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 1901
Topic: Biomechanics & Biomaterials
The torsional rigidity of a solid cylindrical intramedullary nail is proportional to its radius raised to which power?
Correct Answer & Explanation
. Fourth power (r^4)
Explanation
The polar moment of inertia, which determines a solid cylinder's resistance to torsion, is proportional to the radius raised to the fourth power (r^4). A small increase in nail diameter therefore yields an exponential increase in torsional rigidity.
Question 1902
Topic: Biomechanics & Biomaterials
A surgeon inadvertently mixes a titanium alloy fracture plate with 316L stainless steel screws. This dissimilar metal combination risks galvanic corrosion. Which material acts as the anode, and what is its fate?
Correct Answer & Explanation
. Stainless steel acts as the anode and undergoes accelerated corrosion
Explanation
In a galvanic couple between stainless steel and titanium, titanium is the more noble (cathodic) metal. Stainless steel acts as the anode and undergoes accelerated galvanic corrosion, which can lead to implant failure and adverse local tissue reactions.
Question 1903
Topic: Biomechanics & Biomaterials
Cortical bone exhibits viscoelastic behavior, meaning its mechanical properties depend on the loading rate. How does cortical bone adapt biomechanically when subjected to a high-velocity impact (fast loading rate) compared to a low-velocity force?
Correct Answer & Explanation
. It becomes stiffer and absorbs more energy before failure
Explanation
Due to its viscoelastic nature, cortical bone becomes both stiffer and stronger at higher loading rates. It absorbs significantly more energy prior to failure in high-velocity trauma, which is why high-energy fractures typically result in greater comminution and soft tissue damage upon energy release.
Question 1904
Topic: Biomechanics & Biomaterials
A fracture fixation plate manufactured from titanium alloy (Ti-6Al-4V) is compared to an identical plate made of 316L stainless steel. Which of the following correctly describes the titanium construct's biomechanical profile relative to the stainless steel construct?
Correct Answer & Explanation
. Lower modulus of elasticity resulting in lower stiffness.
Explanation
Titanium alloy has a modulus of elasticity (approx. 110 GPa) roughly half that of stainless steel (approx. 200 GPa). This gives titanium implants lower stiffness, resulting in less stress shielding and improved load sharing with the healing bone.
Question 1905
Topic: Infection, Pharmacology & VTE
Which of the following is the most common immediate complication following lumbar decompression for spinal stenosis?
Correct Answer & Explanation
. Dural tear.
Explanation
Correct Answer: CIncidental durotomy (dural tear) is the most common immediate complication during or after lumbar decompression surgery, with reported rates ranging from 3% to 17%. While other complications listed can occur, dural tears are particularly frequent due to the close proximity of the dura to the compressed structures being removed (e.g., hypertrophied ligamentum flavum, osteophytes). DVT/PE (Options A, D) are less common with appropriate prophylaxis. Surgical site infection (Option B) is a serious but less frequent immediate complication. New-onset foot drop (Option E) could occur due to nerve root injury, but dural tear is generally more common.
Question 1906
Topic: Infection, Pharmacology & VTE
A 50-year-old IV drug user presents with fever, severe T12 back pain, and new-onset paraparesis. Pending blood cultures and biopsy results, what is the most appropriate empiric intravenous antibiotic regimen?
Correct Answer & Explanation
. Vancomycin and Ceftriaxone
Explanation
Correct Answer: AIn a patient with risk factors for both MRSA (IV drug user) and Gram-negative bacteria (potentially via hematogenous spread or urinary source), empiric broad-spectrum coverage is essential. Vancomycin provides excellent coverage against MRSA, while a third-generation cephalosporin like Ceftriaxone provides good coverage against Gram-negative organisms, making this a common and appropriate empiric combination. Ciprofloxacin and Rifampin would be used for specific organisms (e.g., Cipro for Pseudomonas, Rifampin in combo for S. aureus after susceptibility). Penicillin G is too narrow. Doxycycline/Metronidazole targets anaerobic and atypical bacteria. Fluconazole/Amphotericin B are for fungal infections.
Question 1907
Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with acute right hip pain, fever of 39.0°C, and absolute refusal to bear weight. His ESR is 50 mm/hr and WBC is 14,000/mm³. According to the Kocher criteria, what is the approximate statistical probability that this child has septic arthritis?
Correct Answer & Explanation
. 99%
Explanation
The patient meets all four classic Kocher criteria: fever > 38.5°C, non-weight-bearing status, ESR > 40 mm/hr, and WBC > 12,000/mm³. The presence of all four criteria predicts a 99% probability of septic arthritis.
Question 1908
Topic: Biology, Genetics & Bone Healing
A 32-year-old woman presents with a lytic, expansile epiphyseal lesion in the proximal tibia. Histology shows mononuclear cells interspersed with multinucleated giant cells. Which of the following targeted therapies acts by binding to RANKL for the treatment of this lesion?
Correct Answer & Explanation
. Denosumab
Explanation
Denosumab is a human monoclonal antibody that binds directly to RANKL, inhibiting osteoclast formation and function. It is highly effective in the medical management of unresectable or recurrent giant cell tumors of bone.
Question 1909
Topic: Infection, Pharmacology & VTE
A 3-year-old boy presents with a 2-day history of refusal to bear weight on his right leg. He is febrile to 39.0 degrees C. His ESR is 50 mm/hr, CRP is 4.5 mg/dL, and WBC is 14,000/mm^3. Based on the classic Kocher criteria, what is the predictive probability that this child has a septic hip?
Correct Answer & Explanation
. 99%
Explanation
The classic Kocher criteria for a septic hip include non-weight-bearing, temperature > 38.5 C, ESR > 40 mm/hr, and WBC > 12,000/mm^3. The presence of all four criteria predicts a 99% probability of septic arthritis.
Question 1910
Topic: Infection, Pharmacology & VTE
A 55-year-old intravenous drug user presents with severe back pain. MRI reveals L3-L4 discitis and adjacent osteomyelitis without epidural compression. He is hemodynamically stable and neurologically intact. Blood cultures have been drawn but are pending. What is the next best step in management?
Correct Answer & Explanation
. CT-guided needle biopsy of the disc space
Explanation
In a hemodynamically stable, neurologically intact patient with suspected vertebral osteomyelitis/discitis, an image-guided biopsy should be performed to direct antibiotic therapy before empiric antibiotics are started.
Question 1911
Topic: Surgical Anatomy & Approaches
During the surgical approach for open reduction internal fixation of a proximal humerus fracture, the deltopectoral interval is utilized. Which of the following anatomical landmarks is crucial for identifying and safely developing this interval?
Correct Answer & Explanation
. C. The cephalic vein, which lies within the interval between the deltoid and pectoralis major muscles.
Explanation
Correct Answer: CThe cephalic vein is the crucial anatomical landmark for identifying and safely developing the deltopectoral interval. This vein consistently runs within the groove between the deltoid and pectoralis major muscles. By identifying the cephalic vein, the surgeon can safely separate these two muscles, either retracting the deltoid laterally and the pectoralis major medially, or vice versa, while protecting the vein (often retracted laterally with the deltoid) to gain access to the anterior aspect of the shoulder joint and proximal humerus.Option A is incorrect. The posterior border of the deltoid and anterior border of the teres major define a different surgical interval (posterior approach to the shoulder), not the deltopectoral interval.Option B is incorrect. While the deltopectoral interval is indeed between the deltoid and pectoralis major, simply stating their borders doesn't identify the specific, consistent landmark (the cephalic vein) that guides the dissection.Option D is incorrect. The axillary nerve runs around the surgical neck of the humerus and is a structure to be protectedafterthe deltopectoral interval is developed and deeper dissection proceeds. It does not define the interval itself.Option E is incorrect. The long head of the biceps tendon is an intra-articular structure and is encountered much deeper in the dissection, not as a landmark for the initial deltopectoral interval.
Question 1912
Topic: 1. General Principles & Basic Science
A 32-year-old male presents to the emergency department after a high-speed motor vehicle collision, sustaining a posterior sternoclavicular joint dislocation. During the initial assessment, he reports difficulty swallowing (dysphagia) and a change in voice (hoarseness).
Which of the following vital structures is MOST likely to be directly compressed or injured, contributing to the patient's dysphagia and voice changes?
Correct Answer & Explanation
. Esophagus
Explanation
Correct Answer: DThe posterior sternoclavicular joint is in close proximity to several critical mediastinal structures. Dysphagia is directly caused by compression or injury to theesophagus, which lies immediately posterior to the trachea and the SC joint. Voice changes (hoarseness) are typically due to injury to the recurrent laryngeal nerve. The recurrent laryngeal nerve runs in the tracheoesophageal groove, making it highly susceptible to injury when the esophagus or trachea are compressed or displaced by a posterior SC joint dislocation. Therefore, compression in this region can simultaneously affect both the esophagus (leading to dysphagia) and the recurrent laryngeal nerve (leading to voice changes). While the trachea (C) can be compressed leading to airway issues, the esophagus (D) is the more direct cause of dysphagia. The subclavian artery (A) and brachial plexus (B) are vascular and neurological structures, respectively, that would typically present with different symptoms (e.g., diminished pulses, arm paresthesias/weakness). The phrenic nerve (E) controls the diaphragm and its injury would lead to respiratory compromise, not dysphagia or voice changes.
Question 1913
Topic: 1. General Principles & Basic Science
A 28-year-old construction worker falls from a height, landing on his right shoulder. He presents with severe pain and a palpable deformity over his right sternoclavicular joint. A standard AP chest X-ray is inconclusive due to bony overlap. Given the high-energy mechanism, there is concern for a posterior dislocation and potential mediastinal involvement.
What is the most appropriate next diagnostic imaging study to accurately characterize the SC joint injury and assess for potential mediastinal involvement?
Correct Answer & Explanation
. CT scan with IV contrast
Explanation
Correct Answer: CThe gold standard for diagnosing and characterizing sternoclavicular (SC) joint dislocations, especially posterior dislocations, is aComputed Tomography (CT) scan with IV contrast. Axial cuts provide detailed information on the direction and degree of displacement relative to the manubrium. For posterior dislocations, a CT angiogram (CT-A) with IV contrast is mandatory to assess for impingement, compression, or laceration of mediastinal vessels and to evaluate the proximity of the clavicle to the trachea, esophagus, and lung apex. While a serendipity view radiograph (A) is helpful for initial screening, it lacks the sensitivity and specificity of CT, particularly for posterior dislocations and assessing vital structures. MRI (B) is useful for soft tissue injuries but less critical than CT for initial bony assessment and mediastinal structures. Ultrasound (D) has limited utility for deep bony and mediastinal structures. A lateral chest radiograph (E) would not provide sufficient detail for the SC joint.
Question 1914
Topic: 1. General Principles & Basic Science
A 25-year-old male presents to the emergency room after a motorcycle accident. He has an acute posterior sternoclavicular joint dislocation. On examination, he is dyspneic, has stridor, and his ipsilateral radial pulse is diminished compared to the contralateral side. A CT scan confirms posterior displacement of the medial clavicle impinging on the trachea and subclavian artery.
What is the absolute emergent indication for surgical intervention in this patient?
Correct Answer & Explanation
. Airway compromise and neurovascular compromise
Explanation
Correct Answer: CFor acute posterior sternoclavicular (SC) joint dislocations, the presence ofairway compromise (dyspnea, stridor) and neurovascular compromise (diminished pulses, subclavian artery impingement)constitutes an absolute emergent indication for surgical intervention. These symptoms indicate direct pressure on vital mediastinal structures, which can be life-threatening. While persistent pain and cosmetic deformity (A), risk of chronic instability (B), and patient's age/activity level (E) are considerations for surgical intervention in other contexts, they are not emergent absolute indications. Inability to perform closed reduction (D) would lead to open reduction, but theabsolute emergent indicationis the compromise of vital structures, which necessitates immediate action regardless of reduction method.
Question 1915
Topic: Surgical Anatomy & Approaches
During a surgical approach to the sternoclavicular joint for chronic instability, the surgeon aims to identify and reconstruct the primary static stabilizer of the joint, which resists superior displacement and provides significant resistance to anterior, posterior, and medial translation.
Which ligament is the surgeon primarily targeting for reconstruction based on its described function?
Correct Answer & Explanation
. Costoclavicular ligament
Explanation
Correct Answer: DThecostoclavicular ligament (rhomboid ligament)is described in the case as the primary static stabilizer of the SC joint. It consists of two laminae extending from the inferior surface of the medial clavicle to the superior surface of the first rib. It strongly resists superior displacement of the clavicle and provides significant resistance to anterior, posterior, and medial translation, as well as axial rotation. Its integrity is paramount for SC joint stability. The anterior (A) and posterior (B) sternoclavicular ligaments primarily resist posterior and anterior translation, respectively. The interclavicular ligament (C) primarily resists inferior displacement. The coracoclavicular ligament (E) stabilizes the acromioclavicular joint, not the sternoclavicular joint.
Question 1916
Topic: Surgical Anatomy & Approaches
A 32-year-old male sustains a closed, isolated mid-diaphyseal humeral shaft fracture after a fall from a bicycle. Initial radiographs confirm a spiral fracture pattern with 15 degrees of varus angulation and 1 cm of shortening. He presents with a new-onset radial nerve palsy, characterized by wrist drop and inability to extend his thumb and fingers. After 3 months of non-operative management with a functional brace, repeat radiographs show early callus formation but no significant change in angulation or shortening. Clinically, there is no improvement in his radial nerve function. What is the MOST appropriate next step in management?
Correct Answer & Explanation
. Proceed with surgical exploration of the radial nerve and internal fixation of the fracture, as there is no sign of recovery after 3 months.
Explanation
Correct Answer: BThe patient presents with a closed humeral shaft fracture and a new radial nerve palsy. The case states that after 3 months of non-operative management, there is no improvement in radial nerve function. According to the teaching case and current literature, for closed humeral shaft fractures with a new radial nerve palsy, initial non-operative management (observation) is generally recommended, with 70-90% spontaneous recovery expected within 3-6 months. However, if there is no sign of recovery after this period (typically 3-6 months), surgical exploration is indicated. Given the 3-month mark with no recovery, and the presence of a fracture that could benefit from fixation (even if angulation is borderline acceptable, the persistent nerve palsy warrants exploration), proceeding with surgical exploration of the radial nerve and internal fixation of the fracture is the most appropriate next step.Option A is incorrectbecause while most radial nerve palsies recover spontaneously, waiting another 3 months without any signs of recovery after the initial 3 months would delay potential nerve repair or decompression, especially when surgical fixation of the fracture is also a consideration.Option C is incorrectbecause while physical therapy is important, it does not address the lack of nerve recovery. Re-evaluating in 6 months without intervention for a non-recovering nerve at 3 months is a delay in definitive management.Option D is incorrectbecause while an EMG/NCS study can provide valuable information about the extent of nerve injury, the clinical absence of recovery after 3 months is a strong enough indication for exploration, especially when combined with the need for fracture fixation. The study might confirm the lack of recovery but would delay surgical intervention.Option E is incorrectbecause while a dynamic wrist-hand orthosis is appropriate for supporting the wrist and fingers in radial nerve palsy, scheduling for tendon transfers at 6 months without first exploring the nerve for potential repair or decompression would be premature. Tendon transfers are typically considered for permanent deficits after nerve recovery potential has been exhausted or exploration has confirmed irreparable damage.
Question 1917
Topic: Surgical Anatomy & Approaches
During an anterolateral approach to the mid-shaft humerus for a comminuted fracture, the surgeon retracts the biceps brachii muscle medially. The image below depicts the next layer of muscle encountered, which is then longitudinally incised to expose the humerus. Which of the following statements regarding the neurovascular structures in this immediate vicinity is MOST accurate?
Correct Answer & Explanation
. The musculocutaneous nerve is usually found in the fascial plane between the biceps and the exposed muscle, and should be retracted medially with the biceps.
Explanation
Correct Answer: CThe image depicts the brachialis muscle, which is encountered deep to the biceps brachii after medial retraction. The teaching case explicitly states: 'The musculocutaneous nerve (C5-C7) is located in the fascial plane between the biceps and brachialis. It typically pierces the coracobrachialis and then runs between the biceps and brachialis, supplying both. It then continues as the lateral antebrachial cutaneous nerve. Identify and protect the main trunk of the musculocutaneous nerve, usually by retracting it medially with the biceps.'Option A is incorrectbecause the main trunk of the musculocutaneous nerve typically lies superficial to the brachialis (between biceps and brachialis) and enters the brachialis in its mid-belly, not deep to it. Longitudinal incision of the brachialis can injure its distal branches, but the main trunk is usually protected by medial retraction of the biceps.Option B is incorrectbecause in the mid-shaft, the radial nerve is located in the spiral groove on the posterior aspect of the humerus. It only becomes more anterior in the distal third of the humerus. Therefore, it is not anterior to the brachialis in the mid-shaft and is not typically identified and protected laterally in the primary dissection plane of the anterolateral approach, though it is at risk from overly long screws or aggressive posterior dissection.Option D is incorrectbecause the profunda brachii artery accompanies the radial nerve in the spiral groove, on the posterior aspect of the humerus, not the musculocutaneous nerve, and is not a primary concern during the longitudinal incision of the brachialis muscle itself, unless dissection extends too far posteriorly.Option E is incorrectbecause the axillary nerve is a critical structure in the proximal humerus (approximately 5-7 cm distal to the acromion), not typically in the mid-shaft region where the brachialis is being incised. Its risk is primarily during proximal extension of the approach or aggressive deltoid retraction.
Question 1918
Topic: Surgical Anatomy & Approaches
A 68-year-old female with osteopenia presents with a comminuted mid-diaphyseal humeral fracture after a low-energy fall. She is scheduled for open reduction and internal fixation via an anterolateral approach. During pre-operative templating, the surgeon plans to use a locking compression plate (LCP) and bicortical screws. Which of the following statements regarding screw placement and potential neurovascular injury is MOST critical to consider?
Correct Answer & Explanation
. Careful measurement of screw length is paramount to avoid iatrogenic injury to the radial nerve, which lies posteriorly in the spiral groove.
Explanation
Correct Answer: CThe teaching case explicitly highlights the radial nerve as the most commonly injured nerve in humeral shaft fractures and their surgical treatment. It states: 'Though posterior, careless anterior dissection, overly aggressive subperiosteal stripping, or placement of excessively long bicortical screws can endanger the radial nerve.' The radial nerve runs in the spiral groove on the posterior aspect of the humerus in the mid-shaft, making it vulnerable to penetration by screws that are too long.Option A is incorrectbecause while the musculocutaneous nerve supplies the brachialis, the primary risk to its main trunk is during the initial dissection between the biceps and brachialis, or if the brachialis split is too lateral. Bicortical screw placement through the brachialis is not the primary mechanism of injury for the musculocutaneous nerve, especially compared to the radial nerve's vulnerability to screw length.Option B is incorrectbecause the axillary nerve wraps around the surgical neck of the humerus (proximal humerus), approximately 5-7 cm distal to the acromion. It is not at highest risk from distal bicortical screws; rather, it is at risk during proximal extension of the approach or aggressive deltoid retraction.Option D is incorrectbecause the brachial artery and veins are located medial to the biceps and coracobrachialis, generally not directly posterior to the humerus. While aggressive medial retraction could injure them, they are not typically at risk from bicortical screws placed from the anterolateral aspect through the posterior cortex.Option E is incorrectbecause the cephalic vein is a superficial vein in the subcutaneous tissue, typically retracted laterally. It is not at risk from bicortical screws placed into the bone, as these screws pass through the bone itself, not the superficial soft tissues where the cephalic vein resides.
Question 1919
Topic: Surgical Anatomy & Approaches
A 45-year-old construction worker undergoes an anterolateral approach for a mid-diaphyseal humeral fracture. Post-operatively, he develops a new radial nerve palsy. Which of the following is the LEAST likely cause of this iatrogenic injury during the surgical procedure?
Correct Answer & Explanation
. Excessive medial retraction of the biceps brachii muscle during exposure.
Explanation
Correct Answer: DThe teaching case describes the radial nerve's course in the spiral groove on the posterior aspect of the humerus. It explicitly states that 'careless anterior dissection, overly aggressive subperiosteal stripping, or placement of excessively long bicortical screws can endanger the radial nerve.' The radial nerve is vulnerable to direct injury from instruments or screws that extend too far posteriorly.Option A is incorrectbecause aggressive subperiosteal stripping on the posterior aspect of the humerus can directly injure the radial nerve, which lies in the spiral groove.Option B is incorrectbecause placement of an excessively long bicortical screw from the anterolateral plate is a classic mechanism of iatrogenic radial nerve injury, as the screw can penetrate the posterior cortex and impinge or transect the nerve.Option C is incorrectbecause a reduction clamp applied to the posterior cortex, especially if placed blindly or without careful consideration of the radial nerve's location, can directly compress or injure the nerve.Option D is the correct answer because excessive medial retraction of the biceps brachii muscle is LEAST likely to cause radial nerve injury.The biceps brachii is retracted medially to expose the brachialis. The radial nerve is located posteriorly in the spiral groove in the mid-shaft. Medial retraction of the biceps primarily risks the musculocutaneous nerve (which lies between the biceps and brachialis) or the brachial artery/veins (if retraction is excessively medial and deep), but not the radial nerve directly.Option E is incorrectbecause drilling through the far cortex without adequate protection or measurement is a direct precursor to placing an excessively long screw, thus putting the radial nerve at risk.
Question 1920
Topic: Surgical Anatomy & Approaches
A 55-year-old male undergoes an anterolateral approach for a proximal third humeral shaft fracture. During the approach, the surgeon needs to extend the dissection proximally to ensure adequate plate purchase. Which of the following anatomical considerations is MOST critical when extending the approach proximally?
Correct Answer & Explanation
. Protecting the axillary nerve, which wraps around the surgical neck approximately 5-7 cm distal to the acromion.
Explanation
Correct Answer: CThe teaching case specifically addresses the proximal humerus (proximal third) approach: 'The axillary nerve is the most critical structure in this region. It wraps around the surgical neck of the humerus approximately 5-7 cm distal to the acromion, supplying the deltoid and teres minor. Meticulous protection of this nerve is essential, particularly when reflecting the deltoid or extending the approach proximally.'Option A is incorrectbecause while the cephalic vein is an important superficial landmark, its identification and protection are generally part of the initial superficial dissection and less critical than the axillary nerve when extending the approach proximally into the deeper structures around the surgical neck.Option B is incorrectbecause the musculocutaneous nerve is primarily at risk during the mid-shaft approach, between the biceps and brachialis. While it's important to protect, the axillary nerve is the paramount concern in the proximal third.Option D is incorrectbecause the radial nerve pierces the lateral intermuscular septum in the distal third of the humerus to reach the anterior compartment. This is a concern for distal extensions, not proximal.Option E is incorrectbecause the brachialis muscle is typically incised in the mid-shaft and distal approaches. While it has dual innervation, the primary concern for proximal extension is the axillary nerve, not the brachialis incision.
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