So, one of the newest treatments being touted in the sports medicine arena is platelet rich plasma (PRP) therapy.  What is this exactly?  It is not an easy thing to explain in plain terms, but here goes my best attempt.

Platelets help the repair process in the body as they contain growth factors like platelet derived growth factor (PDGF), transforming growth factor (TGF)-ß, insulin-like growth factor (IGF) and fibroblast growth factor (FGF) to name a few.  Upon activation, these factors are released and sent to aid the injured site in healing.  In this therapy approach, a centrifuge is used to increase concentration the concentration of platelets.  PRP has up to 8x the concentration of platelets that whole blood does.

The PRP is then usually injected into the injury site.  This is commonly being used to treat ligament sprains such as an MCL sprain in soccer players.  A recent study was released in the American Journal of Sports Medicine in March 2009 in regard to the effects fo PRP on muscle strains.  Muscle strains are largely considered the primary injury in sports medicine today (think about hamstrings, quadriceps, groin and calf strains to name a few).

Keep in mind muscle injuries typically occur when the muscle is lengthening under tension (eccentric contraction).  Why so?  In eccentric contractions the muscle force produced is approximately twice that of a maximal isometric contraction (max muscle force against static resistance without motion).

In this study, researchers looked at rats and induced a muscle injury to the TA (tibialis anterior muscle) in one of two ways: Group A underwent a single eccentric (lengthening) injury over a 90 degree arc of motion, while Group B underwent 45 smaller strains over a 60 degree arc to simulate more of a chronic muscle strain as opposed to an acute injury in Group A.

To summarize the results, researchers found that the PRP had little effect on Group A other than to noticeably affect force production in a positive way on day 3 post-injury.  They are unsure if this is simply due to reduced inflammation (PRP should help with this).  Otherwise, full force production with the single acute strain was back in 7 days relative to pre-injury levels whether using PRP or not.  However, in the repetitive or chronic strain group (group B) the PRP had significantly positive effects at day 7 and 14 and led to a faster overall recovery.

Does this mean we should use PRP on all muscle strains??  Not so fast.  What is clear are that injuries in need of myogenesis (muscle rebuilding) are better candidates for this therapy.  The tricky part is the great degree of variability in muscle strains and determining if the science is transferable from the rat to human model.  In the end, the treatment is promising as there appear to be no harmful side effects, but further research will be needed to validate the impact on healing tendons and muscles alike.

Also keep in mind that progressively rehabbing the injured part with systematic eccentric loading to restore the tissues’ threshold to stress is necessary to accurately gage response to functional mechanical loads.  My hope is that this procedure will be used in conjunction with rehab to speed healing and get athletes back on the field faster.  Its greatest use may come in dealing with chronic tendinitis or partial tears.  Only time will tell, so stay tuned.