A Novel Method for Predicting Ideal Postoperative Upper Instrumented Vertebra Tilt to Prevent Lateral Shoulder Imbalance after Scoliosis Correction Surgery

Abstract Background: Lateral shoulder imbalance (LSI) is reflected radiologically by the clavicle angle (CA). How to achieve postoperative lateral shoulder balance (LSB) after scoliosis correction surgery remains unclear.Methods: In the current study, by using the preoperative upper instrumented vertebra (UIV) tilt, CA, the flexibility between T1 and the UIV, the ideal postoperative UIV tilt was predicted based on the following formula: ideal postoperative UIV tilt = preoperative UIV tilt – the flexibility between T1 and UIV – preoperative CA. The reliability of the formula was verified through a retrospective analysis, and 76 scoliosis patients were enrolled and divided into three groups based on the postoperative shoulder balance: 1) the whole group (n = 76); 2) the LSI group (n = 26); and 3) the LSB group (n = 50). The pre- and postoperative CA, UIV tilt, T1 tilt, flexibility between T1 and the UIV, and ideal UIV tilt were measured or calculated using the formula mentioned above. The feasibility of this method in achieving LSB by establishing the predicted ideal UIV tilt intraoperatively using the improved crossbar technique was verified through a prospective analysis, and 13 scoliosis patients were enrolled. Results: In the retrospective study, there was a significant correlation between the difference in the actual and ideal postoperative UIV tilt values and the postoperative CA, with correlation coefficients in the whole, LSI and LSB groups of 0.981, 0.982 and 0.953, respectively (p < 0.001). In the prospective study, all patients achieved satisfactory LSB, with a correlation coefficient between the difference in the actual and ideal postoperative UIV tilt values and the postoperative CA of 0.939 (p < 0.001).Conclusions: Using the formula preoperatively to predict an ideal postoperative UIV tilt and controlling the intraoperative UIV tilt with the improved crossbar technique may be an effective digital method for achieving postoperative LSB and has important clinical significance.