THE LUMBAR SPINE KINEMATICS FOLLOWING X STOP PROCEDURE AT 6 AND 24 MONTHS POST-OPERATIVELY.

Abstract

Aim: To study the effect of X-stop interspinous decompression device on the lumbar spine kinematics at 6 and 24 months post operatively at the instrumented and adjacent levels in patients with symptomatic lumbar canal stenosis.

Design: Prospective Observational Study of 48 patients.

Methods: Patients due to have an X stop procedure were included and had a positional MRI scan preoperatively, 6 and 24 months post operatively in erect, flexion, extension and neutral position. Disc heights, endplate angles, segmental and lumbar spine motion was measured at stenosed instrumented and adjacent levels. Osiris 4.17 software program was used to measure the canal and foraminal dimensions. The data was analysed using paired t test on SPSS ver.15.01.

Results: Forty-eight patients (25 Male and 23 Female) underwent scans preoperatively and at 6 months. Twenty-nine patients had single level and 19 had double level procedures. Three patients had removal of X stop and 5 did not have scan at 24 months, leaving 40 patients scanned at 24 months. Of these, 38 scans were complete and were included. Mean anterior disc height reduced from 7.1 mm to 6.3 mm (p=0.004) from 48 scans at 6 months and from 7.2 mm (pre-operative) to 5.9 mm (at 24 months) – (p=0.000) from 38 scans at 24 months at the instrumented level. We hypothesise that the reduction in anterior disc heights could be a result of the interspinous distraction plus the natural progression of spinal stenosis and ageing. There was no significant change in posterior disc heights at instrumented level or adjacent levels. The mean lumbar spine motion was 22.89o, 21.3 o and 21o (p=0.183) preoperatively, 6 and 24 months respectively. The total range of movements of lumbar spine and individual segments were measured. There was no significant change in the segmental range of motion at instrumented and adjacent levels.

Conclusion: X-stop interspinous device does not significantly alter the kinematics of lumbar spine at instrumented and adjacent levels at 6 and 24 months postoperatively.