Key Insights On Platelet-Rich Plasma For Soft Tissue Repair
While platelet-rich plasma (PRP) has emerged as a potential adjunctive modality for some lower extremity injuries, there is a lack of conclusive evidence in this regard. Accordingly, this author reviews the available literature and offers insights from his experience in using PRP for Achilles tendinosis and chronic plantar fascial pain.
While oral maxillofacial surgeons have been utilizing platelet rich plasma (PRP) for over a decade, PRP has become an increasingly hot topic in the realm of musculoskeletal pathology in recent years.1
Technicians would obtain PRP by obtaining a small amount of blood via IV puncture and separating the whole blood components from the platelets typically through the use of a centrifuge. The PRP contains numerous growth factors, including insulin-like growth factors (ILGF) 1 and 2, transforming growth factor-b (TGF-b), vascular endothelial growth factor (VEGF), fibroblast growth factor and hepatocyte growth factor, to name a few. The type and amount of growth factor are patient dependent.
The basic science behind PRP is fairly simple. Platelet rich plasma is simply defined as a sample of autologous blood with concentrations of platelets that are typically five times greater than baseline levels. The science of PRP basically involves the alpha-granules found within the platelets. Alpha-granules contain growth factors that affect all aspects of the healing cascade to facilitate healing of all types of tissue. The growth factors are proteins that are secreted and bind to a receptor on a membrane to exert a response from the cell, which leads to the healing response. Examples of these target cells are osteoblasts, fibroblasts, endothelial cells, epidermal cells and mesenchymal stem cells (MSCs). There is a high amount of interest in the use of PRP for soft tissue injuries but high quality literature is lacking.
There are several companies that have the capability of producing the PRP. The concentration typically consists of a separation of red blood cells, platelet concentration and platelet-poor plasma. The amount of blood that is needed to produce the PRP differs among the companies. Activation may occur with or without adding an activating agent. One may add thrombin and/or calcium chloride to begin platelet activation, formation of the clot and release of the growth factors. Some studies have shown the use of thrombin can inhibit bone formation with the use of demineralized bone matrix.2
The other option is not to use the activating agent. Reports by Mishra, Fufa and their respective colleagues have shown that the exposure of PRP to tendon derived collagen factor alone can cause a slow and sustained activation.3,4
Tendon and ligament injuries are both subdivided into acute and chronic injuries. Acute injuries involve tearing of collagen fibers; hematoma formation and subsequent healing through inflammation; cellular proliferation, regeneration and repair; and remodeling processes.5 On the other hand, chronic injuries are often associated with overuse and lead to a degenerative process. Tendinopathy involves collagen fiber disruption, mucoid degeneration, neovascularization and the absence of inflammation.6
What The Literature Reveals About Treating Acute Injuries With PRP
Animal studies by Batten and co-workers have shown that specific growth factors such as PDGF improve healing and mechanical strength in early ligament healing with the greatest response occurring within the first 24 hours.7 In another animal study, Murray and colleagues found the application of PRP facilitated early improvement in load to failure, maximum load and stiffness of porcine anterior cruciate ligament (ACL) suture repairs. However, they noted no improvement in laxity, maximum tensile load or linear stiffness with longer follow-up.8