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2. Trauma MCQs

Practice Set 105 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 2081

Topic: 2. Trauma

A 35-year-old male sustains a comminuted mid-shaft femoral fracture. An unreamed intramedullary nail is inserted. Which biomechanical principle is primarily leveraged by the unreamed technique in this scenario?

. Maximizing cortical contact for rotational stability.
. Preserving endosteal blood supply to enhance fracture healing.
. Increasing the stiffness of the nail-bone construct.
. Facilitating early weight-bearing due to increased implant strength.
. Reducing the risk of thermal necrosis during insertion.

Correct Answer & Explanation

. Preserving endosteal blood supply to enhance fracture healing.

Explanation

Correct Answer: BUnreamed nailing, while potentially leading to a smaller diameter nail, preserves the endosteal blood supply, which is critical for bone healing, especially in comminuted fractures where periosteal blood supply may also be compromised. Reaming can damage the endosteal vessels, potentially impairing healing. While rotational stability, stiffness, and early weight-bearing are important aspects of IM nailing, the primary biomechanical advantage of unreamed nailing, particularly in the context of comminution, is blood supply preservation.

Question 2082

Topic: Lower Extremity Trauma

Regarding intramedullary nail design, increasing the nail's diameter primarily enhances its resistance to what type of biomechanical force?

. Axial compression.
. Torsional loads.
. Bending moments.
. Shear stress.
. Distraction forces.

Correct Answer & Explanation

. Bending moments.

Explanation

Correct Answer: CIncreasing the diameter of an intramedullary nail significantly enhances its moment of inertia, which is the key determinant of a structure's resistance to bending. The resistance to bending is proportional to the fourth power of the radius (or diameter), making diameter a critical factor for bending stiffness. While diameter also affects torsional stiffness, its most dramatic effect is on bending resistance. Axial compression resistance is primarily determined by the cross-sectional area, and shear stress resistance is also influenced by diameter but not as profoundly as bending.

Question 2083

Topic: 2. Trauma

A long, oblique tibial shaft fracture is treated with an intramedullary nail. Post-operatively, the fracture demonstrates excessive shortening. Which biomechanical factor is most likely contributing to this complication?

. Inadequate nail diameter relative to the medullary canal.
. Insufficient number of distal locking screws.
. Working length of the nail-bone construct is too short.
. Presence of a significant fracture gap.
. Locking screws placed in dynamic mode rather than static.

Correct Answer & Explanation

. Presence of a significant fracture gap.

Explanation

Correct Answer: DExcessive shortening in an oblique fracture treated with an IM nail, especially after fixation, strongly suggests a loss of interfragmentary contact and a significant fracture gap, allowing the oblique surfaces to slide past each other. This often occurs when the fracture reduction is not adequately maintained during nail insertion or if there's significant comminution not accounted for. While other factors like inadequate locking can contribute to instability, a large fracture gap in an oblique fracture directly facilitates shortening. The working length concept primarily affects bending stiffness and interfragmentary strain, not directly shortening due to lack of contact. Dynamic locking would allow controlled shortening, but 'excessive' suggests uncontrolled shortening due to poor reduction or fixation failure.

Question 2084

Topic: 2. Trauma

Which biomechanical advantage is specifically offered by the use of multiplanar interlocking screws in an intramedullary nail system for a proximal femoral fracture?

. Enhanced load sharing across the fracture site.
. Increased bending stiffness of the nail.
. Superior resistance to torsional forces.
. Improved biological healing due to less reaming.
. Reduced risk of stress shielding in the distal fragment.

Correct Answer & Explanation

. Increased bending stiffness of the nail.

Explanation

Correct Answer: CMultiplanar interlocking screws (e.g., in a cephalomedullary nail) provide superior resistance to bending moments, particularly in unstable metaphyseal or comminuted fractures where the bone offers less support to the nail. By engaging cortical bone at different angles and planes, they create a broader base of support, effectively increasing the stability of the implant-bone construct against bending and axial rotation. While they contribute to overall stability and thus indirectly to load sharing and resistance to torsion, their primary biomechanical advantage in these complex proximal fractures is mitigating bending forces that often lead to construct failure or malunion.

Question 2085

Topic: 2. Trauma

In the context of IM nailing, what is the primary purpose of 'relative stability' at a fracture site?

. To completely eliminate interfragmentary motion.
. To promote direct bone healing (primary healing).
. To allow controlled interfragmentary motion that stimulates callus formation.
. To ensure rigid fixation allowing immediate full weight-bearing.
. To minimize stress shielding of the bone.

Correct Answer & Explanation

. To allow controlled interfragmentary motion that stimulates callus formation.

Explanation

Correct Answer: CRelative stability, characteristic of IM nailing, allows for controlled, limited interfragmentary motion. This micromotion, when within a specific biological window of interfragmentary strain (2-10%), is crucial for stimulating secondary bone healing through callus formation. Complete elimination of motion (absolute stability) promotes direct healing but is typically achieved with plates using lag screws and compression. IM nails, by their nature, provide relative stability and load-sharing.

Question 2086

Topic: 2. Trauma

A reamed IM nail is used for a segmental tibial fracture. What is the potential biomechanical drawback of a nail that is excessively stiff for the fracture pattern?

. Increased risk of infection due to reaming debris.
. Promotion of hypertrophic non-union.
. Increased likelihood of stress shielding, hindering bone healing.
. Reduced rotational stability in the proximal fragment.
. Premature dynamization of the construct.

Correct Answer & Explanation

. Increased likelihood of stress shielding, hindering bone healing.

Explanation

Correct Answer: CAn excessively stiff nail can lead to significant stress shielding. Stress shielding occurs when the implant carries a disproportionate amount of the load, reducing the stress experienced by the bone. Bone requires physiological stress to remodel and heal effectively (Wolff's Law). Reduced stress can inhibit callus formation and maturation, potentially leading to delayed union or non-union, or even osteopenia around the implant. While hypertrophic non-union is characterized by abundant callus but no bridging, it's often due to excessive motion, not excessive stiffness. Atrophic non-union is more associated with stress shielding. The term 'hindering bone healing' encompasses the effect of stress shielding.

Question 2087

Topic: 2. Trauma

When considering the insertion of an intramedullary nail, which factor most directly influences the 'working length' of the construct?

. The material composition of the nail (e.g., stainless steel vs. titanium).
. The number of locking screws used at each end.
. The distance between the most proximal and most distal locking screws.
. The reaming diameter compared to the nail diameter.
. The nail's cross-sectional geometry.

Correct Answer & Explanation

. The distance between the most proximal and most distal locking screws.

Explanation

Correct Answer: CThe working length of an intramedullary nail construct is defined by the distance between the most proximal and most distal locking screws. A longer working length generally allows for more flexibility and a lower interfragmentary strain, which can be beneficial for healing in comminuted fractures, but may decrease overall construct stiffness. A shorter working length increases stiffness but can lead to higher stress concentrations at the screw-bone interface. This concept is crucial for understanding load transfer and micromotion at the fracture site.

Question 2088

Topic: 2. Trauma

Which biomechanical characteristic is a primary advantage of intramedullary nails over compression plating for a diaphyseal fracture?

. Absolute stability at the fracture site.
. Direct anatomical reduction.
. Load sharing capabilities.
. Minimized soft tissue stripping.
. Superior resistance to bending in all planes.

Correct Answer & Explanation

. Load sharing capabilities.

Explanation

Correct Answer: CIntramedullary nails are load-sharing devices. They bear a portion of the physiological load, allowing the bone to also experience stress, which is conducive to secondary bone healing. Plates, especially compression plates, are load-bearing devices, which initially carry the entire load across the fracture, leading to absolute stability and direct bone healing, but also a higher risk of stress shielding. Minimized soft tissue stripping is a surgical advantage, not a direct biomechanical characteristic of the construct itself. Nails offer relative stability, not absolute. While nails resist bending, their resistance is not necessarily superior in all planes compared to meticulously applied plates with strong cortical contact.

Question 2089

Topic: 2. Trauma

A patient with a comminuted distal tibial metaphyseal fracture is treated with an intramedullary nail. What is the most critical biomechanical challenge in achieving stable fixation in this region with an IM nail?

. Maintaining rotational control due to the broad cancellous bone.
. Achieving adequate purchase of locking screws in the osteoporotic metaphysis.
. Controlling shortening and varus/valgus alignment due to lack of intramedullary bone for nail engagement.
. Preventing stress shielding of the distal fragment.
. Minimizing thermal necrosis during reaming.

Correct Answer & Explanation

. Achieving adequate purchase of locking screws in the osteoporotic metaphysis.

Explanation

Correct Answer: BDistal tibial metaphyseal fractures present a significant challenge for IM nailing primarily due to the widening medullary canal and the thin cortices, especially in osteoporotic patients. This makes it difficult to achieve adequate purchase with distal locking screws, leading to potential loss of reduction, particularly in varus/valgus and shortening. The nail itself often 'floats' in the wide canal without good bone-nail contact, making screw fixation paramount. While rotational control and shortening are concerns, the fundamental issue is the poor screw purchase in the metaphyseal bone, making reliable fixation difficult.

Question 2090

Topic: 2. Trauma

Dynamization of an intramedullary nail is performed in a delayed union. What is the primary biomechanical goal of this procedure?

. To increase the stiffness of the implant-bone construct.
. To convert static locking to absolute stability.
. To increase axial load transfer across the fracture site.
. To reduce rotational forces at the fracture site.
. To decrease interfragmentary strain.

Correct Answer & Explanation

. To increase axial load transfer across the fracture site.

Explanation

Correct Answer: CDynamization, typically achieved by removing one set of locking screws (often the static screws), converts the statically locked construct into one that allows for controlled axial micromotion. This increased axial load transfer and controlled interfragmentary compression (within the appropriate biological window of strain) is intended to stimulate callus formation and accelerate healing in delayed unions. It essentially allows the bone to experience more physiological loading, thus promoting consolidation.

Question 2091

Topic: 2. Trauma

A 45-year-old male presents with a closed Schatzker Type V tibial plateau fracture that extends into the diaphysis. Which of the following fixation strategies is generally considered most appropriate for simultaneous stabilization of both components in a single surgical setting?

. A. Open reduction and internal fixation (ORIF) with a medial buttress plate.
. B. External fixation followed by staged intramedullary nailing.
. C. Limited open reduction and percutaneous screw fixation of the articular surface combined with a retrograde intramedullary nail.
. D. Dual plating with an anterior and posterior plate.
. E. Non-weight bearing cast immobilization for 12 weeks.

Correct Answer & Explanation

. C. Limited open reduction and percutaneous screw fixation of the articular surface combined with a retrograde intramedullary nail.

Explanation

Correct Answer: CFor a Schatzker Type V tibial plateau fracture extending into the diaphysis (tibial shaft), a retrograde intramedullary nail combined with percutaneous or limited open reduction and screw fixation for the articular component is often the preferred method. This approach allows for rigid fixation of the shaft component with the nail, preserves the biological environment, and provides stable support for the articular reconstruction. Medial buttress plating alone (A) is insufficient for a Type V and diaphyseal extension. Staged fixation (B) is an option but a single-stage approach is often preferred if feasible. Dual plating (D) is more invasive and may compromise soft tissues. Cast immobilization (E) is inadequate for such an unstable fracture.

Question 2092

Topic: 2. Trauma

Regarding the biomechanics of intramedullary nailing for long bone fractures, what is the primary advantage of a locked nail over a non-locked nail?

. A. Greater resistance to axial compression.
. B. Enhanced load sharing capabilities.
. C. Prevention of rotation and shortening.
. D. Reduced risk of infection.
. E. Promotion of primary bone healing.

Correct Answer & Explanation

. C. Prevention of rotation and shortening.

Explanation

Correct Answer: CThe primary advantage of a locked intramedullary nail is its ability to prevent rotation and shortening at the fracture site. Locking screws, placed proximally and/or distally, convert the nail into a load-bearing construct that controls all planes of motion, crucial for unstable fractures and those where length and rotation must be maintained. While nails inherently offer load sharing (B) and resistance to axial compression (A), locking mechanisms specifically address rotational and translational stability. Nailing primarily promotes secondary bone healing (E), not primary. Locking itself does not reduce infection risk (D).

Question 2093

Topic: 2. Trauma
Which of the following conditions is an absolute contraindication to reamed intramedullary nailing of a femoral shaft fracture?
. Open Gustilo-Anderson Type IIIA fracture.
. Polytrauma patient with significant pulmonary compromise (ARDS).
. Ipsilateral femoral neck fracture.
. Pre-existing knee osteoarthritis.
. Bone loss exceeding 5 cm at the fracture site.

Correct Answer & Explanation

. Polytrauma patient with significant pulmonary compromise (ARDS).

Explanation

Severe pulmonary compromise, particularly Acute Respiratory Distress Syndrome (ARDS), represents an absolute contraindication to reamed intramedullary nailing due to the significant risk of exacerbating fat embolism syndrome and further compromising lung function. The increased intramedullary pressure during reaming can drive fat emboli into the systemic circulation.

Question 2094

Topic: Lower Extremity Trauma

When performing retrograde intramedullary nailing for a distal femur fracture, what is the most critical anatomical consideration to prevent iatrogenic knee injury?

. A. Avoiding injury to the superior genicular artery.
. B. Ensuring proper entry point to prevent damage to the intercondylar notch and articular cartilage.
. C. Protecting the common peroneal nerve laterally.
. D. Preventing disruption of the posterior cruciate ligament attachment.
. E. Minimizing periosteal stripping during exposure.

Correct Answer & Explanation

. B. Ensuring proper entry point to prevent damage to the intercondylar notch and articular cartilage.

Explanation

Correct Answer: BThe most critical anatomical consideration when performing retrograde intramedullary nailing of the distal femur is ensuring the correct entry point to prevent damage to the intercondylar notch, articular cartilage, and potential compromise of the anterior cruciate ligament (ACL) insertion site. An incorrect entry point can lead to chondral damage, knee pain, and functional impairment. While protecting nerves (C) and minimizing soft tissue stripping (E) are important general principles, the specific challenge with retrograde nailing is the intra-articular entry. The genicular arteries (A) are less of a concern than articular damage. PCL attachment (D) is posterior and generally not at risk with standard entry.

Question 2095

Topic: Lower Extremity Trauma

Following reamed intramedullary nailing of a tibial shaft fracture, a patient develops anterior knee pain. What is the most common cause of this complication?

. A. Osteoarthritis of the patellofemoral joint.
. B. Impingement of the proximal locking screws on the patellar tendon.
. C. Patellar tendon irritation from the nail entry portal.
. D. Neuroma formation in the infrapatellar branch of the saphenous nerve.
. E. Avascular necrosis of the patella.

Correct Answer & Explanation

. C. Patellar tendon irritation from the nail entry portal.

Explanation

Correct Answer: CAnterior knee pain is a well-known complication of tibial intramedullary nailing. The most common cause is irritation or impingement of the patellar tendon by the proximal end of the nail, or by prominent proximal locking screws. While infrapatellar nerve injury (D) can cause numbness and sometimes pain, and osteoarthritis (A) can be a pre-existing condition, the direct mechanical irritation by the hardware is the most frequent cause of post-operative anterior knee pain related to the nailing procedure itself. Avascular necrosis of the patella (E) is exceedingly rare.

Question 2096

Topic: 2. Trauma

Which of the following fracture patterns is generally considered the most challenging to stabilize adequately with a standard antegrade femoral intramedullary nail due to inherent biomechanical limitations?

. A. Transverse mid-diaphyseal fracture.
. B. Segmental fracture of the femoral shaft.
. C. Highly comminuted subtrochanteric fracture.
. D. Short oblique fracture in the distal third of the femur.
. E. Spiral fracture of the proximal diaphysis.

Correct Answer & Explanation

. C. Highly comminuted subtrochanteric fracture.

Explanation

Correct Answer: CHighly comminuted subtrochanteric fractures (C) are often the most challenging to stabilize with a standard antegrade femoral intramedullary nail. The wide medullary canal in the metaphysis, coupled with severe comminution, makes it difficult to achieve adequate cortical purchase proximally and prevent varus collapse or shortening, even with multiple locking screws. While other fracture patterns have their challenges, the unique anatomy and forces at the subtrochanteric region amplify the difficulty. Newer generation nails with improved proximal locking options have mitigated this somewhat, but it remains a significant biomechanical challenge. Transverse (A) and spiral (E) diaphyseal fractures, and segmental fractures (B) are generally well-managed. Distal third fractures (D) may pose entry point challenges but are typically manageable.

Question 2097

Topic: 2. Trauma

What is the primary function of blocking screws (Poller screws) in intramedullary nailing?

. A. To prevent nail migration during weight-bearing.
. B. To enhance the rotational stability of the nail in osteoporotic bone.
. C. To narrow the medullary canal and facilitate central nail placement and achieve better fracture reduction.
. D. To secure bone grafts to the nail in cases of bone loss.
. E. To allow dynamic locking in short oblique fractures.

Correct Answer & Explanation

. C. To narrow the medullary canal and facilitate central nail placement and achieve better fracture reduction.

Explanation

Correct Answer: CBlocking screws (Poller screws) are placedoutsidethe path of the intramedullary nail butwithinthe medullary canal, typically at the metaphysis. Their primary function is to narrow the medullary canal at specific points, thereby guiding the nail centrally into the desired position, preventing malalignment (e.g., translation, angulation), and improving fracture reduction and stability, especially in wide canals or metaphyseal extensions. They do not prevent nail migration (A), directly enhance rotational stability (B) like locking screws, secure grafts (D), or specifically allow dynamic locking (E).

Question 2098

Topic: 2. Trauma

What is the primary rationale for routinely performing reaming during intramedullary nailing for most diaphyseal long bone fractures?

. A. To minimize surgical blood loss.
. B. To create a tight fit for a larger, stiffer nail.
. C. To reduce the risk of infection by removing necrotic tissue.
. D. To preserve the endosteal blood supply.
. E. To facilitate removal of the guide wire.

Correct Answer & Explanation

. B. To create a tight fit for a larger, stiffer nail.

Explanation

Correct Answer: BThe primary rationale for routinely performing reaming is to allow for the insertion of a larger diameter intramedullary nail. A larger nail dramatically increases the stiffness and strength of the implant (stiffness is proportional to the radius to the fourth power, r^4), which creates a more stable construct and improves fatigue life. This translates to a tighter fit (B) and superior biomechanical stability. While reaming transiently disrupts endosteal blood supply (D), the overall benefits for stability and healing outweigh this. Reaming doesn't primarily reduce blood loss (A) or infection risk (C) in this context. It's not for guide wire removal (E).

Question 2099

Topic: Lower Extremity Trauma

What is the most common cause of malrotation following intramedullary nailing of a femoral shaft fracture?

. A. Incorrect entry portal for the nail.
. B. Failure to restore the anatomical anteversion of the proximal femur during reduction.
. C. Distal locking screws placed inaccurately.
. D. Lack of intraoperative fluoroscopy.
. E. Post-operative muscle spasm.

Correct Answer & Explanation

. B. Failure to restore the anatomical anteversion of the proximal femur during reduction.

Explanation

Correct Answer: BMalrotation, particularly internal rotation deformity, is a common and often functionally significant complication after femoral intramedullary nailing. The most common cause is the failure to restore the anatomical anteversion of the proximal and distal femur during reduction and fixation. Intraoperative assessment of rotation (e.g., foot position, lesser trochanter profile, cortical step sign, C-arm techniques) is crucial. Incorrect entry portal (A) can cause malalignment, but not primarily malrotation. Distal locking (C) affects length and angulation more directly. While fluoroscopy (D) aids in visualization, it's theinterpretation and useof that information for rotational assessment that is key.

Question 2100

Topic: Lower Extremity Trauma

What is the primary objective of obtaining an 'axial view' or 'ski tip view' of the distal femur during retrograde intramedullary nailing?

. A. To assess the entry point in the intercondylar notch.
. B. To confirm the rotational alignment of the distal fragment.
. C. To visualize and protect the popliteal neurovascular bundle.
. D. To ensure adequate distal locking screw placement.
. E. To assess for fracture propagation into the articular surface.

Correct Answer & Explanation

. D. To ensure adequate distal locking screw placement.

Explanation

Correct Answer: DThe 'axial view' or 'ski tip view' of the distal femur is crucial during retrograde intramedullary nailing to ensure proper distal locking screw placement (D). This view provides an orthogonal projection to the standard AP and lateral, allowing the surgeon to confirm that the screws are fully engaging the distal cortex and are within the bone, without exiting into soft tissues or the knee joint. It also helps to prevent nerve and vessel injury. While entry point (A) and articular surface assessment (E) are important, the ski tip view is specifically for confirming the distal locking.

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