Role of Mechanical Forces in Hand Nail Configuration Asymmetry in Hemiplegia: An Analysis of Four Hundred Thumb Nails

Abstract

Objective: To assess the relationship between nail configuration and mechanical force, the nail morphology and pinch strengths of the paralyzed and non-paralyzed sides of patients with hemiplegia were measured. Methods: Study 1: Analysis of nail configuration. Both thumb nails of 100 subjects with hemiplegia and 100 healthy volunteers (400 thumb nails) were enrolled. The left and right thumb nails were compared in terms of configuration, namely the curve index (defined as nail height/width). Study 2: Measurement of pinch strength. In 10 subjects with hemiplegia and 10 healthy volunteers, the pinch strengths of both sides were compared. Results: Study 1: In the subjects with hemiplegia, the palsy side had a significantly higher curve index than the non-palsy side (32.7 ± 8.3 vs. 24.4 ± 6.5%). The two sides of the healthy volunteers did not differ significantly in terms of the curve index. Study 2: In all hemiplegia cases, the non-palsy side had a higher pinch strength. The differences were statistically significant (4.40 ± 1.90 vs. 0.05 ± 0.16 kg). In the healthy volunteers, the dominant and non-dominant sides did not differ significantly. Conclusion: Mechanical forces may affect the nail configuration and could participate in the pathophysiology of nail deformities.