Analysis of surgical outcomes and complications following SRS-Schwab grade 6 osteotomy in angular hyperkyphotic deformity: 90 cases with a minimum 2-year follow-up. - Zhang J; Ni J; Zeng Y; Li W (European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2026)