Almost 100 ACC-funded hip replacement surgeries last year were on hips that had already been replaced.

ACC funded 91 revision hip replacements last year at a cost of $4.97 million - an average of $54,623 per surgery.

The corporation also funded 165 first time total or partial hip replacements at a cost of $3.06m - an average of $18,560 per surgery.

The numbers had remained similar for the last 10 years according to ACC but information from the New Zealand Joint Registry showed the number of hip replacements was on the rise.

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The latest figures from the New Zealand Joint Registry showed there were 8373 initial hip replacement procedures and 1168 revision hip replacements in 2015.

According to the registry, the number of initial hip replacements was increasing each year - there were 1411 more in 2015 than 2007. The number of revision hip replacements remained fairly similar over the period.

New Zealand Orthopaedic Association president Dr Richard Keddell said the improvement in technology and surgery techniques as well as an increasing and ageing population were contributing to the increase.

He said it was estimated the number of hip surgeries had increased 75 per cent in the last decade and would continue to increase at the same rate.

"There's people growing older and more active and they are wearing their hips out," he said.

He said worn out hips were the main reason for a revision hip replacement but instability in the hip and infection also contributed.

Revision hip replacements were more complicated because they often required more complex procedures to address damage to the tissues around the hip resulting from the old worn-out joint, he said. This often involves the use of a much more expensive implant due to loss of surrounding bone. An initial operation could take 90 to 120 minutes but a revision operation could take up to five hours.

ACC communications manager James Funnell said most revision hip replacements were due to the ageing process and failure of the device was very uncommon. The life expectancy of a hip replacement was about 15 years but was dependent on the age of the patient and the type of implant.

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Because ACC only covered accidents and treatment injuries, the most common reason for a replacement implant was because of an infection that occurred at the time of the initial surgery, although that was not always picked up straight away.

It could take a while for the infection to manifest itself in a way that it could be picked up and antibiotics were usually tried before a decision to operate again was made, he said.

Funnell said, in New Zealand and worldwide, infections occurred in about 1 per cent of hip replacements.

Hip replacement fault "excruciating"

Lynne Walker had her third hip replacement surgery at the beginning of the year.

The 55-year-old developed arthritis in her hips in her early 40s and had one hip replaced in 2010 and the other in 2011.

"I was the best I'd been," she said.

After that, Walker thought she was done with surgery until a steel pin in one of her hips snapped as she walked across the kitchen. Surgeons told her it didn't happen often and was just bad luck.

"It was excruciating," she said.

Surgeons had to break her leg during the surgery to repair her hip. More than four months later she is still recovering and uses crutches to get around.