Review Question - QID 949

All of those statements regarding conventional polyethylene liners are true EXCEPT they generate larger (not smaller) wear particles than the highly cross-linked liners. It is the highly cross-linked liners that have been found to generate smaller wear particles.

Highly crossed-linked polyethylene in hip arthroplasty has been shown in multiple studies to be more wear resistant compared to conventional polyethylene, particularly in regards to adhesive wear. The highly cross-linked poly generates wear particles of a smaller size. In a randomized clinical study with 6.8 years follow-up, McCalden et al found that THA with highly cross-linked poly had a significantly lower femoral head penetration rate (0.003 mm/yr vs 0.051 mm/yr, p=0.025), which indicates less linear wear in the highly cross-linked poly. The disadvantage of highly cross-linked poly is that the cross-linking reduces its mechanical properties (e.g. decreased toughness, ductility, tensile strength, and fatigue strength) The Bradford reference looked at ex-planted liners and saw consistent evidence of early surface deformation and cracking; All explants exhibited some form of surface change, including surface cracking, abrasion, pitting, or scratching. The Jacobs paper makes the point that the cross-linked polys do seem to exhibit lower wear rates without significant osteolysis problems.