Abstract
Highly cross-linked polyethylene has become the gold standard in total hip replacement for its wear resistance. Moderately crosslinked polyethylene is now available for total knee replacement (TKR), although concerns about reduced mechanical strength have prevented widespread adoption. The purpose of this report is to describe an unusual case where a patient underwent cruciate retaining TKR using a moderately crosslinked polyethylene tibial insert that went on to fracture twice in the same location across the primary and first revision surgery. The first tibial insert was 10 mm thick and was implanted for 16 months. The second tibial insert was 15 mm thick and was implanted for 11 months. Both fractured along the posterior aspect of the medial articular surface. The lack of a specific event leading to these fractures and the fact that they occurred twice in the same location in the same patient suggest that caution is still necessary regarding the introduction of crosslinked polyethylene for TKR surgery.
Highlights
Cross-linked polyethylene was introduced for THR in the last decade and has since demonstrated excellent longterm wear resistance, leading to its acceptance as the new clinical standard for THR implants [1]
Adoption of cross linking for total knee replacement (TKR) has been more controversial, as the cross linking process can decrease the mechanical properties of the polyethylene in addition to increasing its wear resistance [2]
TKR implants made with moderate cross linking of the polyethylene have shown decreased wear and similar mechanical strength compared to implants using conventional polyethylene, and on this basis moderately cross-linked polyethylene inserts have been introduced for clinical use [3,4,5]
Summary
Cross-linked polyethylene was introduced for THR in the last decade and has since demonstrated excellent longterm wear resistance, leading to its acceptance as the new clinical standard for THR implants [1]. Adoption of cross linking for TKR has been more controversial, as the cross linking process can decrease the mechanical properties of the polyethylene in addition to increasing its wear resistance [2]. TKR implants made with moderate cross linking of the polyethylene have shown decreased wear and similar mechanical strength compared to implants using conventional polyethylene, and on this basis moderately cross-linked polyethylene inserts have been introduced for clinical use [3,4,5]. The purpose of this report is to describe an unusual case in which a patient had a fracture of the moderately cross-linked polyethylene tibial insert of their total knee replacement, at the same posteromedial articular surface location, across two different surgeries in the same joint, within a short period of implantation
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