Analysis of the spino-pelvic parameters for symptomatic adjacent segment degeneration after posterior lumbar interbody fusion

Purpose: To identify the risk factors of symptomatic adjacent segment degeneration (SASD) after posterior lumbar interbody fusion (PLIF) and to figure out the correlation between spino-pelvic parameters and SASD. Methods: 21 patients who with postoperative SASD during an average follow-up time of 42.14 +/- 25.97 months were retrospectively analyzed as the study group. The controlled group consisted of 96 patients who developed no SASD after PLIF. Characteristics of the including patients were investigated in both groups. The spino-pelvic parameters including pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) were calculated pre- and post-operatively. Univariate and multivariate regression analysis were then performed to identify the related risk factors for SASD after PLIF. Results: The patients in the SASD group showed a significant reduction of postoperative LL (P=0.002) and significant increase of postoperative PT (P=0.005). The postoperative LL (OR=0.911, P=0.004), postoperative PT (OR=1.121, P=0.007) and bone mineral density (BMD) (OR=0.536, P=0.023) were detected to be the most important risk factors for SASD after PLIF while the body mass index (BMI) was selected as a suspicious factor (P=0.068). Conclusion: The risk factors of SASD after PLIF turn out to be multifactorial, the spino-pelvic parameters play an important role in SASD. The BMD, postoperative LL and postoperative PT are inextricably linked with SASD. Our study demonstrates the necessity to restore the PT and maintain the LL in the surgery to reduce the occurrence of SASD.