Like all things, research can be smartly constructed or just plain dumb. A recent study of platelet-rich plasma (PRP) used to treat ankle sprains falls into the latter category.
The platelets in platelet-rich plasma (PRP) come from whole blood and are concentrated in serum. PRP should work by stimulating local stem cells and other cells to repair the body faster or to prompt repair in an area that was unable to repair itself. Ankle sprains occur when the ankle ligaments are stretched, and most ankle sprains heal on their own. When they don’t, it’s usually because too much ligament damage has occurred for the body to be able to completely heal the torn ligaments.
The study reported June 2, 2015, in The Journal of Emergency Medicine looks great on the surface. It’s randomized and double blind, but it doesn’t take long to see how the authors doomed it to failure before ever injecting the first patient. The hypothesis seemed reasonable enough—a PRP shot in the emergency room for patients who look like they have a more severe ankle sprain will translate into faster healing of the ligament. Not a bad concept, although the first serious issue occurs with the study’s control group.
A control group in a study is one that isn’t treated or that is given a treatment known not to work. This allows researchers to compare the treatment being tested to no treatment. A control group expected to heal presents a major problem for researchers. This is why many pain researchers study chronic injuries, which rarely recover on their own. Since acute ankle sprains tend to get better without any care, choosing acute ankle injuries to study almost guarantees that the group without treatment will do well. In effect, if the study is a horse race between the control group and the group being given PRP, the control group began the race with a huge head start. If the authors would have waited a few weeks to inject only those patients who weren’t recovering, the horse race would have been more evenly matched—and the study likely would have reported different results.
That first flaw in the study’s control group might be chalked up to hubris, or to a slip of common sense, or maybe the study was conducted by emergency room doctors who see patients only right after injury. The second major flaw in the study was inexcusable. For some time it’s been known that the anesthetic Marcaine kills stem cells and other cells. The authors of this study injected PRP along with lidocaine (which hurts stem cells) and Marcaine (which kills both stem cells and tendon cells and ligament cells. This last blunder likely insured that the cells the PRP was supposed to stimulate would be dead or dying by the time the PRP reached them to do its job. This decision virtually ensured that the PRP group would do poorly.
The study concluded that PRP didn’t help ankle sprains heal more quickly than a saline shot used with the control group. While all research is valuable in some respect, the study was a waste of money. Because the authors chose to inject toxic anesthetics with PRP, it’s unknown whether the PRP would have helped these acute ankle sprains if used alone. More concerning for patients is that this study was approved by a major manufacturer of PRP machines and by many smart physicians who should have known better. How many patients are out there receiving PRP shots with anesthetics known to be toxic to stem cells and other cells? That this study exists strongly suggests there are countless patients obtaining ineffective PRP shots from doctors who haven’t gotten the memo that certain anesthetics kill cells.
“Dumb and Dumber: New PRP Ankle Sprain Research” first appeared as a post on the Regenexx blog.