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Welcome to the BMJ Open blog. BMJ Open is an open access journal, dedicated to publishing medical research from all disciplines and therapeutic areas.

Find out more about the journal here.

We will be updating the blog with news about the journal, highly accessed papers, press coverage, events and matters of interest in the open access and publishing world, and anything else that catches our eye.

Top 10 Most Read: Cholesterol and mortality in the elderly, chronic pain in the UK and smokers’ quitting attempts

8 Jul, 16 | by Ed Sucksmith

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Several new entries make it into our top 10 Most Read list this month. In first place is a systematic review on the associations between low-density-lipoprotein cholesterol and mortality in the elderly. Further down the list is an analysis of Italian medical societies’ websites to examine conflicts of interest between professional medical societies and industry. Other new entries this month include an investigation into the relationship between air pollution and child and adolescent mental health by researchers from Umeå University in Sweden. Using a cohort of over half a million individuals under 18 years of age, the authors found that neighbourhood air pollution concentration is associated with dispensed medications for certain psychiatric disorders. At number 6 is a systematic review and meta-analysis of the prevalence of chronic pain in the UK. The authors conclude that chronic pain affects between one-third and one-half of the population of the UK, corresponding to just under 28 million adults. Lastly, making it in at number 9 is a study by Chaiton and colleagues on smokers’ quitting behaviour. The authors found that it may take as much as 30 or more attempts before a smoker quits successfully.

 

Rank Author(s) Title
1 Ravnskov et al. Lack of an association or an inverse association between low-density-lipoprotein cholesterol and mortality in the elderly: a systematic review
2 Eleftheriou et al. Does attractiveness influence condom use intentions in heterosexual men? An experimental study
3 Oudin et al. Association between neighbourhood air pollution concentrations and dispensed medication for psychiatric disorders in a large longitudinal cohort of Swedish children and adolescents
4 Fabbri et al. Conflict of interest between professional medical societies and industry: a cross-sectional study of Italian medical societies’ websites
5 Kristensen et al. The effect of statins on average survival in randomised trials, an analysis of end point postponement
6 Fayaz et al. Prevalence of chronic pain in the UK: a systematic review and meta-analysis of population studies
7 Teschke et al. Bicycling injury hospitalisation rates in Canadian jurisdictions: analyses examining associations with helmet legislation and mode share
8 Thomas et al. When procedures meet practice in community pharmacies: qualitative insights from pharmacists and pharmacy support staff
9 Chaiton et al. Estimating the number of quit attempts it takes to quit smoking successfully in a longitudinal cohort of smokers
10 Fenton et al. Systematic review of the association between dietary acid load, alkaline water and cancer

Most read figures are based on pdf downloads and full text views. Abstract views are excluded.

Third to half of UK population lives with chronic pain

20 Jun, 16 | by Emma Gray

Proportion likely to rise as population ages; major cause of disability and distress

Between a third and half (43%) of the UK population—roughly 28 million adults—lives with chronic pain, finds an analysis of the available evidence, published in the online journal BMJ Open.

This proportion is likely to rise as the population ages, warn the researchers, who add that chronic pain is a major cause of disability and distress among those affected by it.

There is no consensus on the proportion of people living with long term pain in the UK, and in a bid to try and gain an accurate picture, the researchers trawled relevant databases to find research on different types of pain, published after 1990.

Their search included studies on population based estimates of chronic pain—defined as lasting more than 3 months—chronic widespread pain, fibromyalgia (a rheumatic condition characterised by muscular or musculoskeletal pain), and chronic neuropathic pain (pain caused by nerve signalling problems).

From among 1737 relevant articles, 19 studies, involving just under 140,000 adults, were deemed suitable for inclusion in the final analysis.

They pooled the study data to arrive at an estimate of the prevalence of chronic pain, overall, and chronic widespread pain. Summary estimates were also drawn up for moderate to severely disabling chronic pain, fibromyalgia, and chronic neuropathic pain among UK adults.

Based on seven studies, the researchers worked out that the prevalence of chronic pain ranged from 35% to 51% of the adult population, with the prevalence of moderate to severely disabling chronic pain (based on four studies), ranging from 10% to 14%—equivalent to around 8 million people.

Pooling of the data showed that 43% of the population experience chronic pain, and 14% of UK adults live with chronic widespread pain. The summarised data also showed that 8% of UK adults experience chronic neuropathic pain, and 5.5% live with fibromyalgia.

Twelve of the studies categorised the prevalence of pain by age group, and unsurprisingly, these showed that older people were more likely to live with pain over the long term.

Among 18-25 year olds, the prevalence was 14%, although it may be as high as 30% among 18-39 year olds, the analysis indicates—a sizeable chunk of the working population, say the researchers.

Among those aged 75 and above, the prevalence was almost two thirds (62%), suggesting that if current trends continue, the burden of chronic pain may increase further still as the population ages, say the researchers.

Women were more likely than men to be affected by chronic pain, irrespective of age or pain type.

The researchers point out that the included studies varied considerably, and that not all of them were of high quality, so making it difficult to draw firm conclusions.

The studies showed gradually increasing prevalence of chronic pain over time, from 1990. And the researchersestimate that the prevalence of chronic pain in the UK is now around 43%, equating to around 28 million people, based on population stats for 2013.

“Such prevalence data does not itself define need for care or targets for prevention, but reliable information on prevalence will help to drive public health and healthcare policymakers’ prioritisation of this important cause of distress and disability in the general population,” they conclude.

Drug treatment of hyperactivity in kids may have levelled off in UK

20 Jun, 16 | by Emma Gray

But it lasts much longer than it does in rest of Europe or US

The tendency to treat childhood hyperactivity (ADHD) with drugs may have reached a plateau in the UK, following a steep rise in the number of prescriptions for these medicines over the past 20 years, reveals research published in the online journal BMJ Open.

But when kids with attention deficit and hyperactivity disorder (ADHD) do go down the pharmacological route, their treatment lasts for much longer than that of their European or US peers, the findings show.

Drugs are one of several treatment options for ADHD, which includes parental training and behavioural therapies. ADHD drugs have been in use since the 1960s and are on the World Health Organization’s list of essential medicines for common psychiatric disorders.

The researchers base their findings on an analysis of Clinical Practice Research Datalink (CPRD) records, relating to children up to the age of 16 who had been prescribed at least one drug to treat ADHD between 1992 and 2013.

The CPRD is one of the world’s largest collections of long term anonymised primary care medical records. It is broadly representative of the UK population, covering around 8% of the total.

The researchers analysed the data to estimate trends in ADHD prescribing patterns among children between 1995 and 2013, and the length of treatment for those diagnosed with the condition.

During this period, 14,748 children under the age of 16 (85% of them boys) were given at least one prescription for an ADHD drug, with methylphenidate accounting for 94% of all prescriptions.

Over half (58%) of the children received their first prescription between the ages of 6 and 11; around 4% were 5 years old when they were first prescribed an ADHD drug.

The use of these drugs in this age group soared by a factor of 35, from 1.5 per 10,000 children in 1995 to 50.7/10,000 in 2008, after which it seemed to level off at 51.1/10,000 children by 2013.

The rate of new prescriptions rose 8-fold over the same timeframe, reaching 10.2 per 10,000 children in 2007, but subsequently falling to 9.1/10,000 in 2013.

These patterns may reflect the impact of National Institute for Health and Care Excellence guidelines issued in 2008, and/or concerns about the potential impact on the heart of long term use, suggest the researchers.

UK prescribing rates for ADHD drugs are considerably lower than they are in many other countries, the researchers point out. They are 10 times lower than in the US, up to 5 times lower than in Germany, and 4 times lower than in the Netherlands, although UK rates are twice as high as in France.

Nevertheless, the course of treatment tends to be longer than in these countries, the published evidence indicates. More than three out of four UK children (around 77%) were still being prescribed ADHD drugs 1 year after diagnosis and 60% were still on treatment 2 years later, the figures show.

The probability of stopping ADHD drugs within six years seemed to be higher in 11-15 year olds than it was in 6-10 year olds, the data showed, which may indicate that treatment is being stopped too early among young adults, say the researchers.

This is an observational study, and the researchers point out that their analysis cannot determine the causes behind the prescribing patterns they found. Furthermore, the data relate only to  the issuing of prescriptions, and not to their being dispensed or drugs actually taken.

But they conclude: “Although the prevalence and incidence of ADHD drug use in children have substantially increased during the past two decades, it seems that it may have reached a plateau recently…Our study indicates a turning point in the patterns of ADHD drug prescribing in children in the UK.”

Prolonged sitting, non-fatal self-harm, and institutional mental healthcare: Most read articles in May

6 Jun, 16 | by Emma Gray

Prolonged sitting and fatigue, non-fatal self-harm, and trends in institutional mental healthcare in Western Europe

File:Une femme lisant à la biblothèque des Champs Libres de Rennes.jpg

This month sees a mixture of some old favourites and some new entries in the Top 10 Most Read list. First up is a pilot study by Wennberg et al which uses a randomised two-condition crossover trial to compare the acute effects of uninterrupted sitting with sitting interrupted by brief bouts of light-intensity walking on self-reported fatigue, cognition, neuroendocrine biomarkers and cardiometabolic risk markers in overweight and obese adults. Kristensen et al‘s paper on the effect of statins remains popular at number two this month and at number four we have an observational study by Geulayov et al which received a press release – it examines trends in non-fatal self-harm and its management in England. In at number five this month is a study by Chow et al investigating how institutional mental healthcare has changed in Western Europe since 1990, finding that there are ongoing overall trends of a decrease in the number of psychiatric hospital beds and an increase in the number of places in other institutions, including prisons. Last month’s most read paper by Gunn et al remains in the top ten, and at number ten we have a new entry by Laver et al with a systematic review of systematic reviews, assessing the effects of interventions to delay functional decline in people with dementia.

Rank Author(s) Title
1 Wennberg et al. Acute effects of breaking up prolonged sitting on fatigue and cognition: a pilot study
2 Kristensen et al. The effect of statins on average survival in randomised trials, an analysis of end point postponement
3 Teschke et al. Bicycling injury hospitalisation rates in Canadian jurisdictions: analyses examining associations with helmet legislation and mode share
4 Geulayov et al. Epidemiology and trends in non-fatal self-harm in three centres in England, 2000–2012: findings from the Multicentre Study of Self-harm in England
5 Chow et al. How has the extent of institutional mental healthcare changed in Western Europe? Analysis of data since 1990
6 Dickstein et al. Multicentre open-label randomised controlled trial to compare colistin alone with colistin plus meropenem for the treatment of severe infections caused by carbapenem-resistant Gram-negative infections (AIDA): a study protocol
7 Martinez Steele et al. Ultra-processed foods and added sugars in the US diet: evidence from a nationally representative cross-sectional study
8 Gunn et al. Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis
9 Hirono et al. Is health impact assessment useful in the context of trade negotiations? A case study of the Trans Pacific Partnership Agreement
10 Laver et al. Interventions to delay functional decline in people with dementia: a systematic review of systematic reviews

Most read figures are based on pdf downloads and full text views. Abstract views are excluded.

International Clinical Trials Day

19 May, 16 | by aaldcroft

By Sir George Chalmers, c 1720-1791 - [1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=32922810

Today is Clinical Trials Day. Celebrated around the world on or near May 20, Clinical Trials Day commemorates the date when, in 1747, James Lind started the first clinical trial to test citrus fruits as a treatment for scurvy.

This year’s campaign from the NIHR is OK To Ask, which encourages patients and carers to inquire about research opportunities that could be available. We here at BMJ Open support initiatives for patient involvement in research and decision-making and hope that, in making our content freely available online, we help make research more familiar and accessible to the public, including patients, for whom the research is ultimately intended.

While James Lind’s basic principle for the trial remains, the scale, sophistication, and problems surrounding modern trials are evolving rapidly. The importance of registering drugs and publishing all trial results is recognised, but adherence remains unsatisfactory. The notion of what constitutes an intervention is also changing, with text messaging and educational methods now being studied using the same framework as drugs.

BMJ Open will continue efforts to improve the quality of reporting trials, emphasizing the importance of publishing null and negative results and study protocols. The clinical trial is certainly worthy of celebration, along with improvement.

Celebrating International Nurses Day #IND2016

12 May, 16 | by Emma Gray

 

International Nurses Day, celebrated on 12th May each year and coinciding with Florence Nightingale’s birthday, marks the important contributions nurses make to society. As the single largest group of health professionals, nurses care from the first moments of life right through to the final days. To show our appreciation of the work that nurses do, BMJ Open are joining in the celebrations today with a round-up of some of our most popular papers on nursing.

Published in 2015, Dall’Ora et al surveyed registered nurses across 12 European countries to find associations between working 12 hour shifts and job satisfaction, burnout and intention to leave. Receiving over 10,000 downloads since publication, this paper has some important conclusions, finding that longer work hours were indeed associated with adverse outcomes – not only for nurses but potentially for patients as well.

Also published last year was a cross-sectional study into the prevalence of workplace violence that nurses have encountered in Chinese hospitals. The authors, Jiao et al, found that a total of 7.8% of the nurses interviewed for the study had experienced physical violence at work in the previous year, and 71.9% reported experiencing non-physical violence. They aimed to identify risk factors and provide a basis for future interventions, concluding that preplacement education for high-risk groups should take place to reduce workplace violence, and increased awareness from the public as well as policymakers is necessary to develop effective control strategies at individual, hospital and national levels.

One of our most popular papers this year, receiving a press release and over 7,000 downloads since its publication in February, is the paper ‘Registered nurse, healthcare support worker, medical staffing levels and mortality in English hospital trusts: a cross-sectional study’ by Griffiths et al.  Aiming to examine associations between mortality and registered nurse staffing in English hospital trusts, the authors found that ward-based registered nurse staffing is significantly associated with reduced patient mortality, as are higher doctor staffing levels. They conclude by saying that current policies and practices on the staffing in hospital wards should be reviewed in line with the evidence, to reduce risks to patients.

A paper by Schlicht et al published back in 2013 sought to determine the safety and acceptability of the Australian TrueBlue model of nurse-managed care of depression in patients with diabetes or heart disease in the primary healthcare setting. Using a mixed methods study involving a clinical record audit as well as focus groups and interviews with nurses, the study found that nurses were able to identify, assess and manage mental health risks in patients with diabetes or heart disease.  The nurse consultations also meant that there was an opportunity for patients to set goals, as they received scheduled follow-up visits and were monitored regularly, leading to stepped care when appropriate.

The final paper in this short overview of our content on nursing is a review of the cost-effectiveness of nurse practitioners in primary and specialised ambulatory care. A systematic review of randomised controlled trials, conducted by Martin-Misener et al, found that nurse practitioners in alternative provider ambulatory primary care roles have equivalent or better patient outcomes than comparators and are potentially cost-saving. This evidence is promising, but there are few studies contributing to this evidence base at the moment: the authors conclude that while some evidence indicates nurse practitioners in complementary specialised ambulatory care roles improve patient outcomes, their cost-effectiveness requires further study.

More on International Nurses Day:

BMJ is offering free content and discounts on resources for nursing professionals until 12th June: 

To join in with the celebrations, tweet today to show appreciation of nurses using the hashtags #thankanurse #IND2016 and #InternationalNursesDay

Radiotherapy during surgery could save millions of travel miles and tonnes of CO2

9 May, 16 | by Emma Gray

…plus free up thousands of hours for women with early stage breast cancer, every year

One targeted dose of radiotherapy given during surgery to remove early stage breast cancer could save millions of travel miles, enough CO2 emissions for a 100 hectare forest, and free up thousands of hours of women’s time, concludes research published in the online journal BMJ Open.

Standard treatment for early stage breast cancer is surgical removal of the cancerous tissue (lumpectomy), followed by a course of (external) radiotherapy beamed onto the affected breast every day for between three and six weeks.

But single dose targeted intraoperative radiotherapy, or TARGIT for short, is delivered by an applicator directly into the breast tissue during surgery. This adds around 20 to 40 minutes to the operating time, but in most cases avoids the subsequent need for daily hospital visits to complete a standard course of radiotherapy.

Previous international research (TARGIT-A trial) indicates that TARGIT is as good as standard external beam radiotherapy (EBRT) in suitable patients with early stage disease, and it is routinely offered as a treatment option in many countries, say the researchers. But TARGIT is not yet widely available in the UK’s 62 hospitals with radiotherapy units.

To assess the travel implications, journey times, and environmental impact of TARGIT and EBRT, the researchers compared these factors in 485 patients who had taken part in the TARGIT-A trial, 249 of whom had been randomly assigned to TARGIT and 236 to EBRT.

They also included a further 22 patients treated with TARGIT in two other semi-rural centres after the trial had finished.

They calculated the shortest driving distance from home to the radiotherapy unit and average travel time, excluding traffic delays, using Google Maps. They then calculated the total distance travelled and time spent to complete the entire course of radiotherapy.

On average, TARGIT-A trial participants in the UK live 13 miles (21 km) from a radiotherapy unit, and accounting for population density, the researchers estimated that two thirds of the UK population lives further away than this.

CO2 emissions were estimated for a standard family car with an average fuel consumption of 40 miles/gallon (7 litres/100 km). This would produce 299 g/mile (186 g/km) of CO2 emissions for a diesel car and 272 g/mile (169 g/km) for a petrol vehicle.

The TARGIT patients travelled significantly fewer miles (21,681) than EBRT patients (92,591) for their treatment, and spent significantly less time in transit: 3 hours compared with 14 hours.

Their journeys also emitted significantly less CO2: 24.7 kg compared with 111 kg for the EBRT patients.

The researchers worked out that the patients treated in the two semi-rural radiotherapy units each saved themselves journeys adding up to 753 miles, 30 hours of travel time, and they spared the planet 215 kg of CO2.

There are around 50,000 cases of breast cancer diagnosed in the UK every year, of which around three quarters are treated with lumpectomy and EBRT.

Based on these figures, the researchers calculate that if TARGIT became widely available across the UK,  it could save 5 million miles (800,000 km) in journeys, 170,000 hours of travel time, and 1200 tonnes of CO2—equivalent to a forest of 100 hectares—every single year.

This is a lot ‘greener’ than the estimated environmental benefits of introducing mobile breast cancer screening, they say.

“The management of breast cancer has changed over the decades. However, the requirement of patients to travel to receive these specialist services is often forgotten by policy-makers,” they write.

And they conclude that “introducing TARGIT as an option for appropriate patients in the UK will contribute significantly to saving patients time, cost, fuel and CO2 emissions.”

Prenatal exposure to cannabis, overdiagnosis, and counterfeit medicines: Most read articles in April

9 May, 16 | by Emma Gray

Prenatal exposure to cannabis, public definitions of overdiagnosis, and counterfeit medicines in Peru

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The Top 10 Most Read papers list this month contains a number of new entries, many of which have been published within the current issue. They come from a wide range of of areas and some have attracted attention via press release, blogs and discussion online. In the top spot is a systematic review and meta-analysis by Gunn et al which was published with an accompanying press release at the start of the month, assessing the effects of use of cannabis during pregnancy on maternal and fetal outcomes. In at numbers 3 and 5 respectively are Medina et al with a retrospective review on drug alerts related to counterfeit medicines in Peru; and Hirono et al, who explore the usefulness of health impact assessment in trade negotiations. Complete with an interview with the lead author on the BMJ Open blog, Ghanouni et al enter the list at number 8 with their survey of public definitions of the term ‘overdiagnosis’ in the UK, and Esch et al examine patient engagement through open notes at number nine. Making it in at number ten this month is a cross-sectional study on polypharmacy by O’Dwyer et al, which evaluates polypharmacy in older people with intellectual disability, compared with the general population.

Rank Author(s) Title
1 Gunn et al. Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis
2 Kristensen et al. The effect of statins on average survival in randomised trials, an analysis of end point postponement
3 Medina et al. Counterfeit medicines in Peru: a retrospective review (1991-2014)
4 Martinez Steele et al. Ultra-processed foods and added sugars in the US diet: evidence from a nationally representative cross-sectional study
5 Hirono et al. Is health impact assessment useful in the context of trade negotiations? A case study of the Trans Pacific Partnership Agreement
6 Teschke et al. Bicycling injury hospitalisation rates in Canadian jurisdictions: analyses examining associations with helmet legislation and mode share
7 Boulton et al. How much sugar is hidden in drinks marketed to children? A survey of fruit juices, juice drinks and smoothies
8 Ghanouni et al. Survey of public definitions of the term ‘overdiagnosis’ in the UK
9 Esch et al. Engaging patients through open notes: an evaluation using mixed methods
10 O’Dwyer et al. Factors associated with polypharmacy and excessive polypharmacy in older people with intellectual disability differ from the general population: a cross-sectional observational nationwide study

Most read figures are based on pdf downloads and full text views. Abstract views are excluded.

Hospital self-harm cases have steadily risen among men in England since 2008

28 Apr, 16 | by Emma Gray

But only half of those going to hospital afterwards get mental health assessment

The number of hospital cases of self-inflicted harm, such as cutting and overdosing on prescription meds, has risen steadily since 2008 in England among men, reveals research published in the online journal BMJ Open.

But only around half of those who go to hospital after the incident receive a specialist mental health assessment, as national guidelines stipulate they should, the data show.

This is of particular concern as episodes of self-harm precede death in one in every two cases of suicide, the researchers point out.

The researchers base their findings on reported cases of self-harm among people aged 15 and older at five general hospitals in the cities of Oxford, Manchester, and Derby between 2000 and 2012. Self-harm includes intentional injury and overdosing on prescription drugs.

The three cities are all part of the Multicentre Study of Self Harm in England. Because they are socially and economically diverse, the study participants are reasonably representative of urban patterns of self-harm across the country, say the researchers.

During the 13-year study period, 84,378 episodes of self-harm involving 47,048 people were dealt with at the five hospitals. Well over half of these cases (58+%) were among women.

Almost four out of 10 people were under 25, and nearly two thirds (62%) were under 35. Almost a third (30%) were receiving some form of psychiatric care when they self-harmed.

Overall, rates of self-harm fell among women from 2000 onwards. They also fell in men, but only until 2008, after which they steadily rose, possibly because of the effects of the economic downturn, suggest the researchers.

The rates of self-harm closely mirrored patterns of suicide seen in the general population, for both men and women.

An intentional overdose was responsible for more than three quarters of the episodes. Of these, common painkillers were used in over half the overdoses, while antidepressants were used in one in four (just under 25%).

Benzodiazepines, a class of drugs used to treat anxiety and sleep problems, were used in around one in seven cases (just under 14%), while major tranquilisers and antipsychotics were used in around 7% of cases.

A sharp increase in reported cases of cutting/stabbings and hanging/strangulation occurred in the second half of the study period.

“It should be noted that there is a stronger risk of suicide following self-cutting compared to self-poisoning,” write the researchers, adding: “Also repetition of self-harm is more common in individuals who cut themselves.”

One in four people self-harmed again within a year.

Overall, the proportion of people getting a specialist mental health assessment following their visit to hospital was greater in 2012 than in 2003, although this varied among the five hospitals.

Nevertheless, only just over half (53%) of 67,653 episodes of self-harm were followed up with a mental health assessment, as recommended in 2004 by the National Institute of Health and Care Excellence (NICE).

This was particularly true of people who cut themselves, with only just over a third (38%) of those who chose this method receiving an assessment, compared with more than 56% of those who overdosed.

“Our finding that only a little over a half of individuals presenting to hospital after self-harm were offered psychosocial assessment and that individuals who self-injured were least likely to receive an assessment, coupled with the rise in self-injury as a method of self-harm, and the link between such methods and suicide, may have important implications for the management of self-harm in hospitals,” suggest the researchers.

Metal hip replacements implanted since 2006 more prone to failure

28 Apr, 16 | by Emma Gray

Higher rate of issues in manufacturing process since this date may be to blame, say researchers

Metal on metal hip replacements implanted since 2006 are more prone to failure and the need for further surgery, finds research looking at revision rates at one hospital trust for the DePuy Pinnacle device, and published in the online journal BMJ Open.

A higher rate of manufacturing issues since 2006, with more than a third of hips manufactured outside the stated specifications, may be to blame, suggest the researchers.

They looked specifically at the long term performance of the 36 mm Pinnacle metal on metal hip—the most commonly implanted metal hip in the world—in a bid to uncover the risk factors associated with early failure and the need for further surgery.

The use of metal on metal hips has plummeted over the past five years, but “hundreds of thousands” remain in place. A better understanding of the factors associated with a higher risk of failure would not only help those patients fitted with them, but could also inform the design of future products, say the researchers.

They reviewed the progress of 434 patients (243 women and 191 men) fitted with 489 metal on metal total hip replacements at one hospital trust in northern England, and monitored for an average of 7.5 years after the procedure.

In all, 71 metal hips required surgical removal and replacement, adding up to a revision rate of 16.4%, which the researchers describe as “unacceptably high.”

A metal on metal hip consists of a metal ‘ball,’ which acts as the top of the thigh bone (femoral head). This fits inside a metal liner, which acts as the replacement socket.

Total replacement of both (bilateral) hip joints and thinner liners were risk factors for failure at nine years.

But implantation from 2006 onwards also carried a significantly higher risk of revision, possibly because of the increasing tendency from this date to manufacture devices outside of their intended product specification, say the researchers.

Before 2006, only five out of 43 hips (12%) failed to meet the manufacturer’s product specification. But after 2006 more than a third (36%; 43 out of 118) failed to comply.

Furthermore, in over 40% of cases examined the taper surface was defective. The taper surface describes the inside of the femoral head that is attached to the femoral stem—the part that anchors the implant in the thigh bone. This defect was significantly associated with excessive metal particle release.

Abundant metal staining of tissues visible to the naked eye (metallosis) had occurred in around one in five (19%) cases.

Metal hips implanted into women were also more likely to fail, but the researchers caution that twice as many women as men had bilateral hip replacements, and when the findings were analysed according to sex and liner thickness, thinner liners had the greater impact.

Data from the National Joint Registry for England and Wales for 2014 indicate that 11,871 metal on metal Pinnacle hips have been implanted, prompting the researchers to calculate that 180,000 people around the world are now walking around with these hips. These patients might be at risk of early revision surgery, they suggest.