An in vivo rat model of self-control continuous intramedullary infusion of ultra-high molecular weight polyethylene particles by osmotic pumps

SummaryMechanisms and treatment of wear particle induced prosthetic aseptic loosening remain under investigation, as current animal models are not yet entirely favourable for researches because of individual differences or particle count differences. A new rat model of self-control continuous intramedullary infusion of ultra-high molecular weight polyethylene particles by osmotic pumps has been established in order to provide a more reliable model without the limitations mentioned above. Ten male Sprague–Dawley rats were used in this present study. A Kirschner wire and a hollow needle were placed into the medullary cavity of each femur. Two osmotic pumps containing different materials were implanted in the back of the rats, and the polyvinyl tubing connected with each side of the pumps was led subcutaneously to the knee joint and connected to the exposed needle. Radiological examination, histological analysis, tartrate-resistant acid phosphatase staining, immunohistochemistry, and biomechanical evaluation were performed 6 weeks after surgery. The mean optical density of the left femurs (control side) was 199.43 ± 62.36, whereas that of right femurs (treatment side) was 164.98 ± 26.47 (p < 0.05). The treatment side presented thinner new bone and more obvious interface membrane compared with the control side. There was a marked reduction in tartrate-resistant acid phosphatase+ cells (11.1 ± 2.5) in the control side in comparison with the treatment side (21.3 ± 3.9; p < 0.05). The integral optical density of the receptor activator of the nuclear factor-κB protein in the control side (9800.4 ± 1553.6) was less than that in the treatment side (32351.4 ± 3916.3; p < 0.05). The pull-out force was 1.14 ± 0.08 N in the control side and 0.66 ± 0.14 N in the treatment side (p < 0.05). Continuous infusion of ultra-high molecular weight polyethylene particles into the rat bone-implant interface simulated the clinical scenario of local polymer wear particle generation and delivery in humans.