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2. Trauma MCQs

Practice Set 337 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 6721

Topic: Lower Extremity Trauma

The meniscus relies on its unique structural composition to distribute axial loads in the knee. The primary function of the circumferentially oriented Type I collagen fibers in the menisci is to?

. Resist shear stresses during knee flexion
. Resist radial stresses during varus loading
. Resist hoop stresses generated by axial compression
. Provide nourishment to the avascular inner third
. Attach the meniscal horns to the tibial plateau

Correct Answer & Explanation

. Resist hoop stresses generated by axial compression

Explanation

Axial loading of the knee tends to extrude the meniscus peripherally. The robust circumferential Type I collagen fibers resist this outward expansion by converting compressive forces into tensile "hoop stresses," maintaining joint congruity.

Question 6722

Topic: 2. Trauma

When placing a cortical screw for fracture fixation, which of the following alterations in screw geometry will most significantly increase its pullout strength?

. Increasing the minor (core) diameter
. Decreasing the thread pitch
. Increasing the major (outer) diameter
. Using a cannulated screw design
. Increasing the length of the unthreaded shaft

Correct Answer & Explanation

. Increasing the major (outer) diameter

Explanation

Pullout strength of a screw is most strongly proportional to the major (outer) diameter of the screw. Other factors include thread pitch, length of engagement, and the shear strength of the surrounding bone.

Question 6723

Topic: 2. Trauma

In bridge plating of a comminuted diaphyseal fracture, leaving empty screw holes over the fracture site (increasing the working length) has what effect on the mechanical construct?

. Decreases bending stiffness and increases strain at the fracture
. Increases torsional stiffness only
. Decreases construct flexibility
. Decreases strain at the fracture site by increasing flexibility
. Increases shear stress on the plate

Correct Answer & Explanation

. Decreases bending stiffness and increases strain at the fracture

Explanation

Increasing the working length of a plate increases its flexibility. By distributing the deformation over a longer segment, it decreases the interfragmentary strain at the fracture site, which promotes secondary bone healing.

Question 6724

Topic: Lower Extremity Trauma

Placing a longitudinal slot in a cylindrical intramedullary nail significantly decreases which of its primary mechanical properties?

. Bending rigidity
. Torsional rigidity
. Tensile strength
. Compressive strength
. Fatigue life under compression

Correct Answer & Explanation

. Torsional rigidity

Explanation

Slotted nails have significantly less torsional rigidity compared to solid or closed-section nails. While this allows for easier insertion and some radial compressibility, it substantially reduces rotational stability.

Question 6725

Topic: 2. Trauma

When utilizing a bridge plating technique for a highly comminuted femoral shaft fracture, increasing the working length of the plate has what biomechanical effect on the construct?

. Increases torsional stiffness
. Decreases bending stiffness
. Increases the risk of screw pullout
. Decreases interfragmentary strain at the fracture site
. Increases the overall rigidity of the fixation

Correct Answer & Explanation

. Decreases bending stiffness

Explanation

The working length of a plate is the distance between the two innermost screws spanning the fracture. Increasing the working length decreases the bending stiffness, creating a more flexible construct that promotes secondary bone healing.

Question 6726

Topic: 2. Trauma

A titanium intramedullary nail is used to stabilize a transverse tibial diaphyseal fracture.

This construct represents which type of biomechanical environment, and what is the expected predominant mode of fracture healing?

. Load-bearing, primary bone healing
. Load-bearing, secondary bone healing
. Load-sharing, primary bone healing
. Load-sharing, secondary bone healing
. Stress-shielding, primary bone healing

Correct Answer & Explanation

. Load-sharing, secondary bone healing

Explanation

Intramedullary nails act as load-sharing devices that allow for axial micromotion at the fracture site while controlling bending and rotation. This relative stability promotes callus formation, which is the hallmark of secondary (indirect) bone healing.

Question 6727

Topic: Pelvic & Acetabular Trauma

A 45-year-old man is brought to the emergency department after a high-speed motor vehicle collision. He is hypotensive with a blood pressure of 80/40 mm Hg. A pelvic radiograph shows a severely displaced 'open-book' pelvic ring injury. A commercial pelvic binder is ordered. To be most effective, the binder should be centered over which of the following anatomic landmarks?

. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Pubic symphysis
. Sacral promontory

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders should be centered over the greater trochanters to effectively reduce pelvic volume and control hemorrhage. Placement over the iliac crests or ASIS is less effective and can paradoxically widen the pelvic ring.

Question 6728

Topic: 2. Trauma

A 32-year-old construction worker falls from a scaffolding, sustaining an acetabular fracture. Radiographs and CT imaging reveal a fracture pattern where no portion of the articular surface remains attached to the axial skeleton. Which of the following radiographic findings is pathognomonic for this fracture type?

. Gull sign
. Spur sign
. Teardrop disruption
. Ilioischial line disruption
. Obturator ring displacement

Correct Answer & Explanation

. Spur sign

Explanation

A 'Spur sign' on an obturator oblique radiograph represents the intact ilium projecting posterior to the displaced acetabulum. It is pathognomonic for a both-column acetabular fracture, signifying complete articular detachment.

Question 6729

Topic: 2. Trauma
A 28-year-old man sustains a displaced, completely off-ended, transcervical femoral neck fracture (Pauwels type III) after a fall from a height. Open reduction and internal fixation are planned. Which of the following constructs provides the most biomechanically stable fixation for this vertically oriented fracture pattern?
. Three parallel cannulated screws in an inverted triangle
. Three parallel cannulated screws in a standard triangle
. A sliding hip screw (DHS) with a derotation screw
. A cephalomedullary nail
. A bipolar hemiarthroplasty

Correct Answer & Explanation

. A sliding hip screw (DHS) with a derotation screw

Explanation

Pauwels type III fractures are highly vertically oriented and subject to severe shear forces. A sliding hip screw (DHS) with a supplemental anti-rotation screw provides superior biomechanical stability against vertical shear compared to multiple cannulated screws.

Question 6730

Topic: 2. Trauma

A 40-year-old woman is scheduled for open reduction and internal fixation of a severe posterolateral tibial plateau fracture. An isolated posterolateral surgical approach without fibular osteotomy is chosen. Which of the following structures is at greatest risk of iatrogenic injury during this approach?

. Tibial nerve
. Common peroneal nerve
. Popliteal artery
. Saphenous nerve
. Sural nerve

Correct Answer & Explanation

. Common peroneal nerve

Explanation

The posterolateral approach to the tibial plateau requires careful dissection to avoid injury to the common peroneal nerve. The nerve runs directly posterior to the fibular head before wrapping anteriorly around the fibular neck.

Question 6731

Topic: 2. Trauma

A 75-year-old woman sustains a reverse-oblique intertrochanteric femur fracture (AO/OTA 31-A3). She is medically stable for surgery. Which of the following is the most appropriate fixation implant?

. Multiple parallel cannulated screws
. A fixed-angle blade plate
. A sliding hip screw (DHS)
. A long cephalomedullary nail
. A hemiarthroplasty

Correct Answer & Explanation

. A long cephalomedullary nail

Explanation

Reverse-oblique fractures lack lateral wall support, making sliding hip screws prone to medial displacement and early cutout. A cephalomedullary nail (preferably long) acts as an internal buttress, providing the most stable fixation.

Question 6732

Topic: 2. Trauma

A 26-year-old motorcyclist sustains a coronal plane fracture of the lateral femoral condyle (Hoffa fracture). Open reduction and internal fixation are planned. Which of the following screw configurations provides the most appropriate interfragmentary compression for this specific injury pattern?

. Medial-to-lateral lag screws
. Lateral-to-medial lag screws
. Anterior-to-posterior lag screws
. Distal-to-proximal lag screws
. Parallel locking screws from a lateral plate

Correct Answer & Explanation

. Anterior-to-posterior lag screws

Explanation

Hoffa fractures are coronal plane shear fractures of the femoral condyle. Interfragmentary lag screw fixation must be directed orthogonally to the fracture plane, which requires an anterior-to-posterior (or posterior-to-anterior) trajectory.

Question 6733

Topic: 2. Trauma

A 42-year-old man presents with a closed, highly comminuted tibial pilon fracture with severe soft tissue swelling and fracture blisters. A spanning external fixator is applied. To avoid tethering of the anterior soft tissues and facilitate future open reduction and internal fixation, how should the foot be positioned during fixator placement?

. Maximum plantarflexion
. Neutral dorsiflexion
. 15 degrees of dorsiflexion
. Maximum inversion
. Maximum eversion

Correct Answer & Explanation

. Neutral dorsiflexion

Explanation

When placing a spanning external fixator for a pilon fracture, the ankle should be held in neutral (0 degrees) to prevent equinus contracture. This optimal position facilitates subsequent definitive fixation and proper soft tissue healing.

Question 6734

Topic: 2. Trauma

A 24-year-old soccer player sustains a closed, midshaft tibia fracture treated with intramedullary nailing. Postoperatively, he develops severe, unrelenting leg pain exacerbated by passive stretch of the hallux. If the involved compartment is not rapidly decompressed, which sensory deficit is most likely to develop first?

. Plantar aspect of the foot
. First dorsal web space
. Lateral border of the foot
. Medial aspect of the lower leg
. Dorsum of the foot excluding the first web space

Correct Answer & Explanation

. First dorsal web space

Explanation

Passive stretch of the hallux exacerbates pain in anterior compartment syndrome. The deep peroneal nerve resides in this compartment, and severe ischemia will lead to sensory loss in its autonomous zone, the first dorsal web space.

Question 6735

Topic: 2. Trauma

A 45-year-old man undergoes tension band wiring for a transverse patella fracture. According to the tension band principle, the wire construct works by converting what type of force at the anterior patellar surface into a compressive force at the articular surface during knee flexion?

. Shear
. Compression
. Tension
. Torsion
. Bending

Correct Answer & Explanation

. Tension

Explanation

The tension band principle relies on converting tensile forces (which occur on the convex, anterior surface of the patella during knee flexion) into dynamic compressive forces at the concave articular surface.

Question 6736

Topic: Pelvic & Acetabular Trauma

A 45-year-old man is brought to the trauma bay in hemorrhagic shock following a motorcycle crash. A pelvic radiograph demonstrates an open-book pelvic ring injury.

What is the most appropriate anatomical landmark for the optimal placement of a circumferential pelvic sheet or binder?

. Iliac crests
. Greater trochanters
. Anterior superior iliac spines
. Pubic symphysis
. Sacral promontory

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder should be centered directly over the greater trochanters to effectively close the pelvic ring and reduce intrapelvic volume. Placement over the iliac crests is a common error that can fail to reduce the diastasis or paradoxically widen the pelvis.

Question 6737

Topic: 2. Trauma
A 28-year-old man sustains a displaced, high-shear vertical (Pauwels type III) femoral neck fracture. Open reduction and internal fixation is planned. What is the most common mechanical mode of failure for this specific fracture pattern when treated with three parallel cancellous lag screws?
. Varus collapse and shortening
. Valgus impaction and joint penetration
. Anterior cutout of the screws
. Nonunion due to hypertrophic callus formation
. Chondrolysis of the femoral head

Correct Answer & Explanation

. Varus collapse and shortening

Explanation

Pauwels type III fractures experience high vertical shear forces across the fracture site. Fixation with parallel cancellous screws alone often fails to resist these shear forces, predictably leading to varus collapse, limb shortening, and subsequent nonunion.

Question 6738

Topic: 2. Trauma

A surgeon is treating a proximal third tibial shaft fracture with an intramedullary nail. Apex anterior (procurvatum) and valgus deformities are anticipated during nail passage. Where should blocking (Poller) screws be placed in the proximal fragment to prevent this malalignment?

. Anterior and medial to the nail track
. Posterior and lateral to the nail track
. Posterior and medial to the nail track
. Anterior and lateral to the nail track
. Posteriorly in the distal fragment only

Correct Answer & Explanation

. Posterior and lateral to the nail track

Explanation

Blocking screws should be placed on the concave side of the anticipated deformity to centralize the nail. To prevent procurvatum (nail goes posterior) and valgus (nail goes lateral) in the proximal segment, screws are placed posterior and lateral to the nail track.

Question 6739

Topic: 2. Trauma

A 35-year-old man sustains a subtrochanteric femur fracture. Without specific reduction maneuvers, what is the predictable deformity of the proximal fragment due to the muscular deforming forces?

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

Correct Answer & Explanation

. Flexion, abduction, and external rotation

Explanation

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

Question 6740

Topic: 2. Trauma
A 28-year-old man sustains a highly vertical (Pauwels type III) basicervical femoral neck fracture. To maximize biomechanical stability and minimize the risk of shear failure, which of the following constructs is most appropriate?
. Multiple parallel partially threaded cancellous screws
. A sliding hip screw with a supplemental derotation screw
. Unipolar hemiarthroplasty
. Short cephalomedullary nail

Correct Answer & Explanation

. A sliding hip screw with a supplemental derotation screw

Explanation

Vertical Pauwels type III fractures experience high shear forces. In a young patient, a sliding hip screw with a derotation screw offers superior biomechanical stability against shear and varus collapse compared to multiple cancellous screws.

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