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. INTRODUCTION: Functional loading modulates bone size and strength. METHODS: 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). RESULTS: 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. CONCLUSION: 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. Graphical abstract.

Observations on the pollical palmar interosseous muscle (of Henle).

Questions about the existence of a "pollical" (first) volar interosseous muscle have persisted since its description by Henle in 1858. A survey of current human anatomy texts and atlases reveals that the majority do not recognize a pollical volar interosseous muscle and therefore they identify only three palmar interossei. We examined the thumbs of 20 individuals of African and European origin in the human anatomy lab at University of the Witwatersrand (Johannesburg) and 15 individuals of European ancestry in the anatomy lab at the University at Stony Brook (New York). A pollical palmar interosseous muscle (PPIM) was found in 86% of individuals (17/20 of the Witwatersrand sample; 13/15 of the Stony Brook sample). Here, we offer a definition of the PPIM in an attempt to resolve the long-standing question of its existence and its relationship to the adductor pollicis obliquus and the deep head of flexor pollicis brevis. We suggest that the human hand usually possesses four palmar interossei as well as four dorsal interossei.