Combined application of PRP gel and low-intensity pulsed ultrasound enhances early tendon-to-bone interface healing after acute rotator cuff repair in rats

Abstract Objective This study evaluated the effects of combined platelet-rich plasma (PRP) gel and low‑intensity pulsed ultrasound (LIPUS) on early tendon–bone interface healing after acute rotator cuff repair in rats, using histological, micro-CT and biomechanical assessments to inform postoperative rehabilitation. Methods Ninety SPF-grade male Sprague-Dawley rats (8–9 weeks old, 300–350 g) were used: 80 underwent left-sided rotator cuff injury and repair and were randomly allocated into four groups (n = 20 each: CON, LIPUS, PRP, P + L), and the remaining 10 served as blood donors for PRP preparation. Within each group, 10 animals were euthanized at postoperative week 4 and 10 at week 8. At each time point, 5 animals per group were processed for micro-CT and histological analysis and the other 5 for biomechanical testing. Results At both time points, the combined group showed significantly higher bone volume fraction, trabecular thickness and number, fibrocartilage layer thickness, collagen fibre organization, ultimate load and stiffness than the other three groups (P < 0.05). LIPUS and PRP alone also improved these parameters over controls, but the combined regimen produced the most pronounced enhancement. Conclusion Collectively, the combined application of PRP gel and LIPUS further promotes early tendon-to-bone healing after acute rotator cuff repair, substantially improving local tissue structure and biomechanical properties.