Platelet-rich plasma: the PAW classification system

Standardization and validation of a conventional high yield platelet-rich plasma preparation protocol

BACKGROUND

Of late, numerous randomised controlled trials report platelet-rich plasma (PRP) to be ineffective with preparation protocols of low platelet yield despite using expensive commercial PRP kits.

OBJECTIVE

This study aims to identify and standardize a preparation protocol for PRP with maximum platelets yield and concentration to obtain favourable results without the use of commercial preparation kits.

MATERIALS & METHODS

Blood samples were collected from 40 healthy volunteers who signed informed consent for participation in the study. The double spin protocol of PRP preparation was analyzed for variables such as centrifugal acceleration, time, and volume of blood processed and final product utilized. The final PRP prepared was investigated for platelet recovery, concentration, integrity, and viability. Each protocol investigated with technical and biological duplicates to avoid reporting and sampling bias.

RESULTS

We noted maximum platelet recovery (86-99%) with a consistent 6.4 ± 0.8 times the baseline concentration of platelets with first centrifugation at 100g for 15 min followed by second centrifugation at 1600g for 20 min. We did not note a loss of integrity or viability of the platelets in the final product from the above-said protocol. We also validated the protocol among all the study participants demonstrating consistency.

CONCLUSION

The preparation of PRP by the double-spin protocol using 10 ml of blood at 100 g followed by 1600 g for 15 and 20 min respectively in a 15 ml tube and using the lower 1/3rd of the final product demonstrated consistent high platelet recovery (86-99%) and concentration (6x) without disturbing the platelet integrity or viability.

Are leukocyte-poor or multiple injections of platelet-rich plasma more effective than hyaluronic acid for knee osteoarthritis? A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

Platelet-rich plasma (PRP) has gained popularity as a treatment option for knee osteoarthritis; however, its efficacy remains controversial. The optimal leukocyte concentration and number of injections have not been well investigated. This study was, therefore, designed to provide clinical evidence on the leukocyte concentration and number of intra-articular injections of PRP via a meta-analysis of randomized controlled trials (RCTs).

METHODS

The MEDLINE, Embase, Cochrane Library, CINAHL, and Scopus databases were searched and RCTs comparing PRP and hyaluronic acid (HA) for treating knee osteoarthritis were included. Clinical outcomes, including visual analog scale (VAS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and adverse reactions, were evaluated.

RESULTS

A total of 138 studies were screened, of which 21 level 1 RCTs (2086 knees; 1077 PRP and 1009 HA) were included. PRPs showed significant improvement in pain according to the VAS score compared to HA at 6 and 12 months, regardless of leukocyte concentration. Both single and multiple injections of PRP improved pain better than HA at 12 months. Regarding function, both single and multiple injections of leukocyte-poor PRP and leukocyte-rich PRP led to significantly better improvement in total WOMAC score compared with HA at 6 months. There was no significant difference in procedure-related knee pain or swelling between the PRP and HA groups. Leukocyte-rich PRP had a significantly higher odds ratio for procedure-related knee pain or swelling compared to HA (odds ratio, 3.3 [95% confidence interval, 1.1-10.2], P = .037).

CONCLUSION

Based on evidence from Level 1 studies, intra-articular injection of PRP improves pain and function in patients with knee osteoarthritis for up to 12 months and is superior to HA, regardless of leukocyte concentration or number of injections. The findings of this study support the routine clinical use of intra-articular injections of PRP for the treatment of knee osteoarthritis, regardless of the type and frequency of PRP injection.

LEVEL OF EVIDENCE

Meta-analysis of level I studies.

Autologous platelet concentrates for facial rejuvenation

Autologous platelet concentrates (APCs) are promising therapeutic agents in facial rejuvenation since they are a great source of cytokines, growth factors and other biologically active substances. Obtained from the patient’s blood, they have the advantages of reducing immunological reactions, making the procedure safer, well tolerated, with minimal adverse effects and lower cost. Currently, they are used for facial rejuvenation both in combination with microneedling and in mesotherapy techniques, as well as to treat facial acne scars, melasma and wounds after laser ablative treatments. This review summarizes current knowledge on the use of APCs, ranging from basic concepts related to their composition and mechanisms of action to up-to-date information on their clinical efficacy.

Current Trends in Orthobiologics: An 11-Year Review of the Orthopaedic Literature

BACKGROUND

The use of "orthobiologics" or regenerative therapies in orthopaedic surgery has grown in recent years. Particular interest has been raised with regard to platelet-rich plasma, bone marrow aspirate, adipose-derived cells, and amniotic cells. Although studies have analyzed outcomes after orthobiologic treatment, no study has analyzed how the literature as a whole has evolved.

PURPOSE

To evaluate trends in platelet-rich plasma, bone marrow aspirate, adipose-derived cells, and amniotic cell publications and to assess how these might inform efforts to establish minimum reporting standards and forecast future use.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A database was compiled systematically using PubMed to identify articles published between 2009 and 2019 within 9 prominent orthopaedic journals and pertaining to the use of platelet-rich plasma, bone marrow aspirate, adipose-derived cells, and amniotic cells in the treatment of musculoskeletal conditions. Included articles were classified as clinical, nonclinical (translational or basic science), or review, and a variety of study parameters were recorded for each. Additional queries were performed to identify articles that utilized minimum reporting standards.

RESULTS

A total of 474 articles (132 clinical, 271 nonclinical, 71 review) were included, consisting of 244 (51.5%) platelet-rich plasma, 146 (30.8%) bone marrow aspirate, 72 (15.2%) adipose-derived cells, and 12 (2.5%) amniotic cells. The greatest annual increase in publications for each orthobiologic topic was from 2018 to 2019. The American Journal of Sports Medicine demonstrated the highest number of overall (34.2%) and clinical (50.0%) publications, and accounted for 44.3% of all platelet-rich plasma publications. The Journal of Orthopaedic Research accounted for the second highest overall number of publications (24.9%) and highest nonclinical publications (41.0%). Platelet-rich plasma accounted for 91.5% of all level 1 clinical studies, while much greater than half of bone marrow aspirate, adipose-derived cells, and amniotic cell publications were level 3 or lower. Out of the 207 articles that used some form of reporting protocol, 59 (28.5%) used an established algorithm and 125 (60.4%) used their own.

CONCLUSION

Interest in orthobiologics continues to grow, as evidenced by an increasing trend in publications over an 11-year period. However, current reporting on orthobiologic formulations is largely heterogeneous, emphasizing the need for minimum reporting standards and higher-quality studies.

The Effectiveness of Plasma Rich in Growth Factors (PRGF) in the Treatment of Nerve Compression Syndromes of the Upper Extremity: A Retrospective Observational Clinical Study

Background: Nerve compression syndromes of the upper extremity are a common cause of neuropathic pain and functional impairment. Recently, platelet-rich plasma (PRP) infiltrations have emerged as an effective biological approach to the treatment of this type of injury. The objectives of this retrospective observational study were to assess clinical improvement in patients with median and ulnar nerve entrapment syndrome after undergoing biologically-assisted nerve release surgery with plasma-rich-in-growth-factors (PRGF) technology. Methods: Participants (n = 39) with moderate-to-severe nerve compression syndrome of the upper limb diagnosed by both electromyography and clinical examination, and who were treated with PRGF, were identified from the center’s medical records. The evaluation was based on patient-reported outcomes. Pre- and post-treatment differences in the Visual analog scale (VAS), the Boston carpal tunnel questionnaire (BCTQ), and the Quick-DASH score were assessed. Results: Three study groups were conducted: patients with carpal tunnel syndrome (n = 16), with recurrent carpal tunnel syndrome (n = 8), and with ulnar nerve entrapment (n = 15). The median follow-up was 12 months (interquartile range (IQR), 9−16). In comparison to pre-treatment values, all three study groups obtained statistically significant improvements for the three analyzed scales at the end of the follow-up, with p < 0.001 for all scales in the carpal tunnel syndrome and ulnar nerve entrapment groups and p < 0.01 for all scales in the recurrent carpal tunnel syndrome group. There were no serious adverse effects in the analyzed patients. Conclusion: PRGF-assisted open surgical nerve release treatment (intraneural and perineural liquid PRGF infiltrations and nerve wrapping with PRGF membrane) exerts long-term beneficial effects on pain reduction and functional improvement in the nerve and nerve−muscle unit in patients with upper extremity compression syndromes.

Swiss Medical Devices for Autologous Regenerative Medicine: From Innovation to Clinical Validation

Regenerative medicine, based on the use of autologous tissues and embryonic, stem or differentiated cells, is gaining growing interest. However, their preparation, in a manner compliant with good practices and health regulations, is a technical challenge. The aim of this manuscript is to present the design of reliable CE marked medical devices for the preparation of standardized platelet-rich plasma (PRP) and other autologous biologics intended for therapeutic uses. There are numerous PRP isolation processes. Depending on the methodology used, PRP composition varies greatly in terms of platelet concentration, platelet quality, and level of contamination with red and white blood cells. This variability in PRP composition might affect the clinical outcomes. The devices presented here are based on a specific technology, patented all over the world, that allows the precise separation of blood components as a function of their density using thixotropic separator gels in closed systems. This allows the preparation, in an automated manner, of leukocyte poor PRP with a standardized composition. Production of different forms of PRP is a clinical asset to suit various therapeutic needs. Therefore, we are offering solutions to prepare PRP either in liquid or gel form, and PRP combined with hyaluronic acid. These biologics have been successfully used in many different therapeutic domains, resulting in more than 150 published clinical studies. We also developed the CuteCell technology platform for cell culture expansion for further autologous cell therapies. This technology enables the safe and rapid in vitro expansion of cells intended for therapeutic use in good manufacturing practices (GMP) and autologous conditions, using blood-derived products as culture media supplementation. We summarize in this article our 20 years’ experience of research and development for the design of PRP devices and, more recently, for PRP combined with hyaluronic acid.

Platelet-Rich Plasma Is Not Associated With Improved Outcomes Following Hip Femoroacetabular Impingement Surgery: Very Low-Quality Evidence Suggests Hyaluronic Acid and Cell-Based Therapies May Be Beneficial—A Systematic Review of Biological Treatments

Purpose

To examine the efficacy of biologic agents in the treatment of cartilage defects associated with femoroacetabular impingement (FAI).

Methods

PubMed, Ovid MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews were reviewed by 2 independent reviewers for eligible studies. We included randomized and nonrandomized control trials as well as uncontrolled case series and retrospective studies. Studies were excluded if they included injections of corticosteroids, papers that described technique only, review papers, and those not in the English language. Demographics, treatment type, outcome of treatment, and complications were extracted, whereas risk of bias and study quality were assessed independently using the risk of bias tool (ROB2) and effective public health practice project tool. A narrative synthesis was performed, and standardized mean differences were reported. Certainty of evidence was assessed using the GRADE approach.

Results

Eighteen studies consisting of 1,024 patients met the inclusion criteria. Three studies involved the use of platelet-rich plasma (PRP) as an adjuvant to surgery and were included in the meta-analysis. Three studies administered hyaluronic acid (HA) as a primary treatment. Twelve involved various cell-based methods of chondrocyte stimulation for cartilage defects associated with FAI, but heterogeneity did not allow for pooling. Low-quality evidence indicates PRP is not associated with improved outcomes following surgery (mean difference –1.42, 95% confidence interval –3.95 to 1.11, P = .27). Very-low-quality evidence suggests HA (standardized mean difference 1.15, 95% confidence interval 0.64-1.66, P < .001, Z = 4.39) and cell-based therapies may improve function and pain in patients with FAI.

Conclusions

Low-quality evidence indicates PRP is not associated with improved outcomes following hip FAI surgery, and very-low-quality evidence suggests HA and cell-based therapies may improve outcomes.

Level of Evidence

systematic review of Level I-V studies.

The Effect of Platelet-Rich Plasma Injection on Short Term Vocal Outcomes Following Phonosurgery-A Pilot Study

Background and Objectives: The efficiency and optimal voice rest period following phonosurgery remains debatable. Platelet-rich plasma (PRP) is a safe and cheap alternative to many bioactive agents being studied on animal models, and is already in use in many medical areas. We investigate the short-term effects of PRP and voice rest on voice outcomes following phonosurgery as an alternative to voice rest alone. Materials and Methods: A prospective single-blinded pilot study was conducted. Sixteen patients with a diagnosis of vocal fold cyst and polyps were included, forming equal groups (PRP and voice rest vs. voice rest alone). Voice analysis was carried out on the preoperative day, day three, and week three following surgery. The measured parameters were fundamental frequency (F0), noise–signal ratio (NSR), harmonic poverty (HP), attack alteration (AL), pitch instability (PI), and amplitude instability (AI).VHI(Voice Handicap Index)-30 questionnaires were carried out before surgery and three weeks following surgery to assess the impact of subjective voice change on quality of life. PRP was obtained using commercial kits with separator gel. Results: An average 3.68-fold increase in platelets was obtained with PRP. No side effects were noted after injection. All voice parameters improved on day three and week three following surgery. Statistical significance was noted only in the fundamental frequency of male patients (p = 0.048) in favor of the PRP-voice rest group. In addition, the VHI- 30 questionnaire results between preoperative and postoperative assessments showed statistically significant differences in total VHI score (p = 0.02) as well as the physical (p = 0.05) and emotional (p = 0.02) scale in favor of the PRP-voice rest group. Conclusions: PRP presents short term safety in patients who undergo phonosurgery, although long-term outcomes are unknown. PRP and voice rest are superior to voice rest alone when considering subjective assessment of the voice. When analyzing acoustic parameters, PRP and voice rest are not superior to voice rest alone.

Content of blood cell components, inflammatory cytokines and growth factors in autologous platelet-rich plasma obtained by various methods

BACKGROUND

The evaluation of the efficacy of platelet-rich plasma (PRP) in clinical practice yields conflicting results and raises numerous controversies. This may be due to different concentrations of biologically active components in PRP obtained with the use of different methods of gravity separation.

AIM

To compare the content, repeatability and correlations between biologically active components in PRP obtained with four different commercial systems.

METHODS

From a whole blood sample of each of 12 healthy male volunteers, 4 PRP samples were prepared using 4 different commercial kits [Arthrex Autologous Conditioned Plasma (ACP), Mini GPS III, Xerthra, Dr. PRP] in accordance with the instructions provided by the manufacturers. A comparative analysis of blood cell components - 13 selected inflammatory cytokines and 7 growth factors - in the obtained PRP samples was performed using the Kruskal-Wallis test by ranks. The repeatability of results in each method was evaluated by the estimation of the coefficient of variation. The Spearman correlation was used to estimate the relationship between blood cell content and cytokines.

RESULTS

Significantly higher concentrations of platelets (PLT), white blood cells (WBC) and red blood cells (RBC) were found in PRP obtained with the use of Mini GPS III than in PRP obtained using other systems. Significant differences in the content of growth factors and cytokines in PRP were found. A positive correlation of the amount of PLT, RBC and WBC with the concentration of most of the growth factors was found but in only three inflammatory cytokines. The obtained correlations between blood cell components and cytokines differed between the systems in terms of statistical significance, which may be due to insufficient sample size. The repeatability of the obtained PLT concentration also varied between protocols with the lowest in Xerthra and the highest in Arthrex ACP.

CONCLUSION

Significant differences in the content of biologically active components and their repeatability were found in PRP obtained by various methods, providing new data for further research.

Assessment of Characteristics and Methodological Quality of the Top 50 Most Cited Articles on Platelet-Rich Plasma in Musculoskeletal Medicine

Background:

The wide range of clinical applications and controversial scientific evidence associated with platelet-rich plasma (PRP) therapy in musculoskeletal medicine requires an examination of the most commonly cited studies within this field.

Purpose:

To identify the 50 most cited articles on PRP, assess their study design, and determine any correlations between the number of citations and level of evidence (LoE) or methodological quality.

Study Design:

Cross-sectional study.

Methods:

The Web of Science database was queried to identify the top 50 most cited articles on PRP in orthopaedic surgery. Bibliometric characteristics, number of citations, and LoE were recorded. Methodological quality was evaluated using the Modified Coleman Methodology Score (MCMS), Methodological Index for Non-randomized Studies (MINORS), and Minimum Information for Studies Evaluating Biologics in Orthopaedics (MIBO). The Pearson correlation coefficient and Spearman correlation coefficient (r_S) were used to determine the degree of correlation between the number of citations or citation density and LoE, MCMS, MINORS score, and MIBO score. Student t tests were performed for 2-group comparisons.

Results:

The top 50 articles were published between 2005 and 2016 in 21 journals. The mean number of citations and citation density were 241 ± 94 (range, 151-625) and 23 ± 8, respectively, and the mean LoE was 2.44 ± 1.67, with 15 studies classified as LoE 1. The mean MCMS, MINORS score, and MIBO score were 66.9 ± 12.6, 16 ± 4.7, and 12.4 ± 3.7, respectively. No correlation was observed between the number of citations or citation density and LoE, MCMS, MINORS score, and MIBO score. A significant difference (P = .02) was noted in LoE in articles from the United States (3.56 ± 1.7) versus outside the United States (2 ± 1.5). Seven of the 8 in vivo studies were published between 2005 and 2010, whereas 19 of the 25 clinical outcome investigations were published between 2011 and 2016. Studies that were published more recently were found to significantly correlate with number of citations (r_S = –0.38; P = .01), citation density (r_S = 0.36; P = .01), and higher LoE (r_S = 0.47; P = .01).

Conclusion:

The top 50 most cited articles on PRP consisted of high LoE and fair methodological quality. There was a temporal shift in research from in vivo animal studies toward investigations focused on clinical outcomes.

Platelet-Rich Plasma as an Orthobiologic: Clinically Relevant Considerations

Platelet-rich plasma (PRP) is an autologous blood-derived product processed to concentrate platelets and the associated growth factors. PRP has been shown to be relatively well-tolerated and safe to use for a number of conditions in humans, equines, and canines. There are multiple commercial systems that have been validated for canine use. These systems use a variety of methodologies to produce a PRP product. However, PRP products have been shown to differ greatly between systems. Further study is needed to fully elucidate optimal component concentrations for various indications.

Overview of the Effect of Different Regenerative Materials in Class II Furcation Defects in Periodontal Patients

The aim of this review was to give an overview of the outcomes of the use of different regenerative materials to treat molars with class II furcation defects in patients with periodontitis in comparison with open flap debridement (OFD). A search of five databases (PubMed-Medline, Embase, Cochrane, Scopus and Web of Science) was conducted up to and including January 2022. According to the PICOS guidelines, only randomized control trials (S) considering periodontal patients with at least one molar with a class II furcation involvement (P) treated with regenerative materials (I) in comparison to OFD as control treatment (C) and a minimum follow-up period of 6 months were included. Vertical clinical attachment level (VCAL) was considered as the primary outcome (O), while horizontal clinical attachment level (HCAL), horizontal probing depth (HPD) and vertical probing depth (VPD) were considered as secondary outcomes. The search through the databases initially identified 1315 articles. Only 25 of them met the eligibility criteria and were included. The studies were grouped in four macro-categories according to the material used: absorbable and non-absorbable membranes, blood derivatives and a combination of different materials. The greater part of the included studies reported a statistically significant difference in using regenerative materials when compared to OFD. The blood derivatives groups reported a range of mean changes in VCAL of 0.86–4.6 mm, absorbable membrane groups reported −0.6–3.75 mm, non-absorbable membranes groups reported −2.47–4.1 mm, multiple materials groups reported −1.5–4.87 mm and enamel matrix derivatives reported a mean change in VCAL of 1.45 mm. OFD showed a range of mean VCAL changes of −1.86–2.81 mm. Although no statistical analysis was performed, the use of regenerative materials may be considered moderately beneficial in the treatment of molars with grade II furcation involvement. However, the substantial heterogeneity in the protocols’ design does not allow us to draw definitive conclusions. In addition, low levels of evidence for morbidity and patient-centered outcomes were reported.

Clinical Response After Treatment of Knee Osteoarthritis With a Standardized, Closed-System, Low-Cost Platelet-Rich Plasma Product: 1-Year Outcomes

Background:

Intra-articular infiltration of platelet-rich plasma (PRP) is an alternative therapeutic option to classic hyaluronic acid for the treatment of symptomatic knee osteoarthritis (KOA). However, variation in preparation methods and quality assessment of PRP makes the study of its real clinical efficacy difficult.

Purpose:

To (1) evaluate the clinical efficacy of a characterized PRP product prepared in a standardized manner and in a closed-system for the treatment of KOA and to (2) evaluate the association of the clinical response to PRP-related variables.

Study Design:

Case series; Level of evidence, 4.

Methods:

We recruited 130 patients with nonoperative KOA and evaluated them for 1 year. PRP was prepared from a donation of autologous blood, obtaining 3 aliquots of approximately 10mL of product, which were frozen, allowing platelet disruption, platelet factor release, and long-term storage, until administration. Patients were treated 3 consecutive times every 4 weeks with an intra-articular PRP knee injection under sterile conditions. Complete blood count was performed on the whole-blood sample and the processed PRP before freezing it, for product quality assessment. Patients were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and basic satisfaction scale at 3 months, 6 months, and 1 year after intervention.

Results:

Quality assessment confirmed a leukocyte-poor PRP product (white blood cell count, 0.09 ± 0.09 × 10⁹/L) with a high platelet purity (platelet count, 630.86 ± 191.75 × 10⁹/L). WOMAC scores improved, and basic satisfaction was achieved in 70% of patients. No adverse events were reported. No correlations were observed between PRP quality parameters and clinical results. PRP complete treatment production costs were €108/US$125 (€36/US$41.6 per injection).

Conclusion:

This standardized PRP production method resulted in improved WOMAC scores at 1 year postoperatively in 70% of patients with KOA. This technique was safe and affordable and ensured consecutive infiltrations with the same product to each patient.

Platelet-Rich Plasma-Releasate (PRPr) for the Treatment of Discogenic Low Back Pain Patients: Long-Term Follow-Up Survey

Background and Objectives: Clinical studies of platelet-rich plasma (PRP) for the treatment of low back pain (LBP) have been reported; however, less is known about its long-term efficiency. Materials and Methods: This study was a long-term follow-up of a previous prospective clinical feasibility study for the use of PRP releasate (PRPr) to treat discogenic LBP patients. Among 14 patients, 11 patients were evaluated for a long-term survey. The efficacy was assessed by a visual analogue scale (VAS) for LBP intensity and the Roland-Morris Disability Questionnaire (RDQ) for LBP-related disability. Radiographic disc height was evaluated for seven patients. Results: Improvements in VAS and RDQ were sustained at an average of 5.9 years after the intradiscal injection of PRPr (p < 0.01 vs. baseline, respectively). Clinically meaningful improvements (more than 30% decrease from baseline) in VAS and RDQ were identified in 91% of patients at final survey. The radiographic measurement of disc height of PRPr-injected discs showed a mild decrease (13.8% decrease compared to baseline) during the average 5.9 years. Conclusions: The results of this study with a small number of patients suggest that the intradiscal injection of PRPr has a safe and efficacious effect on LBP improvement for more than 5 years after treatment. Further large-scale studies would be needed to confirm the clinical evidence for the use of PRPr for the treatment of patients with discogenic LBP.

Patellar Tendinopathy: Critical Analysis Review of Current Nonoperative Treatments

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Patellar tendinopathy is an attritional injury of the patellar tendon that is frequently identified in jumping athletes. Through repetitive or explosive movements, considerable loads and high peak strains are generated across the patellar tendon.

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This leads to microinjury of tendon fibers, local mucoid degeneration, and loss of the fibrocartilaginous tissue that attaches tendon to bone.

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Management of patellar tendinopathy often begins with nonoperative modalities: progressive tendon loading and eccentric rehabilitative exercise programs are the most effective. While a variety of additional treatment modalities are available, the comparative efficacy of these supportive treatments is not well differentiated at this time.

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In this article, we analyze the existing literature regarding nonoperative treatment of patellar tendinopathy and provide additional insight on the effectiveness of current modalities.

The effect of leucocyte concentration of platelet-rich plasma on outcomes in patients with lateral epicondylitis: a systematic review and meta-analysis

HYPOTHESIS

The concentration of leukocytes influences the quality of platelet-rich plasma (PRP). However, there is no consensus on which type of PRP based on the concentration of leukocytes is the best for lateral epicondylitis (LE).

METHODS

We systematically searched the MEDLINE, Embase, and Cochrane Library databases until March 1, 2020. Studies involving randomized controlled trials, patients with LE, and treatment with PRP injections were included. PRP was classified into leukocyte-poor (LP) PRP and leukocyte-rich (LR) PRP. LR-PRP was defined as PRP with a white blood cell concentration exceeding that of whole blood (4.0-10.0 per μL³), whereas LP-PRP was defined as PRP with a lower white blood cell concentration than that of whole blood. The efficacy of PRP was assessed using the visual analog scale (VAS) and success rates.

RESULTS

Eleven randomized controlled trials (six involving LP-PRP and five involving LR-PRP) were eligible for inclusion in this review. Eight studies were included in the meta-analysis to evaluate the VAS score. Regarding short-term follow-up, there was no difference in the VAS scores between the LP-PRP and control groups (standard mean difference [SMD], 0.01; 95% confidence interval [CI], -0.29 to 0.30; P = 0.97), with no heterogeneity (I² = 0%). There was also no difference in the VAS scores between the LR-PRP and control groups (SMD, -0.19; 95% CI, -0.57 to 0.20; P = 0.34), with substantial heterogeneity (I² = 56.7%). Regarding long-term follow-up, there was no difference in the VAS scores between the LP-PRP and control groups (SMD, -0.73; 95% CI, -1.69 to 0.23; P = 0.134) with substantial heterogeneity (I² = 88.4%). The LR-PRP group had lower VAS scores than the control group (SMD, -1.06; 95% CI, -2.02 to -0.09; P = 0.032) with substantial heterogeneity (I² = 92%). In the LP-PRP group, there was no significant difference in the success rate (odds ratio, 1.08; 95% CI, 0.07-16.47; P = 0.956) with substantial heterogeneity (I² = 87.7%). In the LR-PRP group, however, the patients who received PRP had a higher success rate than those in the control group (odds ratio, 2.85; 95% CI, 1.67-4.85; P < 0.01) with substantial heterogeneity (I² = 82.9%).

CONCLUSION

LR-PRP may provide pain relief and successful outcomes for patients with LE compared with alternative local injections. Better results were observed with the use of LR-PRP than with the use of LP-PRP.

Comparison effects of platelet-rich plasma on healing of infected and non-infected excision wounds by the modulation of the expression of inflammatory mediators: experimental research

INTRODUCTION

Microbial invasion in soft tissue is believed to cause infectious wounds and increase healthcare costs, anxiety, and distress. The current study was conducted to evaluate the effects of topical use of platelet-rich plasma (PRP) on infected wound-healing process in rats.

METHODS

Following the induction of a circular wound, the animals were divided into three groups, including (1) standard control: infected wounds treated with mupirocin (SDCL), (2) non-infected wounds treated with PRP (PRP), and (3) infected group in which the rats were infected with Staphylococcus epidermidis and Pseudomonas aeruginosa and treated with PRP (INF + PRP). To evaluate the effects of PRP on the wound-healing rate, total bacterial count, histopathological assessment, the serum concentrations of sialic acid, C-reactive protein, haptoglobin, and fibrinogen were assessed. Additionally, IL-1β, IL-6, TNF-α, IL-3, NF-κB, iNOS, PDGF, and EGF mRNA level expressions were assessed employing the qRT-PCR method.

RESULTS

The results indicated that topical application of PRP could significantly decrease total bacterial count, the level of C-reactive protein, and pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) compared to the SDCL group. The administration of PRP also promoted re-epithelization rate by increasing the expression of EGF mRNA level.

CONCLUSION

We could recommend the use of PRP for the treatment of infected wounds owing to its efficiency in decreasing colonization of tissue bacteria, tissue inflammation, and stimulating wound heal-up.

The Efficacy of Platelet-Rich Plasma for Ligament Injuries: A Systematic Review of Basic Science Literature With Protocol Quality Assessment

Background:

Despite the existence of many clinical studies on platelet-rich plasma (PRP) interventions for ligamentous pathology, basic science consensus regarding the indications, mechanisms, and optimal composition of PRP for treating ligament injuries is lacking.

Purpose:

To (1) compare the efficacy of PRP in animal models of ligament injury with placebo and (2) describe the potential variability in PRP preparation using accepted classification systems.

Study Design:

Systematic review.

Methods:

The Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, PubMed, Embase, and Ovid MEDLINE were queried in April 2020 for in vivo and in vitro basic science studies regarding PRP use for ligament injury. Study design, results, PRP composition, and analyzed cellular and molecular markers were extracted, and outcomes relative to control models were documented. Bias was assessed using the SYRCLE risk-of-bias tool.

Results:

Included were 43 articles (31 in vivo and 12 in vitro studies) investigating the anterior cruciate ligament/cranial cruciate ligament (n = 32), medial collateral ligament (n = 6), suspensory ligament (n = 3), patellar ligament (n = 1), and Hock ligament (n = 1). Platelet concentration was reported in 34 studies (77.3%); leukocyte composition, in 12 (27.3%); and red blood cell counts, in 7 (15.9%). With PRP treatment, 5 of 12 in vitro studies demonstrated significant increases in cell viability, 6 of 12 in gene expression, 14 of 32 in vivo studies reported superior ligament repair via histological evaluation, and 13 in vivo studies reported superior mechanical properties. Variability in PRP preparation methods was observed across all articles, and only 1 study reported all necessary information to be classified by the 4 schemes we used to evaluate reporting. Among the in vivo studies, detection and performance bias were consistently high, whereas selection, attrition, reporting, and other biases were consistently low.

Conclusion:

Conflicting data on the cellular and molecular effects of PRP for ligament injuries were observed secondary to the finding that included studies were heterogeneous, limiting interpretation across studies and the ability to draw meaningful conclusions. Clinical trials and any causal relationship between PRP use in ligament injuries and its potential for regeneration and healing should be pursued with caution if based solely on basic science data.

A Simple Double-Spin Closed Method for Preparing Platelet-Rich Plasma

Objective: To describe and analyze a new protocol for the extraction of platelet-rich plasma (PRP) for use in clinical practice and compare this technique with methods that have been previously described in the medical literature.

Methods: Sixteen blood samples from healthy volunteers were collected. PRP was prepared using our new double-spin technique, consisting of successive centrifugation of blood samples with two different spins, without opening the container. Descriptive analysis of cell counts in baseline and PRP samples was undertaken. Comparison between cell and platelet count in baseline and PRP samples, as well as the statistical analysis, were done.

Results: The mean platelet concentration ratio was 3.47 (SD: 0.85; 95% CI: 3.01-3.92; range: 2.48-5.71). The baseline whole blood platelet count correlated positively to the PRP platelet count (rP = 0.56; 95% CI: 0.09-0.88; P = 0.023). The PRP was enriched for lymphocytes and monocytes but presented significantly lower counts of neutrophils and eosinophils in comparison to baseline.

Conclusion: Results show a safe and easily reproducible method to obtain PRP for use in clinical daily practice.

Effectiveness of Hematoma Aspiration and Platelet-rich Plasma Muscle Injections for the Treatment of Hamstring Strains in Athletes

INTRODUCTION

The effect of platelet-rich plasma (PRP) treatment on recovery in acute hamstring injuries is controversial. Previous study results are inconsistent, and a standardized therapeutic approach has not been established yet.

PURPOSE

To assess the treatment effect using a combination of hematoma aspiration and muscle strain PRP injection in partial hamstring muscle tears (grade 2 strains) in athletes.

METHODS

Magnetic resonance imaging of athletes with grade 2 hamstring strains were reviewed from 2013 to 2018. From 2013 to 2015, athletes were treated conservatively, and from 2016 to 2018, with a combination of ultrasound-guided hematoma aspiration and PRP muscle strain injection. The outcome, including return-to-play (in days) and recurrence rate, was compared retrospectively between both groups (conservative vs aspiration/PRP) using ANOVA and Fisher's exact test. There was no significant difference in age, type of sport, and muscle involvement (including injury grade/location, hamstring muscle type, and length/cross-sectional area of the strain).

RESULTS

Fifty-five athletes (28 treated conservatively, 27 with hematoma aspiration/PRP injection) were included. Average return-to-play time (mean) was 32.4 d in the conservative group and 23.5 d in the aspiration/PRP group (P < 0.001). Recurrence rate of the hamstring strain was 28.6% (8/28) in the conservative treatment group and less than 4% (1/27) in the aspiration/PRP group (P = 0.025).

CONCLUSIONS

Athletes with grade 2 hamstring strains treated with a combination of hematoma aspiration and PRP injection had a significantly shorter return-to-play and a lower recurrence rate compared with athletes receiving conservative treatment.

Device-Based Enrichment of Knee Joint Synovial Cells to Drive MSC Chondrogenesis Without Prior Culture Expansion In Vitro: A Step Closer to 1-Stage Orthopaedic Procedures

BACKGROUND

Synovial fluid (SF) mesenchymal stem cells (MSCs) are derived from the synovial membrane and have cartilage repair potential. Their current use in clinical practice is largely exploratory. As their numbers tend to be small, therapeutic procedures using MSCs typically require culture expansion. Previous reports indicate that the stem cell-mobilizing device (STEM device) intraoperatively increases SF-MSCs.

PURPOSE

This study evaluated the chondrogenic potential of non-culture expanded synovium-mobilized MSCs and SF-microfragments obtained after enrichment using the STEM device and ascertained if device-mediated synovial membrane manipulation facilitated ongoing MSC release.

STUDY DESIGN

Controlled laboratory study.

METHODS

Two samples of aspiration fluid were collected intraoperatively before and after STEM device utilization from patients (n = 16) undergoing diagnostic or therapeutic knee arthroscopy. Human knee synovium (n = 5) was collected during total knee replacement, and a suspended culture was performed to assess the effect of the STEM device on ongoing MSC release. Colony forming unit-fibroblastic assays were used to determine the number of MSCs. Additionally, cytometric characterization of stromal and immune cells and chondrogenesis differentiation assay were performed without culture expansion. Filtered platelet concentrates were prepared using the HemaTrate system.

RESULTS

After STEM device use, a significant increase was evident in SF-MSCs (P = .03) and synovial fluid-resident synovial tissue microfragments (P = .03). In vitro-suspended synovium released significantly more MSCs following STEM device use than nonstimulated synovium (P = .01). The STEM device-released total cellular fraction produced greater in vitro chondrogenesis with significantly more glycosaminoglycans (GAGs; P < .0001) when compared with non-STEM device synovial fluid material. Nonexpanded SF-MSCs and SF-microfragments combined with autologous filtered platelet concentrate produced significantly more GAGs than the complete chondrogenic media (P < .0001). The STEM device-mobilized cells contained more M2 macrophage cells and fewer M1 cells.

CONCLUSION

Non-culture expanded SF-MSCs and SF-microfragments had the potential to undergo chondrogenesis without culture expansion, which can be augmented using the STEM device with increased MSC release from manipulated synovium for several days. Although preliminary, these findings offer proof of concept toward manipulation of the knee joint environment to facilitate endogenous repair responses.

CLINICAL RELEVANCE

Although numbers were small, this study highlights 3 factors relevant to 1-stage joint repair using the STEM device: increased SF-MSCs and SF-microfragments and prolonged synovial release of MSCs. Joint repair strategies involving endogenous MSCs for cartilage repair without the need for culture expansion in a 1-stage procedure may be possible.

Orthobiologics: Diagnosis and Treatment of Common Tendinopathies

Orthobiologics, including platelet-rich plasma, prolotherapy, and mesenchymal stem cells, are seeing increasing use in the treatment of osteoarthritis (OA), muscle injury, and tendinopathy. This article reviews the biology and applications of orthobiologics in tendons, muscles, and joints, and focuses on platelet-rich plasma (PRP). Clinical evidence-based literature related to the use of PRP in the treatment of rotator cuff injury, lateral epicondylosis, Achilles tendinopathy, plantar fasciitis, knee OA, and acute muscle injury are discussed.

Systematic Review of Platelet-Rich Plasma for Rotator Cuff Repair: Are We Adhering to the Minimum Information for Studies Evaluating Biologics in Orthopaedics?

Background

The therapeutic efficacy of orthobiologic therapies for rotator cuff repair is difficult to evaluate owing to reporting inconsistences. In response, the Minimum Information for Studies Evaluating Biologics in Orthopaedics (MIBO) guidelines were developed to ensure standard reporting on orthobiologic therapies.

Purpose

To systematically review clinical studies evaluating platelet-rich plasma (PRP) for full-thickness rotator cuff repair and adherence to MIBO guidelines.

Study Design

Scoping review; Level of evidence, 4.

Methods

A search was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using PubMed, EMBASE, and the Cochrane Library databases. Inclusion criteria were clinical studies reporting on rotator cuff tears (≥1 cm) surgically repaired with PRP. Patient demographics, biologic intervention, and adherence to the MIBO guidelines were systematically reviewed.

Results

A total of 19 studies (1005 patients) were included in this review. Across all studies, 58.5% of the MIBO checklist items for PRP were reported. Out of 47 checklist items, 19 were reported in over 85% of studies, whereas 22 were reported in less than half of studies. Details of whole-blood processing and characteristics, as well as PRP processing and characteristics, were reported inconsistently, and no study provided adequate information to enable the precise replication of preparation protocols for PRP.

Conclusion

This systematic review highlights the current reporting deficiencies within the scientific literature of important variables for evaluating PRP for full-thickness rotator cuff repair. There was widespread variability among published studies that evaluate PRP for this application and, more specifically, studies were limited by inconsistent universal reporting of whole-blood and PRP processing and postprocessing characteristics. To improve our understanding of biologic efficacy and to promote repeatability, stricter adherence to the MIBO guidelines is necessary. We propose that the checklist limitations be addressed and that modification of the MIBO guidelines be considered to improve the reporting of individual components within certain categories.

Platelet-rich plasma in hair loss-Mechanism, preparation, and classification

Platelet-rich plasma is the autologous plasma containing platelet concentration more than the baseline separated after centrifugation. It has become a very popular option for the treatment of hair loss in the past few decades. Used alone or in combination with other treatment options it has found a place as a hair restoration procedure throughout the world. However, evidence supporting its credibility is quite ambiguous with contradictory reports available in the literature. In this article, we try to analyze the available data regarding its mechanism of action, preparation protocols, and classification, with regard to hair loss.

Autologes plättchenreiches Plasma in der Behandlung der Alopezie

Autologes plättchenreiches Plasma wird aufgrund seiner wundheilenden Eigenschaften vielfach angewandt u. a. in Orthopädie, Chirurgie und Dermatologie. Zunehmend stellt plättchenreiches Plasma außerdem bei bestimmten Formen der Alopezie eine interessante neue Behandlungsoption dar, sei es als alleinige Therapie oder auch als Adjuvans im Rahmen einer Haartransplantation. Kontrollierte klinische Studien an kleineren Patientengruppen zeigten vielfach positive Ergebnisse, größere Studien stehen bislang noch aus. Die Wirkung auf das Haarwachstum wird sehr wahrscheinlich über die in plättchenreichem Plasma enthaltenen Wachstumsfaktoren und Zytokine vermittelt.

Intramammary treatment using allogeneic pure platelet-rich plasma in cows with subclinical mastitis caused by Gram-positive bacteria

The aims of the study were (1) to compare the cure risk of intramammary treatment of pure platelet rich plasma (P-PRP) or cefquinome sulfate (CS) in cows with subclinical mastitis (SCM) caused by Gram-positive bacteria, evaluated via somatic cell count (SCC) and the microbiological analysis of milk; (2) to compare the inflammatory/anti-inflammatory response of mammary gland to both treatments through the analyses of interleukins (IL), interferon gamma (IFN-γ), and tumour necrosis factor alpha (TNF-α) in milk. A non-inferiority randomized clinical trial was conducted. The null hypothesis was that cure risk in the experimental group (P-PRP) was inferior to the reference group (CS). A total of 103 cows were selected according to SCC and presence of Gram-positive bacteria, 49 cows were treated with CS and 54 cows were treated with P-PRP after determination of its cellular and molecular quality control. Cure was assessed by milk analyses at day 21 and 22 after treatment. Cows that remained with SCM were retreated at day 26, and cure assessed at day 47 and 48. Overall, bacteriological cure was observed in 16 cows (30%) of the P-PRP group, and 35 cows (71%) in CS group. Staphylococcus aureus cure risk was higher in CS group, but inconclusive for Streptococcus spp. The mean SCC increased in relation to time only in the P-PRP group. A direct relation between time and treatment for IL-1, IL-2, and IL-6 was observed, while no differences were observed for IL-4. Furthermore, IL-1 and IL-2 increased in cows treated twice in both groups. IL-8, IFN-γ, and TNF-α showed a significant interaction between time and treatment. IFN-γ concentration was lower in the P-PRP group compared to the CS on days 0 and 22. Leukocyte counts were lower in P-PRP when compared to whole blood. TGF-β1 and PF4 concentrations were higher in platelet lysates in comparison to P-PRGS and plasma. Moreover, PDGF-BB concentration was significantly higher in platelet lysates in comparison to plasma. Results obtained in this study demonstrate that SCM treated with PRP showed a lower rate of bacteriologic cure when compared to animals treated with CS.

Single versus multi-dose intra-articular injection of platelet rich plasma in early stages of osteoarthritis of the knee: A single-blind, randomized, superiority trial

Objectives

This study aims to compare the effectiveness of single, double, and triple doses of intra-articular (IA) platelet rich plasma (PRP) in early stages of osteoarthritis (OA) of the knee.

Patients and methods

This single-blind, randomized, superiority trial included a total of 180 knees of 90 patients (22 males, 68 females; mean age: 47.9 years; range, 36 to 60 years) with bilateral OA knee of Kellgren-Lawrence Grade 1-2 between May 2017 and December 2018. The patients were randomized (30 in each group) to receive single, double, or triple doses of IA PRP (two weeks apart in repeat injections). The outcome measures were Visual Analog Scale, International Knee Documentation Committee Score, Knee Injury and Osteoarthritis Outcome Score, and Tegner Lysholm Knee Score. The assessor of outcome was blinded. The scores were collected before intervention and at six weeks, three months, six months, and one year after the intervention.

Results

All patients completed the study. All three groups were comparable with respect to demographic and disease characteristics. All four scores were comparable among the three groups before intervention and at six weeks, three months, and six months. However, at one-year follow-up, the three-dose group showed superiority to others in terms of all four scores. All three groups showed improvement until six months and deterioration thereafter, which was only marginal in the three-dose group. All groups showed a statistically significant improvement of scores compared to baseline scores at one year. There were no major complications.

Conclusion

The IA administration of three doses of PRP yields superior outcome to single and double doses at the end of one year. Repeat doses are probably needed to sustain the benefit achieved at one year.

Platelet-Rich Plasma Facial Rejuvenation: Myth or Reality?

Platelet-rich plasma (PRP) rejuvenation's efficacy has been reported by numerous uncontrolled clinical case studies of inconsistent quality rather than large randomized and placebo-controlled trials. It was suggested that PRP could be considered as a valid anti-aging and rejuvenation treatment modality. The current literature review summarizes available evidence so far described in the literature with special critical attention to higher quality comparative studies published over the last 10 years. The few studies that could be retrieved and included in this review documented less favorable results. So far, there is no international consensus on clinical PRP use for esthetic rejuvenation. Whether a mix of growth factors does in fact generate a clinically significant more youthful look and whether PRP injections result in comparable or better rejuvenation than what can be expected from other simpler non-surgical modalities. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Platelet-Rich Plasma in Facial Rejuvenation: A Systematic Appraisal of the Available Clinical Evidence

Purpose

Platelet-rich plasma (PRP) is a promising noninvasive technique for facial rejuvenation. This systematic literature review aims to appraise the nature and quality of published evidence evaluating the effectiveness and safety of PRP in facial rejuvenation.

Patients and Methods

A systematic literature review was conducted with the search string “Platelet-rich plasma AND Facial rejuvenation” in PubMed and Embase. Clinical studies evaluating the outcomes after PRP-based facial rejuvenation either as monotherapy or in combination with other treatment modalities were included. Studies evaluating wound-healing properties of PRP were excluded. The outcomes included both patient-reported and physician-assessed outcomes. Nonstatistical synthesis of evidence was performed by qualitative assessment. The results are reported by the Synthesis Without Meta-analysis (SWiM) reporting standard.

Results

A total of 36 studies that included a total of 3172 patients were considered for the evidence synthesis. The number of patients in the included studies ranging from 11 to 2005 with a median of 27.5 patients that reflects the challenges in clinically assessing the aesthetic outcomes after PRP-based facial rejuvenation. Among the 36 studies, 17 were observational studies and 18 were interventional studies with 1 being case report PRP was evaluated either alone or in combination with hyaluronic acid, lipofilling, micro-needling technique, and laser-based interventions. Among the studies, 1 study reported the enhanced platelet concentrate in a fibrin matrix to be relatively safe and effective with a maximum benefit observed at 12 weeks suggesting the platelet-rich fibrin matrix may provide desired aesthetic outcomes and it requires further studies to substantiate.

Conclusion

The results suggest very limited clinical evidence, and further clinical studies are warranted to establish the effectiveness of PRP in facial rejuvenation. Furthermore, a consensus for end points used for establishing clinical utility in patients requiring facial rejuvenation is warranted.

Even experts cannot agree on the optimal use of platelet-rich plasma in lateral elbow tendinopathy: an international Delphi study

Background

Platelet-rich plasma (PRP) is widely used in the management of lateral elbow tendinopathy (LET) despite conflicting evidence on its effectiveness. With high levels of user experience, this study aimed to assess consensus amongst experts on its clinical use.

Methods

A three-round international Delphi study was conducted. Participants were invited through national society mailing lists and contact lists derived from a systematic search of the literature on PRP. In round one, a primary working group developed 40 statements on PRP preparation and clinical application. In rounds two and three, an international group of researchers on PRP and clinical users of the device scored their levels of agreement with the statements on a five-point scale. Consensus was defined as an interquartile range of ≤ 1.

Results

Consensus of agreement was only reached for 17/40 (42.5%) statements. For statements on PRP formulation, consensus of agreement was reached in 2/6 statements (33%). Only limited consensus on the contraindications, delivery strategy and delivery technique was achieved.

Conclusion

Experts reached very limited consensus on the use of PRP in LET. High levels of user experience have not resulted in a convergence of opinion on the technical components of PRP formulation and delivery, substantiating the need for further studies and improved trial reporting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10195-021-00608-5.

Proteomic Characterization of Plasma Rich in Growth Factors and Undiluted Autologous Serum

Over the last three decades, there has been special interest in developing drugs that mimic the characteristics of natural tears for use it in the treatment of several ocular surface disorders. Interestingly, the composition of blood plasma is very similar to tears. Therefore, different blood-derived products like autologous serum (AS) and plasma rich in growth factors (PRGF) have been developed for the treatment of diverse ocular pathologies. However, scarce studies have been carried out to analyze the differences between both types of blood-derived products. In the present study, blood from three healthy donors was drawn and processed to obtain AS and PRGF eye drops. Then, human corneal stromal keratocytes (HK) were treated with PRGF or undiluted AS. Proteomic analysis was carried out to analyze and characterize the differential protein profiles between PRGF and AS, and the differentially expressed proteins in HK cells after PRGF and AS treatment. The results obtained in the present study show that undiluted AS induces the activation of different pathways related to an inflammatory, angiogenic, oxidative stress and scarring response in HK cells regarding PRGF. These results suggest that PRGF could be a better alternative than AS for the treatment of ocular surface disorders.

Clinical Cohort Study in Canine Patients, to Determine the Average Platelet and White Blood Cell Number and Its Correlation with Patient's Age, Weight, Breed and Gender: 92 Cases (2019-2020)

Due to its easy preparation and that it is well tolerated, the use of autologous platelet-rich plasma (PRP) has become increasingly popular in regenerative medicine. However, there are still no clear guidelines on how it should be classified or whether the individual canine patient’s clinical status can influence its quality. Objective: This study aims to show if the weight, age, sex, neutered status or breed of canine patients have any correlation with the composition of PRP. Design: A blinded count of the platelets and white blood cells (WBC) was performed from 111 samples from 92 client owned dogs undergoing treatment for degenerative joint disease (DJD). The results were analysed using Pearson correlation test, ANOVA test or Student T-test. Results: There is a positive correlation between the number of platelets and WBC in canine patients of different breeds, but there was no significant difference on the platelet number and WBC number among the different breeds. The weight of the patient is also directly correlated to the platelet number (p = 0.003) but not WBC number. WBC number was negatively correlated to the weight of the patient. The sex and age of the patient did not affect platelets and WBC number, although WBC number is increased in non-neutered male population (p = 0.003). However, it would be interesting to investigate whether the growth factors released from the platelet granules are affected by patient variables in a canine population. Conclusions: Our results show that it is possible to obtain good quality autologous PRP, irrespective of age, sex, neutered status or weight of the patient, for PRP regenerative therapy.

Regenerative effect of platelet-rich plasma in the murine ischemic limbs

AIMS

The purpose of this study was to investigate the effect of PPRP (pure PRP) and LPRP (PRP with leukocytes) on recovery from limb ischemia and on expression of growth factors involved in angiogenesis, myogenesis and fibrogenesis.

MATERIAL AND METHODS

PPRP and LPRP prepared by centrifugation were added to cultures of C2C12 and NIH3T3 cells (1 or 10% PRPs) to evaluate alterations in cell metabolism and expression of growth factors by MTT, ELISA and RT-qPCR, respectively. To evaluate in vivo regenerative effects, PRPs were injected into the ischemic limbs of BALB/c mice and muscle mass/strength and histomorphometry were evaluated after 30 days.

KEY FINDINGS

Mice treated with PRPs after limb ischemia showed an increase in the size of myofibers and muscle strength, reduced fibrosis and adipocytes, and decreased capillary density and necrosis scores compared to untreated mice. In cell culture, serum deprivation reduced the viability of C2C12 and NIH3T3 cells to about 50%, but the addition of 1% PRPs completely recovered this loss. Both PRPs, downregulated most of the tested genes; however, angiogenic gene Vegfa in C2C12 and the fibrogenic genes Col1a1 and Col3a1 in NIH3T3 cells were upregulated by LPRP.

SIGNIFICANCE

PPRP and LPRP had similar effects in regulation of genes involved in angiogenesis, myogenesis and fibrogenesis. However, the presence of leucocytes did not significantly affect regenerative activities of PRP in the ischemic limb.

A Retrospective Analysis of Clinical Outcome and Predictive Factors for Responders with Knee Osteoarthritis to a Single Injection of Leukocyte-Poor Platelet-Rich Plasma

Although various platelet-rich plasma (PRP) kits are commercially available, the efficacy of these kits for knee osteoarthritis (KOA) has not been fully investigated. This study aimed to investigate the short-term results of leukocyte-poor PRP (LP-PRP) and the factors that contribute to its efficacy. We retrospectively reviewed 124 patients with KOA who were treated with LP-PRP. White blood cell (WBC) and platelet counts in the whole blood and the LP-PRP were measured. KOA severity was assessed using radiography. Clinical evaluation was performed both prior to injection and after an average of 3.3 weeks after the injection using the Japanese Knee Osteoarthritis Measure (JKOM). Responders were defined based on the JKOM. The contributing factors for responders were examined using a multivariate logistic analysis. The responder rate was 58.1% and the contributing factors for responders were a higher visual analog scale score before injection, WBC count in whole blood, and platelet concentration ratio of LP-PRP. The LP-PRP improved the clinical scores in the short term. Certain patient characteristics before injection and the concentration ratio of LP-PRP may be predictors of its efficacy; these may provide clues for elucidating which components of LP-PRP act on KOA pathologies.

Evaluation of the Effects of Platelet-Rich Plasma on Follicular and Endometrial Growth: A Literature Review

Platelet-rich plasma (PRP) has been used in several areas of medicine due to its ability to promote tissue regeneration by growth factors and cytokines. This review addresses the use of PRP to rejuvenate ovarian follicles and increase the thickness of the endometrium to receive an embryo. PRP is obtained from the patient's own blood (autologous blood) - a fact that determines a lower chance of rejection reactions. Alpha granules of platelets provide and release supra physiological amounts of growth factors and cytokines, which provide a regenerative stimulus in tissues with low healing potential. In the ovary, PRP and its growth factors stimulate vascularization and recruitment of available primordial follicles that could no longer be otherwise stimulated. The rejuvenation of the ovary by PRP infusion aims to obtain new oocytes in ovaries with low numbers of follicles or low follicular reserve markers. In the preparation of the endometrium, PRP is used for its several growth factors that allow tissue proliferation and endometrial thickening, especially in cases of endometria that are difficult to prepare or that fail to reach an adequate minimum thickness (>7mm). To date, there are few studies of greater expression in the literature that support the use of PRP with the two purposes described above. Thus, although promising, the technique must still be validated by larger clinical trials.

Autologous blood and platelet-rich plasma injection therapy for lateral elbow pain

BACKGROUND

Autologous whole blood or platelet-rich plasma (PRP) injections are commonly used to treat lateral elbow pain (also known as tennis elbow or lateral epicondylitis or epicondylalgia). Based on animal models and observational studies, these injections may modulate tendon injury healing, but randomised controlled trials have reported inconsistent results regarding benefit for people with lateral elbow pain.

OBJECTIVES

To review current evidence on the benefit and safety of autologous whole blood or platelet-rich plasma (PRP) injection for treatment of people with lateral elbow pain.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase for published trials, and Clinicaltrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal for ongoing trials, on 18 September 2020.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) and quasi-RCTs comparing autologous whole blood or PRP injection therapy to another therapy (placebo or active treatment, including non-pharmacological therapies, and comparison between PRP and autologous blood) for lateral elbow pain. The primary comparison was PRP versus placebo. Major outcomes were pain relief (≥ 30% or ≥ 50%), mean pain, mean function, treatment success, quality of life, withdrawal due to adverse events, and adverse events; the primary time point was three months.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 32 studies with 2337 participants; 56% of participants were female, mean age varied between 36 and 53 years, and mean duration of symptoms ranged from 1 to 22 months. Seven trials had three intervention arms. Ten trials compared autologous blood or PRP injection to placebo injection (primary comparison). Fifteen trials compared autologous blood or PRP injection to glucocorticoid injection. Four studies compared autologous blood to PRP. Two trials compared autologous blood or PRP injection plus tennis elbow strap and exercise versus tennis elbow strap and exercise alone. Two trials compared PRP injection to surgery, and one trial compared PRP injection and dry needling to dry needling alone. Other comparisons include autologous blood versus extracorporeal shock wave therapy; PRP versus arthroscopic surgery; PRP versus laser; and autologous blood versus polidocanol. Most studies were at risk of selection, performance, and detection biases, mainly due to inadequate allocation concealment and lack of participant blinding. We found moderate-certainty evidence (downgraded for bias) to show that autologous blood or PRP injection probably does not provide clinically significant improvement in pain or function compared with placebo injection at three months. Further, low-certainty evidence (downgraded for bias and imprecision) suggests that PRP may not increase risk for adverse events. We are uncertain whether autologous blood or PRP injection improves treatment success (downgraded for bias, imprecision, and indirectness) or withdrawals due to adverse events (downgraded for bias and twice for imprecision). No studies measured health-related quality of life, and no studies reported pain relief (> 30% or 50%) at three months. At three months, mean pain was 3.7 points (0 to 10; 0 is best) with placebo and 0.16 points better (95% confidence interval (CI) 0.60 better to 0.29 worse; 8 studies, 523 participants) with autologous blood or PRP injection, for absolute improvement of 1.6% better (6% better to 3% worse). At three months, mean function was 27.5 points (0 to 100; 0 is best) with placebo and 1.86 points better (95% CI 4.9 better to 1.25 worse; 8 studies, 502 participants) with autologous blood or PRP injection, for absolute benefit of 1.9% (5% better to 1% worse), and treatment success was 121 out of 185 (65%) with placebo versus 125 out of 187 (67%) with autologous blood or PRP injection (risk ratio (RR) 1.00; 95% CI 0.83 to 1.19; 4 studies, 372 participants), for absolute improvement of 0% (11.1% lower to 12.4% higher). Regarding harm, we found very low-certainty evidence to suggest that we are uncertain whether withdrawal rates due to adverse events differed. Low-certainty evidence suggests that autologous blood or PRP injection may not increase adverse events compared with placebo injection. Withdrawal due to adverse events occurred in 3 out of 39 (8%) participants treated with placebo versus 1 out of 41 (2%) treated with autologous blood or PRP injection (RR 0.32, 95% CI 0.03 to 2.92; 1 study), for an absolute difference of 5.2% fewer (7.5% fewer to 14.8% more). Adverse event rates were 35 out of 208 (17%) with placebo versus 41 out of 217 (19%) with autologous blood or PRP injection (RR 1.14, 95% CI 0.76 to 1.72; 5 studies; 425 participants), for an absolute difference of 2.4% more (4% fewer to 12% more). At six and twelve months, no clinically important benefit for mean pain or function was observed with autologous blood or PRP injection compared with placebo injection.

AUTHORS' CONCLUSIONS

Data in this review do not support the use of autologous blood or PRP injection for treatment of lateral elbow pain. These injections probably provide little or no clinically important benefit for pain or function (moderate-certainty evidence), and it is uncertain (very low-certainty evidence) whether they improve treatment success and pain relief > 50%, or increase withdrawal due to adverse events. Although risk for harm may not be increased compared with placebo injection (low-certainty evidence), injection therapies cause pain and carry a small risk of infection. With no evidence of benefit, the costs and risks are not justified.

Predictors of Effectiveness of Platelet-Rich Plasma Therapy for Knee Osteoarthritis: A Retrospective Cohort Study

There has recently been growing interest worldwide in biological therapies such as platelet-rich plasma injection for the treatment of knee osteoarthritis. However, predicting the effectiveness of platelet-rich plasma therapy remains uncertain. Therefore, this retrospective cohort study was performed to assess a range of predictors for the effectiveness of platelet-rich plasma therapy in treating knee osteoarthritis. The study included 517 consecutive patients who underwent three injections of leucocyte-poor platelet-rich plasma therapy from 2016 to 2019 at a single institution. The treatment outcomes, including patient-oriented outcomes (visual analogue scale score and Knee Injury and Osteoarthritis Outcome Score), were analyzed and compared according to the severity of knee osteoarthritis based on Kellgren–Lawrence (KL) grading using standing plain radiographs. Fisher’s exact test, univariate regression, and multivariate regression were used for data analysis. Patient-oriented outcomes were significantly improved 6 and 12 months after platelet-rich plasma therapy. The overall responder rate in patients who met the Outcome Measures in Rheumatology (OMERACT)–Osteoarthritis Research Society International (OARSI) responder criteria was 62.1%. The responder rate was significantly lower in patients with severe knee osteoarthritis (KL4, 50.9%) than in those with mild (KL2, 75.2%) and moderate (KL3, 66.5%) knee osteoarthritis. The multivariate logistic regression analysis revealed that deterioration of the knee osteoarthritis grade (increased KL grade) was a significant predictor of a worse clinical outcome (odds ratio, 0.58; 95% confidence interval, 0.45–0.75; p < 0.001). The relative risk for non-responders in severe (KL4) KOA was 2.1 (95% CI, 1.5–3.0) at 6 months and 2.3 (1.6–3.2) at 12 months compared with mild-to-moderate (KL2-3) KOA. The efficacy of platelet-rich plasma therapy was not affected by age, sex, body weight, or platelet count. This study revealed that the effectiveness of platelet-rich plasma therapy for the treatment of knee osteoarthritis is approximately 60% and that the effectiveness depends on the severity of knee osteoarthritis. This observation is useful not only for physicians but also for patients with knee osteoarthritis.

Case Report: Rehabilitation After Platelet-Rich Growth Factors' Intra-Articular Injections for Knee Osteoarthritis: Two Case Reports of a Home-Based Protocol

Knee osteoarthritis (KOA) is a chronic progressive disease that can cause pain, functional impairment, and ultimately disability. A novel and promising therapeutic approach to KOA is the so-called regenerative medicine, a set of procedures designed to harness tissue regenerative capacity and optimize functional recovery. Increasing evidence points out that platelet-rich plasma (PRP) intra-articular injections can decrease pain and improve functional abilities in KOA patients. In the present case reports, we analyze two patients who were treated with PRP injections coupled with a posttreatment home-based rehabilitation program. The two patients were selected to represent two different populations: patient 1 was an 85-year-old with severe impairment of functional abilities, while patient 2 was a younger (59 years old) and more active patient. The protocol consisted in a series of exercise to be performed at home, during the five days following PRP injection for two consecutive weeks (10 days in total). The exercises were designed to reduce the inflammation after the injection, enhance the proprioceptive control of the treated lower limb, and strengthen hip and knee flexors and extensors, mainly by isometric work. Results were evaluated at two time points: before and 2 months after the first PRP injection. The outcomes considered were as follows: visual analog scale for pain, EuroQol 5 dimensions questionnaire, Tegner Activity Scale for functioning, and Knee Injury and Osteoarthritis Outcome Score (KOOS). Both patients did not report any side effects from the treatment. Improvement in patient 1 was drastic at the two months follow-up as far as pain and functional abilities are concerned. Patient 2’s improvement was less evident, probably due to the higher starting point in both pain and functionality. Overall, the developed program seemed safe and was tolerated by the patients analyzed in the study, who performed it with good compliance.

A Modified Preparation Method of Ideal Platelet-Rich Fibrin Matrix From Whole Blood

One bioproduct that is widely used in the wound healing process is platelet-rich plasma (PRP). PRP is a liquid solution with high autologous platelet concentration, making it a good source of growth factors to accelerate wound healing. Recent development in PRP had created a new product called platelet-rich fibrin matrix (PRFM), which has a denser and more flexible structure. PRFM is the newest generation of platelet concentrate with a fibrin matrix that holds platelet in it. The key concept in creating PRFM from PRP is the addition of CaCl₂ followed by centrifugation, which converts fibrinogen to fibrin, and the fibrin cross-links to form a matrix that contains viable platelets. There are many commercially available kits to create PRFM, but they are often expensive and uneconomical. This research will test a modified method of making ideal PRFM from PRP without any commercial kits. The modified method will include determining the minimum level of CaCl₂ used, the type of centrifuge, and the speed and duration of centrifugation. By performing a modified preparation method on five samples of whole blood, it was found that the ideal PRFM could be made by mixing PRP with 25 mM CaCl₂ and centrifuging it at a speed of 2,264 × g for 25 min at room temperature. The PRP and PRFM platelet counts of this method tend to be lower than the platelet counts found in other studies. Although visually comparable, further study is needed to compare the performance of PRFMs made with this method and PRFMs made with commercial kits.

Editorial Commentary: Platelet-Rich Plasma Shows Promise for Improving Shoulder Tendinopathy

Platelet-rich plasma (PRP) injections continue to be used at increasing rates to treat common musculoskeletal conditions. PRP has a low-risk profile and emerging in vitro evidence to support its positive effects on soft-tissue healing. PRP has been shown to be of benefit for knee osteoarthritis, but less has been published regarding the shoulder. PRP delivers a high concentration of growth factors, cytokines, and other important inflammatory modulators. Its use is appealing for treating partial-thickness rotator cuff tears, subacromial bursitis, and rotator cuff tendinopathy since rotator cuff tendons often have poor healing capacity due to intrinsic degeneration. PRP has been shown to increase cell proliferation and matrix synthesis in tenocytes, which may aid tendon regeneration and healing. Adult tendons also contain a small amount of tendon progenitor cells, which can be induced to an active state by PRP. In addition, PRP is an autologous biologic agent and easy to acquire and administer in an outpatient clinical setting. Clinical studies continue to lag and are often heterogenous in quality and in results. PRP can vary widely based on multiple intrinsic and extrinsic factors, including patient age, sex, activity level, centrifugation speed, and number of centrifugation cycles. Thus, quality research methods should include reporting using the PAW (platelets/activation/white blood cells) system. Clinicians should remain cautiously optimistic about the future role of PRP injections in the shoulder.

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.

Subacromial Platelet-Rich Plasma Injections Decrease Pain and Improve Functional Outcomes in Patients With Refractory Rotator Cuff Tendinopathy

PURPOSE

The purpose of this study was to evaluate the effect of subacromial platelet-rich plasma (PRP) injections in patients with refractory rotator cuff tendinopathies based on pain improvement, functional outcomes, sleep disturbances, and return to sports to the same level as before the injury.

METHODS

Between March 2019 and October 2019, 50 patients with rotator cuff tendinopathy refractory to conservative treatment were treated with one subacromial PRP injection in our institution. Magnetic resonance imaging was performed in all patients to confirm diagnosis. The visual analog scale (VAS) was used to evaluate pain. Range of motion, the American Shoulder and Elbow Surgeons (ASES) score, and the Constant score were used to assess functional outcomes. Eighty percent of the patients (40 of 50 patients) and 86% of the patients (43 of 50 patients) achieved a clinically significant improvement that exceeded the substantial clinical benefit for the ASES and Constant scores, respectively. The Pittsburgh Sleep Quality Index was used to assess sleep disorders. Return to sports was also evaluated. The mean follow-up was 12 months, and the mean (SD) age was 37.3 (9.3) years.

RESULTS

All mobility parameters evaluated improved significantly after treatment. The VAS, ASES, and Constant scores showed statistical improvement after the injection (P < .001). Sleep disturbances were resolved in 86% of the patients. Of the 32 patients who practiced sports before the injury, 84% returned to sports and 78% returned to the same level. There were no complications associated with the procedure.

CONCLUSIONS

In most patients with refractory rotator cuff tendinopathy, subacromial injections of leukocyte-rich PRP significantly decreased pain, improved functional outcomes, and resolved sleep disturbances. Moreover, most of the athletes returned to sports at the same level they had before the injury.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Enrichment of plasma in platelets and extracellular vesicles by the counterflow to erythrocyte settling

In order to prepare optimal platelet and extracellular vesicle (EV)-rich plasma for the treatment of chronic temporal bone inflammation, we studied effects of centrifugation parameters on redistribution of blood constituents in blood samples of 23 patients and 20 volunteers with no record of disease. Concentrations of blood cells and EVs were measured by flow cytometry. Sample content was inspected by scanning electron microscopy. A mathematical model was constructed to interpret the experimental results. The observed enrichment of plasma in platelets and EVs after a single spin of blood depended on the erythrocyte sedimentation rate, thereby indicating the presence of a flow of plasma that carried platelets and EVs in the direction opposite to settling of erythrocytes. Prolonged handling time correlated with the decrease of concentration of platelets and larger EVs in platelet and EV-rich plasma (PVRP), R = -0.538, p = 0.003, indicating cell fragmentation during the processing of samples. In further centrifugation of the obtained plasma, platelet and EV enrichment depended on the average distance of the sample from the centrifuge rotor axis. Based on the agreement of the model predictions with observations, we propose the centrifugation protocol optimal for platelet and EV enrichment and recovery in an individual sample, adjusted to the dimensions of the centrifuge rotor, volume of blood and erythrocyte sedimentation rate.[Figure: see text].

The effect of platelet-rich plasma injection on chronic Achilles tendinopathy and acute Achilles tendon rupture

Several clinical trials exploring the effect of platelet-rich plasma (PRP) on Achilles tendon rupture (ATR) or Achilles tendinopathy (AT) have been published. However, current evidence is limited to small-sized trials. This study aims to evaluate whether PRP improves the outcomes of ATR or AT. PubMed, Web of Science, EMBASE, and Cochrane Library databases were searched to identify randomized controlled trials comparing PRP injection versus placebo for ATR or AT. Eleven studies with 574 patients were included. Quantitative synthesis suggested that compared with placebo, AT patients in PRP group had higher VISA-A score improvement at six-week follow-up (mean difference (MD) = 2.64; 95% CI) = 1.12 to 4.15). However, there was no significant difference between two groups for VISA-A score improvement at three-month follow-up (MD = 0.93; 95% CI = -2.75 to 4.62), or 6-month follow-up (MD = 5.46; 95% CI = -1.19 to 12.11). In ATR patients, quantitative synthesis suggested that no significant difference was seen between PRP and control group at 3-month, 6-month, and 1-year follow-up. In addition, no significant difference was detected between the two groups in improving tendon thickness and pain for AT patients, and no significant difference was seen in improving heel-rise work, maximum heel-rise height, dorsal and plantar flexion, rate of returning to sports activities, and complication for ATR patients. To conclude, no evidence indicates that PRP injection can improve the patient-reported/clinical/functional outcomes of AT or ATR. The increasing times of PRP injection could improve the outcomes, and further clinical randomized controlled trials are expected to be conducted to verify this hypothesis.

Nonoperative and Operative Soft-Tissue and Cartilage Regeneration and Orthopaedic Biologics of the Knee: An Orthoregeneration Network (ON) Foundation Review

Orthoregeneration is defined as a solution for orthopedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and optimally, provide an environment for tissue regeneration. Options include: drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electro-magnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the knee, including symptomatic osteoarthritis and chondral injuries, as well as injuries to tendon, meniscus, and ligament, including the anterior cruciate ligament. Promising and established treatment modalities include hyaluronic acid (HA) in liquid or scaffold form; platelet-rich plasma (PRP); bone marrow aspirate (BMA) comprising mesenchymal stromal cells (MSCs), hematopoietic stem cells, endothelial progenitor cells, and growth factors; connective tissue progenitor cells (CTPs) including adipose-derived mesenchymal stem cells (AD-MSCs) and tendon-derived stem cells (TDSCs); matrix cell-based therapy including autologous chondrocytes or allograft; vitamin D; and fibrin clot. Future investigations should standardize solution preparations, because inconsistent results reported may be due to heterogeneity of HA, PRP, BMAC, or MSC preparations and regimens, which may inhibit meaningful comparison between studies to determine the true efficacy and safety for each treatment.