[Effects of pelvic balance after posterior reduction of balanced L5-S1 Ⅲ-grade isthmic spondylolisthesis in adults].

OBJECTIVE: To observe the changes in pelvic balance after posterior reduction of balanced L5-S1 Ⅲ-grade isthmic spondylolisthesis in adults.

METHODS: A total of 18 adult patients with balanced L5-S1 Ⅲ-grade isthmic spondylolisthesis were retrospectively studied after successful treatment by posterior decompression, reduction and L5-S1 interbody fusion in Department of Orthopedic Surgery, the First Affiliated Hospital of Soochow University from October 2009 to October 2014.L5-S1 of eight patients were fixed with pedical strews, while others were fixed upgrade to L4.Spino-pelvic parameters: slipping percentage (SP), spondy slip angle (SSA), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT) and lumbar lordosis (LL) were measured on standing lateral view radiograms.The changes in pelvic balance were analyzed after posterior reduction.

RESULTS: All the patients experienced significant changes in SP and SSA with (42.4%±8.3)% and (9.8±4.9)°improved significantly while no significant differences were recorded in PI, PT, SS and LL. PI, PT, SS and LL passed from an average(61.1±6.2)°, (16.2±4.5)°, (44.8±2.9)°, (51.3±9.3)°preoperatively to (61.4±6.1)°, (14.9±4.0)°, (46.5±3.0)°, (48.6±7.0)°respectively.According to K-means cluster analysis, pelvic balance improved postoperatively.No significant correlation was found for ΔPT, ΔSS with ΔSP, while ΔPT and ΔSS had a significant correlation with ΔSSA (correlation coefficient -0.77 and 0.82 respectively).

CONCLUSION: Posterior SSA reduction in adults with balanced L5-S1 Ⅲ-grade isthmic spondylolisthesis can improve the former pelvic balance.