The Femoral Cement Mantle in JRI Furlong Total Hip Replacements

The creation of an adequate femoral cement mantle in cemented total hip replacement (THR) can reduce the incidence of cement fracture, focal osteolysis and subsequent aseptic loosening. Excavating a suitably sized cavity within the femoral canal with an appropriate broach is an essential step in this process.

We measured the size and volume of the femoral broaches and stems supplied with the JRI Furlong THR system. Least Significant Difference Multiple Comparison revealed that the volume of all 4 broaches was significantly less than the equivalent stems (p<0.001). Using an in vitro method, we created cement mantles that could be directly measured. We found the cement mantles created by these broaches were of inadequate thickness, with numerous cement defects (mean thickness = 0.89 mm, cement defects at 23% of measurement sites).

JRI have developed a new set of broaches to be used with the original femoral stems. Assessment of these broaches showed that all four sizes were significantly larger (CI 14.20 – 26.96) than the original design (CI 10.45 – 13.21, p = 0.011). Volumetric analysis confirmed this significant difference (p<0.001). The cement mantles created by these broaches were significantly thicker and more uniform, with fewer cement defects (mean thickness = 1.99 mm, p<0.05, cement defects at 3% of sites).

We conclude that, in vivo, the original broaches would fail to excavate an appropriate cavity and may not prevent direct bone-stem contact. The newer broaches are significantly larger, and may have an unpredictable effect on subsequent stem longevity when used in vivo.