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1. General Principles & Basic Science MCQs

Practice Set 350 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 6981

Topic: Infection, Pharmacology & VTE

A 62-year-old diabetic patient presents with a deep plantar neuropathic ulcer under the first metatarsal head. On examination, a sterile metal probe smoothly passes through the ulcer base and strikes hard, gritty bone. Which of the following is true regarding this clinical finding?

. It has a high false-positive rate in the presence of surrounding cellulitis.
. It has a high positive predictive value for underlying osteomyelitis.
. It is diagnostic of a Wagner Grade 1 ulcer.
. It mandates immediate primary below-knee amputation.
. It requires confirmation with an urgent MRI before initiating any antibiotics.

Correct Answer & Explanation

. It has a high false-positive rate in the presence of surrounding cellulitis.

Explanation

The probe-to-bone test is highly predictive of osteomyelitis in the presence of an infected diabetic foot ulcer. It has a high positive predictive value, often negating the absolute need for advanced imaging like MRI before starting tailored therapy.

Question 6982

Topic: Infection, Pharmacology & VTE

A 60-year-old diabetic woman with a history of recurrent forefoot ulcers and osteomyelitis presents for preoperative evaluation for a planned Syme amputation. Which of the following noninvasive vascular parameters is the most reliable predictor of successful wound healing at this specific amputation level?

. Absolute ankle systolic pressure > 70 mm Hg
. Transcutaneous oxygen tension (TcPO2) > 20 mm Hg
. Ankle-Brachial Index (ABI) > 0.30
. Serum albumin > 2.5 g/dL
. Total lymphocyte count > 1000/mm3

Correct Answer & Explanation

. Absolute ankle systolic pressure > 70 mm Hg

Explanation

Healing of a Syme or hindfoot amputation typically requires an absolute ankle systolic pressure greater than 70 mm Hg. Toe pressures > 40 mm Hg are used to predict forefoot healing, while a minimum serum albumin of 3.0 g/dL is generally required for reliable soft tissue healing.

Question 6983

Topic: Infection, Pharmacology & VTE

Which of the following clinical tests has the highest positive predictive value for diagnosing osteomyelitis beneath a diabetic foot ulcer?

. Erythrocyte sedimentation rate (ESR) > 30 mm/hr
. Positive probe-to-bone test
. Leukocytosis > 15,000
. Positive plain radiographs
. C-reactive protein (CRP) > 10 mg/L

Correct Answer & Explanation

. Erythrocyte sedimentation rate (ESR) > 30 mm/hr

Explanation

A positive probe-to-bone test is highly predictive of underlying osteomyelitis in a diabetic foot ulcer. While MRI is the most sensitive imaging modality, the clinical probe-to-bone test remains a critical diagnostic tool.

Question 6984

Topic: Infection, Pharmacology & VTE

A 65-year-old diabetic patient presents with a deep, non-healing plantar midfoot ulcer. Radiographs show a bony prominence causing the ulcer, but MRI is equivocal for osteomyelitis. What is the gold standard for diagnosing osteomyelitis in this setting?

. Tagged white blood cell scan
. C-reactive protein
. Bone biopsy for histopathology and culture
. Three-phase bone scan
. Superficial swab culture of the ulcer

Correct Answer & Explanation

. Tagged white blood cell scan

Explanation

While imaging and clinical signs are helpful, a bone biopsy is the gold standard for definitively diagnosing osteomyelitis. It also provides reliable deep culture data to direct targeted antibiotic therapy in the diabetic foot.

Question 6985

Topic: 1. General Principles & Basic Science

In diabetic patients, measuring tissue oxygenation is critical for determining the healing potential of an ulcer or a planned surgical incision. What is the minimum transcutaneous oxygen tension (TcPO2) generally considered necessary to support wound healing?

. 10 mmHg
. 20 mmHg
. 40 mmHg
. 60 mmHg
. 80 mmHg

Correct Answer & Explanation

. 10 mmHg

Explanation

A TcPO2 greater than 40 mmHg is generally associated with a high probability of wound healing. Values below 30 mmHg indicate severe ischemia and a high likelihood of wound failure, often necessitating vascular intervention or higher-level amputation.

Question 6986

Topic: Infection, Pharmacology & VTE

A 60-year-old poorly controlled diabetic patient has a chronic plantar foot ulcer beneath the first metatarsal head. Which of the following clinical findings has the highest positive predictive value for underlying osteomyelitis?

. Erythema extending > 2 cm from the ulcer margin
. Visible tendon in the base of the ulcer
. A positive probe-to-bone test
. Erythrocyte sedimentation rate > 30 mm/hr
. Presence of purulent drainage

Correct Answer & Explanation

. Erythema extending > 2 cm from the ulcer margin

Explanation

A positive probe-to-bone test (palpating hard, gritty bone with a sterile metal probe) is highly predictive of underlying osteomyelitis in the setting of an infected diabetic foot ulcer. It significantly increases the probability of bone infection.

Question 6987

Topic: 1. General Principles & Basic Science

A diabetic patient is undergoing evaluation for a major lower extremity amputation due to gangrene. Compared to a healthy individual, what is the approximate percentage increase in energy expenditure required for ambulation following a unilateral transtibial (below-knee) amputation?

. 10-15%
. 20-30%
. 40-50%
. 60-70%
. 80-100%

Correct Answer & Explanation

. 10-15%

Explanation

Unilateral transtibial (below-knee) amputees typically require about 25% (range 20-30%) more energy for ambulation compared to baseline. A unilateral transfemoral (above-knee) amputation increases energy expenditure by approximately 65%.

Question 6988

Topic: Infection, Pharmacology & VTE

According to the Wagner classification system for diabetic foot ulcers, a lesion described as a deep ulcer with localized gangrene isolated to the great toe and forefoot is classified as:

. Grade 1
. Grade 2
. Grade 3
. Grade 4
. Grade 5

Correct Answer & Explanation

. Grade 1

Explanation

Wagner Grade 4 indicates localized gangrene (e.g., involving the forefoot, heel, or toes). Grade 3 involves a deep ulcer with osteomyelitis or abscess, while Grade 5 describes extensive gangrene of the entire foot.

Question 6989

Topic: Biomechanics & Biomaterials

A 35-year-old woman is 4 months postoperative from open reduction and internal fixation of an ankle fracture, which included placement of two 3.5mm trans-syndesmotic screws. She is completely asymptomatic and asks if the screws must be removed. Based on current orthopedic literature, what is the recommendation regarding routine removal of syndesmotic screws?

. They must be removed at 3 months to prevent catastrophic hardware failure.
. They must be removed prior to full weight-bearing to restore normal ankle kinematics.
. Routine removal is not required, as retained or broken screws do not significantly worsen clinical outcomes.
. They should be removed only if they were placed rigidly through 4 cortices.
. Removal is mandatory to prevent late-onset distal tibiofibular synostosis.

Correct Answer & Explanation

. They must be removed at 3 months to prevent catastrophic hardware failure.

Explanation

Current evidence demonstrates that routine removal of syndesmotic screws is unnecessary. Clinical outcomes are comparable whether the screws are removed, retained intact, or broken, and elective removal exposes the patient to unnecessary surgical risks.

Question 6990

Topic: Infection, Pharmacology & VTE

Differentiating acute Charcot neuroarthropathy from osteomyelitis in the diabetic foot is challenging. On magnetic resonance imaging (MRI), which of the following findings is most specific for osteomyelitis rather than acute Charcot arthropathy?

. Subchondral bone marrow edema
. Diffuse subcutaneous soft tissue edema
. Presence of a significant joint effusion
. Extensive periarticular debris and fragmentation
. Presence of the "ghost sign" on T1-weighted images

Correct Answer & Explanation

. Subchondral bone marrow edema

Explanation

The "ghost sign" (where bone margins become invisible or indistinct on T1-weighted images but 'reappear' on T2/STIR images) is highly indicative of osteomyelitis. Charcot arthropathy typically demonstrates bone marrow edema strictly localized to the subchondral bone adjacent to affected joints.

Question 6991

Topic: Infection, Pharmacology & VTE

A 60-year-old diabetic male has a chronic plantar ulcer under the first metatarsal head. On examination, a sterile metal probe easily advances through the ulcer base and palpably taps against a hard, gritty surface. What is the approximate positive predictive value of this clinical finding for underlying osteomyelitis?

. 10%
. 30%
. 60%
. 89%
. 100%

Correct Answer & Explanation

. 10%

Explanation

The "probe-to-bone" test has a high positive predictive value (approximately 89%) for diagnosing osteomyelitis in the presence of a clinically infected diabetic foot ulcer. It is a rapid, validated, and highly useful initial clinical evaluation tool.

Question 6992

Topic: Infection, Pharmacology & VTE

A 50-year-old diabetic male has a chronic plantar midfoot ulcer overlying a rocker-bottom deformity. An MRI is ordered to differentiate chronic inactive Charcot osteoarthropathy from osteomyelitis. Which MRI finding is most specific for osteomyelitis rather than Charcot changes alone?

. Subchondral bone marrow edema
. Joint effusion in the tarsometatarsal joints
. Presence of a sinus tract extending to the bone
. Ligamentous disruption
. Thickening of the plantar fascia

Correct Answer & Explanation

. Subchondral bone marrow edema

Explanation

Both osteomyelitis and Charcot arthropathy exhibit bone marrow edema on MRI. However, the presence of a sinus tract, adjacent soft tissue ulceration, or the 'ghost sign' (indistinct bone margins on T1) are highly specific for osteomyelitis.

Question 6993

Topic: Infection, Pharmacology & VTE

Which of the following magnetic resonance imaging (MRI) findings is the most sensitive and specific for distinguishing osteomyelitis from acute Charcot neuroarthropathy in the diabetic foot?

. Diffuse subchondral bone marrow edema on STIR sequences
. Joint subluxation, debris, and fragmentation
. Intramuscular edema in the intrinsic foot muscles
. Replacement of subchondral fat signal with low T1 signal in a focal geographic pattern extending from an ulcer
. High signal intensity in the deep subcutaneous tissues

Correct Answer & Explanation

. Diffuse subchondral bone marrow edema on STIR sequences

Explanation

Replacement of the normal marrow fat signal (low T1) that extends contiguously from a skin ulcer is highly indicative of osteomyelitis. Acute Charcot typically exhibits periarticular subchondral marrow edema but preserves the geographic marrow fat signal away from the joint.

Question 6994

Topic: Infection, Pharmacology & VTE

A 58-year-old diabetic male presents with a deep plantar ulcer extending to the joint capsule, but with no bone involvement, no abscess, and no gangrene. According to the Wagner classification, what grade is this ulcer?

. Grade 0
. Grade 1
. Grade 2
. Grade 3
. Grade 4

Correct Answer & Explanation

. Grade 0

Explanation

Wagner Grade 2 ulcers are deep ulcers penetrating to the tendon, bone, or joint capsule but without deep infection or osteomyelitis. Grade 1 is superficial, and Grade 3 involves deep infection such as osteomyelitis or abscess.

Question 6995

Topic: Infection, Pharmacology & VTE

A 62-year-old diabetic patient with a chronic midfoot ulcer presents with erythema and swelling. Radiographs show bone destruction. Which of the following is the most reliable imaging modality to differentiate acute Charcot neuroarthropathy from osteomyelitis?

. Three-phase bone scan
. Indium-111 labeled WBC scan combined with Technetium-99m marrow scan
. Computed tomography (CT)
. Plain radiographs
. Ultrasound

Correct Answer & Explanation

. Three-phase bone scan

Explanation

Differentiating Charcot arthropathy from osteomyelitis is clinically challenging. A combined Indium-111 WBC scan and Tc-99m marrow scan is highly specific and sensitive for diagnosing osteomyelitis in the setting of Charcot foot.

Question 6996

Topic: Infection, Pharmacology & VTE

A diabetic patient presents with a midfoot ulcer and deep soft tissue swelling. Which of the following MRI findings is most indicative of osteomyelitis rather than acute Charcot neuroarthropathy?

. Diffuse bone marrow edema involving multiple contiguous midfoot bones
. Focal, confluent marrow replacement (low T1 signal) directly contiguous with the skin ulcer
. Extensive subchondral cyst formation around the ankle joint
. Diffuse soft tissue edema that resolves with elevation
. Thickening of the plantar fascia without cortical destruction

Correct Answer & Explanation

. Diffuse bone marrow edema involving multiple contiguous midfoot bones

Explanation

Osteomyelitis typically presents on MRI as focal marrow abnormality (low T1, high T2) that is spatially contiguous with a skin ulcer or sinus tract. Acute Charcot typically exhibits periarticular marrow edema across multiple bones (the "ghost sign") without direct continuity to an ulcer.

Question 6997

Topic: Physiology & Rehabilitation

A 35-year-old male bodybuilder feels a sudden pop in his anterior axilla while performing a heavy bench press. He presents with ecchymosis, swelling, and a loss of the anterior axillary fold. MRI confirms a complete rupture of the pectoralis major tendon. Where does this rupture most commonly occur?

. Musculotendinous junction
. Clavicular head muscle belly
. Sternal head insertion onto the humerus
. Clavicular head insertion onto the humerus
. Origin at the sternum

Correct Answer & Explanation

. Musculotendinous junction

Explanation

Pectoralis major ruptures most frequently occur at the sternal head tendon insertion onto the proximal humerus during maximal eccentric contraction. Surgical repair yields the best functional outcomes for active individuals.

Question 6998

Topic: Surgical Anatomy & Approaches

A 25-year-old male sustains a closed midshaft humerus fracture after a fall. Upon presentation, he has a wrist drop and inability to extend his fingers, but normal sensation in the axillary nerve distribution. Radiographs show acceptable alignment. What is the most appropriate initial management of the nerve injury?

. Immediate surgical exploration of the radial nerve
. Coaptation splinting and clinical observation
. Immediate EMG and nerve conduction studies
. External fixation of the humerus
. Open reduction and internal fixation with nerve grafting

Correct Answer & Explanation

. Immediate surgical exploration of the radial nerve

Explanation

Immediate radial nerve palsy in a closed humeral shaft fracture is typically a neuropraxia with a spontaneous recovery rate of over 70-90%. Initial management consists of functional bracing/splinting and observation for 3-4 months before considering exploration.

Question 6999

Topic: Surgical Anatomy & Approaches

During an open Latarjet procedure, aggressive medial retraction of the conjoint tendon places a specific nerve at risk of traction injury. Which nerve is most vulnerable, and what is its expected distance from the tip of the coracoid?

. Axillary nerve; 1 to 2 cm
. Musculocutaneous nerve; 3 to 8 cm
. Suprascapular nerve; 1 to 2 cm
. Radial nerve; 5 to 7 cm
. Median nerve; 10 to 12 cm

Correct Answer & Explanation

. Axillary nerve; 1 to 2 cm

Explanation

The musculocutaneous nerve penetrates the deep surface of the coracobrachialis approximately 3 to 8 cm distal to the tip of the coracoid. Overzealous medial or distal retraction of the conjoint tendon during a Latarjet procedure can cause a traction neurapraxia to this nerve.

Question 7000

Topic: Surgical Anatomy & Approaches

During an open Latarjet procedure, the surgeon inadvertently places a self-retaining medial retractor deep to the conjoined tendon and applies excessive traction. Which of the following nerves is at greatest risk of injury from this maneuver?

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

Correct Answer & Explanation

. Axillary nerve

Explanation

The musculocutaneous nerve typically enters the coracobrachialis muscle 5 to 8 cm distal to the tip of the coracoid. Retractors placed medially and distally to the conjoined tendon place this nerve at significant risk.

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