ASSESSMENT OF METACARPOPHALANGEAL ANGLE IN STAGING OF THUMB DEFORMITIES IN RHEUMATOID-ARTHRITIS - A 20-YEAR FOLLOW-UP-STUDY

Objective: To evaluate the development of thumb deformities in long-du ration rheumatoid arthritis (RA). Patients and methods: The thumbs of 83 RA patients with recent (less than or equal to 6 months) disease we re evaluated radiographically in a prospective follow-up study at onse t and at 1, 3, 8 and 15 years from entry and in 68 patients after 20 y ears. The progression of the angle between the first metacarpal and pr oximal phalanx (MCP-I angle), Larsen grades of MCP I and development o f boutonniere and swan-neck deformities were evaluated. Results: A tot al of 39% of thumbs were of the boutonniere type and 30% of the swan-n eck type after the 20-year follow up. At onset the mean MCP-I angle wa s 15.1 degrees on the right hand and 13.8 degrees on the left; the nor mal value for the MCP-I angle was estimated to be 10-20 degrees. A new grading for thumb deformities was developed. The MCP-I angle in grade -1 boutonniere varied from 20-40 degrees and in grade-2 > 40 degrees, while in grade-1 swan-neck it varied from 0-10 degrees and in grade-2 the angles were all negative. Surgical intervention should be consider ed in grade-2 cases. Conclusion: After 20 years 69% of thumbs in RA we re deformed. Development of deformities, their relation to the Larsen grade of MCP-I, and a new grading based on use of the MCP-I angle are discussed.