Image caption The head of the thigh bone and the socket of the pelvis is replaced with metal parts (yellow) in resurfacing

An operation used instead of a full hip replacement has a high failure rate and, in most instances, should no longer be offered, warn doctors.

Their advice is based on figures from the largest database on hip surgery.

Hip resurfacing - where the damaged bone is capped rather than replaced - is often recommended for younger, active patients who will need more surgery as the joint continues to wear.

Medical regulators say they will look at the Lancet journal findings.

The UK's Medicines and Healthcare products Regulatory Agency (MHRA) has already advised annual checks for people with large head metal-on-metal full hip replacements due to safety concerns. It is thought tiny pieces of metal can break off and leak into the blood.

The current study did not look at the safety of the metal resurfacing implants, although the researchers say there could be the same theoretical safety risk as with metal-on-metal hips.

Resurfacing failure rates in women were unacceptably high Prof Ashley Blom, Lead researcher

Instead it looked at failure rates with metal-on-metal resurfacing - where the socket and ball of the hip bone has a metal surface applied to it rather than being totally replaced.

About seven in every 100 hip patients go for resurfacing rather than a full hip replacement, although the rate has been decreasing in recent years.

Some 32,000 people in England and Wales had this type of surgery between April 2003 and September 2011.

The Bristol University team looked at the National Joint Registry data to see how many of these implants failed in the first seven years after surgery and how they compared with conventional full or "total" hip replacements.

'Not for women'

The resurfacing implants failed more quickly than total hip replacements.

The five-year failure rate was about 5% on average compared with less than 2% for total hip replacement.

The failure rate in women was so high - up to five times greater - that the researchers believe resurfacing implants should never be used in women.

Similar, they should not be recommended to men - the only exception is men with particularly large hip bones who appear to fare as well with resurfacing as with a total hip replacement, say the researchers.

For some patients a resurfacing hip implant may be the most clinically appropriate implant for them Dr Nicola Lennard, MHRA

They estimate that a quarter of men may have bones large enough for resurfacing.

Prof Ashley Blom, who led the investigation said: "Resurfacing failure rates in women were unacceptably high. In view of these findings, we recommend that resurfacing procedures are not undertaken in women."

He said decisions about resurfacing procedures in men should be made carefully and only after measuring the size of the bones that are to be repaired or replaced.

But he said any person who has already been fitted with one should not be alarmed by the findings.

An advantage to resurfacing is that it is less invasive than a total hip replacement and leaves you with a greater range of movement after surgery.

New, stronger materials for prosthetics are being developed that will allow longer wear and better joint mobility.

Between April 2010 to April 2011, the NHS performed just over 70,000 hip replacements in England.

Dr Nicola Lennard, of the MHRA, said: "Decisions about what hip implants to use in patients are made by clinicians after careful consideration of the risks and benefits for each individual patient.

"For some patients a resurfacing hip implant may be the most clinically appropriate implant for them."

She said the MHRA was continuing to closely monitor all the latest evidence about these implants.