Should You Excise Morton's Neuroma?
Treating a Morton’s neuroma can be a delicate operation. There is currently much discussion and controversy over whether to remove an intermetatarsal neuroma or leave the nerve intact and release the deep transverse intermetatarsal ligament via a minimally invasive nerve decompression (MIND). There have not been enough studies to sway the majority of surgeons to leave the intermetatarsal neuroma and only release the ligament. Although I believe this is truly an entrapment of the nerve, I have found removing the neuroma has been quite successful. The clinical signs and symptoms of a neuroma can include sharp, dull or throbbing pain. Burning pain and sharp, shooting sensations are also common. The lateral squeeze test can elicit discomfort and sometimes one may feel a Mulder’s click. Radiographs are virtually negative but one may see tight intermetatarsal spaces. Although you may opt for other diagnostic tests such as ultrasound, MRI and CT scans, the diagnosis is usually based on clinical signs and symptoms. Diagnosing a neuroma can be difficult with the differential diagnosis of forefoot pathology including metatarsal stress fracture, capsulitis, bursitis, tendonitis, other soft tissue masses and possibly ischemia. Anatomically, the most common neuroma is within the third intermetatarsal space, which consists of the third common digital branch of the medial plantar nerve and the communicating branch from the lateral plantar nerve. Pertinent Pointers For Excising The Neuroma When excising a Morton’s neuroma, I start with a dorsal linear incision approach described by McKeever.1 The incision is approximately 3.5 cm. After making the incision, one should use a hemostat to separate subcutaneous tissues. Proceed to clamp, cauterize and cut all superficial vascular structures. Then carefully retract the structures from the field. At this time, identify and transect the superficial intermetatarsal ligament. Again using a hemostat, visualize and dissect the bulbous, white and glistening nerve mass. This is usually just distal to the deep transverse intermetatarsal ligament. One should subsequently identify, dissect and transect the digital branches. Proceed to insert an Inge Lamina spreader in the proximal intermetatarsal space. Doing so will separate the metatarsals well enough to ensure accurate proximal dissection. Note the interossei dorsal to the deep transverse intermetatarsal ligament. Using 7-inch Metzenbaum scissors, proceed to dissect soft tissues meticulously from the nerve and then transect the deep transverse intermetatarsal ligament. However, exercise caution in order to avoid transecting the lumbrical tendon plantar to the deep transverse intermetatarsal ligament. Also keep in mind that the Inge retractor is occasionally placed over the nerve structure and needs to be removed and repositioned. Once you see the nerve as it is coursing plantar to the lumbrical muscle belly, utilize a Ragnell retractor to elevate the muscle belly. Using the Metzenbaum scissors, proceed to transect the nerve. Remove it from the field and send it for pathology. The remaining portion of the nerve will retract proximally into the overlying muscle belly. While the Ragnell retractor is still in place, place a steroid trigger injection, consisting of 1 cc of Decadron, where the nerve has retracted. Perform copious irrigation. Deep space closure consists of 3.0 Vicryl. Reapproximate subcutaneous tissues with 5.0 Vicryl. Skin closure consists of a subcuticular stitch of 6.0 Vicryl followed by 6.0 Prolene simple interrupted sutures. Utilize steri strips on the ends of the 6.0 Vicryl only. This will allow drainage from the incision site when necessary. How To Deal With Complications Surgical resection of the nerve is not without complications. One may counteract a hematoma within the dead space intraoperatively with cauterizing bleeders, using Surgicel when necessary to control bleeding, and performing deep subcutaneous closure. Stump neuromas and reoccurrence of pain can be devastating to the patient. One may help prevent this with accurate proximal dissection. Digital and/or metatarsal phalangeal mechanical instability may occur if you do not ensure meticulous intrinsic dissection. Repairing a severed intrinsic tendon intraoperatively and strapping the adjacent digits postoperatively may be helpful. Patients may feel firm, palpable, adherent scar tissue within the surgical site plantarly but it usually resolves within six to eight weeks. One can minimize intermetatarsal fibrosis and adherent scar formation by applying pressure over the incision site with moleskin, using topical skin scar reducers and emphasizing early physical therapy. A minimally invasive nerve decompression may also have postoperative complications. One should watch out for postoperative web space maceration. I have also noted a significant increase of forefoot contusion postoperatively compared to the excision. Is this from the severing of the vascular structures or from releasing proximal muscle belly fibers? It may be a combination of both. In Conclusion Various new surgical techniques, such as minimally invasive nerve decompression, have emerged in recent years for the treatment of intermetatarsal neuroma. While I have found that using a minimally invasive nerve decompression technique can reduce the length of the scar, recovery time and adherent scar tissue, long-term follow-up studies are needed. Clearly, there are still some unanswered questions. When releasing the deep transverse intermetatarsal ligament only, does this ligament regrow or reattach as suggested by Mann and Reynolds?2 Or is this scar tissue and not regrowth of the ligament, which may still create an impingement/entrapment of the nerve? Once the ligament is released, does the nerve heal and correct itself? Are the weightbearing forces of the forefoot so great that doing just a release is not enough? How does this change the overall structure of the foot or does it? With all these unanswered questions, we have yet to determine if releasing the deep transverse intermetatarsal ligament and leaving the nerve intact is a successful surgical option. I have found that surgical removal of the neuroma has been successful in my practice. However, as with all surgical procedures, success and the result of surgical removal must depend on an accurate diagnosis, meticulous operative technique and conscientious postoperative management. Dr. Gabriel is a Fellow of the American College of Foot and Ankle Surgeons. She practices in the Wood Lands, Houston and Conroe, Texas. Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board-certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark.
References 1. McGlamry, Volume II, page 313. Comprehensive Textbook of Foot Surgery. 2. Mann R, Reynolds JC. Interdigital neuroma: a critical clinical analysis. Foot and Ankle. 3(4):238-243, 1983.