9:26 Treatment of lumbar spinal stenosis with an interspinous spacer

Abstract

Purpose of study: A newly developed spinal implant for the treatment of symptomatic lumbar spinal stenosis is being evaluated in a prospective randomized multicenter study. The implant is placed between the spinous processes of the affected level(s), and the intent is to position the stenotic segment in slight flexion, and by preventing extension, the symptoms of lumbar spinal stenosis will be relieved. The primary objective of this study is to evaluate the safety and efficacy of the implant in a clinical trial setting.Methods used: The surgical implantation of the implant is performed under local anesthesia and routinely requires 30 minutes to 1 hour of surgical time. There is negligible blood loss. The patients typically return home 3 hours after surgery. Two hundred nine patients with neurogenic claudication at the L3–L4 and/or L4–L5 levels have been enrolled in the randomized prospective study. One hundred fifteen of these patients have received the implant (X-Stop; St. Francis Medical Technologies, Concord, CA), and 94 have been treated conservatively including epidural injections. Before surgery, all patients completed an initial Zurich Claudication Questionnaire (ZCQ). The ZCQ is a self-administered survey developed to be a spinal stenosis specific outcome measure consisting of symptom severity, physical function and satisfaction scales [1]. A patient must improve in each of the three categories to be considered a success. In the current study, the ZCQ scores were available for comparison between the implant and conservative groups at 6-week, 6-month and 1-year time points. The two groups were compared statistically using Fisher's exact test (p<.05).of findings: To date, 209 patients have completed the 6-week ZCQ (115 implant and 94 conservative), 176 have completed the 6-month ZCQ (91 implant and 85 conservative) and 100 have completed the 1-year questionnaire (46 implant and 54 conservative). The overall success rates for the implant group are significantly greater than those of the conservative group at each time point (Table 1)Table 1Success rates of the implant and conservative groupsImplant successConservative successp Value6 weeks66/115 (57%)9/94 (10%)<.0016 months50/91 (55%)5/85 (6%)<.0011 year32/46 (70%)1/54 (2%)<.001. Moreover, at 1 year the success rates for the symptom severity, physical function and satisfaction categories were 86%, 83% and 88%, respectively, for the implant group, and 11%, 11% and 28% for the conservative group.Relationship between findings and existing knowledge: The results of this study demonstrate that the implant may be effective in treating pain in patients with lumbar spinal stenosis. This series of patients demonstrates the relative safety and efficacy of a newly developed spinal implant for the treatment of symptomatic lumbar spinal stenosis. In many ways this short-term preliminary follow-up compares favorably to traditional surgical treatment as well as nonsurgical treatment in selected cases. The surgical procedure is minimally invasive, inexpensive and safe. There were no intraoperative complications. Finally, the measurement instrument has been demonstrated to be responsive and sensitive enough to measure clinically significant improvements in mild to severe cases.Overall significance of findings: These findings indicate that the implant may be an effective means of treating painful and debilitating symptoms of lumbar spinal stenosis.Disclosures: Device or drug: X-Stop, Investigational Device Exemption (IDE). Status: investigational.Conflict of interest: Scott Yerby, stockholder; James Zucherman, stockholder; Ken Hsu, stockholder.