Healing of the Torn Anterior Horn of Rabbit Medial Meniscus to Bone after Transtibial Pull-Out Repair and Autologous Platelet-Rich Plasma Gel Injection.

ABSTRACT

OBJECTIVES: The transtibial pull-out repair (TP) is a relatively new method for treating meniscal root tear; however, the clinical evaluation of its healing effect remains controversial. Due to ethical constraints and limitations of imaging techniques in humans, here we dynamically observe the healing effects of TP and TP with platelet-rich plasma gel (PRG) at the histological level using an animal model. METHODS: Platelet-rich plasma (PRP) and PRG of rabbits were prepared. Platelet-derived growth factor (PDGF) and transforming growth factor-ß1 (TGF-ß1) levels in PRP and PRG were determined using an enzyme-linked immunosorbent assay. A rabbit model of anterior horn tear of the medial meniscus and TP surgery were created. PRG was injected between the anterior horn of the medial meniscus and the tibial tunnel. Rabbits were divided into three groups the anterior horn tear group (Tear group), the anterior horn tear + TP group (TP group), and the anterior horn tear + TP + PRG group (TP + PRG group). The healing effect was observed dynamically using histopathological studies and biomechanical experiments. RESULTS: The platelet content in PRP significantly increased to approximately 4.57 times that of whole blood. PDGF and TGF-ß1 concentrations in PRG increased to 2.46 and 4.15 times those in PRP, respectively. Hematoxylin and eosin (H&E) and Masson staining showed that the number of inflammatory cells in healing tissue decreased and the collagen fibers significantly increased in TP and TP + PRG groups at 4, 8, and 12 weeks postoperatively compared to those in Tear group. Neatly arranged, interlaced, and dense collagen fibers were found between the anterior horn and bone at 12 weeks. H&E and toluidine blue staining showed that the injury to the femoral condyle cartilage was alleviated. The healing performance in TP + PRG group was better and faster than that in TP group. The maximum tensile fracture strength of the meniscus progressively increased at 8 and 12 weeks postoperatively. CONCLUSIONS: Anterior horn injury of the medial meniscus in rabbits can be repaired using the TP technique, and the addition of autologous PRG to the bone tunnel promotes early healing of the meniscus and bone postoperatively. Meanwhile, both treatments can reduce the secondary damage to the cartilage due to osteoarthritis.