Objectives:

Mini-invasive approaches have grown substantially these last decades in spinal surgery, notably for lumbar decompressions and fusion, with advantages over open approaches in terms of morbidity reduction. However, to our knowledge, no study has measured on MRI the amount of central decompression obtained by MIS approach. The goal of this study was to precisely measure the decompression of central stenosis by unilateral MIS approaches.

Methods:

The files of 42 patients that had a MIS lumbar fusion with central decompression for central stenosis were reviewed. All patients had a pre- and post-operative MRI, that allowed on T2 axial images to classify the central stenosis according to Schizas’ classification and measure the dural sac cross-sectional area (DSCA) and the anteroposterior diameter (DAP). The statistical analysis was made with paired t-test.

Results:

Fifty-six levels were analyzed, mostly L4L5 (58%). The mean pre-operative DSCA was 70.53mm² and the mean post-operative DSCA was 172.2mm². The mean pre-operative DAP was 6.15mm and post-operative was 10.68 mm. Pre-operatively, the levels analyzed were rated B, C or D according to Schizas for 53 out of 56 levels and A1-4 for 51 out of 56 levels in post-operative. All the results were statistically significant (p<0.001).

Conclusion:

Decompression, assessed by MRI, seems to be equivalent by MIS approach to open laminarthrectomy. MIS approaches have been studied clinically in these indications with very satisfying results. As a conclusion, MIS approaches seems to be a relevant and efficient option in the treatment of lumbar degenerative stenosis.

Level of evidence:

IV, retrospective study.