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PURPOSE: To develop an adhesion assessment rat model that will enable accurate testing of scar barriers and adhesion inhibiting treatments in future research.

METHODS: Thirty-six 6-month old male Sprague-Dawley rats were randomized to one of three groups of twelve. In Group A, the middle 1/3 portion of Achilles tendon was excised. In Group B, the tendon and soft tissue bed was abraded with steel wool. In Group C, a silk suture was sewn along the tendon. The right hind limbs served as controls, Group D. At 4 weeks, biomechanical testing was performed on bilateral hind limbs. The Achilles tendon was cut at the gastrocnemius-tendon junction proximal to the "adhesion zone" (or analogous level in the control limb). The calcaneal insertion of the Achilles was attached to a tensiometer. The force needed to pull the tendon out of its soft tissue envelope at a fixed rate was measured.

RESULTS: Three rats were excluded due to complications during data collection. Pair-wise comparison testing was performed, comparing the peak mean force to pull the Achilles tendon from its soft tissue envelope in 33 control limbs and the contralateral limb from each group. The average peak force for the cut tendon group (A) was 20.1N, 18.8N in the steel wool group (B), and 21.1N in the suture group (C). The average peak force in the control limb group (D) was 15.6N. There was a significant difference noted in peak forces between the control limb and the cut tendons (p= 0.0014), the control and tendons rubbed with steel wool (p= 0.0005), and the control and tendons with suture placement (p=0.000005). There was no statistical difference detected between experimental groups.

CONCLUSION: A consistent and statistically increased force was necessary to pull a rodent Achilles tendon from an adhesion induced tissue bed compared with controls.

CLINICAL RELEVANCE: Our study demonstrates an objective, straight-forward method of biomechanical tendon adhesion assessment in a rat model.