Dynamic changes of pelvic incidence after pelvic fixation with second sacral alar-iliac in patients with degenerative scoliosis / 中华骨科杂志

ABSTRACT

Objective:To investigate how pelvic incidence (PI) would change during the follow-up in degenerative scoliosis (DS) patients who underwent second sacralalar-iliac (S 2AI) fixation and identify the possible factors associated with the changes in PI. Methods:The DS patients who underwent long fusion to pelvis with S 2AI fixation with a minimum follow-up of two years between November 2014 to January 2017 were retrospectively reviewed in this study. The following sagittal radiographic parameters were measured, including pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), PI minus LL (PI-LL), and sagittal vertical axis (SVA) at pre-operation, post-operation and 2-year follow-up. Patients were divided into two groups at immediate post-operation PI decreased less than 5° or increased (Group PI stabilization); PI decreased larger than 5° (Group PI activity). Descriptive statistics were calculated for all patients in the form of mean value and standard deviation (SD). Comparisons of means between variables were performed using an unpaired Student's t test. Pearson correlation coefficienttest was performed to determine the correlations between all radiographic variables. Inter- and intra-observer reliability was assessed using intraclass correlation coefficient (ICC). The internal consistency of the measurements was characterized as excellent ( ICC≥0.9), good (0.7≤ ICC<0.9), acceptable (0.6< ICC≤0.7), poor (0.5≤ ICC<0.6), or unpredictable ( ICC<0.5). Results:There were no significant differences in terms of age, sex, radiographic measurements and scores of SRS-22 between twogroups preoperatively ( P>0.05). 80 DS patients with a mean age of 55.3±16.2 years were enrolled in this study with a mean follow-up period of 34.6±8.7 months. At post-operation, 39 patients (38.8%) were in group PI stabilization whose PI decreased from 45.7°±11.4° to 45.3°±11.2° with no significant difference; while the other 41 (61.2%) were in group PI activity whose PI significantly decreased from 51.6°±14.5° to 40.9°±14.0°. At the last follow-up, 24 patients (49%) in group PI activity had PI returned with an increase of larger than 5°; while the other 25 (51%) showed no increase with a mean &Delta;PI change of -4.2°. Subgroup comparison revealed that &Delta;PI, post-operation PI, post-operation PT and age were significantly different between the two subgroups. Pre-operation PI, post-operation PI, post-operation PT, post-operation PI-LL were significantly correlated with &Delta;PI at the last follow-up. Logistic regression analysis showed that post-operation PI was the associated factor ( OR=0.87, P=0.024). Conclusion:PI decreased in more than half of DS patients after spinal surgery using S 2AI screws, while returned among 48% of them during 2-year follow-up. Lower pre-operation PI, post-operation PI and PT were strongly associated with the return of PI.