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Single Platelet-Rich Plasma Injection (PRP) addition to rehabilitation exercise for Hamstring Strain.
Abstract
Platelet-rich plasma (PRP) become popular biologically method used to accelerate healing in sports medicine and orthopedic surgery field. PRP has concentrated the human platelets to supra-physiologic levels. It is an autologous producing high level of the platelets concentration centrifuged from the peripheral vein. Then it re-injected under the ultrasound gaudiness during surgery or at a site of injury. METHOD: Seventeen physically active males (age 22.0±0.6) with acute hamstring strain injuries divided to 8 case group and 9 matched controls (age 21.6±2.8) were recruited as research participants. Case group participants were injected with single 3 ml of extracted PRP under ultrasound gaudiness. However, Blood samples were collected by venipuncture at standardized time points: before the injection and 24, 48, 72, and 96 hours after for case group and 4wks. and 8wks for both groups. RESULTS: there was significantly difference between the growth factors results of the case group after 4 weeks compared with the 8 weeks result of the control group. Additionally, the same significant results between the two groups after the 8 weeks. Nevertheless, the physical measurements related to hamstring Strain and Knee flexion range of motion between the two groups were not significant after 4 weeks or 8 weeks. CONCLUSION: a single 5-6 mL injection of autologous PRP combined with a rehabilitation program was effective in time return to play and reducing the severity of pain after an acute grade 2 hamstring injury. Additionally, increase in circulating concentrations of VEGF, IGF-1, PDGF and FGF-2.
Key Words: Platelet-rich plasma (PRP), Human Growth Factors, Hamstring Tear.
1. Introduction:
Up to 55% of sports-related injuries are skeletal muscle damage which causes excessive long-term pain and physical disability. Muscles strains and contusions represent more than 90% of sports-related injuries [1] [2]. Hamstring tear injuries are a common problem for athletes, and frequently results in prolonged rehabilitation, time missed from play, and a significant risk of re-injury [3]. Approximately, one-third of athletes with the hamstring strain are prone to the similar injury after two weeks of their return to activity [4]. The high recurrence rate of hamstring injuries has led to use new appropriate rehabilitation strategies. Therefore, platelet-rich plasma (PRP) becomes a popular biological method for accelerating healing in sports medicine and orthopedic surgery. The PRP has concentrated the human platelets to supra-physiologic levels. It is an autologous producing high level of the platelets concentration centrifuged from the peripheral vein. Then it re-injected under the ultrasound gaudiness during surgery or at a site of injury [5] [6]. Indeed, the human blood contains 6% platelets, 1% white blood cells, and 93% red blood cells. The PRP technique aims to reverse the concentration of the platelet in lieu of red cells to increase the growth factors which will be more useful for accelerating the healing [7]. However, platelet-rich plasma is a centrifuged blood product that contains a supra-physiologic number of platelets. Therefore, the preparation to produce a concentrative platelet above the baseline values starts with an autologous extraction of patients` blood, and then follows by plasmapheresis centrifuging to obtain the concentrated suspension of platelets. The plasmapheresis centrifuge separates the solid and liquid components of the anticoagulated blood after a two-stage of centrifugation processes [8]. The initial phase separates the plasma and platelets from the erythrocytes and leucocytes. The second stage consolidates the platelets further into platelet-rich and platelet-poor plasma components [9] [10].Since the 1950s, the platelet-rich plasma (PRP) has been used extensively in dermatology and maxillofacial surgery [11]. In the 2010, the world anti-doping agency’s (WADA) prohibited list banned the platelet-derived preparation including PRP because the concentrative growth factors in PRP might treat the injured athletes unfairly. In 2011, WADA unraveled the lack of evidence to lift the ban on PRP, and also encouraged the researchers to improve its efficiency and practicality [12].
The mechanism of platelet-rich plasma does not differ from the physiological healing process, but it allows for obtaining higher concentrations of growth factors which accelerates the tissue regeneration [13] [14] [15]. The PRP contains some biological factors which enhance the proliferation and collagen secretion of tenocytes. These factors include vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF2), and transforming growth factor β (TGF β) [16] [17]. It also contains platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and insulin-like growth factor 1 (IGF-1) [18] [7]. The platelet α-granules are comprised of hemostatic factors, regulators inflammation, and wound healing. The platelet substances stored in dense granules are thrombocyte-activating factors. The platelets also contain lysosomal granules, which secrete acid hydrolases [19] [20]. However, there is an increasing of PDGF and TGF-β stimulus response in the early stages of tendon and muscles healing after the PRP injection, which resulting in new vessel formation and collagen synthesis. [21]. In addition, the decrease of the oxidative stress could lead to cell apoptosis [22], which reinforced by the release of inflammatory mediators, such as COX-1 and2, PGE-2 [23] [24].
Various researchers reported the benefits of treating soft tissue injuries (e.g., muscles tears and tendinosis) by injecting platelet-rich plasma. Despite this popularization and increasing use in soft tissue injuries, its efficiency remains controversial. It has been previously established that platelets provide regenerative potential by the process of chemo-taxis [25] [26] [27]. The use of PRP for accelerating recovery time after muscle injury has become a common practice in sports medicine. Several studies present that PRP can improve skeletal muscle healing after acute injury. A localized PRP, which increased expression of several myogenic factors at mRNA level, acting on modulating the inflammatory response and myogenesis in the early stages after acute injury [28] [29]. The current study aims to elucidate the effects of an autologous single PRP combined with a rehabilitation program on some growth factors concentration, and time return to sport for athletes with acute grade 2 hamstring injury.
2. Methods
2.1. Design and Participants:
This study was designed as a single-blinded randomized controlled study and followed ethical research principles set by the World Medical Association Declaration of Helsinki and the Damietta University Ethics Office, Egypt. The Department of Sports Health Science, Damietta University, reviewed and approved the research protocol. The research activities included participant recruitment, initial therapy, randomization, treatment and intervention, measurement, and analysis. The procedures were explained to, and written consents were collected from the research candidates prior the study.
Twenty-three physically active male athletes with a 2nd-grade acute hamstring tear were recruited from the Damietta Teaching Hospital and Mansoura University Hospital, Egypt. Three experienced (i.e., more than five years) sports physicians confirmed these athletes’ injuries through standard radiography and ultrasound diagnostics (Philips IU 22 ultra-sound with 17–5 MHz Probe). The injured muscle(s) and the injury grade was reported using the three-graded classifications of Hancock: et al [30]. Grade 3 total muscle or tendon rupture, grade 2 was a partial tear with increased intensity on fluid sensitive, and grade 1 no macroscopic tear with heightened signal intensity on fluid sensitive [31]. These athletes then checked against exception criteria, which were: (a) have not received PRP injections within one year; (b) have not consumed anti-inflammatory medicines within one month; and (c) have not undergone Hamstring, diabetes, anemia, vascular insufficiency, cardiovascular, or peripheral neuropathy surgeries. Based on these criteria, five athletes were excluded from the study; these athletes have either a 1st-grade, a recurrent, or a prolonged (i.e., more than a month) Hamstring strain injury.
Seventeen patients were ultimately enrolled (age 21.8 ± 2.64y, mass 71.52±2.74 Kg, height 175.4±2.32). The participants immediately received initial therapy for 5-7 from the day of injury according to PRICE principles (protection, rest, ice, compression, and elevation). The participant’s randomization was conducted with software (Computerized Covariate Adaptive Randomization Program, version 1.0, Middle Tennessee State University, Murfreesboro, TN). Eight injured athletic males (age 22.0±0.6) considered as a case group and nine matched controls (age 21.6±2.8) were recruited as control participants. The case and control groups were performed rehabilitation program included aquatic exercise and functional exercise for 8 weeks. However, the case group only was received an autologous single PRP injection.
2.4. Rehabilitation program:
The primary goal this study rehabilitation program is to minimize the risks of injury recurrence and restore the athletes’ performances to the same level prior the injury. In this study, both groups received similar eight-week rehabilitation program designed for lower limb and Hamstring muscles, which include aquatic, endurance, and functional exercises. In addition to the rehabilitation program, the cases also received an autologous single PRP injection. The rehabilitation program was organized into two stages. The duration of each stage was four weeks, where each week consisted of five sessions. The program began one week after the initial therapy. All participants were prohibited from engaging in any sports activities until the end of the program.
One rehabilitation session was 50-60 minutes long, where 10-15 minutes were dedicated for warming up and cooling down. Several experienced (i.e., more than five years) physiotherapists supervised the rehabilitation program. Similar to the participants, these physiotherapists were also randomly assigned to the case and control groups. The first stage of this program involved aquatic exercise (i.e., proprioceptive training, the range of motion ROM, and isometric and isotonic exercises). In the second stage, aside from the aquatic exercise, the participants also engaged in endurance and functional exercises. All rehabilitation exercises were carefully individualized in terms of duration and intensity with respect to the participants’ recovery progress and pain tolerance.
The aquatic exercise was performed in a 12m x 6m pool equipped with an elastic-resistant band at Damietta Governate, Egypt. The pool depth and temperature vary from .8 m to 2 m and 28°C to 30°C respectively. During this exercise, the participants must immerse their body up to the xiphoid level. The first rehabilitation stage included 10-12 repetitions of pain-free ROM exercises for hamstring muscle group, where each repetition lasted for 20-30 seconds. After that, the Isometric strengthening exercise was performed within a pain-free range of knee joint motion. This exercise consisted of 3-5 sets of 10 repetitions, and was 8-12 seconds long. Next, the isotonic strengthening exercise was performed over a full range of knee joint motion. This exercise comprised 3-5 sets of 10 repetitions and was maintained for 8-12 seconds. On the third week, the proprioceptive rehabilitation exercise was performed in 3-5 sets with 15-20 repetitions per set. In the second stage, the functional and endurance exercises were performed in 1-2 sets of 3-5 repetitions with 80-90% intensity level of (1RM) one repetition maximum and for three times a week. Nevertheless, Thera-Band resistance bands exercises were used during 8 weeks especially the bands colors (red, blue, black, silver). The red and blue bands were used in the first stage and the black and silver used in the second stage. Furthermore, all the exercises were performed by stretching the band between 75 – 100 %. The weight of stretching in Thera-Band between 75-100% is red 3.3-3.9kg, blue 5.9-7.1kg, black 8.1-9.7, and silver 11.1-13.2kg. All the participant returned to activity after accomplishing the 8 weeks rehabilitation.
2.2. Platelet rich plasma preparation and injection:
In accordance with GPSTM III Systems instruction, the blood collected for PRP was prepared by (Biomet Biologics, Inc., Warsaw, Ind) and standard 60 ml GPSTM III kit. Approximately of 7 ml of PRP was prepared in 30 minutes. Furthermore, single 5-6 ml of extracted PRP were injected under ultrasound gaudiness after adding 8.4% sodium bicarbonate buffered PRP for increasing the pH to normal physiological levels. The sodium was added in a ratio 0.05 ml to 1 ml of PRP. All the participant’s blood samples were stored in -25° Celsius and were analyzed to determine the concentration of the growth factors [30]. Blood was drawn at precisely the same time each morning and at least 3 hours after eating and exercising per WADA standards. The PRP injection of the current study was injected directly into the injured area under aseptic technique. The case group participants only received the single autologous PRP combined with the rehabilitation program. Immediately after injection, the participants were kept in the sleeping position without moving their legs for 60 minutes. The participants were sent home instruction of limit movement and were kept under observation for 96 hours. مرجع كوريا الجنوبية The rehabilitation program were performed after 5-7 days of PRP injection. Blood samples were collected by venipuncture at standardized time points: before (baseline), 4wks., and 8wks. after administration of PRP. Blood was drawn at precisely the same time each morning and at least 3 hours after eating and exercising per WADA standards.
2.3. Data Collection:
Treatment evaluation was performed using the Quantikine enzyme linked immunosorbent assay (ELISA kit), to measure the growth factor concentration. As outlined the Growth factors studied were: human growth hormone (hGH), insulin-like growth factor–1 (IGF-1), basic fibro blast growth factor (FGF-2), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF). [30] [31] [6]. Three basics isotonic force measurements were reported for the knee flexion force by an Isometric Dynamometer device (Isokinetic Dynamometer BiodexMedical Systems, Shirley, New York, 2008). The Pre-test was conducted after 1 day of PRP injection and before the beginning of the rehabilitation program. After four rehabilitative weeks, the Fourth-week test was realized. while the post-test was realized after the eighth rehabilitative week. Moreover, the knee range of motion obtained by Baseline® Metal Goniometers.
2.5. Statistical Analysis
Sphericity and normality assumption were verified using Mauchly’s and Kolgomorov-Smirnoff test respectively. In order to assess the influence of treatment (PRP and rehabilitation) on Growth factors, Knee range of motion, any hamstring strength. measurement repeated measures ANOVA was used with the time as the within-subjects factor while treatment as between-subject’s factors. All statistical analyses were performed using the statistical software IBM SPSS Statistics 23.0 for Windows. Results were obtained from comparisons of between-and within-subject effects. All values within the text and table are observed as Mean and Standard Deviation (mean ± SD). The value of P < 0.05 was used to indicate statistical significance. Moreover, the statistical analysis was based on the intention-to-treat population.
3. Results:
All patients completed the physical rehabilitation interventions without any dropout. The patients in case groups reported local pain started on the day of the PRP injection and subsided gradually. With the exception of the discomfort or aforementioned pain, there were no adverse effects observed during the duration of the study. Moreover, no other complications of either case group or control group were reported.
Both groups showed spectacular significant increases in the Hamstring Force (HF) and Knee Extension range of motion (KE) at 4 and 8 weeks after injury. The case group improvement in the mean HF total scores from 26.62 ± 4.67N at baseline to 104.32 ± 5.67N at 4 weeks and to 107.06±1.64N at 8 weeks (t = 116.633, P= 0.001). The mean HF total scores increased from 25.31 ± 3.41N at baseline to 102.71 ± 4.75N at 4 weeks and to 105.75 ±3.18N at 8 weeks in the control group (t = 91.325, P=0.001). Likewise, the improvement in the mean KE total scores from 51.72 ± 5.17 at baseline to 147.92 ± 0.43 at 4 weeks and to 148.62 ± 0.78 at 8 weeks in the case group (t = 148.315, P= 0.001). While, the mean KE total scores increased from 52.04 ± 2.43 at baseline to 147.02 ± 0.14 at 4 weeks and to 147.36 ± 0.88 at 8 weeks in the control group (t= 117.846, P=0.001). Despite of the significant difference for both group there was not significant difference between the 2-group weather at 4 weeks (t = 1.571, P=0.05) or at 8 weeks (1.680, P=0.05) in the Hamstring Force. Furthermore, there was not significant difference between the 2-group weather at 4 weeks (t = 0.374, P=0.05) or at 8 weeks (1.515, P=0.05) in the Knee Extension range of motion.
Regarding relative improvements in the growth factors concentration, the case group (PRP group) demonstrated better measurements compared with the control group at all measurements intervals. The IGF-1 concentration was s 0.577±0.283 pg/mL at baseline, 0.817 ± 0.844 pg/mL (41.6% improvement) at 4 weeks, and 0. 793 ± 0.141 pg/mL (37.4% improvement) at 8 weeks for the PRP group and 0.582 ± 0.247 pg/mL at baseline, 0.633 ± 0.145 pg/mL (8.8% improvement) at 4 weeks, and 0.637 ± 0.114 pg/mL (9.5% improvement) at 8 weeks for the control group. However, FGF-2 concentration 2.233 ± 1.22 pg/mL at baseline, 3.452 ± 0.567 pg/mL (54.6% improvement) at 4 weeks, and 3.921 ± 0.822 pg/mL (75.6% improvement) at 8 weeks for the PRP group and 2.228 ± 0.721 pg/mL at baseline, 2.593 ± 0.687 pg/mL (16.4% improvement) at 4 weeks, and 2.627 ± 0.514 pg/mL (17.9% improvement) at 8 weeks for the control group. While, the VEGF concentration was 0.346 ± 0.184 pg/mL at baseline, 0.684 ± 0.098 pg/mL (97.6% improvement) at 4 weeks, and 0.549 ± 0.077 pg/mL (58.6% improvement) at 8 weeks for the PRP group and 0.341 ± 0.163 pg/mL at baseline, 0.384 ± 0.187 pg/mL (12.6% improvement) at 4 weeks, and 0.396 ± 0.106 pg/mL (16.1% improvement) at 8 weeks for the control group. The PDGF concentration was 0.352±0.117 pg/mL at baseline, 0.656 ± 0.108 pg/mL (86.4% improvement) at 4 weeks, and 0.507 ± 0.033 pg/mL (44% improvement) at 8 weeks for the PRP group and 0.358 ± 0.121 pg/mL at baseline, 0.421 ± 0.633 pg/mL (17.6% improvement) at 4 weeks, and 0.429 ± 0.078 pg/mL (19.8% improvement) at 8 weeks for the control group.
Pair-wise comparisons revealed rapid change in the case group more than the control. The case group demonstrated measurement at 8 weeks lower than 4 weeks in growth factor concentration. The spectacular significant difference in the growth factor concentration between 4 weeks compared to at 8 weeks in case group was, IGF-1 (t=2.365, P>0.05), FGF-2 (t=4.127, P>0.004), VEGF (t=4.883, P>0.004), and PDGF (t=5.220, P>0.001). Nevertheless, there growth factor was significant difference in the 2 group at 4 and 8 weeks. But there was significant difference between the case group at 4 weeks compared with the control group measurement whether at 4 weeks, IGF-1 (t=24.135, P>0.001), FGF-2 (t=8.887, P>0.001), VEGF (t=3.146, P>0.001), and PDGF (t=6.351, P>0.001) or at 8 weeks IGF-1 (t=21.297, P>0.001), FGF-2 (t=8.677, P>0.001), VEGF (t=7.824, P>0.001), and PDGF (t=4.731, P>0.001).
4. Discussion:
The aim of the study was to determine the effect of PRP in accelerating the healing of hamstring strain. Moreover, to identify potential molecular markers that could be used to distinguish athletes who have been treated with local PRP injections from those who have not. There is little-published evidence to date regarding the growth factors released from combining the PRP injection with rehabilitation exercise. Therefore, the aim of this study was to determine the effects of a single 3 mL injection of autologous PRP combined with a rehabilitation program was effective in the growth factor concentration and time return to play and reducing the severity of pain after an acute grade 2 hamstring injury.
Table 2. Difference of the Growth Factors concentration between the Case and Control group
| Case Group (N=8) | Control Group (N = 9) | ||||||
| Pre-test | 4 weeks | 8 weeks | Pre-test | 4 weeks | 8 weeks | P ≤ 0.05 | |
| hGH pg/mLpg/mL | 1.927 ± 0.67 | 2.321 ± 0.554 | 2.175 ± 0.651 | 1.941 ± 0.201 | 1.997 ± 0.088 | 2.063 ± 0.477 | 1.215 |
| IGF-1 | 0.577±0.283 | 0.817 ± 0.844 | 0. 793 ± 0.141 | 0.582 ± 0.247 | 0.633 ± 0.145 | 0.637 ± 0.114 | 1.760 * |
| FGF-2 | 2.233 ± 1.22 | 3.452 ± 0.567 | 3.921 ± 0.822 | 2.228 ± 0.721 | 2.593 ± 0.687 | 2.627 ± 0.514 | 2.046 * |
| VEGF | 0.346 ± 0.184 | 0.784 ± 0.098 | 0.749 ± 0.077 | 0.341 ± 0.163 | 0.384 ± 0.187 | 0.396 ± 0.106 | 2.584 * |
| PDGF | 0.352±0.117 | 0.856 ± 0.108 | 0.807 ± 0.133 | 0.358 ± 0.121 | 0.421 ± 0.633 | 0.429 ± 0.008 | 2.632 * |
PRP, platelet-rich plasma; hGH, human growth hormone; IGF-1, insulin-like growth factor–1; FGF-2, basic fibroblast growth factor; VEGF, vascular endothelial growth factor; PDGF, platelet-derived growth factor; N, Number; * Significant difference P ≤ 0.05, t =1.740 (N= 17).
Table 3. Difference of Hamstring Force and Knee Flexion (ROM) between the Case and Control group
| Case Group (N=8) | Control Group (N = 9) | |||||||
| Unit | Pre-test | 4 weeks | 8 weeks | Pre-test | 4 weeks | 8 weeks | P ≤ 0.05 | |
| HF | N | 26.62 ± 4.67 | 104.32 ± 5.67 | 107.06±1.64 | 25.31 ± 3.41 | 102.71 ± 4.75 | 105.75 ±3.18 | 0.743 |
| KF(ROM) | Deg. ˚
|
51.72 ± 5.17 | 147.92 ± 0.43 | 148.62 ± 0.78 | 52.04 ± 2.43 | 147.02 ± 0.14 | 147.36 ± 0.88 | 0.632 |
aPRP, platelet-rich plasma; HF, Hamstring Force; KF(ROM), Knee Flexion range of motion. N, Number. P ≤ 0.05, t =1.740 (N= 17).
Figure 5, The concentration of the growth factors after the PRP injection. PRP, platelet-rich plasma; hGH, human growth hormone; IGF-1, insulin-like growth factor–1; FGF-2, basic fibroblast growth factor; VEGF, vascular endothelial growth factor; PDGF, platelet-derived growth factor.
The performance of the growth factors after a single PRP injection was enhanced and increased significantly from 24 until 96 hours. Indeed, hGH was peaked within the 24-hour window, although the results were not significant after 4 weeks or 8 weeks. Similarly, IGF-1 is significantly increased by 24 until 96 hours after PRP, while its’ activation was decreased after 4 weeks and 8 weeks but with significantly difference compared with the pretest and the control group 8 weeks’ test. Furthermore, IGF-1 is generated in the liver in response to hGH, is the primary downstream mediator of hGH, and is the most specific marker of supraphysiological hGH exposure [32] [33]. Despite that both groups performed the same rehabilitation program, our study reported a significant increase in the growth factors for the control group after 4 and 8 weeks (Table 3, figure 6). However, the values of the case group after 4 weeks for the case group were more advanced than the 8 weeks’ values of the controlled (Figure 7,8). Therefore, the PRP injection enhanced the concentration of the growth. It is notably that the physical measurements of hamstring force and knee flexion range of motion were not significant at either 4 or 8 weeks. Wallace et al demonstrated that an acute bout of exercise increases total circulating IGF-1 by only about 20% [34] [8].
Figure 6. The difference between the case and control group in the concentration of the Growth Factors after 8 weeks. hGH, human growth hormone; IGF-1, insulin-like growth factor–1; FGF-2, basic fibroblast growth factor; VEGF, vascular endothelial growth factor; PDGF, platelet-derived growth factor.
4. Discussion:
The aim of the study was to determine the effect of PRP in accelerating the healing of hamstring strain. Moreover, to identify potential molecular markers that could be used to distinguish athletes who have been treated with local PRP injections from those who have not. There is little-published evidence to date regarding the growth factors released from combining the PRP injection with rehabilitation exercise. Therefore, the aim of this study was to determine the effects of a single 3 mL injection of autologous PRP combined with a rehabilitation program was effective in the growth factor concentration and time return to play and reducing the severity of pain after an acute grade 2 hamstring injury.
Two things stand out from the results in the current study. First, it was shown that there were no significant differences between the 2 group in the Hamstring force or Knee extension range of motion whether after 4 or 8 weeks. Secondly, the case group had more growth factor released at 4 weeks than at 8 weeks. By comparison, participants in case group who treated with PRP and exercise program demonstrated a 41% increase at 4-weeks and a 37% in IGF-1, while it was 8.8% at 4 weeks and 9.5% at 8-weeks in control group. Relative to baseline, suggesting that PRP treatment activates the IGF-1 pathway but that a single PRP injection is important to combine with the exercise to maximally stimulate. However, Wallace et al demonstrated that an acute bout of exercise increases total circulating IGF-1 by only about 20% [35] [8] (Figure 6). Our result also observed that FGF-2 had a 54% increase at 4-weeks and a 75% in case group, while it was 16% at 4 weeks and 19% at 8-weeks in control group. One of the hypothesized reasons for this is the b-FGF and IGF-1 were contributed with enhanced muscle regeneration and activated satellite cells. Mosca, Michael J., and Scott A. Rodeo. The Fibroblast growth factors contributes to angiogenesis by stimulating the proliferation of endothelial cells to enhance the proliferation of satellite cells, which are the stem cells of mature muscle [36]. The basic fibroblast growth factor may enhance athletic performance by inducing muscle hyper-trophy and increasing oxygen transport. Nevertheless, there were a spectacular significant deference between the 2 groups in the PDGF and VEGF. The hypothesized reasons for this is the Vascular endothelial growth factor, which a powerful stimulator of angiogenesis and could have noteworthy performance-enhancing effects if it entered the systemic circulation and exerted its effects in tissues other than the site of injury [37]. The potential effects of autologous biological substances to hasten muscle healing were reported in several case reports [30] [38] [39]. However, the concentration of growth factors including PDGF, IGF-), FGF-2, and VEGF are believed to play potentially vital roles in the healing response of soft tissue [40]. The healing benefits of PRP may be correlated with the variation in concentrations of growth factors which may have a differential impact on the natural healing process of muscle compared to other soft tissues. [31]. Furthermore, PDGF and VEGF stimulate fibrosis and thus may have a detrimental effect as it may promote greater fibrotic healing of muscle and stimulate myogenesis and is found in significantly different concentrations in PRP. [40]. The effect of a preparation rich in growth factors (PRGF) to hasten muscle recovery was reported in a 35-year-old professional bodybuilder diagnosed with a right adductor longus rupture. The athlete successfully returned to competitive training within 1 week after the third PRGF injection [39]. The effect of PRP in accelerated and associated a hamstring injury was also observed in the current study. The PRP preparation contained a high concentration of several growth factors including TGF-b, FGF-2, and insulin-like growth factor–1, but the number of platelets and WBCs present was not stated. Additionally, the actual effect of PRP on soft tissue healing is not fully understood,22 our findings supported the possible role of higher growth factors (concentration level) in hastening recovery as postulated by previous researchers [44] [45] [38]. Sanchez et al reported full functional recovery of hamstring and adductor muscle injuries 2 times faster in 20 professional athletes treated with a PRGF [41]. Similarly designed study by Rettig et al has investigated the effects of an autologous PRP injection and was a retrospective case-control study conducted to determine the effect of the PRP on return time to play after acute hamstring injuries. The study included 10 professional National Football League (NFL) players with an acute hamstring injury. The participants were divided equally into PRP and Control groups. Under ultrasound guidance, the PRP group patients were injected once with 6 mL of PRP. Both groups were performed the same rehabilitation program [46].
The current study and Hamid et al [42] study reported that PRP will at best restore athletes to preinjury levels of competition before the control. Recently, Hamilton et al were designed blinded study design with two injections. The study reported the effect of single Platelet-rich plasma and platelet poor plasma for 90 injured athletes with hamstring strain grade I and II. The participants divided equally to three groups. Despite the result shown deference was 5.7 days between PRP and PPP group, 2.9 days between the PRP and no injection group. Nonetheless, there was no significant difference between the three group for the Post-test outcome measures. However, Reurink et al, conducted a randomized controlled study to evaluate the efficacy of PRP injections in acute hamstring injuries in 80 non-professional athletes. The study reported no significant difference between the saline injection and PRP when both were combined with a rehabilitation program. Finally, the PRP injection is a Modern and safe method to cure the soft issues injuries particularly the hamstring strain. Nevertheless, the small number of patients enrolled in the study was limited by the time and cost of PRP therapy. A larger sample size could have allowed a higher effect size better clinical results. Furthermore, Rossi L, et al. reported the effects of an autologous PRP injections on time to return to play in a randomized controlled study conducted on 75 patients. The study represented time to return to play for recreational and competitive athletes and recurrence rate after acute muscle injuries as well. The main result in the study that PRP injection significant reduction of re-injury rates at 2 years. Additionally, it was decreased the pain severity score and significantly decreased the time of return to sports as well [40]. One more study reported that 14 professional athletes were treated with ultrasound-guidance injections of PRP after acute muscle injuries. The athletes showed a quick return to activity and improved healing in muscle tears [7]. Similar results have represented in Sanchez et al study, which conducted on 20 athletes. These results supported the benefits of PRP and its role in muscle healing. The patients recovered in half of the expected time [41].
Figure 8, Difference between the case and control group in (HF) Hamstring Force after 8 weeks.
Nontheless, Borrione et al [30] noted that athletes with grade 3 muscle strains treated with PRP showed earlier functional improvement and a complete recovery than those treated nonoperatively. Hamid et al [42] demonstrated that a single PRP injection was effective in accelerating recovery for grade 2. However, the PRP Group achieved full recovery significantly earlier than controls and returned to play after 27 days while control group returned after 43 days. Another approach successfully treated an athlete with a grade 2 semimembranosus muscle injury with a single 3-mL infiltration of platelet-enriched plasma under ultrasound guidance. The athlete was pain-free and allowed to train at the preinjury intensity 21 days after treatment [43]. Finally, our study showed that a single 3-mL injection of autologous PRP combined with a rehabilitation program was significantly more effective than a control in time return to play after 4 weeks and allowing a significantly after an acute grade 2 hamstring injury. Addition, there is a statistically significant increase in circulating concentrations of VEGF, IGF-1, PDGF and FGF-2 after treatment with a single dose PRP. Furthermore, the results provide biological support for a systemic performance-enhancing effect of PRP.
Acknowledgment:
This study was approved by Department of Sports Health Science, Damietta University, Egypt, and Department of kinesiology and Health science, Utah state university, Logan, UT, USA. Addition it funded by the Egyptian Ministry of High Education. Addition, the author thanks all the participants in this study and all the staff members of the biomechanics lab and Sports Medicine Lab at Utah State University, USA, and Department of Sports Health Science in Damietta University, Egypt, for their assistance while this study was being conducted.
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Table 2. Difference of the Growth Factors concentration between the Case and Control group
| Case Group (N=8) | Control Group (N = 9) | ||||||
| Pre-test | 4 weeks | 8 weeks | Pre-test | 4 weeks | 8 weeks | P ≤ 0.05 | |
| hGH pg/mLpg/mL | 1.927 ± 0.67 | 2.321 ± 0.554 | 2.175 ± 0.651 | 1.941 ± 0.201 | 1.997 ± 0.088 | 2.063 ± 0.477 | 1.215 |
| IGF-1 | 0.577±0.283 | 0.817 ± 0.844 | 0. 793 ± 0.141 | 0.582 ± 0.247 | 0.633 ± 0.145 | 0.637 ± 0.114 | 1.760 * |
| FGF-2 | 2.233 ± 1.22 | 3.452 ± 0.567 | 3.921 ± 0.822 | 2.228 ± 0.721 | 2.593 ± 0.687 | 2.627 ± 0.514 | 2.046 * |
| VEGF | 0.346 ± 0.184 | 0.784 ± 0.098 | 0.749 ± 0.077 | 0.341 ± 0.163 | 0.384 ± 0.187 | 0.396 ± 0.106 | 2.584 * |
| PDGF | 0.352±0.117 | 0.856 ± 0.108 | 0.807 ± 0.133 | 0.358 ± 0.121 | 0.421 ± 0.633 | 0.429 ± 0.008 | 2.632 * |
PRP, platelet-rich plasma; hGH, human growth hormone; IGF-1, insulin-like growth factor–1; FGF-2, basic fibroblast growth factor; VEGF, vascular endothelial growth factor; PDGF, platelet-derived growth factor; N, Number; * Significant difference P ≤ 0.05, t =1.740 (N= 17).
Table 3. Difference of Hamstring Force and Knee Flexion (ROM) between the Case and Control group
| Case Group (N=8) | Control Group (N = 9) | |||||||
| Unit | Pre-test | 4 weeks | 8 weeks | Pre-test | 4 weeks | 8 weeks | P ≤ 0.05 | |
| HF | N | 26.62 ± 4.67 | 104.32 ± 5.67 | 107.06±1.64 | 25.31 ± 3.41 | 102.71 ± 4.75 | 105.75 ±3.18 | 0.743 |
| KF(ROM) | Deg. ˚
|
51.72 ± 5.17 | 147.92 ± 0.43 | 148.62 ± 0.78 | 52.04 ± 2.43 | 147.02 ± 0.14 | 147.36 ± 0.88 | 0.632 |
aPRP, platelet-rich plasma; HF, Hamstring Force; KF(ROM), Knee Flexion range of motion. N, Number. P ≤ 0.05, t =1.740 (N= 17).
