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2. Trauma MCQs

Practice Set 253 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 5041

Topic: 2. Trauma
A 25-year-old male sustains a highly displaced, vertically oriented femoral neck fracture (Pauwels type III). The plan is for joint-preserving internal fixation. Which of the following constructs provides the greatest biomechanical stability against vertical shear forces?
. Three parallel cancellous screws
. Two parallel cancellous screws
. Sliding hip screw (SHS) with a derotation screw
. Cannulated screws placed in an inverted triangle configuration
. Isolated cephalomedullary nail

Correct Answer & Explanation

. Sliding hip screw (SHS) with a derotation screw

Explanation

Pauwels type III fractures are highly vertical (>50 degrees) and experience massive shear forces, leading to high rates of nonunion and failure with traditional parallel cancellous screws. A sliding hip screw (with a derotation screw) or a proximal femoral locking plate provides superior biomechanical stability against these vertical shear forces compared to multiple cancellous screws.

Question 5042

Topic: 2. Trauma

In the surgical treatment of intertrochanteric femur fractures using a sliding hip screw or a cephalomedullary nail, achieving a Tip-Apex Distance (TAD) of less than 25 mm is a critical objective. What is the primary biomechanical rationale for this metric?

. It prevents nonunion of the fracture
. It significantly decreases the risk of lag screw cut-out
. It eliminates the risk of avascular necrosis of the femoral head
. It prevents anterior thigh pain from the distal locking screws
. It allows for dynamic dynamization of the fracture site

Correct Answer & Explanation

. It significantly decreases the risk of lag screw cut-out

Explanation

Described by Baumgaertner, 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 is the most reliable predictor of successful fixation, significantly decreasing the risk of lag screw cut-out through the osteoporotic femoral head.

Question 5043

Topic: 2. Trauma

A 30-year-old male sustains a posterior wall acetabular fracture following a dashboard injury. Which of the following radiographic findings is the most reliable indicator of posterior hip instability mandating operative fixation?

. Involvement of >20% of the posterior wall width on axial CT
. Involvement of >50% of the posterior wall width on axial CT
. Presence of the 'teardrop' sign on the AP pelvis radiograph
. An associated undisplaced fracture of the quadrilateral plate
. Ischial spine avulsion on the obturator oblique view

Correct Answer & Explanation

. Involvement of >50% of the posterior wall width on axial CT

Explanation

The size of the posterior wall fragment is a primary determinant of hip stability. Fragments involving >50% of the posterior wall width on axial CT are virtually always unstable and require ORIF. Fragments <20% are generally stable. Those between 20-50% are indeterminate and may require an examination under anesthesia (EUA) or dynamic fluoroscopy to assess stability.

Question 5044

Topic: 2. Trauma

A 68-year-old female who has been taking alendronate for 8 years presents with a 2-month history of dull ache in her right thigh. Radiographs demonstrate lateral cortical thickening and a transverse radiolucent line involving only the lateral cortex of the subtrochanteric femur. According to AAOS guidelines, what is the primary indication for prophylactic intramedullary nailing in this patient?

. The duration of bisphosphonate therapy exceeding 5 years
. A cortical thickness greater than 5 mm
. The presence of clinical thigh pain
. Medial cortical spiking on the radiograph
. A femoral bowing angle greater than 10 degrees

Correct Answer & Explanation

. The presence of clinical thigh pain

Explanation

This patient has an incomplete atypical femur fracture (AFF). The presence of clinical thigh pain in the setting of radiographic evidence of an incomplete AFF (lateral cortical radiolucent line/beaking) is a strong indication for prophylactic intramedullary nailing to prevent catastrophic completion of the fracture.

Question 5045

Topic: 2. Trauma

A 35-year-old male undergoes open reduction and internal fixation of a transverse patella fracture utilizing a tension band wiring technique. Biomechanically, for this construct to successfully convert tensile forces anteriorly into compressive forces at the articular surface during knee flexion, which of the following must be present?

. An intact anterior soft tissue envelope
. An intact posterior articular bony buttress without comminution
. The use of braided titanium cables instead of stainless steel wire
. Placement of the K-wires anterior to the equator of the patella
. Concomitant lateral retinacular release to reduce extensor mechanism tension

Correct Answer & Explanation

. An intact posterior articular bony buttress without comminution

Explanation

The tension band principle relies on applying an implant eccentrically on the tension side of a fractured bone to convert tensile forces into compressive forces across the fracture site upon loading. For this to work, the opposite cortex (in the patella, the posterior articular bony surface) must be intact to act as a buttress. If there is comminution on the compressive side, the construct will collapse.

Question 5046

Topic: Pelvic & Acetabular Trauma
A 40-year-old male is brought to the trauma bay with hemodynamic instability following a crush injury to the pelvis. Radiographs demonstrate an anteroposterior compression (APC) III pelvic ring injury. A non-invasive pelvic binder is ordered. To optimally reduce pelvic volume and stabilize the ring, over which anatomic landmarks should the binder be centered?
. Iliac crests
. Greater trochanters
. Anterior superior iliac spines (ASIS)
. Pubic symphysis
. Umbilicus

Correct Answer & Explanation

. Greater trochanters

Explanation

To effectively reduce an open-book pelvic injury (APC mechanism) and decrease pelvic volume, the pelvic binder must be centered over the greater trochanters. Placing the binder too high (e.g., over the iliac crests or ASIS) is a common error that fails to close the posterior ring and can paradoxically widen the pelvis.

Question 5047

Topic: 2. Trauma
A 25-year-old male sustains a high-energy Pauwels Type III femoral neck fracture. Biomechanical studies indicate that which of the following internal fixation constructs provides the greatest stability for this specific fracture pattern?
. Three parallel cannulated screws in an inverted triangle configuration
. Three parallel cannulated screws in an upright triangle configuration
. A sliding hip screw with an anti-rotation screw
. A fixed-angle blade plate without compression
. A cephalomedullary nail with a single lag screw

Correct Answer & Explanation

. A sliding hip screw with an anti-rotation screw

Explanation

Pauwels Type III fractures have a highly vertical orientation resulting in significant shear forces. A fixed-angle construct, such as a sliding hip screw with a derotation screw, provides superior biomechanical stability and higher load-to-failure compared to parallel cannulated screws.

Question 5048

Topic: 2. Trauma

In a subtrochanteric femur fracture, the proximal fragment is predictably displaced by the deforming forces of the regional musculature. Which of the following best describes the position of the proximal fragment?

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

Correct Answer & Explanation

. Flexed, abducted, and externally rotated

Explanation

The proximal fragment is flexed by the iliopsoas, abducted by the gluteus medius and minimus, and externally rotated by the short external rotators. Understanding these forces is critical for proper intraoperative reduction and implant placement.

Question 5049

Topic: 2. Trauma

During preoperative planning for a 31-A1 intertrochanteric femur fracture, measurement of the lateral wall thickness on the anteroposterior radiograph is performed. A lateral wall thickness below which threshold is considered a significant predictor for iatrogenic lateral wall fracture if a dynamic hip screw (DHS) is used?

. 20.5 mm
. 25.5 mm
. 30.5 mm
. 35.5 mm
. 40.5 mm

Correct Answer & Explanation

. 20.5 mm

Explanation

A lateral wall thickness of less than 20.5 mm is a reliable threshold indicating a high risk for lateral wall blowout during DHS preparation. These patients are better managed with a cephalomedullary nail to prevent lateral wall failure.

Question 5050

Topic: 2. Trauma

A 30-year-old male sustains a Fraser Type IIa floating knee injury consisting of a diaphyseal femur fracture and an intra-articular tibial plateau fracture. According to damage control principles and optimal functional outcomes in a hemodynamically stable patient, what is the recommended sequence of definitive fixation?

. External fixation of the tibia followed by intramedullary nailing of the femur
. Intramedullary nailing of the femur followed by open reduction and internal fixation of the tibia
. Open reduction and internal fixation of the tibia followed by intramedullary nailing of the femur
. Concurrent definitive fixation using two surgical teams simultaneously
. Open reduction and internal fixation of the femur followed by external fixation of the tibia

Correct Answer & Explanation

. Intramedullary nailing of the femur followed by open reduction and internal fixation of the tibia

Explanation

In a floating knee injury, definitive stabilization of the femur is generally performed first. This establishes control of the limb, aids in mobilizing the patient, and simplifies the subsequent complex intra-articular reconstruction of the tibial plateau.

Question 5051

Topic: 2. Trauma

When performing an intramedullary nailing of a proximal third tibial metaphyseal fracture via an infrapatellar approach, the fracture typically drifts into apex anterior (procurvatum) and valgus deformity. To prevent this, where should the Poller (blocking) screws be placed relative to the intended path of the nail in the proximal segment?

. Anterior and medial
. Posterior and lateral
. Anterior and lateral
. Posterior and medial
. Central and medial

Correct Answer & Explanation

. Posterior and lateral

Explanation

Poller screws should be placed on the concave side of the anticipated deformity to substitute for missing cortical bone. To prevent apex anterior and valgus deformities, screws are placed posterior and lateral to the nail track in the proximal segment.

Question 5052

Topic: 2. Trauma

A 35-year-old male presents with persistent mid-thigh pain 9 months after undergoing reamed intramedullary nailing for a closed femoral shaft fracture. Radiographs show an oligotrophic nonunion with intact hardware. Infection workup is negative. What is the most appropriate next step in surgical management?

. Removal of hardware, compression plating, and iliac crest bone grafting
. Exchange nailing with an intramedullary nail that is 1 to 2 mm larger in diameter
. Dynamization of the current intramedullary nail
. Augmentation with an external fixator
. Injection of bone morphogenetic protein-2 (BMP-2) under fluoroscopic guidance

Correct Answer & Explanation

. Exchange nailing with an intramedullary nail that is 1 to 2 mm larger in diameter

Explanation

Aseptic diaphyseal femoral nonunions treated initially with an IM nail are effectively managed with exchange nailing using a reamed nail larger by 1-2 mm. This enhances both the mechanical stability and the biological healing environment.

Question 5053

Topic: 2. Trauma

A 28-year-old male presents after a posterior knee dislocation. The joint is reduced in the emergency department and pulses are palpable. A handheld Doppler reveals an Ankle-Brachial Index (ABI) of 0.8 on the injured side. What is the most appropriate next step in management?

. Re-examine the vascular status every 2 hours for 24 hours
. Application of a bridging external fixator
. CT angiography of the lower extremity
. Immediate operative exploration of the popliteal artery
. Four-compartment fasciotomy of the lower leg

Correct Answer & Explanation

. CT angiography of the lower extremity

Explanation

An Ankle-Brachial Index (ABI) less than 0.9 after a knee dislocation strongly suggests a significant arterial injury, such as an intimal tear. CT angiography is the diagnostic gold standard and must be performed urgently to localize the injury before potential ischemia.

Question 5054

Topic: 2. Trauma

A coronal shear fracture of the femoral condyle (Hoffa fracture) requires precise surgical planning. Based on the biomechanics of knee loading and natural alignment, which anatomic location is most commonly affected by this specific fracture pattern?

. Medial femoral condyle
. Lateral femoral condyle
. Femoral trochlea
. Both condyles equally
. Intercondylar notch

Correct Answer & Explanation

. Lateral femoral condyle

Explanation

Hoffa fractures most commonly involve the lateral femoral condyle. This is due to the natural physiologic valgus of the knee, which directs axial transmission forces primarily through the lateral condyle, especially when the knee is flexed.

Question 5055

Topic: 2. Trauma
A 75-year-old female with a 12-year-old primary total knee arthroplasty sustains a periprosthetic distal femur fracture classified as Lewis-Rorabeck Type III. Radiographs demonstrate a fracture proximal to the flange with obvious loosening of the femoral component. What is the treatment of choice?
. Retrograde intramedullary nailing
. Open reduction and internal fixation with a lateral locked plate
. Distal femoral replacement (tumor prosthesis)
. Spanning external fixation until fracture union
. Long-leg cast immobilization

Correct Answer & Explanation

. Distal femoral replacement (tumor prosthesis)

Explanation

Lewis-Rorabeck Type III fractures are characterized by a loose femoral component. The definitive treatment for an elderly patient with this injury is a distal femoral replacement, which simultaneously resolves the fracture and the failed implant, allowing early mobilization.

Question 5056

Topic: 2. Trauma

A 35-year-old male is evaluated for persistent groin pain 8 months after internal fixation of a femoral neck fracture. Radiographs reveal a nonunion with hardware cut-out, but MRI confirms the femoral head is viable. What is the most appropriate joint-preserving surgical intervention?

. Revision open reduction and internal fixation with fixed-angle plating
. Core decompression with vascularized fibular grafting
. Valgus intertrochanteric osteotomy
. Varus derotational osteotomy
. Total hip arthroplasty

Correct Answer & Explanation

. Valgus intertrochanteric osteotomy

Explanation

In a young patient with a viable femoral head and a femoral neck nonunion, a valgus intertrochanteric osteotomy is indicated. It predictably changes the vertically oriented nonunion site (shear forces) to a more horizontal orientation (compressive forces), promoting union.

Question 5057

Topic: 2. Trauma
An adult male sustains a Meyers-McKeever Type III displaced tibial eminence (spine) fracture. During attempted closed reduction or arthroscopic fixation, which of the following anatomic structures is most frequently found entrapped, blocking anatomical reduction?
. Posterior horn of the medial meniscus
. Anterior horn of the lateral meniscus
. Anterior horn of the medial meniscus
. Medial collateral ligament
. Infrapatellar fat pad

Correct Answer & Explanation

. Anterior horn of the medial meniscus

Explanation

The anterior horn of the medial meniscus, along with the intermeniscal (transverse) ligament, is the most common structure to become entrapped in a displaced tibial eminence fracture in adults, necessitating unblocking prior to definitive fixation.

Question 5058

Topic: 2. Trauma

A 70-year-old male presents with an AO/OTA 31-A3 (reverse obliquity) intertrochanteric femur fracture. Why is a sliding hip screw (DHS) considered a suboptimal implant for this specific fracture pattern?

. It prevents dynamic compression across the fracture site
. It provides inadequate fixation in osteoporotic cancellous bone
. It permits excessive lateral translation and medial displacement of the femoral shaft
. It inherently leads to varus collapse due to its fixed 135-degree angle
. It requires excessive reaming of the lateral femoral cortex

Correct Answer & Explanation

. It permits excessive lateral translation and medial displacement of the femoral shaft

Explanation

Reverse obliquity fractures (31-A3) lack an intact lateral cortical wall for support. A sliding hip screw allows the femoral shaft to displace medially as the lag screw slides, leading to severe lateral translation of the proximal fragment and construct failure.

Question 5059

Topic: 2. Trauma

A 55-year-old female presents with acute posterior knee pain after descending stairs, followed by an immediate pop. MRI demonstrates a medial meniscus posterior root tear and extrusion of the meniscus by 4 mm. What is the biomechanical consequence of this injury if left untreated?

. Increased peak contact pressures identical to a total meniscectomy
. Decreased anterior tibial translation
. Increased varus alignment without joint space narrowing
. Decreased risk of spontaneous osteonecrosis of the knee (SONK)
. Increased tensile stress on the ACL

Correct Answer & Explanation

. Increased peak contact pressures identical to a total meniscectomy

Explanation

A complete posterior root tear of the medial meniscus destroys the meniscal hoop stresses, leading to meniscal extrusion. Biomechanically, this makes the meniscus nonfunctional, leading to increased peak contact pressures in the medial compartment that are equivalent to the pressures seen after a total medial meniscectomy. This strongly predisposes the patient to rapid cartilage loss and subchondral insufficiency fractures.

Question 5060

Topic: 2. Trauma

A 40-year-old male sustains a closed, displaced intra-articular calcaneus fracture. When considering an extensile lateral approach for ORIF, which specific soft-tissue complication is most classically associated with this surgical exposure?

. Sural nerve injury and wound edge necrosis
. Tibial nerve entrapment
. Deep peroneal nerve palsy
. Medial plantar nerve injury
. Nonunion of the calcaneal tuberosity

Correct Answer & Explanation

. Sural nerve injury and wound edge necrosis

Explanation

The extensile lateral approach for calcaneus fractures relies on an L-shaped incision. The corner of the flap is highly susceptible to tip necrosis and wound dehiscence due to its blood supply (lateral calcaneal artery). Additionally, the sural nerve is directly in the surgical field and is at high risk of iatrogenic injury or neuroma formation.

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