Does the pre-operatıve l5-tılt predıct post-operatıve coronal ımbalance ın patıents wıth lenke type v adolescent ıdıopathıc scolıosıs? A retrospectıve revıew of 84 cases

Abstract

INTRODUCTION: Many factors have been proposed to result in early coronal imbalance and lumbosacral obliquity in patients with Lenke Type V adolescent idiopathic scoliosis(AIS) following selective fusion surgery.The aim of this study was to evaluate, whether pre-operative L5 tilt had any effect on immediate post-operative coronal imbalance in patients with Lenke type V AIS who underwent selective fusion,whether immediate coronal imbalance could be predicted by measuring the L5 tilt and whether immediate coronal imbalance was permanent or temporary. METHOD: 84 patients with Lenke Type V AIS who underwent selective fusion between 2010-2015 were included. Demographical data were collected from patients’ files,while radiographic measurements were undertaken from standing anteroposterior and lateral X-rays.Coronal balance was defined as a difference less than 20mm between C7 plumb line (C7PL) and central sacral vertical line (CSVL). As a result of the evaluation of coronal balance (CB) on post-operative standing X-ray, patients were divided into two groups: immediate post-operative CB versus immediate post-operative coronal imbalance (CIB). Pre- and post-operative L5 tilts,amounts postop immediate and at the last follow-up coronal balance and degrees of total correction angles were compared. RESULTS: 84 patients had a mean age of 16.65 and a mean follow-up period of 61.54 months.48 patients were grouped in immediate CB (mean C7PL-CSVL:10.34mm), while 36 patients were grouped in immediate CIB (mean C7PL-CSVL:30.52mm). 70% (26/36) of patients in immediate post-operative CIB group was detected to regain CB at the last follow up (mean C7PL-CSVL:12.88mm). Mean pre-op L5 tilt in patients with immediate CB was 11.37°,while it was 21.01° in patients with immediate CIB (p<0.001). Pre-operative high L5 tilt was detected to be a risk factor for the development of post-operative immediate CIB with high statistical significance, while the cut-off value of pre-op L5 tilt was calculated as 20.5°. Mean post-op L5 tilt in patients with immediate CB and CIB were 5.1° and 6.67° respectively (p=0.27). Mean amount of total correction of CB groups was 38.72°, while it was 40.10° in CIB group (p=0.27). CONCLUSION: High pre-operative L5 tilt (cut-off value: 20.5°) was found to be a risk factor with high statistical significance for the development of coronal imbalance in patients with Lenke Type V AIS following selective fusion. Pre-operative L5 tilt above 20.5° might be used as a predictive factor for the development of immediate post-operative coronal imbalance. This study showed that pre-operative L5 tilt was one of the most important factors to predict immediate coronal imbalance.