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Dermatologic ultrasound has grown exponentially during the last decades and has passed from the experimental phase to the routine daily practice in multiple countries. The performance of this imaging technique requires color Doppler ultrasound devices working with high-frequency probes, a trained operator on imaging and dermatologic conditions, and the performance of standardized protocols for obtaining the anatomical data properly. In this review, we analyze the ultrasonographic anatomy of the skin, hair, and nails, the technical requirements and considerations, the guidelines, and the recommended protocols, and provide the best tips for practicing this type of examination confidently., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Knowledge of nail anatomy is a prerequisite for both diagnostic and therapeutic purposes. The nail apparatus is a highly specialized structure, but is in close relationship to the distal phalanx which supports it and to the pulp which carries the sensory receptors and is involved in pinching. It can be divided by the nail plate into the perionychium underneath, and the paronychium above. The perionychium includes, from proximal to distal: the nail matrix, the sole structure responsible for the growth of the nail plate; the nail bed, mostly responsible for adhesion of the plate; and the hyponychium, which is the most distal part, where the nail plate loses its adhesion. The paronychium comprises three nail folds, one proximal and two lateral, that embed the nail plate. The nail apparatus is richly vascularized, with three main sources, and richly innervated, which explains why trauma and surgery are so painful., (Copyright © 2024 SFCM. Published by Elsevier Masson SAS. All rights reserved.)

Background: Nowadays, nail care products are extremely important both in medical and cosmetic fields. Actually, there are only a very few "in vivo" methods to evaluate the safety and the efficacy of nail products., Methods: The new apparatus, based on a recently patented technology, is developed for the "in vivo" evaluation of nails in terms of thickness, structural firmness, flattening, and bending properties. The device analyzes nails by an "in vivo" non-invasive methodology in a timely way and with high accuracy. The assessment of the resistance to compression measures the cohesion of the nail matrix (nail firmness), while the evaluation of the resistance to transversal deformation detects the elasticity of the nail plate. Furthermore, the apparatus is able to assess the nail thickness and the flexibility of their distal edge., Results: The instrument provides nail thickness and several parameters reflecting mechanical properties of nail plate: Viscoelasticity expressed as viscoelasticity index (VI), structural strength/ firmness expressed as Firmness Index (FI), and viscoelasticity of the distal edge expressed as Bending Index (BI)., Conclusions: The instruments described in this work represent an innovative apparatus for the safety and efficacy evaluation of nail products in several fields: cosmetics, pharmaceuticals, and medical devices., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Common foot and toenail problems may cause diagnostic and management difficulties and are often complicated by comorbid factors., Objective: The aim of this article is to discuss common disorders of the skin and nails of the feet, regional physiological factors to consider and appropriate investigations and management., Discussion: Cutaneous disorders of the feet and nails present significant diagnostic and management challenges given the considerable overlap of common signs and symptoms and regionally difficult management.

Background: Concerns have been raised over the integrity of gloves and the longevity of their protective barrier function., Aims: This study aimed to assess the effect of clinicians' fingernail length as a predisposing factor for perforation of latex gloves., Methods: We assessed 2006 latex examination gloves for perforations using the water inflation method after being used by 6 senior dental students who had fingernail lengths ranging from 0 to 3 mm. Four simulated clinical procedures representing a variety of hand movements were used for this purpose and were repeated 30 times, followed by a water leakage assessment test. Data were analysed using the χ 2 test, analysis of variance and logistic regression., Results: Leakage was detected in 222 (11.1%) gloves, and was most frequent with longer fingernails (odds ratio =1.431, 95% confidence interval 1.249-1.640; P < 0.001). This was independent from the simulated clinical procedure. Most perforations were over the index fingers and thumbs (63.5% and 24.3%, respectively; P < 0.001). The simulated procedures with most perforations were wiping the scaler tip with gauze (20.8%) and placing the chamfer bur (15.3%). The procedure with the fewest perforations was placing the triple way syringe (3.5%)., Conclusion: The length of the clinicians' fingernails significantly compromises the integrity of latex gloves. Maintaining short fingernails is important in reducing the risk of damaging latex gloves intraoperatively, and hence maintaining the barrier function of the gloves., (Copyright © World Health Organization (WHO) 2019. Some rights reserved. This work is available under the CC BY-NC-SA 3.0 IGO license (https://creativecommons.org/licenses/by-nc-sa/3.0/igo).)

Purpose: During fracture fixation, the size of tibial nail is a vital factor affecting the outcomes and thus preoperative estimation of tibial nail length is very important. This study aims to find out whether "olecranon to 5th metacarpal head" (O-MH) measurement can be used to reliably predict the tibial nail length., Methods: This was a cross sectional study involving 100 volunteers. Measurements were done and recorded by two observers on two separate occasions. Tibial nail length estimation measurement was done from highest point of tibial tuberosity to the tip of the medial malleolus (TT-MM). O-MH measurement was taken from tip of olecranon to the tip of 5th metacarpal head with wrist in neutral position and hand clenched. Statistical analysis was done to find out correlation between two measurements and influence of age, gender and body mass index on them., Results: Paired t-test showed no systematic error between the readings. Intraclass correlation coefficient showed strong agreement in inter and intra observer settings. Strong correlation was found between the TT-MM & O-MH measurements using Pearson's correlation coefficient test (r = 0.966). Hierarchical regression analysis showed age, gender and BMI have no statistically significant bearings on these measurements and their correlations., Conclusion: O-MH measurement is a useful and accurate means of estimating tibial nail length preoperatively., (Copyright © 2019. Production and hosting by Elsevier B.V.)

The concept of the nail unit as a musculoskeletal appendage has become popular in the dermatological and rheumatological literature. However, an exact knowledge of the characteristics of mesenchyme surrounding the nail such as the composition of the collagen and elastic fibers and their arrangement is fundamental before one can propose a constitutive model. To the best of my knowledge, there is no study in the literature concerning the elastic network of the ligamentous connective tissue of the base of the distal phalanx. This study by means of elastic stains demonstrates that the so-called superficial, deep, and lateral laminae of the extensor tendon correspond to 3 different microanatomic structures: the nail dermis and its fibrous root, the subcutaneous proximal nail fold, and the periosteum. The complex fascial and adipose connective tissue of the proximal nail fold surrounds the matrical dermis and could viewed as a kind of suspensory system for the proximal nail unit. Such suspensory system protects the nail matrix epithelium from the biomechanical strain of the extensor mechanism. Near the ulnar and radial edge of the base of the phalanx, focal interconnections between the fibrous root of the apex of the matrix and the periosteum through a fascia-like structure are visible. In its most lateral zone, the matrical horns lie on a thick dermis connected to the interosseous ligament. Such lateral laminar system serves as anchoring ropes for the vault of the nail plate. The nail-extensor enthesitis theory relies on an oversimplified anatomy because the nail unit is an epidermal appendage with a specialized connection with the lateral periosteum, but not a musculoskeletal appendage. Finally, I would like to emphasize, the practical importance of recognizing the matrical hypoderm. In nail surgery, the interface between the matrical nail dermis and its submatrical loose connective tissue is potentially a new, relatively superficial, surgical cleaving plane, beside the classical deep surgical procedure usually extending to the periosteum. Recognition of this additional cleaving plane leads to an optimal nail tangential biopsy.

Nail conditions are routinely encountered in dermatology clinical practice. Nails have important aesthetic functions, and onychodystrophies may cause pain and difficulties with ambulation and performing activities of daily living. Ideally, accurate diagnosis and optimal treatment of nail disorders are taught as early as medical school and extend into dermatology residency. We sought to determine the integration and content of nail education in the American Academy of Dermatology (AAD) Basic Dermatology Curriculum. Our results showed a paucity of nail content in this medical curriculum with only 101 total mentions of nails in 12 modules. Nail examinations were not mentioned as part of the full-body skin examination, nail unit melanoma was inadequately covered, and nail biopsy techniques were completely omitted. There is a notable need to enrich this curriculum with relevant nail content to educate students about the importance of nail disease.

Pregnancy causes some physiological skin changes, such as hyperpigmentation and striae gravidarum. Thickening of scalp hair and a prolonged anagen phase are also known to occur during pregnancy. However, a limited number of studies have been conducted on the effect of pregnancy on the nails. We aimed to investigate the effect of pregnancy on the morphology of the nail plate, specifically its growth rate and thickness. Pregnant women and a control group consisting of healthy female volunteers were included in the study. The distance from the apical point of the lunula to the midpoint of the free edge of the nail plate of the the thumb was measured with digital calipers. The measurement was repeated during the control visits and recorded in millimeters per day. The thickness of the nail plate of the thumb was measured at the midpoint of the free edge of the nail plate. A dermatological examination of the fingernails was performed for both groups. A survey was also conducted to identify any changes that occurred in the nails during pregnancy. The mean growth rate of the nail plate in pregnant women was 0.1 ± 0.05 mm/day, and in the control group it was 0.09 ± 0.05 mm/day. There was no statistically significant difference between the pregnant and control groups regarding the growth rate of the nail plate (P = 0.438). The mean thickness of the nail plate in pregnant women was 0.87 ± 0.19 mm, and in the control group it was 0.75 ± 0.17 mm. There was a statistically significant difference between the groups with respect to nail plate thickness (P < 0.001). A dermatological examination of the fingernails in the two groups did not reveal any statistically significant differences with respect to the nail findings. We determined in our study that pregnancy did not affect the growth rate and the morphology of the nails but increased the thickness of the nail plates., (© 2018 The International Society of Dermatology.)

Background: Wounds of the finger nail bed represent a frequent injury, especially in children. Residents often learn nail bed repair on patients without prior training. We aimed to develop and evaluate a "low-fidelity" simulation model of nail bed repair., Methods: The model consists of a false nail on a plastic finger and a hydrocolloid dressing, which is pasted on the nail bed site and cut horizontally. This model allows nail bed suture and nail fixation. The cost of each model is about $1. Thirty-three doctors evaluated this model on 10 items, rated out of five, concerning the realism, the difficulty of the procedure, and the educational value. The duration of the procedure was also noted. We evaluated the clinical effectiveness by comparing through Fisher's exact test the ratio of unsuitable events (revision surgeries, surgical site infections, and complaint letters) on two periods-3 y before and 18 mo after the implementation of this model in our institution, respectively., Results: Average mark was 4.16/5. The model was considered reliable, reproducible, and realistic. All the testers recognized a big educational value. The overall duration of the procedure averaged 23 min for residents and 11 min for surgeons. We collected 17 unsuitable events out of 84 patients from the period "before" and 2 out of 54 patients from the period "after" (P = 0.005). Revision surgeries were 10/84 from the period before and 2/54 from the period after (P = 0.04)., Conclusions: The results of the internal and clinical evaluations are encouraging. We suggest integration of this model into the training program of residents., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Nail clipping specimens are commonly submitted for the microscopic evaluation of nail disease; however, there may be missing clinical history regarding nail polish or other adornments present on the nail at the time of specimen retrieval. For this study, 6 types of nail cosmetics were chosen and applied to the nail plate of a volunteer. After a period of at least 24 hours, the nail plates with adornments and a control nail plate were clipped and placed in formalin. Specimens were processed using a standard nail protocol. All of the specimens, except the sticker appliqué, survived the fixation process. The glitter nail polish was the only specimen found to be polarizable. None of the specimens that survived fixation were found to be PAS-positive. Cosmetic nail enhancements are easily differentiated from the nail plate microscopically; nail cosmetics appear as a distinct layer of inorganic material lying atop the nail plate. There were 2 main microscopic patterns noted on the specimens: those with 2 layers and those with 3 layers.

Onychomycosis is a fungal infection of the fingernails or toenails caused by dermatophytes, nondermatophytes, moulds, and yeasts. This condition affects around 10-30% people worldwide, negatively influencing patients' quality of life, with severe outcomes in some cases. Since the nail unit acts as a barrier to exogenous substances, its physiological features hampers drug penetration, turning the onychomycosis treatment a challenge. Currently, there are several oral and topical therapies available; nevertheless, cure rates are still low and relapse rates achieves 10-53%. Also, serious side effects may be developed due to long-term treatment. In light of these facts, researchers have focused on improving topical treatments, either by modifying the vehicle or by using some physical technique to improve drug delivery trough the nail plate, hence increasing therapy effectiveness. Therefore, the aim of this paper is to explain these novel alternative approaches. First, the challenges for drug ungual penetration are presented. Then, the chemical and physical strategies developed for overcoming the barriers for drug penetration are discussed. We hope that the information gathered may be useful for the development of safer and more effective treatments for onychomycosis., (© The Author 2016. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Introduction: The nails have a functional and esthetic importance for patients. Almost always, the nail disorders are diagnosed on the basis of clinical findings, but imaging methods may be required for a better assessment. These imaging methods, such as ultrasound and magnetic resonance, may help to establish an accurate diagnosis. Magnetic resonance imaging is not widely available and sometimes may be very expensive; that is why, ultrasound is an excellent imaging modality. Our objective is to expose the nail unit anatomy, the nail unit anatomy in ultrasound, and some of the frequent pathologies found in our daily practice., Methods: A review of the literature was done to review the anatomy, technical aspects, and different findings in normal and abnormal nail unit ultrasound., Results: Ultrasound offers an appropriate alternative for the evaluation of the nail unit, allows a real-time evaluation of each one of the components of the nail unit with an optimal visualization of these structures, and allows the evaluation of the thickness of the components, the vascularity, and blood flow by Doppler application. In addition, the nail unit disorder, such as infectious diseases, inflammatory and rheumatologic conditions, nail tumors, among others, may be assessed, not only in the diagnosis but also in the follow-up. Pre-surgical evaluation, surgical follow-up, and some procedures, such as biopsies, may be done by this technique., Conclusions: Ultrasound is an excellent technique for evaluation of normal anatomy, diagnosis, and follow-up of patients with nail unit diseases. This is an alternative for other imaging methods and may be used for an accurate diagnosis approach.

Nail neoplasms include all tumors occurring in the nail or periungual apparatus tissue. While some nail tumors can be similar to tumors located on the skin, others are unique. Both benign and malignant lesions can affect the nail apparatus. In particular, early malignant tumors like melanoma and squamous cell carcinoma can present similarly to onychomycosis or benign melanonychia and frequently missed by clinicians. Therefore, physicians should be aware of nail structures and the characteristics of nail tumors. Our review covers the normal nail structure and the most common nail tumors from benign to malignant., (© 2017 Japanese Dermatological Association.)

Recent development of ultra high-resolution ultrasound systems, with frequencies as high as 70 MHz and capability resolution as fine as 30 μm, could permit new diagnostic applications to small parts. A variety of superficial targets within the first 1 cm of the skin surface could be imaged, including dermatological applications such as assessment of skin layers, hair follicles and the nail unit. Nail disorders are frequent but they are diagnosed mainly based on clinical examination; although biopsies and scrapings can provide clinically significant information, most patients do not perceive biopsies positively. To image the skin layer and annexes is often difficult with conventional ultrasound but, because of anatomical details obtained with the newest systems, this method holds great promise for addressing important biomedical applications offering unique advantages over the existing non-invasive imaging modalities. This will enable physicians to assess and manage the conditions involving the nails of a large and growing segment of the population in a better way., (© 2016 Japanese Dermatological Association.)

Expert diagnosis of cutaneous pathology requires precise anatomic description. In this brief report the authors review the clinically relevant surface anatomy of the nail and relate it to a case of squamous cell carcinoma., (© The Author(s) 2016.)

Fingertip injuries with nail bed trauma can require specialist hand surgery, depending on severity. However, most of these injuries can be managed in well-equipped emergency departments by emergency nurses with an in-depth knowledge and understanding of the anatomy and physiology of the fingernail and surrounding structures, assessment and examination, pain management and treatment. This article describes the surface and underlying anatomy and physiology of the nail, the most common mechanisms of injury, relevant diagnostic investigations, and initial assessment and management. It also discusses treatment options, referral pathways, and patient discharge advice.

Consumer perception of longitudinal striations of the nail is one of the drivers of nail cosmetic purchase and use. The following work investigates the use of objective instrumental methods for the characterization of longitudinal striations. Striations are quantified by Ra (the average maximum height of the profile), Rq (the root mean square average of the roughness profile), and Rz (the mean roughness depth), industrial roughness parameters, which are calculated using optical profilometry of the three-dimensional surface structure of the nail. A visual assessment is conducted by cosmetologists in vivo and on images captured in several lighting conditions. With this evaluation, the cosmetologists provide ratings of surface ridges on a 0–5 scale to complement and validate the instrumental method. Both the optical profilometry and the cosmetologist-graded methods are used to evaluate 33 nails of visually-varying levels of ridges from female volunteers. The evaluations from these methods yield well-correlated and repeatable results, and these preliminary findings suggest that this new instrumental method can be used to objectively measure longitudinal striations of the nail.

This article reviewed some of the more common diseases of the skin appendages that are encountered in medicine: hyperhidrosis, acne, AA, FPHL, AGA, and TE. The pathophysiology behind the conditions and their treatments were discussed so that the clinician can make logical therapeutic choices for their affected patients., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: The purpose of this study was to delineate the relationship of the terminal extensor hallucis longus tendon insertion to the proximal limit of the nail matrix of the great toe., Material and Methods: Fifty fresh-frozen human cadaver great toes with no evidence of trauma (average age, 62.5 years; 29 males and 21 females) were used for this study. Under 25X magnification, the proximal limit of the nail matrix and the terminal bony insertion of the extensor hallucis longus tendons were identified. The distance from the terminal tendon insertion to the nail matrix was ascertained using precision calipers, an optical microscope, and autocad(®) software for windows. Twenty-five great toes were placed in a neutral formalin solution and further analysed by histological longitudinal-sections. The specimens were stained with haematoxylin and eosin and examined microscopically to determine the presence of the extensor hallucis longus tendon along the dorsal aspect of the distal phalanx of each great toe., Results: The main result we found in great toes was that the extensor tendon is between the matrix and the phalanx and extends dorsally to the distal aspect of the distal phalanx in all, 100%, specimens. The nail matrix of the great toe is not attached to the periosteum of the dorsal aspect of the base of the distal phalanx as is the case for fingers, because the extensor hallucis tendon is plantar or directly underneath the nail matrix and the tendon is dorsal to the bone., Conclusions: We have found that the extensor tendon is between the matrix and the phalanx and extends dorsally to the distal aspect of the distal phalanx. The nail matrix of the great toe is not attached to the periosteum of the dorsal aspect of the base of distal phalanx as is the case in fingers, because the extensor hallucis tendon is plantar or directly underneath the nail matrix and the tendon is dorsal to the bone. Our anatomic study demonstrates that the proximal limit of the matrix and nail bed of the human great toe are dorsal and overlapping the terminal extensor hallucis longus tendon until its distal bony insertion in all specimens., (© 2015 European Academy of Dermatology and Venereology.)

The nail is a highly keratinized structure covering the tip of the digit, and considered to have several important functions in our daily life. In recent years, as biological aspects of the nail organ have been characterized, we realize that the nail unit and the hair follicle share various biological and immunological features. In particular, development and homeostasis of the nail unit also requires intimate epithelial-mesenchymal interactions that involve signaling pathways such as Wnt. There is also a striking immunological resemblance between both appendages, since the nail matrix, like the anagen hair bulb and the bulge, was shown to present unique characteristics of an immune privileged site. On the other hand, considerable progress in identifying nail stem cells has succeeded in locating putative stem cell niches in the nail unit. In this context, it is intriguing that nail stem cells residing in the nail matrix were recently shown to possess the ability to organize the process leading to digit regeneration. Further elucidation of signaling pathways governing epithelial-mesenchymal interactions in the nail unit seems to be a key to develop a novel therapeutic tool to treat amputees using nail epithelium. However, it is at least certain that the nail unit has a promising potential for the future of regenerative medicine. This review explores the biology of the nail organ by focusing on intriguing knowledge gained from recent studies., (Copyright © 2015 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.)

The nail unit is the largest and a rather complex skin appendage. It is located on the dorsal aspect of the tips of fingers and toes and has important protective and sensory functions. Development begins in utero between weeks 7 and 8 and is fully formed at birth. For its correct development, a great number of signals are necessary. Anatomically, it consists of 4 epithelial components: the matrix that forms the nail plate; the nail bed that firmly attaches the plate to the distal phalanx; the hyponychium that forms a natural barrier at the physiological point of separation of the nail from the bed; and the eponychium that represents the undersurface of the proximal nail fold which is responsible for the formation of the cuticle. The connective tissue components of the matrix and nail bed dermis are located between the corresponding epithelia and the bone of the distal phalanx. Characteristics of the connective tissue include: a morphogenetic potency for the regeneration of their epithelia; the lateral and proximal nail folds form a distally open frame for the growing nail; and the tip of the digit has rich sensible and sensory innervation. The blood supply is provided by the paired volar and dorsal digital arteries. Veins and lymphatic vessels are less well defined. The microscopic anatomy varies from nail subregion to subregion. Several different biopsy techniques are available for the histopathological evaluation of nail alterations., (©2015 Frontline Medical Communications.)

Aims: The nail mesenchyme, as ligamentous connective tissue, is classically described as a single compartment. Some authors have even suggested the concept of the nail as a musculoskeletal appendage. Recent studies conducted on supernumerary digits surgically removed for polydactyly or on the developing nail organ have introduced into the literature a new concept: the onychodermis and its onychofibroblasts that are CD10-positive/CD34-negative. The aim of this study was to explore the nail mesenchyme more comprehensively., Methods and Results: A series of 10 normal adult nail units were examined with a combination of morphological and immunohistochemical analysis. This study demonstrates that the nail mesenchyme has two distinct compartments, with a complex microanatomy of matrical dermis and its hypoderm. The matrical dermis is a relatively independent substructure, and comprises two parts: a thin papillary dermis, and a relatively thick reticular dermis. The matrical hypoderm corresponds to a cushion-like layer of adipose tissue, which distally intermingles with an area of loose connective tissue. The nail bed dermis comprises a single, relatively homogeneous compartment., Conclusion: The matrical nail mesenchyme is a modified dermis. The concept of onychodermis is not applicable in the normal adult nail. Underrecognized non-pathological structures may pose diagnostic problems. The chameleon matrical hypoderm is one such structure., (© 2014 John Wiley & Sons Ltd.)

Diagnosing nail matrix diseases requires knowledge of the nail matrix function and anatomy. This allows recognition of the clinical manifestations and assessment of potential surgical risk. Nail signs depend on the location within the matrix (proximal or distal) and the intensity, duration, and extent of the insult. Proximal matrix involvement includes nail surface irregularities (longitudinal lines, transverse lines, roughness of the nail surface, pitting, and superficial brittleness), whereas distal matrix insult induces longitudinal or transverse chromonychia. Clinical signs are described and their main causes are listed to enable readers to diagnose matrix disease from the nail's clinical features., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Topical therapy is at the forefront in treating nail ailments (especially onychomycosis and nail psoriasis) due to its local effects, which circumvents systemic adverse events, improves patient compliance and reduces treatment cost. However, the success of topical therapy has been hindered due to poor penetration of topical therapeutics across densely keratinized nail plate barrier. For effective topical therapy across nail plate, ungual drug permeation must be enhanced. Present review is designed to provide an insight into prime aspects of transungual drug delivery viz. nail structure and physiology, various onychopathies, techniques of nail permeation enhancement and in vitro models for trans-nail drug permeation studies. Updated list of drug molecules studied across the nail plate and key commercial products have been furnished with sufficient depth. Patents pertinent to, and current clinical status of transungual drug delivery have also been comprehensively reviewed. This is the first systematic critique encompassing the detailed aspects of transungual drug delivery. In our opinion, transungual drug delivery is a promising avenue for researchers to develop novel formulations, augmenting pharmaceutical industries to commercialize the products for nail disorders.

For those interested in nails, a fairly good knowledge of the anatomy of the nail unit is indispensable. But nothing will replace a careful, clinical examination of the nail apparatus. The shape of the nail, surface abnormalities and coloration, with or without a magnifying glass, may well provide a medical diagnosis not only in dermatology but also for medicine in general. Pits on the surface of the nail plate may be enough to diagnose psoriasis on a limited area of scalp dandruff. Even partial detachment of the nail apparatus might lead to the suspicion of psoriatic arthritis. A triangular lunula is associated with the absence of patellas. Finally, no pulmonary examination of a smoker is complete without looking for clubbing. It is high time to pay tribute to the nail., (Copyright © 2014. Published by Elsevier Masson SAS.)

Although surgical treatment of nail conditions can be traced back centuries to the writings of Paul Aegineta (625-690 AC), little is known about the physical laws governing nail growth. Such a poor understanding together with the increasing number of nail salons in the high street should raise legitimate concerns regarding the different procedures applied to nails. An understanding of the physics of nail growth is therefore essential to engage with human medicine and to understand the aetiology of nail conditions. In this context, a theory of nail plate adhesion, including a physical description of nail growth can be used to determine the transverse and longitudinal curvatures of the nail plate that are so important in the physical diagnosis of some nail conditions. As a result physics sheds light on: (a) why/how nails/hooves adhere strongly, yet grow smoothly; (b) why hoof/claw/nail growth rates are similar across species; (c) potential nail damage incurred by poor trimming; (d) the connection between three previously unrelated nail conditions, i.e. spoon-shaped, pincer and ingrown nails and; last but not least, (e) why ingrown nails occur preferentially in the big toes.

Purpose of Review: Nail diseases in infants and children are an uncommon cause of consultation and are often difficult to diagnose and to manage. This review will cover nail diseases that are most commonly seen in clinical practice, including congenital and hereditary disorders and inflammatory, infective, and neoplastic nail diseases. The purpose of the review is to help the reader to recognize nail disorders at an early age and to manage them appropriately., Recent Findings: Two recent large studies have reported the clinical findings of genetic disorders involving the nails, that is, pachyonychia congenita and epidermolysis bullosa. Only a few articles gave a comprehensive review of a disease, as occurred for onychomycosis, while the majority of the reports published in the recent literature involve single cases., Summary: Nail diseases in children and neonates are not easy to diagnose by nonexperts. Basic knowledge of the anatomy and biology of the nail facilitates their diagnosis as the understanding of their pathophysiology. This review gives hints at the most common nail diseases that affect infants and children.

Background: We studied the relationship between mechanical force and nail curvature., Methods: The effect of different frequencies and strengths of mechanical force on nail curvature was assessed. In Study 1, 63 carpenters and 63 office workers were enrolled, and the configurations of their thumb nails were assessed by measuring the curve index (defined as nail height/width) and pinch strength. In Study 2, nail curvature and pinch strength of jazz bassists, who characteristically do not use the right fourth and fifth fingers but use the left fifth finger a lot, were compared. In Study 3, the thumb nail curvature and pinch strength of the dominant and nondominant sides of the 126 participants from Study 1 were compared., Results: Study 1: Carpenters had a significantly lower mean thumb nail curve index and higher mean pinch strength. Study 2: The nails of the unused right fourth and fifth fingers were much more curved than the nails of the frequently used left fourth and fifth fingers. The pinch strength of the right fifth finger was much weaker than the pinch strength of the left fifth finger. Study 3: The dominant side had a significantly lower nail curve index and higher pinch strength., Conclusion: The frequency and strength of mechanical forces on finger nails significantly affect nail appearance., (© 2014 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.)

In this report, we review several inflammatory infectious and tumoral conditions of the nail unit. We emphasize the anatomic peculiarities of such pathologies of the nail unit and provide some required diagnostic criteria.

Onychomycosis is one of the most common nail disorders. It affects 10-30% of the world population and is caused by dermatophytes, non-dermatophytes, molds, and yeasts. Present treatment methods of onychomycosis include oral therapy, topical therapy, and a combination of both; they have mild-to-moderate efficacy, with a relapse and reinfection rate of 20-25%. For oral therapy, newer antifungal compounds (azole class and allylamine class) are being investigated to increase efficacy and minimize side effects. Oral therapy with antifungal agents have severe side effects, with lesser bioavailability and longer duration of treatment. By contrast, topical therapy of onychomycosis is associated with greater patient compliance and fewer systemic side effects and drug interactions. Current topical treatment options of onychomycosis are nail lacquers, ointments, lotions, solutions, and gels, but these formulations have been unsuccessful due to poor penetration and distribution of drugs at the infected site. Therefore, novel therapeutic options are constantly being researched to improve the efficacy of onychomycosis treatment by enhancing the permeation of the drug across the nail to reach the infected site. Various physical and chemical enhancement methods have been studied to increase the permeation of drugs across the nail plate to the nail bed. Device-based therapeutic options have also been investigated to increase the antifungal drug concentration and its effects in the onychomycotic nail. Randomized clinical trials of these novel therapies have demonstrated better efficacy. The present review discusses the anatomy of the human nail, onychomycosis and its types, onycholysis, and conventional and novel therapies. We also review patents granted as well as design challenges facing optimal drug formulation for onychomycosis treatment.

The nail unit comprises the nail plate, the surrounding soft tissues, and their vasculature and innervation based upon the distal phalanx. The nail plate is a laminated keratinized structure lying on the nail matrix (15-25%), the nail bed with its distal onychodermal band (75-85%), and the hyponychium at its free edge. The distal part of the matrix, the lunula characterized by its half-moon shape, can be observed in some digits. The nail plate is embedded by the proximal and lateral folds. From the proximal nail fold, the cuticle (also known as the eponychium), adheres to the superficial surface of the proximal nail plate. The nail unit possesses a complex and abundant vascular network to ensure adequate blood supply. Finally, both the periungual soft tissues and the nail folds are innervated. The shapes, structure, and inter-relationships of these tissues are factors in the way nails present with disease and how we understand and manage those diseases. In particular, an understanding of the surgical anatomy is important for those undertaking diagnostic or curative operations on the nail. With this knowledge, the most appropriate surgery can be planned and the patient can be provided with accurate and clear guidance to enable informed consent., (© 2013.)

When dealing with nails, pathologic examination is often indispensable to reach an accurate diagnosis. This requires a biopsy correctly performed by the dermatologist, a specimen correctly handled in the pathology lab, and a pathologist with good knowledge of the various nail conditions. The normal nail histology is first described in this paper. The pathologic aspects of melanocytic lesions, nonmelanocytic tumors of the nail apparatus, inflammatory nail conditions, and onychomycosis are then considered, together with their main differential diagnoses., (© 2013 Elsevier Inc. All rights reserved.)

Recent studies of mice with hair defects have resulted in major contributions to the understanding of hair disorders. To use mouse models as a tool to study nail diseases, a basic understanding of the similarities and differences between the human and mouse nail unit is required. In this study we compare the human and mouse nail unit at the macroscopic and microscopic level and use immunohistochemistry to determine the keratin expression patterns in the mouse nail unit. Both species have a proximal nail fold, cuticle, nail matrix, nail bed, nail plate, and hyponychium. Distinguishing features are the shape of the nail and the presence of an extended hyponychium in the mouse. Expression patterns of most keratins are similar. These findings indicate that the mouse nail unit shares major characteristics with the human nail unit and overall represents a very similar structure, useful for the investigation of nail diseases and nail biology., (Copyright © 2013 Wiley Periodicals, Inc.)

Necrobiosis lipoidica diabeticorum is a granulomatous skin disease of uncertain pathogenesis. Many therapeutic approaches have been reported in the literature, but none of them can be considered the gold standard. Fractional CO(2) laser treatment shows peculiar effects in the skin, mainly due to its ability of modulating cytokine pathways of tissue-repairing mechanisms. Thus, we propose fractional CO(2) laser in the management of refractory necrobiosis lipoidica in selected recalcitrant patients., (© 2012 Wiley Periodicals, Inc.)

Nail dermoscopy is becoming more and more frequently utilized for the diagnosis of nail disorders. It can be performed with handy dermoscope or with a video dermoscope, which allows magnifications of up to 200. Nail dermoscopy requires a good knowledge of nail anatomy and physiology and the pathogenesis of nail diseases: we have to know which part of the nail we have to look at! The nail is in fact not visible as a whole at one time, but its different parts should be observed, moving the lens back and forth and transversally. All nail disorders can be observed by dermoscopy. However, except for some diseases in which the technique really adds a lot to clinical examination, in most of the cases, nail dermoscopy only permits a better visualization of symptoms already evident to the naked eye. Dermoscopic features of nail signs are always very interesting and surprising, and may help in our understanding of nails., (© 2012 Wiley Periodicals, Inc.)

Brittle nails are characterized by roughness of the surface of the nail plate, fragility, and peeling. This is a condition that is seen commonly in elderly individuals, and it is associated mostly with an abnormality of keratin, keratin associated proteins, water, and/or lipid content. It is idiopathic in the majority of the cases, but there are some dermatological and systemic diseases that can be associated with brittle nails. Treatment is a challenge for the clinician, in some case, can be difficult, and certainly needs strong cooperation of the patient., (© 2012 Wiley Periodicals, Inc.)

The nail is a subject of global importance for dermatologists, podiatrists and surgeons. Nail avulsion is a frequently undertaken, yet simple, intriguing procedure. It may either be surgical or chemical, using 40% urea. The former is most often undertaken using the distal approach. Nail avulsion may either be useful for diagnostic purposes like exploration of the nail bed, nail matrix and the nail folds and before contemplating a biopsy on the nail bed or for therapeutic purposes like onychocryptosis, warts, onychomycosis, chronic paronychia, nail tumors, matricectomy and retronychia. The procedure is carried out mostly under local anesthesia with or without epinephrine (1:2,00,000 dilution). Besides the above-mentioned indications, the contraindications and complications of nail avulsion are briefly outlined.

Knowledge of the anatomy and function of the nail apparatus is essential when performing the physical examination. Inspection may reveal localized nail abnormalities that should be treated, or may provide clues to an underlying systemic disease that requires further workup. Excessive keratinaceous material under the nail bed in a distal and lateral distribution should prompt an evaluation for onychomycosis. Onychomycosis may be diagnosed through potassium hydroxide examination of scrapings. If potassium hydroxide testing is negative for the condition, a nail culture or nail plate biopsy should be performed. A proliferating, erythematous, disruptive mass in the nail bed should be carefully evaluated for underlying squamous cell carcinoma. Longitudinal melanonychia (vertical nail bands) must be differentiated from subungual melanomas, which account for 50 percent of melanomas in persons with dark skin. Dystrophic longitudinal ridges and subungual hematomas are local conditions caused by trauma. Edema and erythema of the proximal and lateral nail folds are hallmark features of acute and chronic paronychia. Clubbing may suggest an underlying disease such as cirrhosis, chronic obstructive pulmonary disease, or celiac sprue. Koilonychia (spoon nail) is commonly associated with iron deficiency anemia. Splinter hemorrhages may herald endocarditis, although other causes should be considered. Beau lines can mark the onset of a severe underlying illness, whereas Muehrcke lines are associated with hypoalbuminemia. A pincer nail deformity is inherited or acquired and can be associated with beta-blocker use, psoriasis, onychomycosis, tumors of the nail apparatus, systemic lupus erythematosus, Kawasaki disease, and malignancy.

Background: Nail disorders can be diagnostically challenging to the dermatologist. Noninvasive methods might help to avoid nail biopsies. More knowledge of the typical features of healthy nails with these techniques is needed for comparison with nail diseases., Objectives: To describe the typical morphology of healthy nails in optical coherence tomography (OCT) and confocal laser scanning microscopy (CLSM) and to examine the influence of exposure to water on OCT features, nail thickness as well as on transonychial water loss (TOWL) before and after a hand bath. Material and methods  In the first part healthy nail plates were investigated with OCT and CLSM. The thickness of layers as well as structural details were defined. Secondly, in a prospective study 30 healthy volunteers conducted 10 hand baths with water within a 2-week period. Measurements of nail thickness and signal intensity by OCT as well as of the TOWL were performed over time., Results: In OCT the unaffected nail plate appears as a band-like, layered structure, yet with some individual differences. In addition, CLSM is able to display single corneocytes and the integrity of their borders. Exposure to water led to a transient rise of TOWL and in nail thickness., Conclusions: OCT, CLSM and TOWL offer valuable noninvasive diagnostic tools for the examination of nails. Using CLSM, microscopic features like integrity of single corneocytes can be investigated. OCT allows determination of nail plate thickness and both OCT and TOWL measurements are able to detect short-term effects after exposure to water., (© 2011 The Authors. BJD © 2011 British Association of Dermatologists 2011.)

Speckle pattern, which is inherent in coherence imaging, influences significantly axial and transversal resolution of Optical Coherence Tomography (OCT) instruments. The well known speckle removal techniques are either sensitive to sample motion, require sophisticated and expensive sample tracking systems, or involve sophisticated numerical procedures. As a result, their applicability to in vivo real-time imaging is limited. In this work, we propose to average multiple A-scans collected in a fully controlled way to reduce the speckle contrast. This procedure involves non-coherent averaging of OCT A-scans acquired from adjacent locations on the sample. The technique exploits scanning protocol with fast beam deflection in the direction perpendicular to lateral dimension of the cross-sectional image. Such scanning protocol reduces the time interval between A-scans to be averaged to the repetition time of the acquisition system. Consequently, the averaging algorithm is immune to bulk motion of an investigated sample, does not require any sophisticated data processing to align cross-sectional images, and allows for precise control of lateral shift of the scanning beam on the object. The technique is tested with standard Spectral OCT system with an extra resonant scanner used for rapid beam deflection in the lateral direction. Ultrahigh speed CMOS camera serves as a detector and acquires 200,000 spectra per second. A dedicated A-scan generation algorithm allows for real-time display of images with reduced speckle contrast at 6 frames/second. This technique is applied to in vivo imaging of anterior and posterior segments of the human eye and human skin.

Objective: We compared ultrasonography (US) with the modified nail psoriasis severity index (mNAPSI) to investigate the nail plate, nail matrix and adjacent tendons in subjects with psoriatic nail disease and to test the hypothesis that nail involvement was specifically linked to extensor tendon enthesopathy., Methods: 86 psoriatic patients (169 nails) and 20 healthy controls (HC) (40 nails) were assessed with both the mNAPSI and US. The thickness of the nail plate, nail matrix region and adjacent extensor tendon were assessed and compared with physical examination findings., Results: A good agreement between clinical and sonographic nail findings was noted (kappa value = 0.52, p < 0.0001). Entheseal thickening of the extensor tendon on US was more frequent in patients with clinical nail disease compared to patients without clinical nail disease in both psoriasis and psoriatic arthritis (38 vs. 16%, p = 0.03, and 47 vs. 19%, p = 0.008, respectively). Nail thickness, nail matrix and adjacent skin thickness were higher in psoriatic patients compared to HC., Conclusion: US and clinical findings show good correlation for the assessment of the nail in psoriatic disease. The demonstration of extensor tendon enthesopathy in both psoriasis and psoriatic arthritis supports the importance of enthesopathy in nail disease pathogenesis whether or not clinical arthritis is present., (Copyright © 2012 S. Karger AG, Basel.)

The nail plate's convex shape in both the longitudinal and transverse directions is thought to contribute to its mechanical rigidity, and overcurvature can be a symptom of local and/or systemic disorders. Although a number of methods to measure the longitudinal nail curvature have been proposed, evaluation of the transverse nail curvature has been largely limited to visual estimation of overcurved nail plates. The aim of this study was therefore to measure the transverse curvature of healthy adult fingernail plates and thereby provide a baseline range for 'normal curved' nail plates. In addition, the influence of gender, age, hand size and hand dominance on the transverse fingernail curvature was investigated. The transverse fingernail curvature in 92 men and 90 women (aged 21-90 years) was measured using a set of radius gauges, and the nail plate curvature was expressed as the radius of a circle whose curve most closely approximated that of the nail plate. ANOVA was used to investigate the influence of digit nature on curvature, whereas general linear model was used to assess the influence of gender, age, and hand length, breadth and dominance on transverse nail curvature. Subsequently, the influence of hand dominance and age was further examined by paired t-test and ANOVA, respectively. In this study, baseline values for the transverse nailplate curvature of the thumb, index, middle, ring and little fingers are presented. The thumbnail is the flattest, followed jointly by the index and middle fingernails, then the ring fingernail and finally the little fingernail. Transverse nail curvature is influenced by a person's gender, age, hand dominance and hand width, but not by hand length. Thus, nails are flatter in the dominant hand, in men, in older individuals and in those with wider hands., (© 2011 The Author. ICS © 2011 Society of Cosmetic Scientists and the Société Française de Cosmétologie.)