Background: Alternative methods of platelet‐rich plasma (PRP) preparation, storage, and activation that can be stably reproduced are needed to improve PRP production. The purpose of this study was to investigate the effect of the preparer’s experience on the quality of prepared PRP, chronological changes occurring in PRP, and the effect of the activation procedures on the release of several growth factors from PRP, using PRP prepared with the PRGF‐Endoret Kit.Methods: Leukocyte‐poor PRP samples from seventeen healthy volunteers were prepared using the PRGF‐Endoret Kit and the PRGF IV System Centrifuge. The platelet and leukocyte concentrations were compared based on the preparer’s experience. The concentrations of platelets, hepatocyte growth factor (HGF), platelet‐derived growth factor‐BB (PDGF‐BB), and insulin‐like growth factor‐1 (IGF‐1) were determined at 0 and 60 min after PRP preparation, and compared. Concentrations of the above growth factors from PRP activated by freeze–thaw cycling and by calcium chloride (CaCl₂) were also compared.Results: No significant difference was observed in the platelet concentrations and leukocyte contamination rates, based on the preparer’s experience. At 60 min after PRP preparation, the platelet concentration decreased significantly, while the HGF, PDGF‐BB, and IGF‐1 concentrations remained unchanged. Activation with CaCl₂ resulted in a significant increase in the PDGF‐BB levels, although the HGF and IGF‐1 concentrations remained unchanged.Conclusions: The results of this study show that leukocyte‐poor PRP prepared using the PRGF‐Endoret Kit did not result in any qualitative difference that depended on the experience of the preparer. However, PRP preparation required standardization in terms of the time of blood count measurement. Growth factor concentrations in PRP differed according to the platelet‐activation method used.

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.

Purpose: The Masquelet technique is a recent novel treatment for severe bone defects. Polymethylmethacrylate (PMMA) has been used as a spacer for bone defects, but the optimal spacer is still unknown. Therefore, this study aimed to histologically evaluate the membranes induced by bone wax and PMMA spacers and compare them with respect to bone formation. Methods: In this study, bone defects were created in the femurs of Sprague–Dawley rats, and bone wax and PMMA spacers were implanted into the defects to histologically evaluate the induced membrane and bone formation after bone grafting. Results: As a result, the induced membrane formed by bone wax spacers was significantly thicker than that formed by PMMA spacers, and the vascular area ratio was significantly higher. In addition, bone wax spacers promoted bone formation more than PMMA spacers. Conclusion: Bone wax spacers promoted induced membrane formation and bone formation by enhancing inflammatory responses more than PMMA spacers.

Background and Objectives: Although hybrid closed-wedge high tibial osteotomy (HTO) is an effective procedure for varus knee osteoarthritis, delayed bone union is a frequent occurrence. The rate of bone union and its associated factors remain unclear. This study aimed to investigate the detailed process of bone union in hybrid closed-wedge HTO using computed tomography (CT) and to examine factors associated with delayed bone union. Materials and Methods: We retrospectively reviewed 53 consecutive patients who underwent hybrid closed-wedge HTO. Cases with no bone union at any of five sites (anterior flange, posterior, lateral, hinge, and medial) on coronal and sagittal computed tomography at 3 months postoperatively were defined as delayed bone union. Regression analysis was performed with delayed bone union as the dependent variable and sex, age, height, body weight, body mass index, correction distance, smoking, and diabetes mellitus as independent variables. Results: Among 50 analyzed knees (mean age, 61.4 ± 7.8 years), 17 (34.0%) had delayed bone union at 3 months postoperatively and one knee had screw breakage. Sex was the only significant factor associated with delayed bone union (male: β = 2.1, p < 0.004). Conclusions: Delayed bone union (absence at 3 months after hybrid closed-wedge high tibial osteotomy) occurred in 34% of patients, and male sex was associated with delayed bone union.