One in 12 implants used in hip replacements have no evidence to prove they are safe or effective, experts have warned.
Oxford University researchers trawled data relating to England and Wales and found 8% of devices that were used on patients were not backed by information proving they were safe.
Of all the hip implants potentially available to surgeons to use, 24% were not backed by evidence of safety or effectiveness.
The team warned that the system for regulating hip implants “seems to be entirely inadequate”, almost two years after a widespread scandal resulted in an alert being issued to the NHS.
In February last year, the Medicines and Healthcare products Regulatory Agency (MHRA) announced almost 50,000 patients with “metal on metal” hip replacements would need annual checks - including blood tests - over concerns they could cause serious health problems.
Those devices were linked to muscle and bone damage and neurological issues. Tiny metal ions made up of cobalt and chromium were thought to break off from the implants and leak into the blood.
The most recent research, published in the British Medical Journal (BMJ), involved a review of all hip implants used in surgery in 2011, taken from the National Joint Registry for England and Wales.
The team concluded: “This systematic review of the literature shows that 8% of primary hip replacement prostheses implanted in 2011 and recorded by the National Joint Registry had no readily available evidence relating to their safety or effectiveness.
“This is likely to be an underestimation of the true problem, as much of the evidence that does exist for the other unrated prostheses is of low quality or relates to short-term outcomes only.
“This is of great concern, particularly in light of the widespread publicity surrounding recent safety problems with regard to some resurfacing and other large diameter metal-on-metal joint replacements.”
The researchers said both professional and public confidence in the system was currently “at a low point”.
Their review found that 10,617 devices without available evidence of clinical effectiveness to support their use were implanted into patients in 2011.
These comprised 157 cemented stems, 936 uncemented stems, 1,732 cemented cups and 7,577 uncemented cups.
They were rated “unclassified” or “pre-entry” by the Orthopaedic Data Evaluation Panel (Odep) - the body that rates implants according to levels of evidence.
Manufacturers are requested, but not required, to submit data on their product to the Odep.
Products with less than three years of evidence are classified as “pre-entry”. Inclusion in this pre-entry category does not require evidence from peer reviewed literature at either the pre-clinical or clinical stages of development.
“Therefore, any data, regardless of whether it has been peer reviewed or not, can be submitted,” the researchers said.
Meanwhile, those devices that are “unclassified” have had no evidence submitted by the manufacturers.
In an accompanying editorial, researchers at Harvard Medical School argue that “the ability of manufacturers to promote devices or drugs that are authorised by regulators for widespread use but that do not have rigorous pre-approval data should be restricted.”
They said surgeons “should also ensure that their patients know about the benefits and risks of the new - but often unproved - medical devices that they are receiving.”
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