A Guide To Endoscopic Decompression For Intermetatarsal Neuromas
When conservative measures fail, endoscopic decompression may provide pain relief of Morton’s neuroma. This author provides key diagnostic pearls, imaging insights and surgical tips.
There are many causes of intermetatarsal neuroma pain or generalized pain in the plantar forefoot area. The common source of such relentless pain is a peripheral nerve affliction, which may affect one or more digital plantar nerves as they course through the intermetatarsal spaces.
Morton’s neuroma is a benign lesion or enlargement of the third common digital branch of the medial plantar nerve. The neuroma is located between and is often located distal to the third and fourth metatarsal heads.
Classically, the nerve passes underneath the deep transverse intermetatarsal ligament on its plantar aspect. There are other structures that also pass through along with the nerve. These structures are the third plantar metatarsal artery, vein and the tendon slip from the third lumbrical muscle. This muscle inserts into the extensor hood apparatus on the medial aspect of the fourth toe.
In addition to the third intermetatarsal space, an intermetatarsal neuroma may also occur in other locations such as the second intermetatarsal space but rarely within the fourth or the first. It is important to note that intermetatarsal neuromas do occur bilaterally and one must treat them accordingly.
Key Diagnostic Pointers
The most common location for Morton’s neuroma is the distal third intermetatarsal space. It occurs more frequently in women than in men and affects those ranging in age from 18 to 60. The patient is likely to be overweight.1 In moderate cases, the patient describes the pain as a sensation of walking on a wrinkle or a lump in the sock or shoe.
During the physical examination, you may note some swelling of the plantar metatarsal surface or sulcus in comparison with the contralateral foot. It is clinically prudent to pay attention to the splaying of adjacent toes. If the neuroma is large enough, the adjacent toes may be forced to spread apart on weightbearing.
One can best diagnose Morton’s neuroma by simply listening to the patient’s symptoms. Patients have described the pain from Morton’s neuroma as sharp, dull or throbbing. However, it classically manifests as a paroxysmal burning sensation similar to “walking on a hot pebble.” The pain is most often localized in the third and fourth plantar metatarsal heads, but may radiate to distally into adjacent toes, especially the fourth, transversely to adjacent metatarsal heads. Pain may also manifest proximally up the leg to the knee and, in rare instances, as high as the hip.
Walking in shoes significantly exacerbates the pain and patients report relief to a degree after removing the shoes. A characteristic sign of painful Morton’s neuroma is one’s desire to remove the shoes, rub the forefoot and flex the toes. This usually provides immediate relief though it is transient.
One can reproduce pain by squeezing each intermetatarsal space in a dorsoplantar direction at or distal to the metatarsophalangeal joints. One must differentiate local tenderness from arthritic type pain and/or stress fractures. Mulder’s sign is positive when lateral compression of the forefoot combined with plantar and dorsal pressure produces a silent, palpable and sometimes painful click in the affected intermetatarsal space.2