Structural and Functional Modulation of Early Healing of Full-thickness Superficial Digital Flexor Tendon Rupture in Rabbits by Repeated Subcutaneous Administration of Exogenous Human Recombinant Basic Fibroblast Growth Factor

The present study was designed to investigate the effects of basic fibroblast growth factor on the healing of the acute phase of complete superficial digital flexor tendon rupture in rabbits. A total of 40 skeletally mature female white New Zealand rabbits were randomly divided into 2 equal groups of injured treated and injured control. After tenotomy and surgical anastomosis, using a modified Kessler and running pattern, the injured legs were placed in casts for 14 days, and basic fibroblast growth factor was injected subcutaneously over the lesion on days 3, 7, and 10 after injury. The injured control rabbits received a normal saline injection in a similar protocol. The rabbits' weight, tendon diameter, clinical signs, radiographs, and ultrasound scans were evaluated weekly. The rabbits were killed 28 days after injury, and the tendons were evaluated at the macroscopic, histopathologic, and ultrastructural levels and for biomechanical and the percentage of dry weight analysis. Treatment significantly reduced the diameter and increased the echogenicity and dry weight content and enhanced the maturation rate of the tenoblasts, fibrillogenesis, collagen fibril diameter, fibrillar density, tensile strength, and stiffness and stress of the injured tendons. Treatment with basic fibroblast growth factor was effective in restoring the morphologic and biomechanical properties of the injured superficial digital flexor tendon and could be valuable in clinical trial studies.