Five-year radiological outcomes between decompression alone and decompression with an interlaminar device for lumbar spinal stenosis.

Background: There is limited literature regarding radiological outcomes in the use of interlaminar devices as an adjunct to decompression compared to decompression alone (DA) for symptomatic lumbar spinal stenosis (LSS). This study aims to assess and compare 5-year radiological outcomes following spinal decompression and decompression with ILD (D + ILD). Methods: We conducted a retrospective review of prospectively collected data of 94 patients who underwent spinal decompression with or without ILD insertion between 2007-2015. Patients with symptomatic LSS who met the study criteria were offered spinal decompression with or without ILD insertion. Those patients who accepted ILD insertion were placed in the D + ILD group (n=39); while those opting for DA, were placed in the DA group (n=55). Radiological indices were assessed preoperatively, immediate post-operative, 2 years and 5 years postoperatively. Results: There were a total of 94 patients with 55 in the DA group and 39 in the D + ILD group. In both groups, there was no significant change post-operatively in the sagittal balance parameters namely, the mean pelvic incidence, pelvic tilt, sacral slope and pelvic incidence minus lumbar lordosis (PI - LL) during the 5-year follow-up. Comparing between the groups, there was no significant difference in sagittal balance parameters. Comparing between DA versus D + ILD, there was no significant difference in overall lordosis, but the D + ILD had a significant reduction in sagittal angle (at the index level) of 2.3° compared to the DA group (P=0.01). In the control group, there was no significant difference in the anterior disc, posterior disc and foraminal height post-operatively. In the D + ILD group, there was a significant mean increase of 1.3 mm in anterior disc height, 1.8 mm in posterior disc height and 4.7 mm in foraminal height compared to the control group. In both groups, there was significant improvement in all clinical outcomes namely 36-item short form survey physical component summary (SF36 PCS), 36-item short form survey mental component summary (SF36 MCS) and visual analogue scale (VAS). Comparing the groups, there was significant improvement in the D + ILD group in SF36 MCS (P=0.01) but no difference in SF36 PCS or VAS. Reoperation rates were equivalent. Conclusions: Our study found that in the management of lumbar stenosis, the use of an ILD as an adjunct device compared to DA had significant improvement in anterior disc, posterior disc and foraminal height with expected focal kyphosis at the level of intervention without change in the lumbar lordosis and sagittal balance at 5 years.