Ex vivo Biomechanical Comparison of Two Anchoring Systems and Two Suture Patterns for Calcanean Tendon Attachment to the Calcaneus in Dogs

Introduction: Canine calcaneal tendon injury is a common musculoskeletal injury often requiring surgical intervention. Despite the need for surgery, prognosis is often poor. It has been concluded that knot slippage contributes to gap formation of tendon repairs. In human orthopaedics and sports medicine, knotless anchors are becoming the standard of care for reattachment of tendons/soft tissues. The purpose of our study was to perform ex vivo biomechanical testing of calcaneal tendons either sutured or directly anchored to the calcaneal tuber in canine cadavers.

Materials and Methods: 20 cadaveric pelvic limbs underwent calcanean tendon insertion transection then repaired by 1 of 4 methods; three-loop pulley (TLP) with 0-polypropylene or no. 2-Fiberwire in a Speed-whip (SW) attached with either a knot (KN) through transosseous tunnels (1.5 mm) or 2, 3.5 mm Swivelock (SL) bone anchors placed into the calcaneal tuber. Ex vivo calcanean tendon mechanical testing was then performed at a load rate of 25 mm per minute until construct failure. Ultimate strength and stiffness were calculated. Significance was set at p < 0.05.

Results: There was no significant difference of ultimate strength between test groups (p = 0.62). Stiffness was significantly greater for the repairs performed with SL with either suture pattern compared with KN with the same suture patterns (p < 0.0001).

Discussion/Conclusion: SL anchors provide greater construct stiffness than suture bone tunnels placed into the calcaneal tuber for calcanean tendon repair. Increased stiffness provides resistance to gap formation of a tendon repair site when a patient ambulates.

Acknowledgment: Study funding provided by Arthrex. WMK and SAM are paid consultants for Arthrex. J.K. is a paid employee of Arthrex