Platelet-rich plasma: the PAW classification system

Treatment of osteochondral injuries with platelet gel

OBJECTIVES

Treatments for injured articular cartilage have not advanced to the point that efficient regeneration is possible. However, there has been an increase in the use of platelet-rich plasma for the treatment of several orthopedic disorders, including chondral injuries. Our hypothesis is that the treatment of chondral injuries with platelet gel results in higher-quality repair tissue after 180 days compared with chondral injuries not treated with gel.

METHODS

A controlled experimental laboratory study was performed on 30 male rabbits to evaluate osteochondral injury repair after treatment with or without platelet gel. Osteochondral injuries were surgically induced in both knees of each rabbit at the medial femoral condyle. The left knee injury was filled with the platelet gel, and the right knee was not treated. Microscopic analysis of both knee samples was performed after 180 days using a histological grading scale.

RESULTS

The only histological evaluation criterion that was not significantly different between treatments was metachromasia. The group that was treated with platelet gel exhibited superior results in all other criteria (cell morphology, surface regularity, chondral thickness and repair tissue integration) and in the total score.

CONCLUSION

The repair tissue was histologically superior after 180 days in the study group treated with platelet gel compared with the group of untreated injuries.

Autologous platelet concentrates for bisphosphonate-related osteonecrosis of the jaw treatment and prevention. A systematic review of the literature

PURPOSE

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is an adverse drug reaction consisting of progressive bone destruction in the maxillofacial region of patients under current or previous treatment with a bisphosphonate. Autologous platelet concentrates (APC) demonstrated to enhance bone and soft tissue healing in oral surgery procedures. The present systematic review aimed at evaluating if APC may improve treatment and prevention of BRONJ in patients under bisphosphonate therapy.

METHODS

MEDLINE, Scopus and Cochrane databases were searched using terms like bisphosphonates, osteonecrosis, BRONJ, platelet concentrate, PRP, PRF, PRGF. No language, publication date and study design limitation was set. A hand search of the bibliographies of identified articles was also performed. The primary outcome was recurrence/onset of BRONJ after oral surgery procedures.

RESULTS

Eighteen studies were included, reporting on 362 patients undergoing oral surgery in combination with APC. The adjunct of APC in BRONJ treatment significantly reduced osteonecrosis recurrence with respect to control. APC was associated with a lower BRONJ incidence after tooth extraction, though not significant. Heterogeneity was found regarding bisphosphonate type, clinical indication, treatment duration, triggering factors, study design, follow-up duration, type of APC, outcomes adopted to evaluate treatment success.

CONCLUSION

Though the results of this review must be cautiously interpreted, due to the low evidence level of the studies included, and the limited sample size, they are suggestive of possible benefits of APC when associated with surgical procedures for treatment or prevention of BRONJ. To confirm such indication, prospective comparative studies with a large sample size are urgently needed.

Platelet-rich plasma injections for the treatment of hamstring injuries: a randomized controlled trial

BACKGROUND

A hamstring injury is one of the most common types of injury affecting athletes. Despite this, the optimal management of hamstring muscle injuries is not yet defined. The effect of autologous platelet-rich plasma (PRP) therapy on the recovery of hamstring injuries is unclear.

PURPOSE

To investigate the effect of a single PRP injection in the treatment of grade 2 hamstring muscle injuries.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

Twenty-eight patients diagnosed with an acute hamstring injury were randomly allocated to autologous PRP therapy combined with a rehabilitation program or a rehabilitation program only. The primary outcome of this study was time to return to play. In addition, changes in pain severity and pain interference scores over time were examined.

RESULTS

Patients in the PRP group achieved full recovery significantly earlier than controls (P = .02). The mean time to return to play was 26.7 ± 7.0 days and 42.5 ± 20.6 days for the PRP and control groups, respectively (t(22) = 2.50, P = .02). [corrected]. Significantly lower pain severity scores were observed in the PRP group throughout the study. However, no significant difference in the pain interference score was found between the 2 groups.

CONCLUSION

A single autologous PRP injection combined with a rehabilitation program was significantly more effective in treating hamstring injuries than a rehabilitation program alone.

Does intra articular platelet rich plasma injection improve function, pain and quality of life in patients with osteoarthritis of the knee? A randomized clinical trial

We designed a randomized clinical trial with control group, to investigate the effects of platelet rich plasma (PRP) on pain, stiffness, function and quality of life in patients with knee osteoarthritis. Patients were randomly divided in two groups. For both groups of participants, therapeutic exercise was prescribed. In the PRP group, two courses of leukocyte rich PRP (5.6 fold higher platelet concentration) with a 4-week interval was injected. For each participant, Western Ontario and McMaster University’s Arthritis Index (WOMAC) and the SF-36 questionnaire (Farsi version) were filled at the baseline and 6 months after treatments. Thirty-one patients in the PRP group and 31 patients in the control group were studied. Mean changes of total WOMAC, physical component summery and mental component summery of Short Form-36 in PRP group showed better improvement than control group (P<0.05). This study showed that intra articular PRP knee injection combined with therapeutic exercise can be more effective in pain reduction and improvement of stiffness and quality of life, compared with therapeutic exercise alone.

Efficacy and safety of plasma rich in growth factors intra-articular infiltrations in the treatment of knee osteoarthritis

PURPOSE

The goal of this study was to systematically review the efficacy and safety of plasma rich in growth factors (PRGF) as a treatment for reducing symptoms in patients with knee osteoarthritis.

METHODS

A comprehensive and systematic literature search was conducted for PRGF treatment of knee osteoarthritis following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. All the studies had to include a PRGF group and a control group. Pre- and post-treatment measures of joint pain, reduced function, and stiffness were evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index, Knee Injury and Osteoarthritis Outcome Score, International Knee Documentation Committee score, Lequesne index, or number of Outcome Measures for Rheumatology Committee and Osteoarthritis Research Society International Standing Committee for Clinical Trials Response Criteria Initiative (OMERACT-OARSI) responders, with a follow-up period of at least 4 weeks. An assessment of both the quality and risk of bias of the studies was conducted.

RESULTS

The literature search yielded 91 citations, but only 5 were eligible publications that met the inclusion criteria (2 randomized controlled trials, 2 prospective studies, and 1 retrospective analysis). Two studies were rated as having a low risk of bias whereas 3 had a high risk. In both randomized controlled trials, it was observed that after 6 months of treatment, the number of patients with a pain reduction of more than 50% was significantly higher in the PRGF group. In 2 other studies, the patients treated with PRGF showed a significant pain reduction compared with the control group. The remaining variables (Western Ontario and McMaster Universities Osteoarthritis Index scale for pain, function, and stiffness; Lequesne index; Knee Injury and Osteoarthritis Outcome Score scale; and number of OMERACT-OARSI responders) showed a statistically significant superiority of the group treated with PRGF.

CONCLUSIONS

The current clinical evidence suggests that PRGF intra-articular infiltrations in patients with knee osteoarthritis reduce pain and therefore are clinically efficacious in osteoarthritis treatment.

LEVEL OF EVIDENCE

Level III, systematic review of Level I, II, and III studies.

The basic science of platelet-rich plasma (PRP): what clinicians need to know

Platelet-rich plasma (PRP) has been advocated for the biological augmentation of tissue healing and regeneration through the local introduction of increased levels (above baseline) of platelets and their associated bioactive molecules. In theory, the increased levels of autologous growth factors and secretory proteins provided by the concentrated platelets may enhance the wound healing process, especially in degenerative tissues or biologically compromised individuals. Although PRP has been increasingly utilized in the treatment of a variety of sports-related injuries, improvements in healing and clinical outcomes have not been universally reported. One reason for this may be the fact that all PRP preparations are not the same. Variations in the volume of whole blood taken, the platelet recovery efficacy, the final volume of plasma in which the platelets are suspended, and the presence or absence of white blood cells, and the addition of exogenous thrombin to activate the platelets or calcium chloride to induce fibrin formation, can all affect the character and potential efficacy of the final PRP product. This article will review the basic principles involved in creating PRP and examine the potential basic scientific significance of the individual blood components contained in the various forms of PRP currently used in sports medicine.

Platelet-rich plasma and skeletal muscle healing: a molecular analysis of the early phases of the regeneration process in an experimental animal model

Platelet-rich plasma (PRP) has received increasing interest in applied medicine, being widely used in clinical practice with the aim of stimulating tissue healing. Despite the reported clinical success, there is still a lack of knowledge when considering the biological mechanisms at the base of the activity of PRP during the process of muscle healing. The aim of the present study was to verify whether the local delivery of PRP modulates specific molecular events involved in the early stages of the muscle regeneration process. The right flexor sublimis muscle of anesthetized Wistar rats was mechanically injured and either treated with PRP or received no treatment. At day 2 and 5 after surgery, the animals were sacrificed and the muscle samples evaluated at molecular levels. PRP treatment increased significantly the mRNA level of the pro-inflammatory cytokines IL-1β, and TGF-β1. This phenomenon induced an increased expression at mRNA and/or protein levels of several myogenic regulatory factors such as MyoD1, Myf5 and Pax7, as well as the muscular isoform of insulin-like growth factor1 (IGF-1Eb). No effect was detected with respect to VEGF-A expression. In addition, PRP application modulated the expression of miR-133a together with its known target serum response factor (SRF); increased the phosphorylation of αB-cristallin, with a significant improvement in several apoptotic parameters (NF-κB-p65 and caspase 3), indexes of augmented cell survival. The results of the present study indicates that the effect of PRP in skeletal muscle injury repair is due both to the modulation of the molecular mediators of the inflammatory and myogenic pathways, and to the control of secondary pathways such as those regulated by myomiRNAs and heat shock proteins, which contribute to proper and effective tissue regeneration.

Effectiveness of xenogenous-based bovine-derived platelet gel embedded within a three-dimensional collagen implant on the healing and regeneration of the Achilles tendon defect in rabbits

BACKGROUND AND OBJECTIVE

Tissue engineering is an option in reconstructing large tendon defects and managing their healing and regeneration. We designed and produced a novel xenogeneic-based bovine platelet, embedded it within a tissue-engineered collagen implant (CI) and applied it in an experimentally induced large tendon defect model in rabbits to test whether bovine platelets could stimulate tendon healing and regeneration in vivo.

METHODS

One hundred twenty rabbits were randomly divided into two experimental and pilot groups. In all the animals, the left Achilles tendon was surgically excised and the tendon edges were aligned by Kessler suture. Each group was then divided into three groups of control (no implant), treated with CI and treated with collagen-platelet implant. The pilot groups were euthanized at 10, 15, 30 and 40 days post-injury (DPI), and their gross and histologic characteristics were evaluated to study host-graft interaction mechanism. To study the tendon healing and its outcome, the experimental animals were tested during the experiment using hematologic, ultrasonographic and various methods of clinical examinations and then euthanized at 60 DPI and their tendons were evaluated by gross pathologic, histopathologic, scanning electron microscopic, biophysical and biochemical methods.

RESULTS

Bovine platelets embedded within a CI increased inflammation at short term while it increased the rate of implant absorption and matrix replacement compared with the controls and CI alone. Treatment also significantly increased diameter, density, amount, alignment and differentiation of the collagen fibrils and fibers and approximated the water uptake and delivery behavior of the healing tendons to normal contralaterals (p < 0.05). Treatment also improved echogenicity and homogenicity of the tendons and reduced peritendinous adhesion, muscle fibrosis and atrophy, and therefore, it improved the clinical scores and physical activity related to the injured limb when compared with the controls (p < 0.05).

CONCLUSION

The bovine platelet gel embedded within the tissue-engineered CI was effective in healing, modeling and remodeling of the Achilles tendon in rabbit. This strategy may be a valuable option in the clinical setting.

Classification of platelet concentrates (Platelet-Rich Plasma-PRP, Platelet-Rich Fibrin-PRF) for topical and infiltrative use in orthopedic and sports medicine: current consensus, clinical implications and perspectives

Platelet concentrates for topical and infiltrative use - commonly termed Platetet-Rich Plasma (PRP) or Platelet-Rich Fibrin (PRF) - are used or tested as surgical adjuvants or regenerative medicine preparations in most medical fields, particularly in sports medicine and orthopaedic surgery. Even if these products offer interesting therapeutic perspectives, their clinical relevance is largely debated, as the literature on the topic is often confused and contradictory. The long history of these products was always associated with confusions, mostly related to the lack of consensual terminology, characterization and classification of the many products that were tested in the last 40 years. The current consensus is based on a simple classification system dividing the many products in 4 main families, based on their fibrin architecture and cell content: Pure Platelet-Rich Plasma (P-PRP), such as the PRGF-Endoret technique; Leukocyte- and Platelet-Rich Plasma (LPRP), such as Biomet GPS system; Pure Platelet-Rich Fibrin (P-PRF), such as Fibrinet; Leukocyte- and Platelet-Rich Fibrin (L-PRF), such as Intra-Spin L-PRF. The 4 main families of products present different biological signatures and mechanisms, and obvious differences for clinical applications. This classification serves as a basis for further investigations of the effects of these products. Perspectives of evolutions of this classification and terminology are also discussed, particularly concerning the impact of the cell content, preservation and activation on these products in sports medicine and orthopaedics.

Histologic comparison between platelet-rich plasma and blood clot in regenerative endodontic treatment: an animal study

INTRODUCTION

In regenerative endodontic treatment (RET) for immature permanent tooth, better treatment results could be obtained by applying platelet-rich plasma (PRP) as the scaffold rather than the blood clot. The goal of this study was to compare the histologic differences between using PRP and blood clot in RET.

METHODS

Three 6-month-old beagles each carrying 9 premolars with double root canals were randomly assigned to the PRP group, blood clot group, or negative control group. All experimental teeth suffered apical periodontitis, and RET was performed. In the blood clot group, bleeding was induced from the periapical tissues to fill the canal space. In the PRP group, autologous PRP was injected into each root canal. The animals were sacrificed 3 months later. Histologic sections were stained with hematoxylin-eosin. Statistical analysis was performed by the Fisher exact test, with the significance set at 0.05.

RESULTS

With the ingrowth of cellular cementumlike tissues, the canal wall was thickened, and the apical apex was closed in both the PRP and blood clot groups. Cementocytelike cells were present in the newly formed tissues. Meanwhile, no statistical difference was found in both experimental groups for the average percentage of apical closure, new tissue formation, and pulplike tissue formation. Noticeably, a large number of inflammatory cells were present in some root canals in both groups although the postoperative radiograph revealed the disappearance of periapical radiolucency.

CONCLUSIONS

PRP application could be an option for clinical cases in which little or no bleeding were found when irritating the apical tissue during RET.

Characterization and comparison of 5 platelet-rich plasma preparations in a single-donor model

PURPOSE

The purpose of this study was to compare the biological characteristics of platelet-rich plasma (PRP) obtained from 4 medical devices and a preparation developed in our laboratory using a single-donor model.

METHODS

Ten healthy persons donated blood that was processed to produce PRP by use of 4 commercial preparation systems and a protocol developed in our laboratory. Volumes and platelet, white blood cell (WBC), and red blood cell concentrations were recorded. The platelet activation status was assessed by flow cytometry. Enzyme-linked immunosorbent assay was used to determine the concentrations of vascular endothelial growth factor, platelet-derived growth factor AB, epidermal growth factor, and transforming growth factor β1. We calculated platelet capture efficiency, relative composition, and increase factors from whole blood in platelets and WBC, as well as platelet and growth factor (GF) doses, provided from each preparation.

RESULTS

Leukocyte-rich PRP was obtained with RegenPRP (RegenLab, Le Mont-sur-Lausanne, Switzerland) and the Mini GPS III System (Biomet Biology, Warsaw, IN) and provides PRP with higher proportions of red blood cells, WBCs, and neutrophils than leukocyte-poor PRP obtained with the Selphyl System (Selphyl, Bethlehem, PA), Arthrex ACP (Arthrex, Naples, FL), and the preparation developed in our laboratory. The highest platelet and GF concentrations and doses were obtained with the Mini GPS III System and the preparation developed in our laboratory. Different centrifugation protocols did not show differences in the percentages of activated platelets. Finally, a positive correlation between platelet doses and all the GFs studied was found, whereas a positive correlation between WBC doses and GFs was found only for vascular endothelial growth factor and epidermal growth factor.

CONCLUSIONS

In a single-donor model, significant biological variations in PRP obtained from different preparation systems were highlighted. The observed differences suggest different results for treated tissue and could explain the large variability in the clinical benefit of PRP reported in the literature.

CLINICAL RELEVANCE

Our findings will help clinicians to choose a system that meets their specific needs for a given indication.

Platelet-rich therapies for musculoskeletal soft tissue injuries

BACKGROUND

Platelet-rich therapies are being used increasingly in the treatment of musculoskeletal soft tissue injuries such as ligament, muscle and tendon tears and tendinopathies. These therapies can be used as the principal treatment or as an augmentation procedure (application after surgical repair or reconstruction). Platelet-rich therapies are produced by centrifuging a quantity of the patient's own blood and extracting the active, platelet-rich, fraction. The platelet-rich fraction is applied to the injured tissue; for example, by injection. Platelets have the ability to produce several growth factors, so these therapies should enhance tissue healing. There is a need to assess whether this translates into clinical benefit.

OBJECTIVES

To assess the effects (benefits and harms) of platelet-rich therapies for treating musculoskeletal soft tissue injuries.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (25 March 2013), the Cochrane Central Register of Controlled Trials (CENTRAL 2013 Issue 2), MEDLINE (1946 to March 2013), EMBASE (1980 to 2013 Week 12) and LILACS (1982 to March 2012). We also searched trial registers (to Week 2 2013) and conference abstracts (2005 to March 2012). No language or publication restrictions were applied.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials that compared platelet-rich therapy with either placebo, autologous whole blood, dry needling or no platelet-rich therapy for people with acute or chronic musculoskeletal soft tissue injuries. Primary outcomes were functional status, pain and adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed each study's risk of bias. Disagreement was resolved by discussion or by arbitration by a third author. We contacted trial authors for clarification of methods or missing data. Treatment effects were assessed using risk ratios for dichotomous data and mean differences (MD) or standardised mean differences (SMD) for continuous data, together with 95% confidence intervals. Where appropriate, data were pooled using the fixed-effect model for RR and MD, and the random-effects model for SMD. The quality of the evidence for each outcome was assessed using GRADE criteria.

MAIN RESULTS

We included data from 19 small single centre trials (17 randomised and two quasi-randomised; 1088 participants) that compared platelet-rich therapy with placebo, autologous whole blood, dry needling or no platelet-rich therapy. These trials covered eight clinical conditions: rotator cuff tears (arthroscopic repair) (six trials); shoulder impingement syndrome surgery (one trial); elbow epicondylitis (three trials); anterior cruciate ligament (ACL) reconstruction (four trials), ACL reconstruction (donor graft site application) (two trials), patellar tendinopathy (one trial), Achilles tendinopathy (one trial) and acute Achilles rupture surgical repair (one trial). We also grouped trials into 'tendinopathies' where platelet-rich therapy (PRT) injections were the main treatment (five trials), and surgical augmentation procedures where PRT was applied during surgery (14 trials). Trial participants were mainly male, except in trials including rotator cuff tears, and elbow and Achilles tendinopathies.Three trials were judged as being at low risk of bias; the other 16 were at high or unclear risk of bias relating to selection, detection, attrition or selective reporting, or combinations of these. The methods of preparing platelet-rich plasma (PRP) varied and lacked standardisation and quantification of the PRP applied to the patient.We were able to pool data for our primary outcomes (function, pain, adverse events) for a maximum of 11 trials and 45% of participants. The evidence for all primary outcomes was judged as being of very low quality.Data assessing function in the short term (up to three months) were pooled from four trials that assessed PRT in three clinical conditions and used four different measures. These showed no significant difference between PRT and control (SMD 0.26; 95% confidence interval (CI) -0.19 to 0.71; P value 0.26; I² = 51%; 162 participants; positive values favour PRT). Medium-term function data (at six months) were pooled from five trials that assessed PRT in five clinical conditions and used five different measures. These also showed no difference between groups (SMD -0.09, 95% CI -0.56 to 0.39; P value 0.72; I² = 50%; 151 participants). Long-term function data (at one year) were pooled from 10 trials that assessed PRT in five clinical conditions and used six different measures. These also showed no difference between groups (SMD 0.25, 95% CI -0.07 to 0.57; P value 0.12; I² = 66%; 484 participants). Although the 95% confidence intervals indicate the possibility of a poorer outcome in the PRT group up to a moderate difference in favour of PRT at short- and long-term follow-up, these do not translate into clinically relevant differences.Data pooled from four trials that assessed PRT in three clinical conditions showed a small reduction in short-term pain in favour of PRT on a 10-point scale (MD -0.95, 95% CI -1.41 to -0.48; I² = 0%; 175 participants). The clinical significance of this result is marginal.Four trials reported adverse events; another seven trials reported an absence of adverse events. There was no difference between treatment groups in the numbers of participants with adverse effects (7/241 versus 5/245; RR 1.31, 95% CI 0.48 to 3.59; I² = 0%; 486 participants).In terms of individual conditions, we pooled heterogeneous data for long-term function from six trials of PRT application during rotator cuff tear surgery. This showed no statistically or clinically significant differences between the two groups (324 participants).The available evidence is insufficient to indicate whether the effects of PRT will differ importantly in individual clinical conditions.

AUTHORS' CONCLUSIONS

Overall, and for the individual clinical conditions, there is currently insufficient evidence to support the use of PRT for treating musculoskeletal soft tissue injuries. Researchers contemplating RCTs should consider the coverage of currently ongoing trials when assessing the need for future RCTs on specific conditions. There is need for standardisation of PRP preparation methods.

Platelet-rich plasma induces annulus fibrosus cell proliferation and matrix production

PURPOSE

Platelet-rich plasma (PRP) contains growth factors and creates a 3D structure upon clotting; PRP or platelet lysate (PL) might be considered for annulus fibrosus (AF) repair.

METHODS

Bovine AF cells were cultured with 25% PRP, 50% PRP, 25% PL, 50% PL, or 10% FBS. After 2 and 4 days, DNA, glycosaminoglycan (GAG), and mRNA levels were analyzed. Histology was performed after injection of PRP into an AF defect in a whole disc ex vivo.

RESULTS

By day 4, significant increases in DNA content were observed in all treatment groups. All groups also showed elevated GAG synthesis, with highest amounts at 50% PL. Collagen I and II expression was similar between groups; aggrecan, decorin, and versican expression was highest at 25% PL. Injection of PRP into the AF defect resulted in an increased matrix synthesis.

CONCLUSIONS

Platelet-rich preparations increased the matrix production and cell number and may therefore be considered to promote AF repair.

The effect of platelet-rich plasma on osteochondral defects treated with mosaicplasty

PURPOSE

This study investigated the efficacy of platelet-rich plasma (PRP) on articular surfaces on which the mosaicplasty technique was performed. Our hypothesis was that PRP can accelerate the osseointegration process and enhance the quality of articular integrity after the mosaicplasty procedure.

METHODS

Standard defects were created in the femoral groove of both patellofemoral joints of 12 New Zealand rabbits. PRP solution was placed inside the defect before fixation of the osteochondral autografts and injected inside the involved joint after capsular closure of the tested knees. The contralateral knees served as the control sides. The animals were euthanized three or six weeks after mosaicplasty, and both limbs were assessed according to Pineda's histological grading scale. Significance level was set at p ≤ 0.05 a priori, and the Mann-Whitney U test was used for statistical analysis.

RESULTS

Histologic findings at the interface between the transferred autograft and the original cartilage revealed better integration of the adjacent surfaces in the mosaicplasty with PRP group three weeks after the procedure; the difference was significant (p < 0.05). However, no significant difference in the transition zone was observed between the groups six weeks after the experiment (p = 0.59).

CONCLUSIONS

Our animal model showed that adjunctive use of PRP produced a better healing response and resulted in superior histological scores after three weeks compared with the mosaicplasty-only procedure. Interpretation of our results is important in terms of rapid return to previous activity levels. Thus, application of PRP can represent a valid therapeutic option for improving the efficacy of mosaicplasty by stimulating the local healing response.

Platelet-rich therapies for musculoskeletal soft tissue injuries

BACKGROUND

Platelet-rich therapies are being used increasingly in the treatment of musculoskeletal soft tissue injuries such as ligament, muscle and tendon tears and tendinopathies. These therapies can be used as the principal treatment or as an augmentation procedure (application after surgical repair or reconstruction). Platelet-rich therapies are produced by centrifuging a quantity of the patient's own blood and extracting the active, platelet-rich, fraction. The platelet-rich fraction is applied to the injured tissue; for example, by injection. Platelets have the ability to produce several growth factors, so these therapies should enhance tissue healing. There is a need to assess whether this translates into clinical benefit.

OBJECTIVES

To assess the effects (benefits and harms) of platelet-rich therapies for treating musculoskeletal soft tissue injuries.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (25 March 2013), the Cochrane Central Register of Controlled Trials (CENTRAL 2013 Issue 2), MEDLINE (1946 to March 2013), EMBASE (1980 to 2013 Week 12) and LILACS (1982 to March 2012). We also searched trial registers (to Week 2 2013) and conference abstracts (2005 to March 2012). No language or publication restrictions were applied.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials that compared platelet-rich therapy with either placebo, autologous whole blood, dry needling or no platelet-rich therapy for people with acute or chronic musculoskeletal soft tissue injuries. Primary outcomes were functional status, pain and adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed each study's risk of bias. Disagreement was resolved by discussion or by arbitration by a third author. We contacted trial authors for clarification of methods or missing data. Treatment effects were assessed using risk ratios for dichotomous data and mean differences (MD) or standardised mean differences (SMD) for continuous data, together with 95% confidence intervals. Where appropriate, data were pooled using the fixed-effect model for RR and MD, and the random-effects model for SMD. The quality of the evidence for each outcome was assessed using GRADE criteria.

MAIN RESULTS

We included data from 19 small single centre trials (17 randomised and two quasi-randomised; 1088 participants) that compared platelet-rich therapy with placebo, autologous whole blood, dry needling or no platelet-rich therapy. These trials covered eight clinical conditions: rotator cuff tears (arthroscopic repair) (six trials); shoulder impingement syndrome surgery (one trial); elbow epicondylitis (three trials); anterior cruciate ligament (ACL) reconstruction (four trials), ACL reconstruction (donor graft site application) (two trials), patellar tendinopathy (one trial), Achilles tendinopathy (one trial) and acute Achilles rupture surgical repair (one trial). We also grouped trials into 'tendinopathies' where platelet-rich therapy (PRT) injections were the main treatment (five trials), and surgical augmentation procedures where PRT was applied during surgery (14 trials). Trial participants were mainly male, except in trials including rotator cuff tears, and elbow and Achilles tendinopathies.Three trials were judged as being at low risk of bias; the other 16 were at high or unclear risk of bias relating to selection, detection, attrition or selective reporting, or combinations of these. The methods of preparing platelet-rich plasma (PRP) varied and lacked standardisation and quantification of the PRP applied to the patient.We were able to pool data for our primary outcomes (function, pain, adverse events) for a maximum of 11 trials and 45% of participants. The evidence for all primary outcomes was judged as being of very low quality.Data assessing function in the short term (up to three months) were pooled from five trials that assessed PRT in three clinical conditions and used four different measures. These showed no significant difference between PRT and control (SMD 0.24; 95% confidence interval (CI) -0.07 to 0.56; P value 0.13; I² = 35%; 273 participants; positive values favour PRT). Medium-term function data (at six months) were pooled from six trials that assessed PRT in five clinical conditions and used six different measures. These also showed no difference between groups (SMD 0.06; 95% CI -0.39 to 0.51; P value 0.79; I² = 64%; 262 participants). Long-term function data (at one year) were pooled from 10 trials that assessed PRT in five clinical conditions and used six different measures. These also showed no difference between groups (SMD 0.25, 95% CI -0.07 to 0.57; P value 0.12; I² = 66%; 484 participants). Although the 95% confidence intervals indicate the possibility of a slightly poorer outcome in the PRT group up to a moderate difference in favour of PRT at short- and long-term follow-up, these do not translate into clinically relevant differences.Data pooled from four trials that assessed PRT in three clinical conditions showed a small reduction in short-term pain in favour of PRT on a 10-point scale (MD -0.95, 95% CI -1.41 to -0.48; I² = 0%; 175 participants). The clinical significance of this result is marginal.Four trials reported adverse events; another seven trials reported an absence of adverse events. There was no difference between treatment groups in the numbers of participants with adverse effects (7/241 versus 5/245; RR 1.31, 95% CI 0.48 to 3.59; I² = 0%; 486 participants).In terms of individual conditions, we pooled heterogeneous data for long-term function from six trials of PRT application during rotator cuff tear surgery. This showed no statistically or clinically significant differences between the two groups (324 participants). Pooled data for short-term function for three elbow epicondylitis trials (179 participants) showed a statistically significant difference in favour of PRT, but the clinical significance of this finding is uncertain.The available evidence is insufficient to indicate whether the effects of PRT will differ importantly in individual clinical conditions.

AUTHORS' CONCLUSIONS

Overall, and for the individual clinical conditions, there is currently insufficient evidence to support the use of PRT for treating musculoskeletal soft tissue injuries. Researchers contemplating RCTs should consider the coverage of currently ongoing trials when assessing the need for future RCTs on specific conditions. There is need for standardisation of PRP preparation methods.

Basic science and clinical application of platelet-rich plasma for cartilage defects and osteoarthritis: a review

Cartilage defects (CDs) and the most common joint disease, osteoarthritis (OA), are characterized by degeneration of the articular cartilage that ultimately leads to joint destruction. Current treatment strategies are inadequate: none results in restoration of fully functional hyaline cartilage, for uncertain long-term prognosis. Tissue engineering of cartilage with auto-cartilage cells or appropriate mesenchymal stem cell (MSC)-derived cartilage cells is currently being investigated to search for new therapies. Platelet-rich plasma (PRP), an autologous source of factors obtained by centrifugation, possesses various functions. For culture of MSCs and cartilage cells, it might be substituted for fetal bovine serum (FBS) with high efficiency and safety. It enhances the regeneration of cartilage cells when added to cartilage tissue engineering constructs for repairing CDs and as regenerative injection therapy for OA. But challenges also remain. Some of the growth factors (GFs) present in PRP have negative effects on the OA joint. It is therefore unlikely that a mix of GFs some of which have negative effects in the OA joint, as present in PRP, will be of benefit in OA. Future directions of PRP application may concentrate on seeking an appropriate and innocuous agent like anti-VEGF antibody that can modulate and control the effect of PRP.

Application of Platelet-Rich Plasma to Disorders of the Knee Joint

IMPORTANCE

The promising therapeutic potential and regenerative properties of platelet-rich plasma (PRP) have rapidly led to its widespread clinical use in musculoskeletal injury and disease. Although the basic scientific rationale surrounding PRP products is compelling, the clinical application has outpaced the research.

OBJECTIVE

The purpose of this article is to examine the current concepts around the basic science of PRP application, different preparation systems, and clinical application of PRP in disorders in the knee.

EVIDENCE ACQUISITION

A systematic search of PubMed for studies that evaluated the basic science, preparation and clinical application of platelet concentrates was performed. The search used terms, including platelet-rich plasma or PRP preparation, activation, use in the knee, cartilage, ligament, and meniscus. Studies found in the initial search and related studies were reviewed.

RESULTS

A comprehensive review of the literature supports the potential use of PRP both nonoperatively and intraoperatively, but highlights the absence of large clinical studies and the lack of standardization between method, product, and clinical efficacy. Conclusions and Relevance. In addition to the call for more randomized, controlled clinical studies to assess the clinical effect of PRP, at this point, it is necessary to investigate PRP product composition and eventually have the ability to tailor the therapeutic product for specific indications.

Platelet-rich plasma for arthroscopic repair of large to massive rotator cuff tears: a randomized, single-blind, parallel-group trial

BACKGROUND

Platelet-rich plasma (PRP) is expected to have a biological augmentation potential in the healing of various diseases and injuries, including rotator cuff tears. However, few evaluations have been performed specifically for large to massive tears.

PURPOSE

To assess the efficacy of PRP augmentation in patients undergoing arthroscopic repair for large to massive rotator cuff tears.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 48 patients scheduled for arthroscopic repair of large to massive rotator cuff tears were randomly assigned to receive either PRP-augmented (PRP group) or conventional treatment (conventional group). In the PRP group, 3 PRP gels (3 × 3 mL) were applied to each patient between the torn end and the greater tuberosity. The primary outcome measure was the retear rate assessed by magnetic resonance imaging (MRI) or computed tomographic arthrography (CTA) at a minimum of 9 months after surgery. Secondary outcome measures included pain, range of motion, muscle strength, overall satisfaction, functional scores, and the change in cross-sectional area (CSA) of the supraspinatus.

RESULTS

The retear rate of the PRP group (20.0%) was significantly lower than that of the conventional group (55.6%) (P = .023). Clinical outcomes showed no statistical difference between the 2 groups (all P > .05) except for the overall function (P = .043). The change in 1-year postoperative and immediately postoperative CSA was significantly different between the 2 groups: -15.54 ± 94.34 mm² in the PRP group versus -85.62 ± 103.57 mm² in the conventional group (P = .047).

CONCLUSION

The application of PRP for large to massive rotator cuff repairs significantly improved structural outcomes, as evidenced by a decreased retear rate and increased CSA of the supraspinatus compared with repairs without PRP augmentation. While there was no significant difference in clinical outcomes except the overall shoulder function after 1-year follow-up, better structural outcomes in the PRP group might suggest improved clinical outcomes at longer term follow-up.

Supplementation with platelet-rich plasma improves the in vitro formation of tissue-engineered cartilage with enhanced mechanical properties

PURPOSE

This study aimed to determine the effects of platelet-rich plasma (PRP) on the histologic, biochemical, and biomechanical properties of tissue-engineered cartilage.

METHODS

Chondrocytes isolated from bovine metacarpal-phalangeal articular cartilage were seeded on top of a porous ceramic substrate (calcium polyphosphate [CPP]). Cultures were supplemented with fetal bovine serum (FBS), PRP, or platelet-poor plasma (PPP) at 5%. On day 5, the concentration was increased to 20%. PRP and PPP were obtained through centrifugation of whole blood withdrawn from a mature cow. After 2 weeks, samples (n = 8) were analyzed histologically, biochemically, and biomechanically. Data were analyzed using the Wilcoxon test (significance, P < .05).

RESULTS

Chondrocytes cultured in 20% PRP formed thicker cartilage tissue (1.6 ± 0.2 mm) than did cells grown in 20% FBS (0.7 ± 0.008 mm; P = .002) and 20% PPP (0.8 ± 0.2 mm; P = .03). Cartilage tissue generated in the presence of 20% PRP had a greater equilibrium modulus of 38.1 ± 3.6 kPa versus 15.6 ± 1.5 kPa (P = .0002) for 20% PPP and 20.4 ± 3.5 kPa (P = .007) for 20% FBS. Glycosaminoglycan (GAG) content was increased in tissues formed in 20% PRP (176 ± 18.8 μg GAG/mg) compared with those grown in 20% FBS (112 ± 10.6 μg GAG/mg; P = .01) or 20% PPP (131.5 ± 14.8 μg GAG/mg; P = .11). Hydroxyproline content was similar whether the media was supplemented with 20% PRP (8.7 ± 0.9 μg/mg), 20% FBS (7.6 ± 0.9 μg/mg; P = .37), or 20% PPP (6.4 ± 1 μg/mg; P = .28). DNA content was similar in all tissues whether formed in 20% PRP (11.9 ± 3.5 μg/mg), 20% FBS (9.3 ± 2.5 μg/mg; P = .99), or 20% PPP (7.2 ± 1.3 μg/mg; P = .78). Immunostained samples showed prevalence of type II collagen in tissues formed in the presence of 20% PRP.

CONCLUSIONS

The presence of PRP in the culture media enhances the in vitro formation of cartilage, with increased GAG content and greater compressive mechanical properties, while maintaining characteristics of hyaline phenotype.

CLINICAL RELEVANCE

Understanding the in vitro effects of PRP on tissue-engineered cartilage may lead to the creation of engineered cartilage tissue with enhanced properties suitable for cartilage repair.

Safety and efficient ex vivo expansion of stem cells using platelet-rich plasma technology

The goal of this Review is to provide an overview of the cell culture media supplements used in the ex vivo expansion of stem cells intended for cell therapy. Currently, the gold standard is the culture supplemented with fetal bovine serum, however, their use in cell therapy raises many concerns. The alternatives to its use are presented, ranging from the use of human serum to platelet-rich plasma (PRP), to serum-free media or extracellular matrix components. Finally, various growth factors present in PRP are described, which make it a safe and effective stem cell expansion supplement. These growth factors could be responsible for their efficiency, as they increase both stem cell proliferation and survival. The different PRP formulations are also discussed, as well as the need for protocol standardization.

A biological therapy to osteoarthritis treatment using platelet-rich plasma

INTRODUCTION

Osteoarthritis (OA) is a degenerative disease affecting the synovial joint. It is caused by cells exposure to non-physiological stimuli, either mechanical or biochemical, and the loss of bone-cartilage homeostasis. Some of these changes, however, may be reversed by the use of single or combined growth factors, suggesting that the treatment of OA could be addressed using a pool of growth factors.

AREAS COVERED

This review addresses current molecular and biological knowledge and implicates the recapitulation of some developmental processes during endochondral ossification in OA aetiology and pathogenesis. Platelets act as carriers of endogenous morphogens that may modulate cell fate and therefore affect joint tissues structure and function. We shed light on the platelet-rich plasma effects on biological level that might drive the osteoarthritic joint's improvement both in structure and function.

EXPERT OPINION

We present the therapeutic potential of plasma rich in growth factors (PRGF-Endoret), an endogenous biological therapy that might modulate the gene expression of cells such as chondrocytes, synoviocytes, macrophages, and mesenchymal stem cells, and thereby influence an anabolic microenvironment of synovial joint which is conducive to maintaining the homeostatic state of the joint's tissues, and hence reduce pain and improve the joint motion.

Synovial membrane-derived mesenchymal stem cells supported by platelet-rich plasma can repair osteochondral defects in a rabbit model

PURPOSE

The aim of this study was to determine the in vivo effectiveness of synovial membrane-derived mesenchymal stem cell (SDSC)-encapsulated injectable platelet-rich plasma (PRP) gel in the repair of damaged articular cartilage in the rabbit.

METHODS

An osteochondral defect was created in the trochlear groove of the rabbit femur, and the defects were divided into 3 treatment groups: untreated control group, PRP group, and PRP-SDSC group. After 4, 12, and 24 weeks, the tissue specimens were assessed by macroscopic examination and histologic evaluation and stained immunohistochemically for type II collagen and proliferating cell nuclear antigen. In addition, total glycosaminoglycan content was determined at 24 weeks.

RESULTS

Rabbit PRP contained a high concentration of platelets and high concentration of growth factors compared with those in whole blood. Twenty-four weeks after transplantation, there was fibrous tissue in the control group. In both the PRP group and the PRP-SDSC group, the defects were repaired with hyaline cartilage and exhibited significantly higher safranin O staining, type II collagen immunostaining, glycosaminoglycan content, cumulative histologic scores, and number of proliferating cell nuclear antigen-positive cells. However, incomplete bone regeneration and irregular cartilage surface integration were observed in the PRP group.

CONCLUSIONS

Our results indicate that SDSC-embedded PRP gel could successfully resurface the defect with cartilage and restore the subchondral bone in the rabbit model.

CLINICAL RELEVANCE

This study indicates that in an animal model, the application of PRP and SDSC in combination for the treatment of local cartilage defects appears promising; however, PRP-SDSC products might be more or less appropriate to treat different types of tissues and pathologies. The clinical efficacy of PRP remains under debate. Therefore further research is needed at both the basic science and clinical levels.

Platelet-rich plasma in tendon models: a systematic review of basic science literature

PURPOSE

To perform a systematic review of the basic science literature on the use of platelet-rich plasma (PRP) in tendon models.

METHODS

We searched the PubMed/Medline and Embase databases in June 2012 using the following parameters: ((tenocytes OR tendon OR tendinitis OR tendinosis OR tendinopathy) AND (platelet rich plasma OR PRP OR autologous conditioned plasma OR ACP)). The inclusion criteria for full-text review were in vivo and in vitro studies examining the effects of PRP on tendons and/or tenocytes. Clinical studies were excluded. Only studies published in peer-reviewed journals that compared PRP directly with a control were included. Data were extracted based on a predefined data sheet, which included information on PRP preparation, study methods, and results. Studies were analyzed for trends, comparing and contrasting the reported effects of PRP.

RESULTS

The search yielded 31 articles for inclusion in our review. Of the studies, 22 (71%) reported platelet concentrations in the PRP; 6 (19%) reported cytology. Eight in vivo studies found decreased tendon repair time, increased fiber organization, or both with PRP treatment. Eight in vitro studies reported that PRP treatment increased cell proliferation; 7 reported an increase in growth factor expression. Three in vivo studies found increased vascularity, and 4 found increased tensile strength with PRP treatment.

CONCLUSIONS

In the basic science studies evaluated, it appears that PRP confers several potential effects on tendon models compared with a control. However, the literature is inconsistent with regard to reporting the methods of preparation of PRP and in reporting platelet concentrations and cytology.

CLINICAL RELEVANCE

Establishing proof of concept for PRP may lead to further high-quality clinical studies in which the appropriate indications can be defined.

Can platelet-rich plasma (PRP) improve bone healing? A comparison between the theory and experimental outcomes

The increased concentration of platelets within platelet-rich plasma (PRP) provides a vehicle to deliver supra-physiologic concentrations of growth factors to an injury site, possibly accelerating or otherwise improving connective tissue regeneration. This potential benefit has led to the application of PRP in several applications; however, inconsistent results have limited widespread adoption in bone healing. This review provides a core understanding of the bone healing mechanisms, and corresponds this to the factors present in PRP. In addition, the current state of the art of PRP preparation, the key aspects that may influence its effectiveness, and treatment outcomes as they relate specifically to bone defect healing are presented. Although PRP does have a sound scientific basis, its use for bone healing appears only beneficial when used in combination with osteoconductive scaffolds; however, neither allograft nor autograft appear to be appropriate carriers. Aggressive processing techniques and very high concentrations of PRP may not improve healing outcomes. Moreover, many other variables exist in PRP preparation and use that influence its efficacy; the effect of these variables should be understood when considering PRP use. This review includes the essentials of what has been established, what is currently missing in the literature, and recommendations for future directions.

Effect of autologous platelet-rich plasma-releasate on intervertebral disc degeneration in the rabbit anular puncture model: a preclinical study

INTRODUCTION

Platelet-rich plasma (PRP) is a fraction of plasma in which several growth factors are concentrated at high levels. The active soluble releasate isolated following platelet activation of PRP (PRP-releasate) has been demonstrated to stimulate the metabolism of IVD cells in vitro. The in vivo effect of PRP-releasate on degenerated IVD remains unknown. The purpose of this study was to determine the reparative effects of autologous PRP-releasate on degenerated intervertebral discs (IVDs).

METHODS

To induce disc degeneration, New Zealand white rabbits (n = 12) received anular puncture in two noncontiguous discs. Autologous PRP and PPP (platelet-poor plasma) were isolated from fresh blood using two centrifugation techniques. Four weeks after the initial puncture, releasate isolated from clotted PPP or PRP (PPP- or PRP-releasate), or phosphate-buffered saline (PBS; control) was injected into the punctured discs. Disc height, magnetic resonance imaging (MRI) T2-mapping and histology were assessed.

RESULTS

Anular puncture produced a consistent disc narrowing within four weeks. PRP-releasate induced a statistically significant restoration of disc height (PRP vs. PPP and PBS, P<0.05). In T2-quantification, the mean T2-values of the nucleus pulposus (NP) and anulus fibrosus (AF) of the discs were not significantly different among the three treatment groups. Histologically, the number of chondrocyte-like cells was significantly higher in the discs injected with PRP-releasate compared to that with PBS.

CONCLUSIONS

The administration of active PRP-releasate induced a reparative effect on rabbit degenerated IVDs. The results of this study suggest that the use of autologous PRP-releasate is safe and can lead to a clinical application for IVD degeneration.