Assessing damage in individual joints in rheumatoid arthritis: a new method based on the Larsen system

Radiologic patterning of joint damage to the foot in rheumatoid arthritis

OBJECTIVE

Foot and ankle deformities greatly affect the quality of life of rheumatoid arthritis (RA) patients. The aim of this study was to elucidate the pattern of destruction of the RA foot and its impact on patients.

METHODS

We cross-sectionally investigated RA patients (274 patients and 542 feet) using radiographs. The grade of joint destruction was assigned using Larsen's grading system for 12 joints in the foot and ankle. Cluster analysis was performed using the K-means method to classify the pattern of joint destruction. Of the 274 patients evaluated radiographically, 212 were assessed for functional disability using questionnaires.

RESULTS

Cluster analysis revealed that 542 feet were divided into 5 clusters, named according to the characteristic distribution of joint destruction: cluster I (normal type), cluster II (forefoot type), cluster III (midfoot type), cluster IV (mid-hindfoot type), and cluster V (combined type). Radiographic measurements revealed the characteristic deformities of each cluster: splay foot for cluster II, flat foot for cluster III, hindfoot malalignment for cluster IV, and mixtures of these characteristics for cluster V. A distribution map of each cluster based on disease duration revealed that cluster III peaked in cases of 5-10-year disease duration and subsequently decreased, followed by a gradual increase of cluster IV and cluster V. Cluster IV and cluster V showed significant changes in functional disability compared to cluster III.

CONCLUSION

This report is the first to reveal the pattern of RA foot deformities and their impact on patients using statistical measures in a large series.

Asymmetry of small joint involvement in rheumatoid arthritis: prevalence and tendency towards symmetry over time

OBJECTIVES

To quantify asymmetry of radiological joint damage in rheumatoid arthritis (RA), to determine whether asymmetrical damage to joints in RA becomes symmetrical over time, and to identify factors predictive of symmetrization.

METHODS

In phase 1, initial, mid-term (mean follow-up: 3 years) and late (mean follow-up: 8 years) radiographs of 48 patients with definite RA (English population) were graded by the Modified Larsen (ML) system. In phase 2, 27 subjects (Canadian population) with at least one asymmetrical pair of joints in the hands or feet were identified. Two successive radiographs of 77 asymmetrical joints, separated by at least 2 years, were compared. Clinical and biological factors were assessed for their ability to predict symmetrization, defined as a reduction in side-to-side difference over time of two or more ML grades.

RESULTS

In phase 1, the overall rate of asymmetry was 12.9% (95% CI: 11.2-14.5%), increasing from 9.7% (first visit) to 13.8% (mid-term) and 14.4% (last visit). Metacarpophalangeal (MCP) joints were more frequently asymmetrical than thumb (MCP and interphalangeal) joints (P = 0.0064) and proximal interphalangeal (PIP) joints (P < 0.0001); wrist quadrants were more frequently asymmetrical than PIP joints (P < 0.0001). In phase 2, two groups were identified and compared: symmetrizers (22 joints) and non-symmetrizers (55 joints). The overall probability of small joints in the hand and foot symmetrizing was 28.5%. Rheumatoid factor (RF) was predictive of symmetrization. The risk of symmetrization was significantly increased in RF-positive patients with asymmetric joints (P = 0.01). The prevalence of asymmetry did not decrease with disease duration, despite symmetrization.

CONCLUSIONS

Prevalence of asymmetry in joint damage in RA was 13-16%. Symmetry was more evident in PIP joints than in MCP and wrist joints. Seropositive patients are more than twice as likely to symmetrize than seronegative patients. Data regarding the tendency for symmetrization may have value in the clinical management of RA patients with asymmetrical joint damage.