Enhancing meniscal repair through biology: platelet-rich plasma as an alternative strategy

Meniscal tears are common orthopaedic injuries that can manifest with significant pain and mechanical symptoms. The treatment of meniscal tears has evolved from total meniscectomy to partial meniscectomy and meniscal repair. Preserving the meniscus is ideal because the loss of any portion of the meniscus can lead to significantly increased articular cartilage contact stresses compared with the intact state. However, most of the meniscus has a limited ability to heal because of poor vascularity. This has prompted a search for a better understanding of the biology of meniscal healing and methods to enhance the process. Growth factors have been shown to positively affect meniscal cell function, including platelet-derived growth factor, fibroblast growth factor, basic fibroblast growth factor, transforming growth factor-β, insulin-like growth factor, bone morphogenetic protein, hepatocyte growth factor, and vascular endothelial growth factor. In vitro studies have shown that other cytokines, including interleukin-1, tumor necrosis factor-α, and the matrix metalloproteinases, negatively affect meniscal healing. Identification of these growth factors has led to strategies to deliver serum-derived factors to the meniscus to improve healing. Platelet-rich plasma is the latest technique to be evaluated for augmenting meniscal healing. Activation of the platelets leads to the local release of growth factors from the alpha and dense granules located in the platelet cytoplasm. These growth factors have been associated with the initiation of a healing cascade leading to cellular chemotaxis, angiogenesis, collagen matrix synthesis, and cell proliferation.