Who's afraid of the big bad Wolff?: “Wolff's law” and bone functional adaptation

TLDR

Wolff’s law has been misrepresented and its strict mathematical formulation discredited, but the broader concept of bone functional adaptation to mechanical loading is well supported, though strain–structure correspondence varies by skeletal location and mechanical environment, limiting inference to comparable regions and species. Recent controlled studies show that objections to bone functional adaptation have been largely resolved, adult bone morphology is less strain‑responsive yet not solely shaped by juvenile loads, genetic factors influence but loading variations are equally or more critical, and traditional geometric parameters remain the best estimates for reconstructing in‑vivo mechanical competence and behavioral differences when applied cautiously. Published in Am J Phys Anthropol, 2006 (© 2006 Wiley‑Liss, Inc.).

Abstract

Abstract “Wolff's law” is a concept that has sometimes been misrepresented, and frequently misunderstood, in the anthropological literature. Although it was originally formulated in a strict mathematical sense that has since been discredited, the more general concept of “bone functional adaptation” to mechanical loading (a designation that should probably replace “Wolff's law”) is supported by much experimental and observational data. Objections raised to earlier studies of bone functional adaptation have largely been addressed by more recent and better‐controlled studies. While the bone morphological response to mechanical strains is reduced in adults relative to juveniles, claims that adult morphology reflects only juvenile loadings are greatly exaggerated. Similarly, while there are important genetic influences on bone development and on the nature of bone's response to mechanical loading, variations in loadings themselves are equally if not more important in determining variations in morphology, especially in comparisons between closely related individuals or species. The correspondence between bone strain patterns and bone structure is variable, depending on skeletal location and the general mechanical environment (e.g., distal vs. proximal limb elements, cursorial vs. noncursorial animals), so that mechanical/behavioral inferences based on structure alone should be limited to corresponding skeletal regions and animals with similar basic mechanical designs. Within such comparisons, traditional geometric parameters (such as second moments of area and section moduli) still give the best available estimates of in vivo mechanical competence. Thus, when employed with appropriate caution, these features may be used to reconstruct mechanical loadings and behavioral differences within and between past populations. Am J Phys Anthropol, 2006. © 2006 Wiley‐Liss, Inc.