Prediction of postoperative proximal junctional kyphosis/failure in adult degenerative scoliosis via magnetic resonance imaging-based vertebral bone quality, computed tomography-based Hounsfield units, and sagittal vertical axis

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are common complications after scoliosis surgery. They often necessitate revision surgery, adversely affecting the patient's quality of life and incurring additional medical costs. Studies have found that osteoporosis and sagittal spinal parameters are risk factors for PJK/PJF. This study aimed to investigate the utility of a risk assessment model consisting of imaging features for predicting PJK and PJF (PJK/PJF) after correction for adult degenerative scoliosis (ADS). This retrospective case-control study of 164 patients with ADS treated at our institution from 2014 to 2023 assessed PJK/PJF and spinal parameters via X-ray. Vertebral bone quality (VBQ) scores and Hounsfield unit (HU) values from preoperative magnetic resonance imaging (MRI) and computed tomography scans were measured to evaluate bone quality. Subsequently, a multivariate logistic regression analysis was conducted to identify potential risk factors associated with PJK/PJF. A total of 164 patients (mean age 68 years) were included in the study, and 26 (15.9%) developed PJK. In the multivariate logistic regression model for predicting PJK/PJF, VBQ score odds ratio (OR) =14.758; 95% confidence interval (CI): 2.716-80.191; P=0.002 and HU value (OR =0.981; 95% CI: 0.967-0.995; P=0.009) were strongly associated with the outcome. The final model also included preoperative sagittal vertical axis (SVA) (OR =1.023; 95% CI: 0.995-1.052; P=0.114) and postoperative SVA (OR =1.027; 95% CI: 0.993-1.061; P=0.117). The area under the receiver operating characteristic curve for the novel risk assessment model was 0.876. The combination of VBQ, HU values, and SVA can more accurately predict the occurrence of PJK/PJF after ADS surgery as compared to using VBQ or HU alone.