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Platelet rich Plasma or PRP, is enriched blood product composed primarily of platelets — a type of cell found in the blood — is an emerging clinical tool for use in a wide variety of medical applications. With PRP, blood plasma is concentrated with higher than normal amounts of platelets, which most famously play a role in blood clotting, but have also been discovered to release a multitude of protein growth factors involved in many other biological responses involved in healing and tissue repair (Mishra & Pavelko, 2006). The theory behind PRP is that by introducing platelets in large quantities to a site of injury, the excess of growth factors might stimulate healing of long-term injuries that may contribute to chronic pain (Sampson, Gerhardt, & Mandelbaum, 2008).
PRP was first utilized during an open heart procedure in 1987, and has since found application in a wide variety of medical specialties, including (Sampson, Gerhardt, & Mandelbaum, 2008):
- Sports medicine
- Cosmetic/maxillofacial surgery
- Cardiothoracic surgery
The growing medical application of PRP is a direct result of an increased understanding of platelets and their physiological role in healing processes.
Musculoskeletal injuries are one of the most common causes of chronic pain and disability in the world, and PRP has been shown to be particularly suited their treatment (Sampson, Gerhardt, & Mandelbaum, 2008). Tendons in particular are very vulnerable to damage, which can lead to chronic pain. Tendons, which are composed of thick fibers, are vulnerable to injury as they anchor muscle to bone and are responsible for handling large amounts of force. They also heal very slowly, as the fibrous tissue contains very little vascular supply with which to receive blood and healing mediators such as platelets. Some of the best documented tendon-related musculoskeletal conditions that have been effectively treated with PRP therapy include:
- Lateral epicondylitis (“tennis elbow”) and medial epicondylitis (“golfer’s elbow”) refer to inflammation and pain caused at the bony insertions on either side of the elbow where tendons are tethered to muscles of the forearm. Epicondylitis is often an overuse injury that can cause chronic pain and can be difficult to treat.
- Tendons throughout the body that have suffered from overuse injuries leading to chronic pain and tendon thickening are a target for PRP therapy. Tendinopathies are common in physical laborers and recreational/professional athletes (Khan & Scott, 2012). Common sites of tendinopathy include the elbow, Achilles (heel), patellar (knee) and rotator cuff (shoulder) tendons.
PRP has more recently been reported to be helpful in the treatment of chronic pain due to osteoarthritis, bursitis (inflammation of fluid-filled sacs that lie between tendons and bone or skin), knee ligament injuries, plantar fasciitis (heel pain), wound healing and much more (Sampson, Gerhardt, & Mandelbaum, 2008). Clinical studies continue to accumulate data on the potential benefits of PRP therapy.
Anatomy and Physiology
Blood is primarily comprised of cellular components, including red blood cells, white blood cells and platelets, all contained within a liquid medium known as plasma. Each of these blood components has a special role in normal hematologic physiology (Sampson, Gerhardt, & Mandelbaum, 2008):
- Red blood cells act to transport oxygen and carbon dioxide throughout the body to sustain energy production and life.
- White blood cells act in an immunological capacity to stave off infection and clear debris from the body.
- Platelets are small, disc-like cells formed in the bone marrow that are important for blood clotting and vascular growth, healing, and repair. Platelets contain various granules, which carry clotting, and growth factors; these factors aid in healing processes once the platelets are activated. Platelets are activated by vascular (vessel) wall damage, or by other inducing factors in the blood.
- Plasma is primarily composed of water and acts to transport cells (such as red blood cells, white blood cells, and platelets), proteins, electrolytes and other critical materials throughout the body.
Over 90% of the cellular components of normal blood consist of red blood cells, while platelets account for approximately 6% of the cellular components (Sampson, Gerhardt, & Mandelbaum, 2008). In PRP, the ratio of cellular components is reversed so that the majority of cells within the plasma are platelets, which are more critical to healing processes than other blood components. PRP is considered effective when the platelets are concentrated to at least four times the baseline amount found in normal blood.
PRP effectively induces an inflammatory response at the site of injection, and is thus a type of autologous prolotherapy. Autologous refers to using a patient’s own tissue, in this case blood, while prolotherapy refers to the injection of a solution designed to stimulate proliferation of new connective tissue (Barkdull, O’Connor, & McShane, 2010). During this inflammatory response, unhealthy and injured tissue is absorbed by the body, paving the way for the formation of healthy new connective tissue via platelet-derived growth factors. The biochemical pathways and mechanisms mediated by the many different growth factors released by platelets are very complex and still not completely understood.
Prior to the procedure, the patient is informed of all risks, benefits, possible complications and alternatives to PRP injection therapy (Barkdull, O’Connor, & McShane, 2010). PRP injection therapy is generally completed in just one session, but may require additional injections depending upon the extent of tissue damage and clinical circumstances.
For the PRP procedure, a small volume (30-60 mL, or cc) of blood is drawn from the patient’s vein, placed within a sterile tube and spun within a centrifuge to allow gravity to separate individual components of the blood by weight (Sampson, Gerhardt, & Mandelbaum, 2008). This procedure is called blood fractionation. Once spun, the bottom of the tube will contain the heaviest cells, the red blood cells, while the top will contain fluid plasma with platelets. Separating these two layers is a small white, “buffy coat” layer, which contains the white blood cells and some platelets. The top plasma layer is then separated from the rest of the blood product and spun down more aggressively within a centrifuge to force the platelets to the bottom which is then extracted as a smaller volume of PRP (3-6mL, or cc).
Once the PRP solution is prepared, the patient will be positioned to a comfortable position on a procedural table. The site of injection is then cleaned and sterilized before a local numbing agent, such as lidocaine, is injected superficially to provide local anesthesia during the procedure. A needle is then guided to the intended injection target site, where the physician will administer the PRP. The physician may inject additional medications along with the PRP to ensure proper PRP adherence to the target site (Sampson, Gerhardt, & Mandelbaum, 2008).
In preparation for a PRP procedure, the pain specialist may elect to utilize ultrasound guidance to assist in guiding the needle to the correct location, as well as confirm that the PRP solution was properly placed in the targeted location (Barkdull, O’Connor, & McShane, 2010). Ultrasound can increase the accuracy of the PRP procedure, and potentially reduce post-procedural pain. If ultrasonography is used in conjunction with PRP injection, the patient and physician will review the imaging results during the procedure.
There are certain contraindications to PRP injection therapy, in which a patient may not be immediately eligible for treatment. Infection or broken skin at the injection site, blood clotting disorders, concurrent anti-coagulant therapy, multiple prior injections, pregnancy, or unstable/inaccessible joints may preclude use of the procedure to treat chronic pain (Barkdull, O’Connor, & McShane, 2010).Patients should discuss any of these conditions with their physician before undergoing a PRP procedure.
The entire procedure typically takes between 1-2 hours.
PRP represents an alternative to more conventional treatments of chronic pain, such as medical therapy with pain relievers, corticosteroid injections and even surgery; conventional treatments are unable to alter the inherent healing problems found with tendon tissue, whereas PRP introduces growth factors that can stimulate the clearance of unhealthy tissue and natural healing processes (Sampson, Gerhardt, & Mandelbaum, 2008). Initial improvement in pain is generally seen within a few weeks, and is often a gradual process as the damaged tissue heals.
The benefits of PRP therapy has been shown to be maximized when PRP is combined with physical therapy modalities also designed to stimulate new tissue growth (Barkdull, O’Connor, & McShane, 2010). A physician will discuss with the patient about certain home exercises that may increase the effectiveness of the PRP treatment, or submit a referral for specific physical therapy protocols on behalf of the patient.
In general, PRP injection therapies have been shown to be very safe when performed by an experienced pain management physician, and can be effective for treating chronic musculoskeletal pain where other more conservative or conventional treatment options have failed (Rabago & Zgierska, 2012). Because a patient’s own blood is used for the procedure, risks of transmissible infections or allergic reactions to the procedure are very low.
Because PRP effectively induces an inflammatory response, patients will most likely experience some post-procedural pain at the injection site for up to 48 hours (Barkdull, O’Connor, & McShane, 2010). Higher volumes of injected PRP may cause more post-injection pain. Post-procedural pain can typically be managed with ice and over-the-counter pain relievers like acetaminophen (Tylenol®); however the physician may elect to prescribe opioid prescription pain relievers if significant post-procedural discomfort is expected. Non-steroidal anti-inflammatory agents (NSAIDS) such as aspirin (Bayer®) or ibuprofen (Motrin®, Advil®) should be avoided as they exhibit anti-platelet and anti-coagulant effects, which may diminish the effectiveness of the PRP treatment (Barkdull, O’Connor, & McShane, 2010).
While rare, there are certain inherent risks with any injection procedure (Barkdull, O’Connor, & McShane, 2010). These include:
- Infection of the injection site
- Bleeding, especially with anticoagulant therapy or bleeding disorders
- Tendon rupture due to improper needle placement
Following the PRP procedure, patients should be alert to increased pain, swelling or redness at the injection site, or fever, which may indicate a possible infection. Some physicians may have the patient return within 1-2 days of the procedure to monitor for complications (Barkdull, O’Connor, & McShane, 2010).
It is also possible that the PRP injection therapy may simply fail to provide adequate relief. While unlikely, if such a scenario occurs, the patient and physician may discuss alternative therapies to manage chronic pain.
PRP therapies have shown great promise in preliminary, but very well done randomized controlled trials — particularly for epicondylitis and tendon-related pathology (Rabago & Zgierska, 2012). These studies report that PRP can result in improved quality of life, decreased pain, improved function and healing of damaged tissue. One of the trials cited a 66% improvement in quality of life from baseline, for patients suffering from lateral epicondylitis, as compared to a 17% improvement from alternative corticosteroid injections. These early reports suggest that PRP therapy and the administration of growth factors may provide pain relief where other conventional therapies may have failed, and in some cases, may present an alternative to surgery for tendinosis and related musculoskeletal disorders (Mishra & Pavelko, 2006).
Barkdull, T., O’Connor, F., & McShane, J. (2010). Joint and Soft Tissue Aspiration and Injection. Retrieved from MD Consult. Pfenninger: Pfenninger and Fowler’s Procedures for Primary Care, 3rd ed.
Khan, K., & Scott, A. (2012). Overview of the management of overuse (chronic) tendinopathy. Retrieved from In: UpToDate, Basow. DS (Ed), Waltham, MA.
Mishra, A., & Pavelko, T. (2006). Treatment of Chronic Elbow Tendinosis with Buffered Platelet-Rich Plasma. Am J Sports Med , 1774-1778.
Rabago, D., & Zgierska, A. (2012). Epicondylitis. Retrieved from MD Consult. Rakel: Integrative Medicine, 3rd ed.
Sampson, S., Gerhardt, M., & Mandelbaum, B. (2008). Platelet rich plasma injection grafts for musculoskeletal injuries: a review. Curr Rev Musculoskelet Med , 165-174.