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1. General Principles & Basic Science MCQs

Practice Set 205 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 4081

Topic: Surgical Anatomy & Approaches

A 25-year-old male sustains a closed transverse midshaft humerus fracture and presents with an immediate complete radial nerve palsy. He is treated with a functional brace. At what time point should an EMG/NCS be ordered if there is no clinical evidence of radial nerve recovery?

. 2 weeks
. 6 weeks
. 12 weeks
. 6 months
. 12 months

Correct Answer & Explanation

. 12 weeks

Explanation

For a closed humerus fracture with an immediate radial nerve palsy, observation is the standard of care as the vast majority are neuropraxias that will recover spontaneously. If there is no clinical evidence of recovery (e.g., return of brachioradialis function or wrist extension) by 12 weeks (3 months), an EMG/NCS should be obtained to evaluate for signs of reinnervation or severe denervation.

Question 4082

Topic: 1. General Principles & Basic Science

A 28-year-old competitive weightlifter feels a sudden 'pop' and sharp pain in his anterior chest while performing a heavy bench press. Examination reveals an asymmetric chest wall with loss of the anterior axillary fold and weakness in internal rotation and adduction. MRI confirms a complete rupture of the pectoralis major. Which tendon tear location is most common and has the best outcomes with surgical repair?

. Clavicular head at the muscle-tendon junction
. Sternal head at the muscle-tendon junction
. Avulsion of the entire tendon at its humeral insertion
. Intramuscular tear of the sternal head
. Avulsion from the sternum

Correct Answer & Explanation

. Avulsion of the entire tendon at its humeral insertion

Explanation

Pectoralis major ruptures most commonly occur in young athletic males during weightlifting (particularly bench press). The most common injury pattern is an avulsion of the sternal head (or the entire tendon) from its insertion on the lateral lip of the bicipital groove of the humerus. These injuries are best treated with early surgical repair (suture anchors or bone tunnels), which restores strength and cosmesis more reliably than nonoperative treatment.

Question 4083

Topic: 1. General Principles & Basic Science

A 28-year-old male bodybuilder feels a pop in his anterior axilla while bench-pressing. Physical examination reveals a loss of the normal anterior axillary fold and weakness in internal rotation. Which of the following best describes the anatomical footprint of the torn structure and the recommended treatment?

. It inserts on the lesser tuberosity; conservative management
. It inserts on the lateral lip of the bicipital groove; early surgical repair
. It inserts on the medial lip of the bicipital groove; early surgical repair
. It inserts on the coracoid process; conservative management
. It inserts on the greater tuberosity; early surgical repair

Correct Answer & Explanation

. It inserts on the lesser tuberosity; conservative management

Explanation

The pectoralis major inserts on the lateral lip of the bicipital groove. In young active patients with complete ruptures (especially at the musculotendinous junction or tendon insertion), early surgical repair is indicated to restore strength, particularly in adduction and internal rotation. The latissimus dorsi inserts on the floor of the groove, and the teres major inserts on the medial lip of the bicipital groove (Lady between two majors).

Question 4084

Topic: 1. General Principles & Basic Science

A 19-year-old male presents with dyspnea, dysphagia, and right upper chest pain after a rugby tackle. On examination, the medial right clavicle is less prominent than the left. Which of the following is the most appropriate next step in management?

. Immediate closed reduction in the emergency department using procedural sedation
. CT scan of the chest and consultation with cardiothoracic surgery prior to reduction in the OR
. Discharge with a figure-of-eight brace and routine orthopedic follow-up
. MRI of the sternoclavicular joint
. Open reduction via a trans-sternal approach

Correct Answer & Explanation

. Immediate closed reduction in the emergency department using procedural sedation

Explanation

The patient has a posterior sternoclavicular (SC) joint dislocation, which is a surgical emergency due to the proximity of the trachea, esophagus, and great vessels. A CT scan of the chest is the gold standard to confirm the diagnosis and assess mediastinal structures. Closed reduction should be attempted in the operating room (not the ED) with cardiothoracic surgery available in case of an acute vascular tear during the reduction maneuver.

Question 4085

Topic: Surgical Anatomy & Approaches

A 42-year-old man presents to the ER with his arm locked in hyperabduction over his head after a fall. Radiographs show an inferior glenohumeral dislocation (luxatio erecta). What is the most frequently injured neurovascular structure in this specific dislocation pattern?

. Axillary artery
. Axillary nerve
. Brachial artery
. Musculocutaneous nerve
. Median nerve

Correct Answer & Explanation

. Axillary artery

Explanation

Luxatio erecta is a rare inferior shoulder dislocation. The axillary nerve is the most commonly injured neurovascular structure (up to 60% of cases). While axillary artery injuries have the highest rate of occurrence in luxatio erecta compared to other dislocation directions, nerve injuries (specifically the axillary nerve) remain overall more frequent.

Question 4086

Topic: 1. General Principles & Basic Science

A 30-year-old competitive weightlifter feels a 'pop' in his anterior chest while performing a bench press. Examination reveals an asymmetric axillary fold. MRI confirms a rupture of the pectoralis major. Which head of the pectoralis major is most commonly injured in this mechanism, and where does it normally insert?

. Clavicular head; inserts proximal to the sternal head
. Clavicular head; inserts deep to the sternal head
. Sternal head; inserts proximal to the clavicular head
. Sternal head; inserts deep and proximal to the clavicular head
. Sternal head; inserts superficial and distal to the clavicular head

Correct Answer & Explanation

. Clavicular head; inserts proximal to the sternal head

Explanation

In a bench press injury, the sternal head is most commonly ruptured. The pectoralis major tendon undergoes a 180-degree twist before inserting on the lateral lip of the bicipital groove. Because of this twist, the sternal head inserts deep and proximal to the clavicular head. Thus, it is under maximal tension when the arm is extended and externally rotated (the bottom of the bench press).

Question 4087

Topic: 1. General Principles & Basic Science

A 25-year-old man sustains a closed, middle-third humeral shaft fracture. On presentation, he has a complete primary radial nerve palsy. He is managed non-operatively in a functional brace. At 12 weeks follow-up, there is radiographic evidence of bridging callus, but the patient still has 0/5 wrist extension, 0/5 finger extension, and absent brachioradialis function. EMG shows no evidence of reinnervation. What is the most appropriate next step?

. Continue bracing and observation for an additional 3 months
. Immediate tendon transfers for wrist and finger extension
. Exploration of the radial nerve and neurolysis or nerve grafting
. Open reduction and internal fixation of the humerus
. Injection of botulinum toxin to the flexor compartment

Correct Answer & Explanation

. Continue bracing and observation for an additional 3 months

Explanation

For a closed humeral shaft fracture with a primary radial nerve palsy, observation is the standard of care because 70-90% will spontaneously recover. Recovery usually begins by 3-4 months. If there is no clinical or electromyographic (EMG) evidence of recovery by 12 weeks (3 months), surgical exploration of the nerve is indicated. Since the fracture is healing, concurrent ORIF is not necessary.

Question 4088

Topic: 1. General Principles & Basic Science

A 35-year-old male presents with severe elbow stiffness 6 months after a complex fracture-dislocation. Radiographs demonstrate extensive heterotopic ossification (HO) bridging the radiocapitellar and ulnohumeral joints. His inflammatory markers are normal. The surgeon plans an open arthrolysis and excision of the HO. What is the most effective postoperative prophylaxis regimen to prevent recurrence of HO in this high-risk patient?

. Indomethacin for 3 days
. Single-dose localized radiation therapy (700 cGy) plus indomethacin
. High-dose oral corticosteroids for 2 weeks
. Postoperative continuous passive motion (CPM) machine only
. Intravenous bisphosphonates

Correct Answer & Explanation

. Indomethacin for 3 days

Explanation

Patients requiring surgical excision of extensive heterotopic ossification around the elbow are at extremely high risk for recurrence. The most effective prophylactic regimen is a combination of localized single-dose radiation therapy (typically 700 cGy administered within 24-48 hours postoperatively) and a nonsteroidal anti-inflammatory drug (NSAID) such as indomethacin for 3-6 weeks.

Question 4089

Topic: 1. General Principles & Basic Science

A 19-year-old rugby player sustains a posterior sternoclavicular (SC) joint dislocation. Closed reduction is planned in the operating room. Which of the following ligamentous structures is the most critical stabilizer resisting both anterior and posterior translation of the SC joint?

. Anterior sternoclavicular ligament
. Posterior sternoclavicular ligament
. Costoclavicular (rhomboid) ligament
. Interclavicular ligament
. Subclavius tendon

Correct Answer & Explanation

. Anterior sternoclavicular ligament

Explanation

Biomechanical studies have demonstrated that the posterior sternoclavicular ligament is the most important stabilizer against both anterior and posterior translation of the medial clavicle. Its complete disruption is necessary for an anterior or posterior SC joint dislocation to occur.

Question 4090

Topic: Surgical Anatomy & Approaches

A 28-year-old male sustains a closed transverse midshaft humerus fracture with an immediate complete radial nerve palsy. He is treated with a functional brace. At 12 weeks post-injury, the fracture is healing, but there is no clinical or EMG evidence of radial nerve recovery. What is the most appropriate next step?

. Continued observation for another 12 weeks
. Surgical exploration of the radial nerve
. Tendon transfers for wrist and finger extension
. Ulnar nerve fascicle transfer to the radial nerve
. Botulinum toxin injection to the flexor compartment

Correct Answer & Explanation

. Continued observation for another 12 weeks

Explanation

Most radial nerve palsies associated with closed humeral shaft fractures are neuropraxias or axonotmesis that resolve spontaneously within 3 to 4 months. If there are no clinical or electromyographic signs of recovery by 12 weeks, surgical exploration of the nerve is indicated.

Question 4091

Topic: 1. General Principles & Basic Science

What is the primary function of the structure at the tip of the probe in Figure 79? Review Topic

. Internal tibial rotation
. External tibial rotation
. Posterior tibial translation
. Anterior tibial translation
. Femoral internal rotation

Correct Answer & Explanation

. Internal tibial rotation

Explanation

The structure shown in the figure is the popliteus tendon. This structure is a continuation of the popliteus muscle belly and attaches more proximally through its hiatus in the lateral meniscus onto the lateral femoral epicondyle anterior and distal to the insertion of the lateral collateral ligament. The popliteus is a dynamic internal rotator of the tibia. The popliteus complex reinforces the posterior third of the lateral capsule and plays a major role in the dynamic and static stabilization of the lateral tibia on the femur, including restriction of external tibial rotation, posterior tibial translation, and varus rotation of the tibia.

Question 4092

Topic: 1. General Principles & Basic Science

Which of the following ligaments provides the major static restraint to lateral patellar displacement?

. Medial patellotibial
. Medial patellofemoral
. Medial patellomeniscal
. Lateral patellofemoral
. Lateral patellotibial

Correct Answer & Explanation

. Medial patellotibial

Explanation

The medial patellofemoral ligament is found to arise from the adductor tubercle and pass deep to the VMO and inserts on the proximal aspect of the medial patella and on the undersurface of the distal aspect of the quadriceps mechanism. The ligament varies in size in each patient but is the major soft tissue restraint to lateral displacement of the patella. Conlin and Garth, et al. found that the medial patellofemoral ligament contributed 53% of the total force against lateral displacement of the patella.The medial patellotibial band was found to be functionally unimportant and the medial patellomeniscal ligament was found to contribute 22% to the lateral displacement force.

Question 4093

Topic: 1. General Principles & Basic Science

A 25-year-old male presents with an obvious knee deformity following a high-energy rugby tackle. Physical examination reveals a transverse skin furrow (dimple sign) over the medial joint line. Closed reduction is attempted but is unsuccessful. What is the most likely anatomic block to reduction?

. Medial meniscus interposition
. Buttonholing of the medial femoral condyle through the anteromedial capsule
. Incarceration of the posterior cruciate ligament
. Avulsion of the medial collateral ligament into the joint
. Entrapment of the popliteal artery

Correct Answer & Explanation

. Medial meniscus interposition

Explanation

The "dimple sign" is pathognomonic for an irreducible posterolateral knee dislocation. It is caused by the medial femoral condyle buttonholing through the anteromedial joint capsule, necessitating an open reduction.

Question 4094

Topic: 1. General Principles & Basic Science

A 29-year-old female presents to the ER with a suspected traumatic knee arthrotomy following a deep laceration just medial to the patella. Radiographs show no fractures. A saline load test is planned. Which of the following statements regarding the saline load test is most accurate?

. A 50 mL injection of normal saline is sufficient to rule out an arthrotomy in most patients.
. The addition of methylene blue has been shown to significantly increase the sensitivity of the test.
. A computed tomography (CT) scan is generally less sensitive than a saline load test for detecting small arthrotomies.
. A minimum of 155 mL of fluid is required to achieve 95% sensitivity for detecting a knee arthrotomy.
. The test should be performed by injecting fluid directly through the traumatic wound.

Correct Answer & Explanation

. A minimum of 155 mL of fluid is required to achieve 95% sensitivity for detecting a knee arthrotomy.

Explanation

Studies have shown that to achieve a 95% sensitivity in detecting traumatic knee arthrotomies using the saline load test, an average injection volume of 155 mL is required. CT scans are actually more sensitive for detecting intra-articular air than the saline load test.

Question 4095

Topic: Biology, Genetics & Bone Healing

A 65-year-old woman with a history of osteoporosis on long-term alendronate therapy complains of a 3-month history of prodromal lateral left thigh pain. Radiographs reveal localized lateral cortical thickening of the subtrochanteric femur with a transverse radiolucent line, but no complete fracture. What is the most appropriate management?

. Discontinue alendronate, begin protected weight-bearing, and schedule for prophylactic cephalomedullary nailing.
. Switch alendronate to zoledronic acid and prescribe a cane.
. Observation and repeat radiographs in 6 months.
. Core decompression of the subtrochanteric femur.
. Application of a hinged fracture brace and immediate full weight-bearing.

Correct Answer & Explanation

. Discontinue alendronate, begin protected weight-bearing, and schedule for prophylactic cephalomedullary nailing.

Explanation

This patient has an incomplete atypical femur fracture (AFF) associated with long-term bisphosphonate use, symptomatic with a radiolucent line. Standard of care includes stopping the bisphosphonate and performing prophylactic intramedullary nailing to prevent complete completion.

Question 4096

Topic: Infection, Pharmacology & VTE

Methicillin-resistant staphylococcus aureus (MRSA) develops its resistance to penicillinase-stable antibiotics via which of the following actions?

. Alterations in cell wall permeability
. Genetic mutation
. Creation of a biofilm barrier
. Production of active efflux pump
. Altering peptidoglycan subunits

Correct Answer & Explanation

. Genetic mutation

Explanation

After the introduction of penicillins, bacteria developed the ability to hydrolyze these antibiotics using B-lactamase. In response, penicillinase-stable antibiotics were developed, the first of which was methicillin, since replaced with oxacillin and nafcillin. Drug resistance to this class of antibiotics is achieved via a genetic mutation of mecA encoding an altered penicillin binding protein. The gene product of this mutation, PBPa has a low affinity for these antibiotics and cannot be inhibited by them. Altering cell wall permeability is found in resistance to tetracyclines, quinolones, and trimethoprim, as well as B-lactam antibiotics. Biofilm barriers are produced by bacteria such as salmonella. Active efflux pumps provide resistance to erythromycin and tetracycline, and altering the peptidoglycan subunit is found in resistance to vancomycin.

Question 4097

Topic: 1. General Principles & Basic Science

What factor induces myofibrillar muscle protein synthesis (MPS)? Review Topic

. Aerobic exercise
. Anabolic hormones (growth hormone/testosterone)
. Resistance exercise above 60% 1-repetition maximum (RM)
. High-repetition exercise at mid intensity (30% 1-RM)

Correct Answer & Explanation

. Resistance exercise above 60% 1-repetition maximum (RM)

Explanation

Resistance exercise induces myofibrillar MPS that drives muscle hypertrophy. Growth hormone/testosterone does not influence MPS in acute response to exercise or adaptive response of muscle hypertrophy to resistance exercise. Recombinant growth hormone administration does not affect MPS. Anabolic steroids do not drive adaptation in humans; an intrinsic autocrine/paracrine factor and mechanotransduction process is involved. Exercise above 60% 1-RM represents anabolic ceiling. There is a sigmoidal dose response to resistance exercise, maximum MPS occurs at > 60% 1-RM. Aerobic-zone exercise does not result in hypertrophy of skeletal muscle, but it does increase oxidative capacity.

Question 4098

Topic: 1. General Principles & Basic Science
An 18-year-old man sustains an injury to the right brachial plexus after falling off his bicycle. Examination reveals no rhomboideus major or minor muscle function. This finding most likely indicates a preganglionic injury to which of the following nerve roots?
. C4
. C5
. C5 and C6
. C7
. C8 and T1

Correct Answer & Explanation

. C5

Explanation

The rhomboideus major and minor muscles are innervated by the dorsal scapular nerve, which is supplied entirely by the C5 nerve root. The dorsal scapular nerve arises just distal to the dorsal root ganglion of the C5 nerve root. A functioning rhomboid muscle indicates that an injury involving C5 nerve root fibers must be postganglionic or distal to the C5 dorsal root ganglion. Conversely, loss of function indicates a preganglionic injury.

Question 4099

Topic: 1. General Principles & Basic Science
The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is used to help distinguish necrotizing fasciitis from severe cellulitis. Which of the following laboratory values is a specific component that adds points to the LRINEC score?
. Serum potassium > 5.5 mmol/L
. Serum sodium < 135 mmol/L
. Platelet count < 100,000 /mcL
. Serum calcium < 8.0 mg/dL
. Blood urea nitrogen (BUN) > 30 mg/dL

Correct Answer & Explanation

. Serum sodium < 135 mmol/L

Explanation

The LRINEC score incorporates six laboratory parameters: CRP (>150 mg/L), WBC count (elevated, with higher points for >25), Hemoglobin (decreased, <13.5 or <11), Serum Sodium (<135 mmol/L adds 2 points), Serum Creatinine (>1.41 mg/dL), and Glucose (>180 mg/dL). Platelets, calcium, potassium, and BUN are not components of the LRINEC score.

Question 4100

Topic: Infection, Pharmacology & VTE

A 70-year-old female with a chronic staphylococcal periprosthetic joint infection of the hip is treated with a two-stage exchange arthroplasty. Her systemic antibiotic regimen includes rifampin due to its excellent biofilm penetration. What is the molecular mechanism of action of rifampin?

. Binds to the 30S ribosomal subunit
. Binds to the 50S ribosomal subunit
. Inhibits DNA gyrase
. Inhibits DNA-dependent RNA polymerase
. Inhibits bacterial cell wall cross-linking

Correct Answer & Explanation

. Inhibits DNA-dependent RNA polymerase

Explanation

Rifampin is highly active against Staphylococcal biofilms because it penetrates the biofilm matrix well and acts by binding to and inhibiting bacterial DNA-dependent RNA polymerase, thereby preventing RNA transcription. It must always be used in combination with other agents to prevent the rapid emergence of resistance.

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