Preoperative Computed Tomography-Based Prediction of Device Size for Lumbar Stabilization with Interspinous Process Device for Lumbar Spinal Canal Stenosis.

INTRODUCTION

Lumbar stabilization using an interspinous process device is a surgical option for lumbar spinal canal stenosis. This study retrospectively evaluated the relationship between preoperative computed tomography (CT) measurements and inserted device size.

METHODS

A total of 21 consecutive patients who underwent lumbar stabilization with an interspinous process device (Swift systemⓇ) for one- or two-level lumbar spinal canal stenosis were included. The mean age of the patients was 73.2 years. Surgery involved one level in seven patients and two levels in 14 patients. On preoperative CT images, the interspinous process distance was measured at the posterior line of the bilateral facet joints (basal distance) and at a point 8 mm dorsal (dorsal distance), corresponding to the Swift systemⓇ diameter.

RESULTS

The mean basal and dorsal distances were 6.5±2.1 mm and 5.3±2.4 mm, respectively. In 33 levels (93.5%) with a basal distance ≥4 mm, the device was successfully inserted between the spinous process bases. In the two levels with a basal distance of 2 mm, the device could not be inserted at the base and was placed dorsally. Except for these two cases, the size of the inserted device significantly correlated with the basal distance (p<0.01, r=0.694).

CONCLUSIONS

The basal interspinous distance on preoperative CT was useful for predicting the appropriate device size. The device could be inserted between the spinous processes in all cases with a basal distance of ≥4 mm.