Function Assessment for Rheumatoid Thumb Deformity

Objective: Nalebuff’s type I deformity of the rheumatoid thumb, which is the most common thumb deformity with rheumatoid arthritis, can be classified into three stages according to the range of motion of the thumb. However, a functional assessment for each stage has never been undertaken. Methods: The ranges of motion of the thumb metacarpophalangeal and interphalangeal joints were evaluated to determine Nalebuff’s clinical stage, and both the Modified Kapandji Index (MKI) and the simple test for evaluating hand function (STEF) were used to evaluate hand function in 32 rheumatoid arthritis patients with type I deformity. We assessed hand function in each stage, and examined the relationship between the three clinical stages and dysfunction of the hand. Results: The scores for both MKI and STEF were significantly reduced in parallel with advancing stage of thumb deformity. Conclusion: Nalebuff’s staging system is also useful for reflecting the level of thumb function.