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 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 FUNCTINO (PF) DOMAIN OF THE ZURICH CLAUDICATINO 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). PAIN AND FUNCTION EVALUATIONS WILL BE PERFORMED ANNUALLY USING THE ZURICH CLAUDICATION QUESTIONNAIRE (ZCQ), THROUGH THE FIFTH POSTOPERATIVE YEAR. CLINICAL EXAMINATINO WILL BE PERFORMED AT EACH OFFICE VISIT TO CONFIRM THE ABSENCE OF NEUROLOGIC COMPLICATIONS. X-RAY FILMS (AP/LATERAL VIEWS) TAKEN DURING THE FIFTH POSPOPERATIVE YEAR WILLL, BE ANALYZED TO CONFIRM A) MAINTENANCE OF DISTRACTION AND B) THE ABSENCE OF RADIOLOGIC 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.