Shoulder balance in patients with Lenke type 1 and 2 idiopathic scoliosis appears satisfactory at 2 years following anterior vertebral body tethering of the spine

Background Shoulder balance is an important factor for patient satisfaction following surgery for idiopathic scoliosis (IS). There is no literature reporting the effect of anterior vertebral body tethering (AVBT) on shoulder balance. The purpose of this study was to report the prevalence of postoperative shoulder imbalance in patients undergoing AVBT for IS. Methods In this retrospective case series, patients enrolled in a multicenter scoliosis registry who underwent AVBT from 2013 to 2017 in two Canadian centers were identified. The primary outcome was shoulder imbalance, defined as an absolute radiographic shoulder height of > 2 cm, at 2 years postoperatively (follow-up range: 22-30 months). Clavicular angle and T1 tilt angle were also investigated. Results Of the 50 patients identified (92% female; preoperative age: 11.9 +/- 1.4 years), there were 43 (86%) patients with Lenke 1 and 7 (14%) patients with Lenke 2 curves. The mean Cobb angles of the proximal thoracic and main thoracic curves were 22.8 degrees +/- 8.8 degrees and 49.4 degrees +/- 8.5 degrees preoperatively and 13.1 degrees +/- 7.5 degrees and 24.9 degrees +/- 9.5 degrees at a mean follow-up time of 2.1 years. Absolute clavicular angle and T1 tilt angle were 2.8 degrees +/- 2.2 degrees and 4.8 degrees +/- 3.5 degrees preoperatively and 2.2 degrees +/- 1.7 degrees and 4.7 degrees +/- 4.2 degrees at 2-year follow-up. Preoperatively, absolute shoulder height averaged 15.6 +/- 10.4 mm, and 15 (30%) patients had shoulder imbalance. At 2-year follow-up, absolute shoulder height averaged 11.2 +/- 8.3 mm, and 8 (16%) patients had shoulder imbalance. Of the patients who had acceptable shoulder balance preoperatively, 4 (11.4%) became imbalanced at 2 years postoperatively. Conclusion Postoperative shoulder imbalance in this early group of patients with IS undergoing AVBT was seen in 16% of patients, a reduction from 30% preoperatively. These results likely reflect the potential of the proximal thoracic curve to correct spontaneously following AVBT.