Chronological changes in the collagen-type composition at tendon-bone interface in rabbits

Bone Joint Res. 2012 Sep 1;1(9):218-24. doi: 10.1302/2046-3758.19.2000109. Print 2012 Sep.

Abstract

Objectives: The purpose of this study was to evaluate chronological changes in the collagen-type composition at tendon-bone interface during tendon-bone healing and to clarify the continuity between Sharpey-like fibres and inner fibres of the tendon.

Methods: Male white rabbits were used to create an extra-articular bone-tendon graft model by grafting the extensor digitorum longus into a bone tunnel. Three rabbits were killed at two, four, eight, 12 and 26 weeks post-operatively. Elastica van Gieson staining was used to colour 5 µm coronal sections, which were examined under optical and polarised light microscopy. Immunostaining for type I, II and III collagen was also performed.

Results: Sharpey-like fibres comprised of type III collagen in the early phase were gradually replaced by type I collagen from 12 weeks onwards, until continuity between the Sharpey-like fibres and inner fibres of the tendon was achieved by 26 weeks.

Conclusions: Even in rabbits, which heal faster than humans, an observation period of at least 12 to 26 weeks is required, because the collagen-type composition of the Sharpey-like fibre bone-tendon connection may have insufficient pullout strength during this period. These results suggest that caution is necessary when permitting post-operative activity in humans who have undergone intra-bone tunnel grafts.

Keywords: Collagen-type composition; Immunostaining; Rabbits; Sharpey-like fibres; Tendon–bone healing; Tendon–bone interface.

Grants and funding

This work was supported by the Grant-in Aid for Scientific Research C: KAKENHI 20591769.