What defines spondylolisthesis?

Spondylolisthesis is primarily defined as the condition in which one vertebra slides forward over the vertebra below it. This displacement can result from various factors, including degenerative changes, trauma, or congenital abnormalities. The sliding can lead to narrowing of the spinal canal and potentially cause compression of spinal nerves, which may result in pain and other neurological symptoms.

While other choices mention conditions related to vertebrae, such as fractures and dislocations, they do not specifically match the definition of spondylolisthesis. Fracture of the spinous process refers to a break in a specific part of the vertebra, while compression of the vertebral bodies usually refers to a collapse due to trauma or osteoporosis. A complete dislocation of the vertebrae denotes a severe separation of the vertebrae from their normal anatomical position, which is not the characteristic of spondylolisthesis. Therefore, the forward sliding of one vertebra over another is the hallmark defining feature of spondylolisthesis and correctly identifies the condition.