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1. General Principles & Basic Science MCQs

Practice Set 240 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 4781

Topic: Physiology & Rehabilitation

A 32-year-old male felt a pop in his anterior axillary fold while bench pressing. Examination reveals loss of the anterior axillary contour and weakness in internal rotation. MRI shows rupture of the sternoclavicular head of the pectoralis major. What is the most common mechanism for this injury?

. Concentric contraction of the pectoralis major
. Eccentric contraction with the shoulder extended and externally rotated
. Isometric contraction at 90 degrees of abduction
. Direct blow to the anterior chest
. Eccentric contraction with the shoulder flexed and internally rotated

Correct Answer & Explanation

. Eccentric contraction with the shoulder extended and externally rotated

Explanation

Pectoralis major tendon ruptures classically occur during eccentric contraction with the arm extended and externally rotated. This places maximum tension on the sternoclavicular head, which is usually the first to fail during the eccentric phase of a bench press.

Question 4782

Topic: Surgical Anatomy & Approaches

A 28-year-old female falls onto her extended arm. Radiographs and CT show a capitellum fracture extending into the lateral trochlear ridge with significant posterior comminution (Dubberley Type 3B). What is the most appropriate surgical approach to achieve stable fixation?

. Medial over-the-top approach
. Extensile lateral approach with olecranon osteotomy
. Anterior Henry approach
. Lateral approach (Kocher) with posterior extension
. Arthroscopic-assisted percutaneous pinning

Correct Answer & Explanation

. Lateral approach (Kocher) with posterior extension

Explanation

Dubberley Type 3 fractures involve both the capitellum and trochlea, and the presence of posterior comminution (Type B) frequently necessitates a lateral or combined approach. A lateral approach with posterior extension allows adequate visualization to address both anterior and posterior articular surfaces securely.

Question 4783

Topic: Infection, Pharmacology & VTE

A patient sustains an open fracture of the proximal phalanx of the small finger. Following debridement and fixation, prophylactic antibiotics are typically administered. Which of the following is the most appropriate empirical antibiotic choice for an open hand fracture?

. Vancomycin
. Ciprofloxacin
. Cephalexin
. Cefazolin
. Metronidazole

Correct Answer & Explanation

. Cefazolin

Explanation

Cefazolin (a first-generation cephalosporin) is the most appropriate empirical antibiotic for open fractures, including those of the hand. It provides excellent coverage against Gram-positive organisms, particularly Staphylococcus aureus, which is the most common pathogen in open fractures. Vancomycin is reserved for MRSA. Ciprofloxacin and Metronidazole have different spectrums and are not first-line for this indication.

Question 4784

Topic: 1. General Principles & Basic Science

The Foucher's sign (lack of DIP flexion when the PIP joint is actively flexed) is used to assess the integrity of which tendon?

. Flexor digitorum superficialis
. Flexor digitorum profundus
. Extensor digitorum communis
. Flexor pollicis longus
. Extensor pollicis brevis

Correct Answer & Explanation

. Flexor digitorum superficialis

Explanation

Foucher's sign (or the isolated FDS test) assesses the integrity of the flexor digitorum superficialis (FDS) tendon. When the fingers are held in full extension (blocking the FDS of adjacent fingers), the patient is asked to flex a single finger at the PIP joint. If the FDS is intact, the PIP joint will flex. If the FDS is ruptured, this isolated PIP flexion will be absent or significantly weak, and the DIP joint will also fail to flex (as FDP would also be stretched).

Question 4785

Topic: Infection, Pharmacology & VTE

A patient presents with persistent pain, redness, and swelling in the DIP joint of the small finger, accompanied by a 'sausage digit' appearance. He has a history of psoriasis. What is the most likely diagnosis?

. Osteoarthritis
. Gout
. Rheumatoid arthritis
. Psoriatic arthritis
. Septic arthritis

Correct Answer & Explanation

. Psoriatic arthritis

Explanation

The combination of dactylitis ('sausage digit' swelling of an entire finger) affecting the DIP joints, especially in a patient with psoriasis, is highly characteristic of Psoriatic Arthritis. While gout can cause acute inflammation, it's typically monoarticular. RA rarely affects DIP joints primarily and typically causes symmetrical polyarthritis. Septic arthritis would be more acute and have systemic signs. Osteoarthritis involves cartilage degeneration without such inflammatory signs.

Question 4786

Topic: Surgical Anatomy & Approaches

Which is the most common complication following excision of a dorsal wrist ganglion?

. Infection
. Nerve injury (radial sensory nerve)
. Recurrence
. Stiffness
. Vascular injury

Correct Answer & Explanation

. Recurrence

Explanation

Despite successful surgical excision, recurrence remains the most common complication of dorsal wrist ganglion removal, with rates varying but generally quoted around 5-15%. While nerve injury (e.g., to the superficial radial nerve) and stiffness are potential complications, recurrence is reported most frequently. Infection and vascular injury are rarer.

Question 4787

Topic: 1. General Principles & Basic Science

What is the most common direction of thumb carpometacarpal (CMC) joint dislocation?

. Volar
. Radial
. Dorsal
. Ulnar
. Proximal

Correct Answer & Explanation

. Dorsal

Explanation

Dorsal dislocation is the most common direction for the thumb carpometacarpal (CMC) joint. This typically occurs from a direct force or an axial load on a flexed and adducted thumb. Volar, radial, and ulnar dislocations are rare.

Question 4788

Topic: 1. General Principles & Basic Science

Following a Zone II flexor tendon repair, early active mobilization protocols are commonly initiated. The predominant segmental vascular supply to the flexor tendons within this zone, which is critical for healing, is supplied primarily by which of the following structures?

. The epitenon plexus
. The vincula brevia and longa
. Synovial fluid diffusion alone
. The proper palmar digital arteries directly entering the tendon
. The musculotendinous junction

Correct Answer & Explanation

. The vincula brevia and longa

Explanation

In Zone II, the flexor tendons receive critical segmental intrinsic blood supply via the vincula brevia and longa, which arise from the transverse branches of the digital arteries. Preservation of the vincula during surgery is essential to prevent tendon necrosis.

Question 4789

Topic: 1. General Principles & Basic Science

A 65-year-old female with long-standing rheumatoid arthritis suddenly loses the ability to actively flex her thumb interphalangeal joint. What is the most likely etiology?

. Posterior interosseous nerve palsy
. Rupture of the FPL tendon over a scaphoid osteophyte
. Rupture of the EPL tendon over Lister's tubercle
. Anterior interosseous nerve palsy
. Trigger thumb

Correct Answer & Explanation

. Rupture of the FPL tendon over a scaphoid osteophyte

Explanation

Mannerfelt syndrome refers to the attrition rupture of the flexor pollicis longus (FPL) tendon in rheumatoid arthritis. This typically occurs as it rubs over a bony spur located on the volar scaphoid.

Question 4790

Topic: 1. General Principles & Basic Science

A patient presents with a suspected closed central slip rupture of the extensor mechanism at the PIP joint. During Elson's test, the PIP joint is flexed to 90 degrees and the patient is asked to actively extend against resistance. What finding indicates a complete rupture of the central slip?

. The DIP joint remains completely floppy and flexed
. The PIP joint forcefully extends past 0 degrees
. The DIP joint goes into rigid extension
. The lateral bands subluxate dorsally
. The MP joint goes into compensatory hyperextension

Correct Answer & Explanation

. The DIP joint goes into rigid extension

Explanation

In Elson's test, if the central slip is ruptured, the extensor effort is transmitted entirely through the lateral bands, which subluxate volarly at the PIP joint but forcefully pull the DIP joint into rigid extension. If intact, the DIP remains floppy.

Question 4791

Topic: 1. General Principles & Basic Science
A 22-year-old rugby player presents with an inability to actively flex the distal interphalangeal (DIP) joint of his ring finger after grabbing an opponent's jersey. Examination reveals tenderness in the palm, and ultrasound confirms the flexor digitorum profundus (FDP) tendon has retracted to the level of the lumbrical origin. Which Leddy-Packer type is this, and what is the required timeframe for primary repair?
. Type I, requiring repair within 7 to 10 days
. Type II, requiring repair within 3 weeks
. Type III, requiring repair within 3 weeks
. Type I, requiring repair within 4 to 6 weeks
. Type II, requiring repair within 7 to 10 days

Correct Answer & Explanation

. Type I, requiring repair within 7 to 10 days

Explanation

A Type I Leddy-Packer injury involves FDP retraction into the palm, disrupting all vincular blood supply. Primary repair must be performed within 7 to 10 days to prevent tendon necrosis and irreversible retraction.

Question 4792

Topic: Biology, Genetics & Bone Healing

A 65-year-old woman with osteoporosis presents with acute onset of severe back pain after bending over. Plain radiographs reveal a vertebral compression fracture at L1. Neurological examination is unremarkable. Which of the following is the most appropriate initial management?

. Immediate surgical stabilization with instrumentation.
. Vertebroplasty or kyphoplasty.
. Brace immobilization, analgesia, and osteoporosis management.
. Bed rest for 2 weeks followed by physical therapy.
. MRI to rule out spinal cord compression.

Correct Answer & Explanation

. Brace immobilization, analgesia, and osteoporosis management.

Explanation

For an osteoporotic vertebral compression fracture without neurological deficit, the initial management is typically non-operative. This includes pain management with analgesia, bracing (e.g., thoracolumbosacral orthosis - TLSO) for comfort and stability, and aggressive management of osteoporosis to prevent future fractures. Vertebroplasty or kyphoplasty can be considered if pain remains intractable despite conservative measures, but are not always first-line. Surgical stabilization is reserved for unstable fractures or those with neurological compromise. Bed rest for prolonged periods is generally discouraged due to deconditioning. An MRI is important if there's suspicion of neurological involvement or malignancy, but if the neurological exam is unremarkable, it might not be immediately emergent after initial radiographs confirm the fracture.

Question 4793

Topic: Infection, Pharmacology & VTE

A 70-year-old male with a prosthetic aortic valve on warfarin therapy sustains a displaced intertrochanteric hip fracture. His INR is 3.5. Which of the following is the most appropriate perioperative anticoagulant management?

. Proceed directly to surgery; continue warfarin.
. Stop warfarin; proceed to surgery immediately.
. Reverse warfarin with Vitamin K and FFP; proceed to surgery when INR is normal.
. Bridge with unfractionated heparin until INR is therapeutic, then proceed to surgery.
. Reverse warfarin with PCC and Vitamin K; aim for an INR <1.5 and proceed to surgery within 24 hours.

Correct Answer & Explanation

. Reverse warfarin with PCC and Vitamin K; aim for an INR <1.5 and proceed to surgery within 24 hours.

Explanation

For a patient with a displaced intertrochanteric hip fracture on warfarin, timely surgery is crucial to reduce morbidity and mortality. Reversing warfarin with Prothrombin Complex Concentrate (PCC) provides rapid correction of INR within hours, and Vitamin K provides sustained effect. The goal is typically to achieve an INR <1.5 to safely proceed with surgery, ideally within 24-48 hours. Stopping warfarin alone will take days to normalize INR, increasing DVT risk and delaying surgery. Bridging with unfractionated heparin is too slow and not indicated for emergent INR reversal. Continuing warfarin with an INR of 3.5 carries a significant bleeding risk. Immediate surgery without reversal is highly dangerous. Balancing the risk of bleeding with the need for prompt surgery is critical, and PCC combined with Vitamin K offers the quickest and safest pathway.

Question 4794

Topic: Surgical Anatomy & Approaches

A 42-year-old male sustains a transverse fracture of the acetabulum with a large posterior wall component. Which surgical approach provides the best direct access to address both the posterior wall and the posterior column?

. Ilioinguinal approach
. Kocher-Langenbeck approach
. Modified Stoppa approach
. Smith-Petersen approach
. Watson-Jones approach

Correct Answer & Explanation

. Kocher-Langenbeck approach

Explanation

The Kocher-Langenbeck is the workhorse posterior approach to the acetabulum. It provides excellent direct visualization for reduction and fixation of posterior wall, posterior column, and specific associated transverse fractures.

Question 4795

Topic: Surgical Anatomy & Approaches

A 28-year-old male sustains a posterior hip dislocation and an associated posterior wall acetabular fracture. Following closed reduction, a new ipsilateral foot drop is noted. Which nerve division is most likely injured?

. Tibial division of the sciatic nerve
. Common peroneal division of the sciatic nerve
. Superior gluteal nerve
. Obturator nerve
. Femoral nerve

Correct Answer & Explanation

. Common peroneal division of the sciatic nerve

Explanation

The sciatic nerve is at high risk during posterior hip dislocations and posterior wall fractures. The common peroneal division is lateral and securely tethered at the fibular head, making it significantly more susceptible to stretch injuries than the tibial division.

Question 4796

Topic: Biology, Genetics & Bone Healing

A 65-year-old male presents with a non-union of his tibial shaft fracture after 9 months. Investigations reveal normal calcium and PTH levels. Which of the following cellular mechanisms is most critically impaired in cases of delayed union or non-union of a long bone fracture?

. Osteoclast apoptosis
. Endochondral ossification
. Intramembranous ossification
. Fibroblast proliferation
. Chondrocyte hypertrophy

Correct Answer & Explanation

. Endochondral ossification

Explanation

Long bone fracture healing primarily occurs via endochondral ossification, where a cartilaginous callus forms and is subsequently replaced by woven bone, then remodeled into lamellar bone. Intramembranous ossification is more characteristic of flat bone healing or direct bone formation without a cartilage intermediate, but its impairment is less likely to be theprimarycritical issue in long bone non-union than a failure of the endochondral pathway. Osteoclast apoptosis is important for remodeling but not the initial bone formation. Fibroblast proliferation contributes to the initial hematoma and fibrous tissue, but effective healing requires subsequent cartilage and bone formation. Chondrocyte hypertrophy is a key step in endochondral ossification, and failure of this process would certainly contribute, but endochondral ossification encompasses the entire pathway including cartilage formation, hypertrophy, mineralization, and bone replacement.

Question 4797

Topic: 1. General Principles & Basic Science

Which of the following proteoglycans is the primary component responsible for the osmotic swelling pressure and load-bearing capacity of articular cartilage?

. Decorin
. Aggrecan
. Biglycan
. Versican
. Fibromodulin

Correct Answer & Explanation

. Aggrecan

Explanation

Aggrecan is the most abundant proteoglycan in articular cartilage and forms large aggregates with hyaluronic acid and link proteins. Its numerous negatively charged chondroitin sulfate and keratan sulfate glycosaminoglycan (GAG) chains attract water molecules, creating a significant osmotic swelling pressure within the cartilage matrix. This swelling pressure, constrained by the collagen network, is fundamental to the ability of cartilage to resist compressive loads and maintain its turgor and mechanical properties. Decorin, Biglycan, and Fibromodulin are smaller leucine-rich proteoglycans involved in collagen fibrillogenesis and tissue organization, but not primary load-bearing. Versican is found in many connective tissues but is less prominent in mature articular cartilage compared to aggrecan.

Question 4798

Topic: 1. General Principles & Basic Science

In peripheral nerve injury, Wallerian degeneration involves specific changes distal to the site of injury. Which of the following cellular events is the earliest to occur in the distal segment following axonal transection?

. Schwann cell proliferation
. Macrophage infiltration
. Axonal fragmentation
. Myelin sheath breakdown
. Chromatolysis in the neuronal cell body

Correct Answer & Explanation

. Axonal fragmentation

Explanation

Wallerian degeneration describes the process of axonal degeneration and subsequent myelin breakdown that occurs in the distal segment of a transected peripheral nerve. The earliest event in this cascade, typically beginning within 24-48 hours post-injury, is the fragmentation of the axon itself. This is rapidly followed by the breakdown of the myelin sheath into ovoids, and then infiltration by macrophages to clear cellular debris. Schwann cell proliferation occurs later as part of the regenerative process, and chromatolysis is a change in the neuronal cell body (proximal segment) rather than the distal segment.

Question 4799

Topic: Biology, Genetics & Bone Healing

Parathyroid hormone (PTH) plays a crucial role in calcium homeostasis. At the skeletal level, prolonged elevation of PTH primarily stimulates which of the following?

. Osteoblast differentiation
. Bone matrix mineralization
. Osteocyte apoptosis
. Osteoclastic bone resorption
. Collagen synthesis by osteoblasts

Correct Answer & Explanation

. Osteoclastic bone resorption

Explanation

Parathyroid hormone (PTH) has a complex effect on bone. Intermittent, low-dose administration of PTH (e.g., teriparatide) is anabolic, stimulating osteoblast activity and bone formation. However, sustained or chronically elevated levels of PTH, as seen in conditions like primary hyperparathyroidism, primarily promote osteoclastic bone resorption. PTH acts indirectly on osteoclasts by binding to receptors on osteoblasts, which then produce RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand) and inhibit osteoprotegerin (OPG). This shifts the balance towards increased osteoclast differentiation, activation, and survival, leading to enhanced bone resorption and calcium release from bone.

Question 4800

Topic: Biomechanics & Biomaterials

When designing a hip prosthesis, the material used for the femoral stem must withstand millions of cyclic loads. Which material property is most critical to prevent fatigue failure under these conditions?

. Yield strength
. Ultimate tensile strength
. Elastic modulus
. Endurance limit
. Hardness

Correct Answer & Explanation

. Endurance limit

Explanation

Fatigue failure is a common mode of failure for orthopedic implants due to the repetitive nature of physiological loading. The endurance limit (also known as the fatigue limit) is the maximum stress level below which a material can theoretically withstand an infinite number of loading cycles without failure. For materials like titanium alloys and cobalt-chrome alloys used in femoral stems, which are subjected to millions of cycles of stress during a patient's lifetime, ensuring the operating stresses remain below the endurance limit is paramount to prevent long-term fatigue failure. While yield strength and ultimate tensile strength are important for initial structural integrity, they do not directly predict performance under cyclic loading. Elastic modulus relates to stiffness, and hardness relates to resistance to indentation and wear, not directly fatigue.

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