Selective thoracic fusion of a left decompensated main thoracic curve: proceed with caution?

Purpose: Previous research has shown that with certain idiopathic scoliosis curve types, performing a selective thoracic fusion (STF) is associated with an increased risk of coronal decompensation post-operatively. The purpose of the current study was to determine the influence of curve correction and fusion level on post-operative balance in STF for adolescent idiopathic scoliosis patients with pre-operative coronal decompensation. Methods: A multicenter database was queried for subjects with right Lenke 1–4C curves, pre-operative left coronal imbalance, and 2-year follow-up who underwent STF (caudal fusion level of L1 or proximal). Rates of decompensation were compared between groups with different levels of fusion. Thoracic and lumbar curve correction as well as Scoliosis Research Society-22 outcome scores were compared between groups that were post-operatively balanced or persistently decompensated. Results: 121 patients were identified with average thoracic and lumbar curves of 53° and 41°. Mean pre- and post-operative decompensations were 2.4 ± 1.0 and 1.8 ± 1.1 cm, respectively. Eighteen patients were fused short, 62 to, and 41 were fused past the stable vertebra. Ten patients were fused short, 32 to, and 78 were fused past the neutral vertebra. Incidence of post-operative decompensation was 41%. No differences in post-operative decompensation relative to the stable or neutral vertebra were noted (p = 0.66, p = 0.74). Post-operatively, those patients who were balanced had similar thoracic curve correction (58%) to those decompensated (54%, p = 0.11); however, patients balanced post-operatively had greater SLCC (45 vs 40%, p = 0.04). No differences in SRS-22 outcome scores were noted between groups (p > 0.05). Conclusions: There was a high rate of post-operative decompensation in patients with pre-operative coronal decompensation undergoing STF. Fusion to or past the stable or neutral vertebra did not affect the risk of persistent decompensation. Attempts to improve SLCC could reduce post-operative decompensation.