What is the cause of immediate diplopia in conjunction with a zygomaticomaxillary complex (ZMC) fracture?

Immediate diplopia following a zygomaticomaxillary complex (ZMC) fracture is primarily due to entrapment of the extraocular muscles. When a ZMC fracture occurs, it can lead to herniation or entrapment of these muscles within the fracture site or within the surrounding soft tissue. This mechanical limitation causes an inability to properly coordinate eye movement, resulting in diplopia, or double vision.

Entrapment typically presents immediately due to the acute nature of the injury, which disrupts normal ocular motility. As the extraocular muscles are crucial for coordinated eye movements, any entrapment can lead to misalignment of the eyes, thereby producing diplopia.

Understanding the mechanism of muscle entrapment is vital in the context of ZMC fractures, as it underscores the need for prompt evaluation and possible intervention to restore proper function and alignment. Other factors such as muscle contraction or fatigue could contribute to ocular symptoms but are more associated with different contexts rather than the immediate effects seen in ZMC fractures. Nerve damage could also lead to diplopia, but this typically has a different clinical onset and presentation.