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2. Trauma MCQs

Practice Set 497 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 9921

Topic: 2. Trauma
A 6-year-old boy falls off monkey bars and presents with a swollen, deformed forearm. Radiographs reveal a fracture of the proximal third of the ulna with an anterior dislocation of the radial head. According to the Bado classification, what type of Monteggia lesion is this, and what is the presumed mechanism of injury?
. Bado Type I; Forced pronation of the forearm
. Bado Type II; Axial loading with a flexed elbow
. Bado Type III; Varus stress to the elbow
. Bado Type IV; Direct blow to the radius
. Bado Type I; Forced supination of the forearm

Correct Answer & Explanation

. Bado Type I; Forced pronation of the forearm

Explanation

A proximal ulna fracture with an anterior dislocation of the radial head is a Bado Type I Monteggia fracture. It is the most common type, particularly in children. The accepted mechanism of injury is a fall on an outstretched hand with forced pronation of the forearm, causing the radial head to dislocate anteriorly while the ulna fractures and apexes anteriorly.

Question 9922

Topic: 2. Trauma

A 40-year-old construction worker falls 15 feet, sustaining a severe, comminuted, high-energy tibial pilon fracture with massive soft tissue swelling. A staged protocol is chosen. A spanning external fixator is placed on day 1. Which of the following is the most reliable clinical indicator that the soft tissues are ready for definitive open reduction and internal fixation?

. Resolution of all ecchymosis
. Return of the ankle-brachial index to > 1.0
. Appearance of skin wrinkling around the ankle
. Normalization of C-reactive protein (CRP) levels
. A minimum of 21 days since the initial injury

Correct Answer & Explanation

. Appearance of skin wrinkling around the ankle

Explanation

In the staged management of high-energy pilon fractures, definitive ORIF must be delayed until the soft tissue envelope has recovered sufficiently to allow safe surgical incisions and closure without necrosis or wound breakdown. The appearance of skin wrinkles (the 'wrinkle sign') over the anterior ankle and fracture site is the most reliable clinical indicator that the acute edema has subsided enough to proceed safely with ORIF.

Question 9923

Topic: 2. Trauma

A surgeon uses the posteromedial approach to the ankle for fixation of a posterior malleolus fracture. The dissection takes place posterior to the medial malleolus. To safely access the posterior tibia, the surgeon must retract the neurovascular bundle. Which of the following represents the correct order of structures passing behind the medial malleolus, from anterior/medial to posterior/lateral?

. Tibialis posterior, Flexor digitorum longus, Posterior tibial artery, Posterior tibial vein, Tibial nerve, Flexor hallucis longus
. Flexor digitorum longus, Tibialis posterior, Tibial nerve, Posterior tibial artery, Posterior tibial vein, Flexor hallucis longus
. Tibialis posterior, Flexor hallucis longus, Posterior tibial artery, Posterior tibial vein, Tibial nerve, Flexor digitorum longus
. Flexor hallucis longus, Posterior tibial artery, Posterior tibial vein, Tibial nerve, Tibialis posterior, Flexor digitorum longus
. Tibialis posterior, Flexor digitorum longus, Tibial nerve, Posterior tibial artery, Posterior tibial vein, Flexor hallucis longus

Correct Answer & Explanation

. Tibialis posterior, Flexor digitorum longus, Posterior tibial artery, Posterior tibial vein, Tibial nerve, Flexor hallucis longus

Explanation

The correct sequence of structures passing behind the medial malleolus is remembered by the mnemonic 'Tom, Dick, And Very Nervous Harry': Tibialis posterior, flexor Digitorum longus, posterior tibial Artery, posterior tibial Vein, tibial Nerve, and flexor Hallucis longus.

Question 9924

Topic: 2. Trauma

A surgeon is utilizing an extensile posterior approach to the knee to manage a complex popliteal artery injury and posterior tibial plateau fracture. As dissection proceeds through the popliteal fossa, the surgeon must be aware of the relationship of the neurovascular structures. From superficial/lateral to deep/medial, what is the anatomical arrangement in the central popliteal fossa?

. Popliteal Artery, Popliteal Vein, Tibial Nerve
. Popliteal Vein, Tibial Nerve, Popliteal Artery
. Tibial Nerve, Popliteal Vein, Popliteal Artery
. Tibial Nerve, Popliteal Artery, Popliteal Vein
. Popliteal Artery, Tibial Nerve, Popliteal Vein

Correct Answer & Explanation

. Tibial Nerve, Popliteal Vein, Popliteal Artery

Explanation

In the popliteal fossa, the structures are arranged such that the Tibial Nerve is the most superficial and lateral. Deep and slightly medial to the nerve is the Popliteal Vein. The deepest and most medial structure against the joint capsule is the Popliteal Artery. Mnemonic: N-V-A from superficial/lateral to deep/medial.

Question 9925

Topic: Lower Extremity Trauma

During a medial approach to the tibia to access the entire shaft, what is the structure at risk that runs parallel to the medial border of the tibia, particularly in the distal half of the leg?

. Deep peroneal nerve
. Sural nerve
. Great saphenous vein and saphenous nerve
. Posterior tibial artery
. Tibial nerve

Correct Answer & Explanation

. Great saphenous vein and saphenous nerve

Explanation

The saphenous nerve and great saphenous vein run superficially along the medial aspect of the leg, closely following the medial border of the tibia. They are the primary superficial structures at risk during a medial approach to the tibial shaft.

Question 9926

Topic: 2. Trauma

A 45-year-old woman is evaluated for a stiff, painful, and swollen ankle 8 weeks after a cast was removed for a non-operative distal fibula fracture.

What is the most characteristic early radiographic finding in a patient developing Complex Regional Pain Syndrome (CRPS)?

. Subchondral cysts and joint space narrowing
. Diffuse cortical thickening and sclerosis
. Periarticular patchy osteopenia
. Periosteal reaction along the diaphysis
. Heterotopic ossification in the surrounding soft tissues

Correct Answer & Explanation

. Periarticular patchy osteopenia

Explanation

The hallmark early radiographic sign of CRPS (Sudeck's atrophy) is periarticular patchy or mottled osteopenia. This is believed to result from localized bone resorption mediated by altered sympathetic nervous system activity and regional inflammation.

Question 9927

Topic: 2. Trauma

Following successful enucleation of a 3 cm benign schwannoma from the posterior interosseous nerve, the patient exhibits a new-onset wrist and finger drop. The surgeon is certain no fascicles were sharply transected. What is the most likely etiology and expected outcome of this deficit?

. Axonotmesis requiring immediate nerve grafting
. Neurotmesis with permanent deficit
. Neuropraxia due to traction, likely to recover spontaneously
. Compartment syndrome requiring immediate fasciotomy
. Ischemic neuropathy secondary to epineurial vessel ligation

Correct Answer & Explanation

. Neuropraxia due to traction, likely to recover spontaneously

Explanation

Transient neurologic deficits (neuropraxia) are common after schwannoma enucleation due to traction and manipulation of the adjacent nerve fascicles. If the fascicles were anatomically preserved, spontaneous recovery over weeks to months is the expected outcome.

Question 9928

Topic: 2. Trauma

In the management of a severely injured polytrauma patient, Damage Control Orthopedics (DCO) is indicated over Early Total Care (ETC) when the patient is physiologically unstable. Which of the following parameters is an accepted criterion for initiating DCO?

. Serum Lactate < 2.0 mmol/L
. Core body temperature < 34 degrees Celsius
. Platelet count > 150,000 / microL
. Base excess +2 mEq/L
. Injury Severity Score (ISS) of 15

Correct Answer & Explanation

. Core body temperature < 34 degrees Celsius

Explanation

Damage Control Orthopedics (DCO) is indicated in the 'in extremis' or unstable polytrauma patient. The lethal triad of trauma includes hypothermia, coagulopathy, and acidosis. Clinical parameters favoring DCO include core temperature < 34°C, pH < 7.24, base excess < -5 mEq/L, serum lactate > 2.5 mmol/L, coagulopathy (platelets < 90,000 or elevated INR), and need for massive transfusion. An ISS > 40 is also considered unstable.

Question 9929

Topic: 2. Trauma

A randomized controlled trial introduces a novel prophylactic antibiotic protocol that decreases the rate of deep surgical site infections (SSI) in open tibia fractures from 8% to 4%. What is the Number Needed to Treat (NNT) to prevent one deep SSI using this new protocol?

. 4
. 8
. 12
. 25
. 50

Correct Answer & Explanation

. 25

Explanation

The Number Needed to Treat (NNT) is calculated as 1 / Absolute Risk Reduction (ARR). The ARR is the difference in event rates between the control group and the experimental group. ARR = 8% - 4% = 4% (or 0.04). Therefore, NNT = 1 / 0.04 = 25. This means 25 patients need to be treated with the new protocol to prevent one additional SSI.

Question 9930

Topic: 2. Trauma

Acute compartment syndrome is a surgical emergency. The primary pathophysiological event that initiates the cascade leading to tissue ischemia and necrosis in compartment syndrome is:

. Arterial occlusion leading to profound primary muscle ischemia
. Increased intracompartmental pressure exceeding venous outflow pressure, causing venous collapse
. Lymphatic channel blockage leading to rapid interstitial fluid accumulation
. Direct toxic effect of myoglobin on local capillary endothelial cells
. Spasm of the main arterial trunk supplying the compartment

Correct Answer & Explanation

. Increased intracompartmental pressure exceeding venous outflow pressure, causing venous collapse

Explanation

The cascade of acute compartment syndrome begins when local tissue pressure within a closed fascial space increases. This rising pressure first exceeds venous outflow pressure, causing thin-walled venules to collapse. This obstructs venous return, further increasing local hydrostatic pressure and interstitial edema, which eventually collapses the arteriolar capillary beds, obliterating the arterio-venous gradient and causing severe tissue ischemia.

Question 9931

Topic: Lower Extremity Trauma

When comparing a solid titanium intramedullary nail to a hollow titanium intramedullary nail of the exact same outer diameter, how does the bending stiffness (flexural rigidity) of the hollow nail compare to the solid nail?

. The hollow nail has significantly greater bending stiffness
. The hollow nail has exactly the same bending stiffness
. The hollow nail has slightly less bending stiffness
. The hollow nail has exactly half the bending stiffness
. The hollow nail has significantly less bending stiffness, proportional to the inner radius cubed

Correct Answer & Explanation

. The hollow nail has slightly less bending stiffness

Explanation

Bending stiffness is proportional to the area moment of inertia (I), which correlates to the radius to the fourth power (r^4) for a solid cylinder. For a hollow cylinder, I is proportional to (Outer Radius^4 - Inner Radius^4). Because the r^4 term is heavily influenced by the outermost material, removing the inner core (small inner radius) reduces the overall bending stiffness only slightly.

Question 9932

Topic: 2. Trauma

A multicenter study investigates a new implant for distal femur fractures. The investigators randomly assign patients to either the new implant or the standard of care but fail to blind the surgeons to the allocation. Which type of bias is most likely introduced into the evaluation of intraoperative and immediate postoperative outcomes?

. Recall bias
. Performance bias
. Attrition bias
. Selection bias
. Reporting bias

Correct Answer & Explanation

. Performance bias

Explanation

Performance bias occurs when knowledge of the intervention allocation affects how care is provided. If surgeons are not blinded (which is inherently difficult in surgical trials), their belief in the new implant may lead them to perform the procedure more meticulously or alter co-interventions, thereby systematically distorting the outcomes.

Question 9933

Topic: 2. Trauma

According to Perren's strain theory of bone healing, what is the maximum tissue strain under which secondary bone healing (endochondral ossification) can occur within a fracture gap?

. Less than 2%
. Between 2% and 10%
. Between 10% and 30%
. Between 30% and 50%
. Greater than 100%

Correct Answer & Explanation

. Between 2% and 10%

Explanation

Perren's strain theory posits that different tissues tolerate different levels of mechanical strain. Granulation tissue tolerates up to 100% strain, cartilage tolerates up to 10%, and bone tolerates up to 2%. Therefore, endochondral ossification requires strain to be reduced below 10%.

Question 9934

Topic: Lower Extremity Trauma

During a fluoroscopically guided intramedullary nailing, the surgeon wishes to minimize radiation exposure. Which of the following modifications is most effective in reducing the scatter radiation received by the operating room personnel?

. Decreasing the distance between the X-ray tube and the patient
. Positioning the X-ray tube over the patient and the image intensifier under the table
. Using continuous rather than pulsed fluoroscopy
. Positioning the image intensifier as close to the patient as possible
. Removing the collimator

Correct Answer & Explanation

. Positioning the image intensifier as close to the patient as possible

Explanation

Placing the image intensifier as close to the patient as possible decreases radiation scatter and improves image resolution. The X-ray tube should also be positioned under the operating table to direct backscatter toward the floor rather than the surgeon's torso.

Question 9935

Topic: 2. Trauma
A 35-year-old male sustains a high-energy open tibia fracture after a motorcycle collision. The wound is 12 cm long with extensive soft tissue stripping, periosteal damage, and visible bone contamination with soil, but coverage is possible without a free flap. Based on current evidence-based guidelines for preventing infection in this specific injury pattern, which of the following initial intravenous antibiotic regimens is most appropriate?
. Cefazolin monotherapy for 24 hours
. Ceftriaxone and Vancomycin for 72 hours
. Cefazolin and Gentamicin, with Penicillin for 72 hours
. Ceftriaxone monotherapy for 48 hours
. Cefazolin and Ciprofloxacin for 24 hours

Correct Answer & Explanation

. Cefazolin and Gentamicin, with Penicillin for 72 hours

Explanation

This is a Gustilo-Anderson Type IIIA open fracture (high energy, >10 cm, adequate soft tissue coverage). Standard prophylaxis for Type III open fractures historically includes a first-generation cephalosporin (Cefazolin) and an aminoglycoside (Gentamicin). If organic material (soil/farm injury) is present, adding Penicillin is recommended to cover Clostridium species. Current guidelines typically recommend 72 hours of coverage or 24 hours post-soft tissue coverage.

Question 9936

Topic: 2. Trauma
A 28-year-old male presents to the emergency department with severe leg pain out of proportion to his injury following a tibial shaft fracture. Clinical examination raises suspicion for acute compartment syndrome. The decision to proceed with emergent fasciotomy is most definitively supported by which of the following physiological criteria?
. Absolute compartment pressure greater than 20 mmHg
. Absolute compartment pressure greater than 25 mmHg
. Delta P (Diastolic Blood Pressure minus Compartment Pressure) less than 30 mmHg
. Delta P (Mean Arterial Pressure minus Compartment Pressure) less than 40 mmHg
. Delta P (Systolic Blood Pressure minus Compartment Pressure) less than 50 mmHg

Correct Answer & Explanation

. Delta P (Diastolic Blood Pressure minus Compartment Pressure) less than 30 mmHg

Explanation

The Delta P (ΔP) is the most reliable threshold for diagnosing acute compartment syndrome. A Delta P (Diastolic Blood Pressure minus the Absolute Compartment Pressure) of less than 30 mmHg is considered an indication for emergent fasciotomy. Relying on absolute pressure alone can lead to unnecessary fasciotomies, especially in hypertensive patients.

Question 9937

Topic: 2. Trauma

A 45-year-old male presents with a persistent midshaft clavicle fracture 8 months post-injury. Radiographs reveal a 'horse-shoe' or 'elephant foot' appearance at the fracture site with abundant callus formation but no bridging bone. What is the fundamental biological reason for this specific type of nonunion?

. Inadequate biological healing potential (avascularity)
. Infection at the fracture site
. Interposition of soft tissue
. Inadequate mechanical stability
. Metabolic bone disease

Correct Answer & Explanation

. Inadequate mechanical stability

Explanation

An 'elephant foot' or 'horse-shoe' nonunion is a hypertrophic nonunion. The presence of abundant callus indicates that the biological healing potential (blood supply and cellular activity) is adequate. The failure to progress to solid union is fundamentally due to excessive mechanical instability (inadequate immobilization), which prevents the calcification of the fibrocartilaginous callus into woven bone.

Question 9938

Topic: Pelvic & Acetabular Trauma

A 32-year-old female is involved in a high-speed MVC. An AP Pelvis radiograph demonstrates symphyseal diastasis of 3.5 cm.

Further imaging confirms the posterior sacroiliac (SI) ligaments are intact. According to the Young-Burgess classification, which of the following ligamentous complexes is MOST likely disrupted in this APC-II injury?

. Posterior sacroiliac ligament only
. Sacrotuberous, sacrospinous, and anterior sacroiliac ligaments
. Iliolumbar ligaments bilaterally
. Sacrotuberous ligament only
. Anterior longitudinal ligament

Correct Answer & Explanation

. Sacrotuberous, sacrospinous, and anterior sacroiliac ligaments

Explanation

An Anteroposterior Compression Type II (APC-II) injury involves disruption of the pubic symphysis (>2.5 cm) along with rupture of the sacrotuberous, sacrospinous, and anterior sacroiliac ligaments. The posterior sacroiliac ligaments remain intact, providing vertical stability but resulting in rotational instability (an 'open book' pelvis).

Question 9939

Topic: 2. Trauma
A 25-year-old male sustains a high-energy Pauwels type III (vertical) femoral neck fracture. When selecting an internal fixation construct, the surgeon must account for the primary biomechanical force driving failure and varus collapse in this specific fracture pattern. Which of the following forces is most prominent in this scenario?
. Compressive force across the fracture site
. Tensile force on the inferior neck
. Shear force
. Torsional force
. Bending force strictly in the sagittal plane

Correct Answer & Explanation

. Shear force

Explanation

The Pauwels classification is based on the angle of the femoral neck fracture relative to the horizontal plane. A Pauwels type III fracture is steeply oriented (greater than 50 degrees). Because of this vertical orientation, weight-bearing generates extremely high shear forces across the fracture site, predisposing to varus collapse, nonunion, and fixation failure.

Question 9940

Topic: 2. Trauma

A 28-year-old male sustains a closed comminuted tibia fracture. Four hours post-admission, he develops severe pain out of proportion to the injury.

Intracompartmental pressure testing is performed. The diagnosis of acute compartment syndrome is most definitively supported by which of the following hemodynamic criteria?

. Absolute compartment pressure strictly greater than 20 mmHg
. Absolute compartment pressure strictly greater than 25 mmHg
. Diastolic blood pressure minus compartment pressure less than 30 mmHg
. Mean arterial pressure minus compartment pressure less than 40 mmHg
. Systolic blood pressure minus compartment pressure less than 30 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure less than 30 mmHg

Explanation

The widely accepted threshold for diagnosing acute compartment syndrome and indicating fasciotomy is a 'delta P' of less than 30 mmHg. Delta P is calculated as the patient's diastolic blood pressure minus the intracompartmental pressure. Relying on an absolute pressure threshold (e.g., >30 mmHg) can lead to unnecessary fasciotomies in hypertensive patients or missed diagnoses in hypotensive patients.

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