Probabilistic risk assessment and service life performance of load bearing biomedical implants

It is important to consider the performance of load bearing biomedical implants as a stochastic problem. This provides scope to optimise their whole life performance in terms of design and lifetime performance management measures with the aim of minimisation of the need for replacement, or the number of replacement, during the expected life of the patient. An important parallel is developed with the field of structural reliability analysis (i.e. probabilistic assessment) which has developed in recent years with great success in optimisation of whole life performance of load bearing infrastructure systems. The methodology considers the stochastic nature of loading on and resistance of an individual structure/structural network, within a probabilistic framework, to optimise performance over the whole life and at the same time to minimise the number of interventions required during the structures life. This paper demonstrates how this same methodology can be employed in the field of biomedical engineering to optimise the design and whole life performance of implants considering factors such as (i) deterioration with age, (ii) stochastic variation in load – e.g. as a function of the age of the patient, level of physical activity, weight etc. The paper also demonstrates the importance of Bayesian updating and correlation modelling in considering the design and whole life performance optimisation of biomedical implants.