The performance of mixed manufacturer metal on metal total hip replacements

Using a femoral head from one manufacturer on the stem of another manufacturer poses the risk that the taper interface between the components may not contact correctly and the performance of the joint will be impaired. The cohorts in this study are a combination of modular Birmingham Hip Resurfacing (BHR) and Adept femoral heads on CPT stems. The study reviews the geometry of the taper interfaces to establish if the taper clearance angles was outside of the normal range for other taper interfaces. In addition the rates of material loss from the bearings and taper and a ranking of the stem damage were reviewed to determine if the levels of loss were above that seen for other similar joints. The material loss analysis demonstrated that the rates or levels of loss from the bearings, taper and stem were no different to levels published for manufacturer matched joints and in many cases were lower. The results demonstrate that the taper clearance angles for the mixed manufacturer joints (BHR-CPT: 0.067 to -0.116, Adept-CPT: 0.101 to -0.056) were within the range of other studies and manufacturer matched clearances (0.134 to -0.149).Using components from different manufacturers has not in this instance increased the level of material loss from the joints, when compared to other similar manufacturer matched joints.