Menu

2. Trauma MCQs

Practice Set 608 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 12141

Topic: 2. Trauma

A surgeon decides to increase the diameter of a solid titanium intramedullary nail from 10 mm to 12 mm for a subtrochanteric fracture. By approximately what factor does the torsional rigidity of the new nail increase compared to the original?

. 1.2
. 1.44
. 1.73
. 2.07
. 3.14

Correct Answer & Explanation

. 2.07

Explanation

The torsional rigidity of a solid cylindrical implant is proportional to the fourth power of its radius. Increasing the diameter by a factor of 1.2 (12 mm / 10 mm) increases rigidity by 1.2^4, which is approximately 2.07.

Question 12142

Topic: 2. Trauma

A 45-year-old male develops a nonunion 8 months after intramedullary nailing of a tibial shaft fracture. Radiographs show minimal callus formation but bone scan reveals active uptake. Which of the following best classifies this nonunion?

. Atrophic nonunion
. Hypertrophic nonunion
. Infected nonunion
. Pseudarthrosis
. Oligotrophic nonunion

Correct Answer & Explanation

. Oligotrophic nonunion

Explanation

Oligotrophic nonunions present with minimal to no callus on radiographs but maintain adequate biologic potential and vascularity (demonstrated by uptake on bone scan). They are typically caused by imperfect reduction or insufficient stability.

Question 12143

Topic: 2. Trauma

When evaluating the biomechanical properties of a solid intramedullary nail used for fracture fixation, doubling the radius of the nail will increase its bending stiffness by what factor?

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 16

Explanation

The bending stiffness of a solid cylinder is proportional to its area moment of inertia, which relies on the radius raised to the fourth power (r^4). Therefore, doubling the radius increases the bending stiffness 16-fold.

Question 12144

Topic: 2. Trauma

When applying a dynamic compression plate (DCP) to a transverse radius fracture, the screws are placed eccentrically in the oblong plate holes. As the screws are tightened into the bone, what primary biomechanical effect is generated at the fracture site?

. Distraction
. Axial compression
. Shear strain
. Torsional instability
. Stress shielding

Correct Answer & Explanation

. Axial compression

Explanation

Eccentric screw placement utilizes the spherical geometry of the screw head against the sloped track of the plate hole. Tightening causes the plate to slide, translating the bone fragment and generating interfragmentary axial compression.

Question 12145

Topic: 2. Trauma

In diagnosing acute compartment syndrome in an unresponsive polytrauma patient, which of the following pressure measurements provides the most reliable threshold for indicating a surgical fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 25 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Mean arterial pressure minus compartment pressure < 45 mmHg
. Systolic blood pressure minus compartment pressure < 30 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The delta pressure (diastolic blood pressure minus compartment pressure) is the most reliable clinical indicator for acute compartment syndrome. A delta pressure of less than 30 mmHg indicates inadequate tissue perfusion and is an absolute indication for fasciotomy.

Question 12146

Topic: 2. Trauma

Gurd's major diagnostic criteria for fat embolism syndrome (FES) include respiratory insufficiency, cerebral involvement, and which of the following physical examination findings?

. Tachycardia out of proportion to pain
. High-grade pyrexia
. Petechial rash
. Scleral icterus
. Retinal hemorrhages

Correct Answer & Explanation

. Petechial rash

Explanation

Gurd's diagnostic criteria for fat embolism syndrome include three major criteria: respiratory insufficiency, cerebral involvement (altered mental status), and a petechial rash. The rash typically appears on the axillae, conjunctivae, and upper body within 24 to 48 hours.

Question 12147

Topic: 2. Trauma

In the application of a bridge plate for a comminuted diaphyseal tibia fracture, increasing the 'working length' of the plate (the distance between the innermost screws on either side of the fracture) primarily results in which of the following biomechanical alterations?

. Increased axial stiffness
. Decreased axial stiffness
. Decreased construct flexibility
. Decreased interfragmentary strain
. Increased resistance to fatigue failure

Correct Answer & Explanation

. Decreased axial stiffness

Explanation

The working length of a plate is the segment between the innermost screws on opposite sides of the fracture. Increasing the working length decreases the overall axial and torsional stiffness of the construct. This increased flexibility permits more interfragmentary motion (increased strain), which promotes secondary bone healing through callus formation.

Question 12148

Topic: 2. Trauma

A 38-year-old male sustains a Schatzker IV tibial plateau fracture. Which of the following complications is most specifically associated with this fracture pattern compared to lateral-sided plateau fractures?

. Common peroneal nerve palsy
. Popliteal artery injury
. Lateral collateral ligament tear
. Anterior cruciate ligament avulsion
. Meniscocapsular separation of the lateral meniscus

Correct Answer & Explanation

. Popliteal artery injury

Explanation

A Schatzker IV fracture involves the medial tibial plateau. It is typically a high-energy injury (or low-energy in osteoporotic bone) and is highly associated with knee dislocation or subluxation equivalents. The medial plateau displaces and the popliteal artery is at significant risk of traction or transection injury due to its fixed position at the popliteal trifurcation under the soleus arch.

Question 12149

Topic: Pelvic & Acetabular Trauma

In an APC-II (Anteroposterior Compression Type II) pelvic ring injury, the symphysis pubis is diastatic and there is opening of the anterior sacroiliac joints. Which of the following ligamentous structures remains intact, preventing vertical instability?

. Sacrotuberous ligament
. Sacrospinous ligament
. Anterior sacroiliac ligament
. Posterior sacroiliac ligament
. Iliolumbar ligament

Correct Answer & Explanation

. Sacrospinous ligament

Explanation

An APC-II injury (open book pelvis) involves disruption of the symphysis pubis, the sacrotuberous and sacrospinous ligaments, and the anterior sacroiliac ligaments. The strong posterior sacroiliac ligaments remain intact, acting as a hinge. This allows the pelvis to open anteriorly (rotational instability) but prevents vertical displacement (vertical stability).

Question 12150

Topic: 2. Trauma

A 28-year-old male sustains a closed tibia fracture and presents with severe leg pain out of proportion to the injury. Which of the following absolute compartment pressure measurements is the most widely accepted threshold indicating the need for emergent fasciotomy, considering the delta pressure concept?

. Absolute compartment pressure > 15 mmHg
. Absolute compartment pressure > 25 mmHg
. Delta pressure (Diastolic BP - Compartment Pressure) < 30 mmHg
. Delta pressure (Systolic BP - Compartment Pressure) < 40 mmHg
. Delta pressure (Mean Arterial Pressure - Compartment Pressure) < 10 mmHg

Correct Answer & Explanation

. Delta pressure (Diastolic BP - Compartment Pressure) < 30 mmHg

Explanation

The delta pressure is the most reliable indicator for diagnosing acute compartment syndrome. It is calculated as Diastolic Blood Pressure minus Compartment Pressure. A delta pressure of less than 30 mmHg indicates inadequate tissue perfusion and is a strong indication for emergent fasciotomy.

Question 12151

Topic: 2. Trauma

A 25-year-old male sustains a closed tibial shaft fracture and later complains of pain out of proportion to the injury. Which of the following intra-compartmental pressure measurements most strongly indicates the need for emergent fasciotomy?

. Absolute pressure of 20 mmHg
. Absolute pressure of 25 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Mean arterial pressure minus compartment pressure > 40 mmHg
. Systolic blood pressure minus compartment pressure < 50 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The Delta P (Diastolic Blood Pressure minus Compartment Pressure) is the most reliable indicator for acute compartment syndrome. A Delta P of less than 30 mmHg represents inadequate tissue perfusion and is an absolute indication for emergent fasciotomy.

Question 12152

Topic: 2. Trauma

A 22-year-old male sustains bilateral femoral shaft fractures. On post-operative day 2, he develops confusion, hypoxia, and a petechial rash over his axillae. What is the primary pathophysiological mechanism thought to be responsible for this syndrome?

. Bacterial seeding of the pulmonary vasculature
. Deep vein thrombosis propagating to the pulmonary artery
. Mechanical occlusion of microvasculature by marrow fat droplets
. Release of systemic inflammatory mediators from crushed muscle
. Toxicity from polymethylmethacrylate bone cement

Correct Answer & Explanation

. Mechanical occlusion of microvasculature by marrow fat droplets

Explanation

Fat Embolism Syndrome (FES) clinically presents with hypoxia, neurologic changes, and a petechial rash. The mechanical theory suggests marrow fat droplets enter torn venous sinusoids during fracture or reaming, subsequently occluding the pulmonary microvasculature.

Question 12153

Topic: 2. Trauma

A 24-year-old male sustains a bilateral femur fracture. 48 hours later, he develops tachypnea, confusion, and a petechial rash over his axilla. What is the primary pathophysiologic mechanism underlying the most likely diagnosis?

. Release of inflammatory cytokines causing primary ARDS
. Mechanical obstruction of pulmonary capillaries by marrow fat and endothelial damage from free fatty acids
. Microthrombi formation due to severe systemic hypercoagulability
. Fat emboli lodging directly in the middle cerebral artery
. Aspiration of gastric contents during initial trauma

Correct Answer & Explanation

. Mechanical obstruction of pulmonary capillaries by marrow fat and endothelial damage from free fatty acids

Explanation

Fat embolism syndrome is caused by mechanical obstruction of the pulmonary vasculature by marrow fat droplets, coupled with a biochemical cascade where free fatty acids cause severe endothelial damage. This leads to the classic triad of hypoxemia, neurologic compromise, and petechial rash.

Question 12154

Topic: 2. Trauma

A 32-year-old male presents with a closed tibial shaft fracture and severe leg pain. His diastolic blood pressure is 85 mmHg. Intracompartmental pressure monitoring is performed. At what delta pressure (Delta P) threshold is a fasciotomy definitively indicated?

. Delta P < 45 mmHg
. Delta P > 30 mmHg
. Delta P < 30 mmHg
. Delta P > 45 mmHg
. Delta P < 15 mmHg

Correct Answer & Explanation

. Delta P < 30 mmHg

Explanation

Delta pressure (diastolic blood pressure minus intracompartmental pressure) is the most reliable indicator for compartment syndrome. A Delta P of less than 30 mmHg indicates inadequate tissue perfusion and is a definitive indication for urgent fasciotomy.

Question 12155

Topic: 2. Trauma

Which of the following correctly pairs the recombinant human bone morphogenetic protein (rhBMP) with its FDA-approved indication in orthopedic trauma?

. rhBMP-7 for acute open tibial shaft fractures treated with an intramedullary nail
. rhBMP-2 for recalcitrant tibial nonunions
. rhBMP-2 for acute open tibial shaft fractures treated with an intramedullary nail
. rhBMP-7 for acute closed femoral shaft fractures
. rhBMP-2 for delayed union of scaphoid fractures

Correct Answer & Explanation

. rhBMP-2 for acute open tibial shaft fractures treated with an intramedullary nail

Explanation

The FDA approved rhBMP-2 (Infuse) for the treatment of acute open tibial shaft fractures treated with an intramedullary nail, as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 (OP-1) was historically approved under a Humanitarian Device Exemption for recalcitrant tibial nonunions (defined as a nonunion present for at least 9 months with no radiographic signs of healing for 3 months) and posterolateral lumbar fusion, though it is currently largely unavailable.

Question 12156

Topic: 2. Trauma

A 32-year-old male is admitted after a high-energy tibial plateau fracture. He complains of increasing leg pain that is out of proportion to his injury. His blood pressure is 130/80 mmHg. Direct compartment pressure measurement of the anterior compartment reveals a pressure of 45 mmHg. What is the calculated Delta P, and what is the next appropriate step in management?

. Delta P is 85 mmHg; observation
. Delta P is 85 mmHg; immediate four-compartment fasciotomy
. Delta P is 35 mmHg; observation
. Delta P is 35 mmHg; immediate four-compartment fasciotomy
. Delta P is 45 mmHg; immediate four-compartment fasciotomy

Correct Answer & Explanation

. Delta P is 35 mmHg; observation

Explanation

Delta P is defined as the diastolic blood pressure minus the intracompartmental pressure (Delta P = Diastolic BP - Compartment Pressure). In this patient, 80 mmHg - 45 mmHg = 35 mmHg. The generally accepted threshold for surgical intervention (fasciotomy) for acute compartment syndrome is a Delta P of 30 mmHg or less. Since the Delta P is >30 mmHg, close clinical observation and serial neurovascular checks are indicated.

Question 12157

Topic: 2. Trauma
Gustilo-Anderson classification is crucial for decision-making in open fractures. A 30-year-old male sustains an open midshaft tibia fracture with a 12 cm laceration, extensive periosteal stripping, and exposed diaphyseal bone. Following aggressive debridement, the plastic surgeon determines that the wound cannot be closed primarily and will require a rotational gastrocnemius flap. Intravenous antibiotics are initiated. According to Gustilo-Anderson, how is this fracture classified?
. Type II
. Type IIIA
. Type IIIB
. Type IIIC
. Type IV

Correct Answer & Explanation

. Type IIIB

Explanation

The Gustilo-Anderson classification categorizes open fractures based on wound size, contamination, and soft-tissue injury. A Type IIIA fracture involves extensive soft-tissue stripping but maintains adequate soft-tissue coverage of the fractured bone (primary closure or skin grafting is possible). A Type IIIB fracture involves extensive soft-tissue injury with periosteal stripping and bone exposure, requiring a local or free soft-tissue flap for coverage. Type IIIC involves an arterial injury requiring repair for limb salvage.

Question 12158

Topic: Pelvic & Acetabular Trauma
An adult male is brought to the trauma bay following a high-speed motorcycle collision. He is hemodynamically unstable with a mechanically unstable anteroposterior compression (APC-III) pelvic ring injury. A commercial pelvic binder is applied. To optimize mechanical closure of the pelvic volume and minimize the risk of iatrogenic complications, the binder should be centered strictly over which anatomic landmarks?
. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis and L5 vertebral body
. Inferior pubic rami

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders must be centered directly over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume, particularly in "open book" (APC) injuries. Placement over the iliac crests or ASIS is anatomically too high and can paradoxically widen the pelvic floor, exacerbating bleeding and instability.

Question 12159

Topic: 2. Trauma

What is the initiating pathophysiological event in the development of acute compartment syndrome?

. Arterial occlusion leading to tissue ischemia
. Loss of functioning precapillary sphincters
. Obstruction of venous outflow
. Lymphatic system collapse
. Arteriovenous shunting

Correct Answer & Explanation

. Obstruction of venous outflow

Explanation

The cascade of acute compartment syndrome begins when an increase in intracompartmental pressure overcomes the low-pressure venous system. This obstruction of venous outflow leads to venous pooling, increased capillary hydrostatic pressure, and transudation of fluid. This creates a vicious cycle of increasing tissue pressure that eventually compromises capillary perfusion and arterial inflow.

Question 12160

Topic: 2. Trauma
A 30-year-old male sustains a vertically oriented (Pauwels Type III) femoral neck fracture. To maximize biomechanical stability and resist shear forces, which of the following internal fixation constructs is most appropriate?
. Three parallel cannulated screws in an inverted triangle configuration
. A sliding hip screw (DHS) with a derotation screw
. Two parallel cannulated screws placed inferiorly
. A short cephalomedullary nail
. Multiple threaded Kirschner wires

Correct Answer & Explanation

. A sliding hip screw (DHS) with a derotation screw

Explanation

In young adults with high-shear, vertically oriented femoral neck fractures (Pauwels Type III), biomechanical studies have consistently demonstrated that a fixed-angle device, such as a sliding hip screw (dynamic hip screw, DHS) combined with a derotation screw, provides superior construct stiffness and failure load compared to parallel cannulated screws.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page