Joost Peerbooms

124 Chapter 8 Platelet-rich plasma (PRP) is derived from a patient’s own blood and is injected locally for several musculoskeletal disorders. In the laboratory it has been shown that PRP contains a high concentration of growth factors, and by injecting PRP, local repair reactions might be stimulated. The aim of injecting PRP would be to enhance biological repair processes, leading to reduction of patient complaints. Therefore, PRP has a place in the field of orthobiologics. Due to the limited results of conventional non-surgical treatment for some musculoskeletal disorders, there is great interest in the use of orthobiologics. Application of PRP has become popular, but there is limited evidence of its effectiveness. 1 The overall aim of this thesis was to study the place of PRP in the treatment of two frequently occurring tendon disorders, tennis elbow and plantar fasciitis, and for wound healing in total knee arthroplasty (TKA). We concluded that PRP injections outperforms corticosteroid injections in tennis elbow and plantar fasciitis. We did not find added value in using PRP in wound healing after TKA. In this chapter, we discuss the main findings of our studies and their significance for clinical practice. We will also discuss the complex comparison between different systems of PRP application and opportunities for further research. SECTION I: TENDINOPATHY In our studies we concluded that the group patients who received a PRP injection for their tennis elbow ( Chapter 5 and 6 ) or for plantar fasciitis ( Chapter 7 ) had a better outcome than patients who received a corticosteroid injection. This suggests that PRP reduces the patient complaints, but it may also demonstrate negative long-term effects of corticosteroid injections. The treatment of tendinopathy is challenging because the precise pathophysiology of tendinopathy is not known, and the origin of pain is not clear yet. Thus, this treatment is not based on hard science but on theoretical considerations related to the condition. Corticosteroid Injections Corticosteroid injections have been used to treat tendinopathy since the 1950s. 2 These injections are given directly into the area around the tendon. 3 Corticosteroid injections aim to modulate inflammatory cells and mediators, such as lymphocytes, macrophages and mast cells. 3 Essentially, corticosteroid injections reduce the pain caused by inflammation. However, injections of corticosteroids also increase protein catabolism, reduce the synthesis of type I collagen and therefore slow down repair reactions. 3 Given the rather limited inflammation in prolonged tendinopathy and the inhibition of collagen repair after corticosteroid injection, the usefulness of corticosteroid injections for chronic symptoms in tendinopathy has been subject to much debate. 4-6 Corticosteroid injections have shown to be effective in relieving pain in the short term. However, after longer periods, there tends to be a recurrence of symptoms. 4,5 In addition, several