How reliable are animal studies when checking out something that is going to be used on humans? I ask this because my surgeon wants to inject my own blood plasma into my elbow for a true golfer’s elbow. But when I went on-line, most of the studies using this blood injection therapy have been on animals. So I’m a little less than enthusiastic to try this new treatment. What can you tell me?

As you have probably already found out from your own look into this treatment, platelet-rich plasma (PRP) (also known as blood injection therapy) is a medical treatment being used for a wide range of musculoskeletal problems (in humans!). Platelet-rich plasma 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 musculoskeletal problems, but gaining popularity quickly.

Research has been done on both animals and humans. Animal studies give researchers a place to start until the technique is determined to be safe and effective. Then trials with humans take place. So, although some studies have been done using an animal model, there are just as many using humans to evaluate this treatment.

So far, human studies have shown varied results — some clinical studies report decreased pain and improved use of the arm after PRP. Others show no improvement and the patients actually end up having surgery.

Why the difference and contradictory results? Experts speculate that different systems used to make the product may have something to do with it. Not all products are considered the same or “equal.” The best formula with the exact ratio of blood products (white blood cells and platelets) hasn’t been determined yet. In fact, it’s likely that different conditions (e.g., Achilles tendinitis, tennis elbow, golfer’s elbow) may respond better to one batch of platelet concentration compared to another.

This is where animal studies come in again — to help refine the current treatment techniques. For example, right now veterinarians at Cornell University in New York are using horses to investigate the effect of various platelet to white blood count ratios. They prepared and analyzed the results on healing for four different concentrations of platelet:white blood cells.

They found that the high levels of white blood cells (the leukocytes) caused increased inflammation. This was true no matter what platelet to leukocyte ratio used. Inflammation will delay or slow healing with the possibility of more scar tissue. At least from an animal model, it looks like reducing the amount of leukocytes in platelet-rich plasma (PRP) therapy might help stimulate the best healing response with the least amount of scar tissue. Increasing the amount of platelets does not counteract the inflammatory effect of the leukocytes.