Drilling holes in nails – getting to the root of the infection?
Managing onychomycosis is a significant part of podiatrist’s workload. For most patients, a choice exists between oral and topical, or a combination of both . The use of oral medications has proven to be the most effective with the highest cure rates  however, some patients may be unable to take these medications due to comorbidities or reluctance over the potential side effects of drugs such as oral terbinafine and itraconazole (see my earlier blog - How safe is oral terbinafine?).
Figure 1 Close up of fenestrations in a fungal nail
Topical treatments using various medications applied to the nail is often more attractive option as they have a lower rate of side effects with little or no systemic absorption. However, by its very nature the nail is a physiological barrier to drugs preventing absorption of antifungal treatments. This explains why complete cure rates for topical treatments remain significantly lower than for their oral counterparts. In addition, courses of topical medicine may be protracted – lasting over a year or more risking treatment lapse by the patient.
Studies have consistently shown that mechanical drilling (thinning) of fungal nails modestly improves response rates in onychomycosis [3-5]. In addition some work has shown that fractional lasers can penetrate the nail plate increasing its porosity to antifungal agents . In the UK, a medical device which is designed to create micropores (0.4mm in diameter) within the nail plate, has been available for several years (Clearanail®, www.clearanail.com) - see figure 1. The device retails at a price cheaper than a laser and is specifically designed to fenestrate a nail plate without the risk of penetrating the delicate nail bed beneath by sensing changes in the rotation of the burr. Hard keratin places a higher workload of the drill than soft nail bed. As soon as the underlying softer structures are reached by the advancing burr tip, the drill cuts power and safely retracts back into the device preventing any sub-ungual damage from occurring.
Clinically, there are two advantages to this. Firstly, a hole is created safely in the nail plate but secondly, the drilling produces a small amount of nail dust which collects on the nail surface. This can then be harvested and used for mycological analysis to detect the presence of any fungus. Previous research has shown that nail dust and debris harvested more proximally in diseased parts of the nail demonstrated increased sensitivity for fungal infections over nail clippings collected from the proximal edge .
So, is there any evidence to suggest that nail fenestration improves outcomes in toenail onychomycosis? In 2016, I published a paper reporting three clinical case studies where the device had been successfully used to clear onychomycosis (see figures 2-4 below). Later that year a study was published  which compared three groups of 98 patients (106 nails in total) with confirmed toenail onychomycosis. One group had holes plus oral and topical terbinafine solution, one group topical terbinafine and holes and the control group had topical terbinafine with no holes. Patients were followed up for a total of 28 weeks and mycologically retested. The results showed that drilling holes significantly improved outcomes for patients. At the final visit only 48% of the topical terbinafine only group had clear nail growth whilst the topical terbinafine group with holes showed 73% clear nail and the oral and topical terbinafine group with holes showed just over 80% clear nail growth. Statistically, it showed drilling holes made a significant difference although the difference between the two groups with holes (oral & topical v topical only) was not statistically significant.
Figure 2 Nail before Clearanail treatment
The evidence is supported by further work  which used cadaveric nails and fenestrated half of them using the Clearanail® device to assess the penetration rates of a topical antifungal (ciclopirox 8%) in unperforated and perforated nails. The nails were tested weekly and finally at day 42 to measure drug penetration. It showed that nails which were fenestrated showed 3-4 times higher drug concentrations than the unperforated nails.
Figure 3 Nail 8 weeks after Clearanail treatment (weekly spray with terbinafine solution)
Figure 4 Nail One year after Clearanail treatment
This work does suggest that nails with onychomycosis fair better when the nail is fenestrated. Full scale studies are always welcome but existing work suggests a significant benefit. Of course, there are some clinical considerations here to ensure the best results for the patient. Firstly, it is important to establish the presence of a fungal nail infection using a clinical or laboratory test, to prevent misdiagnosis and inappropriate treatment as around 50% of dystrophic nails are not fungal and visual diagnosis has been shown to be only 60% reliable. Recent research suggests that only 21% of podiatrists regularly employ any formal testing .
Following on, for any treatment to be successful, the topical antifungal agent needs a low viscosity to be able to run through any holes through into the nail bed. From clinical experience, terbinafine solution (Lamisil AT spray®) and clotrimazole (Canesten®) solution are well suited for this process but amorolfine 5% lacquer (by its viscous nature) blocks the holes and cannot be used for this purpose.
Is fenestration a better approach than just drilling nails down to the nail bed to expose fungal infection? This is untested in any formal sense, but I would say yes. Exposure of fungal hyphae through reduction of the nail with a drill allows direct application of a topical agent but as its exposed, it is unclear how long the antifungal will work for. It may evaporate, be showered or rubbed off, limiting its effect. Conversely, when an antifungal solution in introduced under a nail it is much more likely to stay in situ and continue to work longer and consequently be more effective. Additionally, where infection is close to the matrix, as the toe weight bears and the nail is compressed, the mechanical action may act to compress and spread the antifungal liquid in all directions including into the nail matrix. Anecdotally, I have had several successes clearing matrix infection where holes have been placed along the eponychial border.
Generally, the effect of fenestration can be seen over a number of weeks as discoloured infected areas of the nail become paler in colour and infected areas of nail may dissolve away (see figure 3). Patients should also be advised to treat any concomitant tinea pedis at the same time to prevent relapse or reinfection whilst undergoing treatment. Once any infection is eradicated, the new nail needs to grow through. Patients should be advised to treat any recurrence of skin infection during this time to ensure a good, continued outcome.
Declaration: The author declares he has received no financial support or incentives for producing this article.
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