Material loss at the taper junction of retrieved large head metal‐on‐metal total hip replacements

Abstract

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 mm 3 , respectively, while the median volumes of wear from the cup and head bearing surfaces were 1.94 and 3.44 mm 3 , 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. ß

What is the Trouble With Trunnions?

“…Substantial volumetric material loss can take place at the taper junctions of modern large-diameter THAs, and in some cases, the material loss is more than bearing wear [32,34]. There are both solid and soluble products of corrosion that are variable in size [28].…”

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

“…Specifically, the MoM material combinations have recently fallen in popularity of use due to a relatively large number of early failures associated with adverse reactions to metal debris (Anissian et al, 1999;Brock et al, 2015). This unacceptably high failure rate is mainly associated with wear that occurs at the articulating (Brock et al, 2015;Joyce et al, 2009;Lord et al, 2011) and non-articulating (Langton et al, 2012;Matthies et al, 2013) surfaces of these medical implants.…”

Trunnionosis: A pain in the neck

“…In a bid to quantify wear, corrosion and to determine the main mechanism of material loss at the taper, a retrospective study of 78 large metal-on-metal hip replacements retrieved after revision was conducted by Matthies et al [14] . Corrosion was assessed using light microscopy and scanning electron microscopy (SEM).…”

“…Several of the studies mentioned in this paper have also speculated that the material released at the taper may be more biologically active than that derived from the weight bearing surfaces [14,21] .…”