Tibial tray debonding from the cement mantle is associated with deformation of the backside of polyethylene tibial inserts

Abstract

Aims The aim of this study was to investigate whether wear and backside deformation of polyethylene (PE) tibial inserts may influence the cement cover of tibial trays of explanted total knee arthroplasties (TKAs). Methods At our retrieval centre, we measured changes in the wear and deformation of PE inserts using coordinate measuring machines and light microscopy. The amount of cement cover on the backside of tibial trays was quantified as a percentage of the total surface. The study involved data from the explanted fixed-bearing components of four widely used contemporary designs of TKA (Attune, NexGen, Press Fit Condylar (PFC), and Triathlon), revised for any indication, and we compared them with components that used previous generations of PE. Regression modelling was used to identify variables related to the amount of cement cover on the retrieved trays. Results A total of 114 explanted fixed-bearing TKAs were examined. This included 76 used with contemporary PE inserts which were compared with 15 used with older generation PEs. The Attune and NexGen (central locking) trays were found to have significantly less cement cover than Triathlon and PFC trays (peripheral locking group) (p = 0.001). The median planicity values of the PE inserts used with central locking trays were significantly greater than of those with peripheral locking inserts (205 vs 85 microns; p < 0.001). Attune and NexGen inserts had a characteristic pattern of backside deformation, with the outer edges of the PE deviating inferiorly, leaving the PE margins as the primary areas of articulation. Conclusion Explanted TKAs with central locking mechanisms were significantly more likely to debond from the cement mantle. The PE inserts of these designs showed characteristic patterns of deformation, which appeared to relate to the manufacturing process and may be exacerbated in vivo. This pattern of deformation was associated with PE wear occurring at the outer edges of the articulation, potentially increasing the frictional torque generated at this interface.

High rate of radiolucent lines following the cemented original design of the ATTUNE total knee arthroplasty

“…7 However, a comparative retrieval analysis showed that designs of TKA with a central locking tray had significantly less cement cover compared with those with a peripheral locking tray; the Pe inserts in the central locking systems had a characteristic pattern of deformation of the outer edges, which could increase the localized frictional torque and lead to debonding of the tray from the cement mantle. 51 it may also be that the different design and instrumentation of the ATTUNE system leads to an inadequate cement mantle compared with its predecessors. A recent report showed that excessive press fit may lead to incomplete seating or tilting of the tibial component, especially in hard and uneven sclerotic bone.…”

High rate of tibial debonding and failure in a popular knee replacement

“…A recent paper by Bhalekar et al 26 examined explanted NexGen components and identified a pattern of deformation in the polyethylene insert which they thought was likely a manufacturing issue which was exacerbated in vivo. They believe that the problem was related to the polyethylene component and the central locking mechanism used to sit it into the tray, not the tibial tray itself.…”