Primary Outcome Measures:
- Number of Patient Successes Based on Treatment Response for Target Population [ Time Frame: 3+ years following first 2 years post-X-STOP implant through IDE study ] [ Designated as safety issue: Yes ]
Treatment response defined by 7 separate criteria as follows: Clinically significant improvement (at least 0.5 points) in Symptom Severity domain of Zurich Claudication Questionnaire (ZCQ), clinically significant improvement (at least 0.5 points) in Physical Function domain of ZCQ, Patient Satisfaction score of <2.5 points in ZCQ, no additional lumbar spinal stenosis surgery, maintenance of distraction, no device dislodgement, no device-related complications. All 7 criteria must be met to be considered a treatment success.
Secondary Outcome Measures:
- Secondary Measures of Long-term Effectiveness Include the Following: ZCQ Domain Scores and SF-36 Scores. Proportions Will be Analyzed for the Primary Efficacy Assessment. For Continuous Variables, Means and Standard Deviations Will be Presented. [ Time Frame: Five years ] [ Designated as safety issue: No ]
Device: X STOP® Interspinous Process Decompression System
The X STOP is a titanium implant that fits between the spinous processes of the lumbar spine. It is made from Ti-6AI-4V Eli titanium alloy (ISO 5832/3) and consists of two components: a spacer assembly and a wing assembly.
Evaluate the long term safety and effectiveness of the X-Stop interspinous process decompression system In the patients who received the X-Stop under the IDE. These patients consist of two cohorts to be evaluated: patients who had moderately impaired physical function prior to X-Stop implantation (as determined by a baseline score >2.0 in the physical function (PF) domain of the Zurich claudication questionnaire), and patients who had mildly impaired physical function prior to X-Stop surgery(as determined by a baseline score <=2.0 in the PF domain of the Zurich claudication questionnaire (ZCQ), through the fifth postoperative year. Clinical examination will be performed at each office visit to confirm the absence of neurological complications. X-ray films (AP/lateral views) taken during the fifth postoperative year will, be analyzed to confirm A) maintenance of distraction and B) the absence of radiological evidence of device-related complications. Secondary endpoints will include mean scores from the SF-36, and incidence rates of adverse events, device failures, and secondary surgeries.