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Pelvic & Acetabular Trauma MCQs

Practice Set 25 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 481

Topic: Pelvic & Acetabular Trauma
A 35-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. Despite the application of a pelvic binder and aggressive fluid resuscitation, his blood pressure remains 75/40 mm Hg. Focused Assessment with Sonography for Trauma (FAST) is negative for intra-abdominal fluid. What is the most appropriate next step in management?
. Immediate laparotomy for mesenteric repair
. Application of an external fixator and observation
. Preperitoneal pelvic packing or pelvic angiography
. Transfer to the CT scanner for a contrast-enhanced scan
. Administration of tranexamic acid and admission to the ICU

Correct Answer & Explanation

. Preperitoneal pelvic packing or pelvic angiography

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST, the source of bleeding is presumed to be retroperitoneal/pelvic. Preperitoneal pelvic packing or immediate pelvic angiography with embolization are the gold standards for hemorrhage control.

Question 482

Topic: Pelvic & Acetabular Trauma

Which of the following is an essential radiographic criterion for diagnosing Diffuse Idiopathic Skeletal Hyperostosis (DISH) according to Resnick?

. Erosion of the sacroiliac joints
. Flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies
. Severe intervertebral disc space narrowing
. Bilateral facet joint ankylosis
. Positive HLA-B27 antigen test

Correct Answer & Explanation

. Flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies

Explanation

Resnick's criteria for DISH require flowing ossification of at least four contiguous vertebral bodies. It also requires preservation of intervertebral disc height and the absence of sacroiliac joint erosion or facet ankylosis.

Question 483

Topic: Pelvic & Acetabular Trauma

During percutaneous sacroiliac joint fixation, a screw directed too anteriorly through the sacral ala places which neurovascular structure at greatest iatrogenic risk?

. Internal iliac artery
. External iliac vein
. L5 nerve root
. S1 nerve root
. Obturator nerve

Correct Answer & Explanation

. L5 nerve root

Explanation

The L5 nerve root courses directly over the anterior aspect of the sacral ala. Screws or drills that penetrate the anterior cortex of the ala place the L5 nerve root at significant risk of injury.

Question 484

Topic: Pelvic & Acetabular Trauma

A 45-year-old female with a history of untreated developmental dysplasia of the hip (DDH) presents for total hip arthroplasty. Preoperative radiographs demonstrate a high hip dislocation (Crowe Type IV). Which of the following anatomic abnormalities is most consistently encountered during reconstruction of this patient's hip?

. The true acetabulum is located superior and lateral to the false acetabulum.
. The femoral neck exhibits excessive retroversion.
. The femoral medullary canal is unusually wide and capacious.
. The true acetabulum is located inferior and medial to the false acetabulum, and the femur exhibits excessive anteversion.
. The sciatic nerve is shortened and at low risk for stretch injury during reduction.

Correct Answer & Explanation

. The true acetabulum is located inferior and medial to the false acetabulum, and the femur exhibits excessive anteversion.

Explanation

Correct Answer: The true acetabulum is located inferior and medial to the false acetabulum, and the femur exhibits excessive anteversion.In severe developmental dysplasia of the hip (Crowe Type IV), the femoral head is completely dislocated from the true acetabulum and often articulates with a false acetabulum (neoacetabulum) on the ilium. The true acetabulum is located inferior and medial to this false acetabulum and is typically shallow, deficient anteriorly and superiorly, and filled with fibrofatty tissue (pulvinar). On the femoral side, the anatomy is characterized by a narrow (stovepipe) medullary canal, excessive femoral neck anteversion, a short femoral neck, and a posteriorly displaced greater trochanter. The sciatic nerve is often shortened due to the proximal migration of the femur and is at high risk for stretch injury when the hip is brought down to the true acetabulum, often necessitating a femoral shortening osteotomy.

Question 485

Topic: Pelvic & Acetabular Trauma

A 6-year-old non-ambulatory girl with Spinal Muscular Atrophy Type II is noted to have progressive right hip subluxation on annual surveillance radiographs. The hip is currently subluxated 40% but remains reducible. The primary biomechanical driver for this paralytic hip subluxation is an imbalance between which of the following muscle groups?

. Stronger hip abductors overpowering weaker hip adductors.
. Stronger hip extensors overpowering weaker hip flexors.
. Stronger hip flexors and adductors overpowering weaker hip extensors and abductors.
. Global spasticity of all pelvic girdle musculature.
. Primary acetabular dysplasia independent of muscle forces.

Correct Answer & Explanation

. Stronger hip flexors and adductors overpowering weaker hip extensors and abductors.

Explanation

Correct Answer: C (Stronger hip flexors and adductors overpowering weaker hip extensors and abductors.)Hip instability is a common orthopedic complication in non-ambulatory patients with SMA. It is a paralytic dislocation driven by a specific pattern of muscle weakness. In SMA, the hip extensors (gluteus maximus) and hip abductors (gluteus medius/minimus) weaken earlier and more severely than the hip flexors (iliopsoas) and hip adductors. This muscle imbalance creates a deforming force that pulls the proximal femur into flexion and adduction, gradually levering the femoral head posterolaterally out of the acetabulum. SMA is a lower motor neuron disease, so spasticity (an upper motor neuron sign) is absent.

Question 486

Topic: Pelvic & Acetabular Trauma

A 6-year-old girl with Spinal Muscular Atrophy Type II is noted to have progressive right hip subluxation on routine surveillance radiographs. She is non-ambulatory and uses a custom-molded wheelchair. The primary driver of this hip instability is:

. Primary acetabular dysplasia secondary to a genetic collagen defect.
. Avascular necrosis of the femoral head due to recurrent microtrauma.
. Muscle imbalance characterized by relatively strong hip flexors and adductors overpowering weak abductors and extensors.
. Severe spasticity of the hip adductor musculature.
. Ligamentous laxity associated with a concurrent connective tissue disorder.

Correct Answer & Explanation

. Muscle imbalance characterized by relatively strong hip flexors and adductors overpowering weak abductors and extensors.

Explanation

Correct Answer: CHip subluxation and dislocation are highly prevalent in non-ambulatory patients with SMA. The primary etiology is a paralytic muscle imbalance around the hip joint. In SMA, the hip flexors (iliopsoas) and adductors typically retain more strength relative to the profoundly weak hip abductors (gluteus medius/minimus) and extensors (gluteus maximus). Over time, this unopposed flexion and adduction force progressively drives the femoral head laterally and superiorly out of the acetabulum. Because SMA is a lower motor neuron disease, spasticity (an upper motor neuron sign) is absent.

Question 487

Topic: Pelvic & Acetabular Trauma

In designing a new spinal implant for anterior column support, which cross-sectional shape would provide the highest Area Moment of Inertia for resisting bending forces in the sagittal plane, assuming the same cross-sectional area and material?

. A solid circle
. A square
. A thin-walled hollow cylinder with a large outer diameter
. A solid rectangle, oriented vertically
. A triangle

Correct Answer & Explanation

. A thin-walled hollow cylinder with a large outer diameter

Explanation

A thin-walled hollow cylinder with a large outer diameter will provide the highest Area Moment of Inertia for a given cross-sectional area. This shape efficiently distributes the material furthest from the neutral axis, which is the most effective way to maximize MOI and thus resistance to bending and torsion. While a vertically oriented rectangle can be optimized for specific bending directions, the hollow cylinder is generally superior for omni-directional bending resistance for a given amount of material. Solid shapes like circles or squares are less efficient than hollow ones for MOI when material quantity is limited.

Question 488

Topic: Pelvic & Acetabular Trauma
In the acute resuscitation of a hemodynamically unstable patient with an anteroposterior compression (APC) type III pelvic ring injury, what is the most appropriate anatomical landmark for the application of a pelvic circumferential compression device (binder)?
. Anterior superior iliac spines
. Iliac crests
. Greater trochanters
. Pubic symphysis
. Sacral promontory

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders must be placed at the level of the greater trochanters to effectively reduce pelvic volume by applying appropriate compressive forces across the pubic symphysis. Placement over the iliac crests or ASIS can paradoxically open the pelvis further in certain fracture patterns.

Question 489

Topic: Pelvic & Acetabular Trauma

An 18-month-old female presents with an untreated, late-diagnosed Developmental Dysplasia of the Hip (DDH). Open reduction and a pelvic osteotomy are planned to improve anterolateral acetabular coverage. Which of the following pelvic osteotomies utilizes the pubic symphysis as its primary hinge?

. Pemberton osteotomy
. Dega osteotomy
. Salter innominate osteotomy
. Chiari osteotomy
. Steel triple osteotomy

Correct Answer & Explanation

. Salter innominate osteotomy

Explanation

The Salter innominate osteotomy is a complete cut through the ilium extending to the greater sciatic notch. It redirects the entire acetabulum using the pubic symphysis as its hinge. The Pemberton osteotomy hinges on the triradiate cartilage, and the Dega osteotomy hinges on the intact posterior cortex of the ilium.

Question 490

Topic: Pelvic & Acetabular Trauma

A 4-year-old child with developmental dysplasia of the hip (DDH) is scheduled for an innominate osteotomy. Which of the following osteotomies hinges at the pubic symphysis to redirect the entire acetabulum, requiring a complete cut through the ilium from the sciatic notch to the anterior inferior iliac spine?

. Dega osteotomy
. Salter osteotomy
. Pemberton osteotomy
. Chiari osteotomy
. Shelf procedure

Correct Answer & Explanation

. Salter osteotomy

Explanation

The Salter osteotomy is a complete, redirectional transiliac cut that hinges at the pubic symphysis. In contrast, Pemberton and Dega are incomplete, volume-reducing osteotomies that hinge at the triradiate cartilage.

Question 491

Topic: Pelvic & Acetabular Trauma
In the acute trauma bay: A hemodynamically unstable patient with an Anteroposterior Compression Type III (APC-III) pelvic ring injury is receiving a circumferential pelvic binder. To be maximally effective in reducing pelvic volume and controlling hemorrhage without causing paradoxical widening, where must the binder be centered?
. Over the greater trochanters
. Over the iliac crests
. At the level of the umbilicus
. Directly over the anterior superior iliac spines (ASIS)
. Mid-thigh bilaterally

Correct Answer & Explanation

. Over the greater trochanters

Explanation

A common and potentially fatal error in trauma management is placing a pelvic binder too high. If placed over the iliac crests, it can cause the iliac wings to act as a fulcrum, paradoxically widening the true pelvis and exacerbating hemorrhage. The binder must be centered exactly over the greater trochanters of the femur to directly close the pubic symphysis and reduce the pelvic volume.

Question 492

Topic: Pelvic & Acetabular Trauma
Review the radiograph of a hemodynamically unstable trauma patient. The patient has an Anteroposterior Compression (APC) type injury to the pelvic ring. Disruption of which of the following structures differentiates a rotationally unstable but vertically stable APC II injury from a globally unstable APC III injury?
. Symphysis pubis
. Anterior sacroiliac ligaments
. Sacrospinous ligaments
. Posterior sacroiliac ligaments
. Iliolumbar ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

In the Young-Burgess classification, an APC II injury involves disruption of the symphysis pubis, the anterior sacroiliac (SI) ligaments, and the sacrotuberous/sacrospinous ligaments, leading to rotational instability but preserving vertical stability because the strong posterior SI ligaments are intact. An APC III injury implies complete disruption of both the anterior and posterior SI ligaments, leading to both rotational and vertical instability.

Question 493

Topic: Pelvic & Acetabular Trauma

A 32-year-old female is involved in a high-speed MVC. An AP Pelvis radiograph demonstrates symphyseal diastasis of 3.5 cm.

Further imaging confirms the posterior sacroiliac (SI) ligaments are intact. According to the Young-Burgess classification, which of the following ligamentous complexes is MOST likely disrupted in this APC-II injury?

. Posterior sacroiliac ligament only
. Sacrotuberous, sacrospinous, and anterior sacroiliac ligaments
. Iliolumbar ligaments bilaterally
. Sacrotuberous ligament only
. Anterior longitudinal ligament

Correct Answer & Explanation

. Sacrotuberous, sacrospinous, and anterior sacroiliac ligaments

Explanation

An Anteroposterior Compression Type II (APC-II) injury involves disruption of the pubic symphysis (>2.5 cm) along with rupture of the sacrotuberous, sacrospinous, and anterior sacroiliac ligaments. The posterior sacroiliac ligaments remain intact, providing vertical stability but resulting in rotational instability (an 'open book' pelvis).

Question 494

Topic: Pelvic & Acetabular Trauma
A 28-year-old male is brought to the trauma bay following a high-speed motor vehicle collision. He is hypotensive and tachycardic. Pelvic radiographs reveal an anteroposterior compression type III (APC-III) pelvic ring injury. A circumferential pelvic binder is requested to reduce pelvic volume. To be most effective, the binder should be centered directly over which of the following anatomic landmarks?
. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Symphysis pubis
. Umbilicus

Correct Answer & Explanation

. Greater trochanters

Explanation

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

Question 495

Topic: Pelvic & Acetabular Trauma
A hemodynamically unstable patient is brought to the trauma bay after a high-speed motor vehicle collision. The anteroposterior pelvic radiograph shows an APC-III injury with >2.5 cm widening of the pubic symphysis. To properly apply a pelvic binder to reduce pelvic volume, over which anatomic landmark should the binder be centered?
. Iliac crests
. Greater trochanters
. Anterior superior iliac spines
. Pubic symphysis
. Subtrochanteric femur

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder must be applied directly over the greater trochanters to effectively close an open-book pelvic ring injury. Placing the binder higher, over the iliac crests or anterior superior iliac spines, can paradoxically worsen the pubic diastasis and is less effective at reducing pelvic volume and controlling hemorrhage.

Question 496

Topic: Pelvic & Acetabular Trauma

A patient sustains a pelvic ring injury. What is a critical initial 'pressure-related' maneuver to control hemorrhage associated with these injuries?

. Application of external pelvic compression (e.g., binder or sheet).
. Immediate surgical exploration and vessel ligation.
. Aggressive crystalloid fluid resuscitation.
. Insertion of a femoral traction pin.
. Transfusion of packed red blood cells.

Correct Answer & Explanation

. Application of external pelvic compression (e.g., binder or sheet).

Explanation

External pelvic compression, typically achieved with a pelvic binder or even a simple sheet wrapped tightly around the greater trochanters, is a critical initial maneuver in managing hemodynamically unstable pelvic ring injuries. By reducing the volume of the disrupted pelvic cavity, it helps to tamponade venous and arterial bleeding, thereby increasing pressure within the pelvic space and reducing hemorrhage. While fluid resuscitation and blood transfusion are also vital, they address theconsequencesof bleeding, whereas external compression directly helpscontrolthe bleeding source. Surgical exploration is reserved for ongoing instability despite compression. Femoral traction is for associated long bone fractures, not hemorrhage control.

Question 497

Topic: Pelvic & Acetabular Trauma
A 50-year-old male arrives at the trauma bay in hemorrhagic shock following an anteroposterior compression (APC III) pelvic ring injury. Emergency medical services placed a commercial pelvic binder in the field. Upon evaluation, to maximize the mechanical closure of the pelvic ring and tamponade the presacral venous plexus bleeding, the pelvic binder must be accurately centered over which anatomic landmark?
. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Symphysis pubis
. Femoral neck

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders are critical in the acute management of mechanically unstable, open-book pelvic ring injuries (APC II/III) to reduce pelvic volume and tamponade venous bleeding. To be effective, the binder must be placed directly over the greater trochanters. Placement too high (e.g., over the iliac crests) is a common error and may paradoxically open the pelvis further or fail to reduce the volume adequately.

Question 498

Topic: Pelvic & Acetabular Trauma

A 38-year-old female presents in hemorrhagic shock following a crush injury to the pelvis. Radiographs demonstrate a vertical shear pelvic ring disruption with marked displacement of the sacroiliac joint. Despite the application of a pelvic binder and massive transfusion protocol, she remains hemodynamically unstable. If arterial bleeding is contributing to her shock, which artery is most likely injured in the posterior aspect of this pelvic ring disruption?

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

Correct Answer & Explanation

. Superior gluteal artery

Explanation

While venous bleeding (from the presacral venous plexus) and cancellous bone bleeding are the most common sources of hemorrhage in pelvic fractures overall, arterial bleeding can be catastrophic. The superior gluteal artery is the most frequently injured artery in posterior pelvic ring disruptions, particularly those involving sacral fractures or major sacroiliac joint disruptions. The internal pudendal and obturator arteries are more commonly injured in anterior ring disruptions (e.g., rami fractures).

Question 499

Topic: Pelvic & Acetabular Trauma

A 34-year-old male arrives in the trauma bay in hemorrhagic shock after a crush injury to the pelvis. AP pelvis radiograph demonstrates complete disruption of the pubic symphysis (5 cm diastasis) and widened sacroiliac joints bilaterally. A pelvic binder is to be applied. What is the correct anatomical landmark for the optimal placement of the binder?

. Iliac crests
. Greater trochanters
. Anterior superior iliac spines
. Pubic symphysis
. Umbilicus

Correct Answer & Explanation

. Greater trochanters

Explanation

To effectively reduce pelvic volume and control venous hemorrhage in an 'open book' pelvic fracture, a pelvic binder must be centered directly over the greater trochanters. Placement over the iliac crests is ineffective and can exacerbate the deformity.

Question 500

Topic: Pelvic & Acetabular Trauma

To effectively reduce pelvic volume and stabilize an 'open book' pelvic ring injury in the emergency department, a pelvic binder should be anatomically centered over the:

. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Symphysis pubis
. Ischial tuberosities

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders are biomechanically most effective at closing the pelvic volume when centered directly over the greater trochanters. Placement higher over the iliac crests or ASIS may fail to close the symphysis or paradoxically worsen the deformity.

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