Your blood is composed of 3 main solid ingredients, which are red blood cells, white blood cells and platelets. Red blood cells comprise the majority of the volume of your blood and are used to transport oxygen from your lungs to tissues around your body. White blood cells have a variety of functions, but are generally thought of as cells that fight off infection. Platelets have traditionally been thought of as cells that aid with blood clotting; however, recent therapeutic advances have shined the spotlight on the ability of these cells to store and release growth and healing factors to areas of injury or damage in your body.
The healing and growth factors that platelets contain include PDGF, TGF-Beta, VEGF and EGF to name a few. PDGF, Platelet Derived Growth Factor, stimulates formation of blood vessels and skin tissue, promotes cell replication and stimulates granulation tissue. TGF-Beta, Transforming Growth Factor – Beta, regulates bone cell metabolism and stimulates production of the matrix, or scaffolding, that surrounds your cells. VEGF, Vascular Endothelial Growth Factor, promotes formation of new blood vessels. EGF, Endothelial Growth Factor, promotes cell differentiation and formation of new skin, blood vessels and collagen.
Blood will typically consist of 93% RBC, 6% Platelets, and 1% WBC. The rationale for PRP benefit lies in reversing the blood ratio by decreasing RBC and increasing the volume of platelets to 4-5 times the normal amount found in blood. This allows for a supratherapeutic concentration of platelets with growth and healing factors to be injected into an area of interest such as arthritic joints or damaged tendons, which can now theoretically improve and augment the natural healing process.
How is PRP processed and injected?
A member of the Joint Pain Orthopedic team will draw 30-60mL of your blood using a vein in your arm. This blood is then processed using a centrifuge that separates the red blood cells and white blood cells from the mixture and isolates the plasma that contains the platelets. The plasma that contains the high concentration of platelets will then be drawn up into a syringe. There are additives that may be placed in this that would activate the platelets causing them to release all of their healing and growth factors so that it is primed and ready to help at the site of damage.
The area of interest is then prepared using sterilizing agents and injected with an anesthetic agent that may decrease the discomfort that can be associated with PRP after injection. The PRP is then injected after the anesthetic has taken effect and skin has been re-sterilized. This may by done using image guidance such as ultrasound or x-ray guidance.
Leukocytes are a specific type of white blood cell that is found inside your blood. This has been shown to cause an exaggerated inflammatory response if it is not separated from the PRP. In some cases, we are trying to elicit this inflammatory response; however, when treating for arthritis, the goal should be to decrease inflammation. There are different processing techniques that can separate these cells from the PRP.
Knee, Hip and Shoulder Osteoarthritis:
On a molecular level, PRP has been noted to stimulate cartilage cells and cells lining the joint called synoviocytes to produce cartilage matrix. These cells also react to the growth and healing factors found in PRP by decreasing the production of molecules that act to promote inflammation and the degradation of cartilage matrix. What this means for the arthritic joint is that PRP may slow down the progression of arthritis and improve inflammation and pain associated with arthritis. There are no studies to date that have shown PRP can regenerate a significant portion of cartilage or restore a joint back to the pre-arthritic condition.
Studies have indicated that pain can be reduced using PRP injections for knee arthritis and can be reflected by patient reported pain scores being reduced for 3-12 months after injections when compared to placebo, viscosupplementation and corticosteroid injections. These denote that PRP injections can be superior to the other aforementioned treatments for pain relief from knee arthritis.
Studies looking at use of PRP for hip osteoarthritis are limited; however, there is some evidence suggesting that PRP may decrease pain associated with hip osteoarthritis. More high-level studies need to be done to determine if PRP injections for hip arthritis are worthwhile doing.
Glenohumeral, or shoulder joint, osteoarthritis has limited evidence to support the use of PRP injections, although the injections appear to be well tolerated and safe.
Tendon and Ligament Ailments:
PRP may promote new blood vessel formation, which can improve the blood supply and nutrients available to cells that can regenerate injured tissue and remove debris from damaged tissue. This becomes important for specific tendon pains that can result from unfavorable biologic conditions for tissue healing.
Tennis Elbow, or Lateral Epicondylitis, is a condition that can cause a prolonged course of debilitation. Studies have indicated that PRP injections can cause significant reductions in pain and elbow tenderness when compared to active controls. Some studies have demonstrated a longer continuous relief of symptoms when compared to corticosteroid injections.
Jumper’s Knee, or Patellar Tendinopathy, has been evaluated as a potential ailment that can be improved with PRP injections. One particular study looked at dry needling alone versus the same process, but with the addition of PRP. The PRP-injected patients appeared to have a faster improvement in symptoms.
Plantar Fasciitis is a condition that has sometimes been treated with corticosteroid injections. There are concerns regarding a steroid injection at this site, as there have been reports of plantar fascia rupture and atrophy, or wasting, of the protective fat pad in the heel. PRP has been shown in studies to be a viable alternative to steroid injection for plantar fasciitis.
Rotator Cuff Tendinopathy in the shoulder have been demonstrated to be a safe alternative to corticosteroids when injected into the subacromial space.