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2. Trauma MCQs

Practice Set 465 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 9281

Topic: 2. Trauma

Which factor is most crucial in minimizing complications during distal locking of an intramedullary nail using a freehand technique?

. The patient's body habitus.
. The diameter of the intramedullary nail.
. The surgeon's experience and fluoroscopic proficiency.
. The use of a sterile tourniquet.
. The presence of intraoperative bone graft.

Correct Answer & Explanation

. The surgeon's experience and fluoroscopic proficiency.

Explanation

When using a freehand technique for distal locking, the surgeon's experience and proficiency with fluoroscopy are paramount. Accurate distal locking requires precise alignment of the drill, aiming for the nail's distal holes under multiple fluoroscopic views. This is a skill-intensive maneuver. While patient body habitus can make it more challenging (due to thicker soft tissue), and nail diameter influences hole size, the surgeon's technical skill and ability to interpret fluoroscopic images are the most crucial factors in successfully and safely placing the screws. A sterile tourniquet is for bloodless field, not specific to freehand locking. Bone graft is for nonunion, not locking.

Question 9282

Topic: 2. Trauma

What is the primary disadvantage of using a solid (unreamed) intramedullary nail compared to a cannulated (reamed) nail?

. Higher risk of infection due to the solid core.
. Difficulty in achieving precise length and rotation.
. Reduced bending and torsional stiffness.
. Increased likelihood of iatrogenic fracture during insertion.
. Requires more extensive surgical exposure.

Correct Answer & Explanation

. Reduced bending and torsional stiffness.

Explanation

A primary disadvantage of using a solid (unreamed) intramedullary nail is its reduced bending and torsional stiffness compared to a cannulated (reamed) nail of the same material. Because reaming allows for a larger diameter cannulated nail to be inserted, it significantly increases the moment of inertia and thus the strength of the construct. Solid nails are typically smaller in diameter, leading to less robust mechanical properties, which can be a concern in comminuted or unstable fractures. Solid nails do not inherently have a higher risk of infection, nor do they typically require more extensive exposure. Difficulty with length and rotation is more about technique than nail type itself. Iatrogenic fracture risk can be higher with reamed nails if not done carefully.

Question 9283

Topic: 2. Trauma

A patient with a comminuted distal femur fracture (AO/OTA 33-C3) is treated with a retrograde intramedullary nail. Which specific type of locking screw is often employed to enhance stability in the distal fragment?

. Dynamic locking screws.
. Blocking screws (poller screws).
. Convergent/Divergent locking screws.
. Compressive lag screws through the nail.
. Single cortical locking screws.

Correct Answer & Explanation

. Convergent/Divergent locking screws.

Explanation

For comminuted distal femur fractures, particularly those involving the metaphysis and epiphysis, convergent or divergent locking screws (multi-planar screws) are often employed. These screws diverge or converge within the short distal fragment, creating a broader base of fixation and providing enhanced stability against pullout, rotation, and angulation in the short, wide distal bone segment. This is critical for achieving and maintaining reduction. Dynamic locking screws are for axial compression, not multi-planar stability. Blocking screws are for guidewire/nail trajectory. Compressive lag screws are not typically placed through a retrograde nail to compress the fracture itself. Single cortical screws would provide inadequate fixation.

Question 9284

Topic: 2. Trauma
What is the main advantage of using an intramedullary nail for open tibial fractures (Gustilo-Anderson Types I, II, IIIA) over external fixation as definitive treatment?
. Lower incidence of pin tract infection.
. Ability to correct severe bone defects.
. Better preservation of soft tissue envelope.
. Faster time to union and lower nonunion rates.
. Easier wound care and dressings.

Correct Answer & Explanation

. Faster time to union and lower nonunion rates.

Explanation

For open tibial fractures (Gustilo-Anderson Types I, II, IIIA), intramedullary nailing, particularly unreamed, offers several advantages over external fixation as a definitive treatment. The main advantage is a faster time to union and lower nonunion rates. IM nails provide robust, internal stability, allowing for earlier weight-bearing and functional rehabilitation. While external fixation is crucial for severe soft tissue injuries (Type IIIB/C) or as a temporizing measure, its downsides include pin tract infections, slower union, and increased patient discomfort compared to definitive IM nailing. Pin tract infection risk is replaced by infection risk around the IM nail, but IM nailing still leads to better union. IM nailing is not primarily for correcting bone defects. External fixation allows for easier wound care, and IM nailing doesn't necessarily preserve the soft tissue envelope 'better' than an external fixator, but it allows for improved healing.

Question 9285

Topic: 2. Trauma

Which characteristic of an intramedullary nail is most important for stabilizing a fracture in osteoporotic bone?

. A flexible nail material to accommodate bone bowing.
. A smaller diameter nail to avoid iatrogenic fracture.
. Interlocking screws with improved pullout strength (e.g., larger thread pitch, locking to the nail).
. A long, straight nail that extends beyond the fracture by at least two cortical diameters.
. Cannulated design to allow for bone graft insertion.

Correct Answer & Explanation

. Interlocking screws with improved pullout strength (e.g., larger thread pitch, locking to the nail).

Explanation

In osteoporotic bone, the primary challenge is achieving and maintaining adequate fixation, as the bone itself provides poor purchase. Therefore, interlocking screws with improved pullout strength are most important. This includes features like larger thread pitch, multiple points of fixation, and bicortical purchase. Some nails also have specific designs for osteoporosis, such as cemented screws or expandable elements. A flexible nail would offer insufficient stability. A smaller diameter nail offers less stability. While long nails are often used to bypass stress risers, the quality of screw fixation is paramount. Cannulated design is common but not the most critical for stability in osteoporotic bone.

Question 9286

Topic: 2. Trauma

What is the primary indication for 'exchange nailing' in the setting of a healed femoral shaft fracture treated with an IM nail?

. Residual leg length discrepancy.
. Persistent pain at the entry site.
. Nonunion or delayed union.
. Malrotation of the healed fracture.
. Implant failure without nonunion.

Correct Answer & Explanation

. Nonunion or delayed union.

Explanation

The primary indication for 'exchange nailing' (removing the existing nail and inserting a larger diameter nail) is a nonunion or persistent delayed union of a femoral shaft fracture. This procedure aims to refresh the biological environment by reaming, increase the mechanical stability of the construct with a larger, stiffer nail, and potentially induce a biological response that promotes healing. While other complications can occur, exchange nailing is a specific intervention for nonunion/delayed union. Leg length discrepancy or malrotation are often managed with osteotomies or different approaches. Pain at the entry site might warrant removal of the nail or hardware but not necessarily exchange nailing unless nonunion is present. Implant failure without nonunion might indicate re-plating or a revision nailing but the question specified 'healed' in error, usually it refers to non-union.

Question 9287

Topic: 2. Trauma

Regarding the entry point for a tibial intramedullary nail, which statement correctly describes the goal?

. To be as medial as possible to avoid the patellar tendon.
. To be directly through the center of the patellar tendon.
. To be just medial to the lateral tibial spine, in line with the medullary canal.
. To be just lateral to the anterior tibial crest to avoid the extensor mechanism.
. To be distal to the tibial tuberosity.

Correct Answer & Explanation

. To be just medial to the lateral tibial spine, in line with the medullary canal.

Explanation

The ideal entry point for a tibial intramedullary nail is just medial to the lateral tibial spine or at the junction of the medial and central thirds of the intercondylar eminence. This entry point allows a straight shot down the medullary canal, minimizes damage to the articular cartilage, and avoids creating excessive valgus or varus angulation. Being too medial or too lateral can cause iatrogenic fracture or malalignment. Directing it through the center of the patellar tendon can cause pain. Distal to the tibial tuberosity is too low and would create a procurvatum deformity.

Question 9288

Topic: 2. Trauma

A 60-year-old male with a comminuted mid-shaft humerus fracture is undergoing antegrade IM nailing. What is the most critical step to prevent malreduction in the sagittal plane?

. Using a large diameter nail to fill the canal.
. Applying distal traction to lengthen the arm.
. Careful patient positioning to avoid shoulder flexion.
. Achieving and maintaining good reduction during reaming and nail insertion.
. Using multiple proximal locking screws.

Correct Answer & Explanation

. Achieving and maintaining good reduction during reaming and nail insertion.

Explanation

For comminuted mid-shaft humerus fractures treated with antegrade IM nailing, achieving and maintaining good reduction, particularly in the sagittal plane (avoiding apex anterior or posterior angulation), is the most critical step. The humerus has an anterior bow, and a straight nail must be guided carefully. This often requires careful manipulation, gravity assistance, or even temporary external fixation devices to hold the reduction while the nail is inserted. A large diameter nail provides stability but doesn't guarantee reduction. Distal traction is for length. Patient positioning helps, but active reduction is key. Multiple proximal locking screws provide rotational stability, not sagittal alignment.

Question 9289

Topic: 2. Trauma

Which type of fracture is typically considered unsuitable for intramedullary nailing and would be better treated with plate osteosynthesis or arthroplasty?

. Transverse mid-shaft femoral fracture.
. Unstable intertrochanteric hip fracture.
. Highly comminuted supracondylar femoral fracture with articular involvement.
. Segmental tibial shaft fracture.
. Spiral humeral shaft fracture.

Correct Answer & Explanation

. Highly comminuted supracondylar femoral fracture with articular involvement.

Explanation

Highly comminuted supracondylar femoral fractures with significant articular involvement (e.g., distal femur C2, C3 fractures) are generally unsuitable for intramedullary nailing. IM nails are primarily designed for diaphyseal or metaphyseal fractures where the nail can bridge and stabilize the fragments. Articular involvement often requires anatomical reduction and absolute stability, which is better achieved with plate osteosynthesis (e.g., locking plates) that can directly fix the articular fragments. In severe cases, arthroplasty might be considered. Other fracture types listed (transverse femoral shaft, unstable intertrochanteric, segmental tibial, spiral humeral) are all well-suited for IM nailing.

Question 9290

Topic: 2. Trauma

What is a major advantage of retrograde femoral nailing compared to antegrade nailing for a distal femur fracture?

. Lower risk of iatrogenic hip pain.
. Easier access for patients in a supine position.
. Better control of the proximal fragment.
. Reduced risk of fat embolism.
. Less damage to the quadriceps mechanism.

Correct Answer & Explanation

. Lower risk of iatrogenic hip pain.

Explanation

A major advantage of retrograde femoral nailing, particularly for distal femur fractures, is a lower risk of iatrogenic hip pain. Antegrade nails often cause pain related to the entry point at the greater trochanter or piriformis fossa. Retrograde nailing avoids this by using a knee-based entry point. While it can be done supine, it often requires a lateral position. Control of the proximal fragment is often more challenging with retrograde nails, and it doesn't necessarily reduce fat embolism risk more than antegrade. It involves an incision in the knee and can cause knee pain/stiffness, so it's not 'less damage' to the quadriceps mechanism, but different damage.

Question 9291

Topic: 2. Trauma

Which of the following is considered a biomechanical benefit of inserting a larger diameter intramedullary nail by over-reaming in cases of nonunion?

. Decreased endosteal blood supply to the nonunion site.
. Increased implant flexibility, promoting micromotion.
. Increased stiffness of the construct, enhancing stability.
. Reduced axial load transfer through the fracture.
. A tighter fit that prevents dynamization.

Correct Answer & Explanation

. Increased stiffness of the construct, enhancing stability.

Explanation

In cases of nonunion, exchange nailing with over-reaming and insertion of a larger diameter nail is a common strategy. The primary biomechanical benefit is the increased stiffness of the construct. A larger diameter nail dramatically increases the nail's moment of inertia, providing enhanced bending and torsional stability. This increased stiffness helps to overcome the mechanical instability often contributing to nonunion. Over-reaming also stimulates a biological response, enhancing endosteal blood supply. Increased implant flexibility is undesirable. It promotes axial load transfer, not reduces it. A tighter fit doesn't necessarily prevent dynamization but ensures better stability.

Question 9292

Topic: Lower Extremity Trauma

When positioning a patient for antegrade femoral intramedullary nailing, what is the rationale for placing the hip in adduction and internal rotation?

. To facilitate distal locking screw placement.
. To relax the iliopsoas muscle and aid in proximal fragment alignment.
. To expose the greater trochanter for the entry point.
. To reduce the risk of neurovascular injury in the groin.
. To allow the C-arm to obtain true AP and lateral views of the hip.

Correct Answer & Explanation

. To expose the greater trochanter for the entry point.

Explanation

Placing the hip in adduction and internal rotation is done to bring the greater trochanter into a more accessible position and to align the piriformis fossa or trochanteric entry point with the axis of the femoral canal. This facilitates exposure of the greater trochanter and ensures a more direct path for the guidewire and nail into the medullary canal. While it can indirectly help with C-arm views, the primary direct reason is entry point access and alignment. It doesn't primarily relax the iliopsoas (traction does that). Distal locking is unrelated. Neurovascular injury is not directly mitigated by this positioning in the groin.

Question 9293

Topic: 2. Trauma

What is the most appropriate initial management for a stable patient with a closed femoral shaft fracture and an associated ipsilateral tibial shaft fracture (floating knee injury)?

. External fixation of both fractures, followed by delayed IM nailing.
. Immediate intramedullary nailing of both femur and tibia in the same setting.
. Plate fixation of the femur and IM nailing of the tibia.
. IM nailing of the femur, followed by cast immobilization of the tibia.
. Observation and non-operative management if pain is tolerable.

Correct Answer & Explanation

. Immediate intramedullary nailing of both femur and tibia in the same setting.

Explanation

For a stable patient with a floating knee injury (ipsilateral femoral and tibial shaft fractures), the most appropriate initial management is immediate intramedullary nailing of both the femur and tibia in the same setting. This 'simultaneous nailing' approach allows for early mobilization, improved outcomes, and reduced complications compared to staged procedures or less stable fixation methods. While external fixation might be used for damage control in unstable patients, definitive IM nailing is preferred for stable patients. Plate fixation of the femur is generally less favored than IM nailing for shaft fractures. Casting the tibia would provide inadequate stability for a floating knee. Observation is not an option for unstable long bone fractures.

Question 9294

Topic: 2. Trauma

In the context of infection following intramedullary nailing, which of the following scenarios often warrants implant retention with debridement and antibiotics rather than immediate nail removal?

. Early acute infection with signs of systemic sepsis and loose implant.
. Chronic infection with exposed metal and draining sinus.
. Late infection with definitive nonunion and widespread osteomyelitis.
. Acute infection within 2-4 weeks post-op, with stable implant and early signs of healing.
. Superficial wound infection without deep involvement.

Correct Answer & Explanation

. Acute infection within 2-4 weeks post-op, with stable implant and early signs of healing.

Explanation

Acute infection within 2-4 weeks post-op, in the presence of a stable implant and early signs of healing, often warrants a trial of aggressive debridement, irrigation, and culture-directed intravenous antibiotics while retaining the nail. The goal is to eradicate the infection while preserving the fixation necessary for fracture healing. If the implant is loose, the infection is chronic, or there's definitive nonunion, implant removal (often with exchange nailing or alternative fixation) is usually necessary. Superficial wound infection without deep involvement is managed with local wound care and oral antibiotics, not necessarily debridement or IV antibiotics and definitely not nail removal.

Question 9295

Topic: 2. Trauma

When utilizing a screw in a 'buttress' fashion, what is its main biomechanical role?

. To provide interfragmentary compression across an oblique fracture.
. To resist shear forces that would cause collapse or displacement of a fragment.
. To allow controlled micromotion to stimulate bone healing.
. To maintain fracture reduction by acting as a tension band.
. To facilitate immediate weight-bearing in comminuted fractures.

Correct Answer & Explanation

. To resist shear forces that would cause collapse or displacement of a fragment.

Explanation

A buttress plate (or screw acting as a buttress) is typically placed on the tension side of a fracture or used to prevent collapse of metaphyseal fragments under axial load. Its primary role is to resist shear or compressive forces that would otherwise cause a fragment to displace or collapse. It 'buttresses' the fragment, preventing it from migrating. This is distinct from providing interfragmentary compression or acting as a tension band.

Question 9296

Topic: 2. Trauma

A 30-year-old active patient sustains a midshaft clavicle fracture with significant shortening. You decide to fix it with a plate and screws. What is the appropriate drill bit size for the thread hole for a 3.5 mm cortical screw?

. 2.0 mm
. 2.5 mm
. 3.0 mm
. 3.5 mm
. 4.5 mm

Correct Answer & Explanation

. 2.5 mm

Explanation

For a standard 3.5 mm cortical screw, the thread hole (pilot hole for the screw threads) requires a 2.5 mm drill bit. This matches the core diameter of the 3.5 mm cortical screw. If a lag screw technique is employed using a 3.5 mm cortical screw, the gliding hole in the near cortex would be 3.5 mm, while the far cortex thread hole remains 2.5 mm. The options are 0-indexed, so 2.5mm is at index 1.

Question 9297

Topic: 2. Trauma

In a tension band wiring construct for patella fracture, what is the biomechanical role of the K-wires and the figure-of-eight wire?

. K-wires provide primary compression, while the wire acts as a neutralization device.
. K-wires provide rotational stability, while the wire converts tensile forces into compression.
. K-wires prevent bending, while the wire provides a buttress effect.
. K-wires function as lag screws, while the wire prevents shear.
. K-wires stabilize bone fragments, and the wire distributes axial load.

Correct Answer & Explanation

. K-wires provide rotational stability, while the wire converts tensile forces into compression.

Explanation

In a tension band construct (e.g., for patella or olecranon fractures), the K-wires (or sometimes small screws) act as intramedullary fixation, preventing displacement and rotation of the fragments. The figure-of-eight wire, placed anteriorly on the tension side, converts the distractive (tensile) forces that would otherwise open the fracture on the tension side into compressive forces across the articular (compression) side during joint movement. This dynamic compression promotes healing.

Question 9298

Topic: 2. Trauma

When fixing a lateral malleolus fracture with a standard one-third tubular plate, what is the recommended minimum number of cortices that should be engaged by screws distal and proximal to the fracture?

. Two cortices distal, two cortices proximal.
. Four cortices distal, four cortices proximal.
. Six cortices distal, six cortices proximal.
. Eight cortices distal, eight cortices proximal.
. Three cortices distal, three cortices proximal.

Correct Answer & Explanation

. Four cortices distal, four cortices proximal.

Explanation

For most plate fixation of fractures, especially in non-locking constructs, the general principle is to have at least two screws engaging a minimum of four cortices on each side of the fracture. For example, two bicortical screws (each engaging two cortices, near and far) distal to the fracture and two bicortical screws proximal to the fracture provides 4 cortices of purchase distal and 4 cortices proximal. Therefore, a minimum of 4 cortices (2 screws) distal and 4 cortices (2 screws) proximal should be engaged. The question asks for 'number of cortices', not 'number of screws'. So 4 cortices distal and 4 cortices proximal.

Question 9299

Topic: 2. Trauma

A surgeon is evaluating screw lengths for a transcervical femoral neck fracture fixation using three cannulated screws. Which of the following is a critical principle for optimal screw placement and length?

. All screws must be fully buried within the femoral head, without protruding subchondrally.
. Screws should extend just beyond the fracture line into the femoral head, avoiding the subchondral bone.
. Screws must breach the subchondral bone of the femoral head by 5-10 mm for maximum purchase.
. The longest screw should be placed inferiorly to resist shear forces.
. Screw length should always be measured with a depth gauge from the lateral cortex to the fracture line.

Correct Answer & Explanation

. All screws must be fully buried within the femoral head, without protruding subchondrally.

Explanation

For femoral neck fractures, it is crucial that the screws gain purchase in the dense subchondral bone of the femoral head but do not violate the articular surface. Optimal placement involves extending the screw tips into the femoral head to within 5-10 mm of the subchondral bone, or just engaging it, but certainly not breaching it. The goal is to maximize purchase without causing articular damage or future hardware prominence. Option A states 'without protruding subchondrally' which implies 'not breaching the articular surface' which is correct for optimal purchase and avoiding joint irritation. Option B implies avoiding subchondral bone completely, which would compromise purchase. Option C explicitly states breaching the subchondral bone, which is incorrect as it implies violating the articular surface.

Question 9300

Topic: 2. Trauma

A 4.5 mm cortical screw has a major diameter of 4.5 mm and a core diameter of 3.2 mm. For a lag screw technique, what size drill bit is typically used for the gliding hole in the near cortex?

. 2.5 mm
. 3.2 mm
. 4.5 mm
. 6.5 mm
. 5.0 mm

Correct Answer & Explanation

. 4.5 mm

Explanation

To create a gliding hole in the near cortex for a lag screw, the drill bit size must be equal to or slightly larger than the major (outer) diameter of the screw. This allows the screw threads to pass freely through the near cortex without engaging, thus enabling the screw head to compress the near fragment against the far fragment where the threads engage. For a 4.5 mm cortical screw, the gliding hole should be 4.5 mm. The thread hole in the far cortex would be 3.2 mm (matching the core diameter).

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