Investigation into the affect of cementing techniques on load transfer in the resurfaced femoral head: a multi-femur finite element analysis.

BACKGROUND: Femoral head resurfacing is a popular procedure for younger active hip replacement patients. Two major cementing techniques are used in femoral component fixation; producing varying cement mantle thicknesses. Each technique has benefits, but it is not known if cement mantle thickness is detrimental to load transfer within the proximal femur.
METHODS: This study uses computer tomography based finite element analysis to determine the effect of cement mantle thickness on strain in the resurfaced femoral head. A group of 16 femurs were investigated to take into account inter-patient variation; a factor often over-looked in such studies.
FINDINGS: Results showed strain in the proximal femoral head to decrease with increasing cement thickness, with a slight increase in strain in the posterior-superior neck. Cementing of the implant guide-pin produced marked reductions in strain in the head and neck except for the posterior-inferior neck; where it increased slightly.
INTERPRETATION: The study concluded that a thicker cement mantle increases strain shielding within the superior resurfaced femoral head; although short to medium term clinical trials do not suggest these factors to be of much concern. The analysis also found strain to increase around the inferior head-neck junction with a thinner mantle. Cementing the guide pin resulted in increased strain shielding whilst simultaneously shifting peak loads distally along the femoral neck. This work found that modelling a group of femurs was a useful tool for better interpreting the loading in the resurfaced femur.