What is PRP and How Does it Work?

Platelet rich plasma (or PRP as it is called) is the "treatment du jour" for many soft tissue injuries since being mentioned as the technique that allowed Hines Ward to play in the Super Bowl.

Before stating specifically what PRP is, I will discuss the rationale behind its use.

Wound healing is a complex staged process that involves a number of cells.

The first event during injury is bleeding followed by tissue regeneration.

There are three distinct stages of tissue regeneration. These include: inflammation, proliferation (multiplication) of cells, and tissue remodeling.

Initially in the laboratory, scientists discovered a technique to initiate and accelerate tissue regeneration. They found that an autologous (from the self) platelet concentrate was filled with growth and healing factors. First used in animal models, this treatment was then used in human subjects with success.

What was found was that there was a minimal number of platelets required to make this technique work.

While the average platelet count in a normal human being is about 200,000/mm, the amount in a standard platelet concentrate used for PRP is about 1,000,000/mm or more.

PRP is collected by drawing a 20-60 cc volume of blood, then concentrating it in a special centrifuge. The total volume of fluid containing the platelets is approximately five cc. The platelets within the PRP release growth factors over 7 days.

Lesser platelet concentrations or platelets that aren't viable (living and working) will not enhance wound healing.

Platelets contain what are called "alpha granules" that are packed with growth factors. These bioactive growth factors both start as well as accelerate tissue repair and regeneration at the wound site. These growth factors include: adhesion molecules, fibrinogen, interleukin-1 beta, platelet-derived growth factor, transforming growth factor-beta, epidermal growth factor, and vascular endothelial growth factor.

When the PRP is administered to the wound site, it needs to be activated. This is accomplished using a variety of substances. Once activated, the PRP forms a gel. The framework of the gel is set up by both platelets as well as fibrin. The gel forms a temporary sealant and barrier that allows the initiation of tissue regeneration.

Growth factors concentrate within the scaffold and are slowly released over several days. Most importantly, the gel acts as a structure where stem cells can bind. This latter function is important since stem cells are often used along with PRP.

The growth factors from the platelets attract cells to the area to start and accelerate inflammation. This is called chemotaxis. Stem cells, if used, are also attracted (chemoattraction). The growth factors from the platelets also stimulate cell multiplication. This is particularly important, again, if stem cells are used.

PRP is best used for soft tissue injuries such as sprains, strains, tendonitis, and bursitis.

One critical component to the proper use of PRP is the use of ultrasound needle guidance. If the PRP isn't placed in the exact location needed, it won't work. The physician administering PRP must be well-experienced not only in the science and biology of this material but must also be a master of ultrasound needle guidance.

Usually, a tenotomy, meaning making multiple holes in the injured tendon or bursa needs to be done prior to introduction of the PRP.

PRP treatment may have to repeated about 20 per cent of the time if there is no sign of improvement after 4 weeks.

One important issue: all anti-inflammatory and immunosuppressive drugs should be avoided prior to and for 4 weeks following institution of PRP therapy. These drugs may reduce the effectiveness of PRP.

For more information about PRP or stem cell therapy, call the Arthritis and Osteoporosis Center of Maryland at (301) 694-5800.