A longitudinal comparison of appendicular bone growth and markers of strength through adolescence in a South African cohort using radiogrammetry and pQCT
To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally. Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. Weight- and non-weight-bearing bones have different growth and strength patterns.
Functional loading modulates bone size and strength.
To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally, we performed manual radiogrammetry of the second metacarpal on hand-wrist radiographs and measured peripheral quantitative computed tomography images of the radius (65%) and tibia (38% and 65%), annually on 372 black and 152 white South African participants (ages 12–20 years). We aligned participants by age from peak metacarpal length velocity. We assessed bone width (BW, mm); cortical thickness (CT, mm); medullary width (MW, mm); stress-strain index (SSI, mm3); and muscle cross-sectional area (MCSA, mm2).
From 12 to 20 years, the associations between metacarpal measures (BW, CT and SSI) and MCSA at the radius (males R2 = 0.33–0.45; females R2 = 0.12–0.20) were stronger than the tibia (males R2 = 0.01–0.11; females R2 = 0.007–0.04). In all groups, radial BW, CT and MW accrual rates were similar to those of the metacarpal, except in white females who had lower radial CT (0.04 mm/year) and greater radial MW (0.06 mm/year) accrual. In all groups, except for CT in white males, tibial BW and CT accrual rates were greater than at the metacarpal. Tibial MW (0.29–0.35 mm/year) increased significantly relative to metacarpal MW (− 0.07 to 0.06 mm/year) in males only. In all groups, except white females, SSI increased in each bone.
Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. The local and systemic factors influencing site-specific differences require further investigation.
KeywordsFunctional loading Growth patterns Muscle pQCT Radiogrammetry Stress-strain index
The contribution of the Bone Health staff, participants and caregivers is gratefully acknowledged. The authors thank Dr. Simon Schoenbuchner for assisting with the preparation of the pQCT data.
The Bone Health Cohort was supported financially by the Wellcome Trust (UK) and the South African Medical Research Council. JMP received funding from the National Research Foundation.
Compliance with ethical standards
Conflicts of interest
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