Public funding for hip and knee joint replacements has barely changed since 2007 despite a surge in demand, new data from the University of Otago shows.
A study led by Professor David Gwynne-Jones at the Dunedin School of Medicine found surgery numbers are on the rise, but they're being outstripped by an increasing population.
Between 2006 and 2013 the number of publicly funded knee and hip operations increased by 6 percent, behind population growth - meaning the overall rate went backwards 0.6 percent.
"There's been an increase in the total number of hip and knee replacements done, but by looking at rates, we've looked at the adult population and that shows there really hasn't been a change," says Prof Gwynne-Jones.
District Health Boards are likely to see higher demand for the operations in the future.
Nearly one-third of New Zealanders aged over 65 are diagnosed with osteoarthritis, the most common reason for joint replacement surgery. Only 14 percent of New Zealanders are in this age group, but this is expected to rise to 27 percent in the next 50 years.
"This means demand… is likely to increase markedly in coming years, and the public health system will need to be adequately resourced to meet future demand."
There are also differences in rates between DHBs, with larger DHBs funding fewer operations per person than smaller ones.
The study is published today in the New Zealand Medical Journal, and is accompanied by an editorial which says knee and hip operations are losing out in the funding battle to treatments focused on "cancer, cardiac or kids".