Sacral Agenesis: A Neglected Deformity That Increases the Incidence of Postoperative Coronal Imbalance in Congenital Lumbosacral Deformities

A retrospective study.To identify if there is a link between sacral agenesis (SA) and post-operative coronal imbalance in patients with congenital lumbosacral deformities.This study reviewed a consecutive series of patients with congenital lumbosacral deformities. They had a minimum follow-up of 2 years. According to different diagnosis, they were divided into SA and non-SA group. Comparison analysis was performed between patients with and without post-operative coronal imbalance and risk factors were identified.A total of 45 patients (18 in SA group and 27 in non-SA group) were recruited into this study, among whom 33 patients maintained coronal balance while 12 demonstrated postoperative coronal imbalance at last follow-up (14.32 ± 7.67 mm vs 35.53 ± 3.91 mm, P < 0.001). Univariate analysis showed that preoperative lumbar Cobb angle, immediate postoperative coronal balance distance and diagnosis of SA were significantly different between patients with and without post-operative coronal imbalance (P < 0.05). Binary logistic regression analysis showed that SA was an independent risk factor for postoperative coronal imbalance.As an independent risk factor for postoperative coronal imbalance, high level of suspicion of SA should be aware in children with congenital lumbosacral deformities. Sufficient bone grafts at sacroiliac joint are recommended for SA patients to prevent postoperative coronal imbalance.