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1. General Principles & Basic Science MCQs

Practice Set 208 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 4141

Topic: 1. General Principles & Basic Science
A 48-year-old male presents with a rapidly expanding erythematous lesion on his lower leg, severe pain out of proportion to the clinical exam, and hemorrhagic bullae. The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is calculated to distinguish this from severe cellulitis. Which of the following laboratory parameters is a component of the LRINEC score?
. Serum sodium
. Serum lactate
. Serum potassium
. Serum calcium
. Serum albumin

Correct Answer & Explanation

. Serum lactate

Explanation

The LRINEC score uses six routine laboratory parameters to stratify the risk of necrotizing fasciitis: C-reactive protein (CRP), total white blood cell count (WBC), hemoglobin, serum sodium (Na < 135 mEq/L scores 2 points), serum creatinine, and serum glucose. Serum lactate, though indicative of sepsis/tissue hypoperfusion, is not a variable in the original LRINEC score.

Question 4142

Topic: Infection, Pharmacology & VTE

A 4-year-old boy presents with right hip pain and refusal to bear weight. Which of the following combinations of parameters comprises the original Kocher criteria, utilized to differentiate pediatric septic arthritis of the hip from transient synovitis?

. Temperature > 38.5 C, ESR > 40 mm/hr, WBC > 12,000 cells/mm3, and refusal to bear weight
. Temperature > 38.0 C, CRP > 20 mg/L, WBC > 10,000 cells/mm3, and refusal to bear weight
. Temperature > 38.5 C, ESR > 20 mm/hr, CRP > 10 mg/L, and inability to ambulate
. Fever > 39.0 C, synovial WBC > 50,000 cells/mm3, positive blood cultures, and hip flexion contracture
. Joint space widening > 2mm on radiograph, ESR > 40 mm/hr, WBC > 12,000 cells/mm3, and subjective fever

Correct Answer & Explanation

. Temperature > 38.5 C, ESR > 40 mm/hr, WBC > 12,000 cells/mm3, and refusal to bear weight

Explanation

The original Kocher criteria for differentiating septic arthritis from transient synovitis in children include four parameters: Non-weight-bearing status on the affected side, Erythrocyte sedimentation rate (ESR) > 40 mm/hr, Fever > 38.5 C (101.3 F), and a Serum white blood cell (WBC) count > 12,000 cells/mm3. (Note: CRP > 2.0 mg/dL was later added as a fifth independent predictor in Caird's modification).

Question 4143

Topic: 1. General Principles & Basic Science

In the surgical management of chronic post-traumatic osteomyelitis, antibiotic-impregnated polymethylmethacrylate (PMMA) beads are placed into the dead space following radical debridement. To maximize the rate and duration of local antibiotic elution from the PMMA spacer, which of the following techniques is most appropriate?

. Vacuum mixing the cement to increase compressive strength and homogenize the mixture
. Adding >20% weight/weight of liquid aqueous antibiotics to the monomer
. Increasing the porosity of the cement by hand-mixing rather than using a vacuum system
. Decreasing the volume-to-surface area ratio by casting large, solid, monolithic blocks rather than beads
. Selecting a high-viscosity cement to slow the immediate burst release of antibiotics

Correct Answer & Explanation

. Increasing the porosity of the cement by hand-mixing rather than using a vacuum system

Explanation

Antibiotic elution from PMMA is a surface phenomenon. Maximizing elution requires increasing the surface area and the porosity of the cement. Hand-mixing cement (rather than vacuum mixing) incorporates air, increasing porosity and thus elution. Using beads (high surface-area-to-volume ratio) also increases elution compared to a solid block. Adding liquid antibiotics compromises the cement severely and is not recommended in large volumes.

Question 4144

Topic: Infection, Pharmacology & VTE

In the pathogenesis of periprosthetic joint infection, biofilm maturation allows bacteria to become highly resistant to host defenses and antimicrobials. Which biological process allows bacteria to coordinate gene expression according to the local density of their population?

. Phagocytosis evasion
. Quorum sensing
. Planktonic shedding
. Glycocalyx synthesis
. Chemotaxis

Correct Answer & Explanation

. Quorum sensing

Explanation

Quorum sensing is an intercellular communication mechanism that allows bacteria to share information about cell density and adjust gene expression accordingly. This process is critical for biofilm maturation and the development of antibiotic resistance.

Question 4145

Topic: Surgical Anatomy & Approaches

During the ilioinguinal approach for an anterior column acetabular fracture, the surgeon encounters significant bleeding from the "corona mortis". This vascular structure represents an anastomosis between which two vessels?

. External iliac artery and internal pudendal artery
. External iliac (or inferior epigastric) vessels and obturator vessels
. Internal iliac artery and superior gluteal artery
. Femoral artery and internal pudendal artery
. Superior vesicular artery and obturator artery

Correct Answer & Explanation

. External iliac (or inferior epigastric) vessels and obturator vessels

Explanation

The corona mortis is an anatomic variant representing an anastomosis between the external iliac (or inferior epigastric) system and the obturator system. It is located over the superior pubic ramus and is at high risk during anterior pelvic/acetabular exposures.

Question 4146

Topic: Infection, Pharmacology & VTE

A 4-year-old boy presents with a limp, right hip pain, and a temperature of 38.8°C. His WBC count is 14,000/mm3, ESR is 50 mm/hr, and CRP is 3.5 mg/dL. He refuses to bear weight. Based on the Kocher and Caird criteria, what is the approximate probability that this child has septic arthritis rather than transient synovitis?

. 10%
. 30%
. 50%
. 75%
. 99%

Correct Answer & Explanation

. 99%

Explanation

This patient has 5 out of 5 criteria (fever > 38.5°C, non-weight bearing, ESR > 40, WBC > 12k, and CRP > 2.0 mg/dL). The presence of 4 or more criteria yields a 93-99% predictive probability for pediatric septic arthritis of the hip.

Question 4147

Topic: 1. General Principles & Basic Science

Which of the following best describes a Bonferroni correction? Review Topic

. An analysis that starts with a particular probability of an event (the prior probability) and incorporates new information to generate a revised probability (a posterior probability)
. Human behavior that is changed when participants are aware that their behavior is being observed.
. Used to assess the relationship between two normally distributed continuous variables
. A post-hoc statistical correction made to P values when several dependent or independent statistical tests are being performed simultaneously on a single data set
. The ability of a study to detect the difference between two interventions if one in fact exists

Correct Answer & Explanation

. A post-hoc statistical correction made to P values when several dependent or independent statistical tests are being performed simultaneously on a single data set

Explanation

A Bonferroni correction is a post-hoc statistical correction made to P values when several dependent or independent statistical tests are being performed simultaneously on a single data set.To perform a Bonferroni correction, divide the critical P value (alpha level) by the number of comparisons being made. For example, if 10 hypotheses are being tested, the new critical P value would be (alpha level)/10. The statistical power of the study is then calculated based on this modified P value.Guyatt et al. discusses hypothesis testing and the role of alpha levels and P values. They report that the Bonferroni correction is derived from testing a dependent or independent hypotheses on a set of data and finding that the probability of a type I error is offset by testing each hypothesis at a statistical significance level divided by the number of times what it would be if only one hypothesis were tested.Incorrect1:ThisdescribesBayesiananalysis.2:ThisdescribesHawthorneeffect.3:ThisdescribesPearsoncorrelation.

Question 4148

Topic: 1. General Principles & Basic Science
Which of the following radiographic views best assesses anterior coverage of the dysplastic hip?
. AP of the hip
. Obturator oblique
. Lauenstein lateral
. Faux profil
. Pelvic inlet

Correct Answer & Explanation

. Faux profil

Explanation

DISCUSSION: Anterior coverage of the hip may be best estimated by the anterior center edge angle of Lequesne and de Seze (analogous to Wiberg’s angle), which is measured on the well-defined faux profil view. Evaluation with CT scans also has been described.

Question 4149

Topic: 1. General Principles & Basic Science

Which of the following factors is considered to be the strongest predictor of outcome following arthroscopic partial meniscectomy? Review Topic

. Patient age
. Patient body mass index
. Amount of meniscal resection
. Location of the meniscal tear
. Modified Outerbridge cartilage score

Correct Answer & Explanation

. Modified Outerbridge cartilage score

Explanation

In a recent evidence-based review of the literature, the only consistent factor predicting outcome after arthroscopic partial meniscectomy was the extent of osteoarthritis as classified by the modified Outerbridge cartilage score at the time of surgery. All other factors listed (ie, location of meniscal tear, patient age, patient BMI, and amount of meniscal resection) were shown to not predict outcome following partial meniscectomy. While not provided as an answer choice, female gender was shown to be a predictor for slower recovery in the short term.

Question 4150

Topic: Surgical Anatomy & Approaches

During a Latarjet procedure, the coracoid process is osteotomized and transferred to the anterior glenoid. Which nerve is at greatest risk of injury during the approach and retraction medial to the conjoint tendon?

. Axillary nerve
. Suprascapular nerve
. Musculocutaneous nerve
. Median nerve
. Radial nerve

Correct Answer & Explanation

. Musculocutaneous nerve

Explanation

The musculocutaneous nerve enters the coracobrachialis approximately 5 to 8 cm distal to the coracoid process. Vigorous medial retraction of the conjoint tendon places this nerve at high risk for a traction injury.

Question 4151

Topic: Surgical Anatomy & Approaches

Which vessel provides the primary blood supply to the humeral head, and what is its anatomic course?

. Posterior humeral circumflex artery; runs in the quadrangular space
. Anterior humeral circumflex artery; runs as the arcuate artery within the bicipital groove
. Suprascapular artery; enters via the spinoglenoid notch
. Thoracoacromial artery; penetrates the coracoclavicular fascia
. Profunda brachii artery; runs in the spiral groove

Correct Answer & Explanation

. Posterior humeral circumflex artery; runs in the quadrangular space

Explanation

Recent anatomic and perfusion studies have demonstrated that the posterior humeral circumflex artery, running through the quadrangular space, provides the majority of the blood supply to the humeral head. Historically, the anterior circumflex artery was thought to be the primary supply.

Question 4152

Topic: Infection, Pharmacology & VTE

During a medial opening wedge high tibial osteotomy (HTO) for medial compartment osteoarthritis, which of the following technical errors will most likely result in an unintended increase in the posterior tibial slope?

. Placing the osteotomy hinge posterior to the fibular head
. Opening the wedge more anteriorly than posteriorly
. Opening the wedge more posteriorly than anteriorly
. Releasing the superficial medial collateral ligament
. Failing to release the pes anserinus tendons

Correct Answer & Explanation

. Opening the wedge more posteriorly than anteriorly

Explanation

Because the proximal tibia is triangular, opening the wedge uniformly or more anteriorly will inadvertently increase the posterior tibial slope. To maintain normal slope, the wedge must be opened approximately twice as much posteromedially as anteromedially.

Question 4153

Topic: Surgical Anatomy & Approaches

During an open subpectoral biceps tenodesis, deep medial retraction places which of the following neurovascular structures at greatest risk of iatrogenic injury?

. Axillary nerve
. Radial nerve
. Musculocutaneous nerve
. Median nerve
. Cephalic vein

Correct Answer & Explanation

. Musculocutaneous nerve

Explanation

The musculocutaneous nerve courses medially beneath the biceps muscle belly. Excessive medial retraction during a subpectoral biceps tenodesis places this nerve at significant risk for traction injury.

Question 4154

Topic: Physiology & Rehabilitation

Which mechanism of injury is most classically responsible for an acute rupture of the pectoralis major tendon?

. Concentric contraction during internal rotation
. Eccentric contraction while the shoulder is extended and externally rotated
. Direct blunt trauma to the anterior chest wall
. Eccentric contraction during shoulder flexion
. Forced horizontal adduction against a fixed object

Correct Answer & Explanation

. Eccentric contraction while the shoulder is extended and externally rotated

Explanation

Pectoralis major ruptures almost exclusively occur during heavy weightlifting, particularly the bench press. The injury happens when the muscle undergoes maximal eccentric contraction with the shoulder extended and externally rotated.

Question 4155

Topic: 1. General Principles & Basic Science

The primary blood supply to the menisci of the knee, which supports healing in the peripheral 'red-red' zone, is derived from the:

. Middle genicular artery
. Medial and lateral superior genicular arteries
. Medial and lateral inferior genicular arteries
. Descending genicular artery
. Anterior tibial recurrent artery

Correct Answer & Explanation

. Medial and lateral inferior genicular arteries

Explanation

The peripheral 10% to 30% of the menisci is vascularized by a perimeniscal capillary plexus originating primarily from branches of the medial and lateral inferior genicular arteries. Tears in this zone have a higher healing potential.

Question 4156

Topic: 1. General Principles & Basic Science

During a high tibial osteotomy (HTO) for medial compartment knee osteoarthritis, creating excessive valgus overcorrection significantly increases the risk of which complication?

. Progressive lateral compartment osteoarthritis
. Increased tension on the superficial MCL
. Increased risk of patellar tendinopathy
. Rapid breakdown of the medial compartment
. Development of patella alta

Correct Answer & Explanation

. Progressive lateral compartment osteoarthritis

Explanation

The goal of HTO is to shift the mechanical weight-bearing axis slightly lateral to the midline (Fujisawa point). Valgus overcorrection shifts too much load laterally, predisposing the patient to accelerated lateral compartment osteoarthritis.

Question 4157

Topic: 1. General Principles & Basic Science

Which of the following describes the biomechanical effect of an untreated posterior medial meniscus root tear?

. Decreased peak contact pressure in the medial compartment
. Biomechanical equivalence to a completely intact meniscus
. Biomechanical equivalence to a total medial meniscectomy
. Increased anterior tibial translation during the Lachman test
. Shift of peak contact pressures to the lateral compartment

Correct Answer & Explanation

. Biomechanical equivalence to a total medial meniscectomy

Explanation

A posterior medial meniscus root tear disrupts hoop stresses, causing functional extrusion of the meniscus. Biomechanically, this results in peak contact pressures equivalent to a total medial meniscectomy, predisposing the joint to rapid osteoarthritis.

Question 4158

Topic: 1. General Principles & Basic Science

Historical orthopedic literature long taught that a specific artery provided the vast majority of the blood supply to the humeral head. However, more recent quantitative anatomical studies have redefined this. Which artery is now recognized as providing the predominant blood supply to the humeral head?

. Anterior circumflex humeral artery
. Arcuate artery
. Posterior circumflex humeral artery
. Thoracoacromial artery
. Profunda brachii artery

Correct Answer & Explanation

. Posterior circumflex humeral artery

Explanation

Historically, the arcuate artery (a continuation of the ascending branch of the anterior circumflex humeral artery) was thought to supply the majority of the humeral head. However, Hettrich et al. (JBJS Am 2010) demonstrated via quantitative assessment that the posterior circumflex humeral artery actually provides the predominant blood supply (approximately 64%) to the humeral head.

Question 4159

Topic: Surgical Anatomy & Approaches

During an anterior (ilioinguinal or modified Stoppa) approach to the acetabulum, severe, life-threatening hemorrhage can occur from the 'corona mortis'. This structure represents an anastomosis between which two vascular systems?

. Internal iliac vein and external iliac vein
. External iliac (or inferior epigastric) vessels and obturator vessels
. Superior gluteal vessels and inferior gluteal vessels
. Internal pudendal artery and external pudendal artery
. Inferior mesenteric artery and internal iliac artery

Correct Answer & Explanation

. External iliac (or inferior epigastric) vessels and obturator vessels

Explanation

The corona mortis (crown of death) is an anatomical variant representing an arterial or venous anastomosis between the external iliac (or its branch, the inferior epigastric) system and the obturator system. It is located on the posterior aspect of the superior pubic ramus, typically 5 to 6 cm lateral to the pubic symphysis, and is highly vulnerable during anterior pelvic ring and acetabular exposures.

Question 4160

Topic: 1. General Principles & Basic Science

When evaluating a severely traumatized lower limb using the Mangled Extremity Severity Score (MESS), which of the following variables uniquely doubles its allocated point value if a specific time threshold is exceeded?

. Patient Age
. Shock duration
. Ischemia
. Soft tissue injury grading
. Skeletal injury grading

Correct Answer & Explanation

. Ischemia

Explanation

The MESS score evaluates four criteria: Skeletal/soft-tissue injury, Limb ischemia, Shock, and Age. The points allocated for Limb Ischemia are specifically doubled if the ischemia time exceeds 6 hours, recognizing the exponential increase in the risk of irreversible muscle necrosis and ultimate amputation following prolonged anoxia.

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