Prospective 5-year follow-up of L5-S1 versus L4-5 midline decompression and interspinous-interlaminar fixation as a stand-alone treatment for spinal stenosis compared with laminectomies.

Background: Spinal stenosis treatment includes laminectomies with or without fusion or with interspinous distraction with or without fixation. Lack of published data on interspinous fixation devices (IFD) at L5-S1 is less considered as an option due to the smaller anatomical S1 spinous process and the higher stresses from the immobile sacrum. Our objective was to evaluate the outcomes of an IFD used as a stand-alone treatment for spinal stenosis at L5-S1 and L4-5 compared to historical data on open laminectomies. Methods: Prospective comparative cohort study (Level 2) looking at collected preoperatively and postoperatively Visual Analog Scores (VAS) and Oswestry Disability Index (ODI) data, complications, and revision rates on 100 consecutive patients with spinal stenosis treated with midline decompression and InSpan (InSpan LLC, Malden, MA, USA) IFD, at L5-S1 and L4-5, up to five-year follow-up. All patients were treated by a single surgeon in an academic private practice. Historical published outcome data for open laminectomies were compared. Results: Among the 100 patients, 45 underwent surgery at L5-S1 with a mean VAS pain score that decreased by 75% and ODI improved by 63% (P<0.001). Fifty-five patients had surgery at L4-5 with mean VAS and ODI scores improved by 80% and 66% (P<0.001) respectively. Preoperative and postoperative ODI and preoperative VAS scores were similar at L5-S1 and L4-5, however, postoperative VAS scores were significantly less for L4-5 versus L5-S1 (P<0.01). All surgeries were completed in less than one hour. There was a total of one L4-5 revision (1.8%) and two L5-S1 revisions (4.4%). Comparable laminectomy data showed decrease in VAS and ODI scores by 51% and 62% (P<0.05). The reoperation rate for laminectomies at five to ten years varied up to 24%. Conclusions: Spinal stenosis patients treated with midline decompression and InSpan IFD, used as a stand-alone treatment for interspinous-interlaminar fixation, at L4-5 and L5-S1, showed improved outcome scores and low complication and revision rates at five years and were comparable to historical open laminectomy data. InSpan is a successful substitute for laminectomies in selected patients and was performed in less than 60 minutes. We recommend choosing the appropriately sized implant to achieve adequate distraction decompression to avoid recurrent symptoms.