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2. Trauma MCQs

Practice Set 617 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 12321

Topic: 2. Trauma

Following a closed humerus shaft fracture, a patient develops a complete radial nerve palsy. Electromyography (EMG) at 4 weeks shows fibrillation potentials in the brachioradialis. According to Seddon's classification, the nerve injury is determined to be an axonotmesis. Which of the following characterizes this specific type of nerve injury?

. Focal conduction block without Wallerian degeneration
. Complete transection of the nerve including the epineurium
. Disruption of the axon and myelin sheath with preservation of the surrounding connective tissue frameworks
. Demyelination with intact axons
. Spontaneous recovery typically occurs within 2 to 3 days

Correct Answer & Explanation

. Disruption of the axon and myelin sheath with preservation of the surrounding connective tissue frameworks

Explanation

In Seddon's classification, Neuropraxia is a focal conduction block (myelin injury) without axonal disruption (recovers quickly). Axonotmesis involves disruption of the axon and myelin sheath, leading to Wallerian degeneration distally, but the connective tissue tubes (endoneurium, perineurium, epineurium) remain partially or fully intact, allowing for targeted axonal regeneration. Neurotmesis is complete nerve transection.

Question 12322

Topic: 2. Trauma

Which of the following Recombinant Human Bone Morphogenetic Proteins (rhBMPs) has been specifically FDA-approved for use in acute, open tibial shaft fractures stabilized with an intramedullary nail?

. rhBMP-2
. rhBMP-3
. rhBMP-4
. rhBMP-6
. rhBMP-7

Correct Answer & Explanation

. rhBMP-2

Explanation

Recombinant human BMP-2 (rhBMP-2) is FDA-approved for use in acute, open tibial shaft fractures stabilized with an intramedullary nail, as well as for single-level anterior lumbar interbody fusion (ALIF). rhBMP-7 (also known as Osteogenic Protein-1 or OP-1) was previously available under a Humanitarian Device Exemption for recalcitrant tibial nonunions but is not the approved BMP for acute open tibias. BMP-3 is notable for being an inhibitor of osteogenesis.

Question 12323

Topic: 2. Trauma

A 22-year-old man sustains bilateral closed femur fractures in a motor vehicle accident. Forty-eight hours later, he develops confusion, tachypnea, and a petechial rash over his axilla and conjunctiva. Which of the following is the most appropriate initial management?

. Intravenous administration of high-dose corticosteroids
. Immediate systemic heparinization
. Supportive care with optimization of oxygenation and hemodynamics
. Urgent placement of an inferior vena cava filter
. Administration of broad-spectrum antibiotics

Correct Answer & Explanation

. Supportive care with optimization of oxygenation and hemodynamics

Explanation

The patient is presenting with classic Bergman's triad (hypoxia, neurologic compromise, petechial rash), indicative of Fat Embolism Syndrome (FES). The mainstay of treatment for FES is supportive care, primarily focusing on respiratory support (oxygenation/ventilation) and hemodynamic maintenance. Corticosteroids have not been shown to be effective in established FES, and systemic heparinization is contraindicated.

Question 12324

Topic: 2. Trauma
A 45-year-old farmer sustains a Gustilo-Anderson Type IIIA open tibia fracture heavily contaminated with soil and manure. According to current evidence-based trauma guidelines, which of the following antibiotic regimens is most appropriate?
. First-generation cephalosporin alone
. First-generation cephalosporin and an aminoglycoside
. First-generation cephalosporin, an aminoglycoside, and high-dose penicillin
. Fluoroquinolone monotherapy
. Vancomycin and Piperacillin-Tazobactam

Correct Answer & Explanation

. First-generation cephalosporin, an aminoglycoside, and high-dose penicillin

Explanation

For severe open fractures with farm or soil contamination (Type III), high-dose penicillin is added to the standard regimen of a first-generation cephalosporin and an aminoglycoside. This specific addition provides coverage against Clostridium species to prevent gas gangrene.

Question 12325

Topic: 2. Trauma

During internal fixation of a dense cortical bone fracture, the pullout strength of the orthopedic screw is determined by several design parameters. Which of the following geometric modifications most significantly increases the screw's pullout strength?

. Increasing the inner (root) diameter
. Increasing the outer (thread) diameter
. Increasing the pitch length
. Increasing the head diameter
. Decreasing the thread run-out length

Correct Answer & Explanation

. Increasing the outer (thread) diameter

Explanation

Pullout strength of a bone screw is directly proportional to the outer (thread) diameter, the length of thread engagement, and the shear strength of the bone. Increasing the outer diameter maximizes the volume of bone captured between threads.

Question 12326

Topic: 2. Trauma

A 32-year-old male sustains a closed midshaft tibia fracture and subsequently complains of severe pain requiring increasing doses of narcotics. Which of the following clinical findings is considered the earliest and most reliable indicator of acute compartment syndrome?

. Loss of palpable dorsalis pedis and posterior tibial pulses
. Pallor and poikilothermia of the distal extremity
. Severe pain with passive stretch of the involved compartment's muscles
. Paresthesias in the first web space of the toes
. Motor paralysis of the extensor hallucis longus

Correct Answer & Explanation

. Severe pain with passive stretch of the involved compartment's muscles

Explanation

Pain out of proportion to the injury and pain with passive stretching of the muscles within the affected compartment are the earliest and most sensitive clinical signs of acute compartment syndrome. Pulselessness and paralysis are late, ominous signs of irreversible damage.

Question 12327

Topic: 2. Trauma

A patient sustains a closed midshaft humerus fracture and presents with a wrist drop. Electromyography at 4 weeks shows fibrillation potentials in the brachioradialis. Surgical exploration demonstrates that the epineurium, perineurium, and endoneurium remain intact. Which of the following best classifies this nerve injury?

. Neuropraxia
. Axonotmesis
. Neurotmesis
. Sunderland Grade IV
. Sunderland Grade V

Correct Answer & Explanation

. Axonotmesis

Explanation

This injury describes an Axonotmesis (Seddon classification) or Sunderland Grade II injury. The axons are disrupted (leading to Wallerian degeneration and fibrillation potentials on EMG), but the supporting connective tissue frameworks (endoneurium, perineurium, epineurium) are preserved. Neuropraxia does not cause Wallerian degeneration, so fibrillations would be absent. Neurotmesis implies complete transection.

Question 12328

Topic: 2. Trauma

A surgeon is utilizing a bridge plating technique for a highly comminuted midshaft femur fracture. To purposefully decrease the stiffness of the construct and promote secondary bone healing via callus formation, which of the following technical modifications is most appropriate?

. Decrease the working length of the plate
. Increase the working length of the plate
. Use a substantially thicker titanium plate
. Place locked screws in every hole adjacent to the fracture
. Add a lag screw across the fracture site

Correct Answer & Explanation

. Increase the working length of the plate

Explanation

The 'working length' of a plate is the distance between the two closest screws on either side of the fracture. Increasing the working length (leaving more empty holes over the fracture) decreases the stiffness of the construct. This allows for increased, controlled interfragmentary strain, which stimulates secondary bone healing and callus formation. Decreasing the working length or using stiffer materials would create a more rigid construct.

Question 12329

Topic: 2. Trauma
A 35-year-old male presents to the trauma bay after a motorcycle accident with an anteroposterior compression (APC) type III pelvic ring injury. What is the most common primary source of life-threatening hemorrhage in this specific injury pattern?
. Superior gluteal artery
. Presacral venous plexus and bleeding cancellous bone
. Internal pudendal artery
. Obturator artery
. External iliac artery

Correct Answer & Explanation

. Presacral venous plexus and bleeding cancellous bone

Explanation

While arterial bleeding (such as from the internal pudendal artery in APC injuries) can cause rapid hemodynamic decompensation, up to 80-90% of bleeding in pelvic ring disruptions originates from the presacral venous plexus and the exposed cancellous bone surfaces of the fractures.

Question 12330

Topic: 2. Trauma

Which of the following osteoinductive agents is currently FDA approved as an adjunct for the treatment of acute, open tibial shaft fractures stabilized with an intramedullary nail?

. rhBMP-2
. rhBMP-3
. rhBMP-4
. rhBMP-7
. rhBMP-9

Correct Answer & Explanation

. rhBMP-2

Explanation

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is FDA approved for use in acute, open tibial shaft fractures treated with an IM nail, as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 (OP-1) was previously used under a humanitarian exemption for recalcitrant nonunions.

Question 12331

Topic: 2. Trauma
According to the Pauwels classification for femoral neck fractures, which of the following best describes the biomechanical forces primarily acting on a Pauwels type III fracture?
. Low angle (< 30 degrees) resulting in high compressive forces
. Moderate angle (30-50 degrees) resulting in balanced forces
. High angle (> 50 degrees) resulting in high shear forces
. Basicervical location resulting in high bending forces
. Intertrochanteric extension resulting in high tensile forces

Correct Answer & Explanation

. High angle (> 50 degrees) resulting in high shear forces

Explanation

The Pauwels classification describes the angle of the femoral neck fracture line relative to the horizontal. A Pauwels type III fracture has a vertical orientation (>50 degrees), which converts physiologic loads into high shear forces across the fracture site, significantly increasing the risk of nonunion and varus collapse.

Question 12332

Topic: 2. Trauma
A 35-year-old agricultural worker sustains an open tibial shaft fracture after his leg is caught in a tractor mechanism. The wound measures 12 cm long with extensive crush injury to the muscle, but there is adequate periosteal coverage of the bone and normal distal pulses. According to evidence-based guidelines for open fractures, what is the optimal initial intravenous antibiotic regimen?
. First-generation cephalosporin monotherapy
. First-generation cephalosporin and an aminoglycoside
. First-generation cephalosporin, an aminoglycoside, and high-dose penicillin
. Fluoroquinolone monotherapy
. Third-generation cephalosporin monotherapy

Correct Answer & Explanation

. First-generation cephalosporin, an aminoglycoside, and high-dose penicillin

Explanation

This injury is classified as a Gustilo-Anderson Type IIIA open fracture (high energy, wound >10 cm, farm injury, but adequate soft tissue coverage). Farm injuries, heavily contaminated soil wounds, or those with suspected bowel contamination carry a significantly high risk of severe anaerobic infection (e.g., Clostridium perfringens). The standard antibiotic protocol for Type III open fractures includes a first-generation cephalosporin (Gram-positives) and an aminoglycoside (Gram-negatives), with the critical addition of high-dose penicillin to specifically cover anaerobes.

Question 12333

Topic: Pelvic & Acetabular Trauma
In the acute trauma bay management of a hemodynamically unstable patient with an 'open book' pelvic ring injury (APC-III), a pelvic binder is ordered. For optimal biomechanical reduction of the pelvic volume, the center of the binder must be positioned directly over which specific anatomic landmarks?
. The highest aspect of the iliac crests
. The anterior superior iliac spines (ASIS)
. The greater trochanters of the femurs
. The pubic symphysis anteriorly and L5 spinous process posteriorly
. The umbilicus and mid-lumbar spine

Correct Answer & Explanation

. The greater trochanters of the femurs

Explanation

To achieve optimal closure of an open book pelvic fracture (which reduces pelvic volume and helps tamponade venous and cancellous bone hemorrhage), the compressive force must be applied appropriately through the hip joints. A pelvic binder or tightly wrapped sheet should be centered directly over the greater trochanters. Placing the binder too high (over the iliac crests or abdomen) is biomechanically ineffective and can paradoxically worsen the deformity by pushing the iliac wings inward while the pubic symphysis remains splayed open.

Question 12334

Topic: 2. Trauma

During closed reduction and intramedullary nailing of a tibial shaft fracture, the surgeon decides to ream the canal to insert a larger diameter solid titanium nail. If the radius of the solid nail is increased by a factor of 2, by what factor does the nail's bending rigidity increase?

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 16

Explanation

The bending rigidity of a solid cylinder is proportional to its area moment of inertia, which is proportional to the radius to the fourth power (r^4). Therefore, doubling the radius increases the bending rigidity by a factor of 16.

Question 12335

Topic: 2. Trauma

An external fixator is applied to stabilize a highly comminuted tibial plateau fracture. Which of the following modifications to the fixator construct will most effectively increase its overall stiffness?

. Decreasing the pin diameter
. Increasing the distance between the bone and the rod
. Increasing the distance between the pins within each fragment
. Placing the pins further away from the fracture site
. Using titanium rods instead of carbon fiber rods

Correct Answer & Explanation

. Increasing the distance between the pins within each fragment

Explanation

Increasing the spread (distance) between the pins within a single bone fragment significantly increases the stability and stiffness of the external fixator construct. Decreasing bone-to-rod distance and increasing pin diameter also increase stiffness.

Question 12336

Topic: 2. Trauma

A surgeon is plating a comminuted midshaft femur fracture using a bridge plating technique with a locking compression plate. Leaving empty screw holes directly over the fracture site primarily serves to do which of the following?

. Increase the construct rigidity
. Decrease the working length
. Increase the working length and decrease strain at the fracture site
. Decrease the bending stiffness of the plate itself
. Increase the risk of plate fatigue failure

Correct Answer & Explanation

. Increase the working length and decrease strain at the fracture site

Explanation

Leaving empty screw holes over the fracture site increases the working length of the plate construct. This decreases the overall strain at the fracture site, promoting secondary bone healing via callus formation while reducing the risk of implant failure.

Question 12337

Topic: 2. Trauma

A 24-year-old male is admitted with a severe closed tibia fracture. The surgical team is concerned about acute compartment syndrome. The patient is hypotensive with a blood pressure of 80/45 mmHg (Mean Arterial Pressure = 57 mmHg). Intracompartmental pressure testing reveals a pressure of 28 mmHg in the anterior compartment. What is the most appropriate next step in management?

. Immediate four-compartment fasciotomy
. Elevate the leg above the level of the heart and reassess in 2 hours
. Continuous clinical monitoring, as the absolute pressure is below 30 mmHg
. Apply a short leg cast to provide absolute stability and reduce swelling
. Administer intravenous mannitol and observe

Correct Answer & Explanation

. Immediate four-compartment fasciotomy

Explanation

The decision to perform a fasciotomy should be based on the 'delta pressure' (Delta P), which is calculated as the Diastolic Blood Pressure minus the Compartment Pressure. A Delta P of less than or equal to 30 mmHg is highly suggestive of compartment syndrome and is an absolute indication for fasciotomy. In this patient, Delta P = 45 - 28 = 17 mmHg. The absolute compartment pressure of 28 is less significant than the critical narrowing of the perfusion gradient.

Question 12338

Topic: Pelvic & Acetabular Trauma
According to the Young-Burgess classification of pelvic ring injuries, an anteroposterior compression type II (APC II) injury is defined by pubic symphysis diastasis and the specific disruption of which of the following posterior pelvic ligamentous structures?
. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments
. Posterior sacroiliac ligaments only
. Iliolumbar ligaments
. Both anterior and posterior sacroiliac ligaments
. Sacrospinous ligaments exclusively

Correct Answer & Explanation

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments

Explanation

An APC II injury involves an external rotation force that opens the anterior pelvic ring (symphysis diastasis). In the posterior ring, it specifically tears the anterior sacroiliac ligament, the sacrotuberous ligament, and the sacrospinous ligament. The robust posterior sacroiliac ligaments remain completely intact, acting as a hinge. This creates rotational instability but preserves vertical stability. Disruption of both anterior and posterior SI ligaments would constitute an APC III injury.

Question 12339

Topic: 2. Trauma

A 24-year-old polytrauma patient with a bilateral femur fractures arrives in the emergency department. The team debates Early Total Care (ETC) versus Damage Control Orthopedics (DCO) with external fixation. Which of the following physiological parameters strongly indicates that DCO is the safest approach?

. Lactate < 2.0 mmol/L
. Platelet count > 150,000
. Body temperature > 36°C
. Base excess < -8 mmol/L
. Urine output > 1 ml/kg/hr

Correct Answer & Explanation

. Base excess < -8 mmol/L

Explanation

Indications for Damage Control Orthopedics (DCO) include parameters that indicate a patient is 'in extremis' or borderline. These include: Base excess worse than -8 mmol/L, pH < 7.24, Temperature < 35°C, Lactate > 2.5 mmol/L, or significant coagulopathy. A base excess < -8 reflects severe metabolic acidosis and hypoperfusion.

Question 12340

Topic: 2. Trauma

Primary bone healing occurs without callus formation and requires absolute stability. Which of the following fracture fixation constructs is designed to promote primary bone healing?

. Intramedullary nailing of a comminuted midshaft femur fracture
. Bridge plating of a multi-fragmentary tibia shaft fracture
. Compression plating of a transverse midshaft radius fracture
. External fixation of a highly comminuted pilon fracture
. Cast immobilization of a non-displaced scaphoid waist fracture

Correct Answer & Explanation

. Compression plating of a transverse midshaft radius fracture

Explanation

Primary bone healing requires absolute stability (strain <2%) and direct contact between fracture ends, allowing for osteonal cutting cones to cross the fracture site. Compression plating of a transverse fracture provides this environment. Intramedullary nails, bridge plates, external fixators, and casts typically allow micro-motion, resulting in secondary bone healing via endochondral ossification (callus formation).

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