Late Failure of a Polyethylene Unicompartmental Knee Insert -Retrieval Analysis Protocol and Results

This study reports the investigation of a degraded polyethylene insert retrieved after the catastrophic failure of a mobile bearing knee implant, occurred after a traumatic event and leading to a late revision. Understanding wear mechanisms of polyethylene components is important to improve the implants for joint replacement. This model of unicompartmental arthroplasty, due to its mobile, congruent insert and design, has the potential to attain low rates of wear, leading to an improved survival of the prosthesis over fixed-bearing knee implants. During the surgical technique, however, it is critical to avoid any source of impingement or incongruent articulation, as this are associated with increased rates of polyethylene wear and may contribute to the early necessity for revision surgery. The investigated insert presented a macroscopic fragmentation, surface and bulk defects and debris. Characterization of the retrieved polyethylene implant fragments was performed by macroscopic examination, by scanning electron microscopy and Fourier transform infrared spectroscopy. Due to a systematic retrieval analysis according to current standards, we can question that, in our case, third body wear is rarely pure bone or pure cement debris related but a combination of the two mentioned. The combination enhanced contribution of polyethylene debris in severe wear initiation and progression. Complete examination of the explants exhibiting breakage or severe wear may help in understanding pathogenic ways of failure in unicompartmental knee.

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Polyethylene Bearing Wear in the Oxford Unicompartmental Knee

Proceedings of IMPRS ◽

10.18060/23469 ◽

2019 ◽

Vol 2 (1) ◽

Author(s):

Priyanka Ghosh ◽

Hasan Mohammad ◽

Stephen Mellon ◽

David Murray

Keyword(s):

Wear Rate ◽

Polyethylene Wear ◽

Oxford Knee Score ◽

Knee Kinematics ◽

Mobile Bearing ◽

Unicompartmental Knee Replacement ◽

Late Time ◽

Unicompartmental Knee ◽

Implant Size ◽

Over Time

Background and Hypothesis: The Oxford Knee is a unicompartmental knee replacement (UKR) for patients with end-stage knee osteoarthritis (OA). It contains a polyethylene (PE) mobile bearing between the femoral and tibial components that helps maintain normal knee kinematics. Unfortunately bearing wear is one of the leading causes of UKR failure. In this study, we sought to investigate PE wear rate over time and the initial deformation (creep) in early months. Project Methods: This study used radiostereometric analysis (RSA) to precisely track polyethylene bearing thickness over time in 40 medial Oxford UKR patients. The patients underwent stereo radiographs at 1 week post-op (reference), 3 months, 6 months, 1 year, 2 years, and 5 years. Model-based RSA software was used to determine the exact position of the femoral and tibial components, and Matlab was used to calculate the minimum linear distance between these two components, taken as bearing thickness. Results: The average wear rate was 0.32mm/yr (SD 0.42) in the first 3 months, 0.16mm/yr (SD 0.55) from 3 to 6 months, and 0.07mm/yr (SD 0.03) between 1 and 5 years. No correlation was found between wear rate and BMI, fixation, implant size, or 5 year Oxford Knee Score. Conclusion and Potential Impact: This was the first study to investigate detailed early and late time points of polyethylene wear in the Oxford UKR. Mean bearing wear was higher in the first 6 months, presumably due to creep, and significantly reduced from 1 year onwards, presumably while true wear took place.

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Polyethylene wear of mobile-bearing unicompartmental knee replacement at 20 years

Journal of Bone and Joint Surgery - British Volume ◽

10.1302/0301-620x.93b4.25605 ◽

2011 ◽

Vol 93-B (4) ◽

pp. 470-475 ◽

Cited By ~ 40

Author(s):

B. J. L. Kendrick ◽

D. J. Simpson ◽

B. L. Kaptein ◽

E. R. Valstar ◽

H. S. Gill ◽

...

Keyword(s):

Knee Replacement ◽

Polyethylene Wear ◽

Mobile Bearing ◽

Unicompartmental Knee Replacement ◽

Unicompartmental Knee

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Computational wear prediction of insert conformity and material on mobile-bearing unicompartmental knee arthroplasty

Bone and Joint Research ◽

10.1302/2046-3758.811.bjr-2019-0036.r1 ◽

2019 ◽

Vol 8 (11) ◽

pp. 563-569 ◽

Cited By ~ 3

Author(s):

Yong-Gon Koh ◽

Jin-Ah Lee ◽

Hwa-Yong Lee ◽

Hyo-Jeong Kim ◽

Kyoung-Tak Kang

Keyword(s):

Wear Rate ◽

Contact Pressure ◽

Knee Arthroplasty ◽

Contact Area ◽

Unicompartmental Knee Arthroplasty ◽

Polyethylene Wear ◽

Mobile Bearing ◽

Volumetric Wear ◽

Wear Performance ◽

Unicompartmental Knee

Objectives Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty with isolated medial or lateral compartment osteoarthritis. However, polyethylene wear can significantly reduce the lifespan of UKA. Different bearing designs and materials for UKA have been developed to change the rate of polyethylene wear. Therefore, the objective of this study is to investigate the effect of insert conformity and material on the predicted wear in mobile-bearing UKA using a previously developed computational wear method. Methods Two different designs were tested with the same femoral component under identical kinematic input: anatomy mimetic design (AMD) and conforming design inserts with different conformity levels. The insert materials were standard or crosslinked ultra-high-molecular-weight polyethylene (UHMWPE). We evaluated the contact pressure, contact area, wear rate, wear depth, and volumetric wear under gait cycle loading conditions. Results Conforming design inserts had the lower contact pressure and larger contact area. However, they also had the higher wear rate and volumetric wear. The improved wear performance was found with AMD inserts. In addition, the computationally predicted volumetric wear of crosslinked UHMWPE inserts was less than half that of standard UHMWPE inserts. Conclusion Our results showed that increasing conformity may not be the sole predictor of wear performance; highly crosslinked mobile-bearing polyethylene inserts can also provide improvement in wear performance. These results provide improvements in design and materials to reduce wear in mobile-bearing UKA. Cite this article: Bone Joint Res 2019;8:563–569.

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Fixed- versus mobile-bearing unicompartmental knee arthroplasty: a meta-analysis

Scientific Reports ◽

10.1038/s41598-020-76124-z ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Wenchao Zhang ◽

Jianpeng Wang ◽

Hui Li ◽

Wanchun Wang ◽

Daniel M. George ◽

...

Keyword(s):

Knee Arthroplasty ◽

Unicompartmental Knee Arthroplasty ◽

Polyethylene Wear ◽

Meta Analysis ◽

Mobile Bearing ◽

Cochrane Library ◽

Unicompartmental Knee ◽

Significant Difference ◽

Library Studies ◽

The Cochrane Library

Abstract Unicompartmental knee arthroplasty (UKA) can be either a fixed bearing (FB) or a mobile bearing (MB) construct with controversy as to which design is superior. This question is addressed with a systematic review and meta-analysis. A literature search was performed using PubMed, Embase and the Cochrane Library. Studies were reviewed according to the inclusion and exclusion criteria developed in advance. We compared the differences in clinical and radiological outcomes between the FB and MB UKAs. Analyses were performed with the Review Manager and STATA software. A total of 17 studies involving 2612 knees were included. No significant differences were presented between the FB and MB prostheses in clinical and radiological outcomes. However, it was evident that there were differences in the modes and timing of the failures, bearing dislocation led to earlier failures in the MB prosthesis, while the FB prosthesis failed later due to polyethylene wear. There was no evidence of publication bias using the incidence of revisions. There is no significant difference between the FB and MB UKAs; however, there are differences in the modes and timing of failures.

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