Sandra Yin

July 18, 2012

July 18, 2012 (Baltimore, Maryland) — Platelet-rich plasma injections can benefit patients with cartilage degeneration and early osteoarthritis (OA) of the knee, according to preliminary findings from a randomized controlled study presented here at the American Orthopaedic Society for Sports Medicine (AOSSM) 2012 Annual Meeting.

In patients with minimal OA, you see that platelet-rich plasma (PRP) works better than hyaluronic acid, said lead investigator Elizaveta Kon, MD, from the Rizzoli Orthopedic Institute in Bologna, Italy. "If you look at the improvement after 2 months and then after 6 months," she said, "you can see the improvement that is greater [with the respective treatments] in patients." Preliminary findings showed that patients with low degeneration of the knee who are treated with PRP can still see improvement up to 6 months and 12 months later, whereas the patients receiving hyaluronic acid do not.

However, the difference vanishes when you look at a general population of patients with severe OA of the knee, Dr. Kon noted. In those cases, PRP and hyaluronic acid deliver comparable results.

The use of PRP, or autologous platelets, can be a source of growth factors for healing and tissue regeneration. It is fashionable, much hyped, and very controversial, Dr. Kon noted. It has been used to speed healing after dental implant surgery and to treat everything from wrinkles to baldness. Although some consider it a "holy water" that treats everything, Dr. Kon warned that few clinical studies actually support the use of PRP in many sports medicine applications in which it is used.

In her presentation, Dr. Kon discussed findings from 2 studies she conducted. Findings from a comparative study of 72 patients revealed that patients with cartilage degeneration and early OA who began receiving PRP fared slightly better at 6 months, whereas those receiving hyaluronic acid did not. Young patients seemed to benefit more from PRP than from hyaluronic acid, but there was no significant difference between older patients in the 2 groups.

In a double-blind, randomized controlled trial of 200 patients, the researchers compared 109 patients (54 receiving PRP and 55 receiving hyaluronic acid) at 2, 6, and 12 months' follow-up.

To make the PRP used in the study, the Rizzoli lab took a 150-mL venous blood sample and ran it through a centrifuge twice. After platelet concentration, the total number of platelets in the PRP increased to 600% compared with whole blood. The 20 mL of PRP produced was divided into 4 vials of 5 mL each. One vial was used for quality control. The PRP was activated and frozen before use. It was then unfrozen and injected 3 times per week.

The only statistically significant difference, Dr. Kon noted, was that PRP created much more pain and swelling, especially pain the day after the injection, compared with hyaluronic acid. However, none of the patients treated experienced complications such as infection, deep vein thrombosis, or fever.

"PRP is a simple, low-cost, and minimally invasive approach to treat chondropathy and early osteoarthritis," the researchers wrote. "The clinical results of our study are encouraging and suggest this method may be used to treat the degenerative articular pathology of the knee, leading to results at least comparable with those of hyaluronic acid."

Researchers have yet to determine how PRP works, but Dr. Kon described it as a big cocktail of growth factors. Some factors are good for cartilage, but others are not. Likewise, some are good for tendons, but others are not. In the future, it will be possible to exclude certain factors from the formulation and create "a much more efficient PRP preparation," she said.

Session moderator Elizabeth Arendt, MD, professor and vice chair of the Department of Orthopaedic Surgery at the University of Minnesota in Minneapolis, emphasized the elegance of the study, which built on previous research that showed a huge PRP placebo effect.

The research was a randomized double-blind study with a good amount of built-in controls, she told Medscape Medical News. Although she described the results as promising, she echoed a point Dr. Kon made, saying that more study is needed to decode the science behind why growth factors work before taking the field to the next level.

However, Dr. Arendt moderated her enthusiasm, noting that researchers would need to follow the results out further before they could say something more definitive. The evidence shows that young patients in the PRP group continued to improve a little between follow-ups and that the patients receiving hyaluronic acid get a little worse. "That makes the study results a little stronger. You're seeing that at 6 months you didn't see as much of a diversion," she said. "At 12 months, you did see a little bit more. If they go on 18 months, 2 years, you might see more. We'll see."

Although she said nobody thinks the effects of hyaluronic acid last 2 years, she said the effects of PRP might last longer than any other current injections.

When asked whether PRP would be palliative only in the future, or whether it might stabilize cartilage or have an antidegenerative effect down the road, Dr. Kon declined to speculate.

"It's a very tough question," she said, noting that there has been much talk of using PRP for prevention in sports medicine. So far, however, no medical studies support its use as a preventive therapy.

The study's authors have disclosed no relevant financial relationships. Dr. Arendt consults with Tornier.

American Orthopaedic Society for Sports Medicine (AOSSM) 2012 Annual Meeting: Podium Abstract 36. Presented July 14, 2012.

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