Matt Kemp's PRP injection - will it work?

Over the last few years, many athletes have had PRP injections.  The most recent is Matt Kemp of the Los Angeles Dodgers, who had a PRP injection in his shoulder (A-C joint).  Other athletes such as Kobe Bryant, and Tiger Woods have also had this treatment for their injuries.

What is PRP? 

Platelet rich plasma, or PRP, is plasma from the blood which is concentrated in platelets.  Platelets help to signal many growth factors and and inflammatory cells to an injured area.  These cells help promote new blood vessels to form and remodel tissue.

How is it harvested and used? 

PRP can be harvested from your own body.  Blood is drawn out and spun in a centrifuge to help separate the platelets from the rest of the blood cells.  The platelet rich plasma is then injected into the problem area to stimulate an inflammatory and healing response.  After the injection, the area is immobilize to provide the area of injury the best environment to heal.

How effective is PRP? 

There are many studies on PRP, but the results are mixed.  There are few randomized prospective and blinded studies that study PRP, and those show mixed results as well.  However, studies do show that there appears to be some benefit in using it for chronic injuries and less benefit with acute injuries.

Will it work on Matt Kemp? 

Matt Kemp initially had an irritation in his shoulder in April and was treated with a steroid injection.  This appeared to help his problem but he began to have problems with his shoulder a few weeks ago.  MRI studies show that Matt Kemp has an irritation of his AC joint in his shoulder.  This injection may help provide an immune boost to the shoulder to allow the injured area to heal.  However, I'm not sure if the PRP injection will help him too much.  Although this problem appeared to start in April, the shoulder irritation that he is having now is fairly acute (a few weeks old) and there should already be some degree of inflammatory cells in the area.  A PRP injection simply would add more inflammatory cells into the area and hence may be redundant in this case.

Additionally, if Matt Kemp is looking to return to the field sooner, PRP will likely not speed up his recovery.  PRP is simply a modality that helps to recruit inflammatory and healing cells into the area of injury and this does not typically increase healing times at all.

References: 

1.  Weber SC, Kauffman JI, et al.  Platelet-rich fibrin matrix in the management of arthroscopic repair of the rotator cuff: a prospective, randomized, double-blinded study.  Am J Sports Med 2013; 41(2):263-70
2.  Rha DW, Park GY, et al.  Comparison of the therapeutic effects of ultrasound-guided platelet-rich plasma injection and dry needling in rotator cuff disease: a randomized controlled trial.  Clin Rehabil 2013; 27(2):113-22
3.  Chahal J, Van Theil GS, et al.  The role of platelet-rich plasma in arthroscopic rotator cuff repair: a systematic review with quantitative synthesis.  Arthroscopy 2012; 28(11):1718-27
4. Mishra AK, Skrepnik NV, et al.  Platelet-rich plasma significantly improves clinical outcomes in patients with chronic tennis elbow: a Double-Blind, prospective, multicenter, controlled trial of 230 patients.  Am J Sports Med 2013
5. Filardo G, Kon E, et al.  Platelet-rich plasma for the treatment of patellar tendinopathy: clinical and imaging findings at medium-term follow-up. Int Orthotp 2013
6. Martinelli N, Marinozzi A, et al.  Platelet-rich plasma injections for chronic plantar fasciitis.  Int Orthop 2013; 27(5):839-42