OBJECTIVE

To study the effect of the high molecular weight polyethylene on the periprosthetic tissue in vivo as to give some reference to treatment of loosening hip arthroplasty.

METHODS

Every lower limb of 20 New Zealand white rabbits was implanted a Co-Cr-Mo plug in femur by intercondylar notch. 15 mg polyethylene particles, dispersed in 1.5 ml normal saline solution, were injected into one knee joint. The other knee joint was injected 1.5 ml normal saline solution as control. This procedure was repeated 2,4,6,8 and 10 weeks after the implantation. Both of two lower limbs were given a X-ray examination 10 weeks to assess if there were periprosthetic osteolysis and loosening of the plugs. All animals were killed 2 weeks afer the last injection. The distribution of polyethylene in the knee joint capsule was examined to understand if there were loosening of implants or tissue change around implants. Knee joint capsule tissues and periprosthetic tissues were examined by optical microscope.

RESULTS

Nine cases formed fibrous membrane and four cases formed new bone around prostheses in experiment group. Eleven cases formed new bone and two cases formed fibrous membrane in control group (P < 0.05) The X-ray results indicated that the plugs were in distal medulla of femur. There was no sign of periprosthetic osteolysis, implants loosening or new bone formation. Optical microscope study indicated that there were a lot of polyethylene particles inside the capsule. The polyethylene particles were surrounded by multinucleated foreign-body giant cells and fibroblast. In some cases, there were fibroblasts and fibrous tissue around plug. There were no polyethylene particles and multinucleated foreign-body giant cells around plug in the marrow. There were a lot of polyethylene particles on the joint surface. The bone surface that contacted multinucleated foreign-body giant cells was coarse.

CONCLUSION

Maximizing ultra high molecular weight polyethylene can restrain rabbit periprosthetic bone formation.