A Calculating Method for Nail Growth Using CO₂ Laser Drilling and Dermoscopy

Dear Editor:

Some patients with nail dystrophy complain that their dystrophic nails do not grow (Fig. 1A). These patients ask whether their nails are actually growing. However, this is not easy to confirm with the naked eye because fingernails and toenails normally grow at rates of 3.5 mm/month and 1.6 mm/month, respectively, in healthy people1. It is often difficult to notice a difference in nail length, even if you take a picture and compare it with the nail 1~2 months later or mark the nail with a pen, as the mark is easily removed. In such a case, to show that the nail is growing, a fixed reference point around the nail and an indelible mark on the nail are required. The proximal nail fold is a good reference point, but it is often difficult to find an indelible mark. If there is no indelible mark on the nail, CO₂ laser drilling is useful. Small holes can be made with the CO₂ laser in continuous mode at 1-W power (Fig. 1B). Drilling too deep may hurt the nail bed, and a hole that is too shallow is easily blurred by external friction. The procedure is stopped just before the patient feels a little pain or after 0.5 seconds. Positioning the holes 1 to 2 mm away from the distal end of the lunula is safe and keeps them indelible. Drilling too close to the proximal nail fold may injure the nail matrix during the procedure, and if the holes are too distal from the proximal nail fold, they may disappear owing to external friction and tiny foreign material that can easily get into the holes. Pictures are captured using dermoscopy in polarized mode immediately after the procedure and again 6 weeks later and are compared. A ruler placed in the dermoscopy window parallel to the direction of nail growth makes it easy to detect fine changes in length (Fig. 1C). This is an easily accessible and definite procedure to confirm nail growth. Although there are several methods to assess nail growth, including special marks on the nail plate with ink, nitric acid, or a razor blade and magnifying lens with fine calibration2, 3, 4, the marks are easily removed and the methods are sometimes not available in ordinary dermatologic clinics. On the other hand, since the CO₂ laser is one of the most popular lasers globally, most dermatologists are able to easily access the CO₂ laser in their clinics. In addition, dermoscopy has recently been recognized as an essential approach for dermatologists to make a diagnosis of nail disorders5. Many dermatologists already have it, as it has become a must-have device for dermatologists. Lastly, this procedure is simple, fast, and safe. It does not need anesthesia, and the only possible complications are damage to the nail bed and mild pain (visual analog scale score 2~3) that can be avoided with careful use of the CO₂ laser. Moreover, the holes naturally resolve without treatment and are unlikely to have any sequelae.

Fig. 1
(A) A patient wants to confirm whether her dystrophic nail is really growing. (B) A polarized contact dermoscopic image without immersion of six holes made by drilling with a CO₂ laser in continuous mode at 1-W power for 0.5 seconds (magnification, ×10). If the holes are properly positioned 1~2 mm away from the distal end of the lunula, 2 or 3 holes in one row will suffice. (C) A polarized contact dermoscopic image without immersion 6 weeks after the procedure. The holes have got smaller, but about 0.5 mm of nail growth is detected. The patient is satisfied to learn that her nail is still growing (magnification, ×10). We received the patient's consent form about publishing all photographic materials.

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