Large Head Articulations: Benefits and Drawbacks

Abstract

Dislocation, impingement and a limited range of motion of total hip arthroplasty prostheses have been shown to be the major drawbacks of small bearings of 28 mm in head diameter. Since the introduction of new highly cross-linked polyethylenes (XPEs) that show a higher wear resistance than conventional polyethylenes (PEs), larger femoral heads have become more popular. But several issues are still a matter of debate, particularly the long-term volumetric wear under clinical conditions, stability, mechanical integrity and last but not least, the long-term outcome and correct patient selection. In vitro tests have shown that with new XPEs, the wear rate can be further reduced, but this has not been tested long enough under clinical conditions to have sufficient information regarding their long-term outcome. Clinical studies of large-diameter bearings with conventional XPEs yield results that do not confirm the expectations of long-term low volumetric wear, and more evidence is becoming available. There are also serious issues by the use of large-diameter metal heads used in combination with thin XPE liners at the modular head-neck tapers as a result of a higher frictional torque. On the contrary, large-diameter ceramic-on-ceramic bearings seem to be insensitive to wear and friction.