## Core Concept
Lag screw fixation is a surgical technique used in orthopedic and trauma surgery to stabilize bone fractures. It involves the use of a screw that threads into one fragment of bone but not the other, effectively compressing the fragments together. This technique relies on the principle of converting rotational force into compressive force across the fracture site.

## Why the Correct Answer is Right
The correct answer highlights a key advantage or characteristic of lag screw fixation. Typically, lag screws are used to provide interfragmentary compression, which is crucial for the healing of fractures, especially in the absence of significant soft tissue damage. The screw threads engage in one bone fragment but not the other, allowing for compression as the screw is tightened. This method enhances fracture stability and promotes primary bone healing by directly compressing the fracture fragments together.

## Why Each Wrong Option is Incorrect
- **Option A:** Without specific details on what Option A states, it's challenging to provide a direct refutation. However, if Option A suggests that lag screws require both fragments to have threads for equal distribution of stress, it would be incorrect because the essence of a lag screw is that it threads into only one fragment.
- **Option B:** Similarly, if Option B proposes that lag screws are only used for non-displaced fractures, it would be incorrect because lag screws are particularly valuable in displaced fractures where reduction and stabilization are necessary.
- **Option C:** If Option C implies that lag screws provide no mechanical advantage over other fixation methods, it would be incorrect as lag screws do offer a mechanical advantage by converting torque into compressive force across the fracture site.

## Clinical Pearl / High-Yield Fact
A critical point to remember is that for effective lag screw fixation, the screw must be placed in a manner that allows for compression across the fracture site. This often involves careful planning and execution to ensure that the screw engages the bone fragment on one side of the fracture but not the other, thereby providing the necessary compression for healing.

## Correct Answer: D. [Detailed description of correct answer]