Hong Joo MoonKeith H. BridwellAlekos A. TheologisMicheal P. KellyThamrong LertudomphonwanitLawrence G. LenkeMunish C. GuptaRamathibodi HospitalKorea University College of MedicineColumbia University Irving Medical CenterUniversity of California, San FranciscoWashington University in St. Louis2022-08-042022-08-042021-01-01Neurosurgery. Vol.88, No.1 (2021), 55-62152440400148396X2-s2.0-85098531717https://repository.li.mahidol.ac.th/handle/20.500.14594/78867BACKGROUND: Novel radiographic sagittal parameters of the thoracolumbar junction orientation (TLJO, thoracolumbar slope [TLS] and thoracolumbar tilt [TLT]) have been introduced and correlated with lumbopelvic parameters and thoracic kyphosis. OBJECTIVE: To determine a predictive model for reciprocal thoracic kyphosis and proximal junctional kyphosis (PJK) based on the TLJO. METHODS: A total of 127 patients who had fusion from sacrum to T10-L2 from 2004 to 2014 were reviewed. TK (T5-T12), PI, SS, PT, LL, and proximal junctional angle (PJA) were measured preoperatively, 6 wk postoperatively, and at final follow-up. TLJO was measured by TLS and TLT. Changes between time points were determined (preop-6 wk = ΔParameterPre6wk and preop-final follow/up = ΔParameterPreFinal). Scoliosis Research Society (SRS) and Oswestry Disability Index (ODI) questionnaires were evaluated at final follow-up. Patients were divided into 2 groups based on the presence of PJK (ΔPJAPreFinal >15◦). Independent t-tests and receiver operating characteristic (ROC) curves were used to investigate the significance of differences and cut-off values. Pearson correlations and linear regressions were used to analyze the entire cohort to determine the relationship between the changes in parameters. RESULTS: Compared to patients without PJK (n = 100), those with PJK (n = 27) had significantly lower SRS scores and significantly greater ΔTKPreFinal, ΔLLPre6wk, and ΔTLSPre6wk. To maintain in the nonPJK group, ROC curves demonstrated a cut-off value of −9.4◦ for ΔTLSPre6wk. PJK was significantly correlated with ΔTKPreFinal and ΔTLSPre6wk. The linear correlation revealed that ΔTLSPre6wk < −25.3◦ is the risk factor of PJK > 15◦. CONCLUSION: As change of TLS reflects lumbopelvic realignment and influences reciprocal TK, reducing the change of TLS may be a sagittal realignment guideline to reduce the risk of PJK.Mahidol UniversityMedicineArticleSCOPUS10.1093/neuros/nyaa311