Abstract
ABSTRACTBones’ shapes and structures adapt to the muscle and reaction forces they experience during everyday movements. Onset of independent walking, at approximately 12 months, represents the first postnatal exposure of the lower limbs to the large forces associated with bipedal movements; accordingly, earlier walking is associated with greater bone strength. However, associations between early life loading and joint shape have not been explored. We therefore examined associations between walking age and hip shape at age 60 to 64 years in 1423 individuals (740 women) from the MRC National Survey of Health and Development, a nationally representative British birth cohort. Walking age in months was obtained from maternal interview at age 2 years. Ten modes of variation in hip shape (HM1 to HM10), described by statistical shape models, were ascertained from DXA images. In sex‐adjusted analyses, earlier walking age was associated with higher HM1 and HM7 scores; these associations were maintained after further adjustment for height, body composition, and socioeconomic position. Earlier walking was also associated with lower HM2 scores in women only, and lower HM4 scores in men only. Taken together, this suggests that earlier walkers have proportionately larger (HM4) and flatter (HM1, HM4) femoral heads, wider (HM1, HM4, HM7) and flatter (HM1, HM7) femoral necks, a smaller neck‐shaft angle (HM1, HM4), anteversion (HM2, HM7), and early development of osteophytes (HM1). These results suggest that age at onset of walking in infancy is associated with variations in hip shape in older age. Early walkers have a larger femoral head and neck and smaller neck‐shaft angle; these features are associated with reduced hip fracture risk, but also represent an osteoarthritic‐like phenotype. Unlike results of previous studies of walking age and bone mass, associations in this study were not affected by adjustment for lean mass, suggesting that associations may relate directly to skeletal loading in early life when joint shape changes rapidly. © 2018 American Society for Bone and Mineral Research.
Highlights
Hip geometry has been shown to be associated with a number of burdensome musculoskeletal health conditions including osteoarthritis (OA) and osteoporosis
To address important gaps in the existing literature, we examined associations between age at onset of independent walking and hip shape described by Statistical shape modeling (SSM) in older men and women in a British birth cohort study: the Medical Research Council (MRC) National Survey of Health and Development (NSHD)
Early walking appears to be associated with a smaller neck-shaft angle; this could be a consequence of a longer period of loading during a critical growing phase starting from the larger angle found in early infancy.[7]. In addition to a smaller neck-shaft angle, earlier walking was associated with higher scores for HM1 corresponding to a wider, shorter femoral neck, a flattening of the femoral head, and early development of osteophytes
Summary
Hip geometry has been shown to be associated with a number of burdensome musculoskeletal health conditions including osteoarthritis (OA) and osteoporosis. Gross morphological features such as a wider femoral neck[1] and femoral head,(2) smaller neck-shaft angle,(3) and anteversion (external rotation of the femur)(4) are associated with hip OA. Evidence suggests that neckshaft angle increases during gestation, and decreases through childhood until around age 10,(7) thereafter remaining stable throughout adulthood.[8] after peaking at birth, femoral neck anteversion declines dramatically in the first 3 to 4 years,(9) thereafter declining more slowly until maturity. Given the clinical relevance of these components of hip shape and their developmental timing, it is important to identify potentially modifiable factors in childhood that may influence hip shape
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