Nowadays, with the development of high- and ultra-high-resolution linear transducers, nail ultrasound has gained relevance in the identification of traumatic injuries, tumors, and inflammatory conditions, among others, providing useful information for clinical management, surgical planning, and monitoring disease inflammatory activity and effectivity of the treatment.
Which technical considerations do we need to keep in mind?
In all areas of dermatological ultrasound, the evaluation of the nail must be performed with a high-resolution linear transducer, ideally between 15 and 24 MHz, which allows for a perfect anatomical definition of all the components on the nail unit. It is expected to use enough gel between the transducer and the surface of the nail in order to be able to correctly see all the components of the nail (Figure 1), some authors have used other techniques such as immersing the nail in water or the use of pads, but in my practice I consider the first one to be more practical. It is always important to analyze in gray scale, Doppler, Duplex, and color; of course in axial and longitudinal view.
Ultrasound Anatomy of the Nail
The nail unit is made up of three main components: nail plate, nail bed, and matrix, as seen in Figure 2. Each of these has a precise sonographic definition. We also need to evaluate the periungual area compound for periungual folds. Furthermore, it’s important to include the distal phalanx, the distal interphalangeal joint, and the extensor tendon in the evaluation, mainly for inflammatory diseases such as psoriasis.
Why use ultrasound in the nail unit for inflammatory diseases?
The clinical findings of inflammatory nail diseases such as psoriasis, lichen, scleroderma, arthritis, and lupus may be very similar and difficult to differentiate. The use of biopsy leads to scarring and deformation of the nail. The morphological changes shown on ultrasound for these diseases are very characteristic, and, with adequate clinical correlation, we can avoid the use of biopsy. In psoriasis for example, five sonographic stages are described for the identification of the stage of the disease, and we have the ability to monitor the inflammatory activity by using Doppler evaluation and analyze the distal enthesis of the extensor tendon and synovial proliferation in the interphalangeal space. This is very important to develop early findings of psoriatic arthritis, even in subclinical stages, and this information can be crucial for the prognosis and treatment of patients.
Why use nail ultrasound in tumors?
Most nail tumors (73%) are ungular tumors and 27% are periungual. Ultrasound can show the classic appearance of multiple tumors to allow a clear diagnosis and information for surgical planning and treatment. Some studies have shown that ultrasound can change the clinical diagnosis in 35% of cases. For glomus tumors or exostoses, ultrasound can have a specificity of 100% (Figure 3).
Why use nail ultrasound for trauma?
The nail unit is very prone to micro and macro-trauma. Micro-trauma can produce dystrophic changes in the nail plate that can simulate other nail diseases such as onychomycosis or nail psoriasis, retronychia and onychomadesis, being able to differentiate them adequately with ultrasound (Figure 4). In macro-trauma, fragmentation of the plate, hematomas, and even fractures of the distal phalanges can be diagnosed.
As we can see, ultrasound can give us sufficient and very clear information on all the components of the nail unit. Nail ultrasound may be more widely available than other diagnostic tools like MR, it also has more spatial resolution and there is no need for contrast. Of course, ultrasound nail evaluation should be performed following the technical recommendations for Dermatological ultrasound, and the study needs to be performed by a qualified individual with training and knowledge of nail pathology, which can be very challenging. In that scenario, it can be considered the first-line modality to clear up multiple nail pathologies.
References
Aluja Jaramillo F, Quiasúa Mejía DC, Martínez Ordúz HM, González Ardila C. Nail unit ultrasound: a complete guide of the nail diseases. J Ultrasound 2017; 20:181–192. doi:10.1007/s40477-017-0253-6
González CP. Ultrasonido de alta resolución en enfermedades benignas de la piel. Revista De La Asociación Colombiana De Dermatología Y Cirugía Dermatológica 2018; 26:230–239. doi.org/10.29176/2590843X.124
Kromann CB, Wortsman X, Jemec GBE. High-Frequency Ultrasound of the Nail. In: Humbert P, Maibach H, Fanian F, Agache P (eds). Agache’s Measuring the Skin. Springer, Cham; 2015.
Wortsman X, Alfageme F, Roustan G, et al. Guidelines for performing dermatologic ultrasound examinations by the DERMUS Group. J Ultrasound Med 2016; 35:577–580.
Claudia Gonzalez, MD, is a Radiologist at Rosario University in Bogota, Colombia, is Vice Chair of the Dermatologic Ultrasound AIUM Interest Group, and has a Private Practice for high-resolution dermatological and MSK ultrasound in Bogotá, Colombia.
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I saw a “hockey stick” probe. Instinctively, I decided to use it on my fingernails. The images I saw on the screen were so fantastic that I ran to the library to see if there were any papers or publications that focused on ultrasound of the nail.