71. High preoperative T1 slope is a marker for global sagittal malalignment

Abstract

BACKGROUND CONTEXT T1 slope (T1S) is a parameter typically discussed in the context of cervical deformity and is correlated with health-related quality of life outcomes. Although prior research has suggested that T1S is related to global alignment, a definition for “high” T1S has not been established. Most patients undergoing cervical surgery do not receive full spine imaging. Therefore, it would be beneficial to have a parameter obtained from cervical radiographs that is associated with thoracolumbar malalignment. PURPOSE To define a threshold for T1S that is associated with thoracolumbar malalignment STUDY DESIGN/SETTING Retrospective review of a prospective adult spinal deformity(ASD) database PATIENT SAMPLE A total of 226 preoperative ASD patients. OUTCOME MEASURES Baseline sagittal alignment: T1S, thoracic kyphosis(TK), C7 sagittal vertical axis (SVA), T1 pelvic angle (TPA), pelvic tilt (PT), pelvic incidence-lumbar lordosis mismatch (PI-LL). METHODS A database of preoperative ASD patients was analyzed. Patients without preoperative full-spine images were excluded. Measures obtained from standing lateral radiographs included: T1S, TK, SVA, TPA, PT, and PI-LL. T1S was correlated to each of these parameters. Decision tree analysis was then used to determine the T1S corresponding to published thresholds for high TK (40°), SVA (40mm), TPA (25°), and PT (25°). Alignment between high and normal T1S patients was compared via t-tests and chi-square tests. RESULTS A total of 226 preoperative ASD patients were included (mean 58±16y 62% F). At baseline, 30% had high TK, 54% had high SVA, 46% had high TPA, and 46% had high PT. Larger T1S was significantly correlated with greater SVA (R=.365) TPA (R=.302), TK (R=.606), and PT (R=.230)(all p 30° had higher TK (41.5° vs 25.8°), SVA (78.7mm vs 33.7mm), TPA (27.6° vs 18.3°), and PT (26.3° vs 20.8°), and PI-LL (18.2° vs 11.7°)(all p 25° (T1S 20° (T1S CONCLUSIONS Similar to previous studies higher T1S was associated with worse global alignment. T1S was most strongly associated with TK. A T1S=30° corresponds to thresholds for high TK, SVA, TPA, and PT. Therefore, surgeons should consider obtaining full-spine radiographs if a T1S>30° is present on cervical imaging. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.