Efficacy of intra-tendinous injection of platelet-rich plasma in treating tendinosis: comprehensive assessment of a rat model.

Objectives: To assess the potential of intra-tendinous injection of platelet rich plasma (PRP) to treat tendinosis (T+) in a rat model of patellar and Achilles T+, and evaluate its local toxicity.

Methods: Thirty rats (120 patellar and Achilles tendons) were used. We induced T+ into 80 tendons (patellar = 40, Achilles = 40) by injecting collagenase at day 0 under ultrasound (US) guidance. Clinical examination and US at day 3, followed by US-guided intra-tendinous injection of either PRP (PRPT+, n = 40) or physiological serum (ST+, n = 40, control). Follow-up was at days 6, 13, 18 and 25 using clinical, US and histological evaluation. To study PRP toxicity, we injected PRP into 40 normal tendons (PRPT-) and compared with 40 untreated normal tendons (T-).

Results: All PRPT+ showed better joint mobilisation compared with ST+ at day 6 (P = 0.005), day 13 (P = 0.02), day 18 (P = 0.003) and day 25 (P = 0.01). Similar results were found regarding US and histology, with smaller collagen fibre diameters (day 6, P = 0.003, day 25, P ≤ 0.004), less disorganisation and fewer neovessels (day 6, P = 0.003, day 25, P = 0.0003) in PRPT+ compared with ST+. Comparison between PRPT- and T- showed no PRP toxicity (P = 0.18).

Conclusions: Our study suggests that mono-injection of PRP in T+ improves tendon healing, with no local toxicity.

Key Points: • We assessed the potential of platelet rich plasma (PRP) to treat tendinosis. • We treated patellar and Achilles tendinosis in a rat model. • We evaluated clinical, imaging and histological data. • Intra-tendinous PRP injection could be useful in the treatment of tendinosis.