CHANGES IN RADIOGRAPHIC PARAMETERS AFTER MINIMALLY INVASIVE LUMBAR INTERBODY FUSION

Objective : This study aims to evaluate changes in lumbosacral parameters after minimally invasive lumbar interbody fusion. The secondary aim was to evaluate whether interbody cage shape (crescent shaped or rectangular) would influence the results. Method : Retrospective analysis of 70 patients who underwent one or two level lumbar interbody fusion through a minimally invasive posterolateral approach. This included midline preservation and unilateral facetectomy. Pre- and postoperative (three to six months postoperative) radiographs were used for measuring lumbar lordosis (LL), segmental lordosis (SL) at the level of interbody fusion, and sacral slope (SS). Further analyses divided the patients into Roussouly lumbar subgroups. Results : LL was significantly reduced after surgery (59o:39o, p=0.001) as well as the SS (33.8o:31.2o, p=0.05). SL did not change significantly (11.4:11.06, p=0.85). There were no significant differences when comparing patients who received crescent shaped cage (n=27) and rectangular cage (n=43). Hypolordotic patients (Roussouly types 1 and 2) had radiographic improvement in comparison to normolordotic and hyperlordotic groups (types 3 and 4). Conclusion : Minimally invasive lumbar interbody fusion caused reduction in lumbosacral parameters. Cage shape had no influence on the results.