Classification of arm swing as a clinical marker of advancing spinal deformity among community-dwelling female volunteers 60 years or older

The clinical characteristics of adult spinal deformity (ASD) include worsening of deformity during gait, which leads to unstable posture and propensity to fall. The purpose of this study was to classify arm swing and to analyse its clinical implications. Clinical and radiographic evaluations were performed with 168 community-dwelling female volunteers recruited from a population register in Hokkaido, Japan, with a mean age of 67.3 ± 4.7 years, and arm swing was classified into four groups according to maximum forward and backward arm swing distance: (1) predominantly forward swing with forward swing always larger than backward swing (FS, n = 138), (2) equal or equivocal swing (ES, n = 8), (3) predominantly backward swing with backward swing always larger than forward swing (BS, n = 20), and (4) thigh-hand type without arm swing with their hands placed on thighs (TH, n = 2). BS and FS showed significant differences in radiographic lumbar lordosis (BS 19.4 ± 18.1° vs. FS 40.6 ± 14.5°, P < 0.01 ANOVA), pelvic tilt (BS 40.0 ± 7.3° vs. FS 22.9 ± 8.9°, p < 0.01), number of vertebral fractures (BS 1.2 ± 1.4 vs. FS 0.3 ± 0.6, p < 0.01), and trunk extensor muscle strength (BS 374.9 ± 134.8 N vs. FS 478.1 ± 172.6 N, p < 0.05). Arm swing correlated with severity of radiographic ASD, osteoporotic changes, and back muscle weakness. The number of ASD patients, which includes patients with de novo/idiopathic scoliosis, degenerative/osteoporotic kyphosis, and other neuromuscular deformities, has been increasing, and further study should clarify the importance of dynamic evaluation of ASD among elderly patients.