Understanding the uptake of new hip replacement implants in the UK: a cohort study using data from the National Joint Registry for England and Wales

Objectives Primary: describe uptake of new implant components (femoral stem or acetabular cup/shell) for total hip replacements (THRs) in the National Joint Registry for England and Wales (NJR). Secondary: compare the characteristics of: a) surgeons b) patients who used/received new rather than established components.
Design Cohort of 618,393 primary THRs performed for osteoarthritis (±other indications) by 4,979 surgeons between 2008-2017 in England and Wales from the NJR. We described the uptake of new (first recorded use >2008, used within 5 years) stems/cups, and variation in uptake by surgeons (primary objectives). We explored surgeon-level and patient-level factors associated with use/receipt of new components with logistic regression models (secondary objectives). 
Outcomes Primary outcomes: total number of new cups/stems, proportion of operations using new versus established components. Secondary outcomes: odds of: a) a surgeon using a new cup/stem in a calendar-year, b) a patient receiving a new rather than established cup/stem.
Results Sixty-eight new cups and 72 new stems were used in 47,606 primary THRs (7.7%) by 2,005 surgeons (40.3%) 2008-2017. Surgeons used a median of one new stem and cup (25%-75%=1-2 both, max=10 cups, max=8 stems). Surgeons performed a median total of 22 THRs (25%-75%=5-124, range=1-3,938) in the period 2008-2017. Surgeons used new stems in a median of 5.0% (25%-75%=1.3-16.1%) and new cups in a median of 9.4% (25%-75%=2.8-26.7%) of their THRs. Patients aged <55 years old versus those 55-80 had higher odds of receiving a new rather than established stem (OR=1.83, 95%CI=1.73-1.93) and cup (OR=1.31, 95%CI=1.25-1.37). Women had lower odds of receiving a new stem (OR=0.87, 95%CI=0.84-0.90), higher odds of receiving a new cup (OR=1.06, 95%CI=1.03-1.09).
Conclusions Large numbers of new THR components have been introduced in the NJR since 2008. 40% of surgeons have tried new components, with wide variation in how many types and frequency they have been used.