Dispelling the Dogma: upper-instrumented vertebrae of T5–T6 can achieve similar correction and shoulder balance with less blood loss than T2–T4 in select patients

The choice of upper-instrumented vertebrae (UIV) for posterior spinal fusion (PSF) constructs is influenced by guidelines where UIV is T4 or more cephalad. In a cohort of patients with adolescent idiopathic scoliosis (AIS) with thoracic curves, we sought to (a) compare postoperative shoulder balance for patients with UIV of T5-T6 versus T2-T4 and (b) evaluate curve and operative characteristics that lead to balance with a more caudal UIV. A single-institution AIS registry was queried for patients undergoing PSF from 2000 to 2017. Included were patients undergoing PSF for AIS, with Lenke 1 and 2 curves, and minimum 2-year follow-up. Shoulder balance was defined as: T1 tilt = 0 ± 5°, coracoid height difference (CHD) = 0 ± 1 cm. A total of 161 patients were included, mean follow-up was 47 months. Curves fused to T2-T4 had larger, stiffer preoperative proximal thoracic curves and were more likely to be classified as Lenke 2. Following PSF, there was no difference in final T1 tilt ( P = 0.062) or final CHD ( P = 0.176) between groups. Patients with a UIV of T5-T6 had shorter operative times ( P < 0.001), less operative blood loss ( P = 0.009), and similar complication rates ( P = 0.344). In the T5-T6 cohort, 70.3% of patients achieved shoulder balance at the final follow-up. For thoracic AIS undergoing PSF, selecting a UIV of T5 or T6 can result in comparable postoperative shoulder balance in properly selected patients.