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2. Trauma MCQs

Practice Set 461 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 9201

Topic: 2. Trauma

In the application of a locking plate for a metaphyseal fracture, what is the recommended minimum number of locking screws that should be placed in each main fragment (proximal and distal) to ensure adequate stability?

. One screw
. Two screws
. Three screws
. Four screws
. Five screws

Correct Answer & Explanation

. Three screws

Explanation

The general recommendation for adequate stability with a locking plate construct is to place at least three locking screws in each main fragment. This provides sufficient purchase and prevents rotation or pull-out, especially in the often-osteopenic metaphysis. While two screws can provide some stability against bending, three screws are typically recommended to resist bending, torsion, and pullout effectively, forming a stable fixed-angle construct. For very short fragments, sometimes two are used, but three is the ideal minimum for robust fixation.

Question 9202

Topic: 2. Trauma
Which of the following scenarios is a relative contraindication for the use of a minimally invasive plate osteosynthesis (MIPO) technique?
. A simple transverse diaphyseal fracture of the tibia.
. An open fracture (Gustilo-Anderson Type IIIA) with significant soft tissue stripping.
. A comminuted distal femur fracture in an elderly osteoporotic patient.
. A non-union of the humeral shaft requiring autogenous bone grafting.
. A periprosthetic femur fracture around a total hip arthroplasty stem.

Correct Answer & Explanation

. An open fracture (Gustilo-Anderson Type IIIA) with significant soft tissue stripping.

Explanation

An open fracture with significant soft tissue stripping (Gustilo-Anderson Type IIIA) would be a relative contraindication for MIPO. While MIPO aims to preserve soft tissue and blood supply, in an already compromised open fracture site, direct visualization may be critical for debridement, assessment of fracture geometry, and managing contamination. Furthermore, the existing soft tissue damage negates some of the primary advantages of MIPO. MIPO is very well suited for simple diaphyseal fractures, comminuted metaphyseal/diaphyseal fractures, non-unions, and periprosthetic fractures to preserve the critical periosteal blood supply and minimize further soft tissue damage.

Question 9203

Topic: 2. Trauma

Which statement best describes the 'working length' of a plate-screw construct and its biomechanical implication?

. It refers to the total length of the plate that spans the fracture site.
. It is the distance between the two innermost screws on either side of the fracture, directly influencing construct stiffness.
. It represents the number of screws placed within the main fragments, correlating with construct strength.
. It is the length of the plate segment directly over the fracture, determining bone healing time.
. It describes the distance from the plate to the bone surface, impacting periosteal blood flow.

Correct Answer & Explanation

. It is the distance between the two innermost screws on either side of the fracture, directly influencing construct stiffness.

Explanation

The working length of a plate construct is the length of the plate segment that is not rigidly fixed to the bone, essentially the distance between the innermost screws on either side of the fracture. A longer working length (fewer screws near the fracture, screws placed further from the fracture) reduces the stiffness of the construct, allowing for more controlled micromotion, which can be beneficial for secondary bone healing (callus formation) in bridging osteosynthesis. Conversely, a shorter working length (more screws near the fracture) increases stiffness and is used for absolute stability and primary healing.

Question 9204

Topic: 2. Trauma

Regarding the 'tension band principle' as applied to plate fixation, which fracture pattern is it most effectively utilized for?

. A comminuted diaphyseal fracture of the femur.
. A transverse fracture of the olecranon.
. An articular fracture of the tibial plateau with significant depression.
. A simple oblique fracture of the midshaft humerus.
. A periprosthetic fracture distal to a cemented femoral stem.

Correct Answer & Explanation

. A transverse fracture of the olecranon.

Explanation

The tension band principle is most effectively applied to eccentric loading fractures where one side is under tension and the other under compression during physiological loading. A classic example is a transverse fracture of the olecranon or medial malleolus. The plate (or wire) is placed on the tension side (subcutaneous surface for olecranon), converting the tensile forces into compressive forces across the fracture site. A comminuted diaphyseal fracture would typically be treated with a bridging plate, and tibial plateau fractures require buttressing or fixed-angle support.

Question 9205

Topic: 2. Trauma

What is the primary biomechanical difference between a screw in a conventional plate (DCP) and a locking screw in a locking plate (LCP)?

. Conventional screws provide better resistance to torsional forces.
. Locking screws have a smaller core diameter, increasing ductility.
. Conventional screws rely on plate-bone friction for stability, while locking screws create a fixed-angle construct with the plate.
. Locking screws are exclusively used in cancellous bone due to their larger thread pitch.
. Conventional screws are designed for self-tapping, whereas locking screws are not.

Correct Answer & Explanation

. Conventional screws rely on plate-bone friction for stability, while locking screws create a fixed-angle construct with the plate.

Explanation

The fundamental difference lies in how they achieve stability. Conventional screws pull the plate to the bone, relying on plate-bone friction and compression for stability. Locking screws thread into the plate, creating a rigid, fixed-angle construct that acts as a unit with the plate, independent of plate-bone friction. This makes locking plates superior in osteopenic bone or comminuted fractures where plate-bone compression is suboptimal. Locking screws are not exclusively for cancellous bone; they are used in both cortical and cancellous regions, often with different thread designs.

Question 9206

Topic: 2. Trauma

Which statement regarding the use of 'combo holes' (combination holes) found in some modern locking plates is most accurate?

. They allow for either a locking screw or a conventional non-locking screw, but not both simultaneously.
. They combine a Dynamic Compression Unit (DCU) segment for conventional screws and a threaded segment for locking screws, allowing flexibility.
. They are designed exclusively for bicortical screw placement in osteoporotic bone.
. They facilitate sequential compression and locking by allowing a locking screw to be inserted first, then a conventional screw.
. They are primarily used to house cancellous screws for metaphyseal fixation.

Correct Answer & Explanation

. They combine a Dynamic Compression Unit (DCU) segment for conventional screws and a threaded segment for locking screws, allowing flexibility.

Explanation

Combo holes (or combination holes) in modern locking plates are versatile. They have two distinct segments: a dynamic compression unit (DCU) segment for conventional (non-locking) cortical screws to achieve compression, and a threaded segment for locking screws to create a fixed-angle construct. This allows the surgeon to choose between compression (with a conventional screw) or fixed-angle stability (with a locking screw) at each hole, or even to apply lag screws through the plate. They do not allow both types of screws simultaneously in thesamehole, but offer thechoicewithin that hole. This flexibility is key.

Question 9207

Topic: 2. Trauma

A reconstruction plate is often used for fixation of fractures in irregular bone configurations, such as the pelvis or scapula. What is a key characteristic that distinguishes a reconstruction plate from a standard DCP or LCP?

. Its ability to provide absolute stability for primary bone healing.
. Its significantly higher stiffness and bending strength.
. Its malleability and ability to be contoured extensively in multiple planes.
. Its exclusive use of locking screws for fixed-angle constructs.
. Its design for minimally invasive percutaneous insertion.

Correct Answer & Explanation

. Its malleability and ability to be contoured extensively in multiple planes.

Explanation

Reconstruction plates are characterized by their extreme malleability. They have notches or narrow waists between the screw holes, allowing them to be bent and twisted extensively in multiple planes to conform to complex, irregular bone surfaces (e.g., pelvis, acetabulum, clavicle, scapula). This malleability, however, comes at the cost of reduced stiffness and strength compared to standard DCPs or LCPs. They can be used with both conventional and sometimes locking screws, depending on the specific design, but their primary distinguishing feature is their conformability.

Question 9208

Topic: 2. Trauma

Which type of plate fixation would be most appropriate for a highly comminuted, long oblique fracture of the midshaft tibia in a polytrauma patient, aiming for relative stability and secondary bone healing?

. A conventional DCP providing absolute stability and interfragmentary compression.
. A blade plate for precise angular control.
. A buttress plate preventing articular fragment collapse.
. A bridging locking plate with a long working length.
. A tension band plate on the concave side of the tibia.

Correct Answer & Explanation

. A bridging locking plate with a long working length.

Explanation

For a highly comminuted, long oblique midshaft tibia fracture, the goal is typically relative stability to promote secondary bone healing via callus formation. A bridging locking plate is ideal in this scenario. It acts as an internal fixator, spanning the comminuted segment without directly compressing the fragments, thus preserving the periosteal blood supply. A long working length (fewer screws near the fracture zone, screws spread further apart in the main fragments) would further reduce stiffness and encourage micromotion conducive to callus formation. Absolute stability (DCP) is contraindicated in comminuted fractures. Blade plates are for metaphyseal/epiphyseal fractures. Buttress plates are for articular support. Tension band is for specific fracture patterns with eccentric loading.

Question 9209

Topic: Upper Extremity Trauma

A patient presents with a symptomatic proximal humerus locking plate, experiencing shoulder impingement due to hardware prominence. Which factor is most commonly implicated in this complication?

. Excessive screw length causing penetration of the articular surface.
. Over-tightening of the locking screws, leading to plate deformation.
. Improper plate contouring, especially at the superior aspect of the greater tuberosity.
. Inadequate number of screws used in the humeral head, leading to construct failure.
. Placement of the plate too far anterior on the humeral shaft.

Correct Answer & Explanation

. Improper plate contouring, especially at the superior aspect of the greater tuberosity.

Explanation

Hardware prominence, particularly at the superior aspect of the greater tuberosity, is a common complication with proximal humerus locking plates. This often occurs if the plate is positioned too high or if its contour does not precisely match the complex anatomy of the proximal humerus, leading to irritation or impingement of the deltoid or rotator cuff tendons. While articular screw penetration is also a serious complication, plate prominence causing impingement is frequently observed due to the plate's position relative to the surrounding soft tissues and acromion. Over-tightening of locking screws is not typically an issue due to the fixed-angle nature, and screw number relates to stability, not impingement.

Question 9210

Topic: 2. Trauma

What is the primary mechanical function of a 'buttress plate'?

. To provide interfragmentary compression across a fracture site.
. To neutralize torsional and bending forces acting on a lag screw.
. To resist axial collapse or shear forces, typically in metaphyseal or articular fractures.
. To bridge a comminuted fracture segment, allowing for relative stability.
. To stabilize bone grafts used in non-union surgery.

Correct Answer & Explanation

. To resist axial collapse or shear forces, typically in metaphyseal or articular fractures.

Explanation

A buttress plate is designed to resist axial or shear forces, preventing the collapse or displacement of bone fragments. It is commonly used in metaphyseal or articular fractures (e.g., tibial plateau, distal femur) where compressive forces might otherwise cause fragments to sink or displace. The plate is positioned to provide support against these forces, much like a buttress against a wall. It is distinct from neutralization (protecting a lag screw), compression (DCP), or bridging plates (comminuted fractures).

Question 9211

Topic: 2. Trauma

When planning fixation for a complex pilon fracture (distal tibia articular fracture), what is the most appropriate strategy regarding plate application?

. Apply a single, robust locking plate on the medial side for maximum stability.
. Utilize a conventional DCP on the anterior aspect to achieve absolute compression.
. Use multiple smaller, less rigid plates (e.g., one medial, one anterior/anterolateral) to buttress specific fragments and preserve soft tissues.
. Prioritize percutaneous screw fixation over any plating to minimize surgical insult.
. Employ a single extra-long locking plate spanning the entire tibia for ultimate rigidity.

Correct Answer & Explanation

. Use multiple smaller, less rigid plates (e.g., one medial, one anterior/anterolateral) to buttress specific fragments and preserve soft tissues.

Explanation

Complex pilon fractures often involve multiple comminuted articular fragments and significant soft tissue swelling. The strategy usually involves anatomical reduction of the articular surface (often with lag screws or K-wires), followed by buttressing the metaphyseal fragments. Given the complex anatomy and often precarious soft tissue envelope, using multiple smaller, less rigid plates (e.g., a medial plate and an anterolateral/anterior plate) allows for better fragment capture, buttressing, and minimizes soft tissue stripping compared to a single large plate. It also allows for strategic placement based on fracture pattern. Minimally invasive techniques are often employed to preserve blood supply. Absolute compression with a single DCP is typically not feasible or desirable for complex articular/metaphyseal comminution, and percutaneous screws alone are usually insufficient.

Question 9212

Topic: 2. Trauma

What is the primary rationale for using limited contact dynamic compression plates (LC-DCPs) over conventional DCPs?

. To provide fixed-angle stability similar to locking plates.
. To reduce the incidence of screw pull-out in osteoporotic bone.
. To minimize impairment of periosteal blood supply, thus promoting bone healing.
. To achieve greater interfragmentary compression across oblique fractures.
. To simplify the surgical technique by reducing the need for plate contouring.

Correct Answer & Explanation

. To minimize impairment of periosteal blood supply, thus promoting bone healing.

Explanation

LC-DCPs have a 'scalloped' undersurface, reducing the contact area between the plate and the bone by approximately 50%. This design helps to minimize the impairment of periosteal blood supply beneath the plate, which is crucial for bone healing. It also theoretically provides more even stress distribution over the bone surface. While it's an improvement, it still relies on plate-bone friction and does not provide fixed-angle stability like locking plates, nor does it inherently increase interfragmentary compression or simplify contouring compared to conventional DCPs. It addresses the biological concern of blood supply compromise.

Question 9213

Topic: 2. Trauma

In the context of fracture fixation with plates, what distinguishes 'absolute stability' from 'relative stability'?

. Absolute stability is achieved with locking plates, while relative stability is only possible with external fixation.
. Absolute stability allows for no micromotion at the fracture site, promoting primary bone healing; relative stability allows controlled micromotion, promoting secondary bone healing.
. Relative stability is only suitable for pediatric fractures, whereas absolute stability is for adults.
. Absolute stability requires a significantly longer period of non-weight bearing compared to relative stability.
. Relative stability utilizes biodegradable plates, while absolute stability uses permanent implants.

Correct Answer & Explanation

. Absolute stability allows for no micromotion at the fracture site, promoting primary bone healing; relative stability allows controlled micromotion, promoting secondary bone healing.

Explanation

Absolute stability, typically achieved with interfragmentary compression (e.g., lag screw, DCP with compression), aims to eliminate all micromotion at the fracture site, leading to primary bone healing without visible callus formation. Relative stability, achieved with methods like bridging plates, IM nails, or external fixators, allows for controlled, limited micromotion at the fracture site, which stimulates callus formation and secondary bone healing. Both are valid approaches depending on the fracture pattern and biological environment. Neither is exclusive to specific age groups or implant types. Weight-bearing protocols depend on the fracture and patient, not solely on absolute vs. relative stability type.

Question 9214

Topic: 2. Trauma

A patient undergoes ORIF of a proximal tibia fracture using a locking plate. Postoperatively, what is a potential advantage of the fixed-angle construct in managing osteoporotic bone?

. It promotes rapid bone remodeling around the plate due to increased stress.
. It enhances the biological environment by compressing the periosteum.
. It allows for stable fixation even with poor screw purchase in the bone, by distributing load over a wider area.
. It significantly reduces the need for bone grafting in comminuted fractures.
. It limits blood supply to the fracture zone, thus reducing inflammation.

Correct Answer & Explanation

. It allows for stable fixation even with poor screw purchase in the bone, by distributing load over a wider area.

Explanation

In osteoporotic bone, conventional screws often have poor pull-out strength. Locking plates overcome this by creating a fixed-angle construct where the screw-plate interface, not the screw-bone interface, bears the primary load. This distributes the load more broadly within the bone fragments and prevents screw pull-out or toggle, providing stable fixation even when bone quality is poor. It effectively functions as an internal fixator, independent of plate-bone friction or compression. It does not necessarily reduce the need for grafting or limit blood supply in a beneficial way.

Question 9215

Topic: 2. Trauma

Which of the following is the most appropriate indication for the use of a one-third tubular plate?

. High-energy comminuted diaphyseal femur fracture.
. A simple transverse fracture of the distal tibia metaphysis.
. An olecranon fracture, as part of a tension band construct.
. A complex articular fracture of the proximal humerus.
. A segmental forearm fracture requiring rigid fixation.

Correct Answer & Explanation

. An olecranon fracture, as part of a tension band construct.

Explanation

One-third tubular plates are relatively weak and typically used in areas of low stress or for tension band wiring (e.g., olecranon, patella) to convert tensile forces to compression. While they can be used for olecranon fractures, the question asks for themostappropriate general indication. They are often used as neutralization plates for small bone fragments or for specific tension band applications, but their primary role is in low-load applications, often as a component of a tension band for specific small bone fractures or osteotomies. For an olecranon fracture, a tension band wire is often used, sometimes with a one-third tubular plate to augment fixation. However, their primary indication as a standalone plate is limited to small bones or tension banding. Comparing to olecranon (often wires), it is very appropriate for tension banding. The options are tricky. Let's re-evaluate. Olecranon fractures are a classic tension band application where a 1/3 tubular plate can be used. Other examples might be medial malleolus. Femur, tibia (unless very simple, non-weight bearing part), humerus, forearm need stronger plates. Thus, the olecranon fracture, specifically in a tension band construct, is a hallmark application for 1/3 tubular plates. A simple transverse fracture of the distal tibia metaphysis would typically require a stronger locking or conventional plate.

Question 9216

Topic: 2. Trauma

When applying a plate to a bone, what is the significance of the 'point of highest resistance' in plate contouring?

. It refers to the stiffest part of the plate where no contouring should occur.
. It is the point on the bone where the plate must be perfectly anatomically fitted.
. It is the point where the plate is intentionally over-contoured to achieve compression on the far cortex.
. It represents the area of maximum bone density, dictating screw placement.
. It's the location where the plate contacts the bone first during sequential tightening.

Correct Answer & Explanation

. It is the point where the plate is intentionally over-contoured to achieve compression on the far cortex.

Explanation

The 'point of highest resistance' in plate contouring is the location on the plate where it is intentionally over-contoured (often slightly pre-bent away from the bone) such that when the plate is drawn down to the bone by tightening screws, it generates compression across the fracture site, especially on the opposite cortex (trans-cortex). This is a critical principle for achieving effective interfragmentary compression with conventional plates, particularly in transverse fractures. This over-contouring ensures that when the plate is pulled flat against the bone, the fracture fragments are compressed. This is related to the pre-bending concept discussed earlier.

Question 9217

Topic: 2. Trauma

What is the primary advantage of using a variable-angle locking plate system over a fixed-angle locking plate system?

. Greater overall construct stiffness.
. Reduced risk of screw back-out.
. Ability to individually aim and angle screws within a certain cone of angulation, optimizing fragment purchase.
. Requires less meticulous plate contouring to match bone anatomy.
. Significantly lower cost due to simpler manufacturing.

Correct Answer & Explanation

. Ability to individually aim and angle screws within a certain cone of angulation, optimizing fragment purchase.

Explanation

Variable-angle locking plates offer the significant advantage of allowing the surgeon to choose the insertion angle of each locking screw within a certain angular range (e.g., +/- 15-20 degrees) relative to the plate. This flexibility is crucial for optimizing screw purchase in complex fracture patterns, capturing small fragments, avoiding articular surfaces, or bypassing existing hardware. Fixed-angle plates do not allow for this adjustment. While it doesn't necessarily mean less contouring (anatomical fit is still important), the primary benefit is the angular adjustability of screws.

Question 9218

Topic: 2. Trauma

A 28-year-old male sustains a simple transverse midshaft femoral fracture. The decision is made to treat with an intramedullary nail. If plating were considered as an alternative, which biomechanical aspect makes intramedullary nailing generally superior for this specific fracture?

. Nails are inherently stiffer than plates in bending.
. Plates primarily provide rotational stability, which is often insufficient for transverse fractures.
. Nails provide central load-sharing, whereas plates create eccentric loading.
. Nails completely eliminate all micromotion at the fracture site, promoting primary healing.
. Plates require extensive soft tissue stripping, unlike nailing.

Correct Answer & Explanation

. Nails provide central load-sharing, whereas plates create eccentric loading.

Explanation

For diaphyseal fractures, intramedullary nails are biomechanically superior to plates primarily because they provide central load-sharing. The nail is placed within the medullary canal, close to the neutral axis of the bone, allowing it to share the load with the bone more efficiently. Plates, being external to the bone, create an eccentric load-bearing construct, leading to higher stresses on the plate and potential stress shielding. While soft tissue stripping is a consideration for plates, the fundamental biomechanical advantage of load-sharing is key for IM nails in diaphyseal fractures. Nailing does not necessarily eliminateallmicromotion, promoting secondary healing, and plates can provide good rotational stability.

Question 9219

Topic: 2. Trauma

Which factor is most crucial in determining the 'strength' and 'stiffness' of a plate-screw construct?

. The material composition of the plate (e.g., stainless steel vs. titanium).
. The number of screws placed distal to the fracture site.
. The cross-sectional geometry (thickness and width) of the plate and its working length.
. The surface finish of the plate (e.g., polished vs. sandblasted).
. The diameter of the drill bits used for screw insertion.

Correct Answer & Explanation

. The cross-sectional geometry (thickness and width) of the plate and its working length.

Explanation

The strength and stiffness of a plate construct are primarily determined by the plate's cross-sectional geometry (thickness, width) and its working length. Thicker and wider plates are stiffer and stronger. A shorter working length (more screws closer to the fracture, or screws placed closer together) increases stiffness, while a longer working length reduces it. While plate material and screw number contribute, the geometry and working length are the most significant determinants of the construct's overall mechanical properties.

Question 9220

Topic: 2. Trauma

A surgeon plans to use a limited contact dynamic compression plate (LC-DCP) for a diaphyseal fracture. What is a specific feature of the LC-DCP hole design that distinguishes it from a conventional DCP?

. It has a fixed angle thread to accommodate locking screws.
. It incorporates a separate buttress segment for metaphyseal support.
. It has a specific 'T-shaped' slot for controlled compression.
. Its holes are undercut (scalloped) on the undersurface to reduce plate-bone contact.
. It has integrated tension band loops for wire fixation.

Correct Answer & Explanation

. It has a specific 'T-shaped' slot for controlled compression.

Explanation

While LC-DCPs have a scalloped undersurface (reducing plate-bone contact), thehole designitself is also subtly different. The LC-DCP hole has a 'T-shaped' slot at the end of the dynamic compression unit (DCU) allowing for more uniform compression and less bone necrosis under the plate compared to the conventional DCP's spherical gliding hole. This design refinement, combined with the scalloped undersurface, contributes to its biological advantages. It does not accommodate locking screws (that's LCP combo holes), nor does it have separate buttress segments or tension band loops.

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