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2. Trauma MCQs

Practice Set 374 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 7461

Topic: 2. Trauma

In the treatment of an intertrochanteric femur fracture with a sliding hip screw or cephalomedullary nail, which radiographic measurement is the most reliable predictor of lag screw cut-out?

. Neck-shaft angle restoration
. Tip-apex distance greater than 25 mm
. Calcar referenced reduction distance
. Lag screw placement in the posterior-inferior quadrant
. Amount of fracture site impaction

Correct Answer & Explanation

. Neck-shaft angle restoration

Explanation

A tip-apex distance (TAD) greater than 25 mm, as described by Baumgaertner, is the most robust and clinically validated predictor of lag screw cut-out in the fixation of intertrochanteric fractures.

Question 7462

Topic: 2. Trauma

In a subtrochanteric fracture of the femur, the proximal fragment is typically subjected to strong deforming muscle forces. Which muscles are primarily responsible for the characteristic flexion and abduction of the proximal fragment?

. Rectus femoris and vastus lateralis
. Adductor longus and adductor magnus
. Iliopsoas and gluteus medius/minimus
. Hamstrings and gluteus maximus
. Sartorius and gracilis

Correct Answer & Explanation

. Rectus femoris and vastus lateralis

Explanation

In subtrochanteric fractures, the intact muscular attachments to the proximal fragment drive the deformity. The iliopsoas powerfully flexes the proximal fragment, while the gluteus medius and minimus abduct it.

Question 7463

Topic: Pelvic & Acetabular Trauma

A 45-year-old woman with severe developmental dysplasia of the hip (Crowe Type IV) is undergoing total hip arthroplasty. To optimize hip biomechanics and component longevity, where should the acetabular component ideally be placed?

. In the false acetabulum with structural autograft
. In the true anatomic acetabulum
. Two centimeters superior to the transverse acetabular ligament
. Midway between the true and false acetabulum
. Superolateral to the anterior inferior iliac spine

Correct Answer & Explanation

. In the false acetabulum with structural autograft

Explanation

In Crowe IV dysplasia, the hip is completely dislocated. Acetabular reconstruction should ideally be performed at the true anatomic acetabulum to restore the normal center of rotation and optimize hip biomechanics, often necessitating a subtrochanteric shortening osteotomy.

Question 7464

Topic: 2. Trauma

A 32-year-old man sustains a displaced, completely off-ended, vertical femoral neck fracture (Pauwels type III) in a motor vehicle collision. What is the most biomechanically appropriate surgical fixation construct to minimize the risk of nonunion and avascular necrosis in this patient?

. Three parallel cancellous screws placed in an inverted triangle
. A sliding hip screw combined with a derotational cancellous screw
. Cemented unipolar hemiarthroplasty
. Uncemented total hip arthroplasty
. Cephalomedullary nail with dual lag screws

Correct Answer & Explanation

. Three parallel cancellous screws placed in an inverted triangle

Explanation

Pauwels type III fractures are highly vertical and subject to massive shear forces. A sliding hip screw provides superior biomechanical stability against vertical shear compared to multiple cancellous screws, while a derotational screw controls rotation in young patients.

Question 7465

Topic: 2. Trauma

A 78-year-old woman undergoes internal fixation of a stable intertrochanteric femur fracture with a sliding hip screw. To minimize the risk of lag screw cutout, the combined tip-apex distance (TAD) calculated from both the AP and lateral radiographs should ideally be less than:

. 10 mm
. 15 mm
. 25 mm
. 35 mm
. 45 mm

Correct Answer & Explanation

. 10 mm

Explanation

The concept of tip-apex distance (TAD), described by Baumgaertner et al., is the sum of the distance from the lag screw tip to the apex of the femoral head on AP and lateral views. A TAD of less than 25 mm is strongly correlated with a successful outcome and minimal risk of cutout.

Question 7466

Topic: 2. Trauma

A 40-year-old healthy man sustains a highly vertical, displaced femoral neck fracture (Pauwels type III). Which of the following internal fixation constructs provides the greatest biomechanical stability for this fracture pattern?

. Three parallel cannulated screws in an inverted triangle configuration
. Two parallel cannulated screws
. Sliding hip screw (SHS) with a supplemental derotational screw
. Cephalomedullary nail
. Dynamic condylar screw

Correct Answer & Explanation

. Three parallel cannulated screws in an inverted triangle configuration

Explanation

Pauwels type III fractures experience high vertical shear forces that predispose to varus collapse. A sliding hip screw combined with a derotational screw provides superior biomechanical stability and higher failure loads compared to multiple cannulated screws.

Question 7467

Topic: Pelvic & Acetabular Trauma

A 22-year-old collegiate hockey player complains of deep anterior groin pain exacerbated by hip flexion and internal rotation. Imaging confirms a prominent alpha angle and an aspherical femoral head. Which of the following best describes the pathophysiology of his condition?

. Linear contact between the acetabular rim and femoral neck causing rim failure
. Shear forces at the chondrolabral junction causing chondral delamination
. Global overcoverage of the acetabulum leading to pincer impingement
. Posterior subluxation of the femoral head during deep flexion
. Extra-articular impingement of the anterior inferior iliac spine (AIIS)

Correct Answer & Explanation

. Linear contact between the acetabular rim and femoral neck causing rim failure

Explanation

Cam impingement is caused by an aspherical femoral head (prominent alpha angle) engaging the acetabulum during flexion. This creates shear forces that lead to chondral delamination and labral tears, particularly at the anterosuperior chondrolabral junction.

Question 7468

Topic: 2. Trauma

A 78-year-old woman sustains a reverse obliquity intertrochanteric femur fracture after a ground-level fall. Which of the following is the most appropriate surgical intervention?

. Sliding hip screw
. Long cephalomedullary nail
. Multiple cannulated screws
. Cemented hemiarthroplasty
. Proximal femoral locking plate

Correct Answer & Explanation

. Sliding hip screw

Explanation

Reverse obliquity intertrochanteric fractures are mechanically unstable due to lateral wall involvement and medialization of the distal fragment. A cephalomedullary nail provides superior biomechanical control and lower failure rates compared to a sliding hip screw.

Question 7469

Topic: 2. Trauma

A 75-year-old man with a cemented THA sustains a fall resulting in a periprosthetic femur fracture. Radiographs show a spiral fracture around the tip of the stem. The stem is radiographically loose with subsidence, but there is adequate proximal and distal bone stock (Vancouver B2). What is the recommended surgical treatment?

. Open reduction internal fixation with cables and a locking plate, retaining the stem
. Revision to a long, fully porous-coated or fluted tapered diaphyseal-engaging stem
. Impaction bone grafting and placement of a new cemented stem
. Strut allografting alone
. Removal of hardware and placement of an articulating antibiotic spacer

Correct Answer & Explanation

. Open reduction internal fixation with cables and a locking plate, retaining the stem

Explanation

A Vancouver B2 periprosthetic fracture involves a fracture around a loose stem with good bone stock. The standard of care is revision arthroplasty using a diaphyseal-engaging stem (such as a fluted tapered or fully porous-coated stem) that bypasses the fracture by at least 2 cortical diameters.

Question 7470

Topic: 2. Trauma

A 32-year-old man sustains a completely displaced, vertically oriented femoral neck fracture (Pauwels Type III). What is the biomechanically most stable fixation construct for this specific fracture pattern?

. Three parallel cannulated screws in an inverted triangle configuration
. Two parallel cannulated screws placed centrally
. Sliding hip screw with a derotational cancellous screw
. Standard short cephalomedullary nail
. Dynamic condylar screw

Correct Answer & Explanation

. Three parallel cannulated screws in an inverted triangle configuration

Explanation

A sliding hip screw (SHS) combined with a derotational cancellous screw provides the most biomechanically stable construct for vertically oriented (Pauwels III) femoral neck fractures. Cannulated screws have higher failure rates in vertical shear patterns due to inadequate resistance to shear forces.

Question 7471

Topic: 2. Trauma

A 68-year-old woman sustains a reverse obliquity intertrochanteric femur fracture (OTA/AO 31-A3). Why is a long cephalomedullary nail preferred over a sliding hip screw (SHS) for this specific fracture pattern?

. The SHS allows excessive medialization of the distal femoral shaft
. The SHS provides too much rigid fixation leading to nonunion
. The cephalomedullary nail allows controlled sliding along the anatomical axis of the femur
. The cephalomedullary nail prevents post-operative abductor weakness
. The SHS has a higher risk of cutout due to a consistently increased tip-apex distance

Correct Answer & Explanation

. The SHS allows excessive medialization of the distal femoral shaft

Explanation

Reverse obliquity fractures are highly unstable due to the tendency for the distal femoral shaft to shift medially. A cephalomedullary nail acts as an intramedullary buttress to prevent this medialization, making it biomechanically superior to an extramedullary SHS for this pattern.

Question 7472

Topic: 2. Trauma

A 28-year-old man sustains a vertically oriented (Pauwels Type III) femoral neck fracture. Biomechanically, which of the following internal fixation constructs provides the greatest stability against shear forces?

. Three parallel cannulated screws placed in an inverted triangle
. Two parallel cannulated screws
. A sliding hip screw with a derotational cancellous screw
. A cephalomedullary nail
. A fully threaded positioning screw combined with a dynamic hip screw

Correct Answer & Explanation

. Three parallel cannulated screws placed in an inverted triangle

Explanation

Pauwels Type III fractures experience high shear forces. A sliding hip screw with an added derotational screw provides superior biomechanical stability against vertical shear compared to multiple cannulated screws.

Question 7473

Topic: 2. Trauma

A 55-year-old patient is involved in a high-speed motor vehicle collision and sustains a subtrochanteric femur fracture. Predictable deformity of the proximal fragment is primarily caused by which combination of muscular forces?

. Extension, adduction, and internal rotation
. Flexion, abduction, and external rotation
. Flexion, adduction, and internal rotation
. Extension, abduction, and external rotation
. Flexion, abduction, and internal rotation

Correct Answer & Explanation

. Extension, adduction, and internal rotation

Explanation

The proximal fragment in a subtrochanteric fracture is deformed by the iliopsoas (flexion), gluteus medius/minimus (abduction), and short external rotators (external rotation).

Question 7474

Topic: 2. Trauma

A 75-year-old woman presents with a reverse obliquity intertrochanteric femur fracture (AO/OTA 31-A3). If this injury is treated inappropriately with a sliding hip screw (dynamic hip screw), what is the most likely mode of biomechanical failure?

. Femoral head cut-out
. Medial displacement of the femoral shaft
. Z-effect phenomenon
. Lateral displacement of the greater trochanter
. Intrapelvic migration of the lag screw

Correct Answer & Explanation

. Femoral head cut-out

Explanation

A reverse obliquity fracture line lacks the lateral cortical buttress. Compression along a sliding hip screw leads to unopposed medial translation of the distal femoral shaft fragment, resulting in construct failure.

Question 7475

Topic: 2. Trauma

A 35-year-old male sustains a high-energy trauma resulting in a displaced femoral neck fracture.

The predominant blood supply to the adult femoral head, which is critically at risk in this injury, arises directly from which of the following vessels?

. Ascending branch of the lateral femoral circumflex artery
. Medial femoral circumflex artery (lateral epiphyseal branch)
. Artery of the ligamentum teres (foveal artery)
. Inferior gluteal artery
. First perforating branch of the profunda femoris

Correct Answer & Explanation

. Ascending branch of the lateral femoral circumflex artery

Explanation

The major blood supply to the adult femoral head comes from the lateral epiphyseal artery, which is the terminal continuation of the deep branch of the medial femoral circumflex artery (MFCA).

Question 7476

Topic: Pelvic & Acetabular Trauma

A 24-year-old male arrives in the emergency department following a motorcycle collision. He is hypotensive and tachycardic. Pelvic radiographs demonstrate an anteroposterior compression (APC) type III pelvic ring injury. A pelvic binder is applied. For maximum mechanical effectiveness, the binder must be centered at the level of the:

. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis strictly
. Sacral promontory

Correct Answer & Explanation

. Anterior superior iliac spines (ASIS)

Explanation

To optimally reduce pelvic volume and stabilize the fracture, a pelvic binder or sheet must be placed at the level of the greater trochanters. Placement higher over the iliac crests is less effective and can paradoxically open the pelvic floor.

Question 7477

Topic: 2. Trauma

A 68-year-old female presents with acute thigh pain after a minor fall. Radiographs reveal a transverse subtrochanteric fracture with lateral cortical thickening and medial spiking. She has a 9-year history of alendronate use. What is the most appropriate surgical management?

. Open reduction and plate fixation with bone grafting
. Cephalomedullary nailing with attention to the lateral femoral bow
. Bipolar hemiarthroplasty
. Proximal femoral replacement
. Conservative management with a hip spica cast

Correct Answer & Explanation

. Open reduction and plate fixation with bone grafting

Explanation

Atypical femur fractures associated with bisphosphonate use are best treated with full-length cephalomedullary nailing. Surgeons must be cautious of the increased lateral bow, which may require over-reaming or utilizing a nail with a smaller radius of curvature.

Question 7478

Topic: 2. Trauma

A 30-year-old man sustains a displaced, vertically oriented (Pauwels Type III) femoral neck fracture. Which of the following internal fixation constructs provides the most biomechanically stable fixation for this specific high-shear fracture pattern?

. Three parallel fully threaded cancellous screws
. A sliding hip screw coupled with a derotational cancellous screw
. Two parallel partially threaded cancellous screws
. A proximal femoral locking plate alone
. A short retrograde intramedullary nail

Correct Answer & Explanation

. Three parallel fully threaded cancellous screws

Explanation

Pauwels Type III fractures possess high vertical shear forces that lead to failure with standard multiple cancellous screws. A sliding hip screw (with a derotational screw) provides superior biomechanical stability against these sheer stresses.

Question 7479

Topic: 2. Trauma

A 25-year-old man involved in a motor vehicle collision presents with a shortened, internally rotated left lower extremity. Radiographs confirm a posterior hip dislocation without fracture. Which intervention is most critical for minimizing the risk of avascular necrosis (AVN) of the femoral head?

. Surgical open reduction to evacuate the fracture hematoma
. Closed reduction within 6 hours of the injury
. Immediate administration of high-dose corticosteroids
. Post-reduction skeletal traction for 3 weeks
. Protected weight-bearing with crutches for 12 weeks

Correct Answer & Explanation

. Surgical open reduction to evacuate the fracture hematoma

Explanation

The risk of AVN following a traumatic hip dislocation is directly correlated with the time to reduction. Closed reduction performed within 6 hours significantly lowers the incidence of AVN.

Question 7480

Topic: 2. Trauma

When treating a highly comminuted subtrochanteric femur fracture with an antegrade intramedullary nail, establishing a starting entry point that is too lateral to the tip of the greater trochanter typically leads to which of the following mechanical malalignments?

. Varus malalignment
. Valgus malalignment
. Recurvatum deformity
. Procurvatum deformity
. Internal rotational malalignment

Correct Answer & Explanation

. Varus malalignment

Explanation

A lateral starting point forces the intramedullary nail to deviate medially as it enters the canal. This medial vector pushes the proximal fragment into varus malalignment.

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