Methods: Skeletal material from a 35 year old female was acquired from the University of Malawi College of Medicine. Midshaft femur ground sections were prepared, imaged, and analyzed using formal techniques for both lamellar periodicity and variability in widths for bone formed during ca. 1983. Trace element analyses were performed by laser ablation inductively coupled plasma mass spectrometry using a New Wave Research UP-213 (wavelength 213 nm) laser system combined with an Agilent 7500ce ICP quadrupole mass spectrometer. Element concentrations were calculated with the software “GLITTER” for the following: copper, zinc, barium, and strontium normalized to calcium. Detection limits (99% confidence) were typically in the range of 0.01 and 0.03 ppm.
Results: Growth rate variability with near-weekly resolution was obtained for primary lamellar deposited during approximately 1.5 years. We observe a moderately long term growth rhythms provisionally corresponding to ca. 8 weeks duration. Variations of concentrations of barium, strontium, copper, and zinc along the course of these primary lamellae were quantified and rhythms were found that appear to correspond to lamellar growth rate variability.
Conclusions: We observe long periodic growth rate variability in human bone that is comparable to variation seen in fluctuations of trace elements. The metabolic flux of materials is sensitive to growth rate.