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1. General Principles & Basic Science MCQs

Practice Set 607 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 12121

Topic: Surgical Anatomy & Approaches

A 28-year-old male is involved in a motor vehicle collision and sustains a traumatic posterior dislocation of the right hip. Which specific nerve division is most frequently injured in association with this specific dislocation?

. Femoral nerve
. Obturator nerve
. Tibial division of the sciatic nerve
. Peroneal division of the sciatic nerve
. Superior gluteal nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Sciatic nerve injury occurs in approximately 10-20% of posterior hip dislocations. The peroneal (fibular) division is particularly susceptible to stretch and compression injuries due to its more lateral, superficial position and its tight distal tethering at the fibular head.

Question 12122

Topic: Biomechanics & Biomaterials

When selecting metallic alloys for orthopedic implants, engineers often consider the modulus of elasticity to minimize stress shielding of the surrounding bone. Which of the following implant materials has a modulus of elasticity that most closely approximates that of cortical bone?

. Stainless steel
. Titanium alloy
. Cobalt-chromium alloy
. Polymethylmethacrylate (PMMA)
. Tantalum

Correct Answer & Explanation

. Stainless steel

Explanation

Titanium and its alloys have a modulus of elasticity that is much closer to that of cortical bone compared to stiffer metals like cobalt-chromium or stainless steel. This property helps ensure better load sharing and reduces the risk of long-term stress shielding and bone resorption.

Question 12123

Topic: 1. General Principles & Basic Science

A 32-year-old bodybuilder feels a pop in his anterior axilla while performing a heavy bench press. Exam reveals an asymmetrical axillary fold. MRI confirms a complete tear of the pectoralis major. Which anatomical structure is most commonly injured in this mechanism?

. Sternal head at the musculotendinous junction
. Clavicular head at the musculotendinous junction
. Sternal head at the humeral insertion
. Clavicular head at the humeral insertion
. Muscle belly of the sternal head

Correct Answer & Explanation

. Sternal head at the musculotendinous junction

Explanation

Pectoralis major ruptures most commonly occur during eccentric loading and almost exclusively involve avulsion of the sternal head at the humeral insertion. The sternal head tendon lies posterior to the clavicular head tendon at the insertion site.

Question 12124

Topic: Surgical Anatomy & Approaches

During a Latarjet procedure for recurrent anterior shoulder instability, which nerve is at greatest risk of iatrogenic injury during coracoid osteotomy and mobilization?

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

Correct Answer & Explanation

. Axillary nerve

Explanation

The musculocutaneous nerve enters the coracobrachialis 5-8 cm distal to the coracoid process. It is highly susceptible to traction injury during vigorous medial retraction and coracoid mobilization.

Question 12125

Topic: Surgical Anatomy & Approaches

A 38-year-old female sustains a Dubberley Type 3B capitellum fracture (involving the capitellum and trochlea with posterior condylar comminution). What surgical approach provides the most optimal exposure for fixation of the posterior comminution?

. Kocher approach
. Kaplan approach
. Extended lateral (column) approach
. Posterior midline approach with olecranon osteotomy
. Medial over-the-top approach

Correct Answer & Explanation

. Kocher approach

Explanation

Dubberley Type 3B fractures involve both the capitellum and trochlea, accompanied by posterior condylar comminution. A posterior midline approach with an olecranon osteotomy provides the necessary visualization for addressing the posterior articular comminution and restoring the joint surface.

Question 12126

Topic: Physiology & Rehabilitation

A 32-year-old bodybuilder feels a pop in his anterior axilla while bench pressing. Examination reveals loss of the anterior axillary fold and weakness in internal rotation. MRI confirms a complete rupture of the pectoralis major tendon. Which segment of the muscle is most commonly injured in this mechanism?

. Clavicular head at the musculotendinous junction
. Sternal head at its humeral insertion
. Clavicular head at its humeral insertion
. Sternal head at the musculotendinous junction
. Abdominal head at the costal margin

Correct Answer & Explanation

. Clavicular head at the musculotendinous junction

Explanation

Pectoralis major ruptures typically occur during eccentric contraction, most commonly involving the sternal head at the humeral insertion. The sternal head fibers insert deep and proximal to the clavicular fibers, placing them at maximal stretch during the bottom phase of the bench press.

Question 12127

Topic: Surgical Anatomy & Approaches

A 68-year-old female sustains a 3-part proximal humerus fracture. She demonstrates isolated weakness of the deltoid and decreased sensation over the lateral shoulder. Which structural pathway does the injured nerve traverse to innervate these areas?

. Quadrangular space
. Triangular space
. Triangular interval
. Spinoglenoid notch
. Spiral groove

Correct Answer & Explanation

. Quadrangular space

Explanation

The axillary nerve innervates the deltoid and provides sensation to the lateral shoulder. It travels through the quadrangular space, which is bounded by the teres minor, teres major, long head of the triceps, and the surgical neck of the humerus.

Question 12128

Topic: Physiology & Rehabilitation

A 40-year-old weightlifter presents with a sudden 'pop' and pain in his anterior chest wall while performing a heavy bench press. Examination reveals loss of the anterior axillary fold and weakness in internal rotation. If surgical repair is pursued, to which anatomic footprint should the torn tendon be reattached?

. Medial lip of the bicipital groove
. Lateral lip of the bicipital groove
. Coracoid process
. Lesser tuberosity
. Sublime tubercle

Correct Answer & Explanation

. Medial lip of the bicipital groove

Explanation

The pectoralis major inserts on the lateral lip of the bicipital groove. Tears most commonly occur at the sternal head insertion during eccentric contraction, and anatomic repair to this footprint maximizes strength return.

Question 12129

Topic: Surgical Anatomy & Approaches

A 34-year-old woman presents with a complex coronal shear fracture of the capitellum with extensive posterior comminution extending into the trochlea (Dubberley Type 3B). Which surgical approach provides the most optimal visualization for reduction and fixation of this articular extension?

. Standard Kocher approach
. Kaplan approach
. Extensile lateral (column) approach
. Posterior midline approach with olecranon osteotomy
. Medial over-the-top approach

Correct Answer & Explanation

. Standard Kocher approach

Explanation

Dubberley Type 3B fractures involve both the capitellum and trochlea with posterior comminution. A posterior midline approach with an olecranon osteotomy provides the necessary wide exposure to visualize the entire distal articular surface and address posterior defects.

Question 12130

Topic: 1. General Principles & Basic Science

A 32-year-old male feels a "pop" in his anterior chest while bench pressing. Examination reveals loss of the anterior axillary fold. MRI confirms a complete rupture of the sternoclavicular head of the pectoralis major tendon. Where is the anatomical insertion site of this torn tendon head on the humerus relative to the clavicular head?

. Proximal and anterior
. Distal and posterior
. Proximal and posterior
. Distal and anterior
. Directly medial

Correct Answer & Explanation

. Proximal and anterior

Explanation

The pectoralis major tendon twists 180 degrees before inserting on the lateral lip of the bicipital groove. This rotation causes the sternoclavicular head to insert deep (posterior) and distal to the clavicular head.

Question 12131

Topic: Surgical Anatomy & Approaches

A 30-year-old overhead laborer presents with vague posterior shoulder pain and numbness over the lateral deltoid. MRI shows isolated fatty infiltration and atrophy of the teres minor. Which vascular structure is most likely being compressed alongside the affected nerve?

. Anterior humeral circumflex artery
. Posterior humeral circumflex artery
. Suprascapular artery
. Subscapular artery
. Circumflex scapular artery

Correct Answer & Explanation

. Anterior humeral circumflex artery

Explanation

The patient has Quadrilateral Space Syndrome, characterized by compression of the axillary nerve and the posterior humeral circumflex artery. This compression leads to isolated teres minor atrophy and sensory loss over the lateral deltoid.

Question 12132

Topic: Surgical Anatomy & Approaches

A surgeon is utilizing the direct anterior approach (Smith-Petersen) for a total hip arthroplasty. The superficial surgical interval utilizes a true internervous plane. Which of the following identifies the correct muscles and their respective innervations that form this superficial plane?

. Tensor fasciae latae (Superior gluteal nerve) and Sartorius (Femoral nerve)
. Rectus femoris (Femoral nerve) and Tensor fasciae latae (Superior gluteal nerve)
. Gluteus medius (Superior gluteal nerve) and Tensor fasciae latae (Superior gluteal nerve)
. Sartorius (Femoral nerve) and Iliopsoas (Femoral nerve)
. Gluteus maximus (Inferior gluteal nerve) and Gluteus medius (Superior gluteal nerve)

Correct Answer & Explanation

. Tensor fasciae latae (Superior gluteal nerve) and Sartorius (Femoral nerve)

Explanation

The direct anterior approach to the hip uses the Smith-Petersen interval. The superficial internervous plane is between the Sartorius (innervated by the femoral nerve) and the Tensor Fasciae Latae (TFL, innervated by the superior gluteal nerve). The deep internervous plane is between the Rectus Femoris (femoral nerve) and the Gluteus Medius (superior gluteal nerve).

Question 12133

Topic: Biomechanics & Biomaterials

The introduction of highly cross-linked polyethylene (HXLPE) has significantly reduced wear rates and osteolysis in total hip arthroplasty. However, the electron beam or gamma irradiation used to create the cross-linking alters the mechanical properties of the plastic. Which of the following mechanical changes is an adverse consequence of increased irradiation and cross-linking?

. Increased ultimate tensile strength
. Increased resistance to fatigue crack propagation
. Decreased yield strength, ductility, and fracture toughness
. Increased generation of free radicals leading to accelerated in vivo oxidation
. Decreased modulus of elasticity resulting in component deformation

Correct Answer & Explanation

. Increased ultimate tensile strength

Explanation

While cross-linking polyethylene dramatically improves adhesive and abrasive wear resistance, it compromises several structural mechanical properties. Highly cross-linked polyethylene has decreased yield strength, decreased ultimate tensile strength, decreased ductility, and decreased fracture toughness compared to conventional polyethylene. Free radicals are generated during irradiation, but modern processing involves melting or annealing to quench these radicals, preventing oxidation.

Question 12134

Topic: Surgical Anatomy & Approaches

During a primary THA utilizing a posterior approach, the surgeon places a retractor anteriorly, hooking it over the anterior acetabular rim to retract the soft tissues and improve visualization of the anterior labrum. Which nerve is most at risk of injury due to compression from this specific retractor?

. Sciatic nerve
. Superior gluteal nerve
. Femoral nerve
. Obturator nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

Placement of an anterior retractor over the anterior rim of the acetabulum during a THA can compress the soft tissues containing the iliopsoas muscle and the femoral nerve, leading to a postoperative femoral nerve palsy. The sciatic nerve is at risk posteriorly, while the superior gluteal nerve is at risk with proximal propagation of a direct lateral or anterolateral approach.

Question 12135

Topic: Biology, Genetics & Bone Healing

A patient with a history of severe heterotopic ossification (Brooker Class IV) following a primary THA is undergoing revision surgery. Prophylactic radiation therapy is planned to prevent recurrence. To maximize clinical efficacy, when is the optimal timeframe to administer the radiation dose?

. Within 24 hours preoperatively or within 72 hours postoperatively
. Between 7 to 10 days postoperatively
. 14 days preoperatively to allow for tissue conditioning
. Strictly in the intraoperative setting using a shielded beam
. One month postoperatively, after the acute inflammatory phase subsides

Correct Answer & Explanation

. Within 24 hours preoperatively or within 72 hours postoperatively

Explanation

Single-dose radiation therapy (typically 700-800 cGy) is highly effective for preventing heterotopic ossification. It works by preventing the differentiation of pluripotential mesenchymal stem cells into osteoblasts. To be effective, it must be administered while these cells are proliferating, which is optimally within 24 hours prior to surgery or within 72 hours after surgery.

Question 12136

Topic: 1. General Principles & Basic Science

An MRI of the knee in an adult patient with osteoarthritis incidentally reveals a large Baker's cyst. Based on normal anatomical boundaries, a true popliteal (Baker's) cyst communicates with the knee joint space between which two specific structures?

. Medial head of the gastrocnemius and semimembranosus tendons
. Lateral head of the gastrocnemius and biceps femoris tendons
. Popliteus tendon and the lateral collateral ligament
. Semitendinosus and semimembranosus tendons
. Soleus muscle and the medial head of the gastrocnemius

Correct Answer & Explanation

. Medial head of the gastrocnemius and semimembranosus tendons

Explanation

A classic Baker's cyst is a distention of the gastrocnemius-semimembranosus bursa. It typically communicates with the posterior knee joint through a weak point in the capsule located precisely between the medial head of the gastrocnemius and the semimembranosus tendon.

Question 12137

Topic: Surgical Anatomy & Approaches

During a direct anterior approach (Smith-Petersen) for a primary total hip arthroplasty, the surgeon develops the superficial internervous plane. Which two nerves supply the specific muscles that define the boundaries of this superficial plane?

. Femoral nerve and Obturator nerve
. Superior gluteal nerve and Inferior gluteal nerve
. Femoral nerve and Superior gluteal nerve
. Sciatic nerve and Femoral nerve
. Obturator nerve and Superior gluteal nerve

Correct Answer & Explanation

. Femoral nerve and Obturator nerve

Explanation

The superficial internervous plane of the direct anterior approach to the hip is between the sartorius and the tensor fasciae latae (TFL). The sartorius is innervated by the femoral nerve, while the TFL is innervated by the superior gluteal nerve. This true internervous plane allows access to the hip joint without denervating the surrounding musculature.

Question 12138

Topic: Infection, Pharmacology & VTE
A 28-year-old professional athlete sustains an acute knee injury. Physical examination reveals gross valgus laxity at both 30 degrees and 0 degrees of flexion. MRI confirms an isolated Grade III tear of the medial collateral ligament (MCL), specifically noting a distal avulsion of the superficial MCL from the tibia, with the torn ligament end displaced superficial to the pes anserinus tendons. What is the most appropriate management strategy for this specific injury pattern?
. Hinged knee brace and functional rehabilitation for 6 weeks
. Acute surgical repair or reconstruction of the MCL
. Casting the knee in 30 degrees of flexion for 4 weeks
. Corticosteroid injection at the tibial insertion followed by progressive weight bearing
. Arthroscopic meniscectomy and observation of the MCL

Correct Answer & Explanation

. Acute surgical repair or reconstruction of the MCL

Explanation

While the vast majority of isolated MCL tears (even Grade III) can be treated nonoperatively with hinged bracing, a distal tibial avulsion of the superficial MCL that flips superficial to the pes anserinus tendons creates an 'MCL Stener-like lesion.' Because the pes anserinus physically blocks the torn MCL from anatomically resting against its tibial insertion footprint, healing is prohibited. Therefore, this specific pattern is an absolute indication for acute surgical repair.

Question 12139

Topic: Biomechanics & Biomaterials
Highly cross-linked polyethylene (HXLPE) was developed to reduce wear rates in total hip arthroplasty. Which of the following represents the primary mechanism by which cross-linking reduces wear compared to conventional ultra-high-molecular-weight polyethylene (UHMWPE)?
. Elimination of free radicals through remelting or annealing.
. Formation of intermolecular covalent bonds that prevent polymer chain alignment, fibril formation, and subsequent pull-out.
. Decreased overall crystallinity of the polymer matrix.
. Increased oxidative degradation resistance at the bearing surface.
. Conversion of the amorphous region to a strictly crystalline region.

Correct Answer & Explanation

. Formation of intermolecular covalent bonds that prevent polymer chain alignment, fibril formation, and subsequent pull-out.

Explanation

Highly cross-linked polyethylene (HXLPE) undergoes irradiation to break polymer chains, which then recombine to form strong intermolecular covalent bonds (cross-links). This prevents the linear polymer chains from aligning in the direction of motion, completely disrupting the process of fibril formation and subsequent adhesive wear (chain pull-out). While remelting and annealing eliminate free radicals to prevent oxidation, the cross-linking itself is what primarily reduces the mechanical wear.

Question 12140

Topic: Surgical Anatomy & Approaches

The direct anterior (Smith-Petersen) approach is frequently utilized in modern primary total hip arthroplasty due to its intermuscular and internervous properties. Which of the following accurately describes the true internervous superficial surgical interval utilized in this approach?

. Sartorius (Femoral nerve) and Tensor fasciae latae (Superior gluteal nerve).
. Gluteus medius (Superior gluteal nerve) and Tensor fasciae latae (Superior gluteal nerve).
. Rectus femoris (Femoral nerve) and Gluteus medius (Superior gluteal nerve).
. Gluteus maximus (Inferior gluteal nerve) and Gluteus medius (Superior gluteal nerve).
. Pectineus (Femoral nerve) and Adductor longus (Obturator nerve).

Correct Answer & Explanation

. Sartorius (Femoral nerve) and Tensor fasciae latae (Superior gluteal nerve).

Explanation

The direct anterior approach utilizes the Smith-Petersen interval. Superficially, this plane lies between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). Deeply, it passes between the rectus femoris (femoral nerve) and the gluteus medius (superior gluteal nerve). This makes it a true internervous and intermuscular plane. The interval between the gluteus medius and TFL is the Watson-Jones (anterolateral) approach, which is intermuscular but not internervous (both are superior gluteal nerve).

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