Material Loss at the Taper Junction of Retrieved Large Head Metal-on-Metal Total Hip Replacements

It has been speculated that material loss, either as corrosion or wear, at the head–stem taper junction is implicated in the
high revision rates reported for metal-on-metal total hip replacements. We measured the volume of material loss from the taper and
bearing surfaces of retrieved devices, and investigated the associations with blood metal ion levels and the diagnosis of a cystic or solid
pseudotumor. The median volumes of material lost from the female and male taper surfaces were 2.0 and 0.29 mm3, respectively, while
the median volumes of wear from the cup and head bearing surfaces were 1.94 and 3.44 mm3, respectively. Material loss from the female
taper was similar to that from the acetabular bearing surface (p ¼ 0.55), but significantly less than that from the femoral bearing surface
(p < 0.001). Material loss from the male taper was less than that from both bearing surfaces (p < 0.001). Multivariable analysis
demonstrated no significant correlations between the volume of material lost from the taper surfaces and either blood cobalt or chromium
ions, or the presence of pseudotumor. While a substantial volume of material is lost at the taper junction, the clinical significance of this
debris remains unclear.