The influence of different fusion segments on pelvic incidence in patients with degenerative scoliosis

English Keywords:Scoliosis  Kyphosis  Lumbar degeneration  Spinal fusion  Pelvis incidence

English Abstract:

  【Abstract】 Objectives: To investigate the influence of different fusion segments on pelvic incidence in patients with degenerative scoliosis. Methods: The present study reviewed patients with degenerative kyphoscoliosis who underwent posterior long fusion between May 2010 and April 2018. 42 patients were included in our study, andamong which there were 5 males and37 females, with a mean age of 60.6±6.9 years old(50-69). According to different distal fusion segment, patients were divided into two groups, group A(fused at L5, 14 patients) and group B(fused at pelvis, 28 patients). The Cobb′s angle, regional kyphosis(RK), lumbar lordosis(LL), sagittal vertical axis(SVA), pelvic incidence(PI), pelvic tilt(PT), and sacral slop(SS) were recorded before and after operation. The differences of pelvic incidence postoperatively between the two groups were compared and their relationships with the parameters of sagittal plane before operation were analyzed. Results: There was no significant difference in Cobb′s angle, regional kyphosis(RK), number of internal fixation segments, gender, and age between the two groups at pre-operation. The pelvic incidence changed from 46.4°±16.7° preoperatively to 44.1°±13.6° postoperatively without statistical significance(P=0.104) in group A, while it significantly decreased from 50.9°±13.6° to 44.0°±13.7°(P<0.05) in group B, with a postoperative decrease of more than 5° in 15 patients(53.6%). Inter-group analysis showed that changes in PI, preoperative PI-LL and postoperative LL were significantly different between both groups. Correlation analysis showed that the changes in PI, preoperative LL and PI were significantly associated. The formula provided by the regression analysis was ΔPI=-3.117+0.201×PrePI-0.116×PreLL. Conclusions: In patients with degenerative scoliosis who underwent posterior long segment internal fixation, the pelvic incidence is more possible to decrease significantly in those utilizing S2-alar-illiac screws rather than those fixed distally to L5. The significant change of pelvic incidence in pelvic fixation group may be related to larger PI and greater degree of sagittal imbalance before operation.