Postoperative neck tilt in Lenke 1 and 2 AIS patients after correction surgery: a novel predictive index

Yilin Yang,Haijian Ni,Zongde Yang,Ming Li,Mingyuan Yang,Changwei Yang,Jian Zhao,Jinyi Bai,Kai Chen

doi:10.1186/s12891-019-2792-9

Abstract

BackgroundPostoperative neck tilt (PNT) is a phenomenon in adolescent idiopathic scoliosis (AIS) patients which is distinct form shoulder imbalance. There were scarce studies performed to explore the risk factors for PNT in Lenke 1 and 2 AIS patients, and whether it can be predicted after surgery remains unknown. The objective of this study is to explore the prevalence and risk factors for PNT, and introduce an index for prediction of PNT in Lenke 1 and 2 AIS patients after correction surgery.MethodsMedical records of Lenke 1 and 2 AIS patients who received correction surgery were reviewed from February 2013 to February 2015. Posteroanterior films were evaluated before surgery and at 2 years’ follow-up. Patients were divided into two groups according to whether PNT occurred at the 2 years’ follow-up. Risk factors of PNT were analyzed, and PNT Index was proposed and verified.ResultsOne hundred two Lenke 1 and 2 AIS patients were recruited in this study. The prevalence of PNT after correction was 40.2%. According to the postoperative CAT (Cervical Axis Tilt), patients were divided into two group: PNT group (CAT≧5°, n = 41) and non-PNT group (CAT< 5°, n = 61). Postoperative T1 tilt, preoperative proximal thoracic curve (PTC), postoperative PTC and postoperative coronal balance (CB) were significantly different between two groups. Logistic regression showed that postoperative PTC and postoperative CB were the primary risk factors for PNT, which could be predicted by the regression equation: PNT Index = 1.1 x postoperative PTC (degrees) - 0.9 x postoperative CB (millimeters). On the basis of ROC curve, if PNT Index was more than 10, the occurrence rate of PNT was 86%. On the contrary, the rate of no PNT phenomenon was 80%.ConclusionPostoperative PTC and postoperative CB were the important factors for PNT in Lenke 1 and 2 AIS patients. Sufficient correction of PTC and moderate correction of CB should be recommended when operating on Lenke1 and 2 AIS patients.

Highlights

Postoperative neck tilt (PNT) is a phenomenon in adolescent idiopathic scoliosis (AIS) patients which is distinct form shoulder imbalance
This kind of internal fixation can frequently result in overcorrection, especially for the main thoracic curve (MTC), which can result in shoulder imbalance because the proximal thoracic curve (PTC) fails to compensate when fusing to upper thoracic segment [5]
Translation of apex vertebrae (AVT) was used to measure the distance between apex vertebra of curve and CSVL.CA (Clavicle angle: angle between the line connecting the lateral end of both clavicle with the horizontal plane) and RSH (Radiographic shoulder height: difference between the horizontal lines of the level of soft tissue shadow above the acromioclavicular joint) were measured to evaluate the shoulder balance

Summary

Introduction

Postoperative neck tilt (PNT) is a phenomenon in adolescent idiopathic scoliosis (AIS) patients which is distinct form shoulder imbalance. There were scarce studies performed to explore the risk factors for PNT in Lenke 1 and 2 AIS patients, and whether it can be predicted after surgery remains unknown. The objective of this study is to explore the prevalence and risk factors for PNT, and introduce an index for prediction of PNT in Lenke 1 and 2 AIS patients after correction surgery. With constant development in newer techniques and instrumentation, great improvements have been achieved in correction rate of AIS, especially using pedicle screws. Shoulder imbalance is getting increasing recognition of importance as this disastrous complication is observed commonly in AIS patients after correction surgery, which has great influence on patients’ appearance and HRQOL. This kind of internal fixation can frequently result in overcorrection, especially for the main thoracic curve (MTC), which can result in shoulder imbalance because the proximal thoracic curve (PTC) fails to compensate when fusing to upper thoracic segment [5]

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