Comparison of unilateral hemilaminotomy and bilateral hemilaminotomy according to dural sac area in lumbar spinal stenosis.

INTRODUCTION: Unilateral hemilaminotomy (ULH) and/or bilateral hemilaminotomy (BLH) with limited facetectomy are defined approaches to decompress the thecal sac and exiting lumbar nerve roots without increasing the risk of subsequent spinal instability.

METHODS: We retrospectively analyzed 18 cases with degenerative lumbar spinal stenosis (LSS) with BLH or ULH that was performed in 11 and 7 cases, respectively. Magnetic resonance imaging (MRI) was performed at the follow-up examination and dural sac area (DSA) was calculated on T(2)-weighted MRI images and then compared statistically. In addition, the economic and functional status of the patients were evaluated with the Prolo scale.

RESULTS: The mean preoperative values on the visual analogue scale (VAS) were 7.1 for lumbalgia and 7.0 for leg pain, respectively. These values were calculated as 4.8 and 4.4 at the follow-up, respectively. The VAS was significantly improved after operation compared to preoperative values (p=0.001). The mean value of the DSA was 84 (+/-32) mm(2) before the operation and 126 (+/-35) mm(2) at the follow-up and the comparison was statistically significant (p=0.001). No statistical correlation was found between VAS and DSA or between VAS and ULH-BLH groups, however, DSA of the BLH cases was significantly higher than in the ULH group (p=0.035). There was a significant negative correlation between VAS scores (back and leg pain) and Prolo status. However, there was no significant difference between DSA and Prolo scores, and between ULH or BLH groups in terms of Prolo scores.

CONCLUSION: A unilateral approach with bilateral decompression and bilateral approach with bilateral hemilaminotomy are both minimal invasive, adequate and safe approaches with excellent prognosis. However, BLH leads to a bigger expansion of DSA.