Two-Year Evaluation of the X-STOP Interspinous Spacer in Different Primary Patient Populations With Neurogenic Intermittent Claudication Because of Lumbar Spinal Stenosis

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Multicenter, prospective single-arm study in patients diagnosed with neurogenic intermittent claudication because of lumbar spinal stenosis. To collect data from 2 different primary patient populations, new participants meeting entry criteria [Continued Access Program (CAP)], or subjects who had been randomly assigned to nonsurgical management in the pivotal Investigational Device Exemption study and failed to respond upon study completion [Crossover Study (COS)]. The X-STOP interspinous spacer is a minimally invasive treatment option for neurogenic intermittent claudication shown to improve pain, physical functioning, and/or overall quality of life. Fifty-five subjects were enrolled, 42 in CAP and 13 in COS. Zurich Claudication Questionnaire (ZCQ) success rates were obtained based on the number of subjects achieving a threshold level of success. Mean SF-36 domain scores were compared with baseline using repeated measures analysis of variance. Eighty percent of subjects completed the study. At 2 years, 26/43 subjects (60.5%) achieved clinically significant improvement in the Symptom Severity domain, 25/43 (58.1%) achieved clinically significant improvement in the Physical Function domain, and 31/44 (70.5%) achieved clinically significant improvement in the Patient Satisfaction domain of the ZCQ. Statistically significant improvement in mean scores was obtained in all physical domains of the SF-36 (with the exception of General Health) at 24 months. Mean improvement in ZCQ and SF-36 scores was not as pronounced in the COS cohort compared with the CAP cohort. The most frequently reported device-related or treatment-related adverse event was stenosis pain reported by 3 subjects. Overall data are consistent with the randomized pivotal Investigational Device Exemption trial. On the basis of the COS cohort which was subject to several additional years of failed conservative treatment, overall success rates do not improve as greatly in patients with long-standing lumbar spinal stenosis symptoms.