Superion Interspinous Spacer Treatment of Moderate Spinal Stenosis: 4-Year Results.

OBJECTIVE: To determine 4-year clinical outcomes in patients with moderate lumbar spinal stenosis treated with minimally invasive stand-alone interspinous process decompression using the Superion device. METHODS: The 4-year Superion data were extracted from a randomized, controlled Food and Drug Administration investigational device exemption trial. Patients with intermittent neurogenic claudication relieved with back flexion who failed at least 6 months of nonsurgical management were enrolled. Outcomes included Zurich Claudication Questionnaire (ZCQ) symptom severity (ss), physical function (pf) and patient satisfaction (ps) subdomains, leg and back pain visual analog scale (VAS), and Oswestry Disability Index (ODI). At 4-year follow-up, 89 of the 122 patients (73%) provided complete clinical outcome evaluations. RESULTS: At 4 years after index procedure, 75 of 89 patients with Superion (84.3%) demonstrated clinical success on at least 2 of 3 ZCQ domains. Individual component responder rates were 83% (74/89), 79% (70/89), and 87% (77/89) for ZCQss, ZCQpf, and ZCQps; 78% (67/86) and 66% (57/86) for leg and back pain VAS; and 62% (55/89) for ODI. Patients with Superion also demonstrated percentage improvements over baseline of 41%, 40%, 73%, 69%, and 61% for ZCQss, ZCQpf, leg pain VAS, back pain VAS, and ODI. Within-group effect sizes all were classified as very large (>1.0): 1.49, 1.65, 1.42, 1.12, and 1.46 for ZCQss, ZCQpf, leg pain VAS, back pain VAS, and ODI. CONCLUSIONS: Minimally invasive implantation of the Superion device provides long-term, durable relief of symptoms of intermittent neurogenic claudication for patients with moderate lumbar spinal stenosis.