Comparison of Corticosteroid and Ethanol Injection Therapy in the Treatment of Morton's Neuroma

Interdigital neuroma, or Morton's Neuroma, is a painful forefoot disorder characterized by plantar pain and paresthesias radiating to toes. The condition was first described in 1845 by Lewis Durlacher as a painful "neuralgic affection" of the plantar nerve between the third and fourth metatarsals. T.G. Morton, in 1876, attributed the painful symptom complex to a "neuroma." His observation was confirmed by Hoadley who, in 1893, performed a curative excision of a "neuroma" between the third and fourth metatarsals.

Current understanding of interdigital neuroma is based on Gauthier's conclusion in 1979 that the symptom complex was a result of an entrapment neuropathy of the interdigital nerve by the overlying transverse metatarsal ligament. Presently, no definitive single etiology has been confirmed. Additional potential pathoetiologies include the aberrant anatomy of the plantar nerve in this location, trauma and extrinsic mass effect above or below the level of the transverse metatarsal ligament.(3,6) The histological appearance of the affected nerve, however, is consistent and suggests that "neuroma" is a misnomer for this condition. The nerve tissue demonstrates demyelination and deposition of amorphous eosinophilic material, but no exuberant proliferation of nerve endings characteristic of neuroma.(3)

Multiple treatments have been recommended for the management of interdigital neuroma. The usual algorithm begins with an attempt at conservative therapy consisting of shoe wear modifications and the application of a metatarsal pad. Failure of conservative management may prompt a trial of corticosteroid injections.(8) Persistent symptoms ultimately require surgical excision or division of the transverse metatarsal ligament, both of which have good long term outcomes in literature.(2,7)

Recently, serial ethanol injection therapy has been reported to be an effective alternative to surgical excision and has been widely adopted in the treatment of Morton's neuroma. Dockery et. al. reported 89% success rate in a series of 100 consecutive patients treated with 3 to 7 injections of 4% ethanol solutions with an average follow-up of 13 months. Fanucci and Masala reported a 90% success rate at 10 month follow-up after 3 to 7 injections of 30% alcohol in a consecutive series of 40 patients. However, none of these studies were performed in a randomized, double blinded fashion with adequate controls. Therefore, no scientifically valid conclusions concerning treatment efficacy can be made.

The proposed study investigates alcohol sclerosing therapy for the treatment of Morton's neuroma in a randomized, double-blinded, placebo-controlled clinical trial. The primary end point will be evaluation of patient physical function according to the standardized SF-36 questionnaire after the treatment period. Secondary end points include evaluation of pain and satisfaction levels after treatment using, respectively, a standardized and a novel questionnaire.