Radiographic outcomes of endoscopic decompression for lumbar spinal stenosis

OBJECTIVELumbar central stenosis can theoretically be decompressed with minimal bone removal via an endoscopic approach. Although multiple studies have demonstrated an adequate radiographic decompression, none has quantified the volume of bone removal after endoscopic decompression. The objective of this study was to quantify the 3D volume of bone removed from the lamina and facet joints during endoscopic decompression for lumbar central and lateral recess stenosis.METHODSThis retrospective study included adults with lumbar spinal stenosis who underwent endoscopic decompression of a single level or 2 noncontiguous lumbar levels. Central stenosis on MRI was graded preoperatively and postoperatively using the Schizas scale. A computer program was developed in MATLAB to semiautomatically perform a 3D volumetric analysis of preoperative and postoperative lumbar CT scans. The volumetric percentage of bone removed from the lamina and facet joints ipsilateral and contralateral to the side of approach was quantified.RESULTSNineteen patients with 21 treated lumbar levels were included in the study. Preoperatively, the number of levels with Schizas stenosis grades B, C, and D were 5, 12, and 4, respectively. Stenosis grades improved postoperatively to grades A, B, C, and D for 17, 3, 1, and 0 levels, respectively. All levels improved by at least 1 stenosis grade. The volumetric percentage of laminar bone removed was 15.5% (95% CI 11.2%-19.8%, p < 0.001) from the ipsilateral lamina and 8.8% (95% CI 5.7%-11.8%, p < 0.001) from the contralateral lamina. The percentage of facet joint resection was 5.3% (95% CI 4.2%-6.4%, p < 0.001) and 4.3% (95% CI 2.2%-6.4%, p < 0.001) for the ipsilateral and contralateral facet joints, respectively. Average pain scores, as measured by the visual analog scale, improved from 7.9 preoperatively to 2.2 by 3-10 months postoperatively (p < 0.001).CONCLUSIONSEndoscopic lumbar decompression achieves improvement in the radiographic grade of lumbar central stenosis with minimal bone removal from the lamina and facet joints. Future prospective studies are needed to validate the findings of this study with more comprehensive clinical outcomes.