title: Rabbit Achilles tendon full transection model - wound healing, adhesion formation and biomechanics at 3, 6 and 12 weeks post-surgery.
abstract: After tendon rupture repair, two main problems may occur: re-rupture and adhesion formation. Suitable non-murine animal models are needed to study the healing tendon in terms of biomechanical properties and extent of adhesion formation. In this study 24 New Zealand White rabbits received a full transection of the Achilles tendon 2 cm above the calcaneus, sutured with a 4-strand Becker suture. Post-surgical analysis was performed at 3, 6 and 12 weeks. In the 6-week group, animals received a cast either in a 180 deg stretched position during 6 weeks (adhesion provoking immobilization), or were re-casted with a 150 deg position after 3 weeks (adhesion inhibiting immobilization), while in the other groups (3 and 12 weeks) a 180 deg position cast was applied for 3 weeks. Adhesion extent was analyzed by histology and ultrasound. Histopathological scoring was performed according to a method by Stoll et al. (2011), and the main biomechanical properties were assessed. Histopathological scores increased as a function of time, but did not reach values of healthy tendons after 12 weeks (only around 15 out of 20 points). Adhesion provoking immobilization led to an adhesion extent of 82.7±9.7%, while adhesion inhibiting immobilization led to 31.9±9.8% after 6 weeks. Biomechanical properties increased over time, however, they did not reach full strength nor elastic modulus at 12 weeks post-operation. Furthermore, the rabbit Achilles tendon model can be modulated in terms of adhesion formation to the surrounding tissue. It clearly shows the different healing stages in terms of histopathology and offers a suitable model regarding biomechanics because it exhibits similar biomechanics as the human flexor tendons of the hand.
authors.affiliation: Division of Plastic Surgery and Hand Surgery, University Hospital Zurich, Sternwartstrasse 14, Zurich 8091, Switzerland.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Meier Bürgisser
authors.affiliation: Division of Plastic Surgery and Hand Surgery, University Hospital Zurich, Sternwartstrasse 14, Zurich 8091, Switzerland.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Calcagni
authors.affiliation: Uniklinik Balgrist, Department of Orthopedics, Forchstrasse 340, Zurich 8008, Switzerland.
authors.forename: Elias
authors.initials: E
authors.lastname: Bachmann
authors.affiliation: Uniklinik Balgrist, Department of Orthopedics, Forchstrasse 340, Zurich 8008, Switzerland.
authors.forename: Gion
authors.initials: G
authors.lastname: Fessel
authors.affiliation: Uniklinik Balgrist, Department of Orthopedics, Forchstrasse 340, Zurich 8008, Switzerland Laboratory for Orthopaedic Biomechanics, Swiss Federal Institute of Technology in Zurich (ETHZ), Rämistrasse 101, Zurich CH-8092, Switzerland.
authors.forename: Jess G
authors.initials: JG
authors.lastname: Snedeker
authors.affiliation: Division of Plastic Surgery and Hand Surgery, University Hospital Zurich, Sternwartstrasse 14, Zurich 8091, Switzerland.
authors.forename: Pietro
authors.initials: P
authors.lastname: Giovanoli
authors.affiliation: Division of Plastic Surgery and Hand Surgery, University Hospital Zurich, Sternwartstrasse 14, Zurich 8091, Switzerland johanna.buschmann@usz.ch.
authors.forename: Johanna
authors.identifier: http://orcid.org/0000-0001-7919-7448
authors.initials: J
authors.lastname: Buschmann
keywords: Achilles tendon; Adhesion; Elastic modulus; Load until failure; Ultimate stress