The human knee implant is computationally modelled in the mixed lubrication regime to investigate the tribological performance of the implant. This model includes the complex geometry of the implant components, unlike elliptical contact models that approximate this geometry. Film thickness and pressure results are presented for an ISO gait cycle to determine the lubrication regime present within the implant during its operation. It was found that it was possible for the lubrication regime to span between elastohydrodynamic, mixed and boundary lubrication depending on the operating conditions of the implant. It was observed that the tribological conditions present in one condyle were not necessarily representative of the other. Multiple points of contact were found within the same condyle, which cannot be computed by the elliptical contact solvers. This model can be used to balance forces in all directions, instead of only the normal loads, as often done in elliptical contact models. This work is an initial step towards understanding the role of the complex geometry in the tribological characteristics of the human knee implant when operating in physiological conditions.

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Background: Although most pediatric VAD patients survive to transplantation, some die on device therapy. The end-of-life experience of pediatric VAD patients is not well characterized. Methods: Retrospective review of pediatric VAD patients in the ACTION registry who died on device therapy between 3/2012-9/2021. Demographic and clinical data, including invasive interventions used at the end of life and the location of death, were analyzed. Results: 107/721 (15%) of patients died on device at a median age of 5 years (IQR:1, 16) at 43 days (IQR: 17, 91) post implant. Goals of VAD therapy were bridge to candidacy for 50 patients (51%), bridge to transplant for 44 (37.6%), destination therapy for 2 (1.7%). The most common cause of death was multi-organ failure (n=35, 30%), followed by infection (n=12, 10.3%). Eighty-five of 92 patients (92.4%) died with a functioning device in place. Most patients were receiving invasive interventions (mechanical ventilation, 75%; vasoactive infusions, 62%) at the end of life (Table 1). Only 10 (9%) patients died at home. Conclusion: Aggressive interventions are common at the end of life of pediatric patients with VADs. Dying at home is uncommon. These data can inform future practices to promote informed patient and provider decision-making to reduce suffering at the end of life.