Radiographic Assessment of Shoulder Position in 619 Idiopathic Scoliosis Patients: Can T1 Tilt Be Used as an Intraoperative Proxy to Determine Postoperative Shoulder Balance?

Background:The purpose of this study is to assess radiographic shoulder measures from the preoperative to the postoperative time period, specifically to determine whether T1 tilt could be used as an intraoperative proxy for shoulder balance determination. This study focused on radiographic shoulder measures of 619 adolescent idiopathic scoliosis patients who underwent spinal deformity surgery.Methods:A prospective, multicenter database of adolescent idiopathic scoliosis was queried to identify all patients who had undergone spinal deformity surgery with >2 years of follow-up postoperatively. Radiographic analysis focused on measures of shoulder balance: T1 tilt, clavicle angle, and radiographic shoulder height.Results:A total of 619 patients were included in this analysis. Mean age at surgery was 14.8 years with 83% female. Mean preoperative curve size was 58.0 degrees. Mean T1 tilt preoperatively was -0.10 degrees and postoperatively 2.42 degrees. Mean clavicle angle preoperatively was -1.39 degrees and postoperatively 0.79 degrees. Mean radiographic shoulder height preoperatively was -7.04 mm and postoperatively 1.63 mm. All 3 radiographic parameters demonstrated reasonable correlation preoperatively and postoperatively to each other. To assess the viability of T1 tilt as an intraoperative proxy for shoulder balance, standardized ratios between the variables were created. Analysis of these ratios demonstrated little or no relationship preoperatively to postoperatively, hence the relationship of T1 tilt to radiographic shoulder height does not remain constant.Conclusions:Analysis of the relationship of T1 tilt to radiographic shoulder height from preoperative to postoperative did not demonstrate consistency. Lenke 3 and 6 curve patterns demonstrated preoperative to postoperative correlation, both with nonstructural proximal thoracic curves; however, for the remaining curve patterns T1 tilt cannot be used as an intraoperative proxy for shoulder balance.Level of Evidence:Level IV.