This is a plain English summary of an original research article
Ten years of National Joint Registry data show that many factors may increase the risk of joint infection following hip replacement. Less than 1 in 1,000 people on average needed revision surgery for infection per year.
Several modifiable patient factors increased risk, such as obesity and diabetes. Using ceramic components, and approaching surgery from the back rather than the side of the hip, may slightly reduce infection risk.
This NIHR-funded study analysed registry data for 623,253 hip replacement procedures carried out in England and Wales from 2003 to 2013. The study provides useful quantification of the risk of revision surgery due to infection.
The study highlights some modifiable risk factors that might be addressed preoperatively, such as weight loss, and could support decision-making between clinicians and patients.
Why was this study needed?
Hip replacement surgery is a common procedure, most often recommended for people with hip pain that has not responded to conservative measures and is affecting the quality of life. The National Joint Registry records 96,717 primary hip replacement procedures undertaken publicly or privately in 2017.
Prosthetic joint infection is a serious but rare complication of hip replacement that can cause severe pain, reduced physical function and increased mortality risk. Usually, infection from the surgery is evident within the first 60 days, with a much lower baseline rate which is probably from infection from the bloodstream. Revision surgery is the usual treatment; it can be complex and carries the additional risk of complications.
Existing research into risk factors for infection has had limitations, including inadequate follow-up, small sample sizes and between-study heterogeneity.
This study aimed to review a large number of people over a long time and to differentiate between factors associated with early infection linked to the surgery and those of later onset more likely to result from blood spread.
What did this study do?
This cohort study used data collected by the National Joint Registry to identify primary hip replacements carried out in England and Wales from April 2003 to December 2013. The researchers looked to December 2014 to identify cases where the primary procedure was revised due to prosthetic joint infection.
Patients’ data were linked with Hospital Episode Statistics (England) and the Patient Episode Database (Wales) to identify hospital admissions and co-existing illness, and with the Office for National Statistics to identify deaths. The researchers analysed patient and surgical risk factors for revision/infection, stratified by surgical unit.
Limitations include the potential for missing data and remaining sources of bias.
What did it find?
- During the study period, there were 623,253 hip replacements across 460 different surgical units. Of these, 2,705 (4.3 per 1,000) were subsequently revised due to prosthetic joint infection over 4.6 years on average (interquartile range 2.6 to 7.0).
- Men were at increased risk of infection (1.2 per 1,000 per year) compared with women (0.7 per 1,000 per year; rate ratio [RR] 1.68, 95% credible interval [CI] 1.56 to 1.81).
- Although the absolute risk was less than 2 infections per 1,000 per year in most subgroups, other significant associations were identified; younger age (RR 0.66, 95% CI 0.56 to 0.76), BMI of 30kg/m2 or above (RR 1.92, 95% CI 1.72 to 2.15), diabetes (RR 1.35, 95% CI 1.18 to 1.54), and previous septic arthritis (RR 6.69, 95% CI 4.18 to 9.80).
- Surgery-related risk factors included prior surgery for fractured neck of femur (RR 1.82, 95% CI 1.40 to 2.30) and lateral surgical approach compared with a posterior approach (RR 1.32, 95% CI 1.21 to 1.43). Use of ceramic components reduced infection risk, either ceramic-on-polyethylene (RR 0.82, 95% CI 0.71 to 0.95) or ceramic-on-ceramic (RR 0.76, 95% CI 0.66 to 0.86) compared with use of metal-on-polyethylene.
- There was no clear evidence that health service-related factors were associated with risk of revision due to infection, including the grade of the operating surgeon, consultant presence or the number of procedures the surgeon performed. An isolated health service finding was an increased risk for total hospital volume of more than 406 procedures per year (RR 1.28, 95% CI 1.10 to 1.48).
What does current guidance say on this issue?
NICE guidance on total hip replacement for end-stage arthritis notes that infection is one of several causes of surgical revision, which can be more complex and carry greater risks than primary hip replacement. NICE does not recommend a specific choice of prosthesis, aside from advising that the expected revision rate should be less than 5% at 10 years. They also warn that metal-on-metal replacements may be associated with soft tissue damage.
NICE osteoarthritis guidelines state that “Patient-specific factors (including age, sex, smoking, obesity and comorbidities) should not be barriers to referral for joint surgery.” They state that risks and benefits of surgery should be communicated.
What are the implications?
This study provides real-world data exploring the risk factors for prosthetic joint infection from the patient, surgical and healthcare system perspective. Some modifiable risk factors, such as increased BMI and use of metal replacement components, are well known but this study provides useful quantification of the potential size of the risk.
There are inherent limitations when using registry data, such as incomplete recording of complications, illnesses and patient characteristics. Patients can be reassured about the low risk of joint infection less than 2 in 1,000 people per year. The findings may aid discussions with patients preparing for surgery and clinical decision-making in selecting the most appropriate approach according to patient risk factors.
Citation and Funding
Lenguerrand E, Whitehouse MR, Beswick AD et al. Risk factors associated with revision for prosthetic joint infection after hip replacement: a prospective observational cohort study. Lancet Infect Dis. 2018;18(9):1004-14.
This project was funded by the National Institute for Health Research Programme Grants for Applied Research programme (project number RP-PG-1210–12005).
NICE. Osteoarthritis: care and management. CG177. London: National Institute for Health and Care Excellence; 2014.
NICE. Rheumatoid arthritis in adults: management. NG100. London: National Institute for Health and Care Excellence; 2018.
NICE. Total hip replacement and resurfacing arthroplasty for end-stage arthritis of the hip. TA304. London: National Institute for Health and Care Excellence; 2014.
NJR. National Joint Registry of England, Wales, Northern Ireland and the Isle of Man. Hemel Hempstead: National Joint Registry.
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