Platelet-Rich Plasma Shortens Return to Play in National Football League Players With Acute Hamstring Injuries

The Role of Platelet-Rich Plasma Injection for Muscle Strains in Athletes

Muscle tears/strains are among the most common musculoskeletal injuries, posing a serious challenge for sports medicine. Aiming to reduce the time to return to play and the rate of reinjuries, apart from the traditional conservative treatments and rehabilitation protocols, new and innovative therapeutic options have emerged, particularly platelet-rich plasma (PRP). This study aims to present the available evidence regarding PRP injection for the treatment of muscle strains in athletes. Two databases were searched for articles published between January 2012 and December 2022 in Portuguese or English. The query used for the PubMed database was ("Muscles/injuries"[Mesh]) AND ("Athletes"[Mesh] OR "Athletic Injuries"[Mesh]) AND "Platelet-Rich Plasma"[Mesh], while for the Web of Science database the search was performed for "Platelet-rich plasma" AND "Muscle injuries" AND ("Athletes" OR "Athletic injuries"). Eleven studies involving athletes diagnosed with muscle injuries who received treatment with PRP injection alone, or in combination with traditional conservative treatment, compared to a control group, were included. Four randomized controlled trials, four systematic reviews/meta-analyses, two retrospective studies, and one comparative study were included. Current evidence from the highest-quality studies does not support the hypothesis of reduction of time to return to play and the rate of reinjuries after PRP injection, even though some studies reported positive results. However, the available evidence suggests that PRP might have a beneficial effect on the pain perceived by athletes following an acute muscle strain. It is challenging to arrive at definitive conclusions and translate these findings into a clinical context for treating muscle strains in athletes. The existing trials present several inconsistencies and limitations, with a heterogeneous set of patients and injuries, as well as the use of different and inconsistent methods for preparing, administering, and measuring the effects of PRP. To achieve consistent outcomes, standardizing PRP administration procedures is essential.

Percutaneous Interventions for Injuries in Athletes: Implications on Return to Play

For nonsurgical musculoskeletal (MSK) injuries in athletes, image-guided percutaneous intervention may aid in recovery and decrease return to play (RTP) time. These interventions fall into two major categories: to reduce inflammation (and therefore alleviate pain) or to promote healing. This review describes the risks and benefits of the various percutaneous interventions in MSK athletic injury and surveys the literature regarding the implication of these interventions on RTP.

Hamstring Injuries: A Current Concepts Review: Evaluation, Nonoperative Treatment, and Surgical Decision Making

The purpose of this current concepts review is to highlight the evaluation and workup of hamstring injuries, nonoperative treatment options, and surgical decision-making based on patient presentation and injury patterns. Hamstring injuries, which are becoming increasingly recognized, affect professional and recreational athletes alike, commonly occurring after forceful eccentric contraction mechanisms. Injuries occur in the proximal tendon at the ischial tuberosity, in the muscle belly substance, or in the distal tendon insertion on the tibia or fibula. Patients may present with ecchymoses, pain, and weakness. Magnetic resonance imaging remains the gold standard for diagnosis and may help guide treatment. Treatment is dictated by the specific tendon(s) injured, tear location, severity, and chronicity. Many hamstring injuries can be successfully managed with nonoperative measures such as activity modification and physical therapy; adjuncts such as platelet-rich plasma injections are currently being investigated. Operative treatment of proximal hamstring injuries, including endoscopic or open approaches, is traditionally reserved for 2-tendon injuries with >2 cm of retraction, 3-tendon injuries, or injuries that do not improve with 6 months of nonoperative management. Acute surgical treatment of proximal hamstring injuries tends to be favorable. Distal hamstring injuries may initially be managed nonoperatively, although biceps femoris injuries are frequently managed surgically, and return to sport may be faster for semitendinosus injuries treated acutely with excision or tendon stripping in high-level athletes.

Leukocyte-poor platelet-rich plasma and leukocyte-rich platelet-rich plasma promote myoblast proliferation through the upregulation of cyclin A, cdk1, and cdk2

Muscle injuries are common among athletes and often treated with platelet-rich plasma (PRP). However, whether the leukocyte concentration affects the efficacy of PRP in treating muscle injuries remains unclear. This study investigated the effects of leukocyte-poor platelet-rich plasma (LP-PRP) and leukocyte-rich platelet-rich plasma (LR-PRP) on myoblast proliferation and the molecular mechanisms underlying these effects. Myoblasts were treated with 0.5% LP-PRP, 0.5% LR-PRP, 1% LP-PRP, or 1% LR-PRP for 24 h. The gene expression of the LP-PRP- and LR-PRP-treated myoblasts was determined using RNA sequencing analysis. Cell proliferation was evaluated using an bromodeoxyuridine (BrdU) assay, and cell cycle progression was assessed through flow cytometry. The expression of cyclin A, cyclin-dependent kinase 1 (cdk1), and cdk2 was examined using Western blotting. The expression of myoblast determination protein 1 (MyoD1) was examined through Western blotting and immunofluorescence staining. The LP-PRP and LR-PRP both promoted the proliferation of myoblasts and increased differential gene expression of myoblasts. Moreover, the LP-PRP and LR-PRP substantially upregulated the expression of cyclin A, cdk1, and cdk2. MyoD1 expression was induced in the LP-PRP and LR-PRP-treated myoblasts. Our results corroborate the finding that LP-PRP and LR-PRP have similar positive effects on myoblast proliferation and MyoD1 expression.

Hamstring Injury Treatments and Management in Athletes: A Systematic Review of the Current Literature

BACKGROUND

The field of sports medicine presents a varied landscape of research on hamstring injuries in athletes, characterized by inconclusive and sometimes conflicting findings on effective treatment and rehabilitation strategies. This discordance prompted the current systematic investigation.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed for conducting the systematic review. Multiple international bibliometric databases (Scopus, PubMed, Web of Science, and Embase) were searched to identify studies evaluating any treatment option for the management of hamstring injuries in athletes. Eligible studies were appraised for quality using Joanna Briggs Institute and Risk of Bias 2 tools.

RESULTS

A total of 30 studies with 1,195 participants were included. Of the reviewed studies, treatments varied from aggressive rehabilitation, platelet-rich plasma (PRP) injections, manual techniques, various exercise protocols to modalities like high-power laser and nonsteroidal anti-inflammatory drugs. Evidence suggested benefits from treatments like extensive muscle lengthening during eccentric actions, progressive agility, and trunk stabilization. PRP injections produced mixed results regarding return to sport and reinjury rates. Stretching exercises, sometimes combined with cryotherapy, showed benefits.

CONCLUSION

Treatments for hamstring injuries exhibit varied efficacy. Although rest, ice, compression, and elevation remains essential for acute management, rehabilitation focusing on muscle strengthening and flexibility is crucial. The potential benefits of PRP injections, especially for chronic cases, require more conclusive research. A comprehensive approach, combining evidence-based practices and patient-centric factors, is vital for effective management and recovery.

LEVEL OF EVIDENCE

Level IV. See Instructions for Authors for a complete description of levels of evidence.

Clinical Applications of PRP: Musculoskeletal Applications, Current Practices and Update

Musculoskeletal tissues are often subjected to deleterious effects stemming from traumatic injuries or degenerative pathologies, which can impede the body's natural repair response. The advent of regenerative medicine has emerged as a promising therapeutic approach in modern patient care. Among the interventions in this cutting-edge field, platelet-rich plasma (PRP) and cell-based therapies, such as mesenchymal stem cells, have garnered significant attention. In this article, we endeavor to provide an overview of the current practices and recent developments in PRP therapy, with a particular emphasis on the clinical applications for musculoskeletal pathologies.

Current Status and Advancements in Platelet-Rich Plasma Therapy

Platelet-rich plasma (PRP) as a treatment modality has been around for the last four decades, but only truly gained popularity over the last 10 to 15 years in medicine, in a variety of fields ranging from regenerative medicine to infertility treatment. It has gained popularity, especially in treating musculoskeletal conditions where the bulk of research has been performed and published. There is level I evidence available supporting its efficacy in the treatment of osteoarthritis (OA), epicondylitis, bursitis, compressive neuropathy, plantar fasciitis, muscular injuries and osteochondral lesions. Most published research with regards to PRP has been focused on knee OA (limited research in shoulder, elbow, and foot and ankle OA), lateral epicondylitis and carpal tunnel syndrome, whereas spinal and hand conditions have limited research available. Tendinopathies and partial tendon tears have conflicting evidence available, with level I evidence supporting PRP's use in rotator cuff tendinopathies and tears, with contradictory level I evidence discouraging its use in patella and Achilles tendinopathies and tears. The available evidence regarding the use of PRP continues to produce conflicting results, but despite this, there is an ongoing increase in the popularity and use of PRP in patients with musculoskeletal conditions.

Effectiveness of Conservative Interventions After Acute Hamstrings Injuries in Athletes: A Living Systematic Review

BACKGROUND

Hamstrings injuries are common in sports and the reinjury risk is high. Despite the extensive literature on hamstrings injuries, the effectiveness of the different conservative (i.e., non-surgical) interventions (i.e., modalities and doses) for the rehabilitation of athletes with acute hamstrings injuries is unclear.

OBJECTIVE

We aimed to compare the effects of different conservative interventions in time to return to sport (TRTS) and/or time to return to full training (TRFT) and reinjury-related outcomes after acute hamstrings injuries in athletes.

DATA SOURCES

We searched CINAHL, Cochrane Library, EMBASE, PubMed, Scopus, SPORTDiscus, and Web of Science databases up to 1 January, 2022, complemented with manual searches, prospective citation tracking, and consultation of external experts.

ELIGIBILITY CRITERIA

The eligibility criteria were multi-arm studies (randomized and non-randomized) that compared conservative treatments of acute hamstrings injuries in athletes.

DATA ANALYSIS

We summarized the characteristics of included studies and conservative interventions and analyzed data for main outcomes (TRTS, TRFT, and rate of reinjuries). The risk of bias was judged using the Cochrane tools. Quality and completeness of reporting of therapeutic exercise programs were appraised with the i-CONTENT tool and the certainty of evidence was judged using the GRADE framework. TRTS and TRFT were analyzed using mean differences and the risk of reinjury with relative risks.

RESULTS

Fourteen studies (12 randomized and two non-randomized) comprising 730 athletes (mostly men with ages between 14 and 49 years) from different sports were included. Nine randomized studies were judged at high risk and three at low risk of bias, and the two non-randomized studies were judged at critical risk of bias. Seven randomized studies compared exercise-based interventions (e.g., L-protocol vs C-protocol), one randomized study compared the use of low-level laser therapy, and three randomized and two non-randomized studies compared injections of platelet-rich plasma to placebo or no injection. These low-level laser therapy and platelet-rich plasma studies complemented their interventions with an exercise program. Only three studies were judged at low overall risk of ineffectiveness (i-CONTENT). No single intervention or combination of interventions proved superior in achieving a faster TRTS/TRFT or reducing the risk of reinjury. Only eccentric lengthening exercises showed limited evidence in allowing a shorter TRFT. The platelet-rich plasma treatment did not consistently reduce the TRFT or have any effect on the risk of new hamstrings injuries. The certainty of evidence was very low for all outcomes and comparisons.

CONCLUSIONS

Available evidence precludes the prioritization of a particular exercise-based intervention for athletes with acute hamstrings injuries, as different exercise-based interventions showed comparable effects on TRTS/TRFT and the risk of reinjuries. Available evidence also does not support the use of platelet-rich plasma or low-level laser therapy in clinical practice. The currently available literature is limited because of the risk of bias, risk of ineffectiveness of exercise protocols (as assessed with the i-CONTENT), and the lack of comparability across existing studies.

CLINICAL TRIAL REGISTRATION

PROSPERO CRD42021268499 and OSF ( https://osf.io/3k4u2/ ).

The Use of Biologics in NFL Athletes: An Expert Consensus of NFL Team Physicians

Background

There is a lack of published information outlining the use of biologics in National Football League (NFL) athletes and limited data to guide biologic treatment strategies.

Purpose

To develop a consensus on the use of biologics among NFL team physicians.

Study Design

Consensus statement.

Methods

A working group of 6 experts convened a consensus process involving NFL team physicians using validated Delphi methodology. Physicians from 32 NFL teams as well as NFL London were invited to take part. This iterative process was used to define statements on the use of biologics in NFL athletes. A recent scoping review exploring biologics in professional athletes was used to inform the first of 3 rounds of surveys, with statements considered under 7 headings: biologics in general, challenges of treating NFL athletes, terminology/nomenclature, autologous blood products, cell-based therapies, guidance for NFL team physicians, and biologic research in the NFL. In addition to rating agreement, experts were encouraged to propose further items or modifications. Predefined criteria were used to refine item lists after each survey. For a consensus within the final round, defined a priori, items were included in the final information set if a minimum of 75% of respondents agreed and fewer than 10% disagreed.

Results

Physicians from 26 NFL teams and NFL London responded to the initial invitation to participate in the Delphi process; 88.9% of participating team physicians completed the round 1 survey, with response rates of 87.5% in round 2 and 95.2% in round 3. After 3 rounds, 47 statements reached a consensus. A consensus was achieved that platelet-rich plasma has a positive impact on patellar tendinopathy and on symptoms in early osteoarthritis but not for other indications. NFL team physicians agreed that while cell therapies have the potential to improve symptoms, the misrepresentation of uncharacterized preparations as "stem cells" has contributed to the widespread use of unproven therapies.

Conclusion

This study established an expert consensus on 47 statements relating to the use of biologics in NFL athletes. In addition to providing clinical guidance for the use of biologics in NFL athletes, this study identified key areas for future focus including the development of athlete education materials.

Sport-Specific Rehabilitation, but Not PRP Injections, Might Reduce the Re-Injury Rate of Muscle Injuries in Professional Soccer Players: A Retrospective Cohort Study

Platelet-rich plasma (PRP) injections are extremely popular in the management of sports injuries in elite athletes. However, data on the use of various administration protocols of PRP are contradictory. The efficacy of platelet-rich plasma in the treatment of muscle injuries in professional soccer players has to be contextualized within the sport-specific rehabilitation program. Despite the questionable role of PRP, a well-structured rehabilitation program is still regarded as the gold standard. We examined the efficacy of various PRP protocols in the management of muscle injuries in professional soccer players in respect to treatment duration and injury recurrence. A retrospective cohort study. Muscle injuries in professional soccer players (n = 79, height 182.1 ± 5.9 cm, weight 76.8 ± 5.8 kg, BMI 23.1 ± 1.4 kg/m2) from three elite soccer clubs from the Russian Premier League were recorded during the 2018−2019 season. The injuries were graded based on MRI, using the British Athletic Muscle Injury Classification. Treatment protocols included the POLICE regimen, short courses of NSAID administration, and the specific rehabilitation program. The sample group of players were administered PRP injections. The average treatment duration with PRP injection was significantly longer than conventional treatment without PRP, 21.5 ± 15.7 days and 15.3 ± 11.1 days, respectively (p = 0.003). Soccer-specific rehabilitation and obtaining MRI/US before the treatment was associated with significantly reduced injury recurrence rate (p < 0.001). There was no significant difference between the PRP injection protocol applied to any muscle and the treatment duration in respect of grade 2A−2B muscle injuries. The total duration of treatment of type 2A−2B injuries was 15 days among all players. In the group receiving local injections of PRP, the total duration of treatment was 18 days; in the group without PRP injections, the treatment duration was 14 days. In our study, PRP treatment was associated with longer treatment duration, regardless of which muscle was injured. This may reflect the tendency to use PRP in higher-degree injuries. Soccer-specific rehabilitation significantly reduced the injury recurrence rate when compared to the administration of PRP injections. MRI/US imaging before returning to play was also associated with a lower injury recurrence rate. There was no significant difference between the PRP injection protocol applied to any muscle and the treatment duration in treatment of type 2A−2B muscle injuries.

Dependence of Electric Pulse Mediated Growth Factor Release on the Platelet Rich Plasma Separation Method

Platelet rich plasma (PRP) has been explored for multiple clinical applications, including dentistry, orthopedics, sports medicine, diabetic foot ulcers, and cosmetic treatments. Topical applications of PRP typically use thrombin to induce platelet activation, which is accompanied by growth factor release and clotting of the PRP, prior to treatment. Injectable PRP treatments typically use non-activated PRP under the assumption that collagen at the site of the injury mediates platelet activation to ensure growth factor release in vivo. Ex-vivo electrical stimulation of platelets is emerging as a robust, easy to use, instrument-based PRP activation technique to facilitate growth factor release with or without clotting, while providing tunability of growth factor release, clot mechanical properties (when desired), and serotonin release from the dense granules. This paper briefly reviews the key results of the electrical activation of platelets and demonstrates successful growth factor release by electrical ex-vivo stimulation without clotting for three types of PRP separated from whole blood using available commercial kits: Harvest, EmCyte and Eclipse. While these three types of PRP feature a wide range of platelet and red blood cell content compared to whole blood, we demonstrate that pulsed electric fields enable growth factor release for all these biological matrices generated using whole blood from four human donors. These experiments open opportunities for using electrically stimulated PRP with released growth factors without clotting for injectable platelet treatments in relevant clinical applications.

Evidence-Based Management and Factors Associated With Return to Play After Acute Hamstring Injury in Athletes: A Systematic Review

Background:

Considering the lengthy recovery and high recurrence risk after a hamstring injury, effective rehabilitation and accurate prognosis are fundamental to timely and safe return to play (RTP) for athletes.

Purpose:

To analyze methods of rehabilitation for acute proximal and muscular hamstring injuries and summarize prognostic factors associated with RTP.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

In August 2020, MEDLINE, CINAHL, Cochrane Central Register of Controlled Trials, and SPORTDiscus were queried for studies examining management and factors affecting RTP after acute hamstring injury. Included were randomized controlled trials, cohort studies, case-control studies, and case series appraising treatment effects on RTP, reinjury rate, strength, flexibility, hamstrings-to-quadriceps ratio, or functional assessment, as well as studies associating clinical and magnetic resonance imaging factors with RTP. Risk of bias was assessed using the Cochrane Risk-of-Bias Tool for Randomized Trials or the Methodological Index for Non-Randomized Studies (MINORS).

Results:

Of 1289 identified articles, 75 were included. The comparative and noncomparative studies earned MINORS scores of 18.8 ± 1.3 and 11.4 ± 3.4, respectively, and 12 of the 17 randomized controlled trials exhibited low risk of bias. Collectively, studies of muscular injury included younger patients and a greater proportion of male athletes compared with studies of proximal injury. Surgery for proximal hamstring ruptures achieved superior outcomes to nonoperative treatment, whereas physiotherapy incorporating eccentric training, progressive agility, and trunk stabilization restored function and hastened RTP after muscular injuries. Platelet-rich plasma injection for muscular injury yielded inconsistent results. The following initial clinical findings were associated with delayed RTP: greater passive knee extension of the uninjured leg, greater knee extension peak torque angle, biceps femoris injury, greater pain at injury and initial examination, “popping” sound, bruising, and pain on resisted knee flexion. Imaging factors associated with delayed RTP included magnetic resonance imaging-positive injury, longer lesion relative to patient height, greater muscle/tendon involvement, complete central tendon or myotendinous junction rupture, and greater number of muscles injured.

Conclusion:

Surgery enabled earlier RTP and improved strength and flexibility for proximal hamstring injuries, while muscular injuries were effectively managed nonoperatively. Rehabilitation and athlete expectations may be managed by considering several suitable prognostic factors derived from initial clinical and imaging examination.

Platelet-Rich Plasma: Fundamentals and Clinical Applications

Platelet-rich plasma (PRP) is perhaps the most widely studied of the biologic therapies, with an ever-growing body of evidence supporting its safety and efficacy in decreasing inflammation and pain and promoting healing in the setting of both nonoperative and operative treatments. PRP is produced by the centrifugation of whole blood, isolating its constituent parts based on their unique densities. These density gradients can be selectively harvested so as to obtain different concentrations of various blood product components, such as platelets and leukocytes. A precise and consistent method for describing the essential characteristics of different PRP formulations is critical for both practical and research purposes. The concentration of platelets, method of activation, and the total number of red blood cells (RBCs), white blood cells (WBCs), and neutrophils relative to baseline values are all of particular importance in accurately describing a PRP formulation. The biologic activity of PRP is manifold: platelet α granules promote the release of various growth factors, including vascular endothelial growth factor and tissue growth factor β, while inflammation is modulated through inhibition of the nuclear factor-κB pathway. PRP has been convincingly shown to be efficacious in the setting of patellar tendinopathies, knee osteoarthritis, and lateral epicondylitis. In fact, several recent randomized controlled trials have demonstrated the superiority of PRP over both corticosteroids and hyaluronic acid in treating knee OA-related symptoms. There is also substantial promise for the utility of PRP in treating partial hamstring tears and as an adjunct to rotator cuff (RC) repair, especially in the setting of small- to medium-sized tears, where it appears to exert substantial analgesic effects and promote enhanced rates of RC repair healing.

Biologics in professional and Olympic sport: a scoping review

AIMS

The aim of this study was to prepare a scoping review to investigate the use of biologic therapies in the treatment of musculoskeletal injuries in professional and Olympic athletes.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews and Arksey and O'Malley frameworks were followed. A three-step search strategy identified relevant published primary and secondary studies, as well as grey literature. The identified studies were screened with criteria for inclusion comprising clinical studies evaluating the use of biologic therapies in professional and Olympic athletes, systematic reviews, consensus statements, and conference proceedings. Data were extracted using a standardized tool to form a descriptive analysis and a thematic summary.

RESULTS

A total of 202 studies were initially identified, and 35 met criteria for the scoping review; 33 (94.3%) were published within the last eight years, and 18 (51.4%) originated from the USA. Platelet rich plasma was the most studied biologic therapy, being evaluated in 33 (94.3%) studies. Ulnar collateral ligament and hamstring injuries were the conditions most studied (nine (25.7%) studies and seven (20.0%) studies, respectively). Athletes most frequently participated in baseball, soccer, and American football. Only two (5.7%) studies were level 1 evidence, with interpretation and comparison between studies limited by the variations in the injury profile, biologic preparations, and rehabilitation protocols.

CONCLUSION

There is diverse use of biologic therapies in the management of musculoskeletal injuries in professional and Olympic athletes. There is currently insufficient high-level evidence to support the widespread use of biologic therapies in athletes. Further research priorities include the development of condition/pathology-specific preparations of biologic therapies, and of outcome measures and imaging modalities sufficiently sensitive to detect differences in outcomes, should they exist. Cite this article: Bone Joint J 2021;103-B(7):1189-1196.

Electrical stimulation of whole blood for growth factor release and potential clinical implications

Clinicians have increasingly applied platelet-rich plasma (PRP) for wound healing treatments. Topical treatments commonly require biochemical agents such as bovine thrombin to activate PRP ex vivo for clotting and growth factor release to facilitate healing upon application to the wound of interest. Recent studies have explored electrical stimulation as an alternative to bovine thrombin for PRP activation due to the former's cost, workflow complexity and potentially significant side effects; however, both approaches require separating the PRP from whole blood (WB) prior to activation. Eliminating the separation (typically centrifugation) step would reduce the cost and duration of the clinical procedure, which may be critical in trauma and surgical applications. We hypothesize that electric pulses (EPs) can release growth factors from WB, as they do from PRP, without requiring centrifugation of WB into PRP. A pilot study for two donors demonstrates the potential for EP stimulated growth factor release from WB. This motivates future experiments assessing EP parameter optimization for WB activation and in vivo studies to determine the clinical benefits for topical treatments and, especially, for injections in orthopedic applications that already utilize non-treated/non-activated WB.