Change in Sagittal Balance with Placement of an Interspinous Spacer

Study Design: A prospective case series.

Objective: To determine the effect of X-STOP implantation on sagittal spinal balance using 36-inch films.

Summary Of Background Data: Interspinous process spacers have been shown as an effective treatment of neurogenic claudication. The devices block the last few degrees of extension at the stenotic level, thus preventing compression of the nerve roots. These devices have been criticized because they may push the patient's spine into a kyphotic position. However, opening the stenotic level may allow a patient to stand more upright, thereby improving sagittal balance.

Methods: Institutional review board's approval was obtained. A prospective study of 20 patients who were undergoing an X-STOP insertion was utilized. Their spines were x-rayed preoperatively and postoperatively with 36-inch films. Preoperative and postoperative sagittal balance was measured with a C7 body plum line on both films and the difference was measured. Lumbar lordosis was also compared using Cobb angles.

Results: Measurements taken from lateral full-length spine radio-graphs showed an average improvement in sagittal balance of 2.0 cm (range -3.7 to 6.1 cm). The average change in lordosis was -1.1°.

Conclusion: Although previous studies of interspinous process distraction have examined segmental lordosis, disc angles, and other parameters, this study is the first to examine overall spinal balance on full-length films. Interspinous distraction does not seem to be detrimental to sagittal balance, and may improve it.