Plate and bone stresses for single- and double-plated femoral fractures

Abstract

The lateral to medial distribution of axial stresses in the plate and bone of single- and double-plated femoral fractures was analyzed using composite beam theory and internal force methods. The loading conditions used were consistent with those derived by Rybicki et al. (1972) for the one-legged stance phase of gait. Three situations at the fracture site were examined: (1) no bone contact (e.g. bone defect or severely comminuted fracture), (2) bone contact with bone able to transmit only compressive stresses (e.g. simple transverse fracture), and (3) healed fracture with bone able to transmit tensile and compressive stresses. Results indicated that single plating with an ASIF broad plate on the lateral aspect without bone contact may lead to immediate plate failure. Single-plating with bone contact can cause a 46% reduction in maximum compressive stress in the medial cortex of the bone during gait. Double-plating with no bone contact results in low plate stresses. However, after healing the bone stresses in the double-plate femur are reduced by over 90% compared with the stresses in the unfractured femur.