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The current research on seed cells and scaffold materials of bone tissue engineering has achieved milestones. Nevertheless, necrosis of seed cells in center of bone scaffold is a bottleneck in tissue engineering. Therefore, this study aimed to investigate the in vivo inosculation mechanism of recipient microvasculature and prevascularized outgrowth endothelial progenitor cells (OECs)-demineralized bone matrix (DBM) complex. A dorsal skinfold window-chamber model with tail vein injection of Texas red-dextran was established to confirm the optimal observation time of microvessels. OECs-DBM complex under static and dynamic perfusion culture was implanted into the model to analyze vascularization. OECs-DBM complex was harvested on 12th day for HE staining and fluorescent imaging. The model was successfully constructed, and the most appropriate time to observe microvessels was 15 min after injection. The ingrowth of recipient microvessels arcoss the border of OECs-DBM complex increased with time in both groups, and more microvessels across the border were observed in dynamic perfusion group on 3rd, 5th, 7th day. Fluorescent integrated density of border in dynamic perfusion group was higher at all-time points, and the difference was more significant in central area. Fluorescent imaging of OECs-DBM complex exhibited that no enhanced green fluorescent protein-positive cells were found beyond the verge of DBM scaffold in both groups. In vitro prevascularization by dynamic perfusion culture can increase and accelerate the blood perfusion of OECs-DBM complex obtained from recipient microvasculature by internal inosculation. Accordingly, this approach may markedly contribute to the future success of tissue engineering applications in clinical practice.

Background Avulsion fracture of the tibial intercondylar eminence is a rare injury, which mainly occurs in adolescents aged 8–14 years and in those with immature bones. The current commonly used surgery may result in severe surgical trauma, affecting knee joint function and accompanied by serious complications. In this study, we described an all-inside and all-epiphyseal arthroscopic suture fixation technique for a patient to treat tibial intercondylar eminence fracture. Methods ETHIBOND EXCEL-coated braided polyester sutures were used for fixation. Three ETHIBOND sutures were passed through the ACL at 2, 6 and 10 o’clock of the footprint of the ACL and made a cinch-knot loop separately. Under the guidance of ACL tibial locator, three corresponding tibial tunnels were drilled with K-wires at 2, 6 and 10 o’clock of the fracture bed, and the two ends of the suture were pulled out through the tunnel with double-folded steel wire heads. After reduction of the tibial eminence, three sutures were tightened and tied to the medial aspect of the tibial tubercle. Results After all the surgical treatments surgically performed by this method and following a standard postoperative protocol, our patient's ROM, stability, and functional structural scores all improved significantly. Conclusion This three-point suture technique provides a suitable reduction and stable fixation and is suitable for patients with all types of avulsion fractures of the tibial intercondylar eminence.