A Prospective Study of Patient-Reported Outcomes for Two Years After Lumbar Surgery Augmented With Diam®interspinous Implant

Purpose: The device for intervertebral assisted motion (DIAM™) is an interspinous (ISP) implant used to augment surgical decompression of lumbar degenerative conditions: Lumbar spinal stenosis [LSS; foraminal (FS) or central canal (CS)], herniated and degenerated disc disease, facet joint pain syndrome (FJPS) and minor degenerative spondylolisthesis (DS). Limited evidence guides its use in defined clinical indications, while few studies demonstrate effect according to clinically meaningful change (MCID). This prospective longitudinal study examined the efficacy of DIAM-augmented decompression surgery in the broad application of a single-center clinical reality. Methods: Eighty-one consecutive cases [37F, 44M; 52 years (SD 13)] were examined for two years after DIAM-augmented decompression surgery. Patient-reported pain [back and leg; visual analogue scale (VAS)], function [Oswestry disability index (ODI)], and satisfaction (Likert scale) were serially examined and referenced to contemporary MCID thresholds. Subjects were classified into anatomical and diagnostic categories and analyzed according to subgroups to better inform clinical pathways. Serial change was assessed with Scheffe post-hoc test; change scores with unpaired t-tests and descriptive statistics (p < 0.05). Results: Subjects reported 20.4% (SD 29.5; p < 0.0001) mean improvement in back pain, 20.3% (SD 30.6; p < 0.0001) in leg pain, and 15.1% (SD 20.8; p < 0.0001) in function at two years postoperatively. Greatest improvement was seen at six weeks for back pain (by 30.5%; p < 0.0001) and leg pain (by 29.4%; p < 0.0001) and three months for function (by 18.7%; p < 0.0001). Leg pain deteriorated between six weeks and 18 months (p < 0.05). There were more responders at one compared to two years after surgery. FS cases showed superior improvement compared to DS subjects (p < 0.05). Cases receiving multiple adjunctive surgical decompressions in addition to their DIAM had superior improvement than those receiving a single procedure (p < 0.05). Conclusions: Clinical improvement in back pain, leg pain and function were achieved to two years in a single-center cohort of 81 cases with lumbar degenerative disease who received DIAM-augmented decompression surgery. Subsets of the sample had a superior sustained response including foraminal/lateral recess stenosis patients and cases treated with > 1 adjunctive decompression techniques. The need for assessing homogeneous cohorts in future studies is emphasized.