Stress analyses after femoral shaft osteotomy fixed by various plates with different rigidities in simulation test.

Three pairs of human cadaver femora were used for strain measurement under a weight-bearing simulation test, which was performed on intact bone and osteotomized bone fixed by 3 types of plates with different rigidities respectively. The plates with uniform thickness did not adhere to the uniform stress distribution along the plate. The stress between both central screw holes was significantly great. However, the device of trapezoidal plate conformed to the uniform stress distribution along it, and the safety factors of 3 different types of the plates were proposed. The osteotomy site was mainly subjected to compression stress in standing phase with load on both femora, but subjected to bending stress mostly with load on the single femur. The total compression strain at the osteotomy site was greater than that on intact bone while the load was adding over twice body weight with load on both legs, and nearly normal with load on one leg. We believe that the bone structural changes caused by stress shielding and limb disuse etc can be overcome by using optimal plate and normal weight bearing.