The incorporation of platelet rich plasma (PRP) in the treatment of various musculoskeletal conditions has increased exponentially over the past decade. While described most often as an augment or treatment for tendinopathies and acute tendon injuries, more recently, PRP has been described as an adjunct to arthroplasty procedures, mostly with respect to knee arthroplasty. In the shoulder, only a single study has been published, in which Zavadil and colleagues performed a randomised study of 40 patients undergoing total shoulder arthroplasty undergoing either treatment with autologous platelet gel and platelet poor plasma (n=20) or undergoing no biologic treatment (control group, n=20). The authors noted that the treatment group had significantly lower pain scores, less pain medication requirements, and improved internal rotation when compared to controls; in addition, there were no significant differences in post-operative (compared to pre-operative) hemoglobin levels or length of stay. The vast majority of arthroplasty studies discussing PRP analyze the impact of treatment on wound healing, post-operative pain, post-operative range of motion, and need for post-operative blood transfusions. Unfortunately, due to the substantial variability of methodology (not all PRP preparations are the same) in the available studies as well as the variability in outcomes reporting, direct comparison between different studies is not feasible. Here, we discuss the basic science elements of PRP relevant to arthroplasty, the variability of PRP solutions, the specific applications of PRP in arthroplasty, and the latest clinical outcomes analyses of patients undergoing PRP therapy in conjunction with shoulder arthroplasty

The use of platelet-leukocyte gel (PLG), made from platelet rich plasma, to stimulate bone formation and wound healing has been investigated extensively. As leukocytes play an important role in the innate host-defence, we hypothesised that PLG might also have antimicrobial properties. The purpose of this study was to investigate the antimicrobial activity of PLG against Staphylococcus aureus in an in vitro experiment. To determine the contribution of myeloperoxidase (MPO), present in leukocytes, in this process, MPO release was measured. Platelet rich plasma (PRP) was prepared from whole blood of 6 donors. In this process platelet poor plasma (PPP) was obtained as well. PLG was prepared by mixing PRP with either autologous (PLG-AT) or bovine thrombin (PLG-BT). The antimicrobial activity of PLG-AT, PLG-BT, PRP and PPP was determined in a bacterial kill assay, containing 1x106 CFU/ml of Staphylococcus aureus, during a 24-hour period. MPO release was measured by ELISA. Cultures showed a rapid decrease in the number of bacteria in the presence of both PLG-AT and PLG-BT, which was maximal between 4 and 8 hours, to approximately 1% of the bacteria in controls. Also PRP and PPP induced a statistically significant bacterial kill, but the effect of PLG-AT was the largest (p=0.093 vs. PLG-BT; p=0.004 vs. PRP and p< 0.001 vs. PPP). PLG-AT, PLG-BT and PRP showed a comparable, gradually increasing MPO release for 8 to 12 hours. Some MPO was also measured in the PPP samples. No correlation between MPO release and bacterial kill could be found. PLG appears to have potent antimicrobial capacity, but the role of MPO in this activity is questionable. PLG might represent a useful strategy against postoperative infections. Further research should investigate its antimicrobial capacity in the in vivo situation

Summary Statement. An autologous thrombin activated 3-fold PRP, mixed with a biphasic calcium phosphate at a 1mL:1cc ratio, is beneficial for early bone healing in older age sheep. Introduction. The management of bone defects continues to present challenges. Upon activation, platelets secrete an array of growth factors that contribute to bone regeneration. Therefore, combining platelet rich plasma (PRP) with bone graft substitutes has the potential to reduce or replace the reliance on autograft. The simple, autologous nature of PRP has encouraged its use. However, this enthusiasm has failed to consistently translate to clinical expediency. Lack of standardisation and improper use may contribute to the conflicting outcomes reported within both pre-clinical and clinical investigations. This study investigates the potential of PRP for bone augmentation in an older age sheep model. Specifically, PRP dose is controlled to provide clearer indications for its clinical use. Methods. Eighty 11mm diameter defects of 20mm in depth were created in the cancellous bone within the epiphyseal region of the medial proximal tibia and distal femur of twenty five-year-old sheep. The defects were treated with three doses of an autologous thrombin activated PRP combined with a biphasic calcium phosphate (BCP). Activated platelet poor plasma (PPP) and the BCP alone provided reference groups, while the autograft and empty defects served as controls. All animals were sacrificed at four weeks post-operatively for radiographic assessment, micro-computed tomography quantification, histological assessment, histomorphometric quantification of new bone area and bone ingrowth, and weekly fluorochrome bone label quantification. TGF-β1 concentrations were quantified using enzyme-linked immunosorbent assays. Results. The PRP had a 2.9-fold (0.4) increase in platelet concentration, a 0.57-fold (0.09) decrease in leukocytes, and a 0.65-fold (0.11) decrease in fibrinogen. After activation, the PRP had an 8.9-fold (1.5) increase in TGF-β1 serum concentration above baseline. Eleven (11) mm diameter cancellous bone defects in the hind legs of five-year-old sheep do not spontaneously heal within four weeks. PRP dose had a significant effect on the radiographic grade. The highest dose of PRP treatment had a significantly greater micro-CT BV/TV over the BCP alone (PRP: 30.6±1.8%; BCP: 24.5±0.1%). All doses of PRP treatment were significantly greater than the BCP alone for both the histomorphometric new bone area (PRP: 14.5±1.3%; BCP: 9.7±1.5%) and bone ingrowth depth (PRP: 2288±210µm; BCP:1151±268µm). From week two onwards, PRP had a significant effect on the weekly bone ingrowth over BCP, however, autograft had the greatest amount of fluorescently labelled bone within the first three weeks. PRP has a significant effect on the shape and density of osteoblasts within the central region of the defect compared to the BCP alone, however, was not significantly different to autograft. TGF-β1 appeared a better predictor of healing outcomes than platelet concentration, however both had relatively weak correlations (r<.324). Conclusion. PRP induces new bone formation with a dose dependant response at four weeks when used with a biphasic calcium phosphate in older age sheep