Adult spinal deformity and its relationship with hip range of motion: a cohort study of community-dwelling females.

BACKGROUND CONTEXT: Adult spinal deformity affects lower extremity alignment with compensation in joint range of motion (ROM) and alignment of the hip.

PURPOSE: To investigate the relationship between sagittal spinopelvic alignment and the ROM of the hip joint and the femoral oblique angle (FOA).

STUDY DESIGN: Cross-sectional, observational cohort study of community-dwelling Japanese women.

METHODS: The study group included 158 women, enrolled in our ongoing prospective cohort study, with upright spine radiographs and physical measurements obtained for all participants. Radiographic spinopelvic parameters included measurement of thoracic kyphosis, lumbar lordosis (LL), sagittal vertical axis (SVA), sacral slope, pelvic incidence, and pelvic tilt (PT). FOA parameters were measured on hip radiographs and hip ROM included external and internal rotation and extension. The association between spinopelvic parameters, the FOA, and hip joint ROM was evaluated using Spearman's correlation analysis.

RESULTS: External rotation of the hip was correlated with LL (R=0.179, p=.024), PT (R=-0.273, p=.001) and SVA (R=-0.215, p=.007), with the FOA being correlated with the SVA (R=0.502, p<.001).

CONCLUSIONS: The decrease in hip external rotation with adult spinal deformity might reflect a structural modification in spinopelvic alignment. An increase in FOA was associated with an increase in SVA, indicative of a sagittal malalignment in the decompensated phase of adult spinal deformity.