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  • Ivan Bristow

Silver Nitrate - an alternative to phenol in nail surgery

Nail surgery is an effective and curative treatment for ingrowing toenails carried out by podiatrists globally. As with all surgical procedures there are many ways to approach it. Much of this variation surrounds the most effective and efficient means to remove or destroy the germinal matrix to prevent recurrence after the removal of lateral edge of the nail. Techniques include surgical excision, destruction using energy-based sources (such as electrosurgery and laser) or chemical destruction with phenol or sodium hydroxide, for example.





A new paper will shortly be available which looks at the effectiveness of a less commonly used chemical agent (but one which is readily available to podiatrists) – silver nitrate (AgNO3). In the American journal “Pediatric Dermatology” [1] medics in a paediatric surgery centre in Spain retrospectively reviewed three years of records of children undergoing nail surgery using silver nitrate to ablate the matrix. Using a case-control design, they compared these cases with children undergoing the same procedure at their department using electro-cautery examining infection rates and recurrence in the post-operative period.


A total of 209 patients underwent a total of 382 matricectomies. Group A underwent the procedure using electrocautery for matrix ablation under a general anaesthetic (86 patients, a total of 151 sulci treated) whilst group B underwent a procedure under local anaesthesia using silver nitrate to ablate the matrix (123 patients, 231 sulci). Post-operatively all patients received an antiseptic and dressing to the treated area and were evaluated at 1 week and 1 month post-operatively and followed up with a telephone consultation. Median follow up time for groups A and B were 21 and 45 months respectively. Comparison of the two groups revealed that patients undergoing cautery (group A) had higher rates of post-operative infection (4% versus 1.7%) whilst regrowth rates were 11.2% and 4.7% in the two groups respectively.


The study highlights that both groups were similar in age and other demographic data. Whilst the paper suggests that silver nitrate may be a more favourable option, it must be considered that this was a retrospective study which can only suggest effectiveness whilst a randomised controlled trial would be the gold standard by which to assess the true differences between the two techniques.


Is there any other evidence to suggest silver nitrate may be effective? An earlier study undertaken in 2018 [2] adopted a similar study design and reviewed the records of patients of all ages comparing 132 patients who underwent a phenol or silver nitrate ablation. Both groups underwent the procedure in a similar manner with a digital block and application of either of the two chemicals for just 10 seconds (with no flushing of the area). The site was treated with an antiseptic dressing and patients were followed up on a daily basis for wound cleansing and redressing using povidone-iodine and fusidic acid until the wound had fully healed. The data from this study suggested that wound healing in the silver nitrate group was slower (median of 5.1 weeks in the phenol group versus 8.1 weeks in the silver nitrate group). In addition, the phenol group had no post-operative pain or infection whilst 43% of the silver nitrate patient suffered infection after the procedure. Moreover, 65% of the silver nitrate patients reported post-operative pain. There were no complications noted in either group.The overall success rates were 98.8% in the phenol group and 96% in the silver nitrate cohort.


Silver nitrate has been well known to podiatrists for decades as a topical application for the treatment of warts along with the black stain it creates on the skin due to release of silver ions into the epidermis. In addition, due to its cauterising properties can cauterise tissue and halt minor bleeding. It also has mild antibacterial properties. The idea that silver nitrate maybe a suitable alternative to phenol for nail surgery is certainly attractive given that its storage and application risk a significantly lower rate of complications and problems than phenol. However, the evidence provided from these two papers can only at best confirm it can be used to ablate the nail matrix, showing recurrence rates of less than 5% in the two studies, but other aspects may require more studies before firm conclusions can be drawn.


From the second study post-operative infection and pain were much higher in the silver nitrate group which is of concern. Although silver nitrate is known to possess some antimicrobial properties it would seem phenol was more effective in preventing post-operative infection. The anaesthetic effect of phenol is also well known possibly accounting for the lack of reported pain for patients in this group. For both studies though the application times of just 10 seconds are much lower than the 1 – 3 minutes often cited for phenol application. Healing times were also seemingly prolonged in the silver nitrate group which is perhaps a surprise as it has been long known that phenol continues to be locally present in tissue after its application to tissue [3] and may account for a slower rate of healing.


At this time, although silver nitrate appears to possess ablation capacity, other considerations need further exploration in terms of healing times, post-operative pain and patient satisfaction. A well designed randomised controlled trial comparing the gold standard phenolisation technique with silver nitrate may go some way to addressing these issues this but for the moment, there won’t be a significant shift in practice.


Note:

For podiatrists in the UK, current nail surgery guidelines (2022) are available for download [4] from the Royal College of Podiatry Website.



References



1. Delgado-Miguel, C., et al., The effectiveness of matrix ablation with silver nitrate in the treatment of ingrown toenails. A single-center case-control study. Pediatric Dermatology, 2022. Early view.

2. Al-Lenjawi, B., et al., The Treatment of Ingrown Toenails: A Retrospective Study of Combined Wedge Resection with Phenol Versus Silver Nitrate Cauterization. Dermatology Open Journal, 2018. 3(1): p. 10-14.

3. Dagnall, J.C., The History, Development and Current Status of Nail Matrix Phenolisation The Chiropodist, 1981. 36(9): p. 315-324.

4. Royal College of Podiatry. Nail Surgery Guidelines (V6.1). 2022 October 2022 [cited 2022 December ].

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