Shoulder Balance and Scoliosis: The Unresolved Issue

Abstract

Background Data: The main indication of surgery in patients with AIS is better function and cosmesis. Shoulder balance should be considered amongst cosmetic parameters that are strongly associated with patient satisfaction after surgery in patients with AIS. Proper correction of the main and proximal thoracic curves in conjunction with horizontalization of upper instrumented vertebra (UIV) is supposed to promote shoulder balance. In other words, better correction of radiological parameters should promote clinical shoulder balance; however, this is not always observed. Purpose: Determining which of the following radiological measures correlate significantly with postoperative clinical shoulder balance: T1 tilt, UIV tilt, clavicle rib intersection angle, and degree of proximal thoracic curve correction. Study Design: Retrospective clinical case cohort study. Patients and Methods: The study included 20 patients of AIS operated for correction by pedicle screw instrumentation. There were 13 females and 7 males. The mean age at the time of surgery was 14±2.4 years with a range from 11 to 18 years. Mean preoperative Cobb angle of the major curve was 76.1±21.7° corrected to a mean postoperative Cobb 28.2±14.2°. Correction percentage of the major curve was 63.1±14.2%. The data obtained from high resolution back view photographs (to assess clinical shoulder balance) and whole spine X-ray films taken within the first year of follow-up period (to assess radiological measures related to shoulder balance) were retrospectively evaluated. Outcome measures: clinical shoulder balance was correlated with 4 radiological parameters, namely, proximal thoracic curve correction percentage, T1 tilt, UIV tilt, and clavicle-rib intersection angle. Measurements were done by Surgimap software version 2.2.12 (Nemaris, Inc.,US, https://www.surgimap.com). Results: A weak positive correlation was found between postoperative shoulder balance and UIV tilt (r)=0.242, P=0.305, and a very weak negative correlation was found between postoperative shoulder balance and proximal thoracic curve correction percentage (r)=-0.027, P=0.910. A moderate positive correlation but statistically nonsignificant was found between postoperative shoulder balance and T1 tilt (r)=0.440, P=0.052, and a statistically significant positive correlation was found between shoulder balance and clavicle rib intersection angle (r)=0.567, P=0.009. Conclusion: Horizontal UIV combined with proper correction of the main and proximal thoracic curves does not necessarily promote clinical shoulder balance. However, a moderate positive correlation exists between T1 tilt and shoulder balance, and a significant positive correlation exists between clavicle rib intersection angle and clinical shoulder balance. How to control those parameters remains unclear. (2018ESJ126)

Keywords

• shoulder balance
• AIS scoliosis
• spinal instrumentation
• pedicle screw fixation