Non-union in an unnoticed neck fracture in resurfacing total hip arthroplasty.

The renewed popularity of resurfacing hip arthroplasty (RHA) in the last five years has generated a remarkable quantity of scientific contributions based on mid- and short-term follow-up. In spite of some large series with extremely low complication rates, more than one paper has reported a consistent early revision rate as a consequence of biological or biomechanical failure. Two major complications are commonly described with resurfacing implants: avascular necrosis and neck fracture. A close relationship between these two events has been suggested, but not firmly demonstrated, while surgical exposure and implant positioning seem to be better understood as potential causes of failure. However, it may happen that neither avascular necrosis nor neck fracture can be clearly recognised in a failed resurfacing implant: it is what we have directly experienced, with a missed fracture at the head-neck junction, evolved in non-union, beneath the dome of the femoral component. The present report, besides a brief clinical history, tries to give a possible interpretation of such an unusual complication.

Femoral prosthetic heads and their significance in polyethylene wear.

We used scanning electron microscopy to perform an ultrastructural analysis and two optical interferometric profilers to measure roughness on 40 prosthetic femoral heads. We expressed roughness as Ra (roughness average) value and Rsk (roughness skewness) value. Our results show that in order to obtain an ideal surface finish a low or not very high Ra value and a negative Rsk value are needed. The presence of depressions or holes (rather than scratches) with smooth (rather than sharp) edges seems to improve the lubrication and wettability properties.