A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results

Abstract

Patients suffering from neurogenic intermittent claudication secondary to lumbar spinal stenosis have historically been limited to a choice between a decompressive laminectomy with or without fusion or a regimen of non-operative therapies. The X STOP Interspinous Process Distraction System (St. Francis Medical Technologies, Concord, Calif.), a new interspinous implant for patients whose symptoms are exacerbated in extension and relieved in flexion, has been available in Europe since June 2002. This study reports the results from a prospective, randomized trial of the X STOP conducted at nine centers in the U.S. Two hundred patients were enrolled in the study and 191 were treated; 100 received the X STOP and 91 received non-operative therapy (NON OP) as a control. The Zurich Claudication Questionnaire (ZCQ) was the primary outcomes measurement. Validated for lumbar spinal stenosis patients, the ZCQ measures physical function, symptom severity, and patient satisfaction. Patients completed the ZCQ upon enrollment and at follow-up periods of 6 weeks, 6 months, and 1 year. Using the ZCQ criteria, at 6 weeks the success rate was 52% for X STOP patients and 10% for NON OP patients. At 6 months, the success rates were 52 and 9%, respectively, and at 1 year, 59 and 12%. The results of this prospective study indicate that the X STOP offers a significant improvement over non-operative therapies at 1 year with a success rate comparable to published reports for decompressive laminectomy, but with considerably lower morbidity.

Fig. 1

A The patient in the right lateral decubitus position with an incision at the stenotic level. B The curved dilator inserted in the anterior margin of the interspinous space. C A sizing distractor inserted to determine the implant size. D The X STOP inserted into the interspinous space. E The adjustable wing fastened to the implant

Fig. 2

A sagittal, transverse, posterior, and orthogonal view of the X STOP implant. The spacer is produced in 6-, 8-, 10-, 12-, and 14-mm sizes to accommodate a range of interspinous heights. The lateral wings prevent lateral and anterior implant migration

Fig. 3 A

Pre-operative lateral and B anteroposterior (AP) radiographs. C Post-operative lateral and D AP radiographs of the same patient

Fig. 4

Improvement in the symptom severity of X STOP and NON OP patients at 6 weeks, 6 months, and 1 year. The X STOP patients are significantly more pain free at each time point

Fig. 5

Improvement in the physical function of X STOP and NON OP patients at 6 weeks, 6 months, and 1 year. The X STOP patients have significantly improved function at each time point

Fig. 6

Satisfaction rates of the X STOP and NON OP patients at each time point. The X STOP patients are significantly more satisfied than the NON OP patients with their treatment

Fig. 7

In order to be considered a clinical success, a patient must be significantly improved in the symptom severity and physical function domains, and be satisfied with the treatment outcome. Significantly more X STOP patients are a clinical success than NON OP patients

Fig. 8

The pre-op, 6-week, 6-month, and 1-year SF-36 scores for the X STOP group. The scores at all follow-up time points are significantly improved over the pre-op scores. PF physical function, RP role physical, RE role emotional, VT vitality, MH mental health, SF social function, BP bodily pain, GH general health

Fig. 9

The pre-treatment, 6 week, 6 month, and 1 year SF-36 scores for the NON OP group. The scores at all follow-up time points are not significantly different from the pre-treatment scores. PF physical function, RP role physical, RE role emotional, VT vitality, MH mental health, SF social function, BP bodily pain, GH general health