Can A New Nail Trephination Device Help Treat Nail Conditions?

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By Andreas Boker, MD; Clinical Editor: Jesse Burks, DPM

The fully keratinized, thick multilayered structure of the nail plate presents a formidable barrier to nail bed access. This limits the options for treatment of nail diseases such as onychomycosis and subungual hematoma from nail trauma. Until recently, clinicians considered nail removal as an option for formal repair of the nail bed for subungual hematomas involving large regions of the nail bed.1

Penetration enhancing formulations have aided the delivery of molecules to the nail bed through the impermeable nail plate.2 Researchers have used a carbon dioxide laser to treat pincer nail deformity.3 Other authors have demonstrated the use of nail abrasion via sanding of the nail plate to decrease the nail thickness or remove the nail plate completely to facilitate penetration of topical medicines.4 However, these uncontrolled methods cause significant discomfort and may lead to structural deformities in the nail plate.

Podiatrists and dermatologists are also using nail trephination or nail punch biopsy to treat several nail abnormalities. Researchers have shown that mesoscissioning provides a controlled, painless way of creating openings in the nail plate. These microscopic openings, called transungual microconduits, are less than 0.5 mm in diameter and offer minimally invasive access to the nail bed.

The PathFormer (Path Scientific), a handheld device that operates on the mesoscissioning principle, allows one to trephinate the nail virtually painlessly, according to one completed pilot clinical trial and a second ongoing, double-blind clinical trial. This device, which is approved by the Food and Drug Administration for controlled nail trephination, has the potential to transform the treatment of nail disease ranging from subungual hematomas to onychomycosis.

A Closer Look At Mesoscissioning Technology
Mesoscissioning technology uses a microscopic cutter to scission (or cut) a circular opening in the nail plate. The keratinized nail plate has a high electrical resistance. As the cutter progresses into the nail plate, it removes successive layers of the nail plate and accordingly decreases the electrical resistance to the epidermis. The resistance can reduce from a few megaohms for an intact nail plate to tens of kilohms for an opening extending to the stratum corneum free nail bed. Mesoscissioning exploits this reduction to limit the intervention depth and thus avoids reaching the underlying innervated nail bed.

The result is a virtually painless procedure that creates a well defined microscopic hole in the nail plate. By varying the trigger resistance at which one pulls the cutter away from the nail, physicians can intervene superficially, partly, halfway or all the way into the nail plate.

The PathFormer device contains two micromotors. One rotates a 400 micron diameter cutter that scissions the nail plate and the other moves the cutter towards or away from the nail. The cutting motor is connected to an electronic control that measures the electrical resistance between the rotating cutter and an electrode one places on the patient’s skin. The cutter abruptly stops and retracts from the nail when one has reached a preset resistance, leaving a cylindrical microconduit in the nail plate.

The PathFormer cable connects to a pair of monitoring electrodes on the patient’s skin and the power supply unit clips to the operator’s belt. The physician presses and holds down the actuating button until the cutter automatically pulls away from the nail after creating a microconduit. The scissioning time is approximately two seconds.

In one case, surgeons created typical transungual microconduits in a human volunteer toenail using a PathFormer. The surgeon created four microconduits, approximately 400 microns in diameter and about 2 cm apart. The bottom of a newly created microconduit is soft but it slowly hardens over a period of 24 hours. However, hydrating the toenail and keeping it occluded (with a non-porous Band-Aid) prevents the microconduit bottom from hardening.

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