**9. Tendinopathies**

and then implanted in osteochondral defects (4 x 3 mm) produced in the patellar sulcus of rabbit femurs. Evaluation of tissues was completed after 6 and 12 weeks by histological analysis and a mechanical indentation test. The results in both follow-up times were improved and showed that PRP possesses the capacity to stimulate the regeneration of critical defects in

According to Patel et al. in a study with level 1 evidence, PRP has a superior effect compared to placebo in patients with varying degrees of knee OA. They tested 78 patients (156 knees) and observed that PRP alleviated the symptoms of OA when compared with a saline injection used as control. Follow-up period was up to 6 months. The results showed that with the help

Wei et al. reported the effect of PRP on the regeneration of cartilage in vivo. Auricular cartilage

in the dorsum of the donor animal, and after 60 days the tissue was evaluated by magnetic resonance, histological, and histochemical analysis. The results exhibited cartilaginous tissue formation in those groups that were injected with chondrocytes and PRP. In the groups in

observed. The authors inferred that PRP is effective in stimulating regeneration of cartilage

A level 1 study published in 2012 in the Journal of Arthroscopy by Sanchez et al. used PRP type 4A to observe the results of PRP injection compared with hyaluronic acid. In this study 176 patients, were randomized to receive three weekly applications of PRP (8 ml at weekly intervals) or hyaluronic acid injections. The study was well-conducted, but the results only focused on the short term (until 6 months of follow up). The study was awarded as the best randomized clinical trial (level 1) for 2012, which gives useful fundamental guidelines on how

In the light of orthopedic and trauma critical literature, there is no standardization of treatment methods, such that most of the works use 3–5 applications of PRP in intervals ranging from 1–3 weeks with no standardization of the amount of volume to be applied and the ideal platelet

Important factors for results of PRP treatment are the amount of platelets, grade of chondrocyte damage, patient's physical activity, and medical history combined with psychosocial factors. It is good to investigate whether PRP balances anabolism-catabolism, and if there is, what effect of does the PRP have on the synovium. Given the patient's condition, appropriate PRP treatment in OA should use more anti-inflammatory cytokines instead of pro-inflammatory cytokines. The future of OA research aims at isolating cytokines contained in PRP termed as "autologous conditioned serum" to specifically inhibit IL-1 and TNF alpha and down regulate

Early OA can be treated by implementing intra-articular PRP. Worse outcome is observed with patients of advanced age and disease process. Khoshbin et al. compared intra-articular administration of PRP to hyaluronic acid and non-setoroid injections and reported that

cells/ml PRP), injected subcutaneously

of PRP, the homeostasis and function of the knee joint can be improved [74,75].

which only PRP was injected, cartilaginous tissue formation was not

chondrocytes from rabbits were added to PRP (5 x 107

when associated with viable cells [56,76].

to study the effects of PRP [74,77,78].

concentration method [74].

MMP-13 [25,79].

cartilage [56,73].

182 Immunopathology and Immunomodulation

Efficiency of PRP for treating tendinopathies has been vastly studied, and obtained results have been mostly positive (both in vitro and in vivo). Other research also supports the use of PRP for treating tendinopathies through testing cultures of equine and human cells [82,83]. An increase in the types of expression of collagen genes in tendon cell cultures with PRP was presented in a study by Schnabel et al [84]. Similar results were shown by Mishra and Pavelko in their study including an improvement in the pain felt by 15 patients with chronic elbow tendinosis after a single application of PRP [85]. In the PRP-treated group, 93% of the cases achieved pain reduction. Schepull et al. published the first randomized clinical study on the use of PRP in complete ruptures of the ankle tendon. Elasticity was evaluated after 7 weeks and functional assessments were completed after 1 year [86].

Creaney et al. in a recent study concluded that patients with resistant elbow tendinopathy were also considered appropriate for PRP treatment [87]. According to Peerbooms et al. in a double-blind study, with a level of evidence 1, the use of PRP in the treatment of chronic lateral epicondylitis was more favourable than injections of corticoids [88].

A significant statistic improvement at 1 year was observed in the group treated with PRP in comparison to the corticosteroid group that showed improvement only at the beginning. It can be inferred that in addition to conservative treatments, PRP provides a viable therapeutic alternative for refractory tendinopathies (as confirmed in a South Korean study in PRP treatment resulting in "increased cell proliferation, genic expression and synthesis of the tendon matrix in degenerative injuries of the rotatory cuff") [89].

Other findings include the successful use of PRP (alternatively to conservative therapies) in Achilles tendon injuries in conjunction with stem cells and with other various tendinopathies of 203 patients (epicondylitis, patellar tendonitis, hamstring origin (ischial tuberosity) tendo‐ nitis, plantar fasciitis, flexor carpi ulnarii tendonitis, pes anserinus tendonitis, biceps femoris tendonitis, iliopsoas tendonitis, athletic pubalgias, and biceps brachii tendonitis) whose status did not improve during conservative therapies [90]. Local infiltration with PRP was applied and 75% success ratio in patients was achieved. According to Virchenko and Aspenberg, and in another study by Eliasson et al. in Achilles tendon rupture patients, results are better with percutaneous suture, PRGF placement, and early load-bearing and mobilization [83,91,92].
