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Pelvic & Acetabular Trauma MCQs

Practice Set 14 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 261

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the trauma bay following a high-speed motorcycle collision. A pelvic binder was placed in the field. Anteroposterior (AP) pelvis radiograph reveals an anterior-posterior compression (APC) injury. His pubic symphysis is widened by 3.5 cm, but the posterior pelvic ring appears grossly intact on initial imaging. In an APC-II pelvic ring injury, which of the following ligamentous structures remains intact?
. Anterior sacroiliac ligament
. Sacrospinous ligament
. Sacrotuberous ligament
. Posterior sacroiliac ligament
. Pubic symphyseal ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligament

Explanation

According to the Young-Burgess classification, an APC-II injury is characterized by rupture of the pubic symphysis, anterior sacroiliac ligaments, sacrospinous ligaments, and sacrotuberous ligaments, resulting in an 'open book' pelvis. The posterior sacroiliac ligaments remain intact, providing vertical stability but allowing rotational instability. Rupture of the posterior sacroiliac ligaments would result in an APC-III injury, which is completely unstable both rotationally and vertically.

Question 262

Topic: Pelvic & Acetabular Trauma
A 45-year-old male is brought to the ED after a motorcycle crash. His pelvis is unstable. Radiographs show symphyseal diastasis of 3.5 cm and widening of the anterior sacroiliac joints, but the posterior SI ligaments remain intact. According to the Young-Burgess classification, what type of injury is this?
. APC I
. APC II
. APC III
. LC I
. LC II

Correct Answer & Explanation

. APC II

Explanation

Anterior-Posterior Compression (APC) injuries: APC I is symphysis widening < 2.5 cm with intact posterior ligaments. APC II is symphysis widening > 2.5 cm, torn anterior SI, sacrotuberous, and sacrospinous ligaments, but INTACT posterior SI ligaments (rotationally unstable, vertically stable). APC III involves disruption of both anterior and posterior SI ligaments (rotationally and vertically unstable).

Question 263

Topic: Pelvic & Acetabular Trauma
In an anteroposterior compression (APC) type III pelvic ring injury, the symphysis pubis is widely disrupted, and the hemipelvis is completely unstable. Which of the following posterior ligamentous structures is completely disrupted in an APC III injury but intact in an APC II injury?
. Anterior sacroiliac ligaments
. Sacrospinous ligaments
. Sacrotuberous ligaments
. Posterior sacroiliac ligaments
. Iliolumbar ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

APC II injuries involve disruption of the symphysis pubis, anterior sacroiliac ligaments, and the sacrospinous and sacrotuberous ligaments, but the posterior sacroiliac ligaments remain intact (opening book). In APC III, there is complete disruption of the anterior and posterior sacroiliac ligaments, leading to a completely unstable hemipelvis.

Question 264

Topic: Pelvic & Acetabular Trauma
A 35-year-old male sustains an APC-III pelvic ring injury following a high-speed motorcycle collision. After initial hemodynamic stabilization, the surgeon elects to perform an open reduction and internal fixation of a widened sacroiliac (SI) joint via an anterior approach. During dissection and plate placement over the sacral ala, which neurological structure is at greatest risk of iatrogenic injury?
. L3 nerve root
. L4 nerve root
. L5 nerve root
. S1 nerve root
. Sciatic nerve

Correct Answer & Explanation

. L5 nerve root

Explanation

During the anterior approach to the sacroiliac joint, the L5 nerve root is at significant risk. It courses directly over the sacral ala, typically approximately 2 cm medial to the SI joint, before joining the sacral plexus. Retraction or misplaced drills/screws in this region can easily injure the L5 root, leading to foot drop and sensory deficits.

Question 265

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is involved in a high-speed motor vehicle collision and sustains the pelvic ring injury shown below. In an Anteroposterior Compression Type III (APC-III) injury, which ligamentous complex is completely disrupted resulting in global pelvic instability?
. Anterior sacroiliac ligaments only
. Anterior sacroiliac and sacrospinous ligaments only
. Anterior sacroiliac, sacrospinous, sacrotuberous, and posterior sacroiliac ligaments
. Sacrotuberous ligaments only
. Iliolumbar ligaments only

Correct Answer & Explanation

. Anterior sacroiliac, sacrospinous, sacrotuberous, and posterior sacroiliac ligaments

Explanation

An APC-III injury represents a complete disruption of both the anterior and posterior pelvic rings. The symphysis is widened, and there is complete disruption of the anterior sacroiliac (SI), sacrospinous, sacrotuberous, and posterior SI ligaments. This results in global instability (both rotational and vertical). APC-II injuries typically spare the posterior SI ligaments.

Question 266

Topic: Pelvic & Acetabular Trauma

A 22-year-old collegiate hockey player presents with chronic groin pain exacerbated by hip flexion, adduction, and internal rotation. Imaging demonstrates a lack of femoral head-neck offset, presenting as a 'pistol grip' deformity. This Cam-type impingement primarily damages which structure initially?

. Ligamentum teres
. Acetabular labrum at the posteroinferior quadrant
. Articular cartilage of the anterosuperior acetabulum via shear forces
. Femoral head articular cartilage via direct impaction
. Iliopsoas tendon at the pelvic brim

Correct Answer & Explanation

. Articular cartilage of the anterosuperior acetabulum via shear forces

Explanation

Cam impingement (aspherical femoral head/reduced offset) forces a non-spherical portion of the femoral head into the acetabulum during flexion. This primarily causes outside-in shear forces, leading to delamination of the anterosuperior acetabular articular cartilage, often with secondary separation of the adjacent labrum. Pincer impingement, conversely, causes direct linear compression of the labrum.

Question 267

Topic: Pelvic & Acetabular Trauma
A 45-year-old male presents after a motorcycle collision with a radiographically confirmed anteroposterior compression type II (APC II) pelvic ring injury. Which of the following ligamentous structures is typically intact in this specific injury pattern?
. Symphyseal ligaments
. Anterior sacroiliac ligaments
. Sacrospinous ligaments
. Sacrotuberous ligaments
. Posterior sacroiliac ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

In the Young-Burgess classification, an APC II pelvic ring injury involves diastasis of the pubic symphysis (rupture of symphyseal ligaments) and 'opening of the book' at the SI joint. This mechanism ruptures the anterior sacroiliac, sacrospinous, and sacrotuberous ligaments. However, the stout posterior sacroiliac ligaments remain intact, acting as a hinge. Complete disruption of the posterior SI ligaments would convert this to a completely unstable APC III injury.

Question 268

Topic: Pelvic & Acetabular Trauma

A 45-year-old patient is brought to the emergency department after a high-speed motor vehicle collision. He is hypotensive (BP 80/50 mmHg) and tachycardic (HR 125 bpm). Physical examination reveals a swollen and unstable pelvis. A bedside AP pelvis radiograph is obtained and is shown below.

The radiograph shows a significantly displaced open-book pelvic injury with widening of the pubic symphysis and disruption of the posterior sacroiliac ligaments. After initial ATLS resuscitation, what is the MOST immediate and critical orthopedic intervention to manage ongoing hemorrhage?

. Diagnostic peritoneal lavage.
. Laparotomy for abdominal exploration.
. Application of a pelvic binder or external fixator.
. Emergent angiography and embolization.
. CT scan of the abdomen and pelvis.

Correct Answer & Explanation

. Application of a pelvic binder or external fixator.

Explanation

In a hemodynamically unstable patient with an unstable pelvic ring injury, the MOST immediate and critical orthopedic intervention for hemorrhage control is the application of a pelvic binder or external fixator. This maneuver reduces the volume of the pelvic cavity, tamponading venous bleeding and promoting clot formation. While angiography and embolization are crucial for arterial bleeding, and laparotomy may be needed for intra-abdominal organ injury, pelvic compression provides rapid initial stabilization for the majority of pelvic hemorrhage (which is often venous). A CT scan is usually performed after hemodynamic stabilization.

Question 269

Topic: Pelvic & Acetabular Trauma

A 40-year-old female presents with a 6-month history of chronic, dull ache in her right buttock, with occasional radiation to the posterior thigh, but not below the knee. The pain is exacerbated by prolonged standing, sitting, or weight-bearing on the affected side. Physical examination reveals tenderness over the right sacroiliac joint and positive distraction, compression, and FABER tests. Lumbar MRI is unremarkable. What is the MOST appropriate next step in confirming the diagnosis and guiding treatment for suspected sacroiliac joint dysfunction?

. Prescription of oral corticosteroids.
. Electromyography (EMG) and nerve conduction studies (NCS) of the lower extremity.
. Diagnostic injection of local anesthetic into the sacroiliac joint.
. Lumbar epidural steroid injection.
. Referral for psychiatric evaluation due to chronic pain.

Correct Answer & Explanation

. Diagnostic injection of local anesthetic into the sacroiliac joint.

Explanation

When lumbar pathology has been ruled out, a diagnostic injection of local anesthetic (with or without corticosteroid) directly into the sacroiliac joint is considered the gold standard for confirming sacroiliac joint dysfunction. Significant (e.g., >50%) transient relief of symptoms immediately following the injection strongly supports the diagnosis. EMG/NCS are useful for radiculopathy but less specific for SI joint pain. Lumbar epidural steroid injection targets lumbar radicular pain. Oral corticosteroids provide systemic relief but are not diagnostic. Psychiatric evaluation is premature without a confirmed diagnosis.

Question 270

Topic: Pelvic & Acetabular Trauma
Which of the following anatomical landmarks is the correct target for the optimal placement of a circumferential pelvic sheet or binder to reduce an open book pelvic ring injury in the trauma bay?
. Iliac crests
. Greater trochanters
. Anterior superior iliac spines
. Pubic symphysis

Correct Answer & Explanation

. Greater trochanters

Explanation

To effectively reduce an open book pelvic injury, the pelvic binder must be placed at the level of the greater trochanters. Placing it higher, over the iliac crests or ASIS, is ineffective and can potentially worsen the injury.

Question 271

Topic: Pelvic & Acetabular Trauma

In the surgical management of developmental dysplasia of the hip (DDH), various pelvic osteotomies can be utilized to improve coverage.

Which of the following best describes the biomechanical principle of a Pemberton osteotomy?

. It is a complete redirectional osteotomy hinging at the pubic symphysis that does not change the true volume of the acetabulum.
. It is an incomplete osteotomy hinging at the triradiate cartilage that decreases the volume of the acetabulum.
. It is a triple innominate osteotomy that allows for medialization of the joint center.
. It is a salvage capsular arthroplasty that relies on metaplasia of the joint capsule.
. It is a completely intra-articular redirectional osteotomy.

Correct Answer & Explanation

. It is an incomplete osteotomy hinging at the triradiate cartilage that decreases the volume of the acetabulum.

Explanation

A Pemberton osteotomy is an incomplete trans-iliac osteotomy that hinges on the flexible, open triradiate cartilage (the ilioischial and iliopubic limbs). Because it hinges at the triradiate cartilage and folds down the acetabular roof, it inherently decreases the overall volume of the acetabulum. In contrast, the Salter innominate osteotomy is a complete cut through the ilium hinging at the pubic symphysis, altering the direction but not the volume of the acetabulum.

Question 272

Topic: Pelvic & Acetabular Trauma

A 25-year-old male is brought to the trauma bay after a motorcycle accident. He has an open-book pelvic ring injury with hemodynamic instability. To effectively close the pelvic volume, a circumferential pelvic sheet or binder should be placed at the level of the:

. Anterior superior iliac spines
. Iliac crests
. Greater trochanters
. Lesser trochanters
. Symphysis pubis

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder must be placed centered over the greater trochanters to effectively provide compression across the pelvic ring and reduce pelvic volume. Placement over the iliac crests is incorrect and can exacerbate the deformity or cause inadequate compression.

Question 273

Topic: Pelvic & Acetabular Trauma
A 40-year-old male is brought to the trauma bay following a crush injury. He is hemodynamically unstable. Pelvic radiographs demonstrate an anteroposterior compression (APC) type III injury with a widely open symphysis pubis. Where is the optimal anatomical placement of a circumferential pelvic sheet or binder to reduce pelvic volume?
. Over the iliac crests
. Centered over the greater trochanters
. Between the umbilicus and the anterior superior iliac spines
. Directly over the lower lumbar spine
. At the level of the proximal femoral diaphysis

Correct Answer & Explanation

. Centered over the greater trochanters

Explanation

A pelvic binder must be centered over the greater trochanters to generate the appropriate force vector to close an open-book pelvic ring injury effectively. Placement over the iliac crests is incorrect and can exacerbate the deformity.

Question 274

Topic: Pelvic & Acetabular Trauma
A 25-year-old male is brought to the trauma bay hemodynamically unstable following a motorcycle collision. Pelvic radiograph reveals an APC-III pelvic ring injury. Despite application of a pelvic binder and initial fluid resuscitation, he remains hypotensive. What is the most common anatomical source of hemorrhage in this specific injury pattern?
. Superior gluteal artery
. Presacral venous plexus
. Corona mortis
. Internal pudendal artery
. External iliac artery

Correct Answer & Explanation

. Presacral venous plexus

Explanation

Up to 80-90% of bleeding in pelvic ring injuries originates from the low-pressure presacral venous plexus and cancellous bone edges. Arterial bleeding is less common but may require angioembolization if venous sources are controlled and the patient remains unstable.

Question 275

Topic: Pelvic & Acetabular Trauma
A 45-year-old male is brought to the ED after a motorcycle crash. He is hypotensive with a mechanically unstable pelvis (APC type III). A pelvic binder is applied. Where is the optimal anatomical position for the pelvic binder to maximize reduction and minimize complications?
. Over the iliac crests
. Centered over the greater trochanters
. At the level of the anterior superior iliac spines
. Just proximal to the pubic symphysis
. Over the lower lumbar spine and sacrum

Correct Answer & Explanation

. Centered over the greater trochanters

Explanation

To effectively close the pelvic ring and control hemorrhage, a pelvic binder must be placed at the level of the greater trochanters. Placement over the iliac crests is ineffective and can paradoxically open the pelvis further in some fracture patterns.

Question 276

Topic: Pelvic & Acetabular Trauma
A 42-year-old male is brought to the trauma bay after a motorcycle collision. He is hemodynamically unstable with a heart rate of 120 bpm and BP of 80/50 mmHg. Pelvic radiograph reveals an APC-III pelvic ring injury. A pelvic binder is applied. To maximize reduction of the symphysis pubis and control hemorrhage, at what anatomic level should the pelvic binder be centered?
. Anterior superior iliac spines
. Greater trochanters
. Iliac crests
. Pubic symphysis directly
. Umbilicus

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders must be centered over the greater trochanters to effectively close an open-book pelvic ring injury. Placement over the iliac crests is incorrect and can cause paradoxical opening of the pelvic ring, worsening the hemorrhage.

Question 277

Topic: Pelvic & Acetabular Trauma
A 35-year-old male presents with a hypotensive APC-III pelvic ring disruption following a severe crush injury. Despite initial massive transfusion protocols and appropriate application of a pelvic binder, he remains hemodynamically unstable. What is the most common anatomical source of massive hemorrhage in this specific fracture pattern?
. Superior gluteal artery
. Internal pudendal artery
. Presacral venous plexus
. External iliac vein
. Corona mortis

Correct Answer & Explanation

. Presacral venous plexus

Explanation

The presacral venous plexus and disrupted cancellous bone edges are the most common sources of bleeding in severe pelvic ring injuries, accounting for up to 80-90% of bleeding volume. While arterial bleeding (e.g., superior gluteal artery) is life-threatening and treated with embolization, it is less frequent overall.

Question 278

Topic: Pelvic & Acetabular Trauma
A hemodynamically unstable 35-year-old male arrives in the trauma bay after a motorcycle collision. Radiographs show an Anteroposterior Compression (APC) Type III pelvic ring injury. A pelvic binder has been applied but he remains hypotensive despite aggressive fluid resuscitation. FAST scan is negative. What is the most appropriate next step?
. CT abdomen and pelvis with IV contrast
. Application of an external fixator and transfer to ICU
. Preperitoneal pelvic packing and/or angioembolization
. Exploratory laparotomy with bowel run
. Administration of tranexamic acid and wait for response

Correct Answer & Explanation

. Preperitoneal pelvic packing and/or angioembolization

Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury and negative FAST, retroperitoneal hemorrhage is the most likely cause. Preperitoneal pelvic packing and angioembolization are the primary life-saving interventions to control this bleeding.

Question 279

Topic: Pelvic & Acetabular Trauma

The articular cartilage in a healthy synovial joint is primarily a type of:

. Elastic cartilage
. Fibrocartilage
. Hyaline cartilage
. Calcified cartilage
. Reticular cartilage

Correct Answer & Explanation

. Hyaline cartilage

Explanation

Articular cartilage, which covers the ends of bones in synovial joints, is a specialized form of hyaline cartilage. Hyaline cartilage is characterized by a matrix rich in Type II collagen and aggrecan, providing a smooth, resilient, and low-friction surface crucial for joint movement. It lacks blood vessels, nerves, and lymphatic vessels, relying on synovial fluid for nutrition. Fibrocartilage, found in menisci, intervertebral discs, and pubic symphysis, has a higher proportion of Type I collagen and is more resistant to tensile forces. Elastic cartilage is found in the ear and epiglottis.

Question 280

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the trauma bay with an anteroposterior compression (APC-III) pelvic ring injury. Despite application of a pelvic binder, 2L of crystalloid, and 2 units of uncrossmatched blood, his blood pressure remains 80/50 mmHg. A FAST exam is negative. What is the most appropriate next step?
. CT scan of the abdomen and pelvis
. Pelvic packing or immediate angiography
. Exploratory laparotomy
. Definitive anterior and posterior pelvic fixation
. Removal of the pelvic binder to assess for REBOA placement

Correct Answer & Explanation

. Pelvic packing or immediate angiography

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST exam, retroperitoneal venous or arterial bleeding is the primary culprit. Preperitoneal pelvic packing or angiography is the most appropriate next step to achieve hemostasis.

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