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 5521
Topic: 2. Trauma
Which bone morphogenetic protein (BMP) is FDA-approved as an alternative to autograft for the treatment of acute, open tibial shaft fractures stabilized with an intramedullary nail?
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 stabilized with an intramedullary nail. rhBMP-7 (Osteogenic Protein-1 or OP-1) previously had a Humanitarian Device Exemption (HDE) for recalcitrant long bone nonunions but is no longer commercially available in the US for this indication.
Question 5522
Topic: 2. Trauma
A 24-year-old male sustains a high-energy pelvic ring injury after a motor vehicle collision. CT imaging demonstrates a displaced crescent fracture of the ilium extending into the posterior aspect of the sacroiliac joint, consistent with a Day Type II lateral compression injury.
What is the most biomechanically stable method of surgical fixation for this specific posterior ring injury?
Correct Answer & Explanation
. Combined iliosacral screw fixation for the sacroiliac component and lateral plating for the iliac wing fracture
Explanation
Day Type II crescent fractures involve a major fracture line exiting the iliac wing, but a substantial portion of the posterior ilium remains attached to the sacrum via the posterior SI ligaments. Biomechanical studies have demonstrated that for Day Type II fractures (where the fracture extends into the SI joint), combining an iliosacral screw to stabilize the SI joint component with an orthopedic plate for the iliac wing fracture provides the most stable construct, superior to either method alone.
Question 5523
Topic: 2. Trauma
A 28-year-old male sustains a severe closed crush injury to his left leg. Over the next 4 hours, his pain becomes disproportionate to the injury, and he experiences extreme pain with passive stretch of his toes.
Compartment pressure monitoring is initiated. Which of the following thresholds represents the most widely accepted absolute indication for a four-compartment fasciotomy?
The diagnosis of acute compartment syndrome is primarily clinical, but when using intracompartmental pressure monitoring, the 'Delta P' is the most reliable metric. Delta P is calculated as the Diastolic Blood Pressure minus the Compartment Pressure. A Delta P of less than 30 mmHg indicates inadequate tissue perfusion pressure and is the universally accepted threshold indicating the need for emergent fasciotomy. Using absolute compartment pressures alone (e.g., >30 mmHg) can lead to unnecessary surgeries, especially in hypertensive patients.
Question 5524
Topic: Pelvic & Acetabular Trauma
A 45-year-old female presents in hemorrhagic shock after a severe crush injury. Pelvic radiographs show an APC-III pelvic ring injury (diastasis of the symphysis pubis and bilateral SI joint disruption). A pelvic binder is applied and fluid resuscitation initiated, but she remains hemodynamically unstable. In this clinical scenario, what is the most statistically likely source of her pelvic hemorrhage?
Correct Answer & Explanation
. Presacral venous plexus
Explanation
Venous bleeding accounts for 80-90% of all pelvic hemorrhage in pelvic ring injuries. The presacral venous plexus and prevesical veins are the most common sources. While arterial bleeding (from the superior gluteal, pudendal, or obturator arteries) can be severe, brisk, and often requires angioembolization, the venous plexus is overwhelmingly the most likely overall source of bleeding.
Question 5525
Topic: 2. Trauma
A 32-year-old male sustains a high-energy trauma. Imaging demonstrates a vertically oriented femoral neck fracture (Pauwels III). Which of the following biomechanical environments is most responsible for the high rate of nonunion and osteonecrosis in this specific fracture pattern?
Correct Answer & Explanation
. High shear stress promoting varus displacement
Explanation
Pauwels III femoral neck fractures have a fracture line greater than 50 degrees relative to the horizontal. This vertical orientation changes the physiological loading from compressive forces to high shear forces. This shear stress promotes varus displacement and instability, leading to the known higher risks of nonunion and avascular necrosis in young adults.
Question 5526
Topic: 2. Trauma
A 25-year-old male involved in a motorcycle crash sustains an anteroposterior compression (APC) type III pelvic ring injury. He arrives hemodynamically unstable, and a pelvic binder is immediately applied. What is the most common anatomic source of massive retroperitoneal hemorrhage in this fracture pattern?
Correct Answer & Explanation
. Presacral and prevesical venous plexus
Explanation
While arterial injuries (such as to the superior gluteal or internal pudendal arteries) can cause rapid and devastating hemorrhage requiring embolization, the vast majority (80-90%) of bleeding in pelvic fractures originates from the presacral and prevesical venous plexuses, as well as the raw cancellous bone edges. The application of a pelvic binder reduces pelvic volume and facilitates the tamponade of this venous bleeding.
Question 5527
Topic: 2. Trauma
A 40-year-old skier sustains a highly comminuted Schatzker Type VI tibial plateau fracture. Over the next few hours, he develops tense swelling of the lower leg, paresthesias in the first web space, and pain out of proportion to the injury with passive toe extension. If compartment pressures are measured to confirm acute compartment syndrome, which of the following provides the most reliable threshold for diagnosing the condition?
Acute compartment syndrome is primarily a clinical diagnosis, but pressure measurements are critical in equivocal cases or obtunded patients. The most reliable and widely accepted metric is the delta pressure (ΔP), calculated as the Diastolic Blood Pressure minus the Intracompartmental Pressure. A delta pressure of less than 30 mmHg strongly supports the diagnosis and dictates emergent fasciotomy, as capillary perfusion relies on the gradient with diastolic pressure.
Question 5528
Topic: 2. Trauma
A 45-year-old man is involved in a high-speed motor vehicle collision. The AP pelvis radiograph demonstrates an acetabular fracture.
According to the Letournel classification, which of the following radiographic lines is typically disrupted in an isolated transverse acetabular fracture?
Correct Answer & Explanation
. Both the iliopectineal and ilioischial lines
Explanation
A transverse acetabular fracture is an elementary fracture pattern that involves a single fracture line crossing the acetabulum horizontally. Because it bisects both the anterior and posterior columns of the acetabulum, it disrupts both the iliopectineal line (anterior column marker) and the ilioischial line (posterior column marker) on a standard AP pelvis radiograph.
Question 5529
Topic: 2. Trauma
A 29-year-old man sustains a high-energy injury resulting in a femoral neck fracture. Radiographs reveal a Pauwels type III pattern. Which of the following mechanical factors most significantly contributes to the high rate of nonunion and failure of fixation in this specific fracture pattern?
Correct Answer & Explanation
. High shearing forces across the fracture site
Explanation
The Pauwels classification of femoral neck fractures is based on the angle of the fracture line relative to the horizontal plane. A Pauwels type III fracture is highly vertical (angle > 50 degrees). This vertical orientation converts normal hip joint reaction forces into destructive shear forces at the fracture site, predisposing it to varus collapse, nonunion, and implant failure, unlike horizontal fractures which experience stabilizing compressive forces.
Question 5530
Topic: 2. Trauma
A 40-year-old pedestrian is struck by a vehicle and sustains a complex proximal tibia fracture.
Imaging confirms a Schatzker Type IV fracture involving the medial tibial plateau. What is the typical mechanism of injury for this specific fracture pattern, and which anatomic structure is placed under the highest tensile stress?
Correct Answer & Explanation
. Varus force; Lateral collateral ligament (LCL)
Explanation
A Schatzker Type IV fracture involves a fracture of the medial tibial plateau. Unlike lateral plateau fractures (which are typically low-energy valgus injuries), a medial plateau fracture usually results from a high-energy varus force combined with an axial load. This mechanism places extreme tension on the lateral-sided structures, frequently leading to associated Lateral Collateral Ligament (LCL), posterolateral corner, and/or peroneal nerve injuries.
Question 5531
Topic: 2. Trauma
According to Perren's strain theory of bone healing, primary bone healing (osteonal reconstruction without callus formation) can only occur under conditions of absolute stability. What is the maximum interfragmentary strain tolerated for primary bone healing to occur?
Correct Answer & Explanation
. < 2%
Explanation
Perren's strain theory states that the type of tissue that forms in a fracture gap is dictated by the mechanical strain. Primary bone healing requires absolute stability, meaning the interfragmentary strain must be less than 2%. Strains between 2% and 10% allow for secondary bone healing (callus formation), typically seen with relative stability (e.g., intramedullary nailing or bridge plating). Granulation tissue tolerates up to 100% strain.
Question 5532
Topic: 2. Trauma
A poly-trauma patient presents hemodynamically unstable with an anteroposterior compression (APC-III) pelvic ring injury. A circumferential pelvic binder is requested to reduce pelvic volume and control hemorrhage. To be anatomically effective, the binder must be centered precisely over which of the following landmarks?
Correct Answer & Explanation
. Greater trochanters
Explanation
For optimal mechanical advantage and effective reduction of an 'open book' pelvic fracture (APC type), a pelvic binder must be applied directly over the greater trochanters of the femurs. Applying it higher, such as over the iliac crests, is a common error that fails to adequately close the pelvic ring and can paradoxically open the true pelvis.
Question 5533
Topic: 2. Trauma
A 28-year-old male sustains a closed comminuted tibial shaft fracture.
Two hours post-injury, he develops severe leg pain unyielding to narcotics. His blood pressure is 120/80 mmHg. Intracompartmental pressure monitoring is performed. Based on current guidelines, which measurement dictates an emergent 4-compartment fasciotomy?
Acute compartment syndrome is classically defined by tissue hypoperfusion. The absolute compartment pressure is less reliable than the differential pressure (Delta P). A Delta P (Diastolic Blood Pressure minus Compartment Pressure) of less than 30 mmHg is an absolute indication for emergency fasciotomy, as capillary perfusion gradient is lost when tissue pressure approaches the diastolic pressure.
Question 5534
Topic: 2. Trauma
A 42-year-old female sustains a high-energy trauma resulting in a complex bicondylar tibial plateau fracture.
When planning a standard dual-incision approach (anterolateral and posteromedial) for open reduction and internal fixation, what neurovascular structure is most directly at risk during the superficial dissection of the posteromedial approach?
Correct Answer & Explanation
. Saphenous nerve
Explanation
The posteromedial approach to the proximal tibia utilizes the interval between the pes anserinus (retracted anteriorly) and the medial head of the gastrocnemius (retracted posteriorly). During the superficial dissection, the saphenous nerve and the great saphenous vein are directly at risk and must be carefully mobilized and protected. The common peroneal nerve is at risk laterally. The popliteal artery is posterior to the popliteus and is typically protected by the gastrocnemius during this approach.
Question 5535
Topic: 2. Trauma
A 78-year-old male presents after a fall from standing. CT of the cervical spine demonstrates a displaced Type II odontoid fracture. Which of the following factors has been shown in the literature to be the strongest predictor of nonunion if this patient is treated non-operatively in a cervical collar?
Correct Answer & Explanation
. Initial fracture displacement greater than 5 mm
Explanation
Type II odontoid fractures have a high rate of nonunion, particularly in the elderly. Risk factors for nonunion include patient age >50 years, initial fracture displacement >5 mm, posterior displacement of the dens, and initial angulation >10 degrees. While halo vests provide stiffer immobilization than collars, they carry significant morbidity in the elderly. The degree of initial displacement (>5 mm) remains one of the most critical intrinsic fracture characteristics predicting failure of non-operative management.
Question 5536
Topic: 2. Trauma
A 32-year-old male develops extreme pain out of proportion, pain with passive stretch, and tense compartments following a closed tibial shaft fracture. Which of the following best describes the fundamental pathophysiologic mechanism leading to cellular hypoxia and tissue death in acute compartment syndrome?
Correct Answer & Explanation
. Decreased local arteriovenous (AV) pressure gradient leading to capillary collapse
Explanation
The pathophysiology of compartment syndrome is driven by an increase in interstitial tissue pressure within a closed non-yielding fascial space. As tissue pressure rises, it quickly surpasses the low capillary venous pressure, severely impairing venous outflow. This leads to a decreased arteriovenous (AV) pressure gradient, resulting in diminished local capillary blood flow, capillary collapse, ischemia, and subsequent muscle/nerve necrosis. Arterial inflow is typically maintained until very late, which is why pulses are usually palpable even in established compartment syndrome.
Question 5537
Topic: 2. Trauma
A 25-year-old male sustains a high-energy Pauwels type III femoral neck fracture. In a young adult with this vertical fracture pattern, which of the following internal fixation constructs biomechanically offers the greatest resistance to vertical shear forces and varus collapse?
Correct Answer & Explanation
. Sliding hip screw with a supplemental derotational screw
Explanation
Pauwels type III femoral neck fractures have a vertical orientation (>50 degrees) and are subjected to high shear forces rather than compressive forces. Biomechanical studies have consistently demonstrated that a fixed-angle device, such as a sliding hip screw (SHS) with a supplemental derotational screw, provides superior stability against vertical shear and varus collapse compared to multiple cancellous screws in these specific high-angle fractures.
Question 5538
Topic: 2. Trauma
A 22-year-old soccer player sustains a twisting injury to his knee during a match. Radiographs reveal a small elliptical bone fragment adjacent to the lateral tibial plateau (Segond fracture). Based on this radiographic finding, which physical exam maneuver is most likely to be positive in this patient?
Correct Answer & Explanation
. Positive pivot shift test
Explanation
A Segond fracture is an avulsion fracture of the anterolateral ligament (ALL) and lateral capsule from the lateral tibial plateau. It is highly pathognomonic (up to 75-100% predictive value) for an anterior cruciate ligament (ACL) tear. The pivot shift test is the most specific physical examination finding for assessing rotational laxity associated with an ACL-deficient knee.
Question 5539
Topic: Lower Extremity Trauma
A 45-year-old male sustains a high-energy Schatzker IV tibial plateau fracture. Given the classic displacement pattern of this specific injury, which of the following is the most appropriate surgical approach and fixation strategy to properly neutralize the deforming forces?
Correct Answer & Explanation
. Posteromedial approach with a medial buttress (anti-glide) plate
Explanation
A Schatzker IV fracture involves the medial tibial plateau and is typically the result of high-energy varus forces, often combined with an axial load. The primary deforming force drives the medial fragment into varus and posterior subluxation. The biomechanically sound treatment requires a posteromedial approach with a medial buttress (or anti-glide) plate to physically resist the varus and posterior displacement.
Question 5540
Topic: 2. Trauma
A 28-year-old male is admitted after a motorcycle accident with a closed, comminuted midshaft tibial fracture. Four hours post-injury, he develops severe, escalating leg pain out of proportion to his injury and pain with passive stretch of his great toe. Intracompartmental pressure monitoring is performed. What is the most widely accepted objective pressure criterion indicating the need for an emergent four-compartment fasciotomy?
Acute compartment syndrome is a surgical emergency. The most reliable objective measure is the delta pressure, calculated as the patient's diastolic blood pressure minus the measured intracompartmental pressure. A delta pressure of less than 30 mmHg (meaning the compartment pressure is approaching the diastolic pressure) is an absolute indication for emergent fasciotomy to prevent irreversible muscle and nerve necrosis.
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