Novel design analysis tools to increase precision and reduce variation in hip replacement performance

Over 60 million patients worldwide suffer from hip osteoarthritis, and increasing numbers of patients are requiring total hip replacement surgery. Although the surgery is highly successful, the ageing active population and rise in obesity are placing extra demands on hip replacements: devices must now withstand higher loads and survive for longer durations in the body. The number of revision surgery procedures to replace worn out or damaged components is rising, and there is a need to develop more robust hip replacement devices that can withstand these increasing demands across all patient groups. One of the major causes of failure of hip replacements is due to wear and fatigue of the device components. These damage processes can increase dramatically if the components are not well aligned relative to each another, or relative to the direction of the loads they experience in the body. There can be many factors which affect the alignment, including the device design and surgical procedure as well as the patient anatomy and biomechanics.
In this proposal, we will develop computer models to simulate hip replacement performance under different misalignment conditions. We will incorporate patient and surgical variations into the model so that we can define exactly what levels of alignment are required for specific devices to operate adequately. This will enable us to provide better guidance on the choice of device for individual patients to reduce the likelihood of misalignment. It will also help inform surgeons on the positioning of the components for different patient characteristics.
We will work with a major orthopaedic company (DePuy Synthes) to integrate the computer models into their new product development process, so that the next generation of devices can be designed to be more robust to alignment variations, and surgical tools can be developed to help align devices with better precision in the most critical directions.
We will also work with regulators and standards agencies to develop new testing requirements that take account of the variations in patients and surgery, so that all new products will have to undergo more robust testing before they are introduced onto the market.
In the longer term, the methods we develop will help extend the lifetime and reliability of the next generation of hip replacements and enable these devices to meet the increasing demands of our ageing active population.

Over 60 million patients worldwide suffer from hip osteoarthritis and it presents an increasing burden on healthcare systems. There are growing clinical and economic needs to develop more robust, longer lasting hip replacements to meet the demands of an ageing, active population and reduce the rising cost of revision surgery.
The longer term impact of this proposal is to extend the lifetime and reliability of the next generation of hip joint replacements to meet these demands, benefitting patients, healthcare providers and the orthopaedic industry.
Through this proposal, we will develop novel design analysis and testing tools that can simulate the tribological and mechanical effects of patient and surgical variance on hip replacement performance. In the shorter term, the proposal will have impact on industry in providing new design tools for product development, clinicians in providing guidance on patient stratification for existing devices, regulatory and standard agencies in developing methods that enable surgical and patient variation to be incorporated into pre-clinical testing, and academia in developing new methodologies and highly skilled researchers, as well as promoting this application of engineering to the wider public.
For industry, we will develop computational simulation methods that can be integrated into the early design phase of new product development . We will work with Project Partner DePuy Synthes to enable the company to adopt the simulation tools in the design stage of their next generation total hip replacement systems. We will use two-way secondments between the university and DePuy Synthes as well as regular higher level meetings to ensure there is engagement throughout the project and a rapid transfer of technology. The proposed work will strengthen the capabilities of DePuy's newly opened research and development centre in Leeds, helping to drive economic growth. It will pave the way for future adoption across the industrial sector, and application to other replacement devices.
For clinicians, we will develop and validate the models on existing total hip replacement devices and use the models to identify the precision requirements beyond which detrimental tribological conditions will occur. We will investigate the effects of patient and surgical variation and use this to define improved patient stratification or surgical alignment methods for existing devices. We will work with our clinical collaborators and wider network to help disseminate findings and recommendations for current devices.
For standards and regulatory agencies, we will propose new, improved preclinical testing processes and requirements. We will use the results of our validation studies, alongside increasingly stringent performance requirements from NICE and demands from the clinical community for higher levels of compliance to advocate for improved pre-clinical testing and regulation that takes account of surgical and patient variation.
For academia, we will develop novel dynamic finite element simulation methods, as well as new techniques to incorporate patient and surgical variation in a parameterised way that enables rapid analysis of multiple variables. We will publish our methodologies and make methods and data available through our repository. We will also develop a database of patient image and gait data that will provide a resource for the wider community investigating other research questions. We will use the work to promote this application of engineering to the wider public through science fairs and patient-public engagement activities.