PLATELET RICH PLASMA (PRP)
The PRP is obtained by withdrawing blood directly from the patient, with a needle of 18-20G, to avoid trauma to the platelets, which if damaged would release their growth factors early. The syringe contains an anticoagulant (ratio of sodium citrate and blood 1:9) in order to chelate calcium, block the coagulation cascade and preserve the growth factors. The blood is subsequently submitted to centrifugation and cell separation processes to obtain a new substance richer in platelets. After centrifugation, a composite laminate is obtained, consisting of red blood cells, platelet-poor plasma and platelet-rich plasma. Usually, the volume of PRP obtained is 1/10 of the volume of the whole blood (6ml per 60 ml of blood drawn or 3 ml per 30 ml of the fluid), added with sodium bicarbonate, about 0.05 ml for each ml of PRP, to buffer the acidity results from platelet metabolism: An excessive PH decrease could jeopardize the viability of platelets.
Once injected at the injection site, the platelets will activate in contact with substances such as collagen type I or through paracrine mechanisms related to the release of platelet activating factors from previous elements lysed by trauma incurred during handling.
The PRP may be injected either in this form after further activation with calcium gluconate or sodium bicarbonate. The activation leads to a faster release of growth factors; the possibility to activate PRP also depends on the intended use. The main advantages of PRP are safety (the blood is taken from the patient, who will use it - autologous PRP. In this way, the risk of contracting communicable diseases such as hepatitis is avoided, and cost effectiveness, especially compared to the costs of producing artificial tissues. The mechanisms of action of PRP are not fully known yet, but are believed to be related to a slow continuous release of growth factors present in abundance in the platelet gel. The action mechanisms of the best-known platelet growth factors are briefly exposed below.
- PDGF (Platelet derived growth factor) has mitogenic action (it induces mitosis, or cell replication) and induces angiogenesis; it also coordinates the action of other growth factors.
- TGF-beta (Transforming growth factor-beta) is a protein with many functions, including the stimulation of osteoblasts and fibroblasts and the inhibition of osteoclasts.
- IGF I / II - The IGF I and IGF II (insulin-like growth factor I / II) act by stimulating the production of osteoblasts and acting on precursors of the latter; they also stimulate the deposition of bone matrix.
- FGFB (Fibroblast growth factor basic) works by stimulating the migration of fibroblasts and collagen synthase. It is the growth factor that plays the most interesting role in the field of aesthetic medicine.
- EGF (Epidermal growth factor) works by stimulating the mesenchymal and epidermal cells.
When and how the growing interest in the use of blood derivatives such as platelet rich plasma (PRP) in the joint diseases is due to the release of the growth factors contained in platelets that have anti-inflammatory and regenerative capacity. The use of PRP under ultrasound guidance, in the treatment of degenerative processes and arthritic knee and hip, is efficient in terms of reduction of pain and recovery of functionality. The platelet gel exerts anti-inflammatory action related to the chemotactic activity towards cells of inflammation and promotes a true tissue regeneration due to the activation of growth factors. This, in theoretical terms, should lead at local level to a reduction of the inflammatory phenomena with effects on pain and in a partial tissue restoration.
Thanks to its regenerating capacity, PRP can also be used in degenerative diseases and in case of partial tendon lesions. In these cases, it is injected directly into the tendon structure, in a single site (in case of partial lesions) or in multiple locations of the tendon in case of diffuse degeneration. Usually, in clinical practice, PRP is used for tendinosis or partial lesions of tendons such as supraspinatus, Achilles and patellar tendons, or for epicondylitis, sports muscle injuries and flexor- extensor tendons of the hand.
Source for explanation: Barile A. “Anaesthetics, Steroids and Platelet Rich Plasma (PRP) in Ultrasound-Guided Musculoskeletal Procedures.” in Br J Radiol. 2016 Jun 15:20150355. Accessed at http://www.ncbi.nlm.nih.gov/pubmed/27302491