Wear of Femoral Head Taper Connections of Contemporary Total Hip Prostheses : An Experimental Study

Purpose: Progress in the design of total hip prostheses has enhanced the long-term results of total hip arthroplasty. However, recent clinical failures have raised concerns regarding the long-term performance of taper connections. Issues at the taper connection of the femoral head can lead to implant failure and revision surgery. There is scarcity of published studies on the wear performance of contemporary femoral head taper connections in carefully controlled laboratory tests. This work aims to help remedy this shortcoming. Methods: The study comprised dynamic load frame tests and multidirectional hip joint simulator tests for two contemporary prosthesis designs with titanium alloy femoral stems and CoCr and zirconia toughened alumina (ZTA) femoral heads of 36 mm diameter and medium neck length against vitamin E stabilized, highly cross-linked polyethylene liners (n = 3). Worn surfaces were analyzed by optical and scanning electron microscopy (SEM). Results: Wear was more prominent in the inferior and distal parts of the CoCr head tapers, and these regions aligned with those of the trunnions that showed most wear. Wear marks on CoCr heads were relatively mild, indicative of fretting due to micromotion. Material displacement occurred locally without dislodged debris. ZTA heads mainly showed titanium transfer by adhesive wear. ZTA femoral heads outperformed CoCr heads regarding wear resistance and surface stability. The 12/14 tapers showed more pronounced wear and surface modifications compared with Type 1 tapers. EDX analysis confirmed the absence of adhesion between CoCr and Ti alloy, and increased oxygen percentage on worn regions. Conclusion: The wear marks were mild. No serious damage was observed. The wear behavior of the taper connections appeared satisfactory, and not a cause for concern in the short term.