Literature reviewThe clinical impact of platelet-rich plasma on tendinopathy compared to placebo or dry needling injections: A meta-analysis
Introduction
Tendinopathy is a common orthopaedic problem that includes tendinitis, paratenonitis and tendinosis (Khan, Cook, Bonar, Harcourt, & Astrom, 1999). It is characterized by chronic pain, functional deterioration and tendon thickening. Both intrinsic and extrinsic factors have been implicated in the etiology of tendinopathy (Riley, 2004). The histopathology of tendinopathy reveals the absence or minimal presence of inflammatory cells, which has been confirmed by gene array studies (Alfredson et al., 2003, Ireland et al., 2001). Tendinopathy is characterized by increased mucoid substance, intra-tendinous degeneration, and collagen disorganization (Khan et al., 1999). In some cases, a 10- to 20-fold increase in calcium concentration may be detected (Kannus, 2000).
There are a variety of approaches for treating tendinopathy, with traditional methods (i.e., non-steroidal anti-inflammatory drugs and activity modification) still advocated as first-line management (Andres & Murrell, 2008). In cases where conservative treatments fail, surgical consultation is suggested.
In addition to the well-established conservative therapies, many investigational injectable treatments have been developed. Ultrasound- (US) guided dry needling intervention, and US-guided platelet-rich plasma (PRP) injections are two injectable treatments. PRP is defined as the volume of autologous plasma that has a platelet concentration above baseline (Marx, 2001). The dry needling technique, also known as peppering, consists of multiple tendon perforations without injecting any substances.
PRP, placebo and dry needling injections cause bleeding in the tendon, which can increase inflammation and induce the release of beneficial growth factors. This stimulates tendon healing (Filardo et al., 2010, Mishra et al., 2012). Consequently, it is thought that the needling of a tendon, with or without injecting any substances, exerts a positive clinical impact on rehabilitation (Dommerholt, 2011, Krey et al., 2015, Nagraba et al., 2013). The use of high platelet concentrations in PRP, results in the release of significantly greater amounts of beneficial growth factors than that released by any type of needling. Moreover, the concentration of growth factors increases linearly with increasing platelet number (Eppley et al., 2004, Marx, 2001). Nevertheless, it is evident that PRP with significantly high platelet concentrations does not further increase tendon rehabilitation (Marx, 2001, Rughetti et al., 2008). Considering this, we hypothesized that the clinical effect of PRP on tendinopathy would be greater than that of placebo or dry needling.
The purpose of this meta-analysis was to compare the clinical impact of PRP with that of placebo or dry needling on adults with tendinopathy. The primary outcome measure was pain intensity at two or three and six months after the initial intervention. The secondary outcome was functional disability at three months after the initial treatment.
Section snippets
Methods
The review was registered with PROSPERO (CRD42014010003) and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed (Liberati et al., 2009).
Results
The literature search retrieved 1565 potentially relevant studies. Duplicates were removed and the remaining 1205 studies were screened according to the information provided in their title and abstract. After the exclusion of 1179 records, the remaining 26 articles were eligible for full-text assessment. One of the retrieved trials was not randomized (Mishra & Pavelko, 2006). Two trials presented the results of the same study with different follow-up measurements (de Vos, Weir, Tol, Verhaar,
Discussion
Five RCTs comparing the impact of PRP with that of placebo or dry needling on tendinopathy were identified. There was no significant statistical heterogeneity in the overall results of the present quantitative synthesis. Therefore, there was no significant variability in the intervention effects that were evaluated in the included RCTs (Higgins & Green, 2011). At the first primary outcome time point and at the secondary outcome time point, pooled analysis indicated statistically significant
Conclusions
In conclusion, PRP injections did not provide significantly greater clinical relief compared to placebo or dry needling for the treatment of tendinopathy at a six-month follow-up. However, there was a marginal clinical advantage in patients who suffered from rotator cuff tendinopathy. The latter marginal clinical superiority should be further investigated in large-scale RCTs. Future research should determine the impact of potential sources of clinical diversity on the rehabilitation of
Conflict of interests
None declared.
Funding
This study was supported by the project “IKY scholarships” (State Scholarships Foundation) from resources of Operational Programme “Education and lifelong learning” of the European Social Fund (USF) of (NSRF), 2007–2013.
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