Platelets are blood cells that are formed in the bone marrow. They contain packets of proteins that are responsible for clotting and for wound healing.
Once platelets are released into the bloodstream from the marrow, they have a circulating life span of about 7-10 days. When there is acute injury, platelets accumulate at the site. A sequence of events occurs with formation of a clot and then release of growth factors. These growth factors attract various other blood cells to the area. These other growth factors and cells assist in the healing process. In many instance, the addition of calcium chloride and human thrombin (Recothromb) has been used to stimulate the release of growth factors. While bovine thrombin has also been used, there have been reports of hypersensitivity reactions in a small number of patients.
Platelet-rich plasma, PRP, is a concentrate of whole blood that contains at least 1 million platelets per 6 cc's. Ideally, platelet concentrations in the 3-5 million range are better since higher concentration of platelets means more growth factors and theoretically faster healing.
So where has PRP been used? One of the early papers describing the utility of PRP was published by Mishra and Pavelko in the American Journal of Sports Medicine in 2006. They presented a non-randomized study of 20 patients with chronic lateral epicondylitis (tennis elbow). The patients were evaluated eight weeks after receiving their treatment and there was a 60 per cent improvement in the PRP treated group versus 16 per cent in the control group.
This treatment has also been studied for Achilles tendon problems. The results have been mixed. A Dutch study published in the Journal of the American Medical Association in 2010, involving 54 patients shown no statistical difference between the PRP treated group and the group treated with saline and exercise.
However, there has been criticism regarding the study design, and also there have been other studies reporting positive results with PRP with Achilles tendonitis.
Other conditions for which PRP has been used include patellar tendonitis ("jumper's knee"), rotator cuff tendonitis of the shoulder, plantar fasciitis, gluteus medius tendonitis of the hip, and even osteoarthritis.
When PRP is administrated it is done following a needle tenotomy- a procedure where a small needle is introduced into the area of tendon damage using ultrasound guidance. The needle is used to make small holes in the diseased tendon in order to create an acute injury. This acute injury is what stimulates an acute inflammatory response which causes the platelets to release their healing and growth factors.
Contraindications to the use of PRP include active infection, malignancy, bleeding disorders, and the use of strong anticoagulant drugs ("blood thinners").
One area of concern is the use of human growth hormone in conjunction with PRP. Some practitioners use this in combination with PRP. The problems are that we have no long term data on the safety of this mixture. Also, when treating athletes, this approach is problematic vis-a-vis regulations from the World Anti-Doping Agency.
At our center, where we have had an extensive experience with this type of treatment, we do not use growth hormone.