Does lumbar lordosis minus thoracic kyphosis predict the clinical outcome of patients with adult degenerative scoliosis?

Purpose To evaluate the predictive effect of lumbar lordosis minus thoracic kyphosis (LL-TK) in the surgical outcome of adult degenerative scoliosis (ADS) patients and explore the optimum target base on it. Methods The preoperative and postoperative data including radiographic image and functional evaluation (Visual Analog Scale, VAS; Oswestry Disability Index, ODI; Japanese Orthopaedic Association, JOA) of 130 patients with ADS who underwent corrective surgery was retrospectively reviewed. The relationship between sagittal parameters and surgical outcome was assessed by using the Pearson correlation analysis. Receiver operating characteristic (ROC) curve was used to define the optimum cutoff value of LL-TK. Patients were divided into two groups based on LL-TK to compare the preoperative and postoperative status. Results LL-TK assessed soon after surgery strongly correlated with health-related quality of life (HRQOL) and sagittal vertical axis (SVA) at last follow-up. The cutoff value of LL-TK was set at 10 degrees to determine a good clinical outcome (ODI < 20) and sagittal balance (SVA < 50 mm). Patients with LL-TK > 10 degrees presented significantly better postoperative VAS, ODI, JOA, and SVA than patients with LL-TK < 10 degrees. Conclusion LL-TK could effectively predict postoperative HRQOL and sagittal balance for patients with ADS. Patients with LL-TK > 10 degrees showed a better clinical outcome and sagittal balance, so LL-TK > 10 degrees could be the optimum corrective target for these patients.