• Takahiro Kitagawa, Satoshi Suzuki, Kazuki Takeda, Toshiki Okubo, Masahiro Ozaki, Yohei Takahashi, Osahiko Tsuji, Narihito Nagoshi, Mitsuru Yagi, Morio Matsumoto, Masaya Nakamura, and Kota Watanabe.
• Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan.
• Spine. 2024 Jul 30.

Study DesignRetrospective comparative study.ObjectiveTo evaluate the relationship between pelvic incidence (PI) and proximal junctional kyphosis (PJK) in patients with Lenke type 5 adolescent idiopathic scoliosis (AIS).Summary Of Background DataAlthough PJK is a common complication of sagittal malalignment after posterior correction and fusion surgery (PSF), few studies have assessed its risk factors. The significance of pelvic morphology in relation to PJK has been suggested but remains unclear in Lenke type 5 AIS patients.MethodsA total of 92 patients with Lenke type 5 AIS who underwent selective thoracolumbar PSF with a minimum follow-up of two years were included. Patients were divided into PJK and non-PJK groups based on postoperative radiographs. The influence of PI on PJK occurrence was evaluated through binary logistic analysis. Subgroup analysis was performed based on the PI value (low PI,<45°; high PI, ≥ 45°) to identify factors affecting PJK occurrence.ResultsPJK was observed in 17.4% of the whole cohort. Binary logistic regression analysis identified low PI and large TL/L curve as a risk factor for PJK (PI, odds ratio, 0.933; TL/L curve, odds ratio, 1.080). Subgroup analysis showed that the postoperative increase in the upper instrumented vertebra slope in PJK cases was comparable in both the low and high PI groups. Meanwhile, lordotic changes in the fused area in the PJK cases were observed only in the low PI group. No difference in the Scoliosis Research Society 22 scores were observed between the two groups.ConclusionFrom this study a low PI was identified as a risk factor for the occurrence of PJK in Lenke type 5 AIS patients. The occurrence of PJK is influenced by lordotic changes in the fused area and the limited compensatory capacity of the pelvis in patients with a low PI.Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.

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