Material Properties are Related to Stress Fracture Callus and Porosity of Cortical Bone Tissue at Affected and Unaffected Sites

Rachel C. Entwistle,, University of California - Davis
Sara C. Sammons, University of California - Davis
Robert F. Bigley, University of California - Davis
Scott J. Hazelwood, California Polytechnic State University, San Luis Obispo
David P. Fyhrie, University of California - Davis
Jeffery C. Gibeling, University of California - Davis
Susan M. Stover, University of California - Davis

Article comments

This is the pre-peer reviewed version of the following article: Material Properties are Related to Stress Fracture Callus and Porosity of Cortical Bone Tissue at Affected and Unaffected Sites, [Rachel C. Entwistle, Sara C. Sammons, Robert F. Bigley, Scott J. Hazelwood, David P. Fyhrie, Jeffery C. Gibeling, Susan M. Stove], Journal of Orthopaedic Research, 27:10, Copyright © 2009 Wiley-Blackwell., which has been published in final form at http://dx.doi.org/10.1002/jor.20892.

Abstract

Stress fractures are overuse injuries of bone that affect elite athletes and military recruits. One response of cortical bone to stress fracture is to lay down periosteal callus. The objectives of this study were to determine if material properties are different among bones with different stages of stress fracture callus, at both a callus site and at a distal site. Cortical specimens were mechanically tested to determine their stress–strain response. Material property differences were examined using nonparametric and regression analyses. At the callus site, material properties were low during the earliest stages of callus, higher with increasing callus maturity, but dropped at the late stage of callus. At the distal site, the material properties were low during early stages of callus and approached, or returned to, those of bones without callus during the late stages of callus. The effects of stress fracture and bone callus are not limited to the focal site of stress fracture