The Spontaneous Development of Cosmetic Shoulder Balance and Shorter Segment Fusion in Adolescent Idiopathic Scoliosis With Lenke I Curve: A Consecutive Study Followed Up for 2 to 5 Years.

STUDY DESIGN A single-center, retrospective, consecutive case series. OBJECTIVE To evaluate the spontaneous development of cosmetic shoulder balance (SDCSB) after surgery and to investigate the feasibility of shorter segment fusion in adolescent idiopathic scoliosis (AIS) with Lenke I curve. SUMMARY OF BACKGROUND DATA Upper instrumented vertebrae (UIV) at a more proximal level are always chosen to keep postoperative shoulder balance in AIS. In the guidelines of Rose and Lenke proposed in 2007, for Lenke I right thoracic curves, UIV should be T4 or T5 when the right shoulder is elevated preoperatively, T4 or T3 if the shoulders are level, and T2 when the left shoulder is elevated. Cosmetic shoulder balance (CSB), however, corrects and improves itself postoperatively. METHODS Seventy-five consecutive AIS patients with Lenke I curves were followed up for 2 to 5 years postoperatively. Twenty patients (26.7%) selected UIV at the caudal levels in the guidelines of Rose and Lenke (T5 when patients were with right shoulder elevated preoperatively, T4 when patients were with even shoulders preoperatively). Forty-two patients (56.0%) selected UIV at more caudal levels than those suggested by the guidelines. In this study, UIV at the caudal levels in the guidelines and UIV at more caudal levels than those suggested by the guidelines were shorter segment fusion. CSB was measured from photographs. Spinal Appearance Questionnaire (SAQ) was acquired for subjective evaluation of shoulder balance. RESULTS At last follow-up, the main thoracic curve was 19.5° ± 10.4°, the coronal balance improved to 0.7 ± 0.6 cm, and T2-T12 kyphosis was 34.4° ± 10.8°. At preoperation, immediate postoperation, and last follow-up, the measurements of CSB were 1.1 ± 0.7 cm (range: -2.4 to 1.7 cm), 0.9 ± 0.6 cm (range: -0.8 to 3.1 cm), and 0.6 ± 0.4 cm (range: -0.6 to 1.5 cm). At the three time points, numbers of patients with -1.0 cm < CSB < 1.0 cm were 28 (37.3%), 46 (61.3%), and 70 (93.3%), respectively. There was significant difference between the measurements of CSB at immediate postoperation and at last follow-up (t = 3.6, P < 0.001). At last follow-up, 74 (98.7%) patients perceived even shoulders in SAQ. CONCLUSION SDCSB plays an important role in regaining shoulder balance after surgery in AIS. The shorter segment fusion is feasible in treating AIS patients with Lenke I curves. LEVEL OF EVIDENCE 4.