Wear performance of metal and ceramic long-neck femoral head taper connections: an experimental ex vivo study.

BACKGROUND AND PURPOSE: The wear performance of femoral head taper connections is important for the longevity of total hip replacement. Metal release may cause adverse tissue reactions. There are some clinical indications that long neck heads may show increased wear, but no laboratory tests have been published. We aimed to examine the wear performance of femoral head taper connections in long and extra-long neck heads. METHODS: Load frame and hip joint simulator wear tests were performed with the same stem designs as in the reference study. The CoCr and zirconia toughened alumina (ZTA) heads of 36 mm diameter were of the long or extra-long neck type. Optical and scanning electron microscopy were utilized to study wear marks, and mass spectrometry to estimate Ti and Co release. Head disassembly forces were measured. RESULTS: Our preclinical, design-specific results showed that, compared with medium necks, long and especially extra-long necks led to increased wear while maintaining an asymmetric wear pattern more widely distributed throughout the contact area. In the hip joint simulator tests, 1 neck fracture occurred. CONCLUSION: The long and extra-long head taper connections showed increased wear compared with that of medium heads. Although no serious damage occurred, CoCr head tapers were the most affected compared with ZTA.