Reviewed by F. Perry Wilson,
MD, MSCE; Instructor of Medicine, Perelman School of Medicine at the
University of Pennsylvania
Note
that this large cohort study of Canadian recipients of hip or knee replacements
demonstrated higher complication rates among those with rheumatoid arthritis
compared with those with osteoarthritis.
Be
aware that there may be unmeasured confounders that could affect the
interpretation of these results -- for example the degree of immunomodulatory
therapy received by the RA group.
Patients with rheumatoid arthritis
were at higher risk than those with osteoarthritis for adverse outcomes
following joint replacement surgery, a Canadian study found.
After adjustment for potential
confounders, having a diagnosis of rheumatoid arthritis was a significant and
independent predictor of dislocation following total hip arthroplasty, with a
risk almost double that for osteoarthritis (HR 1.91, 95% CI 1.29-2.82, P=0.001),
according to Bheeshma Ravi, MD, of the University of Toronto, and colleagues.
Patients with rheumatoid arthritis
also were at greater risk for developing an infection after total knee
arthroplasty (HR 1.52, 95% CI 1.11-2.09, P=0.03), the researchers
reported online in Arthritis & Rheumatism.
"Over
the last decade, the age-sex standardized rates of total hip arthroplasty and total
knee arthroplasty have increased in North America by approximately 25% and 65%,
respectively," wrote Ravi and colleagues.
These surgeries have been linked with
a risk -- albeit small -- for serious complications including dislocation, infection, venous
thromboembolism, and even death.
However, most data on these
complications have been drawn from the patient population with osteoarthritis,
and little is known about risks for those with rheumatoid arthritis, a much
different disease in its causes, prognosis, and treatment.
The researchers previously conducted
a systematic review and meta-analysis in an effort to fill this knowledge gap,
but were hampered by limitations in many studies such as the possibility of
diagnostic misclassification and lack of adjustment for confounders.
Therefore, they undertook a study in
which they analyzed data from the Canadian
Institute for Health Information Discharge Abstract Database,
identifying patients with a primary elective hip or knee replacement between April 2002 and March 2009.
The diagnosis of rheumatoid arthritis
was confirmed using an algorithm that necessitated hospitalization with a
diagnostic code specifically for rheumatoid arthritis or three physician
claims, at least one being from a specialist such as a rheumatologist or
orthopedic surgeon, within the previous 2 years.
This validated algorithm has a specificity of
100% and a sensitivity of 78%.
The researchers adjusted for patient
age, gender, income, residence, and comorbidities such as congestive heart
failure and diabetes.
They also controlled for frailty,
which has been linked with loss of muscle strength and immune system
abnormalities and therefore could contribute to dislocation and infection.
During the study period, there were
89,713 knee and 60,305 hip arthroplasties performed in Ontario. A total of 3% of the hip
replacements and 4% of the knee surgeries were in patients with rheumatoid
arthritis.
Compared with recipients with osteoarthritis,
those with rheumatoid arthritis were younger, more often women and frail, and
had more comorbidities.
They also were more likely to have
any type of complication following surgery (5.7% versus 4.7%, P=0.01),
but less likely to develop venous thromboembolism (HR 0.35, 95% CI 0.15-0.82, P=0.02).
The lower risk for venous
thromboembolism was unexpected, according to the researchers, and may reflect
selection bias.
Among all patients experiencing a
dislocation within 2 years, the median time to the event was 211 days for
rheumatoid arthritis compared with 263 days for osteoarthritis.
And among those who developed
articular infections, the median time to the event was 196 days for rheumatoid
arthritis compared with 468 days for osteoarthritis.
The
researchers noted that dislocation within a short time of total hip
arthroplasty is a "serious complication."
"In addition to being very
painful and necessitating revision arthroplasty and/or aggressive
rehabilitation following closed reduction, it is estimated that dislocations increase the hospital costs
of a primary total hip arthroplasty by over 300%," they observed.
Possible reasons why patients with
rheumatoid arthritis were more likely to experience this complication were the use of
smaller implants and different surgical techniques, along with
disease-related factors such as acetabular protrusion and soft tissue problems.
Explanations for why infections were more common
in the rheumatoid group included the use of immunomodulatory treatments, but it
wasn't clear why the increased risk was only for knee replacement and not also
for the hip.
Strengths of the study included the
specificity of the algorithm used for diagnosis and large patient population,
while limitations were the lack of information about the specific implants used
and the possibility of unmeasured confounders.
"As both dislocation and
infection lead to significant morbidity and drastically increase healthcare
costs, research is warranted to elucidate explanations for this increased risk
among patients with rheumatoid arthritis. This information will be valuable to inform patient
management decisions, including the development and implementation of
strategies designed to target modifiable risk factors," Ravi and
colleagues concluded.
The study was supported by the
Canadian Institutes of Health Research.
The authors reported no conflicts of
interest.
Primary source: Arthritis & Rheumatism
Source reference: Ravi B, et al
"Patients with rheumatoid arthritis are at increased risk for
complications following total joint arthroplasty" Arthritis Rheum
2013; DOIi: 10.1002/art.38231.
