Ultrasound Imaging of Nails
Section snippets
Principles and normal ultrasound anatomy
Ultrasound imaging is based on the time delay that occurs when ultrasound beams are reflected from different tissues. The clarity of the image depends on the structure of the tissue, its echogenicity, and several technical factors.
Modern diagnostics usually are performed with the new generation of high-resolution ultrasound machines that can process data over 9216 channels per image frame with dynamic ranges of 170 db, and with the appearance of high-frequency compact linear transducers that
Normal ultrasound anatomy
The nail ultrasonographic unit can be divided in three segments
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the plate (dorsal and ventral)
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the matrix
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the nail bed
The dorsal and ventral aspects of the nail plate are viewed as bilaminar, hyperechoic (white), parallel bands with a virtual hypoechoic (dark gray) space between them called the interplate space. The nail bed appears as the hypoechoic region under the plate, and the nail matrix is the echoic (soft gray) region at the proximal end of the nail bed [5], [9].
The nail bed is an
Tumors
Ultrasound is well suited to the identification of tumors with characteristic changes of density, unique flow, or a cystic component. The subungual hematoma or abscess also is detected as a fluid anechoic (black) region at the nail bed, and may contain echoes or septations inside. On occasion, fluid collection dissects the planes of the tumor and extends to the rest of the distal finger, often beginning at the lateral borders of the nail bed and producing a generalized edema of the distal
Inflammatory changes
The detection of inflammation at the nail can be seen as enlargement of the nail bed with a decrease in echogenicity (Fig. 7). In a left-to-right comparison, the operator often can detect subclinical inflammatory changes. The use of Doppler and Power Angio permits visualization of a diffusely increased vascularity (not localized as the glomus tumor) and an absence of erosions of the bone margin of the distal phalanx. Inflammation also may increase the convex shape of the bilaminar hyperechoic
Nail psoriasis
The use of ultrasound as a noninvasive method for psoriatic nail study offers an advantage over clinical examination. Clinically imperceptible changes can be found in early disease, particularly in studies of the ventral nail plate. The hyperechoic deposits seen at the plate correlate with the subungual hyperkeratosis, and in the advanced stages of the disease the involvement of both plates is visible. With advanced disease there is an enlargement of the nail bed compared with healthy control
Candidiasis and fungal infections
Fungal involvement of the nail unit produces a significant increase in the thickness of the nail bed greater than that observed with nail psoriasis; diffuse thickening of the nail plate also occurs (Fig. 10). Just as in psoriasis, however, these can merge in one thick plate in ultrasound. More observations will have to be made in this field in terms of detecting early changes that may be specific to fungal involvement.
Trauma
Traumatic nail deformities, such as nail lacerations or subsequent scarring, can cause problems of continuity between the nail plate and the nail bed. Ultrasound can detect the exact site of laceration and its extension, and it can determine the position of dislocated nail plate fragments following trauma (Fig. 11). Associated damage of the insertion of the extensor tendon at the base of the distal phalanx also can be identified. Ultrasound can be particularly useful when general edema and pain
Discussion
The use of a noninvasive method for the study of human nails offers several advantages over existing research methodology: it allows for longitudinal studies, it provides information about subcutaneous processes, and it allows for quantification of blood flow. The use of ultrasound is particularly appropriate for the study of nail morphology because of the differences in tissue density. Furthermore, the use of ultrasound is convenient because appropriate technology is readily available in most
Summary
Based on the principle of reflected sound waves, ultrasound imaging provides an abstract picture of tissue morphology that may be used to diagnose a wide range of diseases. The nail apparatus contains tissues of various echogenicities, and is thus well suited for ultrasound examination. Moreover, ultrasonography is widely available and is noninvasive, and may therefore be used for longitudinal studies of tissues and diseases. There are methodological limitations in the resolution of ultrasound
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2021, Joint Bone SpineCitation Excerpt :After this discovery, sonographic analysis of an inspectional normal nail aroused curiosity that subclinical abnormalities may be associated with PsA [2,10]. Then, some NUSG changes such as disruption of the trilaminar appearance of the nail plate, fusion (absence of definition of the ventral plate), increased thickness of the nail plate and bed, and increased power Doppler activity of the bed/matrix were described in PsA [6–9,11,12]. However, there was a disparency between the study results.