Establishing a Calculation Method for Estimating the Normal Circumference of the Proximal Interphalangeal Finger Joints

Objective: To estimate the normal circumference of the interphalangeal (IP) thumb joint and the proximal IP (PIP) joints from the index finger to the little finger using individual physical parameters such as body height and body weight. Methods: The maximum size on the ring gauge was recorded which caused resistance when the IP joint of the thumb or PIP joints of the index to small fingers were passed through the gauge. RG was defined as the ring gauge number with the same diameter as the circumference of the IP thumb joint and PIP finger joints from the index finger to the little finger. There were 300 healthy subjects and 600 hands. Univariate and multivariate analyses were used to analyze the relationships between RG and the parameters of age, sex, height, weight, and dominant hand, and regression equations were derived. Results: Age, sex and body weight were all statistically significant predictive factors of RG in all fingers. R2, the coefficient of determination in the regression equation, was almost 0.7 for all fingers, indicating that a moderate or strong correlation was observed between RG and the regression equation. Conclusions: The circumference of the IP thumb joint and PIP finger joints from the index finger to the little finger can be estimated in healthy individuals using a calculation formula that takes age, sex, body height and body weight into account.