Dumb and Dumber: New PRP Ankle Sprain Research
As you might be able to tell from reading these blogs, I love research. I read it voraciously, conduct studies, and publish it. But research, like all things can be smartly constructed or just plain dumb. I’d like to highlight a PRP ankle sprain study this morning that’s in the latter category.
PRP stands for platelet rich plasma, where platelets from whole blood are concentrated in serum. It should work by stimulating local stem cells and other cells to repair things faster or to prompt repair in an area that was unable to repair itself. Ankle sprains occur when the ankle ligaments are stretched, with most healing on their own. When they don’t heal, usually too much ligament damage has occurred for the body to be able to completely heal the micro and/or macro tears in the ligaments.
The new study looks great on the surface in that it’s randomized and double blinded, 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 department 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 with the study is with it’s “control group”.
A control group in a study is one that isn’t treated or is treated with a treatment that we know won’t work so that the researchers can compare the treatment being tested to no treatment. However, what if your control group will also recover from the illness? This becomes a big issue when studying acute injuries that are expected to heal. This is why many researchers studying painful conditions chose chronic injuries, as they don’t usually recover on their own. Since acute ankle sprains tend to get better without care, choosing acute ankle injuries to study almost guarantees that the group without treatment will do pretty well. So in effect, if the study is a horse race between the control group and the PRP group, the control group began the race with a huge head start. If the authors would have waited a few weeks to only inject those patients that weren’t recovering, the horse race would have been more evenly matched and the study would have likely seen different results.
If you can chalk the first study flaw of treating acute ankle sprains up to hubris and a slip of common sense (or maybe that the study was conducted by ER doctors who only see the patient right after the injury), the second major study flaw was inexcusable in how it totally wasted the significant money spent on this study. We’ve known for some time that the anesthetic Marcaine (bupivicaine) kills stem cells as well as other cells quite dead. The authors of this study, for some unknown reason, chose to inject PRP plus lidocaine (which hurts stem cells) and Marcaine (which kills stem cells as well as tendon/ligament cells)! This last blunder likely insured that the cells the PRP were supposed to stimulate would be dead or dying by the time the PRP got there to do its job. Hence, more than any other thing they could have done, based on the research that exists, this decision virtually insured that the PRP group would do poorly. In essence, in our horse race, they set a stick of dynamite on the back of the PRP horse set to go off in the beginning of the race!
The upshot? The study of course concluded that PRP didn’t help ankle sprains heal more quickly than a saline shot control. At the end of the day, while all research is valuable in some respect, the study was a waste of money when looking at PRP effects. Because the authors chose to inject toxic anesthetics with PRP, we have no idea if the PRP would have helped these acute ankle sprains if used alone. More concerning for patients is that this study was actually approved by a major PRP machine manufacturer and went through many smart physicians who should have known better. How many patients are out there getting PRP shots with anesthetics we know are toxic to stem cells and other cells? The fact that this study exists, means to me that there are countless patients getting ineffective PRP shots from docs who haven’t gotten the memo that certain anesthetics kill cells.