The intermetatarsal nerve: a microscopic evaluation

Mallet Toes, Hammertoes, Neuromas, and Metatarsophalangeal Joint Instability: 40 Years of Development in Forefoot Surgery

BACKGROUND

Today's foot and ankle surgeon has an enhanced understanding of forefoot pathology and treatment options compared to surgeons who practiced in previous decades. This paper summarizes developments in forefoot surgery in the past 40 years, specifically in treatments for mallet toe, hammertoe, neuroma, and metatarsophalangeal joint instability.

MATERIALS AND METHODS

A review of the literature was conducted using the PubMed search engine, with key terms including, "mallet toe," "hammertoe," "neuroma," "metatarsophalangeal joint instability," "plantar plate," and "forefoot surgery." Chapters in major orthopaedic textbooks covering these topics were also reviewed. We then chronicled the history of the diagnosis and treatment of these pathologies, with a focus on the past 40 years.

CONCLUSIONS

There have been major advances in understanding and treating forefoot pathologies in the past four decades; however, there remain areas for improvement both in the diagnosis and treatment of these problems.

LEVEL OF EVIDENCE

Level V, meta-synthesis.

Excision of Morton's Neuroma Using a Longitudinal Plantar Approach: A Midterm Follow-up Study

BACKGROUND

Operative procedures are indicated in the treatment of Morton's neuroma (MN) when conservative therapies have been unsuccessful. A dorsal approach for neurolysis or neurectomy was strongly recommended. The aim of this case series study was to prospectively analyze the midterm clinical outcome and complications following the excision of a MN using a plantar longitudinal approach.

METHODS

Between September 2000 and January 2009, we included 44 patients (51 feet, 56 neuromas) in a prospective study treated by excision of a primary MN using a plantar longitudinal approach. The MN diagnosis was based on clinical symptoms, magnetic resonance imaging findings, and pain relief after infiltration of local anesthetics. Histological examinations were performed in all resected specimens. The patients returned for final follow-up at a mean of 54 (range = 12 to 99) months, comparing preoperative and postoperative perception of pain on a Visual Analogue Scale (VAS) and assessing clinical findings.

RESULTS

The average amount of pain, according to VAS, was 8 (range = 6-9) points preoperatively and 0.4 (range = 0-5) points at final follow-up. Complications occurred in 7.1% of interventions and scar problems in 5.2%, including delayed wound healing, hypertrophic scar formation, and inclusion cyst.

CONCLUSION

The present study shows a strong relief of pain after MN resection using a plantar longitudinal incision, coupled with a low rate of local complications. This surgical procedure seems to be a reliable choice for the excision of MN, even in cases with MN in adjacent webspaces, because it is technically simple and the plantar scar is not bothersome if properly located.

LEVELS OF EVIDENCE

Therapeutic, Level IV: Prospective, Case series.

Interdigital neuralgia

Interdigital neuralgia affects a significant number of individuals, with an average age of presentation in the sixth decade and a 4- to 15-fold increased prevalence in women. Historical descriptions date back to the 19th century. Nonoperative treatment with shoe modifications, metatarsal pads, and injections provides relief for most, but long term, 60% to 70% of patients eventually elect to have surgery. Although excision can be performed through a dorsal or plantar approach, we prefer the dorsal incision to prevent scar formation on the plantar aspect of the foot. Satisfactory results are common but not certain with reports of excellent or good ranging from 51% to 93%.

Endoscopic decompression of the intermetatarsal nerve for Morton's neuroma

Endoscopic decompression of the intermetatarsal nerve offers many advantages over other current techniques. Preliminary results in the first 40 patients have been excellent with no hematomas or infections; only three patients returned to the operating room for neurectomy.

Morton's interdigital neuroma: a comprehensive treatment protocol

One hundred fifteen patients with signs and symptoms of Mortons' interdigital neuroma were studied in an attempt to evaluate the efficacy of a staged treatment program. The first stage consisted of patient education, footwear modifications, and metatarsal head relief. The second stage consisted of a steroid/local anesthetic injection into the affected interspace. The third stage was surgical excision of the inflamed interdigital nerve. Overall, 97 of 115 patients (85%) believed that they had improved with the treatment program. Twenty-four patients (21%) eventually required surgical excision of the nerve and 23 of 24 patients (96%) had satisfactory results. The results of the staged treatment protocol were very satisfactory and patient satisfaction was high.

Histological comparison of the third interdigital nerve in patients with Morton's metatarsalgia and control patients

This study compares the histology of the plantar-digital nerve supplying the third web space in asymptomatic patients with those who have clinically diagnosed Morton's metatarsalgia. Despite several studies concentrating on the histological changes in the interdigital nerve, the relevance of these changes is a matter of contention while the exact pathological process responsible for the symptoms has not been determined. The histological findings in control patients were identical to Morton's patients with the exception of demyelination, which was more common in the Morton's group. This suggests that the characteristic nodule and fibrotic changes seen in the interdigital nerves of patients with Morton's neuroma cannot account for the symptoms and that the changes seen in the neurovascular bundle are degenerative in origin and are found in asymptomatic patients.

The diagnostic efficacy of magnetic resonance imaging and ultrasonography in Morton's neuroma: a radiological-surgical correlation

All patients operated upon for Morton's neuroma during 1991 who were examined with both magnetic resonance imaging and ultrasonography were included in this prospective study. The object of the study was to evaluate the diagnostic value of these two modalities. The preoperative diagnosis was purely clinical. Histology confirmed surgical findings. A 0.3 T scanner was used for the magnetic resonance imaging, and a 7.5 MHz linear transducer was used for the ultrasonography. The study includes nine patients. Eight neuromas were found at surgery. Of these, only five were diagnosed with magnetic resonance imaging and three with ultrasonography. This indicates that false negative diagnoses are common. At present we find these modalities of little or no value, but, with improved equipment and experience, they may become valuable.

Morton's neuroma: a microscopic evaluation

Microscopic evaluation of the interdigital neuroma is described in 24 nerves which were evaluated at six cross-section areas for size of the nerve and width of the perineural along with the fascicle diameter and the size and number of blood vessels inside each fascicle. A relationship was noted between the level of the distal edge of the intermetatarsal ligament. Cross-section that was taken at that area showed changes distally in nerve diameter, fascicle number and size, blood vessel number and size, and perineural width. These changes are consistent with the interdigital neuroma as an entrapment condition.