RELATIONSHIP BETWEEN BONE-PROSTHESIS BONDING AND LOAD-TRANSFER IN TOTAL HIP RECONSTRUCTION

The effect of bone-prosthesis bonding on proximal load transfer is inv estigated using a coupled experimental and finite element analysis on a synthetic femur. Three-dimensional finite element models for an inta ct femur and a femur implanted with a cementless prosthesis were const ructed from the experimental models used, and the proximal femoral str ains recorded for two loading conditions approximating a one-legged st ance. The approach was used to investigate a press-fitted and a fully bonded bone-prosthesis structure to identify the stem-bone behaviour f or both interface conditions and their implications for proximal bone load transfer. Regression slopes close to unity indicated that the fin ite element predictions were an accurate estimate of the experimental measurements. Physiological surface strains were recorded only when th e abductor force was included in the loading, Meanwhile, experimental measurements and numerical predictions showed that a different load tr ansfer pattern is to be expected for normally press-fitted and glued p ress-fitted stems. The finite element model for the treated femur, mod elling both interface conditions correlated very well with the experim ental model. These finite element models subsequently modified and use d to analyse the effect of different interface conditons predicted a s ignificant increase in the load transfer to the proximal calcar bone w hen only proximal bonding is achieved. This study suggests that inform ation obtained for the assessment and prediction of total hip arthropl asty longevity by numerical and experimental techniques used together and in parallel is of greater value than either technique used alone. The employment of a femur analogue as featured in this study is also s hown to be a suitable alternative to cadaveric specimens in such an an alysis. (C) 1997 Elsevier Science Ltd.