Influence of mechanical forces as a part of nail configuration

Clinicians encounter pincer nails at a high incidence among bedridden cases who are free from weight bearing. The mechanical force transmitted by walking and loading may affect the nail configuration. This study was aimed at evaluating the influence of mechanical forces on the nail configuration.

Study 1 was conducted on a sample size of 318 great toenails, with the subjects classified into the following 3 groups: healthy volunteers, participants who were bedridden for less than 3 months, and participants who were bedridden for more than 3 months. Study 2 was conducted in 12 subjects with unilateral loading.

The configuration of the great toenails, in terms of the curve index (defined as the nail height/nail width), was compared.

In study 1, the curve index increased significantly as the duration of the bedridden state became longer (17.5 ± 4.75, 28.9 ± 11.0, 36.4 ± 9.58, respectively). In study 2, the curve index on the nonloaded side was significantly higher than that on the loaded side (40.0 ± 8.63 vs. 27.0 ± 8.39).

Our results suggest that mechanical forces may affect the nail configuration and be involved in the pathophysiology of nail deformities.