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Pre-operative synovitis assessments predict TKR outcomes
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CHICAGO — Patients with knee osteoarthritis who had higher volumes of effusion-synovitis and moderate-to-severe Hoffa-synovitis before undergoing total knee replacement surgery experienced significantly greater reductions in pain up to 2 years after the procedure, according to research presented at the ACR/ARHP 2018 Annual Meeting.
In addition, Manjinder Kaur, DO, first-year rheumatology fellow at the University of Arizona College of Medicine, reported that patients with little or no effusion-synovitis, as well as those with normal or mild Hoffa-synovitis, were less likely to have any clinically important improvement in pain after total knee replacement (TKR). Together, the findings suggest that pre-operative effusion-synovitis and Hoffa-synovitis assessments may serve as predictive biomarkers of pain reduction following TKR.
According to Kaur, more than 600,000 TKRs are performed in the United States each year. Despite being a cost-effective treatment for end-stage OA, 20% to 33% of patients who undergo TKR do not experience improvements in knee pain or function.
Previous research has shown that the presence of structural joint abnormalities on knee MRIs is associated with knee pain and an increased risk for knee replacement.
“There is increasing evidence that inflammation, particularly synovitis, plays a role in the pathogenic process of OA,” Kaur said. “However, the relationship between the presence of knee inflammation on MRI prior to knee replacement and experience of clinically important pain reduction after knee replacement is unknown.”
To further investigate the association between MRI-detected knee inflammation and TKR outcomes, Kaur and colleagues compared reductions in WOMAC pain scores and numerical rating scale (NRS) pain scores among patients with varying levels of effusion-synovitis and Hoffa-synovitis, which Kaur defined as hyperintensity within the intercondylar region of the Hoffa fat pad. Pain scores were estimated before patients underwent TKR and 2 years later. The analyses were adjusted for age, sex, race and BMI.
The study included 156 patients from the Osteoarthritis Initiative. Most patients (62.2%) had medium-to-large effusion synovitis, but only 37.2% had moderate-to-severe Hoffa-synovitis. Overall, 70.5% of patients had medium-to-large effusion-synovitis and/or moderate-to-severe Hoffa-synovitis.
Pain scores before, after TKR
Before TKR, participants with medium-to-large effusion-synovitis reported higher levels of pain. Their average WOMAC score was 7.9 (95% CI, 7.1-8.6) vs. 6.3 (95% CI, 5.3-7.3) among participants with little or no effusion-synovitis. Two years after TKR, pain levels were similar across effusion-synovitis groups. However, because participants with medium-to-large effusion-synovitis had greater WOMAC scores at baseline, they experienced a significantly greater reduction in pain: 6.7 (95% CI, 5.5-7.9) vs. 4.0 (95% CI, 2.8-5.3) among participants with little or no effusion-synovitis (2.7 difference; 95% CI, 1.3-4.1). Analyses using NRS pain scores yielded similar results. The average reduction in pain was 5.2 (95% CI, 4.3-6.0) among patients with greater effusion-synovitis vs. 3.9 (95% CI, 3.0-4.7) among those with little or no effusion-synovitis (1.3 difference; 95% CI, 0.4-2.2).
A combined analysis including effusion-synovitis and Hoffa-synovitis further showed that patients with greater and more severe synovitis had higher reductions in WOMAC pain scores (6.3; 95% CI, 5.1-7.5 vs. 4.0; 95% CI, 2.6-5.3; difference of 2.3; 95% CI, 0.8-3.8) and NRS pain scores (5.1; 95% CI, 4.3-5.9 vs. 3.7; 95% CI, 2.8-4.6; difference of 1.4; 95% CI, 0.5-2.4).
Proportion of patients with no pain reduction
When looking at effusion-synovitis alone, 28.8% of participants with little or no effusion-synovitis had no clinically important improvement in WOMAC pain scores 2 years after TKR vs. 13.4% with medium or large effusion-synovitis (adjusted OR = 2.98; 95% CI, 1.26-7.04). Similarly, 27.1% of participants with little or no effusion-synovitis had no clinically important improvement in NRS pain scores vs. 10.3% of participants with medium or large effusion-synovitis (aOR = 4.35; 95% CI, 1.69-11.23).
When combining effusion-synovitis and Hoffa-synovitis, 30.4% of patients with little or no effusion-synovitis and normal or mild Hoffa-synovitis had no clinically important improvement after TKR vs. 14.5% of patients with greater effusion-synovitis and moderate-to-severe Hoffa-synovitis (aOR = 2.62; 95% CI, 1.10-6.28). Results were similar for NRS (30.4% vs. 10.9%; aOR = 3.99; 95% CI, 1.55-10.26).
Additional biomarkers needed
Kaur noted several limitations of the study, including the lack of data on knee replacement indications and information on whether synovium or Hoffa’s fat pad were removed during knee replacement.
Because about 70% of patients with little or no effusion-synovitis and normal-to-mild Hoffa-synovitis still reported pain reduction after TKR, Kaur warned that additional biomarkers may be needed to identify patients who will not likely benefit from the procedure. She said there are future plans to evaluate the impact of other structural abnormalities, such as cartilage and bone marrow edema, on pain reduction following TKR.
“Pre-operative assessment of effusion-synovitis and Hoffa-synovitis may identify participants at increased risk for no pain improvement, and potentially in combination with other MRI-detected structural abnormalities, may serve as predictive biomarkers of pain reduction following TKR,” she concluded. – by Stephanie Viguers
Reference:
Kaur M, et al. Abstract 953. Presented at: ACR/ARHP Annual Meeting, Oct. 20-24, 2018; Chicago.
Disclosure: Kaur reports no relevant financial disclosures. Please see the abstract for a list of all other authors’ relevant financial disclosures.