Sinister! The high pre-op left shoulder is less likely to be radiographically balanced at 2 years post-op.

Abstract

AIS patients consider shoulder balance an important cosmetic outcome after surgery. We examined the impact of preoperative left shoulder elevation (LSE) and choice of upper instrumented vertebra (UIV) on postoperative shoulder imbalance (PostSI). This was a retrospective cohort study utilizing a prospective AIS database. Patients had Lenke type 1-4 curves and preoperative shoulder height ≥ 1.0cm. Patients with preoperative LSE and right shoulder elevation (RSE) were compared. Shoulder height difference < 1cm was considered 'mild', 1-2cm was 'moderate', and ≥ 2.0cm was 'severe'. 407 patients had ≥ 1.0cm imbalance preoperatively, with 88 (21.6%) LSE. There were no differences in gender (p = 0.855) or age (p = 0.477). Patients with LSE more frequently had Lenke type 2 curves (43.2% vs 16.3%, p < 0.001), while preoperative RSE averaged 1.9 ± 0.9cm versus 1.6 ± 0.5cm for LSE (p < 0.001). Those with LSE more often had severe PostSI at 2years (30.7% vs 5.0%, p < 0.001), and only 26.1% of patients with severe preoperative LSE corrected to mild. In contrast, most patients with RSE had mild PostSI regardless of initial imbalance. When examining only LSE patients, there was no difference in preoperative SH by final UIV (p = 0.101). Further, UIV choice did not impact the proportion of severely unbalanced patients postoperatively (p = 0.446). A PTC > 34.5° was predictive of PostSI ≥ 2.0cm for patients with preoperative LSE. AIS patients with preoperative LSE are less likely to achieve level shoulders postoperatively. Choice of higher UIV did not affect postoperative shoulder imbalance in this cohort. A PTC > 34.5° was predictive of severe PostSI in patients with preoperative LSE. II.