Scoliosis and interspinous decompression with the X-STOP: prospective minimum 1-year outcomes in lumbar spinal stenosis

Abstract Background context The X-STOP interspinous decompression device, as a treatment for neurogenic intermittent claudication (NIC) because of lumbar spinal stenosis (LSS), has been shown to be superior to nonoperative control treatment. Current Food and Drug Administration labeling limits X-STOP use to NIC patients with a maximum of 25° concomitant lumbar scoliosis. This value was arrived at arbitrarily by the device developers and is untested. Purpose To determine X-STOP utility for NIC in patients with concomitant lumbar scoliosis. Study design A prospective, single institution, clinical outcome study comparing patients with scoliosis with patients without scoliosis who underwent X-STOP interspinous decompression for NIC because of LSS. Patient sample A cohort of 179 consecutive patients, 63 with scoliosis (Cobb angle 11° or more) and 116 without scoliosis, with symptoms attributable to NIC treated between January 2006 and May 2007, were included in the study. Outcome measures All patients completed self-reported preoperative and minimum 1-year postoperative outcome forms. Functional measures included Oswestry Disability Index (ODI), visual analog scale (VAS) pain score, and maximum walking and standing times in minutes. Three questions measured patient satisfaction: How satisfied were you with the procedure (very satisfied, somewhat satisfied, somewhat dissatisfied, or very dissatisfied); Would you have the procedure again? (yes or no); Would you recommend the procedure to a friend? (yes or no). Methods Before analysis, the 179 consecutive X-STOP patients were divided into three groups: Group 1 (controls without scoliosis, n=116); Group 2 (low scoliosis: 11–25°, n=41), and Group 3 (high scoliosis: 26° or more, n=22). The three groups were not statistically different for any preoperative functional scores. Groups were analyzed for pre- to postoperative functional change and level of satisfaction. Segmental scoliosis at the treated level was also analyzed. Results Fifty-six percent of Group 1 and Group 2 patients, but only 18% of Group 3 patients, achieved the success criterion of an ODI improvement of 15 or more points (Group 3 the outlier, p=.004). The satisfaction rate was Group 1, 76%; Group 2, 78%; Group 3, 59% (Group 3 the outlier, p=.0001). On average, all three groups improved for each outcome: Group 1 (ODI 17.3, VAS 2.0, standing time 39 minutes, and walking time 43 minutes), Group 2 (ODI 20.0, VAS 1.9, standing time 65 minutes, and walking