Comparing the mechanical performance of a new VetWelding® anchor system to a standard suture system for trauma therapy of the ruptured feline Achilles tendon

Abstract

In this work, a standard intra-osseous suture method was biomechanically compared to a new anchor method of tendon re-fixation by in-vitro tensile testing of feline Achilles tendon samples. A functional interface between bone and tendon is crucial to ensure load transmission and therefore, the skeletal motion in all mammals. For cats, the standard procedure for therapy of an Achilles tendon avulsion is suturing the tendon to an intra-osseous tunnel, pre-drilled in the distal calcaneus. An alternative to the tunnel suture is the application of a suture anchor, implanted into the calcaneus. Exemplary, the thermoplastic VetWelding Weldix© anchor can be stimulated by applying ultrasonic energy, making the material mold exactly into the bone structure and leading to a high primary stability compared to other anchor systems. The objective of this study is the investigation of gap development between bone and tendon upon tension, as extensive gap formation can hinder the healing of the repaired site. Results show that samples that were prepared by suture anchor develop a significantly smaller gap compared to samples that were prepared by the intra-osseous tunnel when exposed to the same load. A reference gap of 0.5 mm is reached within the intra-osseous group at a mean tendon load of (23.0 ± 15.4) N, while anchor samples needed almost double the load with a mean of (44.2 ± 5.5) N to reach the same gap-size. This means that the use of a suture anchor leads to less disturbance of the repaired bone-tendon interface and might improve the healing process. At the same time, the maximum load before suture failure is comparable between both groups. This work shows that the biomechanical properties of the VetWelding Weldix© suture anchor are favorable compared to the state-of-the-art intra-osseous tunnel method. For better statistical analysis, more tests can be done in the future, especially a pairwise analysis would require more samples.