In Scheuermann’s kyphosis, a proximal UIV and postop kyphosis value close to patients’ PI decreases the risk of PJK

Purpose Prevalence of proximal junctional kyphosis (PJK) in Scheuermann’s kyphosis (SK) varies between 24 and 40%. Multiple factors have been implicated, including kyphosis overcorrection, failure to include proximal end vertebra, and implant choice. This study aimed to determine the goal correction parameters based upon patients' pelvic incidence, and UIV to decrease PJK in Scheuermann's kyphosis. Methods X-ray and chart review of SK patients operated with all pedicle screw (PS), hybrid fixation (HF), and anterior/posterior fusions with hybrid fixation (AP). T1/T2 were grouped together as proximal fusion groups compared to T3 and distal groups. Results 96 total patients: PS ( n = 41), HF ( n = 24), and AP ( n = 31). Overall, at early postop 12 (12.5%) patients had PJK. At final follow-up, 33 (34.4%) had PJK. There was no significant difference between groups at early postop ( p = 0.86) or final follow-up ( p = 0.67). When correcting kyphosis–PI to > − 10.0° and UIV was chosen to be T1 or T2, PJK developed in 6.1% of patients at final follow-up; when fusing to T1/T2 but with kyphosis–PI < − 10.0°, 38.9% of patients developed PJK. With kyphosis–PI > − 10.0° and UIV at T3 or below, 37.0% of patients developed PJK at final follow-up. When fusing to T3 or below but failing to correct kyphosis–PI to > − 10.0°, 77.8% of patients developed PJK. Conclusion Selecting proximal UIV and avoiding kyphosis–PI mismatch can significantly decrease the prevalence of PJK rather than surgical technique or implant choice. Surgeons treating SK should, therefore, aim to correct kyphosis closer to the patient's pelvic incidence and choose T2/T1 as UIV.