Interlaminar stabilization for spinal stenosis in the Medicare population

Abstract

The number of complex fusions performed on Medicare beneficiaries, defined as ≥age 65, with lumbar spinal stenosis with or without spondylolisthesis has been increasing. Typically, these procedures are longer, more invasive and pose a greater risk for complications. Interlaminar stabilization (ILS) serves as an intermediary between decompression alone and decompression with fusion. The purpose of this study was to prospectively examine the efficacy of ILS in patients ≥age 65 through comparison to fusion in the same age group and ILS in younger patients. A prospective, multicentered, randomized controlled trial comparing decompression with ILS to decompression with posterolateral fusion with bilateral pedicle screw instrumentation. Patients from 21 sites in the United States underwent surgery for moderate stenosis with up to a grade 1 degenerative spondylolisthesis and failure of conservative treatment with low back pain at 1 or 2 contiguous levels from L1-L5. Preoperatively, patient-reported assessment had to meet the criteria of significant pain and disability (Visual Analog Scale [VAS back pain] ≥50 mm on a 100 mm scale; Oswestry Disability Index [ODI] of ≥20/50). The primary outcome was overall Composite Clinical Success (CCS) as determined by ODI scores, incidence of postoperative epidural injections and/or reoperations, incidence of device-related complications, and persistent or progressive neurological deficit. Secondary outcomes included patient satisfaction as measured by VAS for back and worse leg pain and Zurich Claudication Questionnaire scores. Narcotic usage data and radiographic assessment of changes in postoperative posterior disc height and foraminal height were also evaluated. At 1- or 2-levels, 84 patients ≥age 65 underwent decompression with ILS, 57 patients ≥age 65 underwent decompression with fusion, and 131 patients <age 65 underwent decompression with ILS. Comparisons were made between ≥age 65 ILS patients and ≥age 65 fusion patients and between <age 65 and ≥age 65 ILS patients. The patients were assessed before and after surgery at 6 weeks and 3, 6, 12, 18, 24, 48, and 60 months. At 24 and 60 months, there were no statistically significant differences in CCS or any of the individual components of CCS between the ≥ age 65 ILS and fusion groups or between the < age 65 and ≥ age 65 ILS groups. ILS Medicare patients experienced significantly shorter surgeries (p<.001), less blood loss (p<.001), and a shorter hospital stay (p<.001) than fusion patients. There were no significant differences radiographically or with regards to postoperative narcotic usage. Clinically, ILS patients ≥age 65 performed as well as both those receiving fusion and those <age 65 who received ILS. Importantly, however, for this older population, ILS Medicare patients experienced less blood loss, a shorter operation and shorter hospital stay than fusion Medicare patients.