Encircling the tendon repair site with collagen-GAG reduces the formation of postoperative tendon adhesions in a chicken flexor tendon model

Abstract

Background: Tendon healing is a complex and coordinated event involving the activation of extrinsic mechanisms as in classic reparative skin wound healing as well as intrinsic mechanisms characteristic of regenerative wound healing. Despite improvements in surgical and rehabilitative techniques, tendon adhesions remain the most frequent cause of disability following tendon surgery. In this animal model, we evaluated the use of a clinically available, biocompatible collagen- glycosaminoglycan (GAG) material as an adjunct to surgical tendon repair.

Methods: Thirty-two white leghorn chickens underwent surgical tendon repair of their left second and fourth digits. Digits were randomized to study and control groups. In both groups, the long flexor tendon was divided and repaired using a modified Kessler's repair. In the study group, collagen-GAG membrane was wrapped around the repair site. Animals were immobilized with a plaster cast and sacrificed at 3 wk. Sixteen animals had their tendon repair sites histologically assessed and graded for healing and adhesion formation. Eight animals had their tendon repairs assessed for quantification of the work associated with flexion, employing a specifically designed biomechanical apparatus. Eight animals had their repair sites tested for bursting strength.

Results: Control (untreated) tendons showed fibrous tissue surrounding the repair sites with approximately 50% of the circumference of the repair site adherent to surrounding tissue elements. The mean histologic grades for control and study group were 3.1+/-0.2 and 1.9+/-0.2, respectively. The difference between mean grades for control and study group samples was statistically significant (paired t-test: P<0.01). The work of flexion (WOF) for flexion cycles 1, 2, 3, and 4 for the control group was 0.58, 0.55, 0.46, and 0.44N/mm, respectively. The study (collagen-GAG wrapped) group had WOF values 0.16, 0.14, 0.10, 0.09N/mm, and the difference between the groups was statistically significant (paired t-test, P<0.01). The mean bursting strength of repaired tendons for control and study groups were 14.3+/-1.87N and 11.5+/-1.85N, respectively. There was no significant difference in bursting strength between the groups (paired t-test, P=0.71).

Conclusions: Collagen-GAG reduces formation of early postoperative tendon adhesions in this chicken flexor tendon repair model. Collagen-GAG wrapped tendons healed with minimal peritendinous adhesion formation and required less effort for flexion. The investing collagen-GAG membrane did not appear to interfere with either the quality or strength of healing.