Background/Purpose: The Disease Activity Score including 28 joints (DAS28), the Simplified Disease Activity Index (SDAI) and the Clinical Disease Activity Index (CDAI) were developed in order to provide a quantifiable measure of rheumatoid arthritis (RA) activity. Although inflamed hip joints greatly impact activities of daily living (ADL) and walking ability, the hip joint was not included in the DAS28, SDAI or CDAI assessments. This study aimed to assess the correlation between a hip score and disease activity in patients with RA after THA.

Methods: We analyzed the effect of RA disease activity on a hip function score in an observational cohort of RA patients after THA. Thirty-three registered RA patients who had undergone THA (44 joints) between 1997 and 2016 and who had been followed for more than 1 year were included. Hip function was recorded and RA disease activity was measured on the same day. The mean age of the patients was 66.8 years (range, 41–84 years). They were followed for a mean of 7.9 years (range, 1–19) after surgery. The Japanese Orthopedic Association (JOA) hip score was used as a clinical outcome measure for hip dysfunction. The JOA hip score accounts for: ‘pain’ (up to 40 points), ‘range of motion’, ‘ability to walk’, and ‘activities of daily living (ADL)’ (each up to 20 points), such that a higher score indicates less pathology. The mean duration of disease following RA diagnosis for this patient group was 22.9 years (range 2–47 years). The RA disease progression was assessed by Steinbrocker radiographic stages, 9 patients (11 THA) were in stage II, 4 patients (7 THA) were in stage III, and 20 patients (26 THA) were in stage IV. More than half of the studied patients had advanced to Steinbrocker radiographic stage IV. RA disease activity were measured using the DAS28, SDAI and CDAI. RA functional assessment was measured using the modified health assessment questionnaire (mHAQ).

Results:

The mean JOA score for hip function was 83.8 (range, 39–99) at the final follow-up. The mean DAS28-ESR, DAS28-CRP, SDAI, CDAI and mHAQ measuring RA disease activity levels were 3.87 (range, 0.77–6.04), 2.39 (range, 1.03–5.21), 8.89 (range, 0.23–27.33) and 7.67 (range, 0.1–23.90), respectively, at the final follow-up. There was a significant negative correlation between the JOA hip score and all disease activity assessments observed after THA (DAS-ESR [P = 0.0012]; DAS-CRP [P = 0.0036]), SDAI [P = 0.0023], CDAI [P = 0.0016] and mHAQ [P < 0.0001]). There were significant JOA score changes among the parameters of ADL (DAS-ESR [P = 0.0081]; DAS-CRP [P = 0.0245]), SDAI [P = 0.0116] and CDAI [P = 0.0187] and mHAQ [P < 0.0001]) and the ability to walk (DAS-ESR [P = 0.0012], DAS-CRP [P = 0.0011], SDAI [P = 0.0011, CDAI [P = 0.0007] and mHAQ [P < 0.0001]). Thus, ADL and ability to walk are correlated with RA disease activity.

Conclusion: We found significant negative correlations between JOA hip scores and all disease activity assessments in RA patients treated with THA. We conclude that THA may have a positive secondary systemic effect on RA disease activity, and tight control of RA disease activity may improve hip function for RA patients after THA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/correlation-between-disease-activity-and-hip-score-in-patients-with-rheumatoid-arthritis-after-total-hip-arthroplasty/