POS0617 SYNOVITIS OF THE FIRST METACARPOPHALANGEAL JOINT HAS A MAJOR IMPACT ON GRIP FORCE IN EARLY RHEUMATOID ARTHRITIS

Abstract

BackgroundRheumatoid arthritis (RA) has a major impact on hand function in many patients. Information on the contribution of individual joints to impaired grip strength may be helpful for guiding individualized management.ObjectivesThe objective of this study was to investigate the relation between swelling and tenderness of individual finger joints and grip force in patients with early RA.MethodsAn inception cohort of patients with early RA (symptom duration ≤12 months), recruited in 1995-2005, was investigated and followed in a structured program, with follow-up evaluations after 1 and 5 years. All patients were examined by the same rheumatologist according to a structured protocol. Grip force (Newton) was measured using the electronic instrument Grippit (AB Detektor, Gothenburg, Sweden). Average grip force values of each hand were evaluated and compared to the expected, based on age- and sex-specific reference values from the literature (1). Grip force was expressed as % of expected values. Linear regression analyses were used to assess the relation between involvement of individual finger joints and grip force. Synovitis and joint tenderness were assessed in separate models. As wrist involvement, high erythrocyte sedimentation rate (ESR) and severe patient reported pain have been independently associated with reduced grip force in early RA (2), the analyses were adjusted for these covariates.ResultsA total of 215 patients with early RA (71 % women; mean age 60 years) were investigated. The median symptom duration at inclusion was 7 months; interquartile range 5-10. In the right hand, synovitis of the first metacarpophalangeal (MCP) joint was consistently associated with reduced grip force at all evaluations (Table 1). Patients with MCP II and MCP III synovitis also had reduced grip force at inclusion, but not after 1 and 5 years. Proximal interphalangeal (PIP) joint swelling (Table 1), and tenderness of MCP or PIP joints, had a lower impact on grip force. Results were largely similar for the left hand.Table 1.Relation between synovitis of individual MCP and PIP joints and grip force of the right hand (% of expected) in patients with early RA; β (95 % CI), adjusted for wrist synovitis, ESR and VAS painInclusion1-year follow-up5-year follow-upMCP I-10.8 (-17.1 to -4.4)-8.0 (-14.8 to -1.2)-8.2 (-16.4 to 0)MCP II-7.5 (-13.9 to -1.1)-0.6 (-7.6 to 6.4)-0.6 (-8.2 to 9.5)MCP III-7.4 (-13.5 to -1.3)-1.3 (-9.4 to 6.8)-4.5 (-13.4 to 4.5)MCP IV-8.9 (-18.5 to 0.7)-8.8 (-25.7 to 8.1)-4.0 (-22.1 to 14.0)MCP V-2.5 (-12.6 to 7.6)-2.6 (-16.5 to 11.2)7.4 (-5.2 to 20.0)IP I2.0 (-6.4 to 10.9)-1.6 (-14.0 to 10.7)-5.1 (-23.3 to 13.2)PIP II-0.8 (-7.7 to 6.2)-3.9 (-13.3 to 5.5)-3.2 (-16.2 to 9.8)PIP III-5.6 (-12.1 to 1.0)2.5 (-6.5 to 11.6)1.9 (-9.0 to 12.9)PIP IV-4.1 (-11.8 to 3.6)-1.9 (-12.8 to 9.0)-0.1 (-14.2 to 14.1)PIP V-7.2 (-16.0 to 1.7)-10.3 (-22.8 to 2.3)-5.6 (-21.2 to 9.9)ConclusionMCP I synovitis is a major contributor to reduced grip force in patients with early RA during the first 5 years after diagnosis, independent of wrist synovitis, general pain and systemic inflammation. This underlines the importance of involvement of the thumb for impaired hand function in RA.