Determination of mechanical loading components of the equine metacarpus from measurements of strain during walking.
BACKGROUND
The mechanical environment of the distal limb is thought to be involved in the pathogenesis of many injuries, but has not yet been thoroughly described.


OBJECTIVE
To determine the forces and moments experienced by the metacarpus in vivo during walking and also to assess the effect of some simplifying assumptions used in analysis.


METHODS
Strains from 8 gauges adhered to the left metacarpus of one horse were recorded in vivo during walking. Two different models - one based upon the mechanical theory of beams and shafts and, the other, based upon a finite element analysis (FEA) - were used to determine the external loads applied at the ends of the bone.


RESULTS
Five orthogonal force and moment components were resolved by the analysis. In addition, 2 orthogonal bending moments were calculated near mid-shaft. Axial force was found to be the major loading component and displayed a bi-modal pattern during the stance phase of the stride. The shaft model of the bone showed good agreement with the FEA model, despite making many simplifying assumptions.


CONCLUSIONS
A 3-dimensional loading scenario was observed in the metacarpus, with axial force being the major component.


CONCLUSIONS
These results provide an opportunity to validate mathematical (computer) models of the limb. The data may also assist in the formulation of hypotheses regarding the pathogenesis of injuries to the distal limb.
Merritt
J S
JS
Faculty of Veterinary Science, The University of Melbourne, Australia.
Burvill
C R
CR
Pandy
M G
MG
Davies
H M S
HM
D000818:Animals; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology; D006736:Horses / Q000502:physiology*; D008124:Locomotion / Q000502:physiology; D008297:Male; D008663:Metacarpus / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000502:physiology; D013314:Stress, Mechanical; D016138:Walking / Q000502:physiology*