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2. Trauma MCQs

Practice Set 362 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 7221

Topic: 2. Trauma

To minimize the risk of lag screw cut-out when using a sliding hip screw or cephalomedullary nail for intertrochanteric fracture fixation, the Tip-Apex Distance (TAD) as described by Baumgaertner should be maintained below what value?

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

Correct Answer & Explanation

. 10 mm

Explanation

The Tip-Apex Distance (TAD) is the sum of the distance from the tip of the lag screw to the apex of the femoral head on both AP and lateral radiographs. A TAD of less than 25 mm has been shown to significantly reduce the risk of lag screw cut-out in intertrochanteric fracture fixation.

Question 7222

Topic: 2. Trauma
A 28-year-old woman sustains a high-energy, vertically oriented, displaced femoral neck fracture (Pauwels type III). If internal fixation is chosen, which of the following constructs provides the greatest biomechanical stability against the predominant deforming shear forces?
. Three parallel cannulated screws placed in an inverted triangle
. A sliding hip screw combined with an anti-rotation screw
. Two divergent cannulated screws
. A fully threaded positioning screw
. Standard length unreamed antegrade intramedullary nail without a proximal interlocking screw

Correct Answer & Explanation

. A sliding hip screw combined with an anti-rotation screw

Explanation

Pauwels type III fractures are highly vertical and experience massive shear forces, leading to high rates of nonunion and failure with parallel screw fixation alone. A fixed-angle construct, such as a sliding hip screw combined with a superior anti-rotation screw, is biomechanically superior for resisting these vertical shear forces.

Question 7223

Topic: 2. Trauma
A 25-year-old man presents with a posterior hip dislocation associated with a fracture of the femoral head. A computed tomography scan shows the fracture involves the superior aspect of the femoral head, cephalad to the fovea capitis. What is the correct Pipkin classification for this injury?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

The Pipkin classification describes femoral head fractures associated with hip dislocations. A Type I fracture is caudad to the fovea, Type II is cephalad to the fovea (involving the weight-bearing dome), Type III includes an associated femoral neck fracture, and Type IV includes an associated acetabular fracture.

Question 7224

Topic: 2. Trauma

A 30-year-old man sustains a transverse subtrochanteric femur fracture. Due to the muscular attachments in this region, the proximal fragment is typically displaced into which of the following positions?

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

Correct Answer & Explanation

. Flexion, adduction, and internal rotation

Explanation

The proximal fragment of a subtrochanteric fracture is classically displaced into flexion by the iliopsoas, abduction by the gluteus medius and minimus, and external rotation by the short external rotators. Understanding these deforming forces is critical for obtaining intraoperative reduction.

Question 7225

Topic: 2. Trauma

A 65-year-old woman undergoes fixation of a stable intertrochanteric fracture with a sliding hip screw. Intraoperative fluoroscopy reveals an intact lateral wall thickness of 15 mm. Based on this measurement, what is the most likely biomechanical complication of this construct?

. Avascular necrosis of the femoral head
. Fracture of the lateral wall with subsequent medialization of the shaft
. Nonunion of the greater trochanter
. Anterior perforation of the femoral head by the lag screw
. Iatrogenic sciatic nerve palsy

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

A lateral wall thickness of less than 20.5 mm in an intertrochanteric fracture indicates instability. Using a sliding hip screw in this setting has a high risk of iatrogenic lateral wall fracture during reaming or screw insertion, leading to massive collapse and shaft medialization.

Question 7226

Topic: 2. Trauma

Which of the following intraoperative factors is most predictive of failure (nonunion or loss of fixation) after closed reduction and percutaneous pinning of a displaced femoral neck fracture in a young adult?

. Use of partially threaded rather than fully threaded screws
. Use of parallel rather than divergent screw trajectory
. Quality of the anatomic reduction
. Placement of the inferior screw above the calcar
. Starting the distal screw below the lesser trochanter

Correct Answer & Explanation

. Use of partially threaded rather than fully threaded screws

Explanation

The most critical factor predicting the success of internal fixation for a displaced femoral neck fracture is the quality of the anatomic reduction. Malreduction leads to highly altered biomechanics, shear stress, and early failure or nonunion.

Question 7227

Topic: 2. Trauma

A 45-year-old woman sustained a posterior hip dislocation with an associated posterior wall acetabulum fracture. After closed reduction, she is taken for dynamic fluoroscopic stress testing. Which specific maneuver is most appropriate to evaluate for posterior hip instability that would necessitate open reduction and internal fixation of the posterior wall?

. Hip extension and external rotation
. Hip abduction and external rotation
. Hip extension and adduction
. Hip flexion and internal rotation
. Axial traction in neutral position

Correct Answer & Explanation

. Hip extension and external rotation

Explanation

Dynamic stress testing to evaluate posterior hip instability in the setting of a posterior wall fracture is performed by flexing the hip to 90 degrees and applying internal rotation and axial load. Subluxation of the femoral head under fluoroscopy confirms instability, making ORIF of the posterior wall indicated.

Question 7228

Topic: 2. Trauma

Which of the following fracture patterns is widely considered an absolute contraindication to the use of a standard sliding hip screw (DHS) for definitive fixation?

. Stable two-part intertrochanteric fracture
. Basicervical femoral neck fracture
. Reverse obliquity intertrochanteric fracture
. Subcapital femoral neck fracture in a young patient
. Intertrochanteric fracture with lateral wall thickness of 25 mm

Correct Answer & Explanation

. Stable two-part intertrochanteric fracture

Explanation

A reverse obliquity intertrochanteric fracture pattern is an absolute contraindication to a sliding hip screw. The medial displacement force of the shaft allows the proximal fragment to slide laterally, leading to predictable failure and collapse.

Question 7229

Topic: 2. Trauma

A 35-year-old man sustains a subtrochanteric femur fracture following a high-speed motorcycle collision. Which of the following describes the characteristic position of the proximal fracture fragment secondary to the muscular deforming forces?

. Flexed, adducted, and externally rotated
. Flexed, abducted, and externally rotated
. Extended, adducted, and internally rotated
. Extended, abducted, and externally rotated
. Flexed, abducted, and internally rotated

Correct Answer & Explanation

. Flexed, adducted, and externally rotated

Explanation

The proximal fragment in a subtrochanteric fracture is flexed by the iliopsoas, abducted by the gluteus medius and minimus, and externally rotated by the short external rotators.

Question 7230

Topic: 2. Trauma

When treating an intertrochanteric femur fracture with a sliding hip screw, the tip-apex distance (TAD) is measured to assess the adequacy of lag screw placement. A TAD greater than what threshold value is associated with a significantly increased risk of lag screw cut-out?

. 10 mm
. 15 mm
. 20 mm
. 25 mm
. 35 mm

Correct Answer & Explanation

. 10 mm

Explanation

Baumgaertner et al. demonstrated that a tip-apex distance (TAD) greater than 25 mm is the most significant predictive factor for lag screw cut-out in intertrochanteric fractures treated with a sliding hip screw.

Question 7231

Topic: 2. Trauma
A 40-year-old man presents with a posterior hip dislocation and an associated femoral head fracture located cephalad to the fovea capitis. According to the Pipkin classification, what type of fracture does this represent?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

A Pipkin Type II fracture involves the femoral head cephalad to the fovea capitis. Type I is caudad to the fovea, Type III involves an associated femoral neck fracture, and Type IV involves an associated acetabular fracture.

Question 7232

Topic: 2. Trauma

A 72-year-old woman sustains a reverse obliquity intertrochanteric femur fracture. Which of the following fixation constructs is biomechanically most appropriate for this specific fracture pattern?

. Standard sliding hip screw with a 135-degree angle
. Multiple cannulated cancellous screws
. Cephalomedullary nail
. Hemiarthroplasty
. Non-locking proximal femoral plate

Correct Answer & Explanation

. Standard sliding hip screw with a 135-degree angle

Explanation

Reverse obliquity intertrochanteric fractures are inherently unstable and have high failure rates with standard sliding hip screws due to medial displacement of the shaft. A cephalomedullary nail or a 95-degree fixed-angle device provides superior biomechanical stability.

Question 7233

Topic: 2. Trauma

When evaluating an intertrochanteric fracture for surgical fixation, the lateral wall thickness is a critical factor. Below what threshold of intact lateral wall thickness is the fracture considered highly unstable, thus increasing the failure risk of a standard sliding hip screw?

. 10.5 mm
. 15.5 mm
. 20.5 mm
. 25.5 mm
. 30.5 mm

Correct Answer & Explanation

. 10.5 mm

Explanation

A lateral wall thickness of less than 20.5 mm on an AP radiograph has been shown to be a reliable predictor of postoperative lateral wall fracture when using a sliding hip screw. These unstable patterns are better treated with an intramedullary device.

Question 7234

Topic: Pelvic & Acetabular Trauma

A 25-year-old man presents with a posterior hip dislocation after a high-speed collision. Closed reduction under conscious sedation in the emergency department is unsuccessful. A CT scan demonstrates an empty acetabulum with no large bony fragments. What is the most likely soft-tissue structure blocking closed reduction?

. Iliopsoas tendon
. Ligamentum teres
. Piriformis muscle
. Rectus femoris
. Gluteus maximus

Correct Answer & Explanation

. Iliopsoas tendon

Explanation

In irreducible posterior hip dislocations, the femoral head can buttonhole through the posterior capsule and the short external rotators. The piriformis muscle, obturator internus, or the torn capsule itself are the most common structures preventing closed reduction.

Question 7235

Topic: 2. Trauma




A 75-year-old man presents with groin pain after a fall. Imaging demonstrates a basicervical femoral neck fracture. Which of the following best describes the biomechanical characteristics and optimal fixation of this fracture pattern compared to a transcervical fracture?

. It has lower shear forces and is best treated with three parallel cannulated screws
. It behaves like an extracapsular fracture with high rotational instability, best treated with a cephalomedullary nail or sliding hip screw with derotation
. It has a higher rate of avascular necrosis and requires immediate arthroplasty
. It is primarily a stable tension-sided fracture and requires conservative care
. It lacks capsular attachments and therefore heals rapidly with conservative care

Correct Answer & Explanation

. It has lower shear forces and is best treated with three parallel cannulated screws

Explanation

Basicervical femoral neck fractures are extracapsular and highly unstable, particularly in rotation. They act biomechanically similar to intertrochanteric fractures and require robust fixation such as a cephalomedullary nail or a sliding hip screw, often supplemented with a derotation screw.

Question 7236

Topic: 2. Trauma

When performing closed reduction and percutaneous pinning for a nondisplaced femoral neck fracture in an adult, what is the biomechanically optimal configuration for the three cannulated screws?

. An inverted triangle configuration adjacent to the femoral neck cortices
. A standard triangle configuration with the apex pointing superiorly
. A linear vertical configuration along the calcar
. A parallel configuration grouped strictly in the center of the femoral neck
. Divergent placement to maximize cancellous bone purchase

Correct Answer & Explanation

. An inverted triangle configuration adjacent to the femoral neck cortices

Explanation

The inverted triangle configuration (two screws superiorly, one inferiorly) spread as widely as possible and placed adjacent to the dense cortical bone of the femoral neck provides the highest biomechanical stability and lowest rate of failure.

Question 7237

Topic: 2. Trauma

A 24-year-old male sustains a nondisplaced femoral neck fracture following a fall from height. He is treated with percutaneous cannulated screw fixation. Which of the following factors is most critical in minimizing his risk of developing avascular necrosis (AVN) of the femoral head?

. Routine anterior capsulotomy
. Delaying surgery for 48 hours to allow swelling to subside
. Use of an intraoperative fracture table
. Anatomic reduction and stable mechanical fixation
. Preoperative aspiration of the hip joint

Correct Answer & Explanation

. Routine anterior capsulotomy

Explanation

In young adults with femoral neck fractures, anatomic reduction and rigid fixation are the most critical factors in minimizing the risk of nonunion and avascular necrosis. The routine use of capsulotomy to decompress intracapsular hematoma remains controversial.

Question 7238

Topic: 2. Trauma
A 35-year-old man sustains a completely displaced, vertically oriented femoral neck fracture (Pauwels type III) after a fall from a height. 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
. A sliding hip screw (SHS) with an adjunctive anti-rotation screw
. Two crossed cannulated screws
. A short cephalomedullary nail
. A dynamic condylar screw

Correct Answer & Explanation

. A sliding hip screw (SHS) with an adjunctive anti-rotation screw

Explanation

Pauwels type III fractures are highly vertical and subject to significant shear forces. Biomechanical studies demonstrate that a sliding hip screw combined with an anti-rotation screw provides superior stability against shear and varus displacement compared to multiple cannulated screws.

Question 7239

Topic: 2. Trauma

During closed reduction and internal fixation of a displaced femoral neck fracture, care must be taken to minimize further injury to the primary blood supply of the adult femoral head. Which of the following vessels provides the majority of this blood supply?

. Artery of the ligamentum teres
. Ascending branch of the lateral femoral circumflex artery
. Deep branch of the medial femoral circumflex artery
. Inferior gluteal artery
. First perforating artery of the profunda femoris

Correct Answer & Explanation

. Artery of the ligamentum teres

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) provides the primary blood supply to the adult femoral head via the lateral epiphyseal (retinacular) vessels. The lateral femoral circumflex and artery of the ligamentum teres provide minimal contribution in adults.

Question 7240

Topic: 2. Trauma

A meta-analysis comparing unipolar and bipolar hemiarthroplasty for the treatment of displaced femoral neck fractures in the elderly would most likely demonstrate which of the following findings?

. Bipolar prostheses significantly reduce the 10-year rate of acetabular erosion.
. Bipolar prostheses provide superior long-term functional hip scores.
. Unipolar prostheses have a significantly higher dislocation rate.
. No significant difference in clinical outcomes or acetabular erosion rates at 5 years.
. Unipolar prostheses are associated with a higher 30-day mortality rate.

Correct Answer & Explanation

. Bipolar prostheses significantly reduce the 10-year rate of acetabular erosion.

Explanation

Multiple randomized trials and meta-analyses have shown no clinically significant differences in functional outcomes, dislocation rates, or symptomatic acetabular erosion between unipolar and bipolar hemiarthroplasties at intermediate follow-up, though bipolar implants are more expensive.

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