In vivo wear of polyethylene glenoid components in total shoulder arthroplasty

Abstract

AbstractLoosening of the glenoid component after a total shoulder arthroplasty, leading to pain and the need for a revision operation, accounts for one third of all shoulder replacement complications. It has been shown that glenoid loosening could be a result of osteolysis of periprosthetic bone induced by polymeric wear debris. The aim of this study was to determine the amount and pattern of in vivo wear of polyethylene glenoid components by examining a set of so-called retrievals. Six glenoid components were retrieved and examined (5 all-polyethylene and 1 metal-backed). The average time of functioning of these components in human bodies was 10 years with the shortest time of 7 and longest 14 years. Four components were scanned using a laser scanner. The results of measurements have been used to generate geometrical models of the retrievals using CAD software. These models have been subsequently used to determine the maximum depth and volumetric wear rate for each component. All six retrievals were examined using scanning electron microscopy (SEM). The maximum volumetric wear rate and wear depth for the analyzed retrievals was 30 mm3/year and 0.2 mm/year, respectively. From SEM analysis of the retrievals it was found that at macroscopic level the worn surfaces consist of (a) polished and (b) scratched regions. Intensive wear areas and fine multidirectional scratches were dominant in all retrievals. Random scratches were also observed, most probably due to third body wear (cement particles). In two implants pitting areas and surface micro-cracks have been observed, which most likely result from subsurface fatigue.