The mechanical and histological estimation of calcaneal tendon callus in rats after PRP injection

The study investigated the potential impact of platelet-rich plasma on tendon healing.

The study was conducted in 88 young, sexually mature rats, Wistar strain. The animals were randomly divided into two groups. The animals from the examined group (n=44) with an operated calcaneal tendon were given subcutaneously allogeneic PRP. The animals from the control group (n=44) were given 0.9% NaCl solution within the area of calcaneal tendon damage. After 7, 14, 21, and 42 days, the tendons were tested mechanically using the universal testing machines (UTM, Lloyd LRX), and were subjected to histological evaluation.

The study evaluated the maximum breaking force (Fmax), the force at the end of the proportional range (Fs) and stiffness of the tendons (H). After 7 days of the experiment, there were significant differences in H (P=0.021), between the examined and control groups. There were no significant differences in Fmax (P=0.53) and Fs (P=0.48) after 7 days. Mean values of Fmax, Fs and H after 14, 21, and 42 days in the study group were significantly higher compared to the control group (P<0.05). In the histological evaluation, the tendons of the examined groups were characterized by higher cellular and vascular density and a more orderly arrangement of collagen fibers compared to the control groups.

Growth factors in allogeneic PRP increased the mechanical strength of regenerating calcaneal tendons after 14, 21, and 42 days from injury. PRP resulted in the increased histological maturity of the tendon callus in examined groups, at each stage of the experiment.