Platelet-rich plasma (PRP) is a preparation of autologous human plasma with increased platelet concentration formed by centrifuging a large volume of a patient’s own blood.
Platelets contain many growth factors which can be concentrated during the centrifugation to a number greater than what is typically in found in our body. Normal platelet counts range from 150,000 to 350,000/uL. Suspected improvements in healing occur with up to 3-5 fold increase in concentration, ranging up to 1,000,000/uL.
In general, whole blood is collected and then mixed with anticoagulant factor prior to centrifugation, separating the red cells from platelet poor plasma and the “buffy coat”, which contains concentrated platelets and leukocytes. This concentrated plasma is then injected back into the injured area.
There are multiple studies proving its safety and low side effect profile. Unfortunately, there are many different preparations and systems, so variation exists in protocol and preparation; platelet capture efficiency, isolation method, speed of centrifugation, type of collection tube system and operation. These variations create challenges in interpreting literature regarding clinical efficacy.
PRP is often used for tendon injuries, as it has produces many of the cytokines involved in the healing stages of inflammation, cellular proliferation and subsequent remodeling. It may also promote neovascularization; increase blood supply and nutrients needed for cells to remove debris from damaged tissue and heal the injured tissue.
Recently, PRP has become more prevalent for osteoarthritis (hip and knee primarily). Leuckocyte-poor PRP (fewer neutrophils) is injected intraarticularly. Level 1 (Smith PA, AJSM 2016; Shen L., J Ortho Surg 2017) studies have shown reduced pain and function up to 12 months in knee osteoarthritis; but long-term studies are still needed. The benefits have only been demonstrated in mild to moderate osteoarthritis. The results for hip osteoarthritis are not as strong, showing better short-term compared to hyaluronic acid injections, but equivocal long-term effects.
PRP is occasionally used to augment surgical repair; rotator cuff repair, decreasing donor site pain with ACL reconstruction, etc. The is some movement towards using it for ankle sprain, muscle injury, and fracture non-union, but significant benefits have yet to be proven.