Nail StrainStress Meter NM 100: A novel in vivo method to characterize biomechanical properties of nails.

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.

Nail Anatomy, Nail Psoriasis, and Nail Extensor Enthesitis Theory: What Is the Link?

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.

Correlation between tibial nail length and olecrenon to 5th metacarpal head measurement: An anthropometric study.

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.

A simulation model of nail bed suture and nail fixation: description and preliminary evaluation.

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.

Chemical and physical strategies in onychomycosis topical treatment: A review.

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.

Microscopy of Common Nail Cosmetics.

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.

Surface Anatomy of the Nail for the Dermatologist.

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.

Use of optical profilometry and visual grading for measurement of longitudinal striations of the nail.

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 0­5 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.

Assessment, management and treatment of acute fingertip injuries.

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.

The nail dermis: from microanatomy to constitutive modelling.

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.

Anatomic relationship of the proximal nail matrix to the extensor hallucis longus tendon insertion.

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.

Anatomy of the nail unit and the nail biopsy.

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.

Physics of nail conditions: why do ingrown nails always happen in the big toes?

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.

Nail disorders in infants and children.

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.

Effect of mechanical forces on finger nail curvature: an analysis of the effect of occupation on finger nails.

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.

Surgical anatomy of the nail.

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.

Efficient reduction of speckle noise in Optical Coherence Tomography.

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.

Confocal laser scanning microscopy, optical coherence tomography and transonychial water loss for in vivo investigation of nails.

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.