INTRODUCTION: We have performed endoscopic decompression for lumbar degenerative spondylolisthesis (DS) regardless of the degree of slippage and instability. Sagittalization of the facet joint (FS) has been reported to be a risk factor for lumbar spondylolisthesis, but few reports have been published on the relationship between FS and the postoperative results of endoscopic decompression. This study aimed to clarify the relationship between FS in DS and the medium-term results of endoscopic decompression.

METHODS: Of the 35 patients who underwent endoscopic decompression with a diagnosis of DS (slippage of ≥3 mm on the X-ray standing view) from April 2013 to October 2018, 32 patients whose images could be evaluated 2 years after surgery were investigated. The mean postoperative follow-up period was 3 years and 7 months. Bilateral facet joint angles were measured at the height of the lower margin of the slip level on preoperative CT, and the mean value was taken as the facet joint angle. The following items were compared based on the presence or absence of FS. The primary endpoint was the change in slippage rate at the decompressed level. As a secondary endpoint, the reoperation rate caused by the decompressed level was investigated. Age, sex, preoperative facet joint width, and postoperative joint survival rate were also investigated as adjusting factors. Regarding the presence or absence of FS, it was judged that the risk factor for DS in the previous study was ≥58 degrees with FS, and <58 degrees without FS.

RESULTS: There were 22 patients with FS (11 males, 11 females, mean age at surgery 67.9 years) and 11 without FS (2 males, 9 females, mean age 65.7 years). There were significantly more females without FS. The mean preoperative facet joint angle was 67.2 ± 6.6 degrees with FS and 47.4 ± 8.5 degrees without FS. No significant differences in preoperative facet joint width or the postoperative facet joint survival rate were observed between the groups. The postoperative % slip change was 1.9 ± 1.1% with FS and 1.6 ± 1.6% without FS, showing no significant difference, and the progression of slip was less than 2% with or without FS. There was one reoperation without FS. That is, FS is unlikely to affect postoperative slip progression or the reoperation rate.

CONCLUSION: Endoscopic decompression is useful for DS because it is not affected by sagittalization of the facet joint.