An animal model of osteolysis

Objective To develop a rat model of bone dissolution for research into prevention and control of osteolysis around a prosthesis.Methods Thirty male SD rats were randomized into an experimental group,a sham operation group and a control group.In the experimental group,the knee joint was exposed via a medial para-patellar incision.A hole of 1.5 nun in diameter and 1.5 cm in length was drilled from the femoral intercondylar notch through the femoral medullary canal.Gelatin gel containing polyethylene particles was injected into the hole at a dose of 200 μL/rat followed by insertion of a titanium rod (1.2 mm in diameter and 1.5 cm in length).The excessive gelatin extruded out of the hole was removed before the hole was covered with bone wax.In the sham operation group,the wound was sutured with nothing inserted after the hole was drilled and covered with bone wax.No measures were taken in the control group.All the rats were euthanized at 7 weeks after surgery to obtain samples of the serum and right femur.The serum levels of Trap-5b(tartrate-resistant acid phosphatase 5b),Ca(calcium),P(Phosphorus) and ALP(alkaline phosphatase) were observed and radiological and histopathological analyses were conducted.Results X-ray showed phenomenon of osteolysis around the titanium rod in the femur in the experimental group.Histopathological observation also showed obvious bone resorption around the rod in the experimental group.The other 2 groups showed normal radiological and histopathological observations.The serum level of Trap5b was significantly higher and the ALP level was significantly lower in the experimental group than in the other 2 groups ( P ＜ 0.05).Conclusion Since the rat model can result in osteolysis around a prosthesis,it can be used for further research on sterile loosening of a joint prosthesis. Key words: Prosthesis;  Polyethylene;  Models, animal;  Rats