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Robert J. de Vos, MD; et al., Platelet-Rich Plasma Injection for Chronic Achilles Tendinopathy, JAMA. 2010;303(2):144-149. doi: 10.1001/jama.2009.1986
This study was moderate in size with 27 in the PRP group and 27 in the saline group and good followup to data analysis point occurred without data loss. The VISA-A was used as the primary clinical measure. The VISA-A score is a measure specifically of Achilles pain and function. The authors, (despite decades of research showing that injection is not a placebo intervention), describe subcutaneous injection of marcaine 0.5%, followed by intratendinous needling with saline in 5 separate aliquots, as a "placebo" intervention. The authors unfortunately missed an excellent opportunity to have an exercise control by not assigning a group of patients to exercise only. They also did not have a group with injection only. (See Yelland et al 2009 study on Achilles Tendinopathy for a better study design)
A review of the two groups characteristics before treatment revealed that the duration of symptoms was 10 weeks longer in the PRP group (36 vs 26), and that only 1/4 as many in the PRP group were able to play sport unchanged (9% versus 37%). Despite that, 10% more in the PRP group were playing their desired sport at the 6 month period. (78% versus 67%).
So, essentially, this study was a treatment comparison study, not a placebo study, and had potentially dissimilar groups. Nevertheless, this study does make a statement about the potential limitations of any one injectant over another in conditions unless the pathology is more fully understood. In this case, in those doing eccentric lengthening exercises, a single injection session with PRP appears to be no more efficacious than saline injection.
Brian Shiple commented on the major problems with this study in a very useful way. A few thoughts of his are offered here:
Comment #1: "In our experience, the two pathologies that are the most recalcitrant to treatment with PRP are chondromalacia patellae and Achilles tendinopathy. In over two years of doing PRP, we have NEVER had a patient with chronic Achilles tendinopathy heal after only one treatment. It typically takes 3–4 treatments and 6 months or more, combined with eccentric exercise. And even with that, the success rate is much lower than with epicondylosis, patellar tendon, etc."
Note that basic research means that you use a treatment approach that you expect to be effective. What Dr. Shiple is saying is that this study used completely in appropriate dosing to try to prove something. It is like studying defibrillation at 1/10th normal voltage versus pounding on the chest and finding that neither one in the patient with a shockable rhythm cardiac arrest.
Comment #2: "Did these patients have paratenon disease either on exam or by U/S? If they did and this was not treated, they don't get better in our experience. Some authors have described the achilles tendon disease as acutally 4 separate and distinctly different disease states: 1) mid portion tendinosis; 2) mid portion paratenon tendinitis/osis; 3) mid portion acute complete tear; 4) mid portion partial tears with coexisting tendinosis. And then there is the insertional tendon issues which behave differently than the mid portion ones. Plus you can have a combination of these conditions above. So if they had 60% of these cases with tendinosis with paratenon disease and the paratenon was not treated you would have 60% doing equally poorly."
Achilles studies need to be more precise about what they are actually studying as different conditions respond differently and this affects outcomes and group comparisons a great deal.
The complete study for Platelet-Rich Plasma Injection Versus Saline injection, including abstract, is available here.