Equine Proximal Phalanx Bone Properties During Growth

Fatigue is the most common cause of fractures in racing horses. Bone adaptation can be driven by mechanical loading, and exercise during youth has been shown to have life long benefits for bone health. However, normal development must be characterized in order to evaluate the effect of exercise during post-natal skeletal development. Three Standardbred trotting colts were longitudinally CT scanned between 2 and 12 months old. Finite-element models were constructed of the left forelimb proximal phalanx (P1) bone and used to simulate the loading during quiet standing. Changes in mineral density and bone area fraction in the distal, diaphysis, and proximal regions were evaluated. The diaphysis of the P1 maintained constant strain energy density (SED) during growth, indicating adaptation to the standing condition. The proximal region experienced the most changes in mineral density and bone area fraction in the medial quadrant, which is the quadrant most loaded when young horses graze. The data presented provides a benchmark of normal growth trajectories that can be used to evaluate the effect of training regimens during growth.

Year	Entry
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Year

Entry

1992

Gross TS, McLeod KJ, Rubin CT. Characterizing bone strain distributions in vivo using three triple rosette strain gages. J Biomech. September 1992;25(9):1081-1087.

1994

Les CM, Keyak JH, Stover SM, Taylor KT, Kaneps AJ. Estimation of material properties in the equine metacarpus with use of quantitative computed tomography. J Orthop Res. November 1994;12(6):822-833.

1996

Martin RB, Gibson VA, Stover SM, Gibeling JC, Griffins LV. Osteonal structure in the equine third metacarpus. Bone. February 1996;18(2):165-171.

2013

Zysset PK, Dall'Ara E, Varga P, Pahr DH. Finite element analysis for prediction of bone strength. BoneKEy Rep. August 2013;2:386.

1982

Biewener AA. Bone strength in small mammals and bipedal birds: do safety factors change with body size? J Exp Biol. June 1982;82:289-301.