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Morton Neuroma: Treatment
Updated: May 9, 2008
Treatment
Medical Therapy
The biomechanical goals of nonsurgical management are to reduce forefoot compression and to eliminate the effect of intermetatarsal ligament tension. In theory, this decreases the overall pressure on the nerve and allows it to function more normally. Shoe modifications are simple to understand but may be objectionable to some patients. High-heeled and narrow shoes should be avoided. The use of a metatarsal pad orthotic device can help keep pressure off the nerve.13
The literature is conflicting regarding the success rate for nonsurgical management, but a reasonable estimate would be that 20-30% of patients would obtain either total resolution of symptoms or improvement to a satisfactory level with footwear modifications and restrictions.
Corticosteroid or local anesthetic injections may be helpful, especially when coupled with the aforementioned shoe modifications. Using 2 mL of corticosteroid with 1 mL of Marcaine in the same syringe, the injection should be given from the dorsal direction. Do not inject into the superficial subcutaneous tissue, so as to avoid steroid-induced skin necrosis. Injections should not be used indiscriminately, because the injection itself is associated with morbidities.
Surgical Therapy
Current surgical care for Morton neuroma involves a few different options for either decompressing or resecting the nerve. The first consideration relates to the choice of surgical approach. The plantar approach is through a 3- to 4-cm longitudinal incision centered over the intermetatarsal space. This approach provides direct exposure of the nerve, since it lies plantar to the intermetatarsal ligament. The dorsal approach is through a similar-sized incision but must be taken down between the metatarsals and through the transected intermetatarsal ligament, a much less direct exposure of the nerve.14
Current trends are toward the use of the dorsal incision for primary resection because it avoids the more debilitating problems of a plantar incision if a wound complication arises. Using a small Inge retractor to widen the intermetatarsal space and apply tension to the tissues facilitates the dissection and identification of the important structures. It is prudent to inspect the area carefully to look for concurrent pathology such as lipomas, osteophytes, or inflamed bursae.
After deciding which approach to use, the definitive surgical procedure must be performed—another somewhat controversial issue. One surgical option is simply to divide the intermetatarsal ligament and thereby create a decompression of the intermetatarsal space. This may be coupled with a neurolysis, depending on the surgeon's preference. Proponents of this ideology generally believe that decreasing the stresses on the nerve is the key aspect of successful treatment and that, by preserving the nerve, some normal nerve function can return. Furthermore, by not resecting any nerve tissue, no chance of forming a recurrent (stump) neuroma exists.
A second option is to perform a neurectomy. Proponents of neurectomy believe that the key to successful treatment is elimination of the pathologic nerve tissue, while decompression would only serve to decrease the ongoing mechanical stresses on that abnormally functioning nerve. As mentioned previously, it is very important to transect the nerve as far proximal to the bifurcation as possible. Many authors promote transecting the nerve 3 cm proximal to the proximal border of the intermetatarsal ligament, since this allows proper resection of the plantar branches that may otherwise prevent the nerve stump retraction away from the weightbearing surface.15
To this author's knowledge, no prospective, controlled trials exist to compare the 2 main surgical options. A review of the case series in the current body of literature indicates that the reported success rates are similar, generally with 80% satisfactory results.
Postoperative Details
Postoperative care consists of restricting the patient to weight bearing as tolerated in a postoperative shoe, with gradual introduction of appropriate footwear as tolerated once the wound has healed and swelling has resolved.
Complications
An expected complication of the neurectomy is loss of cutaneous sensation of the interdigital skin. For most patients, this is not clinically significant. A variable amount of numbness may be present on the plantar skin, just proximal to the web space. Some authors believe that this can be more problematic and may be more likely to perform surgical decompression of the nerve (and not resect it) to avoid this complication.1
In the rare cases in which simultaneous adjacent neurectomies have been performed, the toe is affected by a more dense numbness from the metatarsal head to the tip of the digit. One study showed this increased numbness caused some awkwardness with nail care but no significant disability.16
Intractable plantar keratosis underneath adjacent metatarsal heads has been identified as a potential complication, likely as a result of altered weight-bearing mechanics due to releasing the intermetatarsal ligament.15 Wound complications are typically minor when they occur. Antibiotic treatment, debridement, or both are used as indicated.
Recurrent or persisting symptoms after surgical intervention may relate to a number of factors and can be difficult to treat. Patients who have had the decompression type of procedure may continue to have problems if the decompression was incomplete or if the nerve simply remains irritable. Those who have had neurectomy may develop a stump neuroma that may be even more painful than the original problem. Surgical intervention may be indicated should the persisting symptoms be intolerable and fail to respond to conservative measures. When operating on a recurrent neuroma, the plantar approach provides more direct access to the nerve while avoiding the scarred tissue planes of the initial dorsal approach.
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References
Weinfeld SB, Myerson MS. Interdigital Neuritis: Diagnosis and Treatment. J Am Acad Orthop Surg. Nov 1996;4(6):328-335. [Medline].
Coughlin MJ, Mann RA. Surgery of the Foot and Ankle. 7th ed. Mosby-Year Book;1999.
Thompson FM, Deland JT. Occurrence of two interdigital neuromas in one foot. Foot Ankle. Jan 1993;14(1):15-7. [Medline].
Levitsky KA, Alman BA, Jevsevar DS. Digital nerves of the foot: anatomic variations and implications regarding the pathogenesis of interdigital neuroma. Foot Ankle. May 1993;14(4):208-14. [Medline].
Mulder J. The Causative Mechanism in Morton's Metatarsalgia. J Bone Joint Surg Br. 1951;33:94-95.
Lee MJ, Kim S, Huh YM, Song HT, Lee SA, Lee JW, et al. Morton neuroma: evaluated with ultrasonography and MR imaging. Korean J Radiol. Mar-Apr 2007;8(2):148-55. [Medline].
Zanetti M, Weishaupt D. MR imaging of the forefoot: Morton neuroma and differential diagnoses. Semin Musculoskelet Radiol. Sep 2005;9(3):175-86. [Medline].
Giannini S, Bacchini P, Ceccarelli F, Vannini F. Interdigital neuroma: clinical examination and histopathologic results in 63 cases treated with excision. Foot Ankle Int. Feb 2004;25(2):79-84. [Medline].
Read JW, Noakes JB, Kerr D. Morton''s metatarsalgia: sonographic findings and correlated histopathology. Foot Ankle Int. Mar 1999;20(3):153-61. [Medline].
Iagnocco A, Coari G, Palombi G. Sonography in the study of metatarsalgia. J Rheumatol. Jun 2001;28(6):1338-40. [Medline].
Timins ME. MR imaging of the foot and ankle. Foot Ankle Clin. Mar 2000;5(1):83-101, vi. [Medline].
Terk MR, Kwong PK, Suthar M. Morton neuroma: evaluation with MR imaging performed with contrast enhancement and fat suppression. Radiology. Oct 1993;189(1):239-41. [Medline].
Saygi B, Yildirim Y, Saygi EK, Kara H, Esemenli T. Morton neuroma: comparative results of two conservative methods. Foot Ankle Int. Jul 2005;26(7):556-9. [Medline].
Valente M, Crucil M, Alecci V. Operative treatment of interdigital Morton's neuroma. Chir Organi Mov. Mar 14 2008;[Medline].
Coughlin MJ, Pinsonneault T. Operative treatment of interdigital neuroma. A long-term follow-up study. J Bone Joint Surg Am. Sep 2001;83-A(9):1321-8. [Medline].
Benedetti RS, Baxter DE, Davis PF. Clinical results of simultaneous adjacent interdigital neurectomy in the foot. Foot Ankle Int. May 1996;17(5):264-8. [Medline].
Further Reading
Keywords
interdigital neuroma, interdigital neuritis, forefoot pain, forefoot paresthesias, forefoot numbness, foot pain, Inge retractor, neurectomy, plantar keratosis
Treatment: Morton Neuroma