• Teemu V Karjalainen, Michael Silagy, Edward O'Bryan, Renea V Johnston, Sheila Cyril, and Rachelle Buchbinder.
• Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University; Monash-Cabrini Department of Musculoskeletal Health and Clinical Epidemiology, Cabrini Health, Melbourne, Australia.
• Cochrane Db Syst Rev. 2021 Sep 30; 9 (9): CD010951CD010951.

BackgroundAutologous whole blood or platelet-rich plasma (PRP) injections are commonly used to treat lateral elbow pain (also known as tennis elbow or lateral epicondylitis or epicondylalgia). Based on animal models and observational studies, these injections may modulate tendon injury healing, but randomised controlled trials have reported inconsistent results regarding benefit for people with lateral elbow pain.ObjectivesTo review current evidence on the benefit and safety of autologous whole blood or platelet-rich plasma (PRP) injection for treatment of people with lateral elbow pain.Search MethodsWe searched CENTRAL, MEDLINE, and Embase for published trials, and Clinicaltrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal for ongoing trials, on 18 September 2020.Selection CriteriaWe included all randomised controlled trials (RCTs) and quasi-RCTs comparing autologous whole blood or PRP injection therapy to another therapy (placebo or active treatment, including non-pharmacological therapies, and comparison between PRP and autologous blood) for lateral elbow pain. The primary comparison was PRP versus placebo. Major outcomes were pain relief (≥ 30% or ≥ 50%), mean pain, mean function, treatment success, quality of life, withdrawal due to adverse events, and adverse events; the primary time point was three months.Data Collection And AnalysisWe used standard methodological procedures expected by Cochrane.Main ResultsWe included 32 studies with 2337 participants; 56% of participants were female, mean age varied between 36 and 53 years, and mean duration of symptoms ranged from 1 to 22 months. Seven trials had three intervention arms. Ten trials compared autologous blood or PRP injection to placebo injection (primary comparison). Fifteen trials compared autologous blood or PRP injection to glucocorticoid injection. Four studies compared autologous blood to PRP. Two trials compared autologous blood or PRP injection plus tennis elbow strap and exercise versus tennis elbow strap and exercise alone. Two trials compared PRP injection to surgery, and one trial compared PRP injection and dry needling to dry needling alone. Other comparisons include autologous blood versus extracorporeal shock wave therapy; PRP versus arthroscopic surgery; PRP versus laser; and autologous blood versus polidocanol. Most studies were at risk of selection, performance, and detection biases, mainly due to inadequate allocation concealment and lack of participant blinding. We found moderate-certainty evidence (downgraded for bias) to show that autologous blood or PRP injection probably does not provide clinically significant improvement in pain or function compared with placebo injection at three months. Further, low-certainty evidence (downgraded for bias and imprecision) suggests that PRP may not increase risk for adverse events. We are uncertain whether autologous blood or PRP injection improves treatment success (downgraded for bias, imprecision, and indirectness) or withdrawals due to adverse events (downgraded for bias and twice for imprecision). No studies measured health-related quality of life, and no studies reported pain relief (> 30% or 50%) at three months. At three months, mean pain was 3.7 points (0 to 10; 0 is best) with placebo and 0.16 points better (95% confidence interval (CI) 0.60 better to 0.29 worse; 8 studies, 523 participants) with autologous blood or PRP injection, for absolute improvement of 1.6% better (6% better to 3% worse). At three months, mean function was 27.5 points (0 to 100; 0 is best) with placebo and 1.86 points better (95% CI 4.9 better to 1.25 worse; 8 studies, 502 participants) with autologous blood or PRP injection, for absolute benefit of 1.9% (5% better to 1% worse), and treatment success was 121 out of 185 (65%) with placebo versus 125 out of 187 (67%) with autologous blood or PRP injection (risk ratio (RR) 1.00; 95% CI 0.83 to 1.19; 4 studies, 372 participants), for absolute improvement of 0% (11.1% lower to 12.4% higher). Regarding harm, we found very low-certainty evidence to suggest that we are uncertain whether withdrawal rates due to adverse events differed. Low-certainty evidence suggests that autologous blood or PRP injection may not increase adverse events compared with placebo injection. Withdrawal due to adverse events occurred in 3 out of 39 (8%) participants treated with placebo versus 1 out of 41 (2%) treated with autologous blood or PRP injection (RR 0.32, 95% CI 0.03 to 2.92; 1 study), for an absolute difference of 5.2% fewer (7.5% fewer to 14.8% more). Adverse event rates were 35 out of 208 (17%) with placebo versus 41 out of 217 (19%) with autologous blood or PRP injection (RR 1.14, 95% CI 0.76 to 1.72; 5 studies; 425 participants), for an absolute difference of 2.4% more (4% fewer to 12% more). At six and twelve months, no clinically important benefit for mean pain or function was observed with autologous blood or PRP injection compared with placebo injection.Authors' ConclusionsData in this review do not support the use of autologous blood or PRP injection for treatment of lateral elbow pain. These injections probably provide little or no clinically important benefit for pain or function (moderate-certainty evidence), and it is uncertain (very low-certainty evidence) whether they improve treatment success and pain relief > 50%, or increase withdrawal due to adverse events. Although risk for harm may not be increased compared with placebo injection (low-certainty evidence), injection therapies cause pain and carry a small risk of infection. With no evidence of benefit, the costs and risks are not justified.Copyright © 2021 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

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