Evaluation of spinopelvic alignment according to Roussouly classification can predict the occurrence of adjacent segment disease after lumbar fusion

Abstract

Objective: To investigate the correlation of spinopelvic alignment according to Roussouly classification on the occurrence of adjacent segment disease (ASD) in the patients undergoing fusion surgery for lumbar degenerative diseases. Methods: A cross-sectional study. Clinical data of 166 consecutive patients who had undergone lumbar fusion between January 2009 and January 2019 in the Affiliated Changzhou Second People's Hospital of Nanjing Medical University and Affiliated Drum Tower Hospital of Medical School of Nanjing University were retrospectively reviewed. There were 59 males and 107 females, with an average age of (58.6±9.5) years (ranged 41-78 years). Fusion length averagely spanned (1.7±0.7) levels (ranged 1-3 levels). The patients were classified by both "theoretical" (based on pelvic incidence (PI)) and "current"(based on sacral slope (SS)) Roussouly types. The patients were classified as "matched" if their "current" shape matched the "theoretical" type and otherwise as "unmatched". Multivariate logistic regression analysis of the variables recruited from univariate analyses was performed to identify the factors independently associated with the development of ASD after lumbar fusion. Results: The average follow-up duration after initial surgery was (49.2±20.7) months (ranged 25 to 134 months). Thirty (18.1%, 30/166) patients were diagnosed as ASD. Postoperatively, two thirds of the patients who suffered ASD after surgery were unmatched, while 36.8% (50/136) of the patients without ASD had unmatched type. Univariate analyses showed that older age, more fusion levels, float fusion, pre-and postoperative worse spinopelvic alignment, and postoperative unmatched Roussouly type were identified as risk factors of ASD. Multivariate logistic regression analysis identified postoperative Roussouly type mismatch (OR=3.310, 95%CI: 1.282-8.545, P=0.013), old age (OR=1.074, 95%CI: 1.019-1.131, P=0.008) and postoperative SS (OR=0.928, 95%CI: 0.865-0.995, P=0.036) as the independent risk factors of development of ASD after lumbar fusion. Conclusion: A significant association between postoperative sagittal malalignment and occurrence of ASD is detected, the evaluation of sagittal alignment by Roussouly classification could help predict the occurrence of ASD.