Reducing variation in hip replacement outcomes: understanding psoas tendon impingement

Total hip replacement (THR) is a successful operation but the number of devices requiring revision is continuing to rise. Up to 40% of patients report persistent pain after their surgery, and a cause is soft tissue impinging (specifically the iliopsoas tendon) against the replaced joint which can occur in around 5% of cases. Effective treatment is usually further surgery, consisting of release or resection of the iliopsoas tendon, alone or in combination with re-positioning the hip replacement cup to reduce the impingement. Some evidence suggests that there is a link between cup size and position, an individual patient's bony anatomy and posture, and symptomatic psoas impingement.
The aims of this study are to determine how an acetabular component can be positioned to avoid psoas impingement, given the anatomy and posture of an individual.
This project is co-funded by a major implant manufacturer, and will address an issue of relevance to both clinicians and industry to ensure the outcomes of hip replacement surgery for all patients are optimal. Additionally, the project will be co-supervised by an orthopaedic surgeon to provide a clinical perspective.
The project will involve characterising the relationship between bony and soft tissue anatomy (using cadaveric and imaging facilities) relating to psoas impingement and posture in a range of subjects, then developing a new computational model to define the wrapping path of the psoas tendon for use in predicting impingement. There will be opportunities to compare characterisation and modelling with an existing clinical data set of patients with symptomatic psoas impingement after hip replacement.
The project outcomes will provide evidence for surgical recommendations on component selection and position for different patients to avoid psoas impingement.