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. 2025 Feb 1;107-B(2):239-245.
doi: 10.1302/0301-620X.107B2.BJJ-2024-0623.

Evaluating polyethylene, polyether-ether-ketone, and metal-on-metal locking mechanism survival in Modular Universal Tumour and Revision System knee reconstructions for oncological indications : insights from the MUTARS Orthopedic Registry Europe

Richard E Evenhuis  1 , Michaël P A Bus  1 , Joao van Nes  1 , Sebastian G Walter  2 , Jorge Cabrolier  3 , Marta Fiocco  4   5   6 , Robert J P van der Wal  1 , Demien Broekhuis  1 , Simen Sellevold  7 , Michiel A J van de Sande  1   4
Affiliations

Evaluating polyethylene, polyether-ether-ketone, and metal-on-metal locking mechanism survival in Modular Universal Tumour and Revision System knee reconstructions for oncological indications : insights from the MUTARS Orthopedic Registry Europe

Richard E Evenhuis et al. Bone Joint J. .

Abstract

Aims: Over time, the locking mechanism of Modular Universal Tumour and Revision System (MUTARS) knee arthroplasties changed from polyethylene (PE) to polyether-ether-ketone Optima (PEEK) and metal-on-metal (MoM) in an attempt to reduce the risk of mechanical failure. In this study, we aimed to assess the cumulative incidence of locking mechanism revision for symptomatic instability by type of material, and assess potential associated risk factors.

Methods: The MUTARS Orthopaedic Registry Europe was used for a retrospective review of 316 patients (54% male (n = 170), median age 44 years (IQR 23 to 61)) who underwent a MUTARS knee arthroplasty for oncological indications between December 1995 and January 2023. The minimum follow-up was 12 months, and the median follow-up was 7.9 years (IQR 3.3 to 13.0). A competing risk model was used to estimate the cumulative incidence of first locking mechanism revision with death and revision for any other reason as competing events. Possible risk factors were assessed employing a univariate cause-specific hazards regression model.

Results: Symptomatic instability of the hinge or locking mechanism due to wear (n = 20) or breakage (n = 14) occurred in 34 patients (11%): 9% of PE (n = 4/45), 20% of PEEK (n = 9/44), and 9% of MoM locking mechanisms (n = 21/227). The cumulative incidences of revision for instability due to wear or locking mechanism breakage at two, five, and ten years were 0%, 5% (95% CI 1 to 15), and 5% (95% CI 1 to 15) for PE, 5% (95% CI 1 to 14), 14% (95% CI 5 to 26), and 16% (95% CI 7 to 29) for PEEK, and 0%, 3% (95% CI 1 to 6), and 10% (95% CI 5 to 16) for MoM. With PE as the reference category, the cause-specific hazard ratio for PEEK and MoM were 3.6 (95% CI 1.1 to 11.9; p = 0.036) and 3.2 (95% CI 1.1 to 9.5; p = 0.043), respectively. Age, BMI, resection length, and extra-articular resections were not associated with the time to locking mechanism revision.

Conclusion: Alterations in prosthetic materials have not decreased the revision risk for locking mechanism failure. Besides locking mechanism material, no other patient- or prosthesis-related risk factors for locking mechanism failure were identified. Improvement of the locking mechanism is warranted since revision exposes patients to the risk of serious secondary complications.

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Conflict of interest statement

R. E. Evenhuis, M. P. A. Bus, J. van Nes, R. J. P. van der Wal, D. Broekhuis, and M. A. J. van de Sande report an unconditional research grant, paid to their institution, from Implantcast, related to this study. The funder (and also producer of the MUTARS knee reconstructions) was not involved with the design, conduction, or analysis of the study results. M. van de Sande also reports grants from Carbofix and advisory board expenses from Synox, AnMax,and Dicephera, all of which are unrelated to this study. S. Sellevold reports support for attending meetings and/or travel for a MUTARS meeting, unrelated to this study.

References

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