• Hong Joo Moon, Keith H Bridwell, Alekos A Theologis, Micheal P Kelly, Thamrong Lertudomphonwanit, Lawrence G Lenke, and Munish C Gupta.
• Department of Neurosurgery, Korea University College of Medicine, Seoul, South Korea.
• Neurosurgery. 2020 Dec 15; 88 (1): 55-62.

BackgroundNovel 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.ObjectiveTo determine a predictive model for reciprocal thoracic kyphosis and proximal junctional kyphosis (PJK) based on the TLJO.MethodsA 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.ResultsCompared 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°.ConclusionAs 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.Copyright © 2020 by the Congress of Neurological Surgeons.

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