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Pelvic & Acetabular Trauma MCQs

Practice Set 35 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 681

Topic: Pelvic & Acetabular Trauma

A 4-year-old girl with residual acetabular dysplasia requires a pelvic osteotomy. The surgeon plans a redirectional osteotomy that hinges at the pubic symphysis. Which of the following osteotomies is described?

. Pemberton osteotomy
. Dega osteotomy
. Salter innominate osteotomy
. Chiari osteotomy
. Ganz periacetabular osteotomy (PAO)

Correct Answer & Explanation

. Salter innominate osteotomy

Explanation

The Salter innominate osteotomy is a complete, redirectional osteotomy that cuts through the ilium to the sciatic notch and hinges at the pubic symphysis. The Pemberton and Dega are incomplete shaping osteotomies that hinge at the triradiate cartilage.

Question 682

Topic: Pelvic & Acetabular Trauma

A newborn is diagnosed with congenital femoral deficiency. Radiographs reveal a complete absence of the proximal femur, including the femoral head, and no acetabular development. Which class does this represent in the Aitken classification?

. Aitken Class A
. Aitken Class B
. Aitken Class C
. Aitken Class D
. Aitken Class E

Correct Answer & Explanation

. Aitken Class D

Explanation

Aitken Class D represents the most severe form of congenital femoral deficiency, characterized by the complete absence of the femoral head, neck, and acetabulum. Class A features a present femoral head and adequate acetabulum with a subtrochanteric varus.

Question 683

Topic: Pelvic & Acetabular Trauma

The Bernese periacetabular osteotomy (PAO) involves multiple bone cuts to reorient the acetabulum. Which of the following pelvic structures is deliberately left intact to maintain pelvic ring stability?

. Superior pubic ramus
. Ischial tuberosity
. Iliac crest
. Posterior column
. Anterior column

Correct Answer & Explanation

. Posterior column

Explanation

The PAO preserves the posterior column of the pelvis, which maintains the continuity of the pelvic ring. This crucial structural preservation allows for earlier mobilization and weight-bearing compared to other pelvic osteotomies.

Question 684

Topic: Pelvic & Acetabular Trauma

A 24-year-old male hockey player presents with anterior groin pain exacerbated by hip flexion and internal rotation. Imaging demonstrates a "pistol grip" deformity and an alpha angle of 65 degrees. The primary pathomechanical process in this condition involves:

. Linear contact between the femoral neck and acetabulum leading to chondral delamination
. Pincer impingement causing posterior labral tears
. Global acetabular overcoverage
. Dysplastic shallow acetabulum leading to edge loading
. Isolated ligamentum teres avulsion

Correct Answer & Explanation

. Linear contact between the femoral neck and acetabulum leading to chondral delamination

Explanation

Cam impingement (characterized by a high alpha angle and pistol grip deformity) causes shear forces at the chondrolabral junction. This leads to outside-in chondral delamination and labral detachment from the acetabular rim.

Question 685

Topic: Pelvic & Acetabular Trauma

Which of the following is the most sensitive imaging modality for detecting early sacroiliitis in a patient with suspected ankylosing spondylitis?

. Plain radiographs of the sacroiliac joints
. CT scan of the sacroiliac joints
. MRI of the sacroiliac joints
. Bone scan
. Ultrasound of the sacroiliac joints

Correct Answer & Explanation

. MRI of the sacroiliac joints

Explanation

MRI of the sacroiliac joints, particularly with STIR (Short Tau Inversion Recovery) sequences to detect bone marrow edema, is the most sensitive imaging modality for detecting early, active sacroiliitis (inflammation of the SI joints) in conditions like ankylosing spondylitis. Plain radiographs are often normal in the early stages, as they primarily show chronic changes (erosions, sclerosis, fusion). CT provides good bony detail but is less sensitive for early inflammatory changes. Bone scans are sensitive but not specific for sacroiliitis. Ultrasound is generally not used for deep joint imaging like the SI joint.

Question 686

Topic: Pelvic & Acetabular Trauma
A 35-year-old man presents with a hemodynamically unstable anteroposterior compression (APC) type III pelvic ring injury following a motorcycle accident. A pelvic binder is applied. What is the most common anatomic source of hemorrhage in this type of injury?
. Internal pudendal artery
. Superior gluteal artery
. Presacral venous plexus and cancellous bone
. Corona mortis
. External iliac artery

Correct Answer & Explanation

. Presacral venous plexus and cancellous bone

Explanation

The vast majority (80-90%) of bleeding in pelvic ring injuries is venous, originating from the presacral venous plexus and bleeding cancellous bone ends. Arterial bleeding accounts for a smaller percentage of life-threatening hemorrhage.

Question 687

Topic: Pelvic & Acetabular Trauma
A 35-year-old male presents following a high-speed motor vehicle collision. He is hypotensive and tachycardic. Radiographs reveal an APC III pelvic ring injury. After initial fluid resuscitation, a pelvic binder is placed, but he remains hemodynamically unstable. A FAST examination is negative. What is the most appropriate next step in management?
. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) or preperitoneal pelvic packing
. Placement of an anterior pelvic external fixator
. Emergent exploratory laparotomy
. Immediate CT angiography of the abdomen and pelvis
. Definitive open reduction and internal fixation of the pelvis

Correct Answer & Explanation

. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) or preperitoneal pelvic packing

Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury and a negative FAST, bleeding is typically from the retroperitoneal venous plexus or pelvic vessels. Preperitoneal pelvic packing, REBOA, or angiography with embolization is the appropriate next step to control hemorrhage after mechanical stabilization.

Question 688

Topic: Pelvic & Acetabular Trauma
A 45-year-old male is brought to the trauma bay following a high-speed motorcycle collision. He has a mechanically unstable pelvis with an anteroposterior compression (APC) type III injury. A pelvic binder is placed, but he remains hemodynamically unstable despite a massive transfusion protocol. FAST exam is negative. What is the most appropriate next step in management?
. Application of an external fixator
. Immediate exploratory laparotomy
. Preperitoneal pelvic packing
. Bilateral internal iliac artery ligation
. CT angiography of the abdomen and pelvis

Correct Answer & Explanation

. Preperitoneal pelvic packing

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and negative FAST, venous bleeding from the presacral plexus or cancellous bone is the most common source. Preperitoneal pelvic packing (or pelvic angiography depending on institutional protocol) is the immediate next step for hemorrhage control.

Question 689

Topic: Pelvic & Acetabular Trauma
A 45-year-old man sustains a severe crush injury resulting in an APC III pelvic ring disruption. He is hemodynamically unstable despite receiving 2L of crystalloid and 2 units of PRBCs. A FAST exam is negative, and a pelvic binder is in place. What is the most appropriate next step in management?
. Immediate open reduction and internal fixation of the pelvis
. Pelvic angiography with embolization or preperitoneal pelvic packing
. Exploratory laparotomy
. Retrograde urethrogram
. CT scan of the abdomen and pelvis

Correct Answer & Explanation

. Pelvic angiography with embolization or preperitoneal pelvic packing

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and no other identified source of bleeding (negative FAST), the hemorrhage is likely retroperitoneal. Immediate pelvic angiography with embolization or preperitoneal packing is indicated.

Question 690

Topic: Pelvic & Acetabular Trauma

Which of the following ligamentous complexes provides the most significant restraint to vertical displacement of the hemipelvis in a completely unstable pelvic ring injury?

. Anterior sacroiliac ligaments
. Sacrospinous ligaments
. Sacrotuberous ligaments
. Posterior sacroiliac ligaments
. Iliolumbar ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

The intact posterior sacroiliac ligamentous complex is the most vital structure for maintaining vertical stability of the pelvic ring. Disruption of these ligaments results in vertical shear instability.

Question 691

Topic: Pelvic & Acetabular Trauma

A 28-year-old motorcyclist is brought to the emergency department in hemorrhagic shock following an accident. A pelvic radiograph shows widening of the pubic symphysis by 4 cm and disruption of the anterior sacroiliac ligaments. Application of a pelvic binder is crucial to control bleeding primarily from which anatomic source?

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

Correct Answer & Explanation

. Presacral venous plexus

Explanation

Antero-posterior compression (APC) pelvic fractures often cause severe retroperitoneal hemorrhage. The predominant source of hemorrhage in pelvic ring injuries is the presacral venous plexus and bleeding from cancellous bone, which is partially tamponaded by reducing the pelvic volume with a binder.

Question 692

Topic: Pelvic & Acetabular Trauma

A 28-year-old man presents with chronic lower back pain and morning stiffness lasting over an hour. Radiographs of the sacroiliac joints are unremarkable.

What is the earliest MRI finding of sacroiliitis in patients with this condition?

. Subchondral sclerosis
. Joint space narrowing
. Bone marrow edema on STIR sequences
. Erosions of the iliac side of the joint
. Ankylosis of the sacroiliac joint

Correct Answer & Explanation

. Bone marrow edema on STIR sequences

Explanation

The earliest sign of sacroiliitis in ankylosing spondylitis is active inflammation manifesting as subchondral bone marrow edema on STIR or T2-weighted fat-suppressed MRI. This finding precedes any structural changes seen on plain radiographs.

Question 693

Topic: Pelvic & Acetabular Trauma
A hemodynamically unstable 35-year-old male is brought to the trauma bay following a motorcycle collision. Pelvic radiographs demonstrate an anteroposterior compression type III (APC-III) pelvic ring injury. Where is the correct anatomical landmark for the application of a circumferential pelvic sheet or commercial binder?
. Over the iliac crests
. Over the anterior superior iliac spines
. Directly over the greater trochanters
. At the level of the symphysis pubis
. Over the subtrochanteric femur

Correct Answer & Explanation

. Directly over the greater trochanters

Explanation

A pelvic binder must be placed and centered precisely over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is mechanically ineffective and can exacerbate an open-book deformity.

Question 694

Topic: Pelvic & Acetabular Trauma
A 45-year-old man sustains an anteroposterior compression (APC) type III pelvic ring injury in a high-speed motorcycle crash. He is hemodynamically unstable upon arrival despite a properly placed pelvic binder and aggressive fluid resuscitation. What is the most likely primary source of his pelvic hemorrhage?
. Superior gluteal artery
. Presacral venous plexus and cancellous bone
. Corona mortis
. Internal pudendal artery
. Obturator artery

Correct Answer & Explanation

. Presacral venous plexus and cancellous bone

Explanation

In major pelvic ring fractures, approximately 80% to 90% of severe bleeding is venous in origin, primarily arising from the presacral venous plexus and the exposed fractured cancellous bone surfaces. While arterial bleeding can be life-threatening, venous sources are far more common overall.

Question 695

Topic: Pelvic & Acetabular Trauma
A 42-year-old farmer is brought to the trauma bay after a tractor rollover. He has a widely displaced symphysis pubis and bilateral sacroiliac joint disruption. Which of the following vascular structures is at greatest risk of injury leading to massive hemorrhage in this classic anteroposterior compression (APC-III) pelvic ring injury?
. Superior gluteal artery
. Internal pudendal artery
. Venous presacral plexus
. Femoral artery
. Obturator artery

Correct Answer & Explanation

. Venous presacral plexus

Explanation

While lateral compression injuries often tear the superior gluteal artery, anteroposterior compression (APC) injuries typically cause massive hemorrhage by disrupting the extensive presacral venous plexus and anterior branches of the internal iliac artery.

Question 696

Topic: Pelvic & Acetabular Trauma
A 40-year-old male presents in hemorrhagic shock following a crush injury to the pelvis. Anteroposterior pelvic radiograph demonstrates an anteroposterior compression type III (APC-III) pelvic ring injury with a widely displaced symphysis and completely disrupted sacroiliac joints. A pelvic binder is applied, and his blood pressure transiently improves. What is the predominant anatomic source of hemorrhage in this specific injury pattern?
. Superior gluteal artery
. Corona mortis
. Presacral venous plexus
. Internal pudendal artery
. Obturator artery

Correct Answer & Explanation

. Presacral venous plexus

Explanation

The presacral venous plexus and bleeding from fractured cancellous bone surfaces account for approximately 80% of hemorrhage in unstable pelvic ring fractures. Arterial bleeding occurs in a minority of cases, more typically involving branches of the internal iliac system such as the superior gluteal or internal pudendal arteries.

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