ABSTRACT

The true incidence and clinical impact of instability at an adjacent segment after stabilization of the lumbar spine is unclear. This study investigates the development of disc herniation or instability at the adjacent segment after stabilization of the lumbar spine.

Twenty-nine patients who received surgery using short-segment posterior instrumentation and fusion were evaluated for the development of adjacent upper segment disc herniation and instability. Stabilization and fusion were performed for listhesis or presumed instability after stenosis surgery or unstable disc herniation. For all patients, pre- and postoperative MRIs and X-ray images were obtained. Disc herniations were evaluated by MRI, and any slippage or rotational angling of the adjacent upper segments were measured by X-ray.

Three patients had disc herniation and six patients had instability at the adjacent segment. No statistical correlation was found between the development of instability and disc herniation and age, gender, type of pathology, or level stabilized.

Stabilization and fusion were sufficient for patients and did not produce too much instability at the adjacent upper segment. Randomized studies with more patients and different instability criteria are needed to better understand adjacent segment instability.