This study aimed to estimate the demand for total hip (THR) and knee replacements (TKR) by 2026 within New Zealand (NZ) and show how demographic factors are likely to influence this projection.
Yearly population data from the NZ Census was compared to the NZ Joint Register from 2001-2011 and ethnic and gender specific data was organised into 5 year age groups from 35 years to calculate the incidence for each age group. Poisson regression analysis was used to project the incidence for 2026 and to evaluate the independent associations between age, gender and ethnicity.
Between 2001 and 2011 the incidence of THR and TKR increased by 8.20% and 52.20% respectively with a peak incidence in the 70-74 age group. Men were less likely to undergo both THR and TKR (OR 0.91, 95% CI 0.89-0.94 and OR 0.88, 95% CI 0.89-0.90). By 2026 the absolute number of THR and TKR is estimated to increase by 84% (8950 procedures) and 183% (8613 procedures) respectively. Europeans were the most likely to undergo THR compared to Maori, Pacific people or Asians (OR 0.72, 95% CI 0.67-0.74). There was a large increase in the age standardised incidence of TKR for Pacific people and they were more likely to undergo TKR than Europeans (OR 1.00, 95% CI 0.97-1.04).
Over the past decade, incidence of THR and TKR have increased, and by 2026, the number of THR and TKR is projected to increase by 84% and 183% respectively. This increase will create a significant socioeconomic burden which will necessitate prudent and focused healthcare strategies to ensure that there are adequate resources to meet this demand.