Sweat Science Platelet-Rich Plasma for Knee Osteoarthritis A new study shows promise, as long as you dont look too closely. By Alex Hutchinson Published February 22, 2013 kneearthritis Remember a few years ago when platelet-rich plasma (PRP) injections were the hottest thing in sports medicine? The evidence that PRP could help tendon injuries was preliminary at best, but Tiger Woods and a ton of other top athletes were doing it, so it was only a matter of time before better studies emerged. Except that they didnt – study after study produced results that were ambiguous at best. The hype has died down a bit, but my sense is that PRP (which involves removing some of your blood, spinning it to concentrate the purported healing power of the platelets, then reinjecting it at the injury site) remains quietly popular. The most recent PRP study I saw tested its potential to treat knee osteoarthritis, and the press release was very encouraging: A study by researchers from Hospital for Special Surgery has shown that platelet-rich plasma (PRP) holds great promise for treating patients with knee osteoarthritis. The treatment improved pain and function, and in up to 73% of patients, appeared to delay the progression of osteoarthritis, which is a progressive disease... This is a very positive study, said Brian Halpern, M.D., chief of the Primary Care Sports Medicine Service at Hospital for Special Surgery, New York City, and lead author of the study. What I found most interesting was that the study used objective outcomes to measure success, rather than just asking the patients whether they felt better. Again from the press release: The problem with a lot of the PRP studies is that most people have just used subjective outcome instruments, such as pain and function scores, said Hollis Potter, M.D., chief of the Division of Magnetic Resonance Imaging at Hospital for Special Surgery, another author of the study. But even when patients are blinded, they know there has been some treatment, so there is often some bias interjected into those types of studies. When you add MRI assessment, it shows you the status of the disease at that time, regardless of whether the patient is symptomatic or asymptomatic... This sounded very promising, so I dug up the full paper from the Clinical Journal of Sports Medicine to check it out. Ill leave aside the subjective measures of pain and stiffness and so on, because this was an unblinded case series with no control group – based on the results produced even by placebo injections in other PRP studies, I dont think theres much useful information we can gather from those measures. But what about the objective MRI data? In this case, the images were analyzed and scored by radiologists who were blinded as to whether the images were before or after, which is great. While its a little ambiguous, it appears 12 patients (a total of 15 knees) were assessed with MRI. The headline number that osteoarthritis progression was delayed in 73% of patients seems to come from the fact that 11 of the 15 knees showed no significant worsening 12 months after the PRP treatment. Now, the crucial question is: under normal circumstances (i.e. if theyd had a control group), what sort of changes would they have expected to see? Heres what they say: This is in contrast to some longitudinal studies that suggest an annual decrease of up to 4% to 6% of cartilage volume in knee osteoarthritis compartments. If you follow the references they cite for this statement, you find this paper (full text freely available here). Sure enough, they report that after 12 months, they observed a decrease in cartilage volume of 3.7 +/- 3.0% for global cartilage and -5.5 +/- 4.3% for the medial compartment [of the knee joint]. Youll notice that the standard deviation of these measurements is almost as big the measurement itself, which means you need a reasonably large sample size to observe the effect (the original study had 102 subjects). So what were the actual numbers (and standard deviations) in the PRP study? As far as I can tell, they dont report them anywhere! They just say that the measurements did not reach statistical significance. Does this mean they observed a volume change of -0.0 +/ 0.5%? Or -3.0 +/- 6.0%? I have no idea. Why does this matter? Theres a big difference between failing to observe a statistically significant change and successfully showing that a parameter doesnt change (i.e. that the progression of the disease is delayed). Doing the latter was always going to be extremely difficult with just 12 patients – but not publishing the results makes it impossible to judge whether they did. (On the other hand, they did include a large table with detailed values for seven different subjective measures, with a total of 70 different numbers). As the press release stated, The problem with a lot of the PRP studies is that most people have just used subjective outcome instruments. This one didnt, but if it doesnt reveal the results of the objective measures, then whats the difference? Tags: Osteoarthritis To make a payment, cancel or renew your subscription for Runners World, contact customer service at: 400 South Tenth Street · Emmaus, PA 18098-0099 (800) 816-4735 · customerservice.runnersworld rwdcustserv@cdsfulfillment Runners World ©2015, Rodale Inc. All rights reserved.
Posted on: Sun, 25 Jan 2015 14:37:44 +0000
Recently Viewed Topics
© 2015