Friday June 13 2014
Hip operations are major surgery and are never risk free
"Toxic NHS hip implants blamed for more than 40 deaths," The Daily Telegraph reports. Other media sources similarly report how surgical "cement" used in some hip replacements has been linked to the deaths.
This news is based on a study looking at risk of death or severe harm associated with partial hip replacements involving cement for people with a fracture at the top of the thigh bone (fractured neck of femur).
The practice of using cement to attach the replacement "ball" joint to the "socket" is a clinical decision made by surgeons based on their experience and the patient's characteristics.
In 2009, the National Patient Safety Agency (NPSA) alerted health professionals to the risk of bone cement implantation syndrome (BCIS), which can happen when cement is used.
In BCIS, insertion of cement somehow leads to some fat and bone marrow contents being released into the bloodstream (venous embolisation). This in turn risks blocking the blood flow, potentially causing respiratory and cardiac arrest.
This study looked at the number of cases of BCIS reported between 2005 and 2012. There were 62 cases of death or severe harm caused by BCIS in this period. This is 1 case per every 2,900 partial hip replacements for fractured neck of femur.
Worryingly, three-quarters of these incidents occurred after 2009, suggesting that the precautionary measures regarding use of cement advised by the NPSA had either not been implemented or were not effective.
However, this study is not able to fully appraise the risks and benefits of using cement or not.
Where did the story come from?
The study was carried out by researchers from Imperial College London, including Sir Liam Donaldson, the former chief medical officer.
It is reported to be part of a research programme at Imperial College funded by National Health Service (NHS) England to develop incident reporting in the NHS.
The study has been published in the peer-reviewed medical journal BMJ Open and is open access, so it is freely available to read online.
The Daily Telegraph's headline "Toxic NHS hip implants blamed for more than 40 deaths" has somewhat misfired. It is not the implants themselves that have been called into question, but the cement used to hold them in place. The cement is not made by the NHS, and it is almost certain that similar practices are used in the UK private sector, as well as healthcare systems in other countries.
Once past the headlines, the media is representative of this research, although The Telegraph included a response from NHS England, while The Guardian and The Independent chose to take the researchers' words at face value.
This is not the first time there have been concerns about hip replacements. In 2012, some brands of metal-on-metal hip implants were recalled over safety concerns.
What kind of research was this?
This was a patient safety surveillance study that aimed to estimate the risk of death or severe harm in people undergoing partial hip replacement surgery for a fracture at the top of the thigh bone (fractured neck of femur).
A partial hip replacement (hemiarthroplasty) involves replacing only the top "ball" part of the thigh bone that is fractured, as opposed to a total hip replacement (often carried out because of osteoarthritis, for example), which involves replacing the "socket" part of the joint as well.
Around 75,000 fractures to the neck of femur are said to occur in the UK every year – most are related to osteoporosis. The researchers report that in 2012, 22,000 people in the UK received a partial hip replacement following fracture.
In these operations, cement is often used to hold the replacement metal "ball" in place in the socket, but there is considerable debate about this practice.
An alternative is to not use cement and allow the bone of the socket to gradually mesh with the replacement.
The decision to use cement or not usually comes down to the surgeon's choice and the characteristics of the patient.
In 2009, the National Patient Safety Agency (NPSA) accumulated an increasing number of reports attributing the cement used in partial hip replacements to severe harm and sudden death.
The specific concern – bone cement implantation syndrome (BCIS) – is said to be caused by the cementation process somehow leading to some fat and bone marrow contents being released into the venous bloodstream (venous embolisation).
This in turn can potentially cause blockages in the bloodstream, leading to low blood pressure and respiratory and cardiac arrest. The exact way that cementation may cause this to happen is poorly understood.
The identified clusters of incidents led to guidance being given to health professionals about additional precautions for the use of cement (related to patient assessment, anaesthetic technique and surgical technique). However, as the researchers say, there was no firm direction about whether to use cement or not.
Since the alert, further research studies have looked into the number of incidents reported. The current study examines the number of incidents of BCIS reported to the National Reporting and Learning System (NRLS), a patient safety incident and reporting system set up by the NHS in 2003.
What did the research involve?
The researchers looked for all incidents reported by NHS hospitals in England and Wales between January 2005 and December 2012 where the incident report clearly described severe patient harm associated with cement use in partial hip replacement for fractured neck of femur.
To identify potential cases, the researchers looked for key words in the report text, such as "cement" and "[death during the operation]", "cardiac arrest", "[low blood pressure]", "fat embolus", or "collapse", and words related to orthopedics and hip replacement surgery.
They specifically looked for reports classified as "death", "severe harm" or "moderate harm". The identified incidents were then separately reviewed and verified by two researchers.
The main outcomes the researchers were interested in were the number of reported deaths, cardiac arrests and near cardiac arrests per year. They also looked at the timing of the patient's deterioration and its relation to cement insertion.
They specifically looked at the number of reports that occurred before and after the 2009 NPSA alert on the potential risk of cement was issued.
What were the basic results?
Over the seven-year period, there were 360 identified potential reports, of which 62 were judged by the two reviewers to clearly report severe harm or death specifically associated with the use of cement in partial hip replacement for fractured neck of femur.
Of these 62 incidents:
- two-thirds (41 of 62) were deaths, of which most (33) occurred on the operating table
- 14 involved a cardiac arrest from which the person was resuscitated
- 7 involved near cardiac arrests from which the person recovered
In the majority of cases (55/62, 89%) the person deteriorated during or within a few minutes of cement insertion.
Overall, there was one incident of BCIS for every 2,900 partial hip replacements for fractured neck of femur carried out over the seven-year period. There was a general increase in the number of incidents reported every year between 2005 and 2012. Nearly three times as many incidents were reported after the NPSA alert was issued in 2009 compared with before.
How did the researchers interpret the results?
The researchers conclude that the incident reports identified provide evidence that cement use in partial hip replacement for fractured neck of femur in England and Wales can be associated with death or severe harm as a result of BCIS.
They note that three-quarters of the deaths identified have occurred since the 2009 alert, when the NPSA publicised the issue and encouraged the use of mitigation measures related to patient assessment, anaesthetic technique and surgical techniques.
The researchers suggest that the reports show that there has been incomplete implementation or effectiveness of these mitigation measures.
They go on to say that there is a need for stronger evidence that weighs the risks and benefits of cement in partial hip replacement for fractured neck of femur.
This is valuable research that highlights that there have been 62 cases of severe patient harm or death between 2005 and 2012 as a result of cement use in partial hip replacement for fractured neck of femur resulting in bone cement implantation syndrome (BCIS).
Notably, the 2009 alert by the National Patient Safety Agency (NPSA) on the potential for this risk doesn't appear to have had an effect on decreasing the number of cases. In fact, the number of cases clearly increased year by year over the seven-year study period.
The reason for the apparent ineffectiveness of the alert is not known. The researchers can't say whether the suggested measures related to patient assessment, anaesthetic technique and surgical techniques have not been taken up by professionals, or have just not been effective.
It is also possible that an increased awareness of the risk of BCIS after the NPSA alert led to more serious harms and deaths being reported as potentially associated with cement use.
As the researchers further acknowledge, it could be that the incidence of 1 in every 2,900 partial hip replacements for fractured neck of femur could even be an underestimate, as there may have been a lack of reporting to the National Reporting and Learning System (NRLS) that was used to provide the data for this study.
Also, as the researchers say, this study of reported incidents is not able to fully appraise the benefits and risks of cement use in partial hip replacements, so its findings need to be considered alongside information on the use of cement collected through other sources.
Professor Sir Liam Donaldson, former chief medical officer and a patient safety enthusiast, was involved in this study, and is quoted in The Telegraph as saying: "We want to see this whole question about the use of cement opened up again and further research and evaluation of the risks."
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.