The working space of the hand in rheumatoid arthritis: its impact on disability.

The volumes enclosed by each of 108 hands in 54 rheumatoid arthritis patients were calculated using individual joint measurements. The difference between the flexion and extension volumes is the 'working space' of the hand. Correlations between the working space and parameters of stiffness, pain, deformity, movement, grip and functional disability were performed. The average working space volume was 4921 cc in rheumatoid patients with no visible hand deformity and 1154 cc in the presence of combined finger deformities (P < 0.005). The loss in volume was due mainly to loss of extension. The Patient Evaluation Measure and the Functional Disability Score were significantly related to changes in the working space (P < 0.05). The concept of the working space of the hand may aid the assessment of the rheumatoid hand and help surgical decision-making.