The practice of using mixed parts in New Zealand hip operations has been criticised by a leading orthopaedic surgeon who says it is compromising patients' welfare.
The 2014 NZ Joint Registry report shows 44 per cent of the 7481 primary hip replacements performed in 2012 were fitted with parts made by different manufacturers.
At least 2500 joints used in operations are sourced from different companies.
The parts were sourced from different companies with many patients unaware they were being fitted with mixed parts.
England's Oxford University professor and orthopaedic surgeon Christopher Bulstrode has denounced the practice, saying he would never use mixed parts in hip replacement operations because there was no guarantee the parts would be compatible.
"If you mix two different makes together you are really in unproven territory because manufacturing competitors never check their product against someone else's," Bulstrode said.
Surgeons risked exposing patients to a range of possible reactions, he said.
"If the fit isn't right then it will wear very quickly and it will produce a particle of wear, and these particles stimulate the body to reject the whole replacement."
Bulstrode said in England and France manufacturers were paying off surgeons to use their products.
"I don't know what's happening in New Zealand but manufacturers all want to bring out new products . . . In France when you get a new hip replacement the manufacturer puts a € 100 note in the front of your right shoe. When you come out of surgery you have an extra € 100 tax free in your pocket. I think they call it sponsoring."
Bulstrode said in Britain it's a little bit more subtle.
"What tends to happen is that surgeons get sponsored to go to conferences in Aspen, Colorado, somewhere there is some good skiing or some good golf. In fact they don't turn up to much of the conference and the [sponsoring] reps don't expect them to."
New Zealand Joint Registry Board chairman and professor in orthopaedics Alistair Rothwell said surgeons were not sponsored in New Zealand.
Medical Council communications manager George Symmes said the council is "not able to make any comment about the legality of ‘sponsorship' or a ‘contract' with a supplier" and that the questions should be addressed to the Ministry of Health.
However, Waikato Hospital said mixing ball and socket parts is an accepted surgical method that is used internationally.
New Zealand Orthopaedic Association chief executive Flora Gilkison said mixed parts have a "similar" success rate to non-mixed parts.
"If you are asking if combinations are more or less successful than non-combinations then this is a complex question as it depends which ones but generally the answer is [yes]."
Asked why surgeons used mixed parts, Rothwell said it depended on the patient's "skeletal size and state".
But Bulstrode refuted that allegation.
"It is not right to say that the use of mixed parts depends on a patient's size. All manufacturers make a range of sizes for both femur and acetabulum. It is the surgeon who decides to mix them [most likely] because he ‘likes' one stem but likes another manufacturers ‘cup'."
Waikato Hospital orthopaedic surgeon Chris O'Meegan acknowledged patients were not told about the surgeon's decision to mix implants but said that he would discuss the different materials used - for example, ceramic parts versus metal parts.
"Specific manufacturers are not [discussed] except when patients occasionally ask," O'Meegan said, adding the "practice is nothing new."
"I recall using ‘mixed' components on a frequent basis when I was training in Christchurch in the early 1990s."
O'Meegan said from the Waikato DHB surgeons' point of view, "age or cost" were not significant issues in terms of implant selection.
"The best implant for the patient's anatomy that the surgeon is familiar with are generally used . . . Hybrid combinations are felt to be better especially in patients with limited bone stock in the femur for a number of reasons and the results in the Swedish and New Zealand registers show that the results are satisfactory."
The Waikato Times requested information about patients who needed a second surgery to fix or replace a mixed implant hip replacement.
Waikato District Health Board communications director Mary Anne Gill said the information would take too long to collate.
"These three questions have been identified as likely to take this amount of time and accordingly we intend to invoice you for the request," Gill said.
In an email Gill said the Times would be billed $9120 for the information.
A hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant.
A total hip replacement (total hip arthroplasty) consists of replacing both the acetabulum and the femoral head.
Hip replacement is currently the most common orthopaedic operation.
- Waikato Times