Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog.

TLDR

The study evaluated tendon‑to‑bone healing in a canine model. Twenty adult mongrel dogs received a long digital extensor tendon graft into a 4.8‑mm drill hole in the proximal tibial metaphysis, and at five time points (2, 4, 8, 12, 26 weeks) the tendon‑bone interface was examined histologically and biomechanically. Histology showed progressive reestablishment of collagen‑fiber continuity and Sharpey‑like fibers, radiographs revealed trabecular bone remodeling, and biomechanical testing indicated that interface strength increased significantly from week 2 to week 12, correlating with bone ingrowth and tissue maturation, although all specimens failed by pull‑out or tendon rupture at later time points.

Abstract

Our study evaluated tendon-to-bone healing in a dog model. Twenty adult mongrel dogs had a transplantation of the long digital extensor tendon into a 4.8-millimeter drill-hole in the proximal tibial metaphysis. Four dogs were killed at each of five time-periods (two, four, eight, twelve, and twenty-six weeks after the transplantation), and the histological and biomechanical characteristics of the tendon-bone interface were evaluated. Serial histological analysis revealed progressive reestablishment of collagen-fiber continuity between the bone and the tendon. A layer of cellular, fibrous tissue was noted between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey fibers. High-resolution radiographs showed remodeling of the trabecular bone that surrounded the tendon. At the two, four, and eight-week time-periods, all specimens had failed by pull-out of the tendon from the bone tunnel. The strength of the interface was noted to have significantly and progressively increased between the second and the twelfth week after the transplantation. At the twelve and twenty-six-week time-periods, all specimens had failed by pull-out of the tendon from the clamp or by mid-substance rupture of the tendon. The progressive increase in strength was correlated with the degree of bone ingrowth, mineralization, and maturation of the healing tissue, noted histologically.