BIODEGRADABLE PLATE FIXATION OF RABBIT FEMORAL-SHAFT OSTEOTOMIES - A COMPARATIVE-STUDY

Femoral shaft transverse osteotomies in 58 rabbits were fixed with ult rahigh strength poly-L-lactic acid plates made by a drawing technique. Similar osteotomies in another 35 rabbits were fixed using stainless steel plates. The union rate, the mechanical strength of the united bo nes, bone mineral content and density in the area beneath the plate us ing dual energy xray absorptiometry, and the cortical thickness beneat h and opposite the plate using a digitizer was compared between the po ly-L-lactic acid and stainless steel groups after postoperative period s of 8, 25, and 40 weeks. The poly-L-lactic acid and stainless steel g roups showed union rates of 67% (39 of 58) and 80% (28 of 35) without displacement, respectively. In the poly-L-lactic acid group, plate fai lure occurred in 14% (8 of 58). The mechanical strength of the specime n was restored to a level equal to that on the untreated side by 25 we eks, and cortical thickness and bone mineral content and density were maintained almost normal for 40 weeks in the poly-L-lactic acid group. The stainless steel group showed significantly lower mechanical stren gth and led to osteopenia because of stress shielding after 25 weeks.