Among Large-Diameter MoM Hip Implants, Durom Has Highest Metal Ion Level
In a May 2011 supplement to The Journal of Bone & Joint Surgery, Lavigne et al. reported results from a prospective two-year study looking at blood metal-ion levels in patients who received one of four types of large-head, metal-on-metal THA designs. At that point, the Durom design from Zimmer showed significantly higher blood levels of cobalt and titanium ions than the three other implants (Birmingham from Smith & Nephew, ASR XL from DePuy, and Magnum from Biomet).
The February 17, 2016 JBJS provides an update on the same cohort at five years of follow-up. By five years, the original 144-patient cohort had diminished to 134, 123 of whom were available for clinical follow-up and 93 of whom had their metal-ion levels analyzed again.
In terms of WOMAC and UCLA function scores, there were no differences at five years among the implant types. However, the current study revealed that the Durom design produced the highest levels of metal ions in the blood and the highest number of adverse local tissue reactions and revisions. One of the most problematic design factors in all four implants, the authors say, is the junction of the femoral trunnion and head taper or adapter sleeve (see related OrthoBuzz post).
While noting that ion levels in isolation are probably not useful as either diagnostic or screening criteria, the authors say that “ion progression over time may be more useful, and ideally, a multimodal investigative protocol correlating patient symptomatology, ion levels, and cross-sectional imaging would be required.”