Abstract
BackgroundRecent studies suggest that pincer nails are caused by lack of upward mechanical forces on the toe pad. However, clinically significant pincer nails are also often observed among healthy walkers. It was hypothesized that in these cases, the affected toes do not receive adequate physical stimulation from walking and loading. To test this, the gait characteristics of pincer nail cases were assessed by measuring plantar pressure during walking.MethodsIn total, 12 bilateral pincer nail cases (24 affected feet) and 12 age- and sex-controlled healthy control subjects (24 ft) were enrolled in this prospective case–control study. Plantar pressure during free ambulation in both the barefoot and shod state was assessed using a digital pressure-plate system named S-Plate platform (Medicapteurs Co. France). First toe pressure and the frequencies of peak pressure in the first toe, metatarsal head, or other foot areas were calculated.ResultsIn both the barefoot and shod state, the pincer nail group had significantly lower pressure on the first toe than the control group. In both the barefoot and shod state, the peak pressure area was mostly the metatarsal head area in the pincer nail group, whereas it was mostly the first toe area in the control group. Binomial logistic regression analysis revealed that peak pressure area was a significant risk factor for pincer nail development.ConclusionWalking behavior appears to contribute to pincer nail development. Pincer nails of walkers could be treated by correcting the walking behaviour so that more pressure is placed on the toe pad.
Highlights
Recent studies suggest that pincer nails are caused by lack of upward mechanical forces on the toe pad
The Mann-Whitney U test revealed that the pincer nail group had a significantly higher mean first toe nail curve index than the control group (57.9 ± 24.9 % vs. 13.9 ± 5.4 %, p < 0.001)
The Mann-Whitney U test revealed that the pressure on the first toe of the pincer nail group was significantly lower than that of the control group
Summary
Recent studies suggest that pincer nails are caused by lack of upward mechanical forces on the toe pad. Fingernails play a key role in protecting the distal phalanges, enhancing tactile discrimination and performing fine manipulation [1,2,3,4]. Nails are constantly exposed to physical stimuli such as counter pressure and shear force. These mechanical forces may play a marked role in nail configuration and participate in the development of nail deformities. The term pincer nail was introduced by Cornelius and Shellery in 1968 [5] and is defined as a transverse overcurvature of the nail plate Another condition is ingrown nail, which is a painful inflammatory condition caused by a nail edge that has usually been rendered sharp by improper trimming [6].
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