Proximal Junctional Kyphosis in Lenke 5 AIS Patients: The Important Factor of Pelvic Incidence

Abstract BackgroundThe purpose of the study was to investigate whether pelvic incidence (PI) will affect the occurrence of PJK in Lenke 5 AIS patients after correction surgery and try to explore a better surgical scheme based on PI.MethodsLenke 5C AIS patients that underwent correction surgery for thoracolumbar/lumbar (TL/L) curves with a minimum of a 2-year follow-up were identified. Demographic and radiographic data were collected preoperatively, postoperatively, and at the final follow-up. The comparison between the PJK and the Non-PJK group was conducted and the subgroup analysis was performed based on the preoperative value of PI to investigate the potential mechanism of PJK. ResultsThe mean preoperative Cobb angle of the TL/L curve was 53.4°±8.6. At the final follow-up, the mean TL/L Cobb angle was drastically decreased to 7.3°±6.8 (P <0.001). The incidence of PJK was 21.9% (7/32) in the low PI group (PI<45°) and 15.8% (6/38) in the high PI group (PI≥45°), and there was no statistical difference between the two groups (2=0.425, P > 0.05). The UIV of the PJK subgroup was much closer to the cranial level than the Non-PJK subgroup for the high PI group (PJK vs. Non-PJK: 6.0±1.3 vs. 8.6±1.6, P = 0.003). There was no significant difference in the selection of LIV between the two groups.ConclusionsThe incidence of PJK in Lenke 5 AIS was 18.6%. Our results found no difference in the incidence of PJK according to PI, but the mechanisms of PJK may be different for different PI values. The design of surgical plans for Lenke 5 AIS patients should take individual PI into account to decrease the incidence of PJK.