Biomechanical Properties of Canine Cruciate Ligament Prostheses

The aim of this study was to biomechanically test ligaments in different preparations from dead horses and dogs with respect to their suitability as a substitute for the cranial cruciate ligament.

Native CrCL breakage tests:
The biomechanical properties of the bilateral native cranial cruciate ligament (CrCL) from 28 dog were tested in different 5 geometrical stifle joint angles. The resulting biomechanical findings were related to the respective weights of the examined dogs, and were compared to the biomechanical properties of the CrCL.

Tendon breakage tests:
The native suitability of canine common calcaneal tendons (CCCT) and canine radial carpal extensor tendons (CRCET) from 30 euthanised dogs, and native equine deep digital flexor tendons (EDDFT) were obtained from two horses (euthanised or recently deceased). These were treated with a variety of decellulariation, and subsequently recellularisation methods and the biomechanical changes were evaluated. By comparing the effects of various methods on the collagen structure and biomechanics, the aim of the study was to identify the most effective decellularisation method and to determine which decellularisation method has more impact biomechanically on recellularised ligaments. Moreover, a variety of combinations were investigated, including t-octylphenoxypolyethoxyethanol (Triton-X 100) and tri-n-butyl phosphate (TnBP), in order to determine which combination exhibited the greatest biomechanical decellularisation effect in dogs' and horses' tendons. The biomechanical properties of all CrCL and canine and equine tendons were investigated in breaking-strength and elongation tests. The breaking strength of the specimens was elongated at a loading rate of 0.1 kN/s, force interspace: 3000 - 4000 N, test velocity: 10 mm/min. By way of a general overview for native CrCL and tendon breakage tests, the average breaking strength was found for canine CrCL samples (M = 1187.4 N; SD = 425.3), Fmax 2454 and Fmin 441N. For decellularised canine and equine tendons (M = 401.3 N; SD = 121.6), Fmax 656.2 N and Fmin 160 N; as well as recellularised canine and equine tendons (M = 499.8 N; SD = 139.6), Fmax 797.1 N and Fmin 174 N were measured. The breaking strength of canine CrCL samples was significantly higher than the breaking strength of decellularised canine and equine tendons, as well as recellularised canine and equine tendons. The test showed a significant effect of native CrCL and implant materials on the breaking strength. Additionally, the results for the elongation of native CrCL samples (M = 15.7 mm; SD = 8.3) was higher than in decellularised canine and equine tendons (M = 13.6 mm; SD = 5.7) as well as recellularised canine and equine tendons (M = 14.0 mm; SD = 4.4). Information obtained during this study could be applied to prostheses used in dogs with CrCL rupture, and it was suggested that a constant factor related to body-weight could be used to evaluate the approximate strength and elasticity of the CrCL.