Reinforcement of bone cement around prostheses by pre-coated wire coil: a finite element model study

The longevity of cemented total joint replacements, namely total hip arthroplasty (THA), depends on the integrity of the cement per se and interfaces of the metallic stem-cement and bone-cement, and stress/stress transmission and its distribution. A simple coil made of stainless steel wire was placed around a tapered stem in a simulated cement mantle to counteract the radial- and hoop-stresses created by the stem loading. Two-dimensional axisymmetric finite element analysis was performed to elucidate the level of the stress and its distribution with and without the wire coil. The results suggest that the peak stresses distributed throughout the cement may be reduced by more than one half, via the incorporation of a wire coil, confirming the mechanical test results, which showed an average fracture load of 3.70 +/- 1.13 kN for pure bone cement control and 9.02 +/- 1.54 kN for the wire coil reinforced specimens. These results indicate that the reinforcement of the cement mantle with a wire coil in the distal end of the hip stem prosthesis could reduce the hoop-stresses, which may results in reduced stresses in the bone and cement interface. Consequently, loosening of the interfaces of the bone-cement and cement-stem could be reduced due to the enhanced fatigue life of the bone cement mantle with favorable stress distribution at the distal tip of the stem.