A biodegradable polyurethane adhesive augments tendon-bone interface healing in a rat Achilles repair model.

AIMS: Surgical repair infrequently restores the native tendon-bone interface (TBI, also referred to as the enthesis), resulting in excessive scar formation, compromised biomechanics, and frequent re-tears. A simple, biodegradable surgical adjunct that supports tendon-bone healing could augment standard repair strategies. In this study, we evaluated a biomimetic, amino acid-based biodegradable polyurethane adhesive as an intraoperative adjunct to standard suture repair in a rat Achilles tendon-calcaneus model. METHODS: A total of 90 female Sprague-Dawley rats (8 weeks old) were randomly assigned to two groups: suture-only and suture + adhesive (n = 45 per group). In the enthesis injury model, after transection and drilling, the polymer adhesive was freshly prepared and applied directly to the tendon-bone interface prior to suture tightening. The contralateral limb served as an intact control. Animals were sacrificed at four-, eight-, and 12-week timepoints, and tissues were evaluated using histological, imaging, micro-CT, and biomechanical analyses. RESULTS: Compared with suture-only repair, the suture + adhesive treatment was associated with more organized fibrocartilage formation, improved collagen I/III organization, greater proteoglycan deposition, and a smaller, more compact repair interface. When normalized by cross-sectional area, the adhesive group exhibited higher ultimate stress (tissue-level mechanical strength), although ultimate stress remained below that of intact controls. Whole-construct mechanical properties were comparable between groups, suggesting that the adhesive served as a biological and structural adjunct that was associated with improved intrinsic tissue quality, rather than increased construct-level strength. CONCLUSION: These findings suggest that a biodegradable polyurethane adhesive is associated with improved structural organization and intrinsic tissue-level mechanical properties of the repaired tendon-bone interface. Its straightforward intraoperative use and favourable biocompatibility profile support further investigation of its potential as an adjunctive strategy for tendon-bone repair.