ETHNIC DIFFERENCES IN THE UTILIZATION AND OUTCOME OF PATIENTS UNDERGOING TOTAL HIP AND KNEE ARTHROPLASTY IN NEW ZEALAND

Abstract

The New Zealand Joint Registry (NZJR) was established in 1999. However, ethnicity data was not recorded by prioritisation in line with Ministry of Health (MoH) recommendations. Recently, cross-referencing with MoH updated ethnicity data for all 326,150 entries in the NZJR database. The objective of this national level, population study was to identify any ethnic disparities in access and outcome for Māori for primary total hip (THA) and knee arthroplasty (TKA) for Osteoarthritis.The utilisation rate for THA and TKAs were calculated for the Māori and NZ European population from all data in the NZJR and Census data in 2001, 2006, 2013 and 2018. Utilisation rate was reported separately for four age groups (<55, 55-64, 65-74, >75) over four time periods (1999-2004, 2005-2009, 2010-2014, 2015-2020). Revision rate, 6 months and 5-year Oxford scores were adjusted for age, sex and BMI, then compared between groups.In every age group and at all but one time point, significant under-utilisation of TKA was observed in Māori. For THAs, Māori had similar utilisation rates in the <55 and 55-64 age groups, but significantly lower utilisation rates in all other age groups.When adjusted for age, sex and BMI, no significant differences in revision rates were observed between Māori and NZ Europeans for THAs (HR 0.939, P 0.417) or TKAs (HR 1.129, P 0.149). Adjusted 6 months and 5-year Oxford scores were significantly higher in NZ Europeans, however, the maximum difference was less than 3 points and is unlikely to be clinically significant.Despite the same risk of being diagnosed with osteoarthritis, Māori are less likely to undergo THA and TKA. There are no clinically significant differences in outcomes post arthroplasty between Māori and NZ Europeans. Further research is required to investigate causes for lower utilisation in Māori.