According to the authors of this review and update on platelet-rich plasma (PRP), there are now 1000s of articles published on the topic. Yet for all that research, we still don't know if platelet-rich plasma treatment is really the way to go for tendon (or other soft tissue and bone) healing.
Let's take a look at what this review was able to uncover about platelet-rich plasma. Here's a quick review for those who don't know what it is. Platelet-rich plasma (PRP) refers to a sample of serum (blood) plasma that has as much as four times more than the normal amount of platelets. This treatment enhances the body’s natural ability to heal itself and is used to improve healing and shorten recovery time from acute and chronic soft tissue injuries.
It has been used for years after plastic surgery and surgery on the mouth, jaw, and neck. It seems to promote bone graft healing. Researchers have found a way to combine this substance with other chemicals to make it into a putty or gel that can be painted on a surgical site to speed up healing.
Blood injection therapy of this type has been used for knee osteoarthritis, degenerative cartilage, spinal fusion, bone fractures that don’t heal, and poor wound healing. This treatment technique is fairly new in the sports medicine treatment of tendon, cartilage, and ligament problems, but gaining popularity quickly.
Despite the many publications on the topic of PRP, it's still unclear if it works, why it works, or how to prepare the product for use with any of these problems. That's where this article comes in. The authors ask and answer these questions:
Should white blood cells be part of the PRP solution?
- What is the optimal platelet concentration for healing?
- How often should the injections be given for the best results?
- How does the use of PRP compare with cortisone or hyaluronic acid (HA) injections?
- The PRP solution is usually made without any of the white blood cell components. The reason for this is that white blood cells activate too much of an inflammatory process.
- The net effect is actually detrimental to tissue healing. Platelets with their natural growth factors stimulate a healthier healing response with less scar tissue compared with leukocytes or other types of white blood cells.
There are some positive effects of white blood cells such as the breakdown and removal of dead tissue that might be delaying healing and recovery. White blood cells also help prevent infection. Platelet-rich plasma (PRP) does not have a direct antimicrobial effect like white blood cells do, but PRP does activate chemical that help clean up dead or dying cells at an injury site.
Whether to use low, moderate, or high concentrations of PRP remains a point of debate. It is difficult to actually measure how many platelets are activated and delivered to damaged tissue. There is a concern that too much concentration would oversaturate the area and cause problems. And there is some evidence that high platelet levels create a threshold effect. This means that after a certain number of platelets (PRP concentration level), the effect is actually negative rather than positive.
Of course, too little concentration may not have the desired healing response. It is a bit like the story of Goldilocks and the three bears because it takes time to find out what is "just right." Studies comparing the effects of low to moderate to high concentrations of PRP remain at the stage of animal studies. Future studies with humans are still needed in this area.
Now, what about the frequency of injections? Are the results of multiple injections just as good as one injection? In most animal and human studies, only one injection has been used. The focus has been more on the timing of the injection. Some reports published showed better results when PRP injections were given during the first seven days after injury. So the chase has been on to find the ideal window for treatment by PRP injection. It may turn out that the timing is different for acute versus chronic tissue damage.
And finally, how do the results of PRP injections compare with the more traditional steroid or hyaluronic acid injections given for joint arthritis or chronic tendinitis. There are two key findings when comparing PRP to cortisone injections.
First, PRP seems to reduce pain and improve function better than steroid injections. Those findings were consistent after one-year and after two-year follow-up checks. And second, patients with chronic tennis elbow who did not benefit at all from steroid injection(s) did experience improvements in pain and function when treated with PRP instead.
As for comparing PRP to hyaluronic acid (HA) for knee osteoarthritis, there has been one study that showed a 33 per cent improvement in pain and function for patients receiving PRP injections compared with a 10 per cent improvement for the group who received an HA injection. In other studies comparing the two, the results of PRP were greater and longer lasting than treatment with HA.
In conclusion, no one is ready to drop the use of platelet-rich plasma without further exploring its benefits. There haven't been any adverse effects in using it so there's no apparent danger. Just as many people who are aided by this treatment seem to receive no benefit at all. So until scientists can iron out all the who, what, when, where, and hows of this treatment, expect to see a continuation of ongoing studies focused on platelet-rich plasma.
Reference: Jeffrey M. DeLong, et al. Sports Medicine. Update on Platelet-Rich Plasma. In Current Orthopaedic Practice. November/December 2011. Vol. 22. No. 6. Pp. 514-523.