Abstract
INTRODUCTION: Some adult patients with spinal deformities show a sloping spine, not kyphosis, with severe global malalignment and deterioration of patient-reported outcome measures (PROMs). The purpose of this study was to elucidate sloping-type deformities on the basis of radiographic parameters and PROMs. METHODS: This study included participants from a health screening program with sagittal vertical axis (SVA) >40 mm. The sloping-type deformity (S group) was defined as the deformity in which all posterior vertebral walls were positioned anteriorly to the vertical line extending from the posterior end of the sacrum on standing whole-spine lateral radiographs. SVA, thoracic kyphosis (TK), lumbar lordosis (LL), L4-S angle, pelvic incidence (PI), and pelvic tilt (PT) were measured. PROMs were evaluated using the Oswestry Disability Index (ODI). RESULTS: A total of 348 participants (142 men and 206 women; average age 75.8 years) were included in the study, and 50 participants (14.4%) were classified into the S group. The mean age and measured variables of the S and non-sloping-type (non-S) group were 76.1, 72.6 years; SVA 111, 79 mm; TK 24, 35°; L4-S 15, 30°; PI 58, 49°; PT 27, 21°; PI-LL 28, 14°; and ODI 22, 15%, respectively. There were 30 participants (60%) with evident lumbar anterolisthesis in the S group and 76 (25.5%) in the non-S group (p<0.001). The S group had larger SVA, PI, PT, and PI-LL (all p<0.001) and lower TK and L4-S angle (both p<0.001) than did the non-S group. The S group showed an inferior ODI to that of the non-S group (p=0.012). CONCLUSIONS: The sloping-type deformity showed a significantly higher PI, and worse spinopelvic alignment and PROMs. The significant factors contributing to the incidence of sloping-type deformities were higher PI, prevalence of lumbar anteriolisthesis, and lower TK and L4-S angle.