Ultrasound Guided Cryoablation of Morton’s Neuroma: Case Series Including Post-Ablation MRI Appearances

Abstract

Category: Midfoot/Forefoot; Other Introduction/Purpose: Morton’s neuroma (MN) is a very common compressive neuropathy of the interdigital nerve. Non- operative management is recommended initially and many therapies have been described. Cryoablation has shown promising results, however there are limited published studies in the literature. The purpose of this study was to assess the safety and efficacy of Cryoablation in patients with MN. A secondary aim was to evaluate post-procedure MRI appearances. Methods: A retrospective analysis was completed for 24 MN treated between June 2021 and September 2022. All patients had refractory MN symptoms after previous US guided steroid and LA injection within the previous year. Three patients also had refractory symptoms after prior alcohol ablation. Cryoablation was performed as a single outpatient procedure under continuous US monitoring and local anesthesia with 1 cycle for average of 2 minutes. Telephone follow up by radiology department with a 0–10 visual analogue scale (VAS) score was performed at 6 weeks and 3 months post-ablation. The patients were also encouraged to submit patient reported outcomes to a British Foot and Ankle Society (BOFAS) online scoring database as facilitated by the surgical team. Post-ablation MRI was performed to evaluate for post-procedure appearances at various intervals between 3 to 14 months. Results: 24 MN were treated. The mean size of MN treated was 12.3mm. Technical success was 100% and all patients tolerated the procedure well under local anesthesia. Mean pre-procedure VAS pain score was 8, which reduced to 1 at 6 weeks, and 2 at 3 months follow up in the treated MN. There is high patient satisfaction with 20 cases (83%) very satisfied. Four cases had various persistent symptoms and would want to have it done again (17%). Post-ablation MRI showed various bone and soft tissue changes in the ablation zone. There were two cases of fibrosis in the intermetatarsal space and one residual neuroma observed on MRI, although the patients were asymptomatic in the ablation site. No complications occurred e.g. infection, fracture or thermal injury. Conclusion: In this small series, ultrasound guided Cryoablation was deemed safe and effective treatment for MN. Clinical advantages of the procedure are good patient tolerance, single outpatient procedure, high patient satisfaction and reduced risk of scarring or residual neuroma. Further controlled prospective studies would be beneficial.