Influence of mechanical forces as a part of nail configuration

Pincer Nail Deformity: Clinical Characteristics, Causes, and Managements

A pincer nail is a common nail deformity of toenails and is characterized by nail thickening and nail plate deformation. It often causes severe pain for patients. We perform a thorough literature review and an additional review of pertinent clinical cases, aiming to provide a comprehensive review of the etiology, pathogenesis, clinical classification, differential diagnosis, and treatment of pincer nail deformity (PND). Understanding the clinical characteristics and treatment progress of a pincer nail will provide clinicians with comprehensive and evidence-based information about PND, thus allowing the selection of an appropriate treatment according to the patient's request and the clinical manifestations of PND, which should maximize patient satisfaction.

Presence of a family history and excessive pressure on the first toe pad during walking in female subjects with pincer nails

Pincer nails (PN) are defined as a transverse overcurvature of the nail plate. Although there have been advancements in therapeutic approaches, the precise underlying mechanisms for the development of PN are still not fully understood. Currently, PN are assumed to develop due to lack of upward mechanical force on the toes. We developed a novel wireless device to observe detailed gait motion. We analyzed trends of gait motion in healthy individuals without PN, healthy individuals with PN without a family history of PN, and healthy individuals with PN and a family history of PN. We found that a family history of PN is an independent risk factor for PN, irrespective of gait motion. Moreover, healthy individuals with PN but without a family history of PN exhibit strong and concentrated pressure on the first toe pad during walking. In sum, a family history of PN and excess upward mechanical forces on the first toe pad during walking may be risk factors for the development of PN.

Nail Plate and Bed Reconstruction for Pincer Nail Deformity

Pincer nail deformity is a severe condition in which the nail bed becomes compressed and the nail shows an overcurvature. We retrospectively analyzed 13 pincer nail deformities treated using our nail plate and bed reconstruction technique. Visual analogue scale scores, the width of nail root, width of nail tip, height of nail tip, width index, and height index were assessed before and after surgery. The overcurvature was corrected after detachment of the nail plate. The nail fold was pushed underneath the nail plate and then fixed. The width of nail tip significantly increased after surgery (p < 0.05) and was maintained during follow-up. The height of nail tip decreased after surgery (p < 0.05). This nail plate and bed reconstruction technique is a simple and quick surgical method for correcting deformities and reduces risks of complications such as skin necrosis and infection compared to other existing surgical techniques. We recommend this efficient surgical technique for the treatment of pincer nails.

Development of the infant foot as a load bearing structure: study protocol for a longitudinal evaluation (the Small Steps study)

BACKGROUND

An improved understanding of the structural and functional development of the paediatric foot is fundamental to a strong theoretical framework for health professionals and scientists. An infant's transition from sitting, through crawling and cruising, to walking is when the structures and function of the foot must adapt to bearing load. The adaptation of skin and other hard and soft tissue, and foot and gait biomechanics, during this time is poorly understood. This is because data characterising the foot tissue and loading pre-walking onset does not exist. Of the existing kinematic and plantar pressure data, few studies have collected data which reflects the real-life activities of infants with modern equipment.

METHODS

This is a longitudinal study and part of the Great Foundations Initiative, a collaborative project between the University of Brighton and the University of Salford, which is seeking to improve foot health in children. Two cohorts of 50 infants will be recruited at the two sites (University of Brighton, Eastbourne, UK and University of Salford, Salford, UK). Infants will be recruited when they first reach for their feet and attend four laboratory visits at milestones related to foot loading, with experienced independent walking being the final milestone. Data collection will include tissue characteristics (skin thickness, texture, elasticity, pH and tendon thickness and cross-sectional area), plantar pressures and kinematics captured during real world locomotion tasks.

DISCUSSION

This study will provide a database characterising the development of the infant foot as it becomes a weight bearing structure. The data will allow effective comparison and quantification of changes in structure and function due to maturation and loading by measuring pre and post established walking. Additional variables which impact on the development of the foot (gender, ethnicity and body weight) will also be factored into our analysis. This will help us to advance understanding of the determinants of foot development in early childhood.

Foot loading is different in people with and without pincer nails: a case control study

Background

Recent 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.

Methods

In 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.

Results

In 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.

Conclusion

Walking 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.

A novel nonsurgical treatment for pincer nail that involves mechanical force control

We hypothesize that nails have an automatic curvature feature and that their flat shape is maintained by the daily upward mechanical forces from the finger/toe pad. Thus, nail deformities, such as pincer nail, spoon nail, and koilonychias, may be caused by an imbalance between these forces and can be treated by controlling these forces. Here, we report the case of a 55-year-old man whose severe pincer nail was effectively treated by thinning the nail, which reduced the automatic curvature force. This is the first report to show that pincer nail can be treated by a nonsurgical method that reduces the automatic curvature force, thus obviating the need for surgery. This supports the notion that mechanical stimulus–based treatments have high therapeutic potential for nail deformities.

Clinical Evidence for the Relationship between Nail Configuration and Mechanical Forces

Summary:

Mechanobiology is an emerging field of science that focuses on the way physical forces and changes in cell or tissue mechanics contribute to development, physiology, and disease. As nails are always exposed to physical stimulation, mechanical forces may have a particularly pronounced effect on nail configuration and could be involved in the development of nail deformities. However, the role of mechanobiology in nail configuration and deformities has rarely been assessed. This review describes what is currently understood regarding the effect of mechanical force on nail configuration and deformities. On the basis of these observations, we hypothesize that nails have an automatic curvature function that allows them to adapt to the daily upward mechanical forces. Under normal conditions, the upward daily mechanical force and the automatic curvature force are well balanced. However, an imbalance between these 2 forces may cause nail deformation. For example, pincer nails may be caused by the absence of upward mechanical forces or a genetic propensity increase in the automatic curvature force, whereas koilonychias may occur when the upward mechanical force exceeds the automatic curvature force, thereby causing the nail to curve outward. This hypothesis is a new concept that could aid the development of innovative methods to prevent and treat nail deformities.