The risks and predictive factors of proximal junctional kyphosis in Lenke type 5 adolescent idiopathic scoliosis correction patients

Objective Proximal junctional kyphosis (PJK) is a common sagittal complication of adolescent idiopathic scoliosis (AIS) following corrective surgery, leading to new deformities, pain, and even revision surgery. This study aimed to investigate the risk and predictive factors for PJK in Lenke type 5 AIS patients after correction, and identify parameters relevant to intraoperative guidance. Methods Thirty-five patients with Lenke type 5 AIS who underwent corrective surgery at our hospital between January 2008 and February 2016 were divided into the PJK (n = 15) and non-PJK (n = 20) groups. Correlation and receiver operating characteristic (ROC) curve analyses were performed to screen significant parameters and calculate their thresholds. Survival analysis was performed to examine differences between the groups. Results Independent t tests revealed significant differences between groups in the preoperative pelvic incidence, preoperative pelvic tilt, postoperative proximal junctional angle (PJA), and postoperative thoracic kyphosis (TK). The postoperative PJA, postoperative TK, and other parameters correlated significantly with changes in the PJA at final follow-up. ROC curves revealed that the postoperative PJA and postoperative TK effectively predicted the occurrence of PJK, with thresholds of 9.45° and 25.25°, respectively. The estimated survival times were 14.7 months for PJA > 9.45° and TK > 25.25°, 19.2 months for PJA > 9.45°, and 33.9 months for TK > 25.25°. Conclusions This study showed that the postoperative PJA and postoperative TK can be used to effectively predict the occurrence of PJK in Lenke type 5 AIS patients following corrective surgery, with thresholds of 9.45° and 25.25°, respectively.