrosus. Type X is associated with the calcified cartilage zone and hypertrophic chondrocytes.

Question 1013

Topic: Biology, Genetics & Bone Healing
Which of the following structures enables the growth plate to grow in diameter as the skeleton gets larger?
. The chondroepiphysis
. The apophysis
. The groove of Ranvier
. The ring of Lacroix
. The secondary spongiosa

Correct Answer & Explanation

. The groove of Ranvier

Explanation

The ossification groove of Ranvier contains chondrocytes that provide latitudinal growth of the growth plate. The groove of Ranvier may be thought of as the growth ring of the growth plate. The chondroepiphysis is the cartilage precursor of the epiphysis. The apophysis is a nonarticular growth region. The ring of Lacroix is a peripheral structure that reinforces the growth plate. The secondary spongiosa is mature lamellar bone after it has been remodeled.

Question 1014

Topic: 1. General Principles & Basic Science

Which area of the growth plate has the lowest oxygen tension:

. The reserve zone
. The proliferative zone
. The hypertrophic zone
. The zone of calcification
. The perichondral ring

Correct Answer & Explanation

. The hypertrophic zone

Explanation

The lowest pressure of oxygen is in the hypertrophic zone because it is poorly vascularized. This is one of the features that triggers cell death and calcificaton.

Question 1015

Topic: 1. General Principles & Basic Science

How many major centers of ossification comprise the normal lumbar vertebral body:

. One
. Two
. Three
. Four
. Five

Correct Answer & Explanation

. Two

Explanation

The normal lumbar and thoracic vertebrae are comprised of two posterior and one main anterior ossification center. These join at the neurocentral synchondrosis and the midline vertebal ossification center.

Question 1016

Topic: Biology, Genetics & Bone Healing
An African-American mother brings her 18-month-old baby in for examination because he has bowing of the legs. The child's past medical history is normal including height and weight. The child is still breast-fed. Radiographs reveal mild widening and irregularity of the physes. Which of the following conditions is likely to be found on laboratory examination?
. Elevated phosphorus
. Decreased alkaline phosphatase
. Normal 1,25 dihydroxyvitamin D
. Elevated creatinine
. Elevated parathyroid hormone

Correct Answer & Explanation

. Elevated parathyroid hormone

Explanation

This patient has nutritional rickets because of a combination of decreased vitamin D intake and increased need for sunlight due to dark skin. The laboratory findings should include a low-normal calcium phosphate, elevated alkaline phosphatase and parathyroid hormone, and low vitamin D levels and precursors. Vitamin D supplementation without bracing is adequate treatment.

Question 1017

Topic: 1. General Principles & Basic Science

The potency ratio of hydromorphone to morphine sulfate is:

. 1-2:1
. 5:1
. 7-10:1
. 20-25:1
. 50:1

Correct Answer & Explanation

. 7-10:1

Explanation

The potency ratio of commonly-used drugs is one of the factors that determines the appropriate dose of a drug. The potency ratio of hydromorphone to morphine sulfate is 7-10:1.

Question 1018

Topic: 1. General Principles & Basic Science
The youngest age at which a number scale to quantitate pain (i.e., rating it as 1-10) can be appropriately used is:
. 2 years
. 3 years
. 5 years
. 7 years
. 9 years

Correct Answer & Explanation

. 7 years

Explanation

Pain measurement is becoming increasingly important for both children and adults. A number scale to quantitate pain can be appropriately used for most children over the age of 7 years. For younger children, the 'faces scale' or a finger span scale (stretching the fingers as far apart as possible) is more accurate.

Question 1019

Topic: 1. General Principles & Basic Science

Which of the following findings on a neuromuscular examination is not characteristic of spasticity:

. Hyperreflexia
. C lonus
. Velocity-dependent resistance
. Writhing movements
. Muscle contracture

Correct Answer & Explanation

. Writhing movements

Explanation

Spasticity is a hallmark of upper motor lesions. Spasticity is characterized by hyperreflexia, clonus, and velocity-dependent resistance. After early childhood, muscle contracture also develops. Writhing movements are characteristic of athetosis, not spasticity.

Question 1020

Topic: 1. General Principles & Basic Science

Which of the following describes the mechanism of action of Botulinum toxin type A:

. Botulinum toxin type A blocks the release of acetylcholine.
. Botulinum toxin type A prevents binding of acetylcholine to receptors.
. Botulinum toxin type A interrupts transmission of impulses along axons.
. Botulinum toxin type A softens fibrous tissue causing contracture.
. Botulinum toxin type A depolarizes sarcolemma of muscles.

Correct Answer & Explanation

. Botulinum toxin type A blocks the release of acetylcholine.

Explanation

Botulinum toxin type A acts by blocking the release of acetylcholine at the nerve terminal. Over time, new terminals sprout and the effect is lost. By contrast, alcohol and phenol denature proteins and disrupt nerve conduction.

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