In the last few years, scientists have discovered that injecting platelets from blood into damaged tendons helps them heal faster and better. This has been good news for professional athletes who are eager to get back to work on the playing field.
Platelet-rich plasma (PRP) (also known as blood injection therapy) is a medical treatment being used for a wide range of musculoskeletal problems. Platelet-rich plasma refers to a sample of serum (blood) plasma that has much more than the normal amount of platelets. This treatment enhances the body’s natural ability to heal itself. It is used to improve healing and shorten recovery time from acute and chronic soft tissue injuries.
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 musculoskeletal problems, but gaining popularity quickly.
In a surprising twist on the subject, researchers in Sweden reported on their not-so-successful results. They used platelet-rich plasma (PRP) injections in the Achilles tendon of 16 patients. They were not all professional athletes but the injury did occur while engaged in recreational sports.
Results were compared to another group of patients who also had a recent Achilles tendon rupture (within three days). The second group was the control group -- they did not have the PRP injection. Patients in both groups ranged in age from 18 to 60 and were in good general health.
The Achilles tendon was chosen for several reasons. It is a commonly injured area in athletes as well as in others who do not participate in sports. The tendon does not heal well -- it takes a long time to recover from an Achilles tendon rupture. And the risk of rupturing it again is fairly high. For all those reasons, finding a more effective treatment with better long-term results would be a great boon to all.
This group of researchers has been studying tendon healing for a long time. They have developed a way to measure tendon elasticity. In this study, they measured both tendon elasticity and function at regular intervals after PRP injection. Follow-up was for a full year.
Before the procedure was done, everyone donated a unit of blood to be used for themselves. The lab removed platelets from the blood and the surgeon injected a solution that was 10 times higher in platelets than regular blood. The tendon was repaired surgically and then the PRP was injected into the area of rupture.
Postoperative treatment included a short-leg cast with the foot in a slightly plantar-flexed position (toes pointed down). This position takes pressure and load off the healing Achilles tendon. It is a standard post-operative treatment after surgery to repair ruptured. After three and a half weeks, the foot and ankle were re-cast in a more neutral position.
At the end of seven weeks post-op, no further casting was needed. Patients wore shoes with a slight heel (again to avoid overstretching the healing tendon) for a month. During all this time, they were allowed to put as much weight on the leg and foot as they could comfortably tolerate. Patients in both groups were enrolled in a typical Physical Therapy rehab program.
The authors were surprised to find no differences between the two groups. The PRP group did not heal faster or have a stronger Achilles tendon at any point in the follow-up. In fact, if anything, the PRP group had slightly worse functional results. Functional refers to their ankle motion, ability to rise up on toes, and jump vertically. The PRP group did not see themselves as limited in daily activities but there is still a concern that their risk of re-injury is greater than normal.
Taking a look back on how the experiment was done, the authors could not find any obvious reason why the PRP group did not have better results than the control group. The preparation of the injection was followed according to standard protocols used in other studies. The platelet concentration was higher than reported in other studies (17 times normal blood compared to three times higher in another similar study).
They suggested that perhaps using tendon elasticity as a measure of "success" may not be correct. Their basis for thinking elasticity was an accurate measure comes from the belief that healing tendons heal in an elastic manner. Maybe there is an error in this assumption. Another possibility is the concentration of platelets. Is it possible that too high a concentration yields worse results than lower amounts?
This was the first study to treat Achilles tendon ruptures with PRP compared with a control group. More studies will be needed to clear up the mystery of why Achilles tendon healing was not enhanced.
Reference: Thorsten Schepull, MD, et al. Autologous Platelets Have No Effect on the Healing of Human Achilles Tendon Ruptures. In The American Journal of Sports Medicine. January 2011. Vol. 39. No. 1. Pp. 38-47.