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. Cite this article: Bone Joint Res 2026;15(9):1111–1122.