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1. General Principles & Basic Science MCQs

Practice Set 99 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 1961

Topic: 1. General Principles & Basic Science

Which of the following physical examination maneuvers is most specific for diagnosing patellar instability?

. Valgus stress test at 30 degrees of flexion.
. Lachman test.
. Patellar apprehension test.
. McMurray test.
. Patellar grind test.

Correct Answer & Explanation

. Patellar apprehension test.

Explanation

Correct Answer: CThe patellar apprehension test (or 'Fairbank's test') involves attempting to laterally translate the patella with the knee in varying degrees of flexion while observing for the patient's anxiety, muscle guarding, or resistance, which signifies impending dislocation. This test is highly specific for patellar instability. The other tests are for collateral ligaments (valgus stress), ACL (Lachman), meniscal injury (McMurray), or patellofemoral pain syndrome (patellar grind), not patellar instability directly.

Question 1962

Topic: 1. General Principles & Basic Science

Following an acute lateral patellar dislocation, magnetic resonance imaging (MRI) is most likely to reveal a specific pattern of bone bruising. Which two anatomic locations classically demonstrate bone contusions in this scenario?

. Medial femoral condyle and lateral patellar facet
. Lateral femoral condyle and inferomedial patellar facet
. Lateral femoral condyle and superolateral patellar facet
. Medial femoral condyle and medial patellar facet
. Anterior tibia and inferior patellar pole

Correct Answer & Explanation

. Lateral femoral condyle and inferomedial patellar facet

Explanation

The classic MRI bone bruising pattern after an acute lateral patellar dislocation involves the anterolateral aspect of the lateral femoral condyle and the inferomedial aspect of the patella. This occurs as the patella impacts the condyle during dislocation or relocation.

Question 1963

Topic: 1. General Principles & Basic Science

A positive J-sign observed during physical examination of a patient with patellofemoral instability represents which of the following kinematic events?

. Sudden medial subluxation of the patella during terminal extension
. Sudden lateral deviation of the patella during terminal extension as it exits the trochlear groove
. Sudden lateral deviation of the patella during deep flexion
. Posterior sagging of the tibia during active knee flexion
. Anterior tracking of the patella against a supratrochlear spur

Correct Answer & Explanation

. Sudden lateral deviation of the patella during terminal extension as it exits the trochlear groove

Explanation

The J-sign describes the sudden lateral deviation (or tracking) of the patella in terminal extension. This occurs because the patella loses the bony restraint of the trochlear groove as it translates proximally and is pulled laterally by an imbalance in soft tissues.

Question 1964

Topic: Surgical Anatomy & Approaches

A surgeon is planning definitive ORIF for a G-A Type B, Subtype 2 pilon fracture with significant anterolateral articular involvement. The chosen approach is the anterolateral approach. Which of the following describes the correct internervous plane and key neurovascular structures to protect during this approach?

. Between the flexor hallucis longus and the peroneus longus/brevis, protecting the posterior tibial artery and nerve.
. Between the tibialis anterior and the extensor digitorum longus, protecting the anterior tibial artery and deep peroneal nerve.
. Between the flexor digitorum longus and the tibialis posterior, protecting the saphenous nerve and vein.
. Directly over the medial malleolus, protecting the superficial peroneal nerve.
. Between the gastrocnemius and soleus, protecting the sural nerve.

Correct Answer & Explanation

. Between the tibialis anterior and the extensor digitorum longus, protecting the anterior tibial artery and deep peroneal nerve.

Explanation

Correct Answer: BThe case details the surgical anatomy and approaches. For the anterolateral approach:Internervous Plane:It utilizes the interval between the tibialis anterior muscle (innervated by the deep peroneal nerve) and the extensor digitorum longus muscle (also deep peroneal nerve). While technically not a true internervous plane as both muscles are supplied by the deep peroneal nerve, it is a functional interval.Neurovascular Structures:Access is achieved by retracting the extensor tendons and the neurovascular bundle (anterior tibial artery and deep peroneal nerve) medially. Therefore, protecting the anterior tibial artery and deep peroneal nerve is crucial.Let's evaluate the other options:A. Between the flexor hallucis longus and the peroneus longus/brevis, protecting the posterior tibial artery and nerve:This describes the posterolateral approach, which accesses the posterior malleolus and posterolateral plafond, and protects the posterior neurovascular bundle.C. Between the flexor digitorum longus and the tibialis posterior, protecting the saphenous nerve and vein:This describes the posteromedial approach, which accesses the posteromedial aspect of the tibia. The saphenous nerve and vein are typically protected in the anteromedial approach.D. Directly over the medial malleolus, protecting the superficial peroneal nerve:This describes the anteromedial approach. The superficial peroneal nerve is anterolateral and would be at risk with an anterolateral incision, but this option incorrectly places it with the anteromedial approach.E. Between the gastrocnemius and soleus, protecting the sural nerve:This describes a posterior approach to the tibia, typically for proximal or mid-shaft fractures, not specifically for the distal pilon, and the sural nerve is typically protected in posterolateral approaches.

Question 1965

Topic: Surgical Anatomy & Approaches

A 42-year-old male undergoes open reduction and internal fixation of a mid-shaft humeral fracture using a posterior approach (triceps-sparing). During the procedure, the surgeon is particularly cautious when dissecting in the spiral groove. Which of the following structures is most at risk of iatrogenic injury in this specific anatomical region during this approach?

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

Correct Answer & Explanation

. Radial nerve

Explanation

Correct Answer: DThe radial nerve (Option D) is the structure most at risk during a posterior approach to the mid-shaft humerus, particularly when dissecting in the spiral groove. The radial nerve courses obliquely across the posterior aspect of the humerus within the spiral groove, approximately 10-14 cm proximal to the lateral epicondyle. It is intimately associated with the bone in this region, making it highly vulnerable to direct injury, traction, or compression during surgical exposure, reduction, and plate application. The triceps-sparing posterior approach aims to minimize muscle damage but still requires careful identification and protection of the radial nerve.The Axillary nerve (Option A) is more proximal, associated with the surgical neck of the humerus. The Median nerve (Option B) and Ulnar nerve (Option C) are located more medially and anteriorly in the arm, and distally, respectively, and are not typically at direct risk with a posterior mid-shaft approach. The Musculocutaneous nerve (Option E) is located more anteriorly, between the biceps and brachialis muscles, and is at risk with anterolateral approaches, not a posterior approach to the mid-shaft.

Question 1966

Topic: Surgical Anatomy & Approaches

A 45-year-old male presents with a pilon fracture featuring a large, displaced anterolateral (Chaput) fragment and central articular impaction. Which surgical approach provides the most direct visualization and access for reducing this specific fracture pattern?

. Posterolateral
. Anteromedial
. Anterolateral
. Direct medial
. Posteromedial

Correct Answer & Explanation

. Anterolateral

Explanation

The anterolateral approach allows direct visualization of the Tillaux-Chaput fragment and central articular impaction. It utilizes the internervous plane between the superficial peroneal nerve and deep peroneal nerve.

Question 1967

Topic: Surgical Anatomy & Approaches

During a deltopectoral approach for open reduction internal fixation of a proximal humerus fracture, excessive distal retraction of the deltoid risks injury to the axillary nerve. On average, how far distal to the lateral edge of the acromion does the axillary nerve travel?

. 1 to 2 cm
. 5 to 7 cm
. 10 to 12 cm
. 15 to 17 cm
. 20 to 22 cm

Correct Answer & Explanation

. 5 to 7 cm

Explanation

The axillary nerve runs transversely across the deep surface of the deltoid muscle, typically averaging 5 to 7 cm distal to the lateral edge of the acromion. Care must be taken not to split the deltoid distally beyond this point during anterolateral or deltopectoral extensions.

Question 1968

Topic: Surgical Anatomy & Approaches

During the anterolateral approach to the humeral shaft, the brachialis muscle is split. To minimize the risk of denervating portions of the brachialis, how should the muscle be split?

. Longitudinally through its medial third
. Longitudinally along its midline, utilizing its dual innervation
. Transversely at the level of the deltoid insertion
. It should be retracted laterally in its entirety without splitting
. It should be retracted medially in its entirety without splitting

Correct Answer & Explanation

. Longitudinally along its midline, utilizing its dual innervation

Explanation

The brachialis muscle receives dual innervation: the medial aspect is innervated by the musculocutaneous nerve, and the lateral aspect by the radial nerve. Splitting the muscle longitudinally along its midline safely utilizes this dual innervation, preserving function on both halves.

Question 1969

Topic: Biology, Genetics & Bone Healing

A 45-year-old male sustains a severe high-energy pilon fracture. He undergoes placement of an ankle-spanning external fixator on the day of injury. When assessing the patient for definitive open reduction and internal fixation (ORIF), which of the following is the most reliable clinical indicator that the soft tissues are ready?

. Post-injury day 14
. Normalization of serum CRP
. Resolution of fracture blisters and presence of a positive wrinkle sign
. Radiographic evidence of early callus formation
. Patient ability to actively dorsiflex the toes without pain

Correct Answer & Explanation

. Resolution of fracture blisters and presence of a positive wrinkle sign

Explanation

A positive wrinkle sign indicates resolution of significant interstitial edema and is the most reliable clinical sign that the soft tissue envelope can tolerate surgical incisions for definitive ORIF. Delaying surgery until this sign appears minimizes the risk of severe wound complications.

Question 1970

Topic: Surgical Anatomy & Approaches

A 28-year-old male sustains a closed midshaft humerus fracture and presents with an inability to extend his wrist and fingers. Sensation is decreased over the dorsal first web space. The fracture is acceptably aligned in a coaptation splint. What is the most appropriate initial management for his neurologic deficit?

. Immediate surgical exploration of the radial nerve
. Electromyography (EMG) at 1 week post-injury
. Observation and expectant management
. Surgical exploration if no recovery is noted after 2 weeks
. Ultrasound-guided nerve injection

Correct Answer & Explanation

. Observation and expectant management

Explanation

Primary radial nerve palsy in the setting of a closed humeral shaft fracture has a high rate of spontaneous recovery (up to 90%). Expectant management with observation is the standard of care, with clinical and EMG re-evaluation at 3-4 months if no recovery occurs.

Question 1971

Topic: Surgical Anatomy & Approaches

A 45-year-old man sustains a severe pilon fracture following a fall from height. Preoperative CT imaging demonstrates a dominant anterolateral articular fragment. Which surgical approach provides the most direct access and optimal trajectory for fixation of this specific fragment?

. Direct medial approach
. Anteromedial approach
. Anterolateral approach
. Posterolateral approach
. Posteromedial approach

Correct Answer & Explanation

. Anterolateral approach

Explanation

The anterolateral approach utilizes the interval between the fibula and the extensor digitorum longus. It provides the most direct and optimal access to the Chaput (anterolateral) fragment of the distal tibia.

Question 1972

Topic: 1. General Principles & Basic Science

Regarding the vascular supply of the humeral head, recent quantitative cadaveric injection studies have challenged classic teaching by demonstrating that the principal blood supply to the majority of the humeral head is derived from which vessel?

. Ascending branch of the anterior circumflex humeral artery
. Posterior circumflex humeral artery
. Thoracoacromial artery
. Suprascapular artery
. Subscapular artery

Correct Answer & Explanation

. Posterior circumflex humeral artery

Explanation

While classic teaching (Gerber et al.) emphasized the anterior circumflex humeral artery, more recent robust studies (Hettrich et al.) demonstrate that the posterior circumflex humeral artery provides the predominant blood supply (up to 64%) to the humeral head.

Question 1973

Topic: Surgical Anatomy & Approaches

During a lateral approach to the distal humerus (Kocher approach) for a capitellar fracture, the surgeon must extend the dissection distally. Which nerve is at greatest risk during the distal extension of the interval between the extensor carpi ulnaris (ECU) and the anconeus?

. Median nerve
. Posterior interosseous nerve (PIN)
. Ulnar nerve
. Anterior interosseous nerve (AIN)
. Superficial radial nerve

Correct Answer & Explanation

. Posterior interosseous nerve (PIN)

Explanation

The posterior interosseous nerve (PIN) wraps around the radial neck within the supinator muscle. It is at significant risk of iatrogenic injury with excessive distal extension of lateral elbow approaches.

Question 1974

Topic: Surgical Anatomy & Approaches
A 32-year-old male sustains a Mason Type III radial head fracture with associated posterolateral rotatory instability (terrible triad injury). Surgical intervention via the Kaplan anterolateral approach is planned. During the deep dissection phase, the surgeon must be acutely aware of the most critical neurovascular structure at risk. Which nerve is most vulnerable during this approach, and what is its anatomical course relative to the supinator muscle?
. Ulnar nerve; it passes posterior to the medial epicondyle and is protected by the medial triceps.
. Median nerve; it passes anterior to the elbow joint, deep to the biceps aponeurosis.
. Posterior Interosseous Nerve (PIN); it passes between the superficial and deep heads of the supinator muscle.
. Radial nerve (superficial branch); it lies superficial to the brachioradialis muscle and is protected by keeping dissection deep.
. Musculocutaneous nerve; it pierces the coracobrachialis and continues as the lateral antebrachial cutaneous nerve.

Correct Answer & Explanation

. Posterior Interosseous Nerve (PIN); it passes between the superficial and deep heads of the supinator muscle.

Explanation

The Kaplan anterolateral approach is primarily used for radial head fractures. The Posterior Interosseous Nerve (PIN) is the paramount structure at risk during this approach. It passes into the forearm between the two heads of the supinator muscle, often compressed by the Arcade of Frohse. Injury to the PIN results in paralysis of wrist and finger extensors, sparing ECRL.

Question 1975

Topic: Surgical Anatomy & Approaches

During a Kaplan anterolateral approach for a radial head fracture, the surgeon identifies the internervous plane. Which two muscles define the superficial internervous plane utilized in this approach, and what is their common innervation?

. A. Brachialis and Biceps Brachii; Musculocutaneous nerve.
. B. Extensor Carpi Radialis Brevis (ECRB) and Extensor Digitorum Communis (EDC); Radial nerve.
. C. Anconeus and Triceps Brachii; Radial nerve.
. D. Flexor Carpi Ulnaris and Flexor Digitorum Profundus; Ulnar nerve.
. E. Pronator Teres and Flexor Carpi Radialis; Median nerve.

Correct Answer & Explanation

. B. Extensor Carpi Radialis Brevis (ECRB) and Extensor Digitorum Communis (EDC); Radial nerve.

Explanation

Correct Answer: BExplanation:The text, under 'Kaplan Anterolateral Approach - Internervous Plane,' explicitly states: 'Superficially: Between the ECRB and EDC, both of which are innervated by the radial nerve. This allows for safe initial dissection.' This directly answers the question.A. Brachialis and Biceps Brachii:These are anterior compartment muscles, primarily innervated by the musculocutaneous nerve, and not part of the Kaplan anterolateral approach internervous plane.C. Anconeus and Triceps Brachii:These are posterior compartment muscles, innervated by the radial nerve, and relevant to the Kocher posterior approach, not the Kaplan anterolateral.D. Flexor Carpi Ulnaris and Flexor Digitorum Profundus:These are medial forearm muscles, primarily innervated by the ulnar nerve, and not part of the Kaplan anterolateral approach.E. Pronator Teres and Flexor Carpi Radialis:These are anterior forearm muscles, primarily innervated by the median nerve, and not part of the Kaplan anterolateral approach.

Question 1976

Topic: Surgical Anatomy & Approaches

A surgeon approaches the radial head via the Kaplan (anterolateral) approach. To safely expose the joint capsule, the deep dissection must exploit a specific internervous plane. Which two muscles define this deep interval?

. Extensor carpi ulnaris and anconeus
. Brachioradialis and pronator teres
. Extensor digitorum communis and extensor carpi radialis brevis
. Extensor carpi radialis longus and brachioradialis
. Flexor carpi ulnaris and flexor digitorum superficialis

Correct Answer & Explanation

. Extensor digitorum communis and extensor carpi radialis brevis

Explanation

The Kaplan approach utilizes the internervous plane between the extensor digitorum communis (posterior interosseous nerve) and the extensor carpi radialis brevis (radial nerve). This is more anterior than the Kocher approach and places the posterior interosseous nerve at a slightly higher risk.

Question 1977

Topic: Surgical Anatomy & Approaches

A 45-year-old female presents with a terrible triad injury of the elbow. A lateral (Kocher) approach is planned to address the radial head fracture. During this approach, the surgical interval is between which two muscles, and what nerve is most at risk if the dissection proceeds too far distally?

. Extensor Carpi Ulnaris (ECU) and Anconeus; Posterior Interosseous Nerve (PIN)
. Extensor Carpi Radialis Brevis (ECRB) and Extensor Digitorum Communis (EDC); Superficial Radial Nerve
. Brachioradialis and Pronator Teres; Median Nerve
. Flexor Carpi Ulnaris (FCU) and Flexor Digitorum Superficialis (FDS); Ulnar Nerve
. Extensor Digitorum Communis (EDC) and Extensor Carpi Radialis Brevis (ECRB); Anterior Interosseous Nerve

Correct Answer & Explanation

. Extensor Carpi Ulnaris (ECU) and Anconeus; Posterior Interosseous Nerve (PIN)

Explanation

The Kocher approach utilizes the internervous plane between the anconeus (radial nerve) and the extensor carpi ulnaris (posterior interosseous nerve). Distal extension of this exposure risks injury to the PIN as it wraps around the radial neck.

Question 1978

Topic: 1. General Principles & Basic Science

A 45-year-old male sustains a bicondylar tibial plateau fracture with a large displaced posteromedial shear fragment. A posteromedial surgical approach is utilized. Which of the following defines the optimal internervous or intermuscular interval for this approach?

. Between the pes anserinus anteriorly and the medial head of the gastrocnemius posteriorly
. Between the medial gastrocnemius and the soleus
. Between the semitendinosus and gracilis muscles
. Between the tibialis posterior and flexor digitorum longus
. Between the anterior tibialis and extensor hallucis longus

Correct Answer & Explanation

. Between the pes anserinus anteriorly and the medial head of the gastrocnemius posteriorly

Explanation

The posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius posteriorly and the pes anserinus anteriorly. This safely exposes the posteromedial tibia for buttress plating while protecting the neurovascular structures.

Question 1979

Topic: Surgical Anatomy & Approaches

A 72-year-old female with severe rheumatoid arthritis undergoes a primary linked semi-constrained total elbow arthroplasty. Postoperatively, she develops progressive weakness in active elbow extension. Which of the following surgical approaches is most strongly associated with this specific complication?

. Triceps-detaching (Bryan-Morrey) approach
. Triceps-splitting approach
. Triceps-sparing approach
. Olecranon osteotomy approach
. Extensile lateral (Kocher) approach

Correct Answer & Explanation

. Triceps-detaching (Bryan-Morrey) approach

Explanation

The triceps-detaching (Bryan-Morrey) approach relies on postoperative reattachment and healing of the triceps mechanism, which carries a known risk of postoperative triceps insufficiency. Triceps-sparing or splitting approaches minimize this specific extensor mechanism risk.

Question 1980

Topic: Biology, Genetics & Bone Healing

A 72-year-old male with a history of chronic obstructive pulmonary disease and a recent fragility fracture of the distal radius is being evaluated for secondary fracture prevention. His DEXA scan shows a T-score of -2.8 at the lumbar spine. He is currently taking calcium and Vitamin D supplements. Which of the following pharmacological interventions would be the most appropriate initial step for this patient, considering his history of a fragility fracture and severe osteoporosis?

. A. Initiate teriparatide (recombinant PTH).
. B. Initiate romosozumab (sclerostin inhibitor).
. C. Initiate alendronate (bisphosphonate).
. D. Increase calcium and Vitamin D supplementation only.
. E. Prescribe calcitonin nasal spray.

Correct Answer & Explanation

. C. Initiate alendronate (bisphosphonate).

Explanation

Correct Answer: CThe patient has a fragility fracture and a DEXA T-score of -2.8, which meets the criteria for osteoporosis. A fragility fracture is a sentinel event, significantly increasing the risk of subsequent fractures. The case emphasizes that antiresorptive agents, such as bisphosphonates (e.g., alendronate, zoledronic acid) or RANKL inhibitors (denosumab), are the critical initial pharmacological interventions to decrease osteoclast activity and prevent further bone degradation. Bisphosphonates are typically the first-line therapy due to their efficacy, cost-effectiveness, and long-standing evidence base.Option A (Initiate teriparatide)andOption B (Initiate romosozumab)are anabolic agents that stimulate osteoblast-mediated bone formation. While highly effective, they are generally reserved for patients with severe osteoporosis, those who fracture while on antiresorptive therapy, or those with very high fracture risk. They are typically not the first-line agents for initial management after a first fragility fracture unless there are specific contraindications to antiresorptives or a history of multiple fractures.Option D (Increase calcium and Vitamin D supplementation only)is insufficient. While calcium and Vitamin D supplementation form the baseline of all pharmacological regimens, they alone are not adequate to treat established osteoporosis with a fragility fracture. Active pharmacological intervention to either reduce bone resorption or stimulate bone formation is required.Option E (Prescribe calcitonin nasal spray)is a less potent antiresorptive agent, primarily used for pain relief in acute vertebral compression fractures and has limited efficacy in preventing future fractures compared to bisphosphonates or other agents. It is not considered a first-line treatment for osteoporosis.

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