Catastrophic failure of a low profile metal-backed glenoid component after total shoulder arthroplasty.

Context: The longevity of the glenoid component in total shoulder arthroplasty (TSA) continues to be problematic. All polyethylene glenoid components have been most widely used, but loosening rates with time and the need for revision has resulted in high-profile metal-backed components with the potential for a more stable prosthesis bone interface and liner exchange. High revision rates in the high profile metal backed designs led us to evaluate a low profile metal backed component. Aims: To examine the rate and mode of failure of a TSA in a single surgeon consecutive series that has been identified by the Australian National Joint Replacement Registry to have a higher than anticipated rate of revision. Materials and Methods: This is a single surgeon retrospective consecutive series of 51 arthroplasties undertaken in 50 patients (18 males and 32 females) with an average age of 70.4 ears (range 51-90) and mean follow-up of 5.5 years (range 3.7-8.1). Results: We observed a very high (29%) rate of revision of the metal-backed glenoid components in this series. The primary mode of failure was glenoid baseplate nonintegration which with a well-fixed central cage screw led to bone resorption and implant breakage or disassembly. Conclusion: Analysis of the mode of failure of implants identified by robust registries is essential for the development of new prostheses and the pursuit of prosthesis longevity. This low profile metal backed prosthesis has been withdrawn, but without a published mechanism of failure. We feel that any prosthesis withdrawal should be accompanied by appropriate published mechanisms to prevent future component design errors based on similar design problems.