Emerging Insights On Platelet-Rich Plasma

Platelet-rich plasma has become more popular over the last several years as an orthobiologic option for foot and ankle injuries. Incorporating a mix of research findings with his own clinical experience, this author takes a closer look at how PRP may be beneficial for plantar fasciitis, Achilles tendinopathy, bone augmentation and wound healing.    The use of orthobiologics in the treatment of foot and ankle injuries, both in the clinical and surgical venues, is significantly increasing. Clinicians and surgeons continue to seek better ways to accelerate and mediate the healing of bone and soft tissue while incorporating less invasive techniques.    Over the last few years, the use of autologous platelet-rich plasma (PRP) has emerged in the forefront of biologic tools for foot and ankle specialists. Researchers have investigated the use of PRP in the treatment of tendon injuries, chronic wounds, ligamentous injuries, cartilage injuries, muscle injuries and for bone augmentation (intraoperative fusions and fracture repair).1    Platelet-rich plasma has been in use over the last four decades. Theoretically, PRP offers increased concentrations of autologous platelets, which yield high concentrations of growth factors and other proteins that will subsequently lead to enhanced healing of bone and soft tissue on a cellular level.    Platelet-rich plasma is a concentration of platelets derived from the plasma portion of centrifuged or filtered autologous blood. This platelet-rich solution can be an adjunct to healing as with a fresh surgical fusion or it can reinstate healing as with chronic tendon injuries. Platelet-rich plasma and related products have different labels throughout the literature including platelet-rich concentrate, platelet gel, preparation rich in growth factors (PRGF), platelet releasate and platelet-leukocyte-rich gel (PLRG).    Platelet-rich plasma may or may not become activated by another product. The PRP without activation is usually reserved for the treatment of tendon, muscle and other soft tissue. When PRP is available in a gel or fibrin sealant, one can use this both clinically and intraoperatively for wound healing and bone augmentation. There have been several studies investigating the efficacy of PRP and its applications including wound healing and podiatric surgery.1    There have been several basic science reviews and studies as well as clinical studies on PRP. There are both in vitro and in vivo studies. Animal and human studies have examined the benefits and safety of PRP. Many of these studies have adequately shown the safety and efficacy of PRP in the clinical and surgical setting.2-7    However, the human studies are limited by their inconsistencies, small sample size and lack of controls.8 Other limitations include a lack of standardization in technique, concentration of platelets, applications of clinical use, the volume injected, separation from whole blood and post-injection care. There also seems to be as many studies that confirm the benefits of PRP as there are studies that are inconclusive. An important distinction is whether the use of PRP is as beneficial in the acute phases of tissue healing as it may be in chronic pathology.    Foot and ankle applications for PRP fall into several categories. These categories include: acute and chronic ligamentous injuries, chronic tendinopathy (tendinosis), bone pathology, chronic wounds and cartilage injury. With this in mind, let us take a closer look at the use of PRP in the foot and ankle.

What You Should Know About Using PRP For Plantar Fasciitis

Barrett and Erredge investigated the use of PRP for plantar fasciitis in a small study.9 They obtained an ultrasound of the fascia before and after treatment, and utilized a patient pain scale to help determine efficacy. The patients were weightbearing in a walking boot for two days after the procedure and were subsequently in regular shoe gear with limited activity. They were restricted from using anti-inflammatories or other modalities.    The researchers found that six of nine patients achieved complete resolution of symptoms after two months.9 One patient had resolution after a second injection. After one year, 77.9 percent of the patients had no symptoms. Ultrasound measurements showed reduced thickness of the plantar fascia between pre- and post-injection. It is unclear how long the patients had their symptoms before treatment.    I have found promising results using PRP for those patients with chronic, recalcitrant plantar fasciitis. Patients may be candidates for PRP if they have failed conservative treatments after three to six months. The conservative treatments include rest, ice, compression, elevation, functional foot orthotics, physical therapy and cortisone injections.    Physicians should confirm diagnosis via ultrasound and/or magnetic resonance imaging (MRI). Use a skin marker to identify the site of most pain on palpation. Perform an initial anesthetic block at the site (For a primer on the acquisition and use of PRP, see “How To Acquire And Activate PRP” at right). Draw 60 cc of whole blood using the collection tube supplied with the Magellan Autologous Platelet Separator System (Arteriocyte Medical Systems). Use calcium chloride to activate the PRP. Do not use thrombin in order to keep the PRP in liquid form for injection.    After preparing the PRP with the Magellan system, utilize a 10 cc syringe and 25 gauge needle, and inject the patient with 5 cc to 8 cc of PRP from the 60 cc whole blood collection. This yields a concentration that is 10 to 6 times over baseline respectively. Anecdotally, I have found that as the concentration increases, the patient’s post-injection pain increases.    One should perform the injection under ultrasound guidance. While peppering the medial plantar fascial band with the needle, make several 0.25 cc pulsed injections, starting at the point of maximum tenderness. In many of the patients, one can appreciate the fibrosis of the ligament by feeling and hearing a crepitus as the needle passes in and out of the fascial tissue. After completing the injection, continued peppering of the fascia using the 25-gauge needle further aggravates the tissue.    Restrict the patient from using any anti-inflammatories or physical therapy modalities for up to three months. One may use acetaminophen or narcotics for pain as needed. I have found better results with a post-injection protocol of a walking boot and crutches with no weightbearing for three to five days. Then I have the patients walk in the boot for two to three weeks. Activity begins gradually around the third or fourth week in an athletic shoe and functional foot orthotic, and increases over a four-week period.    Some patients have benefited from a second injection six weeks after the first injection when the first injection yields only some relief in symptoms. Those patients who have no change in their symptoms after the first injection rarely benefit from a follow-up injection.

Pertinent Insights On Using PRP For Achilles Tendinopathy And Rupture Repair

Recent studies have shown that PRP can positively affect gene expression and matrix synthesis in tendon and tendon cells.11 It is important, however, to distinguish acute tendon injury from chronic cases when discussing and studying the use of PRP for tendon pathology.    Achilles tendon injury leads to a cascade of degenerating events, including hypovascularity, repetitive microtrauma and the addition of fibrous tissue, which can then lead to degeneration and weakness of the tendon. This eventually leads to rupture. In theory, PRP reverses the effects of tendinopathy by stimulating the revascularization and improving healing at the microscopic level.14    Alfredson and Lorentzon categorize Achilles tendon pathology into paratendinitis, paratendinitis with tendinosis and pure tendinosis.14 In paratendinitis, adhesions form between the paratenon and the tendon. Paratendinitis with tendinosis involves degenerative changes within the substance of the tendon as well as inflammation in the paratenon. In patients with pure tendinosis, there is often a palpable nodule. The hypothesis is that the introduction of PRP into the pathologic tendon will aid in the repair and remodeling of the tendon by tenocytes.    In a randomized, double-blind, placebo-controlled study, de Vos and colleagues assessed and treated patients with tendinopathy between the ages of 18 and 70.10 The clinical diagnosis included findings of a painful and thickened tendon in relation to activity and on palpation with symptoms lasting greater than two months. The patient base included 27 in the PRP group and 27 in the control group.    Researchers used 54 mL of whole blood to derive the PRP that was mixed with sodium bicarbonate to match the pH of tendon tissue. They injected a non-disclosed amount of PRP into five sites along the injured tendon under ultrasound guidance.    Patients were only allowed to walk short distances indoors in the first 48 hours. In days three to seven, patients were allowed walks up to 30 minutes. After one week, patients started an exercise routine with one week of stretching and a 12-week daily eccentric exercise program. Patients were not allowed to participate in weightbearing sports activities for four weeks after the injection and subsequently had a gradual return to these activities. They were only to use acetaminophen during the follow-up period.    Patient results were based on patient questionnaires that quantify pain and activity level. The results showed an improvement in 24 weeks by 21.7 points in the PRP group and 20.5 points in the placebo group. The study concluded that there was no significant difference between the groups.10    This study is limited by a number of factors. Researchers did not identify any characteristics of the tendon anatomy pre- and post-injection, neither clinically nor with imaging techniques. The sample size was small. They could not quantify the concentrations of PRP they used for each patient.    Sánchez and colleagues investigated the augmentation of Achilles tendon rupture repair with PRP in athletes (six in both the PRP group and control group).15 They used two PRP preparations on the primary repair of the Achilles in comparison with controls. Researchers mixed 4 mL of PRP with CaCl2. After 30 minutes, this mixture produced a fibrin scaffold, which researchers incorporated into the repair site between the tendon ends. Researchers mixed the remaining PRP with CaCl2 and immediately sprayed it onto the wound site before closure.    At the one-year follow-up, the study authors assessed the patients via physical examination and ultrasound imaging. They found that the PRP group was able to return to mild running with earlier range of motion and without wound complications in comparison to the control group.15    I have used PRP for the treatment of chronic Achilles tendinopathy in many patients. The treatment protocol is very similar to that of plantar fasciitis. One should choose patients based on the chronicity of their symptoms and the quality of the tendon. Those patients who have failed conservative therapies after three to six months are good candidates. In addition to pain, decreased activity and loss of function, most patients present with nodular thickening within the substance of the tendon. Some may even have multiple fibrotic nodules. I have also used PRP to treat patients who have an associated retrocalcaneal exostosis with varying results.    Confirm the diagnosis with ultrasound and/or MRI. Place a local anesthetic block well above the site of injection. Then prepare the PRP at the desired concentration from the whole blood collection and activate it with calcium citrate. Inject between 6 and 10 cc of PRP within the substance of the tendon, beginning at the site of pathology (pain and any bulbous mass). Approach the medial or lateral aspect of the tendon under ultrasound guidance with the patient in a prone position. Inject several pulsed (peppered) doses of about 0.25 cc at a time, using a 25-gauge needle to fenestrate the tendon.    Have the patient use a walking boot or crutches for up to one week after the procedure. Then allow the patient to bear weight in the boot for the next one to three weeks. Subsequently transition the patient into an athletic shoe with a gradual increase in weightbearing activity over a four-week period.    I have seen a significant reduction in pain, a decrease in the size of fibrous nodules within the tendon and a sooner return to regular and sporting activity after PRP. Most patients have been able to return to increased exercise and activity within two months of the injection. Again, some patients have benefited by a second injection about six weeks after the first injection.

Key Pointers On Using PRP To Help Address Cartilage Issues With OA

Many studies have examined the role of PRP in aiding the repair of cartilage in early osteoarthritis (OA). In vitro studies have shown that PRP has the potential of increasing proteoglycan and collagen synthesis in chondrocytes.16 In vivo studies have also been promising.17,18    Sánchez and colleagues reported results on a retrospective study for human patients with OA of the knee.19 They compared PRP injections and hyaluronan injections with three injections over three weeks. By week five, the pain scale success reached only 10 percent for the hyaluronan group and 33.4 percent for the PRP group.    Kon and colleagues studied the use of PRP injections in 115 osteoarthritic knees.20 They found improvements in pain at six months. Cugat and co-workers investigated plasma rich in growth factors (PRGF) on athletes with chondral defects with positive results.21    Mesenchymal stem cells can differentiate into chondrocytes and cartilage. Mishra and colleagues studied the effect of mesenchymal stem cells treated with PRP on cartilage regeneration in vitro.22 They found that a 10 percent PRP treatment increased cellular proliferation of chondrogenic differentiation over 10-fold versus the control.    An investigation by Wu and co-workers suggested promising results with using PRP as a chondrocyte carrier to fill acute cartilage lesions in the knee.23 A scaffold made with PRP and thrombin transferred chondrocytes to the lesion.    I have not found studies that show the effect of PRP on OA of the foot and ankle. Theoretically, however, there is evidence that suggests improvement in pain and cartilage regeneration could prove effective in the treatment of OA in the foot and ankle. At present, foot and ankle surgeons perform microfractures into cartilage lesions (osteochondral drilling) to initiate fibrocartilage repair. The marrow cells that infiltrate the joint after microfracture are similar to those from bone marrow aspirate, mesenchymal stem cells and PRP. It would seem logical that the introduction of such cell products by percutaneous injection or surgical transfer would, in fact, increase cartilage regeneration and repair.

Does PRP Have Potential For Bone Augmentation?

Platelet-rich plasma can augment bone or bone grafting. Concentrating platelets will increase the level of growth factors that could stimulate a prematurely terminated bone healing process.24,25 Initially, PRP was in use for graft augmentation in oral and maxillofacial surgery with Marx and colleagues finding significant improvements in fusion rates and bone density in the mandible.4 Percutaneous injection of PRP for fresh fractures can facilitate healing of nonunions, augment fresh arthrodesis procedures with and without bone graft, facilitate surgery using autogenous or allogenic bone graft, and also fill bone defects.    The effect of PRP on bone healing has undergone study in great detail both in vitro and in vivo.24-30 The theory is that the increase in platelets and their growth factors will stimulate and enhance levels of osteoprotegerin, osteopontin, osteoblast differentiation of myoblasts and osteoblastic cells, and osteoclast-like cells.28,29,31,32 Researchers are divided on the efficacy of PRP in the augmentation of bone and bone graft healing. There are many studies that show promise while others show little difference from PRP versus control or traditional products.    Gandhi and colleagues used PRP in nonunion fractures of the foot and ankle that were present for four months or more.7 Their findings suggest a decreased level of growth factors around nonunion fracture sites in comparison to fresh fracture sites. The addition of PRP in nonunions could then increase nonunion healing potential through increases in growth factors. These researchers found a 60-day mean resolution of the nonunions after the addition of PRP.    Bibbo and colleagues studied high-risk elective foot and ankle surgical patients.33 The risk factors included previous poor osseous healing, osteomyelitis, tobacco use, diabetic neuropathy, malnutrition, immunosuppression and alcohol abuse. They found that using either autogenous or allogenic graft enabled 116 fusion sites (94 percent) to achieve fusion in a mean of 41 days. They concluded that PRP may aid in union rates for high-risk patients.    Bielecki and co-workers used what they called platelet-leukocyte-rich gel (PLRG) percutaneously in delayed unions and nonunions of the humerus, femur, tibia, radius and clavicle.34 Using X-ray and absorptiometry examinations, these researchers followed 32 patients. They achieved total union in 9.3 weeks for all 12 delayed union patients treated with PLRG. In the nonunion group, union occurred in 13 of 20 patients with an average of 10.3 weeks with PLRG. Notably, researchers found delayed unions and nonunions over 11 months in duration had the least favorable results.    Overall, they concluded that percutaneous injection of PLRG into nonunion and delayed union fractures may be sufficient to facilitate union, and can replace more invasive bone marrow injections.34    Coetzee and co-workers studied the benefits of PRP in the union of the syndesmosis with the use of total ankle arthroplasty.35 The retrospective study compared 66 patients with the addition of PRP and 114 without augmentation. The control group had a fusion rate of 61 percent at eight weeks and 85 percent at six months. The PRP group had a fusion rate of 76 percent at eight weeks and 97 percent at six months. They also found an increase in the fusion rate of those patients treated with PRP who had a history of tobacco use. Barrow and Pomeroy reported similar results in a prospective study, finding an 85 percent union rate at eight weeks and 100 percent at six months.36    I have used PRP in conjunction with bone marrow aspirate to facilitate midfoot and rearfoot surgical fusions. For several years, researchers have studied the use of bone marrow aspirate to enhance the healing of bone.37 There are two types of stem cells that originate in the bone marrow: hematopoietic and mesenchymal. The hematopoietic cells differentiate into platelets whereas the mesenchymal cells differentiate into osteoblasts.    Research has demonstrated that mesenchymal stem cells differentiate into cartilage, bone, muscle and adipose tissue.38 Studies have shown that mesenchymal stem cells regenerate articular cartilage in animal models and in bone for human models.39-43 Investigators have noted that PRP and its growth factors and cytokines enhance mesenchymal stem cell proliferation.44,45 Theoretically, combining bone marrow aspirate and PRP can create an environment where platelets and stem cells can act together to enhance bone healing even further than when one uses them alone.    When it comes to selecting patients for augmentation of fusion with PRP, I consider the patient’s history and risk factors. Patients with a history of tobacco use, alcohol abuse, previous nonunions, diabetic neuropathy and osteoporosis are not good candidates. I have used PRP in conjunction with bone marrow aspirate in patients with or without the need for bone autograft or allograft.    I will harvest the bone marrow aspirate from the calcaneus or the proximal tibial metaphysis. Schweinberger and Roukis have documented the technique for acquiring the percutaneous bone marrow aspirate from these areas.46 The physician would combine the whole blood acquired for the PRP and bone marrow aspirate, and prepare them in the centrifuge. One can apply the final PRP and bone marrow aspirate mixture as a liquid or a gel. The gel forms by adding thrombin to the final mixture. Exposure of PRP to thrombin will induce platelet degranulation, which increases the concentration of growth factors.    Research has found the use of bovine thrombin can lead to the development of antibodies to the clotting factors V, XI and autologous thrombin, which can lead to multisystem failure.47 One now can use the same blood sample used to make PRP to generate autologous thrombin from prothrombin. The surgeon can achieve this by adding CaCl2 during the processing of the PRP, which leads to the formation of a dense fibrin matrix that traps the platelets. This results in a small amount of thrombin, minimizing activation and leading to a slow release of growth factors over seven days.11    The fibrin mass that is created is a gelatinous scaffold. This is a malleable product, which one can introduce between bones to be fused (with or without a bone graft) and introduce into bone defects.    When it comes to the combination of PRP and bone marrow aspirate, I have seen promising results in the form of increased bone healing rates with less pain and earlier radiographic evidence of fusion.

How PRP Can Enhance Wound Healing

Many foot and ankle surgeons face diabetic, iatrogenic, decubitus and venous chronic wounds. A plethora of biologic materials can aid in the closure of chronic wounds. Platelet-rich plasma also seems to have the properties to augment wound healing.    During the inflammatory phase of wound healing, an environment rich in cellular proteins forms an initial clot. This clot is composed of collagen, platelets, thrombin and fibronectin. In addition to aiding in hemostasis, these products lead to the release of growth factors and cytokines that will stimulate the cascade that ends in a healed wound. Platelet-rich plasma is full of these growth factors that could significantly aid in the closure of chronic wounds.    Several in vitro and in vivo studies have shown PRP can increase the potential of wound healing cell products. Smith and Roukis reviewed several studies investigating the use of PRP on chronic wounds (diabetic and non-diabetic) of the lower extremity.48 The majority of these studies found that wounds treated with PRP healed significantly sooner than wounds in the control groups. In most of the studies, the control groups that eventually underwent treatment with PRP achieved closure due to the effectiveness of PRP.    Some studies have shown the ability of PRP to combat wound infection.49-51 Bielecki and colleagues found that PRP gel inhibited the growth of Escherichia coli and Staphylococcus aureus.49 Further studies specific to wound care and PRP are necessary.

In Conclusion

Platelet-rich plasma has promise for the treatment of many foot and ankle pathologies. These pathologies include tendinopathy (Achilles, peroneal, posterior tibial, flexor hallucis longus, anterior tibial) and ligamentous injury (plantar fasciitis, lateral ankle).    Other possibilities for PRP include augmentation of bone intraoperatively with primary fusions, fresh fractures, nonunions, tendon rupture repairs, cartilage injury (ankle, subtalar, metatarsal cartilage lesions), sesamoiditis and chronic wounds.    I have been using PRP over the last two years. The results have been increasingly promising with regard to decreased pain, increased activity, improved function, faster recovery and increased strength. The use of PRP in the clinical setting may be advantageous for its ease of use, relative availability, low side effects and tolerability in comparison to more invasive techniques.    Although PRP has shown promise as indicated by positive clinical evidence, it is evident that additional, well-designed prospective studies on PRP and its use in foot and ankle pathology are necessary to measure its true effectiveness.    Dr. Soomekh is a Fellow of the American College of Foot and Ankle Surgeons, and a Diplomate of the American Board of Podiatric Surgery. He is on the faculty of the University Foot and Ankle Institute in Santa Monica, Calif.    For further reading, see the exclusive online sidebar, “What You Should Know About The Science Of PRP” at the above right.    Editor’s note: For related articles, see “Platelet Rich Plasma: Can It Have An Impact For Tendinosis And Plantar Fasciosis?” in the May 2009 issue of Podiatry Today, “Current Insights On Growth Factor Therapy” in the October 2007 issue, or “A New Approach To Using Growth Factors In Wound Healing” in the October 2003 issue.
 

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