What is the proper technique for cryosurgery (cryotherapy) in treating plantar warts?

Proper Cryosurgery Technique for Plantar Warts

Pre-Treatment Preparation

Before applying liquid nitrogen, debride (pare down) the plantar wart using a surgical blade to remove hyperkeratotic tissue and improve treatment penetration. 1, 2, 3

• Ensure the treatment area is clean and dry before cryotherapy application 4
• Consider topical or injected local anesthesia if treating multiple warts or large surface areas, as plantar warts can be particularly painful during treatment 1, 2

Application Technique

Use the open spray technique with liquid nitrogen delivered via cryogun, applying treatment until a white "frost" develops on the wart and extends 1-2mm into surrounding normal tissue. 3

• Apply liquid nitrogen directly to the wart using either a cryogun spray or cryoprobe 1, 2
• Proper training is essential—both over-treatment and under-treatment reduce efficacy and increase complications 1, 2
• The mechanism of action is thermal-induced cytolysis that destroys wart tissue 1, 2

Treatment Schedule and Duration

Repeat cryotherapy applications every 1-2 weeks for optimal results. 1, 2, 4

• The British Association of Dermatologists recommends gentle fortnightly treatments for 3-4 months 1
• If no substantial improvement occurs after 3 treatments, or if warts haven't completely cleared after 6 treatments, switch to an alternative modality 2
• Most successful cases clear with 1-3 treatments: in one study, 83.5% of plantar warts cleared with a single treatment, 6% with two treatments, and 3% with three treatments 3

Expected Outcomes and Side Effects

Patients should expect pain after liquid nitrogen application, followed by necrosis and sometimes blistering—these are normal responses to treatment. 1, 2

• Overall clearance rates for plantar warts with cryotherapy range from 73-92.5% 3, 5
• Warn patients about potential scarring, particularly persistent hypopigmentation or hyperpigmentation, which is common with ablative modalities 2, 4
• Recurrence rates range from 16-22%, with most recurrences occurring within the first 3 months after treatment 2, 4, 5

Common Pitfalls to Avoid

Do not use cryotherapy as monotherapy for plantar warts without adequate debridement—this significantly reduces treatment efficacy. 1, 2, 3

• Avoid excessive treatment depth that extends into the dermis, as this increases scarring risk and can cause nerve damage in areas with superficial nerves 4
• Do not continue cryotherapy indefinitely—if there's no response after 6 treatments, the modality is ineffective for that patient 2
• Be cautious in patients with diabetes, peripheral vascular disease, or poor circulation to extremities, as they may have delayed healing 4
• Cryotherapy is contraindicated in patients with cold intolerance disorders (Raynaud's disease, cryoglobulinemia, cold urticaria) 4

Comparative Effectiveness

For plantar warts specifically, cryotherapy shows no significant advantage over salicylic acid treatment, though it may work faster in some cases. 6, 7

• A 2011 randomized controlled trial found equal clearance rates (14%) at 12 weeks for both cryotherapy and salicylic acid in plantar warts 7
• However, a 2010 study showed cryotherapy was more effective for common warts (49% cure rate) but not significantly different for plantar warts 6
• CO2 laser requires fewer sessions (median 1 vs. 3) compared to cryotherapy but has similar recurrence rates 8
• Cryotherapy causes less pain, delayed wound healing, and scarring compared to electrosurgery, with similar overall clearance rates (73% vs. 75%) 5

Post-Treatment Care

Instruct patients to keep the area clean and dry, allow scabs to fall off naturally (typically 1-2 weeks), and return for follow-up in 2-4 weeks. 4

• Patients should contact you if signs of infection develop (increasing pain, warmth, redness, swelling, discharge) 4
• After visible warts clear, follow-up is not mandatory, but patients should watch for recurrences during the first 3 months 2, 4

Documentation Requirements

Document the dose, duration, number of freeze-thaw cycles, and obtain verbal consent for each cryotherapy session. 1, 4

• Provide patients with a written information leaflet about cryotherapy 1, 4