Tendon injury healing with G-90 in a rabbit model: biomechanical and histopathological evaluation

Tendon injuries are one of the most common and disabling acute orthopedic disorders. Several techniques are used to restore the mobility of patients, but all have significant limitations. In some studies utilization of biomaterials has been investigated in the healing of tendons, skin and nerves. The present study was designed to investigate the effects of G-90, as a stimulating factor agent, on the healing of the superficial digital flexor tendon (SDFT) of rabbits after 35 days post tenotomy and surgical repair. Twenty male rabbits, 12 months old and weighing 2.0 +/- 0.5 kg were used in this study. All rabbits were anesthetized, and the superficial flexor tendons of both hind limbs were cut transversely and then sutured with a Bunnel-Mayer suture pattern. After suturing tendons and skin, 0.5 mL of normal saline was injected in the injured tendon area of the left leg and 0.5 mL earthworm extract (EW) G-90 was injected at a concentration of 10 mg/mL into the injured tendon area of the right leg. Every two weeks 4 rabbits were euthanized, and samples were collected and sent for histopathological and biomechanical evaluation. In the histopathological evaluation less inflammation, more maturity of fibrocytes and more aggregation of collagen fibers were observed in tendons treated with G-90 in comparison with untreated tendons. In the biomechanical evaluation the ultimate strength of tendons treated with G-90 was superior to untreated tendons. The findings of the present experiment clearly show that administration of G-90 could enhance the structural and biomechanical properties of the experimentally tenotomized SDFT in rabbits.