Determination of the stiffness of the equine spine.

Abstract

REASONS FOR PERFORMING STUDY: Mechanical properties of the equine back are the bases for realistic modelling of the back, which is recognised as an important step towards improved understanding of the pathogenesis of equine back conditions. HYPOTHESIS: The stiffness of the equine back depends on the direction of the applied force and on the position of the spine. METHODS: Fourteen dissected spines were tested in a tensile testing machine. In 3 different positions, simulating dorsoventral, laterolateral and dorsoventral-30 degree rotated movement, force was applied on the dorsal spinous process of T12 to reach an excursion of 4 cm in each direction. The normal distribution of the stiffness coefficients was tested with a Kolmogorov-Smirnov test and the stiffness coefficients were compared with paired t tests. RESULTS: Mean +/- s.d. dorsoventral stiffness was 2093 +/- 611 N/m for the nonrotated spine and 2182 +/- 459 N/m for the 30 degree rotated spine. Mean laterolateral stiffness was significantly lower than dorsoventral stiffness at 1454 +/- 156 N/m. CONCLUSIONS: The stiffness of the spine depends on the direction of loading. POTENTIAL RELEVANCE: The stiffness of the spine under loading may be a relevant factor in the development of back disorders.