In the past decades, a deeper understanding of the biomechanical underpinnings of adult spinal deformity (ASD) surgery has been gained, with an increased focus on global sagittal alignment. Still, the development of proximal junctional kyphosis (PJK) or even proximal junctional failure after correction remain a relatively frequent and clinically relevant occurrence, and represent major drivers of reoperations and morbidity. 1 Lee et al. 2 approach the problem of PJK by aiming at reliably predicting its risk. With this, they aim to promote enhanced patient counseling and risk-benefit management, but also allow for refined therapeutic approaches -corrections could in theory be "personalized" to every single patient, even more so than they are anyways already, by considering personalized risk profiles. Moreover, specifically for PJK, postoperative patient-specific evaluations of the correction could identify those who may benefit from early revision surgery. The authors apply data from a large multi-institutional database from 16 Korean centers, strengthening the potential generalizability of their approach. In total, 201 patients with a minimum follow-up of 1 year were included, of which 49 (24.4%) experienced PJK -which was defined as a proximal junctional angle (PJA) of 20° or greater, or as an increase in PJA of 10° or greater. All patients were then randomly split into train and test sets, hyperparameters were tuned via a cross-validation approach, and a range of machine learning (ML) techniques applied. Input parameters of the final model, which was based on the random forest algorithm, include age and body mass index (BMI), deformity etiology (idiopathic, degenerative, neuromuscular, etc.), curve type, and pelvic as well as global parameters. In addi-
Neurospine