Index-to-ring finger ratio may identify older adults prone to TMCJ osteoarthritis

Radiographic index-to-ring finger ratio (IRFR), particularly metacarpal IRFR, helps predict the susceptibility of older adults to trapeziometacarpal joint (TMCJ) osteoarthritis (OA), suggest a Korea study. In addition, visual IRFR is associated with severe TMCJ OA.

A total of 604 participants (mean age 74.8 years) were included in this population-based study. The authors measured IRFR radiographically using the ratio of the length of the right second to fourth phalangeal bones (phalangeal IRFR) and metacarpal bones (metacarpal IRFR) and classified it as either type 1 (index finger longer than or equal to ring finger) or type 2 (index finger shorter than ring finger).

Logistic regression was used to analyse odds ratios (ORs) for the presence of OA (Kellgren-Lawrence [KL] grade >1) and for severe OA (KL grade >2).

The average phalangeal and metacarpal IRFRs were 91.3 percent and 116.7 percent, respectively. Of the 604 participants, 304 (50.3 percent) had type 2 IRFR. TMCJ OA was diagnosed in 112 participants (18.5 percent) and severe TMCJ OA in 33 (5.5 percent).

The presence of TMCH OA significantly correlated with age (OR, 1.04, 95 percent confidence interval [CI], 1.01‒1.06) and metacarpal IRFR (OR, 0.94, 95 percent CI, 0.88‒0.99). Severe TMCJ OA, on the other hand, was significantly associated with age (OR, 1.08, 95 percent CI, 1.03‒1.12) and type 2 IRFR (OR, 3.07, 95 percent CI, 1.13‒8.33).

“The results of this study suggest that IRFR might serve as an easily measurable biomarker to identify patients vulnerable to TMCJ OA,” the researchers said.