Plantar Warts: Advanced Treatment Techniques

Plantar warts have no specific pharmaceutical treatment, as no drug has yet been developed that can inhibit the HPV virus that causes the infection. Instead, surgical or non-surgical alternatives are available to remove the wart, with immunomodulator and photodynamic therapy as examples of more recently adopted treatment options.
Nonsurgical treatment options are:

• use of keratolytics
• use of vesicants
• immunomodulators
• photodynamic therapy

Keratolytics

Keratolytics are the most widely used products in the nonsurgical treatment of warts. They cause the controlled destruction of the wart by working on the breakdown of keratins.
The most commonly used keratolytic agent is highly concentrated salicylic acid, which is applied to the wart with the help of elastic collodion. Flexible collodion is a viscous liquid that, on contact with air, solidifies and forms a film on the skin.
There are many commercially available salicylic acid/flexible collodion treatments, which usually contain salicylic acid at a concentration of about 15% or 16%. Some products may also contain lactic acid and other ingredients.
The preparation is applied directly on the wart with a special spatula that is attached to the product cap. Keratolytics can also be used to treat mosaic and periungual warts.
A potential side effect of salicylic acid in flexible collodion occurs when it is poorly applied by the patient. This means the wart will not be eradicated properly, and if the solution is overused or haphazardly applied, it may cause irritation on healthy skin surrounding the wart.

The salicylic acid pickling method

The treatment method combines the use of salicylic acid in flexible collodion with the manual pickling of the hyperkeratotic part of the wart. The following formula is used:

• Salicylic acid 3g
• 5% flexible collodion 5g
• Ethyl ether 1g
• Ethyl alcohol 1g

Prepared in dropper bottle. In practice, the treatment should be applied as follows:

• Remove the hyperkeratotic part of the wart using a nail file, mechanical bur, or gouge, taking care not to cause punctiform bleeding.
• Apply a drop of the salicylic acid/flexible collodion solution to the individual wart or spread the product on the area of any mosaic or periungual warts.
• Wait ten minutes until the solution has completely solidified
• Do not cover
• Do not wet the area for the remainder of the day. Washing can resume as normal on non-application days.
• If treating at home, repeat the application every other night. If being treated by a podiatrist who is able to perform professional “pickling”, repeat once per week.

The advantages of the salicylic acid pickling method are:

• pain free
• non-scarring
• no need for anesthesia
• the wart will not come back
• no need to pause usual routine

The disadvantages of the salicylic acid pickling method are:

• Lengthy healing time
• Lengthy application procedure

Wart plasters and discs are commercially available and claim to treat warts through salicylic acid binding on the stratum corneum to cause keratolysis. The medicated plasters or discs come in diameters of 6mm, 12mm and 20mm, with 3.75mg, 13.5mg and 36.3mg of salicylic acid, respectively. The diameter of the plaster or disc should be in line with the size of the wart.
While the plasters and discs might seem a handy treatment option, some difficulties arise:

• The thickness of the plasters can increase pain when standing or putting pressure on the foot
• The plaster or disc can unstick when walking
• The salicylic acid on the plaster can damage healthy skin around the wart
• In children, high concentrations of salicylic acid can cause irritation and pain

For these reasons, the salicylic acid pickling method is safer and more effective.

Use of blister agents (vesicants)

Some blister agents that cause dermo-epidermal detachment can be used to treat warts because they can generate the removal of the entire wart, which is an intraepidermal lesion.
Cantharidin is extracted from the blister beetle, belonging to the coleoptera genus, and is the vesicant that has the necessary properties to trigger dermo-epidermal detachment. Cantharidin, however, is not commercially available for human use in Europe, and in order to use it, a specific preparation must be made from the dried blister beetles. While the process of extracting cantharidin itself is not complicated, the titration of the extract (how much cantharidin it contains) is difficult.
The resulting cantharidin-containing extract appears as a sticky, viscous brown liquid which is applied directly to the warts, allowed to dry and covered with gauze
Cantharidin causes complete dermo-epidermal detachment within 12 to 24 hours with the formation of a blister. The blister and then the wart can be detached carefully with a scalpel blade, or better yet, left to naturally detach on its own within seven to ten days.

Additional nonsurgical treatment options

In the past, radiotherapy or antiblastic therapy with intralesional bleomycin were also used to treat warts. However, their serious side effects mean neither are in use today.
Studies have recently been published regarding the use of topical imiquimod in the treatment of warts. Imiquimod is considered a modulator of the immune response that can heighten defenses against HPV viruses through interferon production. Topical imiquimod is available under the commercial name ‘Aldara’, and is registered for the treatment of condylomata acuminata (genital warts) and superficial basal cell carcinomas. Aldara is particularly expensive and is not suitable for the treatment of plantar warts.
Even more recently, literature on photodynamic therapy as a treatment for plantar warts has come to light. Using a photosensitizer and 630 nm light, photodynamic therapy works by destroying HPV-affected cells through the mechanism of oxygen free radicals. While already widely used to destroy skin cancers, photodynamic therapy has yet to be validated for the treatment of warts although it has shown promising results in early studies.

Surgical treatment options

The main surgical forms of wart removal today are:

Thermal destruction through:

• diathermocoagulation
• laser therapy
• cryotherapy

Surgical destruction using:

• scalpels
• curettes

The thermal destruction of warts by temperature increase is achieved through:

• diathermocoagulation
• laser therapy

Or, by destruction of the wart by lowering the temperature can happen with:
cryotherapy with liquid nitrogen (- 196°C).
However, it is important to note that neither hyper- or hypothermia treatments are actually suitable for wart removal due to heat propagation. Through conduction, heat propagates in all directions which can cause thermal necrosis in tissue beyond the lesion that is being treated. In the case of using hypothermia to remove warts, there are risks of destroying the dermis, impairment of nerve endings and vascular damage.

Destruction through temperature increase

The drawbacks of diathermocoagulation or laser therapy interventions are:

• significant thermal destruction of adjacent tissues
• post-operative pain, and slow healing leading to an increased risk of infection
• scarring by dermal fibrosis
• HPV virus DNA leaking into the environment through vapors during treatment

Destruction through temperature decrease

Cryotherapy

Rapid temperature lowering produces effects very similar to those treatments involving heat. In particular, cold propagation is even more damaging to the tissues near to the lesion than hyperthermia is.
The drawbacks of liquid nitrogen (- 196°C) treatment for plantar warts are:

• persistent pain
• formation of blisters and then ulcers
• slow healing
• increased risk of infection
• significant thermal destruction of the dermis with scarring
• damage to nerve endings with prolonged or permanent loss of sensation
• formation of doughnut warts, where a new, peripheral, circular wart surrounds a preexisting wart

Scalpel wart removal

The decision to operate on one or more plantar warts is usually due to the fact that the patient is in a hurry to resolve the problem. It should be noted that surgery is not recommended to remove mosaic or periungual warts.
In theory, wart surgery can be performed with a scalpel or curette (sharp spoon).

In reality, scalpel surgery is an unsuitable procedure for removing warts.
Scalpel surgery is performed under local anesthesia to remove the wart, followed by suturing with non absorbable stitches.

By using the scalpel, portions of the dermis that are not wart sites are also incised and removed, and if viral particles are spread during the procedure, it is easy for the wart to recur.
Another drawback of scalpel surgery is bleeding, which will be particularly intense at the plantar site. To stop the bleeding, the surgeon is often forced to assist hematosis with diathermocoagulation, but this can cause tissue necrosis, delays in healing and an increased infection risk.
Scalpel surgery for wart removal is therefore not recommend due to:

• postoperative pain
• scarring
• risk of HPV spreading
• high recurrence rate of wart
• immobilization of the patient for a few days
• increased risk of infection

Curettage wart removal

Curettage is the surgical procedure of choice to remove plantar warts. The procedure is as follows:
the part to be treated is disinfected and anesthesia is administered directly into the dermis below the wart. Either carbocaine or analogs without adrenaline anesthesia will be used. Anesthesia with adrenaline is not necessary due to the minimal bleeding the surgery causes. Local anesthesia is performed with insulin needle, in the dermis directly below the wart

After ensuring the anesthesia is working, the surgeon will choose a sterilized, oval cutting spoon that matches the size of the wart. The spoon is placed near the wart and, using the spoon’s sharp edge, firm pressure is applied in order to penetrate the spoon below the wart.

Once penetrated, the wart is disconnected at the periphery from the surrounding tissues and, by forcing the spoon upward, the entire body of the wart is extracted.

Once the wart has been extracted, a small, bleeding crater about the size of the wart will remain. To stop the bleeding, the patient should be placed on their stomach (if they are not already) and the leg bent to 45°.
A cotton swab soaked in 40% aluminum chloride hexahydrate solution and mounted on a wooden rod is inserted into the crater. In a few seconds, both hemostasis by protein coagulation and sterilization of the small wound have occurred.

The wound can then be medicated with PEG Ointment, and covered with cotton gauze held in place by plaster.
The patient can now put their shoe back on and walk normally. The only limitation is that the patient must not drive for at least two hours until the anesthesia has worn off and all sensation has returned to the foot.
At home, the patient should change the dressing by applying PEG Ointment and a cotton gauze every morning and evening.
Dressing the area and ensuring the wound does not come into contact with water should be continued for four to five days, after which point there is no need to dress the wound. Any residual crusts on the area will spontaneously clear in about 15 days.
A follow-up visit is recommended one month after surgery to assess the likelihood or lack thereof of recurrence.
The advantages of curettage wart removal are:

• minimally invasive surgery
• minimal destruction of surrounding healthy tissue and dermis
• pain limited to anesthesia injection
• infrequent recurrences
• very low infection risk
• rapid healing
• no interruption to daily activities

Preventing HPV virus infection

There are no drugs or disinfectants that can prevent infection of the HPV virus.
To avoid contagion, avoid walking around barefoot in any areas that are popular with the public, such as clothing store fitting rooms. Special attention should be paid in gyms, communal showers and swimming pools. Avoiding swapping shoes with others is also a good prevention method.
Check the feet regularly and if small lumps appear, have them checked to ensure early intervention.