Effects of Platelet-rich Plasma Injections - Thesis Example

?Effects of Platelet-rich Plasma Injections On the Ulnar Collateral Ligament in Baseball Pitchers Results and Discussion Results All 16 patients approached responded to the questionnaires, answering all questions, with less than five individual non-responses to questions across the whole group (Table 1). All patients surveyed fit the category of healthy adult males ranging between 15 and 40 years, who were baseball pitchers, had received an injury to their ulnar collateral ligament (UCL) and had received a platelet rich plasma (PRP) injection to the elbow. Thirteen of the patients had a dominant right hand (81.3%), while the remaining three had a dominant left hand (18.7%). The time it took for patients to have an exam following their injury varied widely, from four to 156 weeks, with the average being 32.9 weeks. Number of years played was less variable, with all patients having played at least six years of baseball, and some playing up to 17 years. The mean number of years as a baseball pitcher was 11.9 years. History of Injury Most of the patients had missed at least one game or practice within the last year due to an elbow injury (93.8%) with only one individual making all their games and practices (Table 2). In addition the majority of patients reported diagnosis of a UCL injury, although four (25%) had been given no diagnosis. The diagnoses included tear to the UCL (83.3%), partial UCL tear (8.3%), stress fracture (8.3%) and torn flexor tendon (25%). Many individuals were diagnosed with multiple types of injuries; hence the percentages indicate what percentage of diagnosed patients had a particular type of injury. Treatments that had been taken for the injury varied across rest, therapy, steroid injection, PRP or surgery. All patients had been given PRP injections, as this was a criterion for inclusion in the study. In addition, each patient had used at least one other method, with one patient using all five types, and eight patients (50%) using all but steroid injection as a method of treatment. Rest and therapy were the most popular treatments aside from PRP, with 14 patients (87.5%) using rest as a method of treatment, and 15 (93.7%) reporting use of therapy. Surgery was also popular, with ten patients (62.5%) reporting using surgery as a treatment for their UCL injury. Most patients had a single PRP injection, with only one patient having two and one having three. Time from the PRP injection to first picking up a baseball to throw ranged from two weeks to 16, with an average of 7.3 weeks. Patients were asked to give level of pain on a scale of 0-10 both before the PRP injection and the first time they picked up the baseball to pitch following the injection. The average score before the injection was 3.6, while afterwards it was 6.6. A total of 11 patients (68.8%) reported decrease in pain between before the PRP injection, and the first time they picked up the ball afterwards, four (25%) reported an increase in pain, while one did not give a pain level for after PRP injection. The result for the individual that did not give a pain level can be disregarded for this calculation, making the total proportion of patients that reported a decrease in pain to be 73.3%, and the proportion that reported an increase in pain to be 26.7%. There was some correlation between level of pain and weeks recovery time, but not in all cases (Figure 1). Figure 1: This graph shows the level of reported pain per patient compared with the number of weeks of recovery before they picked up the ball to pitch. Reported complications were relatively low, with only three patients (18.8%) reporting a long term increase in pain following the treatment, one (6.25%) reporting tingling or numbness, one (6.25%) reporting increased pressure and tightness, and four (25%) reporting decreased mobility in their elbow. Satisfaction with the PRP treatment was given on a scale of 0 to ten, with an average of 6.8. However, the average does not give the true picture, as responses were dichotomous, with most patients being either highly happy or not at all (Figure 2). Four patients indication zero satisfaction, one indicated five satisfaction (the middle mark) while the remainder put satisfaction at eight or higher. Only one patient went on to have surgery after PRP injections. Figure 2: Satisfaction of patients towards the PRP treatment on a scale of 0-10 where 0 meant complete dissatisfaction, and 10 meant full satisfaction. Competition level Five of the patients had played at major league level (31.2%), but following injury and PRP treatment, only two remained at this level (Table 3). Of the three that no longer play in the major leagues, two no longer play because of injury (66.7%), and one has dropped to the minor leagues, but states that injury was not the cause. Prior to injury three patients played in the minor leagues, following their treatment two of these returned to the minor leagues reporting no troubles, and one reported some troubles or pain while playing. Four patients originally played at the college level, one retired following treatment, one continues to play at college level, but reports problems with pain and two are yet to return to playing. Of the four high school level players, two returned to playing reporting problems with pain, and two are yet to return. For patients to return to competition the number of weeks ranged from seven to 54 weeks, with an average of 26 weeks however, two (18.2%) of those that returned to competition stopped playing at a later date due to pain. In total, four patients returned to competition with no pain (25%), five returned having some trouble (31.2%) and seven are yet to return, or returned but have since left competition due to pain (43.7%). Physical function Physical function appeared to vary significantly across both patients and activity (Table 4). Getting loose during warm up and control were both strong across patients, with no patients reporting levels below four and 31.3% reporting a ten for warm up, and 62.5% reporting a ten for control. More than 50% of patients reported their relationship with their coaches had not changed as a consequence of their injury, likewise, 53.3% of patients reported that they had not had to make any changes to their pitching motion because of the injury. The level of pain varied widely across individuals. No patients reported pain at rest, with the lowest recorded response being a three made by one individual (6.25%), a total of eight individual reported pain levels between four and seven inclusive (50%), while the remaining six reported the pain as between eight and ten (37.5%). Levels of weakness and fatigue followed the same pattern as pain levels, although one individual scored level of weakness as zero, being so bad that it prevented him from playing. Forty-three percent of patients reported no instability in their elbow, while the remaining patients had responses roughly evenly spread from nine down to two. The injury appeared to significantly affect the power or velocity of most of the patients’ pitches, with only 20% reporting no loss in power and 13.3% having to change to finesse pitching as they had no power left. Endurance varied widely, with 31.3% reporting no change in levels of endurance, with levels of endurance ranging from nine down to zero, with two individuals (12.5%) reporting significant loss that resulted in them having to become relief pitcher, throw less pitches or something similar Question ten addressed patients opinion on how their injury affects play. This had the widest range of responses with six individuals reporting that they had to stop playing (37.5%), three individuals reporting a large effect of the injury (18.8%), five reporting full desired level of competitive play (31.3%) and the remaining reporting middling levels of discomfort. Discussion This study looked at the effectiveness of platelet rich plasma (PRP) injections into the elbow in recovery and return to competition for baseball pitchers suffering from a ulnar collateral ligament (UCL) injury. This was achieved by contacting individuals who had received PRP injections as treatment for a UCL injury. These individuals were found using patient records and given a three part questionnaire that looked at the injury history, current sports status, physical function as well as basic demographic information. In total 16 eligible patients were contacted, all of which answered the questionnaires fully. This gives a substantial amount of data that can be evaluated. All patients had gone through a number of different therapies prior to PRP injections. While the most common were rest and physical therapy, more than half of the patients also underwent surgery prior to PRP treatment, and one patient did so afterwards. PRP is generally seen as an alternative treatment to invasive surgeries such as ulnar collateral ligament reconstruction , the Jobe figure-of-8 technique or a form of reconstruction that makes use of the triceps tendon . Pain levels Pain levels before and after the PRP treatment varied. Patients were asked to rate their pain level on a scale of 0-10 prior to PRP injection, and on the first time they picked up a baseball ball to throw. On average pain decreased following PRP injection, close to 70% of patients (11 out of 16) reported a decrease in pain as a consequence, one not giving enough information for this to be determined and four reporting an increase in pain. PRP is designed to help the healing process by helping the body repair itself by stimulating growth and tissue repair . The idea that using a patient’s own blood reduces complications , and reduces the time required to heal and return to play, as there is no incision that needs to heal . Consequently, we expected to see a decrease in pain with the administration of PRP, as the patients bodies repaired themselves. In some cases the decrease in pain was substantial, with Patient 1 reporting a change in pain from one, which indicated severe pain to ten which was no pain at all; likewise Patient 16 reported a change from zero, which was pain even at rest, to ten. Some changes were less drastic with Patients 7 and 8 reporting changes from three to ten, and two to ten, respectively. However, there were changes in the opposite direction. Patient 10 reported a change in pain levels from a middling six, to zero. This is a surprising result, as PRP shouldn’t harm the body in any way. It is difficult to determine why there was an increase in pain in four cases following PRP treatment; however this could be caused by insufficient rehabilitation following injury. On average pain decreased from 3.6 to 6.6 following PRP injection, indicating the treatment was effective. Variation in the amount of pain that patients felt could be connected to the amount of time before they attempted to throw a ball. This can’t be the case for patient 10; he had the longest recovery time, but highest level of pain (Figure 1). Likewise, patient 6 had a high recovery time, but his pain was high when he first picked up the ball. There seems to be no direct correlation between the number of week’s recovery and the level of pain experienced. Instead, the cause may be how long the patient waited between the time of injury and the exam. Patient 10 and 6 experienced the highest amounts of pain following treatment, and also waited the longest time before having an exam, 156 weeks and 72 weeks respectively, where the average for all patients was 32.9 weeks. In addition, patient 10’s injury was a stress fracture, which takes longer to heal than soft tissues. This provides information about the effectiveness and limitations of the PRP technique. It utilizes the body’s own repair system, and because of this appears to be limited when significant time has occurred since the injury. Satisfaction The majority of patients experienced no complications with PRP use. Three individuals reported increased pain and decreased mobility (Patients 2, 3 and 13 – patient 10 did not report increased pain for this question), while one patient reported decreased mobility alone, one reported increased pressure, and one reported tingling and numbness. Patients were polarized in their reactions to PRP, while the average satisfaction level was 6.8, this was because four patients placed satisfaction at zero. This was not directly related to pain levels, while four patients found an increase of pain through PRP, only two of these rated their satisfaction at zero. Indeed, one of the patients that rated satisfaction at zero was patient 16, who saw the biggest improvement in pain across the program. However, this patient did experience an unusual side effect of increased pressure and triceps tightness. These were patients 6, 11, 15 and 16. There is no indication why the last patient rated their satisfaction at zero. Of the sixteen patients that had PRP injections a total of seven had still not returned to playing at a competitive level. A further five had returned to playing, but were having some troubles. Physical function varied widely depending on the patient and the activity, for every type of physical activity a number of individuals rated their ability at ten, indicating a pain free ability to perform at the level prior to injury. However, for many types of physical function, some individuals reported low values such as zero, one and two, indicating that their level of activity was very impaired, and in some cases they had to change aspects of their game, such as moving towards finesse pitching, or becoming a relief pitcher. Outcomes of PRP use We had predicted that the use of PRP injections would help in relieving pain in patients that suffered from UCL injuries. Our study shows a clear decrease in pain levels as a consequence of PRP use, with 68.8% of patients reporting a decrease in pain. There were a number of factors involved in each of the individual patient’s cases, including the use of different combinations of treatments, different types of injury, different levels of initial pain and substantial differences in the time it took between the injury and getting the injury checked out. The number of differences between the patients, and the small sample size means that are results cannot be predictive, nor can they be easily applied to the general population. In addition, there was no control group, and the questionnaires were based on memory, so it is likely that the responses were not entirely accurate. However, close to 75% of patients saw a decrease in pain through the use of PRP, meaning that we can tentatively reject the null hypothesis that PRP has no effect on pain levels. It is difficult to ascertain for whether PRP was the driver of these pain decreases, as all patients had multiple treatments, and more than half also underwent surgery. It is surprising that for four patients a worsening of pain occurred. This can perhaps be explained in two cases, where the individuals waited a long period of time before getting their injuries treated, but there is no easily obtainable explanation for the other two increases. A similar study using autologous blood injection therapy, which has numerous parallels with PRP, across 28 patients found no reoccurrence or worsening of pain . Wider implications Platelet rich plasma injections are still a relatively new science in terms of medicine, although it has been used in plastic surgery since the late 1990s , and in surgery in general . The term refers to a range of technologies that work to enhance the body’s response to injury , promoting muscle regeneration . Traditionally, ligament reconstruction or repair through surgical grafts has been the method of treatment for UCL injuries , especially for UCL tears . The reconstruction returns the contact pressures, and reduces the resistance at the elbow to similar levels that they were before injury One study has found 83% of athletes to return to their previous level of performance following reconstruction of the UCL , while another study puts this figure at 90% . PRP has become more popular recently because of a demand to provide alterative or additional therapies to reconstruction, because of media publicity , and the thought that there may be alternative methods available . In addition it offers faster return to competition, which is important for the highly competitive nature of sports . One study that tested PRP injections against placebos for chronic midportion Achilles tendinopathy found that there was no significant improvement in pain or activity from the PRP compared to the placebo . Another study that looked at non-surgical treatment found that 42% were able to return to previous levels of competition, however this study was not predictive . An extensive study looking at 140 patients suffering chronic epicondylar elbow pain that received PRP injections found no side effects or complications, with 90% returning to sporting activities and 99% to their daily activities with no difficulties . One study found pain in some subjects following PRP administration, but pain reduction for most subjects . A study of 30 individuals found only one patient that reported no improvement following PRP injection, and none that suffered from increased pain .This indicates that the side effects and increased pain we observed may be a consequence of the combination of treatments the patients underwent, rather than the PRP itself. These studies, like this study, show that it is difficult to provide predictive results on non-invasive therapies for UCL injuries. Combining PRP with other cell therapies or matricies has been found to be a method of increasing the efficacy of the therapy, giving the pest possible results . In addition, it has been used in treatment of injuries that do not heal in order to reduce pain . There is still as substantial amount of work to be done with the use of PRP in sports medicine, as methods of plasma preparation are yet to be standardized , and there is a need for more clinical trials to ensure the safety and reliability of this type of treatment. There are concerns about the use of PRP in sports medicine because of its potential to enhance performance, and to be used as a performance-enhancing agent by athletes . PRP works by the additional platelets stimulating growth factors , and the concern is that if this was used on healthy athletes it could increase performance. Injuries to the UCL are common , and can often be a result of the dynamic actions involved in pitching , as stress is placed on the UCL while throwing the ball . In particular the motions involved in cocking and acceleration stress the UCL In young pitchers, the mechanical stress is able to alter the development of the joint, resulting in developmental anatomic changes . While treatment options for UCL injuries are many, prevention is still a better alternative, and being aware of proper stretching, conditioning and warm-ups as well as the mechanics of pitching can help to avoid tendon and ligament damage . For example, positive correlations has been found between elbow torque and elbow injuries as well as with pitch and velocity . Appendix Table 1: Demographics of patients interviewed. Patients were assigned arbitrary IDs (1-16) to protect privacy. No response to a particular question is indicated by a NR in the table. Patient ID 1 2 3 4 5 6 7 8 Dominant Hand Right Right Right Left Right Right Right Right Injury to exam (weeks) 5 16 4 6 58 72 9 38 Years played 14 NR 15 17 14 14 12 12 Patient ID 9 10 11 12 13 14 15 16 Dominant Hand Right Left Right Left Right Right Right Right Injury to exam (weeks) 26 156 28 14 12 51 25 6 Years played 6 9 7 12 7 17 8 15 Table 2: History of injury for the patients interviewed. Number assignments are the same as for the previous table. Question numbers refer to the History of Injury Questionnaire given earlier in this paper, where the first question was have you missed a game or practice time due to an injury to your elbow? *This patient had yet to return to playing, so was unable to give an after PRP injury score. ** Patient reported increased pressure and tricep tightness. Patient ID 1 2 3 4 5 6 7 8 Q1 Yes Yes Yes Yes Yes Yes Yes No Q2 Yes Yes Yes Yes Yes Yes Yes No UCL tear Yes Yes Yes Yes Yes Yes Yes Partial tear Stress fracture Torn flexon tendon Yes Yes Yes Q3 Rest Yes Yes Yes Yes Yes Yes Yes Yes Therapy Yes Yes Yes Yes Yes Yes Yes Yes Steroid Yes PRP Yes Yes Yes Yes Yes Yes Yes Yes Surgery Yes Yes Yes Yes Yes Yes Yes Q4 3 2 1 1 1 1 1 1 Q5 1 2 2 5 6 3 3 2 Q6 6 2 7 3 6 8 12 10 Q7 10 4 9 10 2 0 10 10 Q8 Infection Increased Pain Yes Yes Tingling/Numb Decreased Mobility Yes Yes Other Q9 10 5 10 10 9 0 10 8 Q10 No No Yes No No No No No Patient ID 9 10 11 12 13 14 15 16 Q1 Yes Yes Yes Yes Yes Yes Yes Yes Q2 No Yes No Yes Yes Yes No Yes UCL tear Yes Yes Yes Partial tear Yes Stress fracture Yes Torn flexon tendon Q3 Rest Yes Yes Yes Yes Yes Yes Therapy Yes Yes Yes Yes Yes Yes Yes Steroid PRP Yes Yes Yes Yes Yes Yes Yes Yes Surgery Yes Yes Yes Q4 1 1 1 1 1 1 1 1 Q5 6 6 3 5 7 0 7 0 Q6 6 16 12 5 12 4 3 4 Q7 10 0 4 NA* 10 8 2 10 Q8 Infection Increased Pain Yes Tingling/Numb Yes Decreased Mobility Yes Yes Other Yes** Q9 8 9 0 10 10 10 0 0 Q10 No No No No No No No No Table 3 Patient responses to questionnaire on current level of baseball competition following PRP injections, given earlier in the paper. Patient ID assignments are the same as in previous questionnaire. An entry of NR means that no response was given from the patient to the question. Patient ID 1 2 3 4 5 6 7 8 Q1 Major Major Minor Major Major College Minor College Q2 Not Playing Major Minor Minor Major College Minor Retired Q3 Yes No NR Q4 Not Returned 32 24 9 52 20 20 54 Q5 No trouble Yes Yes Yes Trouble Yes Yes Not playing Yes Yes Yes Patient ID 9 10 11 12 13 14 15 16 Q1 High School College High School College High School Major High School Minor Q2 High School College High School College High School Minor High School Minor Q3 Yes Q4 7 Not Returned Not Returned Not Returned Not Returned 7 52 12 Q5 No trouble Yes Trouble Yes Yes Yes Not playing Yes Yes Yes Yes Table 4: Patient responses to questions on the physical function of patience during the game and practice, questions are given earlier in the paper. Patient ID is the same as previous tables. NA indicates that the patient no longer engages in the activity. For all questions patients were asked to answer on a scale of 0-10 with 10 being normal and 0 being very different than normal. Specific meanings per question are explained with the questions. Patient ID 1 2 3 4 5 6 7 8 Q1 8 4 10 10 4 7 10 6 Q2 5 5 9 10 4 2 10 7 Q3 0 5 9 10 5 10 10 4 Q4 5 9 9 10 10 10 10 2 Q5 6 8 4 10 10 5 10 10 Q6 6 10 10 10 6 0 10 5 Q7 10 6 10 7 6 0 10 0 Q8 10 10 9 10 5 0 10 10 Q9 5 10 10 7 6 7 10 10 Q10 0 10 10 7 0 0 10 2 Patient ID 9 10 11 12 13 14 15 16 Q1 10 7 10 6 5 8 5 6 Q2 5 4 3 6 10 8 4 8 Q3 10 9 7 4 10 7 4 6 Q4 10 6 3 4 10 10 2 7 Q5 10 3 10 9 10 10 4 0 Q6 10 10 10 7 NA 10 9 8 Q7 6 7 3 9 NA 7 7 5 Q8 7 8 0 3 2 9 4 4 Q9 10 10 4 4 10 10 10 10 Q10 10 2 0 2 0 10 0 6 Bibliography Andia, I., M. Sanchez, and N. Maffulli. "Tendon Healing and Platelet-Rich Plasma Therapies." Expert Opinion on Biological Therapy.0 (2010): 1-12. Print. Azar, F.M., et al. "Operative Treatment of Ulnar Collateral Ligament Injuries of the Elbow in Athletes." The American journal of sports medicine 28.1 (2000): 16. Print. Blatman, H.S. "Prolotherapy Therapy with Platelet Rich Plasma". 2011. blatmanpainclinic.com. 3 July 2011. . Bowers, A.L., et al. "Elbow Medial Ulnar Collateral Ligament Reconstruction: Clinical Relevance and the Docking Technique." Journal of Shoulder and Elbow Surgery 19.2 (2010): 110-17. Print. Bushnell, B.D., et al. "Association of Maximum Pitch Velocity and Elbow Injury in Professional Baseball Pitchers." The American journal of sports medicine 38.4 (2010): 728. Print. Cain, E.L., et al. "Outcome of Ulnar Collateral Ligament Reconstruction of the Elbow in 1281 Athletes." The American journal of sports medicine 38.12 (2010): 2426. Print. Creaney, L., and B. Hamilton. "Growth Factor Delivery Methods in the Management of Sports Injuries: The State of Play." British journal of sports medicine 42.5 (2008): 314. Print. de Vos, R.J., et al. "Platelet-Rich Plasma Injection for Chronic Achilles Tendinopathy." JAMA: the journal of the American Medical Association 303.2 (2010): 144. Print. DiGiovine, N.M., et al. "An Electromyographic Analysis of the Upper Extremity in Pitching." Journal of Shoulder and Elbow Surgery 1.1 (1992): 15-25. Print. Dodson, C.C., et al. "Medial Ulnar Collateral Ligament Reconstruction of the Elbow in Throwing Athletes." The American journal of sports medicine 34.12 (2006): 1926. Print. Duggan Jr, J.P., et al. "The Impact of Ulnar Collateral Ligament Tear and Reconstruction on Contact Pressures in the Lateral Compartment of the Elbow." Journal of Shoulder and Elbow Surgery 20.2 (2011): 226-33. Print. Edwards, S.G., and J.H. Calandruccio. "Autologous Blood Injections for Refractory Lateral Epicondylitis." The Journal of hand surgery 28.2 (2003): 272-78. Print. Fleisig, G.S., et al. "Kinetics of Baseball Pitching with Implications About Injury Mechanisms." The American journal of sports medicine 23.2 (1995): 233. Print. Fleisig, GS, CJ Dillman, and JR Andrews. "Proper Mechanics for Baseball Pitching." Clin Sports Med 1.1 (1989): 151–70. Print. Foster, T.E., et al. "Platelet-Rich Plasma." The American journal of sports medicine 37.11 (2009): 2259. Print. Gaweda, K., M. Tarczynska, and W. Krzyzanowski. "Treatment of Achilles Tendinopathy with Platelet-Rich Plasma." Int J Sports Med 31.8 (2010): 577-83. Print. Gong, H.S., et al. "A New Technique for Lateral Ulnar Collateral Ligament Reconstruction Using the Triceps Tendon." Techniques in Hand & Upper Extremity Surgery 13.1 (2009): 34. Print. Hall, M.P., et al. "Platelet-Rich Plasma: Current Concepts and Application in Sports Medicine." Journal of the American Academy of Orthopaedic Surgeons 17.10 (2009): 602. Print. Hammond, J.W., et al. "Use of Autologous Platelet-Rich Plasma to Treat Muscle Strain Injuries." (2009). Print. Hariri, S., and MR Safran. "Ulnar Collateral Ligament Injury in the Overhead Athlete." Clinics in Sports Medicine 29.4 (2010): 619. Print. Hechtman, K.S., et al. "Platelet-Rich Plasma Injection Reduces Pain in Patients with Recalcitrant Epicondylitis." Orthopedics 34.2 (2011): 92. Print. Hutson, M., and C. Speed. Sports Injuries. Oxford Univ Pr, 2011. Print. Kon, E., et al. "Platelet-Rich Plasma (Prp) to Treat Sports Injuries: Evidence to Support Its Use." Knee Surgery, Sports Traumatology, Arthroscopy (2010): 1-12. Print. Limpisvasti, O., N.S. ElAttrache, and F.W. Jobe. "Understanding Shoulder and Elbow Injuries in Baseball." Journal of the American Academy of Orthopaedic Surgeons 15.3 (2007): 139. Print. Lopez-Vidriero, E., et al. "The Use of Platelet-Rich Plasma in Arthroscopy and Sports Medicine: Optimizing the Healing Environment." Arthroscopy: The Journal of Arthroscopic and Related Surgery 26.2 (2010): 269-78. Print. Mehta, V. "Platelet-Rich Plasma: A Review of the Science and Possible Clinical Applications." Orthopedics 33.2 (2010): 111-14. Print. Mei-Dan, O., et al. "Autologous Platelet-Rich Plasma: A Revolution in Soft Tissue Sports Injury Management?" The Physician and sportsmedicine 38.4 (2010): 127. Print. Mishra, A., and T. Pavelko. "Treatment of Chronic Elbow Tendinosis with Buffered Platelet-Rich Plasma." The American journal of sports medicine 34.11 (2006): 1774. Print. Osbahr, D.C., et al. "Combined Flexor-Pronator Mass and Ulnar Collateral Ligament Injuries in the Elbows of Older Baseball Players." The American journal of sports medicine 38.4 (2010): 733. Print. Petty, D.H., et al. "Ulnar Collateral Ligament Reconstruction in High School Baseball Players." The American journal of sports medicine 32.5 (2004): 1158. Print. Redler, L.H., et al. "Platelet-Rich Plasma Therapy: A Systematic Literature Review and Evidence for Clinical Use." Phys Sportsmed 39.1 (2011): 42-51. Print. Rettig, A.C., et al. "Nonoperative Treatment of Ulnar Collateral Ligament Injuries in Throwing Athletes." The American journal of sports medicine 29.1 (2001): 15. Print. Safran, M.F. "Ulnar Collateral Ligament Injury in the Overhead Athlete: Diagnosis and Treatment." Clinics in Sports Medicine 23.4 (2004): 643-63. Print. Sampson, S., M. Gerhardt, and B. Mandelbaum. "Platelet Rich Plasma Injection Grafts for Musculoskeletal Injuries: A Review." Current reviews in musculoskeletal medicine 1.3 (2008): 165-74. Print. Sanchez, M., et al. "Platelet-Rich Therapies in the Treatment of Orthopaedic Sport Injuries." Sports Medicine 39.5 (2009): 345-54. Print. Savoie, F.H., et al. "Primary Repair of Ulnar Collateral Ligament Injuries of the Elbow in Young Athletes." The American journal of sports medicine 36.6 (2008): 1066. Print. Schwarz, A. "A Promising Treatment for Athletes, in Blood." The New. Print. Werner, SL, et al. "Biomechanics of the Elbow During Baseball Pitching." The Journal of orthopaedic and sports physical therapy 17.6 (1993): 274. Print. Woodell-May, J.E., and W.S. Pietrzak. "Platelet-Rich Plasma in Orthopedics." Musculoskeletal Tissue Regeneration (2008): 547-68. Print.  Read More