Osteoporosis is a very common condition
A company making a drug for osteoporosis has won a High Court case against the NHS drugs advisory body.
Servier, which makes Protelos, says the National Institute for Health and Clinical Excellence unfairly restricts access to the treatment.
The judge ruled NICE had failed to be as transparent as it could have been in drawing up the guidance.
It means NICE will have to reconsider the guidelines but not necessarily that the advice will change.
The case is the first successful legal challenge against NICE guidelines although the judge warned people not to take "false hope" from the case.
Osteoporosis is a progressive disease in which bone tissue deteriorates, putting people at risk of fracture.
It is particularly common in post-menopausal women.
Around one in three and one in five men will suffer an osteoporotic fracture in their lifetime.
In guidelines for England and Wales published last year, NICE recommended a drug called alendronate as a first-line treatment.
But around one in four patients cannot tolerate it due to side-effects.
NICE then recommends other options, including Protelos or strontium ranelate, but the patient's condition needs to have deteriorated before they are eligible.
Servier calculates this would leave the 15% of women with osteoporosis who cannot take or tolerate bisphosphonates unprotected from the risk of fracture - potentially for many years.
The company appealed against the guidance on the grounds that there had been a lack of transparency around the economic model used to make the decision.
It also said that the guidance misinterpreted the company's clinical data around hip fracture data and infringed rights under EU and UK discrimination law on the basis of disability.
In the High Court, Mr Justice Holman, agreed NICE had failed to be as transparent as it should have been.
NICE will have to disclose the economic model it used in the guidelines and take on board fresh expert advice.
On the other two grounds the High Court ruled in favour of NICE.
Professor Peter Littlejohns, NICE clinical and public health director, said: "The judge agrees that NICE was correct in not releasing 'in confidence' information but nevertheless considered that, although we had asked for permission to release the information, NICE could have done more to arrange for that information to be available.
"NICE will now make every endeavour to encourage the owner of the information to allow us to release this information."
He added that the judgement was not about the recommendations in the guidelines but a step in the decision-making process.
Professor Tim Spector, consultant rheumatologist at St Thomas's Hospital in London, said as they stood the guidelines meant doctors could put someone on the first drug but if they could not tolerate it, they might have to wait three years for the patient to deteriorate before they could have a second choice.
He said clinicians were ignoring the guidelines because they were too complicated.
"The message is that NICE should reconsider, to take on board the clear consensus and make these guidelines more practical and more flexible or no one will pay any attention to them."
Servier said they were satisfied with the ruling.
But they pointed out the judge has not yet taken a decision on whether the guidance will be quashed.
Nick Rijke, from the National Osteoporosis Society said: "We welcome today's judgement, which finally gives us the proper access to the economic modelling that NICE use to decide which treatments the NHS should prescribe.
"At last we will have the opportunity to prove that giving patients and doctors a wide range of treatment options is cost effective."