Sometimes a word has different meanings in different scientific communities. To a physicist, plasma is the fourth state of matter (solid, liquid, gas, plasma, right?!), but in the health sciences, plasma refers to the fluid portion of blood.
When you accidentally cut your finger while sawing away on a loaf of Kevlar-crusted artisan bread, 55% of what you see seeping into the kitchen towel is plasma. The other 45% is almost entirely red blood cells, which shuttle oxygen around the body. A very small amount is composed of white blood cells — the mainstay of the immune system — and another group of cells called platelets.
When a blood vessel is injured and begins to bleed, platelets are the cells that quickly stick to the area of injury — and to each other — to form a patch that plugs the leak in the artery. As part of their first responder role, platelets also release a cascade of growth factors that stimulate tissue regeneration and healing in the injured area.
If platelet-rich plasma (PRP) is good for multimillion-dollar athletes, why wouldn’t it work in regular folks?
The regenerative, healing property of platelets is what sparked the idea of injecting them into injured tissues to try to speed recovery. Platelet injections — better known as platelet-rich plasma (PRP) injections — have been used in multiple fields of medicine. However, they have been most widely used in orthopedics and sports medicine to treat musculoskeletal injuries — especially those involving the knee and shoulder but also those in the ankle, foot and elbow. PRP is being injected into damaged muscles, tendons and ligaments, and it is also being used to try to rehabilitate the rubbery cartilage that cushions joints. Cartilage breakdown is what leads to osteoarthritis.
Although PRP injections first came to public light as a treatment for injured professional athletes, the injections are now being used to treat the battered and banged-up proletariat. And not just in orthopedic clinics but also in stand-alone clinics that describe themselves as offering regenerative medicine. These clinics often avoid using the term “PRP” or “injections,” and instead describe the treatment in a somewhat cryptic code as a drug-free, minimally invasive, nonsurgical alternative that takes advantage of the body’s natural capabilities to stimulate the restoration of damaged tissue.
I scoured the website of a high-profile national chain of regenerative medicine clinics and could not find a specific reference to PRP or how it is performed. Maybe that’s to avoid having potential customers imagine someone putting a needle into their already painful joints or tendons. (“But doctor, isn’t that going to hurt, and couldn’t that make things worse?”)
Or it may have to do with avoiding the question, “How much will that cost?” Few insurance plans cover PRP, and the cost can range anywhere from $300 to $2,500 depending on who does it and how many treatments are performed.
What, exactly, is a PRP injection?
PRP is created when whole blood is removed from a person’s vein and then sent to a lab where a machine like the Plasmaticizer 8000 is used to filter out most of the red and white blood cells, leaving behind plasma with a high concentration of platelets.
It’s a quick process. The blood can be drawn, concentrated and injected as PRP during the same clinic appointment, often within an hour. Symptom relief, in contrast, may take considerably longer. A PRP treatment is typically preceded by an injection of local anesthesia, but once that’s worn off, it’s possible that the pain in the injured area might increase for a week or two before any improvement.
So does it work?
It depends on who you ask: the science or the testimonials. The testimonials, of course, are giving a resounding yes. But the science is less enthusiastic. If you read the American Academy of Orthopaedic Surgeons (AAOS) website, you’ll see it isn’t exactly trumpeting the benefits of PRP. It’s more of a cautious woodwind sound, noting that lingering questions remain, and that “although it is not exactly clear how PRP works … PRP may potentially speed up the healing process” (emphasis mine).
The AAOS website contends that PRP is effective for low to moderate grade knee osteoarthritis, and for certain chronic tendon injuries. It recommends more research to see if PRP therapy is truly effective for other conditions.
To that end, in 2021 three high-quality clinical trials published in the Journal of the American Medical Association (JAMA) gave PRP a bum knee. The studies revealed PRP to be no more effective than an injection of placebo (saline solution) for osteoarthritis of the knee or ankle or for Achille’s tendonitis. The results rekindled the debate about PRP’s effectiveness. Noting that the bulk of studies using PRP for knee pain lean toward a benefit, most orthopedists continue to view PRP as a reasonable management tool for knee pain.
An editorial accompanying the three JAMA studies noted that many previous trials did not compare PRP with placebo injections. That’s particularly important in a trial of an injected therapy because injections have a considerable placebo effect and can improve people’s pain ratings by 1.8 on a 10-point pain scale. People expect big things (pain relief) from big things (a needle disappearing into the knee).
What’s hobbling PRP research the most is what researchers call heterogeneity, and what nonspecialists call comparing apples to oranges. In a clinical trial involving an oral drug, every pill carries the exact same amount of drug. But in the case of PRP, the many different machines being used to transform whole blood into PRP produce many different PRP products. These end products can vary in important ways, including the concentration of platelets and how many white blood cells might have sneaked in. For PRP promoters, a negative study can be explained away by saying that the particular PRP machine used in the trial produced the wrong stuff rather than the right stuff.
Where next for the future of PRP?
It’s not easy to rain on the parade of a therapy that has the potential to relieve the pain and disability of millions. For all people, life takes its toll in a series of dings and dents that eventually add up, even if they’re not retired celebrity athletes. The hope is that future research will provide more and better studies to determine whether the regenerative power of platelets can be if not a Fountain of Youth, then at least a small dripping spigot of youth, or maybe even a refreshing mister of vitality.
PRP is the most widely used and recognized form of what are often referred to as orthobiologics, which also include infusions of stem cells and adipose (fat) cells.
According to Shane A. Shapiro, M.D., medical director for Mayo Clinic’s Regenerative Medicine Therapeutics Program, the work on orthobiologics is just getting started.
“We recognize that our first-generation orthobiologics just scratch the surface in terms of using cells to treat orthopedic disease. The future of orthopedic cell therapy is going to require much more sophisticated versions of these cell therapies,” Dr. Shapiro points out. “Treatment using orthobiologics that’s not based in sound orthopedic science is not likely to help people. Mayo Clinic is committed to advancing the science of regenerative medicine, to harness its potential and to provide evidence-based treatments for patients.”
Things to consider when considering PRP
The practitioner’s experience. Ask your practitioner when they began administering PRP and how many PRP injections they’ve performed. A practitioner who is a medical doctor is likely to have more overall medical experience than other types of practitioners.
Honesty of the treatment plan. Did the PRP discussion feel more like a sales pitch than a recovery option? Did your care team discuss treatment options other than PRP? In general, approach PRP-heavy solo practitioners with caution.
How many and how much. Ask how many injections the practitioner thinks you’ll need, and what that will cost you. In addition, ask what’s needed in terms of recovery, physical restrictions and therapy other than PRP.
Chances of improvement. Ask whether your practitioner can quantify how previous patients have responded to PRP injections similar to the ones you’re considering. Is the practitioner involved in any clinical trials to help move the science along?
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