Specific distribution pattern of cartilage stiffness and thickness on the equine talus

Objective: This article deals for the first time with reference values for cartilage stiffness and cartilage thickness at the talus of the horse. Material and methods: 24 horses of different age (two foals, one yearling, 21 adults) were examined post mortem. Cartilage stiffness was determined in vitro at 23 measuring points on the talus by an indenter (Artscan (R) 200) which can be used likewise intra vitam. The measuring probe was placed on the cartilage at a force of 2 Newton (N) in an angle of 20 degrees for about 2 seconds. Cartilage thickness was determined using a magnifying measuring glass on 18 measuring points on the sliced cartilage preparation. In the newborn foal,the determination of the cartilage thickness was not possible due to the not yet finished enchondral ossification. In the adult horses,three to four measuring points were compared with one another on hypothetical measuring lines on and at the flanks of the trochlear ridges. With linear regression slopes (trends) on the proximodistal measuring lines were calculated within each horse. By means of the single-sample t test the mean slope was compared with zero to its statistical relevance. As regards the foal and the yearling, a descriptive statistical analysis was performed. Results: The hocks of the newborn foals showed a homogeneous distribution of the cartilage stiffness over the entire talus. The tali of the yearling already presented a clear heterogeneity of cartilage stiffness and thickness. In the adult animals, cartilage stiffness decreased significantly from proximal to distal (p <0.001). Cartilage thickness showed a contrary tendency and increased to distal. This trend was seen directly on the trochlear ridges as well as on the lateral flanks. Values from 0.873-1.321 Newton (N) were reached at the proximal measuring points, whereas the most distal ones reached only 0.375-0.550 N. Cartilage thickness here is antidromic to cartilage stiffness over the entire talus with proximal values from 0.49-0.78 mm and distal ones from 0.68-1.08 mm. Conclusions: The indenter system is useful to measure cartilage stiffness in the horse. Cartilage stiffness and thickness of the equine talus show a site-specific and age-related pattern. Clinical relevance: To detect early pathological changes in cartilage matrix intra vitam the specific distribution pattern of cartilage stiffness should be considered.