Abstract
INTRODUCTION
Retrieval analysis is an important aspect of medical device development. Examination of retrieved devices allows device developers to close the design loop, understand the performance of devices, and validate assumptions made and methods used during preclinical testing. We provide an overview of the implant retrieval analysis performed at the Implant Research Center at Drexel University on reverse total shoulder systems retrieved after short to medium term implantation.
METHODS
We have examined 18 reverse total shoulders, retrieved at revision surgery after short to mid-term implantation (average 1.4 years, maximum 3.3 years). The average age at revision was 71 years old (st dev 11 years). Our evaluations included analysis of glenosphere bearing surface damage, evaluation of tribocorrosion at the modular junctions, visual assessment of polyethylene humeral bearing surface damage, quantitative analysis of polyethylene wear.
RESULTS and DISCUSSION
We observed that polyethylene wear of the humeral bearing surface (mode I) is limited in the short to medium term and that wear and damage of revised devices are dominated by unintentional contact and impingement of the inferior rim of the bushing (mode II damage). This was in agreement with a previously published analysis of a smaller cohort (Figure 1). Scratching and damage of the glenosphere was a common observation, particularly in patients with a history of instability. The observed increase in glenosphere roughness was similar to that reported in association with hip dislocation (Figure 2). Damage at the modular junctions was limited and dominated by fretting rather than corrosive damage. Mild to moderate fretting was commonly observed at the interface between the glenosphere and metaglene (Figure 3). These observations provide an increased understanding of device performance and potential failure modes. Further studies will be necessary to characterize the long term performance of reverse total shoulder systems.
