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Pelvic & Acetabular Trauma MCQs

Practice Set 34 of 35

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

Question 661

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the trauma bay in hemorrhagic shock following a high-speed motorcycle collision. Pelvic radiographs reveal an anteroposterior compression type III (APC-III) pelvic ring injury. A circumferential pelvic binder is requested. Over which specific anatomic landmark should the binder be centered to be most effective?
. Anterior superior iliac spines
. Iliac crests
. Pubic symphysis
. Sacral promontory
. Greater trochanters

Correct Answer & Explanation

. Greater trochanters

Explanation

To effectively reduce pelvic volume and control venous bleeding in mechanically unstable pelvic ring injuries, a pelvic binder or sheet must be centered directly over the greater trochanters. Placing it higher (e.g., over the iliac crests) can paradoxically distract the pelvic brim.

Question 662

Topic: Pelvic & Acetabular Trauma
According to the Young-Burgess classification, an anterior posterior compression type II (APC-II) pelvic ring injury is classically characterized by the rupture of the anterior sacroiliac ligaments along with which other major ligamentous complexes?
. Posterior sacroiliac ligaments only
. Sacrotuberous and sacrospinous ligaments
. Iliolumbar ligaments
. Sacrospinous and posterior sacroiliac ligaments
. Symphyseal ligaments only with intact posterior structures

Correct Answer & Explanation

. Sacrotuberous and sacrospinous ligaments

Explanation

APC-I involves pubic symphysis diastasis (<2.5 cm) with intact posterior ligaments. APC-II involves a symphysis diastasis (>2.5 cm) with rupture of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but the strong posterior sacroiliac ligaments remain intact, causing rotational instability but vertical stability. APC-III involves complete disruption including the posterior SI ligaments.

Question 663

Topic: Pelvic & Acetabular Trauma

In an anteroposterior compression type II (APC-II) pelvic ring injury, which of the following sets of ligaments are characteristically ruptured?

. Symphyseal ligaments and anterior sacroiliac ligaments only
. Symphyseal ligaments, anterior and posterior sacroiliac ligaments
. Anterior sacroiliac ligaments and sacrospinous ligaments only
. Symphyseal ligaments, sacrospinous, sacrotuberous, and anterior sacroiliac ligaments
. Iliolumbar ligaments and posterior sacroiliac ligaments

Correct Answer & Explanation

. Symphyseal ligaments, sacrospinous, sacrotuberous, and anterior sacroiliac ligaments

Explanation

An APC-II injury (an 'open book' pelvis) involves the rupture of the anterior symphyseal ligaments, the pelvic floor ligaments (sacrospinous and sacrotuberous), and the anterior sacroiliac ligaments. Crucially, the strong posterior sacroiliac ligaments remain intact, providing vertical stability but allowing significant rotational instability.

Question 664

Topic: Pelvic & Acetabular Trauma
An anteroposterior compression (APC) Type III pelvic ring injury involves complete disruption of the pubic symphysis and both the anterior and posterior sacroiliac ligaments. What is statistically the most common anatomical source of life-threatening hemorrhage in such injuries?
. Superior gluteal artery
. Presacral venous plexus
. External iliac artery
. Obturator artery
. Internal pudendal artery

Correct Answer & Explanation

. Presacral venous plexus

Explanation

While arterial bleeding (e.g., superior gluteal or internal pudendal) can be fatal and requires embolization, the majority (approximately 80%) of massive retroperitoneal bleeding in pelvic ring disruptions originates from the presacral venous plexus and bleeding cancellous bone surfaces.

Question 665

Topic: Pelvic & Acetabular Trauma
In a hemodynamically unstable patient with an anterior-posterior compression (APC) type III pelvic ring injury, what is the most appropriate anatomical landmark for the correct placement of a circumferential pelvic binder?
. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis
. L5-S1 junction

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder should be centered over the greater trochanters to effectively close the pelvic volume and reduce pubic symphysis diastasis. Placement higher over the iliac crests is less effective and can paradoxically open the pelvis in some fracture patterns.

Question 666

Topic: Pelvic & Acetabular Trauma

To maximize mechanical advantage and effectively reduce pelvic volume in a hemodynamically unstable anterior-posterior compression (APC) pelvic ring injury, a pelvic binder should be centered precisely over which anatomical landmark?

. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis
. Sacroiliac joints

Correct Answer & Explanation

. Greater trochanters

Explanation

For optimal biomechanical reduction of a pelvic ring injury and to appropriately decrease intrapelvic volume to tamponade bleeding, a pelvic binder or sheet must be placed at the level of the greater trochanters. Placement higher over the iliac crests is less effective and may cause abdominal compression.

Question 667

Topic: Pelvic & Acetabular Trauma

A 30-year-old male presents with an acute lateral compression type II (LC-II) pelvic ring injury. Which of the following ligaments is considered the strongest posterior stabilizer of the pelvic ring?

. Sacrotuberous ligament
. Sacrospinous ligament
. Anterior sacroiliac ligament
. Interosseous sacroiliac ligament
. Iliolumbar ligament

Correct Answer & Explanation

. Interosseous sacroiliac ligament

Explanation

The interosseous sacroiliac ligament is the strongest ligament in the body and serves as the primary stabilizer of the posterior pelvic ring. It effectively resists anteroposterior translation and extreme rotational forces.

Question 668

Topic: Pelvic & Acetabular Trauma
A patient arrives hypotensive after a high-speed collision, with an anteroposterior compression (APC) type III pelvic ring injury. Where is the most biomechanically effective anatomical location to apply a pelvic binder?
. Over the iliac crests
. Directly over the greater trochanters
. Superior to the anterior superior iliac spines (ASIS)
. At the level of the umbilicus
. Midway down the femoral shafts

Correct Answer & Explanation

. Directly over the greater trochanters

Explanation

A pelvic binder must be applied directly over the greater trochanters to effectively close the pelvic volume and stabilize the symphysis. Placing it higher over the iliac crests can paradoxically open the pelvis further.

Question 669

Topic: Pelvic & Acetabular Trauma
A hemodynamically unstable patient arrives after a severe crush injury. Pelvic radiographs demonstrate an anterior-posterior compression (APC) Type III pelvic ring injury. After placing a pelvic binder, the patient remains hypotensive despite massive transfusion. A FAST exam is negative. What is the most appropriate next step?
. Immediate CT abdomen and pelvis
. Pre-peritoneal pelvic packing and/or angioembolization
. Exploratory laparotomy
. Application of an external fixator in the emergency department
. Bilateral lower extremity skeletal traction

Correct Answer & Explanation

. Pre-peritoneal pelvic packing and/or angioembolization

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST exam, the pelvis is the primary source of life-threatening hemorrhage. Pre-peritoneal pelvic packing and/or pelvic angiography with embolization are the immediate interventions of choice.

Question 670

Topic: Pelvic & Acetabular Trauma

In the Young-Burgess classification of pelvic ring injuries, an Anterior Posterior Compression Type II (APC-II) injury is characterized by rupture of which primary ligamentous structures, leading to rotational instability but maintained vertical stability?

. Symphysis pubis, anterior sacroiliac, and posterior sacroiliac ligaments
. Symphysis pubis, anterior sacroiliac, sacrotuberous, and sacrospinous ligaments
. Symphysis pubis and posterior sacroiliac ligaments only
. Posterior sacroiliac, sacrotuberous, and sacrospinous ligaments only
. Iliolumbar and posterior sacroiliac ligaments

Correct Answer & Explanation

. Symphysis pubis, anterior sacroiliac, sacrotuberous, and sacrospinous ligaments

Explanation

An APC-II pelvic ring injury involves widening of the pubic symphysis (>2.5 cm) and disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. This results in rotational instability ('open book' pelvis) but maintains vertical stability because the strong posterior sacroiliac ligaments remain intact.

Question 671

Topic: Pelvic & Acetabular Trauma
A hemodynamically unstable trauma patient is brought to the emergency department with an anteroposterior compression type III (APC-III) pelvic ring injury. In the initial resuscitation phase, where is the most anatomically appropriate location to apply a circumferential pelvic binder?
. Over the iliac crests
. Over the anterior superior iliac spines
. Directly over the greater trochanters
. Inferior to the pubic symphysis
. Around the proximal thighs

Correct Answer & Explanation

. Directly over the greater trochanters

Explanation

A pelvic binder should be centered directly over the greater trochanters to effectively reduce pelvic volume and control venous bleeding. Placement higher over the iliac crests is less effective and may cause paradoxical pelvic widening.

Question 672

Topic: Pelvic & Acetabular Trauma

An unstable pelvic ring injury is suspected in a hypotensive trauma patient. A pelvic binder is applied in the trauma bay. To optimally reduce pelvic volume and control venous hemorrhage, the binder should be centered directly over which anatomic landmarks?

. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Pubic symphysis
. Ischial tuberosities

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder should be centered directly over the greater trochanters to generate the appropriate force vector to close the pelvic ring. Placement over the iliac crests is incorrect and can paradoxically widen the true pelvis, worsening hemorrhage.

Question 673

Topic: Pelvic & Acetabular Trauma
In the emergent management of a hemodynamically unstable patient with an anteroposterior compression type III (APC-III) pelvic ring injury, where is the optimal anatomical position for a pelvic circumferential compression device?
. At the level of the iliac crests
. Just proximal to the umbilicus
. Centered directly over the greater trochanters
. At the level of the anterior superior iliac spines
. Around the proximal thighs

Correct Answer & Explanation

. Centered directly over the greater trochanters

Explanation

A pelvic binder must be centered precisely over the greater trochanters to effectively close the pelvic volume and safely stabilize the pelvic ring. Placement over the iliac crests is a common error that can exacerbate the deformity or provide inadequate compression.

Question 674

Topic: Pelvic & Acetabular Trauma

A 45-year-old male presents in hemorrhagic shock after a motorcycle crash. Radiographs show a vertical shear pelvic fracture. A pelvic binder is applied, but he remains hypotensive. FAST exam is negative. According to orthopedic trauma guidelines, the source of massive retroperitoneal hemorrhage in pelvic ring disruptions most commonly originates from which of the following?

. Superior gluteal artery
. Internal pudendal artery
. Presacral venous plexus and cancellous bone
. External iliac artery
. Obturator artery

Correct Answer & Explanation

. Presacral venous plexus and cancellous bone

Explanation

While arterial injuries can cause rapid exsanguination, up to 80% of hemorrhage in severe pelvic ring disruptions is venous in origin, primarily arising from the presacral venous plexus and bleeding from fractured cancellous bone.

Question 675

Topic: Pelvic & Acetabular Trauma

Which of the following is considered an unstable pelvic ring injury according to the Young-Burgess classification?

. Lateral Compression Type I (LC-I)
. Anterior-Posterior Compression Type I (APC-I)
. Lateral Compression Type II (LC-II)
. Vertical Shear (VS)
. Anterior-Posterior Compression Type II (APC-II)

Correct Answer & Explanation

. Vertical Shear (VS)

Explanation

According to the Young-Burgess classification, Vertical Shear (VS) injuries are inherently unstable. They involve complete disruption of the posterior pelvic ring (sacroiliac joint or sacral fractures) and often the anterior ring as well, with vertical displacement. LC-I, APC-I, and APC-II are generally considered stable or rotationally unstable but vertically stable (APC-II has partial posterior disruption). LC-II involves posterior ligamentous disruption (sacrotuberous and sacrospinous ligaments) but the posterior arch may remain intact, making it rotationally unstable but not necessarily vertically unstable without further disruption.

Question 676

Topic: Pelvic & Acetabular Trauma
A 7-year-old boy with Legg-Calvรฉ-Perthes disease presents with a painful limp and limited abduction. Radiographs demonstrate hinge abduction. What is the primary pathomechanical consequence of persistent hinge abduction if left untreated?
. Premature closure of the triradiate cartilage
. Prevention of femoral head remodeling by the acetabulum
. Spontaneous fusion of the hip joint
. Avascular necrosis of the acetabulum
. Overgrowth of the greater trochanter leading to coxa valga

Correct Answer & Explanation

. Prevention of femoral head remodeling by the acetabulum

Explanation

Hinge abduction occurs when the extruded, enlarged anterolateral portion of the femoral head impinges on the lateral margin of the acetabulum during abduction. Persistent hinge abduction prevents the acetabulum from effectively remodeling the femoral head, leading to a permanently deformed, aspherical femoral head (coxa magna) and early osteoarthritis. It does not cause premature closure of the triradiate cartilage or avascular necrosis of the acetabulum.

Question 677

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the trauma bay following a motorcycle collision. He is hemodynamically unstable and radiographs reveal an Anteroposterior Compression (APC) type III pelvic ring injury. A pelvic binder is applied. Which of the following ligamentous structures provides the primary restraint to external rotation of the hemipelvis?
. Anterior sacroiliac ligament
. Sacrotuberous ligament
. Posterior sacroiliac ligament
. Iliolumbar ligament
. Sacrospinous ligament

Correct Answer & Explanation

. Anterior sacroiliac ligament

Explanation

The anterior sacroiliac ligament is the primary restraint to external rotation of the hemipelvis. In APC injuries, the symphysis fails first, followed by the sacrotuberous/sacrospinous ligaments, and finally the anterior sacroiliac ligament, causing profound external rotational instability.

Question 678

Topic: Pelvic & Acetabular Trauma

When performing the Barlow maneuver, what is the primary direction of force applied to the femoral head to test for instability?

. Anterior and superior
. Posterior and lateral
. Posterior and inferior
. Anterior and medial
. Posterior and superior

Correct Answer & Explanation

. Posterior and lateral

Explanation

In the Barlow maneuver, the hip is flexed and adducted, and a posterior (downward towards the table) and slightly lateral force is applied to the knee/thigh, attempting to dislocate the femoral head posteriorly out of the acetabulum. The Ortolani maneuver involves anterior and superior force to reduce a dislocated hip.

Question 679

Topic: Pelvic & Acetabular Trauma

Which radiographic line or angle is primarily used to assess acetabular depth and coverage of the femoral head in children over 4-6 months of age?

. Shenton's line
. Perkin's line
. Hilgenreiner's line
. Acetabular index (angle)
. Wiberg's CE angle

Correct Answer & Explanation

. Acetabular index (angle)

Explanation

The acetabular index (or acetabular angle) is formed by a line drawn from the triradiate cartilage to the lateral edge of the acetabular roof and Hilgenreiner's line (a horizontal line connecting the inferior margins of the triradiate cartilages). An increased acetabular index indicates a shallow, dysplastic acetabulum. Hilgenreiner's line and Perkin's line (perpendicular to Hilgenreiner's, drawn from the lateral edge of the acetabulum) create quadrants for assessing femoral head position. Shenton's line assesses the alignment of the medial femoral neck and superior obturator foramen. Wiberg's CE angle (center-edge angle) is used in older children and adults to assess lateral femoral head coverage, not typically in infants for initial dysplasia assessment.

Question 680

Topic: Pelvic & Acetabular Trauma

A 6-month-old infant is diagnosed with a dislocated hip. What is the key advantage of obtaining an AP pelvis radiograph over a hip ultrasound at this age?

. Better visualization of soft tissue structures like the labrum.
. No exposure to ionizing radiation.
. More accurate assessment of the ossified femoral head and acetabular bony morphology.
. Dynamic assessment of hip stability.
. Superior for detecting early avascular necrosis.

Correct Answer & Explanation

. More accurate assessment of the ossified femoral head and acetabular bony morphology.

Explanation

By 6 months of age, the ossific nucleus of the femoral head and bony acetabular margins are sufficiently developed to be visualized and accurately assessed on plain radiographs. Ultrasound becomes less effective due to ossification shadowing. Radiographs provide a more accurate assessment of bony morphology (e.g., acetabular index, position of the femoral head relative to the acetabulum). Ultrasound is better for soft tissues and dynamic assessment in younger infants, and CT/MRI are better for AVN.

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