Ex-Vivo Biomechanical Testing of Tendon Implant Device for the Repair of Equine Flexor Tendon Lacerations

Abstract

Flexor tendon lacerations are a serious injury in horses that are life threatening and often career ending. An ideal tendon repair allows rapid return to weight bearing by providing a high strength to failure, high resistance to gap formation, minimal compromise of tendon vasculature and producing minimal adhesion formation. The 3 loop pulley (3LP) is the currently recommended primary repair technique for tendon lacerations in the horse. The 3LP is limited by gap formation, vascular compromise. This project compares the in vitro strength and failure characteristics of a novel tendon implant device (SA) against the 3LP in equine superficial digital flexor tendon laceration (SDFT) repair. 8 pairs of superficial digital flexor tendons were harvested with various breeds represented including: American Quarter Horses (3), Tennessee Walking Horse (2), Thoroughbred(2) and warmblood(1). Ultimate load to failure, mode of failure, gap at failure, and load to create a 2 mm gap were compared between the two repairs. Statistical evaluation was made using a Student’s T-test, with significance set at P≤0.05. The 3 LP failed at a significantly (P = 0.0001) greater load (363.5 N +/- 83.7 N) than SA (132.4 N +/- 26.8N), but the load to a 2 mm gap (3 LP = 164.9 N +/- 67.7 N, SA = 114.5 N +/- 21.5 N) was not significantly different (P = 0.09). Mode of failure was by suture pull out and anchor pull out respectively. The gap at failure was significantly larger in the 3LP, than in the SA repair (P = 0. 000005). Load to 2 mm gap formation is a clinically significant test, because gaps larger than 2 mm in lacerated tendons produce a weaker tendon callous than gaps smaller than 2 mm.