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Pelvic & Acetabular Trauma MCQs

Practice Set 31 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 601

Topic: Pelvic & Acetabular Trauma
A 40-year-old patient is involved in an MVC and sustains an anteroposterior compression type III (APC-III) pelvic ring injury. In the trauma bay, the patient is hypotensive and tachycardic. A pelvic binder is applied. What is the correct anatomical landmark for the placement of the pelvic binder to effectively reduce pelvic volume?
. Over the iliac crests
. Over the greater trochanters
. Over the anterior superior iliac spines
. Just proximal to the umbilicus
. Around the mid-thighs

Correct Answer & Explanation

. Over the greater trochanters

Explanation

Pelvic binders must be centered over the greater trochanters (at the level of the symphysis pubis) to effectively compress the pelvic ring, internally rotate the hemi-pelves, and reduce the intrapelvic volume. Placement over the iliac crests is a common error and can worsen the rotational deformity.

Question 602

Topic: Pelvic & Acetabular Trauma

A 45-year-old motorcyclist sustains a closed pelvic ring injury. Clinically, there is a large, fluctuant swelling over the greater trochanter with ecchymosis. Aspiration yields serosanguinous fluid. What is the most appropriate initial management of this specific soft tissue lesion?

. Immediate wide surgical excision
. Intravenous antibiotics alone
. Percutaneous drainage and compression
. Observation with no intervention
. Immediate open reduction and internal fixation through the lesion

Correct Answer & Explanation

. Immediate wide surgical excision

Explanation

The patient has a Morel-Lavallee lesion, a closed degloving injury where skin and subcutaneous fat are separated from the underlying fascia. Initial management of acute lesions often involves percutaneous drainage and firm compression to obliterate the dead space and prevent pseudocyst formation.

Question 603

Topic: Pelvic & Acetabular Trauma
According to the Young-Burgess classification, an Anteroposterior Compression Type II (APC-II) pelvic ring injury is characterized by rupture of the anterior sacroiliac ligaments while maintaining the integrity of which specific posterior structures?
. Sacrotuberous ligaments
. Sacrospinous ligaments
. Posterior sacroiliac ligaments
. Symphysis pubis
. Iliolumbar ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

An APC-II injury involves pubic symphyseal diastasis and rupture of the anterior sacroiliac ligaments, sacrotuberous, and sacrospinous ligaments. The strong posterior sacroiliac ligaments remain intact, providing vertical stability but resulting in rotational instability ('open book' pelvis). An APC-III injury involves disruption of both anterior and posterior SI ligaments, resulting in both rotational and vertical instability.

Question 604

Topic: Pelvic & Acetabular Trauma
A 28-year-old male arrives in hemorrhagic shock after a motorcycle accident. Radiographs reveal an AP compression type III (APC-III) pelvic ring injury. To be maximally effective in reducing pelvic volume, where should a pelvic binder be centered?
. Over the iliac crests
. Over the greater trochanters
. Over the umbilicus
. Over the proximal femurs below the lesser trochanter
. Over the mid-lumbar spine

Correct Answer & Explanation

. Over the greater trochanters

Explanation

Pelvic binders are most effective at reducing pelvic volume and controlling hemorrhage when centered precisely over the greater trochanters. Placement over the iliac crests is less effective and may exacerbate certain fracture patterns.

Question 605

Topic: Pelvic & Acetabular Trauma
A 50-year-old male presents with a pelvic ring injury and a large, fluctuant soft-tissue swelling over the greater trochanter. Aspiration yields serosanguinous fluid containing fat globules. What is the pathophysiologic mechanism of this specific lesion?
. Bacterial inoculation of a superficial hematoma
. Arterial pseudoaneurysm formation from the superior gluteal artery
. Closed degloving injury separating subcutaneous tissue from the underlying deep fascia
. Herniation of muscle tissue through a traumatic fascial defect
. Rupture of the trochanteric bursa due to direct impact

Correct Answer & Explanation

. Closed degloving injury separating subcutaneous tissue from the underlying deep fascia

Explanation

A Morel-Lavallée lesion is a closed degloving injury where the subcutaneous tissue is separated from the underlying deep fascia. This disrupts perforating vessels, leading to the accumulation of blood, lymph, and necrotic fat.

Question 606

Topic: Pelvic & Acetabular Trauma
A 24-year-old male is brought to the trauma bay following a motorcycle collision. He is hypotensive with a systolic blood pressure of 75 mmHg. Pelvic radiograph shows an APC-III pelvic ring injury. A pelvic binder is applied, and he receives 2 units of packed red blood cells, but his hemodynamics do not improve. FAST scan is negative. What is the most appropriate next step in management?
. Application of an external fixator
. Exploratory laparotomy
. Preperitoneal pelvic packing or angiography
. Administration of tranexamic acid and wait 1 hour
. Transfer for definitive open reduction and internal fixation

Correct Answer & Explanation

. Preperitoneal pelvic packing or angiography

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST scan, the source of bleeding is presumed to be the pelvis. The next appropriate step is preperitoneal pelvic packing or pelvic angiography for embolization.

Question 607

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the emergency department after a high-speed motor vehicle collision. He is hemodynamically unstable with a suspected anterior-posterior compression (APC) type III pelvic ring injury. When applying a non-invasive pelvic circumferential compression device (pelvic binder), at what anatomical level should it be centered for maximum efficacy?
. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Symphysis pubis directly
. Sacral promontory

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder must be centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement higher over the iliac crests is less effective and may paradoxically open the true pelvis in certain fracture patterns.

Question 608

Topic: Pelvic & Acetabular Trauma

According to the Young-Burgess classification, an anteroposterior compression (APC) type II pelvic ring injury is characterized by rupture of the anterior sacroiliac ligaments. What is the classic radiographic appearance of the pubic symphysis in this specific injury pattern?

. Diastasis less than 2.5 cm
. Diastasis greater than 2.5 cm
. Vertical displacement of the hemipelvis
. Overlapping of the pubic symphysis
. Normal symphysis width with bilateral rami fractures

Correct Answer & Explanation

. Diastasis less than 2.5 cm

Explanation

In an APC II injury, the pubic symphysis diastasis is typically greater than 2.5 cm. This represents disruption of the symphyseal ligaments as well as the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. The robust posterior sacroiliac ligaments remain intact, leading to an externally rotated ('open book') but vertically stable pelvis.

Question 609

Topic: Pelvic & Acetabular Trauma
In the management of pelvic ring injuries, the primary structural distinction between an Anteroposterior Compression (APC) Type II and Type III injury according to the Young-Burgess classification is the complete disruption of which of the following?
. Symphysis pubis
. Anterior sacroiliac ligaments
. Sacrospinous ligaments
. Sacrotuberous ligaments
. Posterior sacroiliac ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

An APC II injury involves symphyseal diastasis and disruption of the anterior sacroiliac (SI), sacrospinous, and sacrotuberous ligaments, but the posterior SI ligaments remain intact (providing vertical stability despite rotational instability). An APC III injury involves disruption of both anterior and posterior SI ligaments, resulting in complete spinopelvic dissociation with both rotational and vertical instability.

Question 610

Topic: Pelvic & Acetabular Trauma

A 2-year-old girl is diagnosed with late-presenting unilateral Developmental Dysplasia of the Hip (DDH). During open reduction, a Salter osteotomy is performed. Through which structural hinge does the distal fragment rotate to improve anterior and lateral coverage?

. Sacroiliac joint
. Triradiate cartilage
. Pubic symphysis
. Ischial tuberosity
. Acetabular roof

Correct Answer & Explanation

. Sacroiliac joint

Explanation

The Salter innominate osteotomy is an incomplete, directional transiliac osteotomy that hinges on a flexible pubic symphysis. It redirects the entire acetabulum to improve anterolateral coverage of the femoral head without changing acetabular volume.

Question 611

Topic: Pelvic & Acetabular Trauma
The Bernese periacetabular osteotomy (PAO) is an essential joint-preserving procedure for symptomatic acetabular dysplasia. Which of the following bony structures of the pelvis is intentionally left intact during a standard PAO to maintain the stability of the pelvic ring?
. Anterior column
. Pubic ramus
. Posterior column
. Ischium
. Ilium (supra-acetabular portion)

Correct Answer & Explanation

. Posterior column

Explanation

The Bernese PAO consists of a series of specific bone cuts: an incomplete ischial osteotomy, a complete pubic ramus osteotomy, and a complete supra-acetabular iliac osteotomy (anterior column). The posterior column of the ilium/ischium is intentionally left intact, which preserves the structural continuity of the pelvic ring and allows for immediate postoperative mobilization.

Question 612

Topic: Pelvic & Acetabular Trauma
A trauma patient arrives with a hemodynamically unstable pelvic ring injury (APC III). A pelvic binder is applied in the emergency department. To effectively close the pelvic ring and reduce pelvic volume, the binder must be centered precisely over which anatomical landmark?
. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis
. Umbilicus

Correct Answer & Explanation

. Greater trochanters

Explanation

For a pelvic binder to effectively reduce pelvic volume and stabilize the bony pelvis, it must be centered over the greater trochanters. Placement higher over the iliac crests can paradoxically open the pelvic ring further.

Question 613

Topic: Pelvic & Acetabular Trauma

A 68-year-old male with type 2 diabetes presents with neck stiffness. Radiographs show flowing ossification along the anterolateral aspect of five contiguous cervical and thoracic vertebrae. Disc heights are preserved, and there is no evidence of sacroiliac joint ankylosis. Which of the following is true regarding this patient's condition?

. The patient will almost certainly test positive for HLA-B27
. The condition is primarily mediated by autoimmune inflammation of the entheses
. It is defined by Resnick criteria, which includes flowing ossification of at least 4 contiguous vertebrae
. Treatment requires aggressive immunosuppression to halt progression
. The disease typically destroys the intervertebral discs leading to spontaneous fusions

Correct Answer & Explanation

. It is defined by Resnick criteria, which includes flowing ossification of at least 4 contiguous vertebrae

Explanation

The clinical picture describes Diffuse Idiopathic Skeletal Hyperostosis (DISH). The classic Resnick and Niwayama criteria for DISH include: 1. Flowing ossification along the anterolateral aspect of at least 4 contiguous vertebrae. 2. Preservation of intervertebral disc height. 3. Absence of apophyseal joint bony ankylosis or sacroiliac joint erosion/sclerosis. Unlike Ankylosing Spondylitis, DISH is not associated with HLA-B27, lacks SI joint involvement, does not erode discs, and does not respond to immunosuppressants.

Question 614

Topic: Pelvic & Acetabular Trauma

A 25-year-old male is brought to the trauma bay after a crush injury with a mechanically unstable pelvis and hypotension. A decision is made to place a circumferential pelvic sheet or binder. What is the correct anatomical landmark for centering the binder?

. Iliac crests
. Greater trochanters
. Pubic symphysis
. Anterior superior iliac spines
. Subtrochanteric line

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders must be centered over the greater trochanters to effectively reduce the pelvic volume. Placement over the iliac crests can paradoxically open the pelvis further, worsening an unstable open-book injury.

Question 615

Topic: Pelvic & Acetabular Trauma
A 35-year-old male presents after a motorcycle collision with a blood pressure of 80/50 mmHg. A pelvic binder is applied, and FAST exam is negative. Pelvic radiograph demonstrates an APC III pelvic ring injury. Despite the binder and fluid resuscitation, his blood pressure remains 75/40 mmHg. What is the most appropriate next step in management?
. Retrograde urethrogram
. Preperitoneal pelvic packing
. Emergent open reduction internal fixation of the pelvis
. Exploratory laparotomy
. Application of bilateral chest tubes

Correct Answer & Explanation

. Preperitoneal pelvic packing

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST exam, bleeding is likely retroperitoneal. Preperitoneal pelvic packing or pelvic angiography is indicated after a pelvic binder has failed to achieve hemodynamic stability.

Question 616

Topic: Pelvic & Acetabular Trauma
A 40-year-old male presents in hemorrhagic shock after a motorcycle crash. Pelvic radiographs show an anteroposterior compression type III (APC-III) pelvic ring injury. A FAST scan is negative. Despite application of a pelvic binder and massive transfusion protocol, his blood pressure remains 75/40 mm Hg. What is the most appropriate next step in management?
. CT scan of the abdomen and pelvis
. Application of a pelvic C-clamp
. Retrograde urethrogram
. Preperitoneal pelvic packing or angiography
. Exploratory laparotomy

Correct Answer & Explanation

. Preperitoneal pelvic packing or angiography

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and negative FAST, the source of bleeding is likely pelvic venous plexus or arterial injury. Preperitoneal pelvic packing or pelvic angiography are the appropriate interventions.

Question 617

Topic: Pelvic & Acetabular Trauma

A 40-year-old male is evaluated for an acetabular fracture. An iliac oblique Judet radiograph is obtained. Which primary structures are best profiled on this specific radiographic view?

. Anterior column and posterior wall
. Posterior column and anterior wall
. Iliac wing and obturator ring
. Superior pubic ramus and ischial spine
. Ischial tuberosity and symphysis pubis

Correct Answer & Explanation

. Posterior column and anterior wall

Explanation

The Judet views are standard for evaluating acetabular fractures. The iliac oblique view best profiles the posterior column and the anterior wall of the acetabulum, while the obturator oblique view profiles the anterior column and posterior wall.

Question 618

Topic: Pelvic & Acetabular Trauma

A 25-year-old male sustains a posterior hip dislocation. After successful closed reduction, what is the most important imaging study to obtain and why?

. MRI of the hip to assess labral tears.
. CT scan of the hip to rule out incarcerated fragments and evaluate concentric reduction.
. Repeat plain radiographs to confirm reduction.
. Angiography to rule out femoral artery injury.
. Bone scan to assess for avascular necrosis (AVN) of the femoral head.

Correct Answer & Explanation

. CT scan of the hip to rule out incarcerated fragments and evaluate concentric reduction.

Explanation

After closed reduction of a posterior hip dislocation, a CT scan of the hip (B) is essential. It serves two critical purposes: 1) to confirm concentric reduction of the femoral head within the acetabulum, and 2) to rule out incarcerated intra-articular fragments (e.g., osteochondral fragments from the femoral head or acetabulum) that would necessitate open reduction. Failure to identify and remove such fragments significantly increases the risk of post-traumatic arthritis and loss of reduction. Repeat plain radiographs (C) are usually obtained immediately after reduction but are insufficient to rule out small incarcerated fragments. MRI (A) and angiography (D) are typically not the immediate next step, and bone scan (E) is for delayed complications like AVN.

Question 619

Topic: Pelvic & Acetabular Trauma

Which of the following physical examination findings is most suggestive of an unstable lateral compression (LC-II) pelvic ring injury?

. Sacral tenderness on palpation.
. Blood at the urethral meatus.
. Positive Faber test.
. Pain with internal rotation of the hip.
. Unilateral anterior superior iliac spine (ASIS) tenderness with rotational instability.

Correct Answer & Explanation

. Unilateral anterior superior iliac spine (ASIS) tenderness with rotational instability.

Explanation

A Young-Burgess Lateral Compression Type II (LC-II) pelvic ring injury is characterized by an internal rotation force causing an anterior injury (e.g., pubic rami fractures) and a posterior injury involving the ipsilateral sacroiliac joint or sacrum, often with a crescent fracture of the iliac wing. Rotational instability (E), often detected by gently compressing the iliac wings laterally (provocative stress test), is the key indicator of an unstable lateral compression injury. Sacral tenderness (A) is general for posterior injury. Blood at the urethral meatus (B) suggests urethral injury, which can be associated but isn't specific for LC-II mechanical instability. Faber test (C) is for hip pathology. Pain with internal rotation of the hip (D) is non-specific.

Question 620

Topic: Pelvic & Acetabular Trauma
A 30-year-old male presents to the emergency department after a high-speed motor vehicle accident. He is hemodynamically unstable, with a blood pressure of 80/40 mmHg and heart rate of 130 bpm. Pelvic X-ray shows a symphyseal diastasis of 5 cm and bilateral sacroiliac joint disruption. Which type of pelvic fracture does this best represent?
. Lateral Compression Type I (LC-I)
. Lateral Compression Type II (LC-II)
. Anterior-Posterior Compression Type I (APC-I)
. Anterior-Posterior Compression Type III (APC-III)
. Vertical Shear (VS)

Correct Answer & Explanation

. Anterior-Posterior Compression Type III (APC-III)

Explanation

This patient's injury pattern with symphyseal diastasis and bilateral sacroiliac joint disruption, combined with hemodynamic instability, is characteristic of an Anterior-Posterior Compression Type III (APC-III) pelvic fracture. This involves complete disruption of the posterior ligamentous complex (including sacrospinous, sacrotuberous, and anterior/posterior SI ligaments), leading to significant pelvic instability and a high risk of life-threatening hemorrhage. APC-I has symphyseal widening but intact posterior ligaments. LC types involve lateral compression with different degrees of rotation. Vertical Shear involves vertical displacement with complete disruption.

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