Abstract
Trabecular bone of the human calcaneus is subjected to extreme repetitive forces during endurance running and should adapt in response to this strain. To assess possible bone functional adaptation in the posterior region of the calcaneus, we recruited forefoot-striking runners (n = 6), rearfoot-striking runners (n = 6), and non-runners (n = 6), all males aged 20–41 for this institutionally approved study. Foot strike pattern was confirmed for each runner using a motion capture system. We obtained high resolution peripheral computed tomography scans of the posterior calcaneus for both runners and non-runners. No statistically significant differences were found between runners and nonrunners or forefoot strikers and rearfoot strikers. Mean trabecular thickness and mineral density were greatest in forefoot runners with strong effect sizes (<0.80). Trabecular thickness was positively correlated with weekly running distance (r2 = 0.417, p<0.05) and years running (r2 = 0.339, p<0.05) and negatively correlated with age at onset of running (r2 = 0.515, p<0.01) Trabecular thickness, mineral density and bone volume ratio of nonrunners were highly correlated with body mass (r2 = 0.824, p<0.05) and nonrunners were significantly heavier than runners (p<0.05). Adjusting for body mass revealed significantly thicker trabeculae in the posterior calcaneus of forefoot strikers, likely an artifact of greater running volume and earlier onset of running in this subgroup; thus, individuals with the greatest summative loading stimulus had, after body mass adjustment, the thickest trabeculae. Further study with larger sample sizes is necessary to elucidate the role of footstrike on calcaneal trabecular structure. To our knowledge, intraspecific body mass correlations with measures of trabecular robusticity have not been reported elsewhere. We hypothesize that early adoption of running and years of sustained moderate volume running stimulate bone modeling in trabeculae of the posterior calcaneus.
Highlights
Trabecular bone forms porous networks in long bone epiphyses, joint articulations, and throughout the internal volumes of the foot bones
The purpose of the present study is to investigate possible trabecular bone adaptation resultant from a common activity that subjects bone to a regime of repetitive and high strain: endurance running
The largest effect sizes were found in comparisons of forefoot striking (FFS) vs. rearfoot striking (RFS), for three variables: Tb.Th (2.00), DTrab (1.17), and bone volume/total volume (BV/TV) (1.16)
Summary
Trabecular bone forms porous networks in long bone epiphyses, joint articulations, and throughout the internal volumes of the foot bones. Elastic properties of trabecular bone are a function of several characteristics, including the average thickness of each trabecular strut (trabeculae), the number of struts per unit area, the total volume of trabecular bone per unit area. (bone volume fraction: a function of trabecular number and thickness), orientation and connectivity of struts, and mineral density. Density of trabecular bone was first correlated with mechanical properties 50 years ago [1, 2], and by the 1970’s and 1980’s architectural properties were as well [3, 4, 5, 6]. Diederichs et al [7] found that CTderived trabecular properties are highly predictive of mechanical strength in the calcaneus, bone mineral density (r2 = 60%), bone volume fraction, (r2 = 63%) and average thickness of trabeculae (r2 = 53%). Trabeculae are usually aligned with the principle direction of strain [8], and degree of anisotropy- a measure of trabecular alignment- is positively correlated with mechanical strength in the prevailing direction of trabeculation [9]
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