THE INCREASE IN THE DURAL SAC AND FORAMINAL AREA IS MAINTAINED AT 2 YEARS FOLLOWING X STOP PROCEDURE

Abstract

Aim: To measure the effect of X-stop interspinous decompression device on the dural sac and foraminal area at 6 and 24 months post operatively at the instrumented level 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 and 6 & 24 months post operatively. Foraminal area was measured in flexion and extension position whereas dural cross sectional area was measured in erect, neutral, flexion and extension positions. 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 six 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. We noted increase in mean dural sac area in all positions. The mean dural sac area increased from 131 mm2 to 143 mm2 (p=0.144) at 6 months and from 137 mm2 to 202 mm2 (p= 000) at 24 months in standing position. The difference in pre-operative measurements in the six and 24-month measurements is because of the different patient numbers scanned. There were similar increased dural sac areas in the other positions. The mean foraminal areas were measured in flexion and extension and the measurements in extension were increased from 66.58 mm2 to 79.51 mm2 (p=. 001) at 6 months and from 68.10 to 69.57 mm2 (p=0.752) at 24 months on left side; and increased from 63.75 mm2 to 71.65 mm2 (p=0.036) at 6 months, from 65.54 mm2 to 68.01mm2 (p=0.440) at 24 months on right side. Thus there is a small increase in foraminal areas and statistically significant increase in dural sac areas at 24 months.

Conclusion: X-stop interspinous device remains effective in decompressing the stenosed spinal segment by increasing the anatomic dural cross sectional areas and foraminal areas of spinal canal at 24 months post operatively, thus providing symptomatic relief from lumbar canal stenosis.