A preclinical numerical assessment of a polyetheretherketone femoral component in total knee arthroplasty during gait

Contains fulltext : 170568.pdf (publisher's version ) (Open Access)BACKGROUND: Conventional total knee replacement designs show high success rates but in the long term, the stiff metal components may affect bone quality of the distal femur. In this study we introduce an all-polymer total knee replacement device containing a PEEK femoral component on an UHMWPE tibial implant and study its mechanical integrity, fixation, and stress shielding of the periprosthetic femur. METHODS: The implant was analysed in finite element simulations of level gait, adopted from the ISO 14243-1 standard. Mechanical integrity of the implant and underlying cement mantle were tested, and the fixation strength of the cement-implant interface was studied. Stress shielding was assessed based on strain energy density distributions in the distal femur. We compared PEEK and CoCr implants for mechanical performance and fixation, and compared both versions against an intact case to determine the change in bone strain energy density. RESULTS: The mechanical integrity of the PEEK and CoCr components was similar in magnitude, but differences in stress patterns were found. Moreover, the cement mantle was loaded more heavily in the CoCr configuration. Under similar interface properties, the CoCr-cement interface was more at risk of failure than the PEEK-cement interface. The bone strain energy density distribution of the PEEK implant was similar to the intact case, while the CoCr implant showed signs of stress shielding, and a different distribution than the intact and PEEK models. CONCLUSIONS: During gait, the PEEK femoral component performed similarly to CoCr, with no added risk for the cement mantle. The reduction in stress shielding for PEEK was evident and confirms the potential reduction in long-term loss of bone stock for this all-polymer knee implant

The mechanical response of a polyetheretherketone femoral knee implant under a deep squatting loading condition

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Too hot to hunt: Mechanistic predictions of thermal refuge from cat predation risk

First published: 29 June 2022Many threatened species depend on climatic microrefugia, but places with harsh climates for predators may also play a refugial role. Feral cats threaten many native species in arid Australia. Although cats can persist in regions with no free water, their abundance should depend on the availability of microclimates that protect them from harsh environmental conditions. We developed a bio-physical model of feral cat heat stress and used it to explore how behavior and microhabitat features influence water requirements and activity. Tests of model predictions against fine-scale GPS and microclimate data highlight the importance of refuges, particularly rabbit burrows. Continent-wide simulations show large but temporally varying areas of the arid zone that would be lethal for cats without access to deep or shaded burrows. Our approach can identify locations that may act as natural refuges for native prey, and where habitat management strategies may be effective in controlling cat abundance.Natalie J. Briscoe, Hugh McGregor, David Roshier, Andrew Carter, Brendan A. Wintle, Michael R. Kearne

A typology of international human resource management strategies and processes

This paper develops a framework of international human resource management (IHRM) that moves beyond strategy and structure to focus on processes. The results of six case studies of large German multinational corporations in three countries show different configurations of IHRM strategies and policies. International knowledge flows and coordination varied in intensity, content, direction and mechanisms used. With 'cognofederate' IHRM one type was identified that has been hitherto neglected

Velocity dependence of atomic friction: Rate theory and beyond

Evstigneev M, Reimann P. Velocity dependence of atomic friction: Rate theory and beyond. In: Gnecco E, Meyer E, eds. Fundamentals of Friction and Wear. NanoScience and Technology. Berlin: Springer; 2007: 117-142