EVALUATION OF AN AUTOLOGOUS TENDON GRAFT REPAIR METHOD FOR GAP HEALING OF THE DEEP DIGITAL FLEXOR TENDON IN HORSES

A sutured tenorrhaphy technique that incorporated an autologous tendon graft was compared mechanically and histologically with a sutured ten orrhaphy at 6, 12, and 24 weeks after repair. Tenorrhaphy was performe d in the forelimb tendon of the deep digital flexor muscle and the gra ft was taken from the hindlimb tendon of the lateral digital extensor muscle; one forelimb site included the graft, whereas the other foreli mb site was not grafted. Tenotomies were made immediately proximal to the insertion of the accessory ligament into the tendon of the deep di gital flexor muscle. Grafted and nongrafted tenorrhaphies were sutured with 2 polydioxanone in a modified double locking-loop pattern. Limbs were supported with a bandage and an extended elevated heel shoe that maintained the dorsal hoof wall angle at 70 degrees to 75 degrees; th is support was removed at 12 weeks and dorsal hoof wall angle was main tained at 40 degrees to 35 degrees for the remainder of the study. Gap formation (2.5 +/- .3 cm) was evident at all tenorrhaphy sires at 3 d ays on ultrasound examination. In grafted repairs, the breaking stress was increased (P < .001) between 6 weeks (2.56 +/- .44 MPa) and 12 we eks (17.69 +/- 7.68 MPa), with grafted tendon having a greater breakin g stress than nongrafted tendon (8.77 +/- 2.5 MPa; P < .05). No differ ences in breaking stress were evident at 24 weeks. At 12 weeks, repair tissue in grafted tendon was histologically more mature, had less cel lularity, better fibroblast orientation acid more homogeneous collagen matrix than nongrafted tendon. Polydioxanone suture was still evident histologically at 24 weeks and was associated with minimal cellular r eaction. Incorporation of an autologous tendon graft improved the mech anical properties and histological quality of the repair tissue in equ ine flexor tenorrhaphies at 12 weeks but not at 24 weeks after repair. (C) Copyright 1996 by The American College of Veterinary Surgeons.