Hippiatrik, Pferdeheilkunde, 6(21), p. 531-537, 2005
DOI: 10.21836/pem20050603
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The digital cushion in horses, hoof, and hoof cartilage are structures reducing mechanical loads. The digital cushion is fixed to adjacent structures by ligaments and thick fibre bundles. The pars torica of the digital cushion is localised between the heels, the pars cunealis is underlying the frog. Due to the hoof mechanism during locomotion, the pars torica undergoes more significant deformation than the pars cunealis. It is unknown whether different mechanical loads result in a different structure and fixation of the individual parts of the digital cushion. The aim of our study was to answer these questions. Digital organs of horses with an age of 0.5-28 years were examined macroscopically (n=20) and microscopically (n=20). The quantitative composition of the pars cunealis and the pars torica of the digital cushion in young and adult horses was assessed by the Cavalieri method, a stereological method for volume estimation based on section analysis. The compact pars cunealis and the soft-elastic pars torica already differed macroscopically. On the palmar/plantar side of the pars cunealis, massive fibre layers were predominantly directed towards the toe axis. The pars torica was fixed to the hoof cartilages by chondropulvinal ligaments and finger-shaped interdigitations. The digital cushion contained 39.3% dense, irregular, connective tissue, 37.6% tissue with matrix rich in hyaluronic acid, 17.4% elastic fibres and 5.7% adipose tissue. Dense connective tissue was found mainly in the pars cunealis. In foals, the pars torica contained more adipose tissue than in adult horses, where it was replaced by dense connective tissue and tissue with a hyaluronic-acid rich matrix. Elastic fibres were mainly detected in the pars torica and the transition zone between pars torica and pars cunealis. The composition of the digital cushion varied individually, probably due to different work loads and purposes of use of the examined horses. Further studies, preferentially in horses under the same training conditions are necessary to obtain information on the influence of mechanical loads on the inner structure of digital cushions.