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Pelvic & Acetabular Trauma MCQs

Practice Set 16 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 301

Topic: Pelvic & Acetabular Trauma

In the setting of a severe vertical shear (VS) pelvic ring disruption with profound hemodynamic instability, life-threatening arterial hemorrhage from the posterior pelvic elements is most commonly due to injury of which of the following vessels?

. Obturator artery
. Superior gluteal artery
. Internal pudendal artery
. External iliac artery
. Inferior epigastric artery

Correct Answer & Explanation

. Superior gluteal artery

Explanation

Vertical shear (VS) pelvic ring injuries involve massive disruption of the posterior sacroiliac complex. Due to its intimate anatomic relationship with the upper border of the greater sciatic notch and the sacroiliac joint, the superior gluteal artery (the largest branch of the posterior division of the internal iliac artery) is highly vulnerable to laceration or avulsion in posterior disruption patterns. Anterior ring disruptions (like APC injuries) are more commonly associated with bleeding from the obturator or internal pudendal vessels.

Question 302

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 303

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 304

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 305

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 306

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 307

Topic: Pelvic & Acetabular Trauma
In the Young-Burgess classification of pelvic ring injuries, which of the following specifically differentiates an Anteroposterior Compression (APC) Type III injury from an APC Type II injury?
. Disruption of the symphysis pubis
. Disruption of the sacrotuberous ligament
. Disruption of the sacrospinous ligament
. Disruption of the posterior sacroiliac ligament
. Disruption of the anterior sacroiliac ligament

Correct Answer & Explanation

. Disruption of the posterior sacroiliac ligament

Explanation

In the Young-Burgess classification, APC II injuries involve disruption of the symphysis pubis (or anterior ring) along with the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. The posterior sacroiliac ligaments remain intact, providing some rotational instability but maintaining vertical stability. In an APC III injury, the posterior sacroiliac ligaments are completely disrupted, resulting in both rotational and vertical instability (a completely unstable hemipelvis).

Question 308

Topic: Pelvic & Acetabular Trauma
During the acute trauma bay management of a hemodynamically unstable patient with an anteroposterior compression (APC) type III pelvic ring injury, a circumferential pelvic binder is applied. To achieve the maximal mechanical advantage for reducing pelvic volume, the binder must be centered exactly over which anatomical landmark?
. Iliac crests
. Anterior superior iliac spines (ASIS)
. Greater trochanters
. Level of the pubic symphysis
. Subtrochanteric femurs

Correct Answer & Explanation

. Greater trochanters

Explanation

To effectively close the pelvic ring and reduce pelvic volume in open-book type fractures, the pelvic binder or sheet must be centered directly over the greater trochanters. Placement higher over the iliac crests is a common error and can paradoxically open the true pelvis further or fail to reduce the pubic symphysis effectively.

Question 309

Topic: Pelvic & Acetabular Trauma
A 26-year-old male is brought to the emergency department after a motorcycle collision. Pelvic radiographs reveal an anteroposterior compression (APC) injury. Which of the following findings defines an APC III pelvic ring injury according to the Young-Burgess classification?
. Symphysis widening less than 2.5 cm with intact posterior ligaments
. Disruption of the anterior sacroiliac ligaments with intact posterior sacroiliac ligaments
. Complete disruption of the pubic symphysis and both the anterior and posterior sacroiliac ligaments
. Sacral fracture with an ipsilateral superior and inferior rami fracture
. A crescent fracture of the posterior ilium

Correct Answer & Explanation

. Complete disruption of the pubic symphysis and both the anterior and posterior sacroiliac ligaments

Explanation

In the Young-Burgess classification, APC injuries are divided by severity. APC I is symphyseal diastasis <2.5 cm. APC II is symphyseal diastasis >2.5 cm with disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but intact posterior sacroiliac ligaments. APC III involves complete disruption of both anterior and posterior sacroiliac ligaments, leading to a completely unstable hemipelvis.

Question 310

Topic: Pelvic & Acetabular Trauma

In an anteroposterior compression type II (APC II) pelvic ring injury, which of the following ligamentous structures is primarily disrupted to allow widening of the pubic symphysis greater than 2.5 cm, while vertical stability is maintained?

. Posterior sacroiliac ligament
. Sacrotuberous and sacrospinous ligaments
. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments
. Iliolumbar ligament
. Sacrospinous ligament only

Correct Answer & Explanation

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments

Explanation

An APC II pelvic ring injury is characterized by symphyseal diastasis > 2.5 cm and widening of the anterior SI joint. The anterior sacroiliac, sacrotuberous, and sacrospinous ligaments are torn, causing rotational instability. The strong posterior sacroiliac ligaments remain intact, which prevents vertical displacement and maintains vertical stability.

Question 311

Topic: Pelvic & Acetabular Trauma
A 45-year-old male sustains an anteroposterior compression (APC) type II pelvic ring injury. Based on the Young-Burgess classification, an APC II injury is characterized by disruption of the symphysis pubis and which of the following posterior structures?
. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments
. Posterior sacroiliac ligaments only
. Both anterior and posterior sacroiliac ligaments
. Iliolumbar ligaments only
. Complete disruption of the pelvic floor and all sacroiliac ligaments

Correct Answer & Explanation

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments

Explanation

In an APC II injury, the 'open book' mechanism causes widening of the symphysis pubis (>2.5 cm) and tearing of the anterior sacroiliac ligaments, as well as the sacrotuberous and sacrospinous ligaments. The strong posterior sacroiliac ligaments remain intact, leaving the pelvis rotationally unstable but vertically stable. Complete disruption involving the posterior SI ligaments defines an APC III injury.

Question 312

Topic: Pelvic & Acetabular Trauma

In an anteroposterior compression (APC) type II pelvic ring injury (Young-Burgess classification), which of the following ligaments are typically ruptured?

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments
. Posterior sacroiliac and iliolumbar ligaments
. Anterior sacroiliac and posterior sacroiliac ligaments
. Sacrotuberous, sacrospinous, and posterior sacroiliac ligaments
. Sacrospinous, anterior sacroiliac, and iliolumbar ligaments

Correct Answer & Explanation

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments

Explanation

APC II injuries involve a 'subluxed' sacroiliac joint characterized by rupture of the anterior sacroiliac ligament, as well as the sacrotuberous and sacrospinous ligaments. The posterior sacroiliac ligament complex remains intact, which maintains vertical stability despite rotational instability (open book pelvis).

Question 313

Topic: Pelvic & Acetabular Trauma
In a Young-Burgess APC-III (Anteroposterior Compression type III) pelvic ring injury, which of the following best describes the posterior ligamentous disruption compared to an APC-II injury?
. Disruption of anterior sacroiliac ligaments only.
. Disruption of anterior and posterior sacroiliac, sacrotuberous, and sacrospinous ligaments.
. Disruption of the sacrotuberous ligaments only.
. Disruption of the sacrospinous ligaments only.
. Complete avulsion of the iliolumbar ligament with an intact posterior SI complex.

Correct Answer & Explanation

. Disruption of anterior and posterior sacroiliac, sacrotuberous, and sacrospinous ligaments.

Explanation

An APC-II injury is characterized by symphyseal diastasis and disruption of the anterior sacroiliac (SI), sacrotuberous, and sacrospinous ligaments, but the posterior SI ligaments remain intact, providing rotational instability but vertical stability. An APC-III injury involves further energy, resulting in complete disruption of both anterior and posterior SI ligaments, as well as the sacrotuberous and sacrospinous ligaments, leading to both rotational and vertical instability.

Question 314

Topic: Pelvic & Acetabular Trauma
In the Young-Burgess classification of pelvic ring injuries, which of the following injury patterns is most strongly associated with massive retroperitoneal hemorrhage requiring urgent volume reduction with a pelvic binder?
. Lateral Compression Type I (LC-1)
. Anteroposterior Compression Type III (APC-3)
. Lateral Compression Type II (LC-2)
. Vertical Shear (VS)
. Anteroposterior Compression Type I (APC-1)

Correct Answer & Explanation

. Anteroposterior Compression Type III (APC-3)

Explanation

Anteroposterior Compression Type III (APC-3) injuries involve complete disruption of both the anterior and posterior pelvic ligaments (including the pubic symphysis, sacrospinous, sacrotuberous, and anterior/posterior sacroiliac ligaments). This creates an extreme 'open-book' pattern, leading to complete instability and the largest increase in pelvic volume. It is associated with the highest rate of catastrophic retroperitoneal venous and arterial hemorrhage.

Question 315

Topic: Pelvic & Acetabular Trauma

In the Graf ultrasound classification for developmental dysplasia of the hip (DDH) in an infant, the alpha angle is widely utilized to determine the severity of dysplasia. What anatomic feature does the alpha angle represent, and what is its generally accepted normal value?

. The cartilaginous roof of the acetabulum; greater than 55 degrees
. The bony roof of the acetabulum; greater than 60 degrees
. The cartilaginous roof of the acetabulum; less than 55 degrees
. The bony roof of the acetabulum; less than 60 degrees
. The fibrocartilaginous labrum; greater than 60 degrees

Correct Answer & Explanation

. The bony roof of the acetabulum; greater than 60 degrees

Explanation

In the Graf ultrasound evaluation of infantile hips, the alpha angle measures the concavity of the bony roof of the acetabulum (formed by the ilium). A normal alpha angle (Graf Type I) is greater than or equal to 60 degrees. The beta angle measures the cartilaginous roof and is normally less than 55 degrees.

Question 316

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the ED after a high-speed motorcycle crash. His blood pressure is 70/40 mmHg. Pelvic radiographs reveal an anteroposterior compression (APC) Type III pelvic ring injury with complete disruption of the symphysis and bilateral sacroiliac joints. A massive transfusion protocol is initiated. What is the most appropriate immediate orthopedic intervention?
. Immediate open reduction and internal fixation of the pubic symphysis
. Application of a pelvic binder centered over the iliac crests
. Application of a pelvic binder centered over the greater trochanters
. Retrograde urethrogram to assess for urologic injury
. Angiography for bilateral internal iliac artery embolization

Correct Answer & Explanation

. Application of a pelvic binder centered over the greater trochanters

Explanation

In a hemodynamically unstable patient with an open-book pelvic fracture, the immediate step is to mechanically reduce pelvic volume to tamponade venous bleeding. A pelvic binder or sheet must be applied accurately over the greater trochanters to effectively close the pelvic ring. Placement over the iliac crests is incorrect and can exacerbate the deformity.

Question 317

Topic: Pelvic & Acetabular Trauma
A 45-year-old male presents in hemorrhagic shock following a high-speed motorcycle accident. Anteroposterior pelvis radiograph demonstrates an Anteroposterior Compression Type III (APC-III) pelvic ring injury. A pelvic binder is applied, and a massive transfusion protocol is initiated. Despite these measures, his hemodynamics remain unstable. A FAST (Focused Assessment with Sonography for Trauma) exam is negative. What is the most appropriate next step in management?
. Exploratory laparotomy
. Preperitoneal pelvic packing and/or pelvic angiography
. Application of a supra-acetabular external fixator
. Open reduction and internal fixation of the pubic symphysis
. Computed tomography angiography of the abdomen and pelvis

Correct Answer & Explanation

. Preperitoneal pelvic packing and/or pelvic angiography

Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury and a negative FAST exam, the source of bleeding is predominantly retroperitoneal (venous plexus or arterial). The accepted standard algorithms recommend either preperitoneal pelvic packing or pelvic angiography/embolization. CT scan is contraindicated in a hemodynamically unstable patient. Laparotomy is indicated for intra-abdominal bleeding (positive FAST), but opening the retroperitoneum during laparotomy can release the tamponade effect and worsen pelvic bleeding.

Question 318

Topic: Pelvic & Acetabular Trauma
A 35-year-old cyclist falls and sustains a closed degloving injury over the greater trochanter. Two weeks later, a fluctuant swelling is present. Aspiration yields serosanguinous fluid. What is the pathophysiological hallmark of this lesion?
. Subperiosteal hematoma formation
. Separation of the skin and subcutaneous tissue from the underlying deep fascia
. Rupture of the vastus lateralis with intramuscular hematoma
. Herniation of muscle through a fascial defect
. Lymphatic disruption within the superficial dermal layer

Correct Answer & Explanation

. Separation of the skin and subcutaneous tissue from the underlying deep fascia

Explanation

A Morel-Lavallée lesion is a closed degloving injury caused by shearing forces that separate the skin and subcutaneous fat from the underlying deep fascia. This creates a potential space that fills with blood, lymph, and necrotic fat.

Question 319

Topic: Pelvic & Acetabular Trauma
A 32-year-old male is brought to the emergency department after a motorcycle collision. He is hemodynamically unstable. Pelvic radiographs demonstrate an anteroposterior compression type III (APC III) pelvic ring injury. After application of a pelvic binder and initial fluid resuscitation, his blood pressure remains 70/40 mmHg. What is the most appropriate next step in management?
. Immediate open reduction and internal fixation of the pubic symphysis
. Pelvic angiography and embolization
. Laparotomy and bilateral internal iliac artery ligation
. Preperitoneal/retroperitoneal pelvic packing
. Placement of a supra-acetabular external fixator and transfer to the ICU

Correct Answer & Explanation

. Preperitoneal/retroperitoneal pelvic packing

Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury who does not respond to initial resuscitation and pelvic binding, preperitoneal/retroperitoneal pelvic packing is the most rapid and effective intervention to control venous bleeding, which represents the source in 80-90% of pelvic hemorrhage. Angiography is indicated if arterial bleeding is confirmed (e.g., contrast blush on CT) or if instability persists after packing.

Question 320

Topic: Pelvic & Acetabular Trauma

In the Young-Burgess classification of pelvic ring injuries, an anteroposterior compression (APC) Type II injury is characterized by the rupture of which ligaments?

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments with an intact posterior sacroiliac ligament
. Anterior and posterior sacroiliac ligaments
. Sacrotuberous ligament only
. Posterior sacroiliac ligament only
. Iliolumbar ligament only

Correct Answer & Explanation

. Anterior sacroiliac, sacrotuberous, and sacrospinous ligaments with an intact posterior sacroiliac ligament

Explanation

An APC II injury involves symphyseal diastasis (usually >2.5 cm) with disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. The critical posterior sacroiliac ligament remains intact, making the pelvis rotationally unstable ('open book') but vertically stable.

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