An Experimental Technique for the Investigation of Three-Dimensional Stress in Bone Cement Underlying a Tibial Plateau

The technique of experimental model testing was applied to the analysis of stress at selected sites in bone cement underlying a tibial plateau. The investigation utilized a large model knee fabricated from materials which had mechanical properties similar to the actual tibial plateau and acrylic cement but which did not duplicate adequately the complexity of bone. A porous interface was created in the model between the materials representing the bone and cement. Three-dimensional strain rosettes were embedded into the cement and the model was loaded in a varus or valgus mode. Overloading resulted in breakdown of the modelled anterior and part of the posterior cement-bone interfaces, producing non-linear and in some cases erratic strains in the anterior section but repeatable linear results in the posterior section. The investigation highlighted the necessity for three-dimensional strain gauge investigations as opposed to two-dimensional studies. It is suggested that the approach could provide comparative information about different products and form the basis for a valuable design tool.