OBJECTIVETo investigate the biomechanics effect due to unilateral cortical bone defect of different size in long tubular bone.

METHODSSeventy-six pieces of Sanhuang cock tibial were randomly divided into 7 groups. The unilateral diaphyses cortical were drilled holes of different size, include 1.5, 2.0, 2.5, 3.0, 3.5, and 4.5 mm, performed three-points bend single experiment. The intact bone cortical group was control group.

RESULTSWhen there were bone structure destructions, the maximum of the bend load between 3 groups which bone defect diameter were 1.5 mm, 2.0 mm, and control was not significant difference (P = 0.824, 0.865), but the maximum of the bend load between 3 groups which bone defect diameter were 2.5, 3.0, and 3.5 mm decreasing about 14 percent of the control group (P = 0.015, 0.010, 0.021). and the maximum of the bend load which bone defect diameter were 4.5 mm decrease about 23 percent of the control group (P = 0.001).

CONCLUSIONSIf the diameter of bone cortical defect is within 22.63 +/- 1.39 percent of bone cortical outer diameter, there was no reduction of the bend load. If the diameter of bone cortical defect is beyond 29.36 +/- 2.07 percent of bone cortical outer diameter, it decreases the maximum bend load of the long tubular bone, but the reduced range is not complete with direct ratio to the bone defect size.