When metal implants in your body can leave you in even MORE pain
AFTER years of back pain, Pat taylor thought a hightech implant would finally bring relief. the retired secretary had tried numerous treatments over the years, but with the pain now impinging on her mobility, she was keen to try anything.
‘I was at a point where I’d tried everything, including cold packs from the freezer to acupuncture and various injections,’ she says. ‘But nothing helped and the pain was making me low — I hoped finally this would work.’
the device was inserted under the skin at the bottom of her spine. there, it emitted electrical currents that worked by interrupting the irregular nerve signals to the brain that sometimes cause chronic back pain. And it seemed to work — for the first time in years Pat was virtually pain free.
But last year, just over two years after she had the implant fitted, the 72-yearold from Bury St edmunds, Suffolk, was back in hospital having it removed — not because it didn’t work, but because her body had started to reject it.
‘I could always feel the implant under the skin, but two years after having it put in, the area became tender and sore,’ recalls Pat, who lives with husband Gerry, 77. ‘I started to feel really rundown and hot all the time and the terrible pain returned.’
Pat went back to hospital, but her consultant initially could not figure out exactly what was happening. Yet in September 2015, after repeated hospital visits, Pat was told her body was in effect rejecting the implant, and she needed surgery to take it out.
‘I had gone all that time using the stimulator with reasonable success, but suddenly the thing that was meant to help me actually left me with even more pain. No one had ever mentioned that this was a possibility,’ says Pat, a mother of two and grandmother of five.
Pat’s is not an isolated case. In fact, any metal implant or device — be it a spinal cord stimulator, as Pat had, dental implant to take the place of lost teeth, or hip and knee replacement — can potentially lead to a hypersensitivity reaction. even pacemakers can, in theory, be affected — although few cases have been recorded.
Hypersensitivity can occur when the body starts to view the metal implant as a foreign body and the immune system attacks it.
It differs from allergic reactions, as cells released as part of an allergic reaction are not involved in implant rejection.
WITH hypersensitivity, different immune cells launch an attack, triggering inflammation. And whereas an allergic response would be immediate, hypersensitivity can cause problems years after the implant is fitted.
‘Symptoms of hypersensitivity include pain around the joint and itchy skin — not necessarily at the site of the implant,’ says rishi Chana, a hip and knee joint replacement specialist at Ashford & St Peter’s NHS foundation trust and Surrey Orthopaedic Clinic
‘Because these are so vague, often the problem with the implant is not immediately identified.’
In some cases, such as Pat’s, the reaction and subsequent pain is so intense it can ultimately end in the implant having to be removed. People have a ‘spectrum of responses depending on their sensitivity,’ adds Mr Chana. ‘Some patients are very sensitive to small amounts of metal.’
‘I have seen patients who have experienced a delayed hypersensitivity reaction and rejected an implant after eight years of having it in,’ adds Alister Hart, a consultant hip and knee surgeon at the royal National Orthopaedic Hospital.
Implants are made from different metals. But, according to research, those made of nickel, cobalt and chromium are most likely to elicit a reaction; titanium is better tolerated by the body.
However, some implants contain separate parts made from different materials that can corrode and then cause hypersensitivity: the worst combination is when there is a titanium part next to a cobalt-chromium part — found in some hip replacements.
People who get a nickel rash when they wear watches are more at risk of reacting to their implant, says Mr Chana. that’s because patients get ‘sensitised’ to react to a certain metal and women are more at risk of this than men, adds Mr Hart. ‘this may be because they wear cheap jewellery which is made from nickel,’ he says. ‘Over time their body becomes sensitised to react to it and so when it comes to later in life and needing an implant — many of which contain nickel or metals that the body’s immune system “sees” as nickel — they reject the implant.’
Any implant can cause an issue, but it is the joint replacements that are most troublesome.
A recent review suggested that up to 5 per cent of all patients with total joint metal replacements and up to 21 per cent of patients with existing metal sensitivity may go on to develop hypersensitivity reactions when they are re-exposed to the same metal.
the delay in allergic reaction symptoms may be due to metal particles being released slowly from the implant, but which then go on to cause inflammatory reactions.
there are other possible causes too, adds Ashish Shetty, a consultant in pain medicine at University College London Hospitals.
‘for example, it is possible that a wire inside the implant breaks, so the nickel inside has been exposed,’ he adds.
research suggests a sensitivity reaction occurs in 0.2 per cent to 2 per cent of patients who have had a hip replacement.
But in those who have pre-existing reactions to nickel or other metals, the incidence rises to between 2 per cent to 4 per cent, says Mr Chana.
A study published recently in the journal BMC Musculoskeletal Disorders suggested that given the high percentage of hypersensitivity to metals (up to 10 per cent of the population), particularly to nickel, and the presence of nickel in standard knee implants, it ought to be crucial to check a patient’s sensitivity before surgery in order to prevent reactions.
Mr CHANA says he routinely asks all of his patients whether they react to costume jewellery and if they are able to wear a watch with a stainless steel back. ‘this can be a good screening tool and helps us identify patients who need to be treated as a reactive patient and, where possible, choose a hypoallergenic implant such as one containing plastic or titanium, which are better tolerated.’
Given the relatively low incidence of metal reaction, there is no routine testing. Before any operation, patients are given a questionnaire to answer which mentions allergies — but this is not specific to metals.
Some doctors offer a test called MeLISA, which can identify a metal reaction before implant surgery. It is a blood test that looks at the white blood cell reaction when exposed to various metals. However, the test is not available on the NHS and privately costs patients between £300 and £500, says Mr Chana.
Sometimes, the challenge is sifting through the symptoms and finding what’s causing them, he says.
‘there can be many issues that may be manifesting themselves with the same symptoms such as pain or swelling, so it is usually a case of eliminating the major risks such as infection or misalignment before we start considering the idea of a hypersensitivity reaction,’ he adds.
‘Patients are usually given physiotherapy and medication to reduce inflammation before anything else — revision surgery is always a last resort.’
Where possible, doctors can remove the metal implant and replace it with a hypoallergenic one, although there may be a compromise in terms of their function or quality, says Mr Chana.
‘By and large there should be a solution — for example, in hip replacements we have titanium implants that are better tolerated than other metal ones, or plastic implants; and there’s a type of knee replacement that has a special coating which doesn’t seem to lead to reactions,’ he adds.
Sometimes there’s no alternative replacement, as was the case for Pat. She is now on strong morphine-based drugs and pain patches for life, but remains optimistic about her future.
‘Sadly for me surgery didn’t work, but I have no regrets about trying it and would try other treatments given the chance.
‘I just think back to this time last year when I was in hospital after surgery and was very poorly and taking very high doses of painkillers such as morphine.
‘Some days are still bad and I can’t get out of bed, but in general I am getting better.
‘I take lower dose of painkillers now and try to make the most of my days.’