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Platelet rich plasma (PRP) is widely used in regenerative medicine and especially in orthopaedic sport medicine [14, 34, 45]. Basic science studies show many positive effects of PRP in vitro and in vivo on many cells of the musculoskeletal system, e.g. chondrocytes, tenocytes or muscle cells [5, 6, 21, 33, 41]. However, the quality of the available literature remains limited, both of basic science and clinical studies [15, 21, 34]. As a result, in clinical studies the effects are not as clear as in basic science studies [12, 26, 34].
Possible reasons for this are numerous. To start with, multiple preparation methods (currently over 25 different commercial systems available ) exist to obtain platelet-derived growth factors, but the final PRP products are limited by their inhomogeneous composition and their elaborative production protocols [4, 37, 45, 50, 51, 55, 59]. For example, different PRP preparation methods have shown different effects on articular chondrocytes . Moreover, as the reporting of basic parameters like blood constituents (erythrocytes, leukocytes and thrombocytes) is still not performed in every study, there is an urgent need for a standardized reporting of these factors [13, 21]. Also there are large interindividual differences of the final PRP product . To complicate matters even further, the dosing, timing and number of PRP applications are not standardized and not yet investigated sufficiently in basic science studies . In this respect, the need for a standardized preparation of platelet-derived growth factors is obvious and would allow standardized basic science testing of the effect of different parameters like PRP preparation, amount of PRP injections and timing of injections [27, 36]. Further, the use of classifications to better describe the used PRP product should be mandatory. Several authors proposed different classification systems, among which are Mishra (platelet count, presence white blood cell, activation), Dohan Ehrenfest (platelet count, leukocyte count, presence of fibrin), Delong (Platelet count, Activation, White blood cells count; PAW classification) and Mautner (Platelet count, Leukocyte presence, Red blood cell presence, and use of Activation; PLRA classification) . Magalon et al. proposed the DEPA classification describing the Dose of injected platelets, Efficiency of production, Purity of the PRP and its Activation . Harrision et al. published another comprehensive classification system including activation method if used, the total volume used, the frequency of dosing and subcategories of activation, platelet concentration and preparation technique and includes the overall average counts and range (low–high) of platelets, red cells and differential leukocyte counts (neutrophils, lymphocytes and monocytes) . The most recent classification comes from Kon et al. based on an expert consensus and describing the most important factors to be reported as the platelet composition (concentration of platelets and concentration ratio), purity (presence of erythrocytes/leukocytes) and activation (endogenous/exogenous, addition of calcium) .
Many indications for PRP use are widely debated, e.g. the treatment of tendinopathies is complicated by the fact that clinical studies both describe positive and negative results for various locations [15, 22, 25, 31, 46, 48]. As a result, often no conclusive evidence can be drawn from the literature. This also makes it difficult for PRP therapy to be included in various guidelines. Since many open questions using PRP remain, the rationale of this paper was to display the current opinion of experts among the German “Working Group for Clinical Tissue Regeneration” of the German Society of Orthopaedics and Traumatology (DGOU) about the use of PRP and future research areas.
Source: Tischer, T., Bode, G., Buhs, M. et al. Platelet-rich plasma (PRP) as therapy for cartilage, tendon and muscle damage – German working group position statement. J EXP ORTOP 7, 64 (2020). https://doi.org/10.1186/s40634-020-00282-2