Efficacy of corticosteroid injection versus size of plantar interdigital neuroma

The aim of this prospective study was to assess the effectiveness of a single ultrasound-guided steroid injection in the treatment of Morton's neuromas and whether the response to injection correlates with the size of the neuroma.

Forty-three patients with clinical features of Morton's neuroma underwent ultrasound scan assessment. Once the lesion was confirmed in the relevant web space, a single corticosteroid injection was given using 40 mg of methylprednisolone along with 1% lidocaine. All scans and injections were performed by a single musculoskeletal radiologist. Patients were divided into two groups on the basis of the size of the lesion measured on the scan. Group 1 included patients with neuromas of 5 mm or less and group 2 patients had neuromas larger than 5 mm. A visual analog scale (VAS) for pain (scale 0 to 10), the American Orthopaedic Foot and Ankle Society (AOFAS) score, and the Johnson satisfaction scale were used to assess patients before injection and then at 6 weeks, 6 months, and 12 months following the injection. Thirty-nine patients had confirmed neuromas. Group 1 (lesion ≤ 5 mm) included 17 patients (mean age, 30 years) (7 males, 10 females) and group 2 (lesion >5 mm) had 22 patients (mean age, 33 years) (8 males, 14 females).

VAS scores, AOFAS scores, and Johnson scale improved significantly in both groups at 6 weeks (p < .0001). At 6 months postinjection, this improvement remained significant only in group 1 with all scores (p < . 001). At 12 months, there was no difference between both groups and outcome scores nearly approached preinjection scores. At the final review, two patients in group 1 and four patients in group 2 had severe recurrent symptoms and therefore underwent surgical excision of the neuroma after they rejected the offer for a repeat injection (p = 0.6).

A single ultrasound-guided corticosteroid injection resulted in generally short-term pain relief for symptomatic Morton's neuromas. The effectiveness of the injection appears to be more significant and long-lasting for lesions smaller than 5 mm.