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2. Trauma MCQs

Practice Set 299 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 5961

Topic: Pelvic & Acetabular Trauma

During an ilioinguinal approach for open reduction and internal fixation of an anterior column acetabular fracture, massive hemorrhage occurs as the surgeon dissects over the superior pubic ramus. This bleeding is most likely originating from an anastomosis between which of the following vessels?

. External iliac artery and internal pudendal artery
. Internal iliac artery and superior gluteal artery
. External iliac vein and inferior epigastric vein
. Internal pudendal artery and obturator artery
. Obturator vessels and inferior epigastric or external iliac vessels

Correct Answer & Explanation

. Obturator vessels and inferior epigastric or external iliac vessels

Explanation

The corona mortis ('crown of death') is a vascular anastomosis between the obturator vessels (internal iliac system) and the inferior epigastric or external iliac vessels. It lies on the posterior aspect of the superior pubic ramus at an average distance of 5 to 6 cm from the pubic symphysis and is at significant risk during the anterior approaches to the acetabulum.

Question 5962

Topic: 2. Trauma

Recent quantitative anatomical studies evaluating the vascularity of the proximal humerus have challenged historical teachings. In the context of a 4-part proximal humerus fracture, which artery is now recognized as providing the predominant blood supply to the humeral head?

. Anterior humeral circumflex artery
. Posterior humeral circumflex artery
. Thoracoacromial artery
. Circumflex scapular artery
. Profunda brachii artery

Correct Answer & Explanation

. Posterior humeral circumflex artery

Explanation

While classic literature (e.g., Laing) taught that the anterior humeral circumflex artery (via the arcuate artery) was the main blood supply, modern studies (such as those by Hettrich et al.) have demonstrated that the posterior humeral circumflex artery provides approximately 64% of the blood supply to the humeral head.

Question 5963

Topic: 2. Trauma

A 30-year-old male sustains a closed tibial shaft fracture. Two hours post-admission, he develops severe pain out of proportion to the injury and tense leg compartments. Which of the following intracompartmental pressure measurements represents the most absolute and reliable indication for an immediate fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Diastolic Blood Pressure minus Compartment Pressure < 30 mmHg
. Mean Arterial Pressure minus Compartment Pressure < 40 mmHg
. Systolic Blood Pressure minus Compartment Pressure < 30 mmHg
. Absolute compartment pressure equal to Central Venous Pressure

Correct Answer & Explanation

. Diastolic Blood Pressure minus Compartment Pressure < 30 mmHg

Explanation

The 'delta pressure' (Diastolic Blood Pressure minus the intracompartmental pressure) is the most accurate predictor for acute compartment syndrome. A delta pressure of less than 30 mmHg (e.g., DBP 70, Compartment Pressure 45 -> Delta = 25) indicates severe capillary bed occlusion and is an absolute indication for emergency fasciotomy.

Question 5964

Topic: Pelvic & Acetabular Trauma
A 35-year-old male presents with a closed pelvic ring injury after a motorcycle accident. Examination reveals a large, fluctuant, soft-tissue swelling over the greater trochanter. Aspiration yields serosanguinous fluid. What is the most appropriate management of this lesion to minimize infection risk prior to definitive pelvic fixation?
. Percutaneous aspiration alone
. Open debridement, sclerodesis, and primary closure
. Application of a compression dressing and delayed fixation
. Incision, thorough debridement, and delayed primary closure or negative pressure wound therapy
. Immediate pelvic fixation through the lesion

Correct Answer & Explanation

. Incision, thorough debridement, and delayed primary closure or negative pressure wound therapy

Explanation

The patient has a Morel-Lavallée lesion (closed degloving injury). These lesions are at high risk for infection if not addressed, especially if surgical incisions for fracture fixation are planned through or near the zone of injury. Large or established lesions are best managed by thorough open debridement and delayed primary closure or application of negative pressure wound therapy. Percutaneous aspiration alone has a high recurrence rate for large lesions and leaves necrotic fat in the dead space.

Question 5965

Topic: 2. Trauma

A 40-year-old male sustains a Schatzker VI tibial plateau fracture following a motor vehicle collision. On arrival, he has tense swelling of the leg, severe pain on passive stretch of the toes, and decreased sensation in the first webspace. Emergent four-compartment fasciotomy is planned. In a standard two-incision technique, through which incision is the deep posterior compartment accessed?

. Anterolateral incision
. Posteromedial incision
. Directly over the fibula
. Transverse anterior incision
. Posterior midline incision

Correct Answer & Explanation

. Posteromedial incision

Explanation

In a dual-incision technique for lower leg fasciotomies, the anterolateral incision is used to release the anterior and lateral compartments. The posteromedial incision (placed 1-2 cm posterior to the medial tibial border) is used to release the superficial posterior compartment and the deep posterior compartment. To access the deep posterior compartment, the soleus bridge must be detached from the medial tibia.

Question 5966

Topic: 2. Trauma

A 28-year-old male presents with a closed midshaft tibia fracture. He develops extreme pain out of proportion to his injury. Compartment pressures are measured. Which of the following absolute or differential pressure values is the most widely accepted threshold for indicating an emergency fasciotomy?

. Absolute compartment pressure of 20 mmHg
. Absolute compartment pressure of 25 mmHg
. Delta pressure (Diastolic blood pressure minus compartment pressure) less than 30 mmHg
. Delta pressure (Mean arterial pressure minus compartment pressure) less than 40 mmHg
. Delta pressure (Systolic blood pressure minus compartment pressure) less than 50 mmHg

Correct Answer & Explanation

. Delta pressure (Diastolic blood pressure minus compartment pressure) less than 30 mmHg

Explanation

A delta pressure (Diastolic blood pressure minus compartment pressure) of less than 30 mmHg is the most widely accepted and clinically validated threshold for diagnosing acute compartment syndrome and indicating fasciotomy. Absolute compartment pressures can be misleading, as tissue perfusion depends on the pressure gradient between the capillary bed and the interstitial space.

Question 5967

Topic: Pelvic & Acetabular Trauma

A 2-year-old female presents with untreated developmental dysplasia of the hip (DDH). Radiographs show a completely dislocated left hip with a false acetabulum. The surgeon plans an open reduction and pelvic osteotomy. Which of the following pelvic osteotomies hinges at the pubic symphysis and improves anterolateral coverage without altering the volume of the true acetabulum?

. Salter innominate osteotomy
. Pemberton osteotomy
. Dega osteotomy
. Chiari osteotomy
. Triple pelvic osteotomy

Correct Answer & Explanation

. Salter innominate osteotomy

Explanation

The Salter innominate osteotomy is a complete cut through the ilium extending from the greater sciatic notch to the anterior inferior iliac spine. The distal fragment is rotated anterolaterally, hinging at the pubic symphysis, to improve anterior and lateral coverage. Because it is a complete osteotomy of the ilium, it redirects the entire acetabulum but does not alter its intrinsic shape or volume. Pemberton and Dega are incomplete osteotomies that change acetabular volume.

Question 5968

Topic: Lower Extremity Trauma

The mechanical axis of the lower extremity is defined as a line drawn from the center of the femoral head to the center of the ankle joint. In a normal, well-aligned lower limb, where does this mechanical axis pass relative to the knee joint center?

. Exactly through the center of the knee joint
. 10 mm lateral to the center of the knee joint
. 8-10 mm medial to the center of the knee joint
. 25 mm medial to the center of the knee joint
. Through the lateral collateral ligament

Correct Answer & Explanation

. 8-10 mm medial to the center of the knee joint

Explanation

In a normally aligned human leg, the mechanical axis passes slightly medial to the geometric center of the knee joint (typically about 8 to 10 mm medial to the midpoint of the tibial plateau). This slight medial offset is why the medial compartment of the normal knee bears a larger percentage (approximately 60%) of the physiological weight-bearing load compared to the lateral compartment.

Question 5969

Topic: 2. Trauma
A 45-year-old male is brought to the trauma bay after a high-speed motorcycle collision. He has an Anteroposterior Compression (APC) Type III pelvic ring injury. He remains hypotensive (BP 75/40 mmHg) despite receiving 2 liters of crystalloid and 2 units of uncrossmatched PRBCs. A pelvic binder is correctly applied over the greater trochanters. A FAST ultrasound is negative. What is the most appropriate next step in management?
. CT scan of the abdomen and pelvis with IV contrast
. Exploratory laparotomy with four-quadrant packing
. Preperitoneal pelvic packing and/or angioembolization
. Application of an external fixator and transfer to the ICU
. Immediate operative internal fixation of the anterior and posterior ring

Correct Answer & Explanation

. Preperitoneal pelvic packing and/or angioembolization

Explanation

In a hemodynamically unstable patient with an unstable pelvic ring fracture and a negative FAST exam (effectively ruling out major intra-abdominal, intraperitoneal hemorrhage), the primary source of bleeding is assumed to be the retroperitoneal pelvic venous plexus or arterial injury. Immediate preperitoneal pelvic packing and/or pelvic angiography with embolization (dictated by institutional protocols) is the definitive life-saving intervention.

Question 5970

Topic: 2. Trauma

Proximal pole fractures of the scaphoid have a high rate of nonunion and avascular necrosis. This is primarily dictated by the intraosseous vascular anatomy of the scaphoid. Where does the dominant arterial supply enter the scaphoid?

. Through the volar surface at the proximal pole
. Through the dorsal ridge in the distal half of the bone
. Through the volar tubercle distally
. Through the scapholunate interosseous ligament proximally
. Through the radial styloid capsular attachments

Correct Answer & Explanation

. Through the dorsal ridge in the distal half of the bone

Explanation

The primary blood supply to the scaphoid (accounting for 70-80% of the intraosseous vascularity) enters through the dorsal ridge in the distal half of the bone. The blood flow is retrograde to the proximal pole, making proximal pole fractures highly susceptible to avascular necrosis due to disruption of this retrograde vascular supply.

Question 5971

Topic: 2. Trauma

A 78-year-old male sustains an Anderson-D'Alonzo Type II odontoid fracture after a ground-level fall. Imaging reveals 7 mm of posterior displacement. If conservative management is selected, which of the following characteristics is the strongest independent predictor of nonunion?

. Displacement greater than 5 mm
. Fracture comminution at the base
. Delay in diagnosis greater than 48 hours
. Associated C1 posterior arch fracture
. The presence of degenerative cervical spondylosis

Correct Answer & Explanation

. Displacement greater than 5 mm

Explanation

For Type II odontoid fractures, known risk factors for nonunion include initial displacement > 5 mm, posterior displacement, angulation > 10 degrees, and advanced age (typically > 50 or 65 depending on the study). Initial displacement greater than 5 mm is widely cited in literature as the strongest single predictive factor for nonunion, often prompting surgical consideration even in older patients.

Question 5972

Topic: 2. Trauma

A 42-year-old male requires open reduction and internal fixation for a complex posterolateral tibial plateau fracture. A posterolateral (Frosch) approach is planned. To safely access the posterolateral articular surface, the deep surgical interval is developed between which two structures?

. Lateral head of gastrocnemius and soleus
. Lateral head of gastrocnemius and biceps femoris
. Iliotibial band and biceps femoris
. Popliteus and soleus
. Lateral collateral ligament and popliteus

Correct Answer & Explanation

. Lateral head of gastrocnemius and biceps femoris

Explanation

The classic posterolateral approach to the tibial plateau (such as the Frosch approach) uses an interval between the lateral head of the gastrocnemius (retracted medially) and the biceps femoris (retracted laterally). This provides direct access to the posterior aspect of the lateral tibial plateau. Care must be taken to identify and protect the common peroneal nerve, which lies directly posterior to the biceps femoris tendon.

Question 5973

Topic: 2. Trauma

According to the Young and Burgess classification, a Lateral Compression Type II (LC-2) pelvic ring injury is characterized by anterior ring fractures and which of the following posterior ring injury patterns?

. Sacral compression fracture on the side of impact
. Complete disruption of the sacroiliac joint with anterior and posterior ligament rupture
. Crescent fracture of the ilium on the side of impact
. Bilateral sacral alar fractures with spino-pelvic dissociation
. Avulsion fracture of the ischial spine and sacrotuberous ligament

Correct Answer & Explanation

. Crescent fracture of the ilium on the side of impact

Explanation

In the Young and Burgess classification, a Lateral Compression Type I (LC-1) injury involves a sacral compression fracture. An LC-2 injury involves a crescent (ilium) fracture on the side of impact due to the internal rotation force continuing past the sacrum, causing the strong intact posterior SI ligaments to avulse a piece of the posterior ilium. An LC-3 is a 'windswept' pelvis, featuring an LC injury on the impacted side and an APC-type injury on the contralateral side.

Question 5974

Topic: 2. Trauma
A 30-year-old male sustains a vertically oriented, displaced femoral neck fracture (Pauwels Type III) after falling from a height. Open reduction and internal fixation is planned. Biomechanical studies indicate that which of the following fixation constructs provides the greatest resistance to vertical shear forces and varus collapse for this specific fracture pattern?
. Three parallel cannulated screws in an inverted triangle configuration
. Two parallel cannulated screws placed centrally
. A sliding hip screw with a supplemental derotation screw
. A cephalomedullary nail with a single lag screw
. Multiple threaded Steinmann pins

Correct Answer & Explanation

. A sliding hip screw with a supplemental derotation screw

Explanation

Vertical femoral neck fractures in young adults (Pauwels Type III) are subject to high shear forces, making them prone to varus collapse and nonunion. Biomechanical studies have consistently shown that a fixed-angle device, such as a sliding hip screw (SHS) with a supplemental derotation screw (to control rotational forces), provides superior mechanical stability and resistance to vertical shear compared to multiple parallel cannulated screws for high-angle (vertical) femoral neck fractures.

Question 5975

Topic: 2. Trauma
A 28-year-old male sustains a vertically oriented femoral neck fracture (Pauwels III). Biomechanical studies show which fixation construct provides the highest load to failure and greatest resistance to shear forces for this specific fracture pattern?
. Three parallel cancellous screws
. Sliding hip screw with a derotation screw
. Proximal femoral nail
. Two parallel cancellous screws
. Dynamic condylar screw

Correct Answer & Explanation

. Sliding hip screw with a derotation screw

Explanation

Biomechanical studies demonstrate that a sliding hip screw (SHS) with an anti-rotation screw provides superior fixation for vertically oriented (Pauwels III) femoral neck fractures compared to multiple cancellous screws, primarily by better resisting the high shear forces across the vertical fracture line.

Question 5976

Topic: 2. Trauma

A 35-year-old male is admitted with a closed tibia fracture. Eight hours later, he develops severe pain out of proportion to the injury, exacerbated by passive stretch of the toes. Intracompartmental pressure monitoring is planned. What is the generally accepted threshold for performing a fasciotomy?

. Absolute compartment pressure > 15 mmHg
. Absolute compartment pressure > 20 mmHg
. Delta pressure (Diastolic blood pressure minus compartment pressure) < 30 mmHg
. Delta pressure (Systolic blood pressure minus compartment pressure) < 30 mmHg
. Delta pressure (Mean arterial pressure minus compartment pressure) < 40 mmHg

Correct Answer & Explanation

. Delta pressure (Diastolic blood pressure minus compartment pressure) < 30 mmHg

Explanation

The threshold for diagnosing acute compartment syndrome and indicating a fasciotomy is a delta pressure (Diastolic Blood Pressure - Compartment Pressure) of less than 30 mmHg. This measurement accounts for systemic perfusion pressure, making it more accurate than absolute compartment pressure alone.

Question 5977

Topic: Pelvic & Acetabular Trauma
In an anteroposterior compression (APC) type II pelvic ring injury (open book), the pubic symphysis is diastatic > 2.5 cm. Which posterior pelvic ligaments are disrupted, and which remain intact?
. Anterior sacroiliac ligaments intact; posterior sacroiliac ligaments disrupted
. Both anterior and posterior sacroiliac ligaments disrupted
. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments disrupted; posterior sacroiliac ligaments intact
. Sacrotuberous ligaments intact; sacrospinous ligaments disrupted
. All pelvic ligaments remain intact but stretched

Correct Answer & Explanation

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments disrupted; posterior sacroiliac ligaments intact

Explanation

In an APC-II injury, the pubic symphysis diastasis (>2.5 cm) is accompanied by tearing of the anterior sacroiliac ligaments, the sacrotuberous ligaments, and the sacrospinous ligaments. The strong posterior sacroiliac ligaments remain intact, leading to rotational instability but vertical stability.

Question 5978

Topic: Pelvic & Acetabular Trauma
A 45-year-old male sustains an anteroposterior compression type III (APC-III) pelvic ring injury following a crush accident. After initial resuscitation, an anterior external fixator is placed. What is the primary biomechanical limitation of an anterior external fixator in this specific injury pattern?
. Inability to adequately control external rotation of the hemipelvis
. Interference with necessary exploratory laparotomies
. Inability to control posterior ring instability
. Inability to control anterior vertical shear forces
. Excessively high risk of pin tract infection delaying definitive care

Correct Answer & Explanation

. Inability to control posterior ring instability

Explanation

An APC-III injury involves complete disruption of both the anterior ring (symphysis pubis) and the posterior sacroiliac complex (anterior and posterior SI ligaments, sacrotuberous, sacrospinous). An anterior external fixator cannot adequately control the highly unstable posterior ring. Posterior stabilization (e.g., SI screws or posterior plating) is mandatory.

Question 5979

Topic: 2. Trauma

A 25-year-old manual laborer presents with an acute scaphoid proximal pole fracture and requests surgical fixation. What is the anatomical basis for the high rate of avascular necrosis and nonunion specifically associated with proximal pole fractures?

. The primary blood supply is via the volar carpal branch of the radial artery.
. The dominant blood supply enters the distal pole via the dorsal carpal branch and flows in a retrograde fashion.
. The superficial palmar arch provides exclusively tenuous end-arterial flow to the proximal pole.
. The proximal pole is intracapsular and devoid of periosteal coverage, relying solely on synovial diffusion.
. The ulnar artery supplies the proximal pole via an inconsistent branch of the deep palmar arch.

Correct Answer & Explanation

. The dominant blood supply enters the distal pole via the dorsal carpal branch and flows in a retrograde fashion.

Explanation

The primary blood supply to the scaphoid comes from the dorsal carpal branch of the radial artery, which enters the scaphoid at the distal pole and waist, flowing in a retrograde direction to the proximal pole. Fractures at the proximal pole disrupt this retrograde flow, heavily predisposing the proximal fragment to ischemia and AVN.

Question 5980

Topic: 2. Trauma

A 32-year-old previously healthy male sustains an isolated, closed, transverse fracture of the middle third of the femoral shaft in a motor vehicle collision. He is hemodynamically stable without head or chest trauma. What is the optimal timing for intramedullary nailing of this fracture?

. Immediately within the first 6 hours to prevent fat embolism
. Within 24 hours of injury
. Between 48 and 72 hours to allow the inflammatory response to subside
. At 5 to 7 days post-injury to optimize the biological fracture hematoma
. After 2 weeks to minimize the risk of ARDS

Correct Answer & Explanation

. Within 24 hours of injury

Explanation

In a hemodynamically stable patient without severe physiological insults (polytrauma, severe head, or chest injuries requiring damage control orthopedics), early definitive fixation of femoral shaft fractures (within 24 hours) is the standard of care. It significantly reduces the rates of pulmonary complications (ARDS, pneumonia), mortality, and hospital length of stay.

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