Introduction

It is often difficult to select the surgical method for cases of lumbar spinal stenosis (LSS) with complex pathologies. For the cases of LSS with old vertebral fracture, fusion surgery may be generally preferred, but we have selected minimally invasive decompression surgery for those cases without instability or the symptom due to foraminal stenosis in our institution. However, there has not been few reports about the influence of prevalent vertebral fracture on the clinical outcome of decompression surgery for LSS. The purpose of this study was to investigate the feature of LSS with old vertebral fracture and the clinical results of minimally invasive posterior decompression.

Methods

In this study, we retrospectively reviewed prospectively collected data of 773 cases who underwent minimally invasive posterior decompression for LSS and followed up for more than 2 years. We extracted the cases with old prevalent fracture in the decompression level. The cases with fresh fracture were excluded in this study. To evaluate the feature of the pathology, we investigated the presence of anterior/posterior spondylolisthesis, lateral- slip, and coronal wedging on preoperative X-ray. For the clinical outcome, we investigated additional surgery/reoperation, and preoperative and postoperative (2years) visual analogue scale (VAS) for low back pain, leg pain and leg numbness, and JOA score for low back pain. We also extracted the twice number of control cases without fracture by using propensity score-matching based on age, sex, the number of decompression level, and the operative method (under microscope or micro-endoscope) and compared the items between the two groups.

Results

Twenty-six out of 773 cases (3.4%) had one or more prevalent vertebral fracture in the decompression level. L4 fracture was the most common, and multiple fractures were found in 7cases. In the intervertebral level with prevalent fracture, anterior/posterior spondylolisthesis was found in 54%, lateral slip in 27%, and coronal wedging in 42%, but there was not significant difference in the prevalence compared with the control group (anterior/posterior spondylolisthesis 38%, lateral slip in 23%, and coronal wedging in 42%). Pre-operative VAS for low back pain, leg pain and leg numbness and JOA score were significantly improved at 2years after surgery in both groups, and there was not significant difference in the degree of improvement. The rate of additional surgery in 2yrs was 15% in the group with old fracture and 10% in the control group. There was not significant difference in the rate, but all the additional surgery were fusion surgery in the group with old fracture whereas 20% in the control group.

Discussion

The clinical outcome of minimally invasive posterior decompression for lumbar spinal stenosis with prevalent vertebral fracture was similar with that for lumbar spinal stenosis without fracture. Minimally invasive decompression surgery offers favorable outcome also for LSS with prevalent vertebral fracture without instability or foraminal stenosis, and not all the LSS cases with prevalent fracture require fusion surgery.