Trunnion Corrosion and Early Failure in Monolithic Metal-on-Polyethylene TMZF Femoral Components: A Case Series

We describe four patients who were treated with primary total hip arthroplasty (THA) at two tertiary academic Australian teaching hospitals that experienced premature failure of head-neck trunnions through dissociation of the head-neck taper junction. This retrospective case series have similar clinical presentations and macroscopic pathology with severe head-neck taper junction loss of material, corrosion and early catastrophic failure. It is proposed that the accelerated wear is related to use of varus offset neck in a proprietary beta titanium alloy (Ti-12Mo-6Zr-2Fe  or TMZF O Stryker Osteonics, Mahwah NJ, USA) TMZF femoral stem, longer head-neck combination in a relatively active, older, male patient population. In this limited case series presentation was on average 80 months (range 53-92) following index procedure. In three of the four patients, a prodromal period of groin or buttock pain was reported for between 1 week and 2 months prior to acute presentation. Significant metallosis and local tissue damage including gluteal muscle insufficiency was evident. Each stem revised was well fixed. An extended trochanteric osteotomy was required in two of the four cases for stem extraction. We recommend caution and further evaluation on the relationship between TMZF metal alloy and its longevity in higher demand patients with high neck offset, varus stem geometry and large CoCr bearing heads.