Abstract 32

THE EFFECTS OF OVARIECTOMY AND POLYETHYLENE WEAR DEBRIS ON FRACTURE HEALING IN A RODENT MODEL

Rajaratnam R., Yee G., Yu Y., Matthews J B., Ingham E., Walsh W R

Orthopaedic Research Laboratories, Prince of Wales Hospital, University of New South Wales, Sydney, NSW, Australia

Several complications arise associated with total hip arthroplasties including fractures and loosening with a high incidence occurring in osteoporotic patients. The healing of these fractures can be further complicated by the presence of wear debris. This study examines the effect of PE wear debris placed directly into a closed fracture site in an oestrogen deficient rodent model.

At 22 weeks of age, a standard closed right femur fracture was produced in fifty ovx and fifty sham Sprague-Dawley rats following fixation with a k-wire.

1cm<³ Ceridust combined with Hyaluronic acid and sterile saline in a 1:2 ratio was injected directly into the fracture site percutaneously. Control animals received comparable injections excluding the Ceridust. Time-points were 1, 3 and 6 weeks.

DEXA revealed a significant reduction in BMC and BMD (p<0.05) in the left, non-fractured femurs in the sham and ovx animals at 3 and 6 weeks respectively. No statistical differences (p>0.05) in the ultimate load or stiffness were observed between the control and PE treated fractures at either time-point.

Control ovx fractures showed more cartilage than the sham group at 3 weeks and delayed remodelling at 6 weeks. While the ovx group injected with PE debris showed more fibrous tissue at the fracture gap and inside the diaphysis tunnel showing further delayed healing compared to the sham group with PE.

Our data suggests that delayed healing was evident in the oestrogen deficient group with further delays due to the presence of the PE wear debris.

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