The lunula: a magnetic resonance imagining approach to the subnail matrix area

Radiological imaging in nail unit disorders (Part I) - Modalities used

The nail unit is a unique skin appendage, capable of mounting only a limited number of reaction patterns to a variety of insults. This makes it difficult to diagnose many nail conditions based on clinical features alone. Thus, diagnostic modalities have an important role to play in nail disorders. Emphasis is placed on non-invasive diagnostic methods, of which, radiological imaging forms an important part; however, it is a field largely under-explored with very few studies and reports available in the literature. This could be due to the problems encountered in nail unit radiology including its small size, complex anatomy, requirement for special high-frequency probes to reliably evaluate superficial structures, and non-familiarity with nail unit radiological features even amongst trained radiologists. Nevertheless, it plays a useful role in diagnosing nail disorders (especially tumors), localizing the changes, exploring differential diagnoses, estimating prognosis, and planning management. This article is aimed at collating scientific data pertaining to various radiological modalities used in the diagnosis of nail diseases. The advantages and limitations of various imaging techniques used for evaluating the nail unit, including digital radiographs, high-frequency ultrasound, ultrasound doppler (USD), computed tomography (CT), and magnetic resonance imaging (MRI), are discussed in the first part. The second part will discuss the features of common and uncommon nail diseases.

Resident and Nonresident Fingernail Isotopes Reveal Diet and Travel Patterns,

Global travel has increased, and having a diagnostic tool to distinguish residents from visitors would be valuable. This study examined stable isotope biomarkers of fingernail tissues of resident (n = 26) and nonresident (n = 22) participants in Salt Lake City (SLC), UT, from 2015 to 2016. The purpose of this research was to determine whether fingernail isotopes could be used for reconstructing geolocation movements and to examine the convergence in nonresident fingernail isotopes to that of the resident signal following their arrival to SLC. Resident isotope values defined a baseline to make comparisons to. Initial nonresident hydrogen and oxygen isotope values were correlated with precipitation isotopes of their prior location. Fingernail isotope turnover rates were rapid and nonresident isotopes were indistinguishable from residents after ~71-90 days. The results of our study highlight the utility of stable isotope measurements of fingernail clippings to examine travel history reconstruction that could aid in identification of human remains.

A Review of Natural Joint Systems and Numerical Investigation of Bio-Inspired GFRP-to-Steel Joints

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a mechanical point of view, was undertaken. This was used to develop a taxonomy based on the different methods/functions that nature successfully uses to attach dissimilar tissues. One of the key methods that nature uses to join dissimilar materials is a transitional zone of stiffness at the insertion site. This method was used to propose bio-inspired solutions with a transitional zone of stiffness at the joint site for several glass fibre reinforced plastic (GFRP) to steel adhesively bonded joint configurations. The transition zone was used to reduce the material stiffness mismatch of the joint parts. A numerical finite element model was used to identify the optimum variation in material stiffness that minimises potential failure of the joint. The best bio-inspired joints showed a 118% increase of joint strength compared to the standard joints.

[Anatomy, biology, physiology and basic pathology of the nail organ]

The nail is the largest skin appendage. It grows continuously through life in a non-cyclical manner; its growth is not hormone-dependent. The nail of the middle finger of the dominant hand grows fastest with approximately 0.1 mm/day, whereas the big toe nail grows only 0.03-0.05 mm/d. The nails' size and shape vary characteristically from finger to finger and from toe to toe, for which the size and shape of the bone of the terminal phalanx is responsible. The nail apparatus consists of both epithelial and connective tissue components. The matrix epithelium is responsible for the production of the nail plate whereas the nail bed epithelium mediates firm attachment. The hyponychium is a specialized structure sealing the subungual space and allowing the nail plate to physiologically detach from the nail bed. The proximal nail fold covers most of the matrix. Its free end forms the cuticle which seals the nail pocket or cul-de-sac. The dermis of the matrix and nail bed is specialized with a morphogenetic potency. The proximal and lateral nail folds form a frame on three sides giving the nail stability and allowing it to grow out. The nail protects the distal phalanx, is an extremely versatile tool for defense and dexterity and increases the sensitivity of the tip of the finger. Nail apparatus, finger tip, tendons and ligaments of the distal interphalangeal joint form a functional unit and cannot be seen independently. The nail organ has only a certain number of reaction patterns that differ in many respects from hairy and palmoplantar skin.

Nail biology and nail science

The nail plate is the permanent product of the nail matrix. Its normal appearance and growth depend on the integrity of several components: the surrounding tissues or perionychium and the bony phalanx that are contributing to the nail apparatus or nail unit. The nail is inserted proximally in an invagination practically parallel to the upper surface of the skin and laterally in the lateral nail grooves. This pocket-like invagination has a roof, the proximal nail fold and a floor, the matrix from which the nail is derived. The germinal matrix forms the bulk of the nail plate. The proximal element forms the superficial third of the nail whereas the distal element provides its inferior two-thirds. The ventral surface of the proximal nail fold adheres closely to the nail for a short distance and forms a gradually desquamating tissue, the cuticle, made of the stratum corneum of both the dorsal and the ventral side of the proximal nail fold. The cuticle seals and therefore protects the ungual cul-de-sac. The nail plate is bordered by the proximal nail fold which is continuous with the similarly structured lateral nail fold on each side. The nail bed extends from the lunula to the hyponychium. It presents with parallel longitudinal rete ridges. This area, by contrast to the matrix has a firm attachment to the nail plate and nail avulsion produces a denudation of the nail bed. Colourless, but translucent, the highly vascular connective tissue containing glomus organs transmits a pink colour through the nail. Among its multiple functions, the nail provides counterpressure to the pulp that is essential to the tactile sensation involving the fingers and to the prevention of the hypertrophy of the distal wall tissue, produced after nail loss of the great toe nail.

Feasibility study of 3-T MR imaging of the skin

The purpose of this study was to assess the quality of 3-T magnetic resonance (MR) imaging of the skin, to describe skin anatomy at 3 T and to discuss future prospects of skin MRI. A 7-cm single-element surface receiver coil was developed for our 3-T MRI system. Thin sections were obtained with a three-dimensional FIESTA acquisition sequence and a spin-echo T1-weighted sequence (SET1). Prospective analysis was performed twice by two radiologists independently. Thirty-six healthy volunteers were included and underwent MRI on the face and the calf. Image quality was assessed regarding visibility of skin layers and quantification of artefacts. High field strength MR enables imaging of the skin with a high spatial in-plane resolution (87-180 microm), the total examination lasting 15-20 min. Image quality was excellent for the calf (mean SET1 quality = 96%) with a high intra- and interobserver correlation (SET1 kappa coefficient concerning visibility of epidermis, dermis and hypodermis > or = 0.84). Motion artefacts resulted in a small loss of quality and reproducibility for the face. In conclusion, 3-T MR allows high spatial resolution imaging of the skin and can potentially provide an accurate noninvasive means of analysing the skin.

Advances in MR imaging of the skin

MR imaging of the skin is challenging because of the small size of the structures to be visualized. By increasing the gradient amplitude and/or duration, skin layers can be visualized with a voxel size of the order of 20 microm, clearly the smallest obtained for in vivo images in a whole-body imager. Currently, the gradient strength of most commercial systems enables acquisition of such a small voxel size, and the main difficulty has thus become to achieve sufficient detection sensitivity. The signal-to-noise ratio (SNR) can be increased either by increasing the magnetic field strength or by minimizing noise with small coils; cooling copper coils or superconducting coils can enhance the SNR by a factor of 3 or more. MR imaging, because of the large number of parameters it is able to measure, can provide more than the microscopic architecture of the skin: physical parameters such as relaxation times, magnetization transfer or diffusion, and chemical parameters such as the water and fat contents or phosphorus metabolism. In spite of the amount of information they have provided to date, MR imaging and spectroscopy have had limited clinical applications, mainly because cutaneous pathologies are easily accessible to the naked eye and surgery. However, MR technologies indeed represent powerful research tools to study normal and diseased skin.

[Treatment of post-traumatic nail bed deformities with split-thickness nail bed grafts]

INTRODUCTION

Split-thickness nail bed graft have been proposed for treatment of post-traumatic nail bed dystrophies. Only three papers reported good results in 60 to 90% of cases. We report our experience.

MATERIAL AND METHODS

We reviewed 18 cases of split-thickness nail bed grafts from operative and consultation files and photographs. Evaluation was made using criteria as the nail plate shape, its adhesion on the nail bed, patient satisfaction and possible sequelae on the donor finger. RESULTANTS: Thirteen patients have been reviewed with a sufficient follow-up to assess the results. In 13 cases, the graft was taken from the hallux. The nail-bed graft was used for hallux reconstruction two times, the thumb six times, index six times, middle and ring finger one each, and the little finger two times. In every patient the graft was molded using either the patient nail or the nail plate from the donor finger. Clinical results were excellent in five cases, good in three and poor in five cases. Five failures were due to wrong indications in three cases in which matrix problem has been underestimated, and infectious failures in two cases. Fifteen per cent of our patients had some sequelae on the donor finger.

Subungual myxoid cysts: clinical manifestations and response to therapy

BACKGROUND

Myxoid cysts located beneath the nail are very different from those within the nailfold and there is no established literature on their diagnosis and therapy.

OBJECTIVE

Thirty-five cases of subungual myxoid cyst are described in which the diagnosis was confirmed by magnetic resonance imaging, surgical exploration, or both.

METHODS

The clinical characteristics of all cases of subungual myxoid cysts confirmed in 3 specialist nail clinics are reported. Twenty cases were confirmed by magnetic resonance imaging. Histologic details were recorded in 4 cases.

RESULTS

Thirty-four patients (22 female, 12 male) presented with a subungual tumor of the thumb (n = 25) or finger (n = 10). The 3 main clinical variables were color of the lunula, transverse nail curvature, and integrity of the nail. In 26 cases the lunula was discolored; it was red in 22 cases, blue in 3, and as part of a longitudinal leukonychia in one. Transverse curvature was increased in 29 cases and was normal in 5 cases; in one case the nail was destroyed. In 11 cases, the change in curvature led to lateral ingrowing. Surgery (n = 22), sclerosant (n = 1), and spontaneous discharge (n = 2) all resulted in resolution. Ten patients had no treatment.

CONCLUSION

This study describes 35 subungual myxoid cysts having characteristic features that allow clinical diagnosis. They respond to a range of treatments.

Lupus erythematosus-associated red lunula

BACKGROUND

Red lunulae have only rarely been described in patients with lupus erythematosus.

OBJECTIVE

We assessed the frequency and classified the type of red lunulae in patients with definite lupus erythematosus seen in an interdisciplinary dermatorheumatologic outpatient clinic.

METHODS

We studied 56 patients with either systemic or cutaneous lupus erythematosus for the presence of red lunulae.

RESULTS

Eleven of 56 patients (19.6%) with lupus erythematosus had red lunulae. All of them showed a complete type of red lunulae, which was seen on all finger nails in 10 patients and on a single finger nail in 1 patient. Seven patients suffered from systemic lupus, the other from subacute cutaneous (n = 2) or chronic discoid cutaneous lupus (n = 2). There was no statistically significant difference in autoantibody expression or treatment regimen between patients with or without red lunulae. However, symptomatic patients had a shorter disease interval, and all but 1 showed either periungual erythema or chilblain lupus. Periungual erythema was not observed in any patient without red lunulae.

CONCLUSION

Red lunulae, although rarely described in the literature, are not an uncommon symptom of patients with lupus erythematosus. They seem to be associated with periungual erythema or chilblain lupus. Red lunulae should be considered in the clinical spectrum of lupus disease.

Etiology and treatment of nail malalignment

BACKGROUND

There are three main types of nail malalignment. These are: congenital nail malalignment of the big toenail, traumatic nail malalignment, and iatrogenic malalignment of the nail plate.

OBJECTIVE

Treatment is only of benefit in the first two conditions, and specific surgical approach to each condition is outlined. The probable mechanism of iatrogenic malalignment is discussed.

RESULTS

Nail rotation for congenital malalignment produces its best results in early childhood.

CONCLUSION

Surgery is of benefit in congenital malalignment and traumatic malalignment and is worthwhile in selected cases. Iatrogenic malalignment that is the consequence of wide lateral nail biopsies or similar excisions does not respond to treatment.

Lymphedematous skin and subcutis: in vivo high resolution magnetic resonance imaging evaluation

Physico-chemical and morphologic parameters of skin layers and subcutaneous tissue in lymphedematous limb were studied in vivo using magnetic resonance imaging. High resolution images were obtained with a depth resolution of about 70 microm, using a specific surface gradient coil specially designed for skin imaging and connected to a standard whole-body imager at 1.5 T. Twenty-one patients with unilateral lower extremity lymphedema (11 primary and 10 secondary) were examined. Skin thickness, relaxation times, and relative proton density were calculated in lymphedematous limbs and in contralateral extremities. In diseased limbs, the average skin thickness (2.17 mm) was significantly larger (p = 1.5 x 10(-4)) than that of contralateral limb (1.14 mm). Major cutaneous alterations due to lymphedema took place in dermis. In lymphedematous dermis, the significant increase of relaxation time values could be due to a shift in the equilibrium of water inside this tissue in relation to the interactions between macromolecules and water molecules. In lymphedematous epidermis our results showed an increase in the number of free water protons. Information about water and fat distribution in lymphedema was also obtained using chemical shift weighted images. Our results demonstrated a water retention diffusely spread over the entire dermis, and an important fluid retention located in the interlobular spacing and beside the superficial fascia. Inside the subcutis, the mean thickness of the superficial fat lobules was increased more than that of the deep fat lobules. From all the various measurements we could not distinguish primary from secondary lymphedema.