Surgical treatment of Morton's neuroma
Surgical treatment of Morton's neuroma is considered following a reasonable course of conservative care and when pain due to Morton's neuroma makes day to day activities difficult. What's a reasonable course of conservative care? The definition of conservative care will vary with each and every doctor, but a minimum of 2 months is a reasonable period of time. As you and your doctor team-up to treat your neuroma, you'll be trying different methods of care, but you'll also be building a bit of rapport. Honestly, I think a lot of the conservative care period is a period for building trust. Should you choose to have surgery performed on your neuroma, hopefully, the procedure will be performed by a doctor who you have learned to know and trust.
I mentioned in my first blog post on this topic that the treatment for Morton's neuroma has essentially remained unchanged since the condition was first described. Morton, an orthopedic surgeon, described a simple neurectomy from the dorsal (top of the foot) approach. The interdigital nerve was simply excised (cut out). One alternative to this procedure is to perform the neurectomy from the plantar (bottom of the foot) approach. There are pros and cons to both approaches. The dorsal approach preserves the sole of the foot. By doing so, a patient can walk on the foot immediately following surgery. But bear in mind that the interdigital nerve resides on the bottom of the foot. So to access the neuroma from a dorsal approach necessitates crossing a lot of anatomy that can be damaged in the course of surgery. With a plantar approach, the neuroma is very close to the bottom surface of the foot. One additional advantage of the plantar approach is the ability to transpose the nerve once excised. With a high potential for regrowth of the resected nerve, it's helpful to try to decrease this problem. With the plantar approach, you can transpose (move) the proximal stump of the nerve into an adjacent muscle belly. This transposition of the nerve does help to cut down on the formation of a stump neuroma.
It's a rare day that I do a neurectomy for Morton's neuroma, but in my hands, I've found the plantar approach to be superior. Granted, the plantar approach does force the patient to be non-weight bearing for 3 weeks following surgery. Weight-bearing on the incision would potentially result in formation of a scar on the bottom of the foot. But from a surgeon's perspective, what I'm looking to do is to get in and get out with the least amount of tissue damage. I just find the dorsal approach to be awkward in my hands. And outcomes of the plantar approach just seem to be better for me.
The reason that I no longer perform a traditional neurectomy, as originally described by Morton, is that there is a surgical option. Think about Morton's neuroma surgery from this perspective; Morton's neuroma and carpal tunnel are both nerve entrapments. In both conditions, the nerve is entrapped and irritated making the function of the nerve faulty. I will grant you the fact that the median nerve of the wrist is both a sensory and motor nerve while the interdigital nerve is purely sensory. But still, although each is caused by a nerve entrapment, the treatments are so radically different. In the case of carpal tunnel, the nerve is preserved through a procedure to release the entrapment either with an open procedure or with an endoscopic procedure. But in the case of Morton's neuroma, we just chop out the nerve? Wait a minute. We can do better than that.
EDIN - endoscopic decompression of intermetatarsal neuroma
There's a very underutilized procedure for the surgical treatment of Morton's neuroma that goes by the acronym of the EDIN procedure. EDIN stands for endoscopic decompression of the interdigital nerve. The procedure is a nerve-sparing procedure that releases the intermetatarsal ligament. The EDIN procedure is performed with three 1cm incisions and patients can walk on the foot the same day of surgery. In my experience, I've found the success of the EDIN procedure to be very good. I think the reason that the EDIN procedure has not gained favor in the orthopedic and podiatric communities is simply due to surgical dogma. Once you've been trained in the EDIN procedure, it's relatively easy to perform in under ten minutes. I have to think that the dogma surrounding the treatment of Moton's neuroma is so steadfast and ingrained in our residency training models, that the EDIN procedure has failed to yet see the light.
In addition to traditional neurectomy and the EDIN procedure, there are a few other options that are available to patients who have
failed to respond to conservative care of Morton's neuroma. We've already mentioned chemical ablation (also called neuroablation) of the nerve with absolute alcohol. Neuroablation can be performed in a number of ways including radiofrequency ablation and thermal ablation. Radiofrequency ablation is performed using an ultrasound-guided probe that emits radiofrequency. The radiofrequency results in a thermal burn (hot) that destroys tissue adjacent to the probe. Cold neuroablation is also used to treat Morton's neuroma. Under ultrasound guidance, the cold probe is placed adjacent to the Morton's neuroma and activated. The cold probe freezes the contents of the nerve, sparing the nerve sheath and destroying the contents. We've spoken earlier about why this is important and how sparing the sheath of the nerve results in fewer stump neuromas.
As a surgeon, I find the treatment of Morton's neuroma to be one of the more interesting areas of foot care. You have to ask yourself, why isn't there more progress in the treatment of Morton's neuroma? Why isn't there consensus in terms of what is the best method of treatment? I think implicit in this conversation is the fact that there's really no consensus as to what actually caused Morton's neuroma. Why does one person develop Morton's neuroma and another does not. Is Morton's neuroma purely a structural problem due to the conjoined nerve of the medial and lateral plantar nerves? Is Morton's neuroma a functional problem due to the motion of the metatarsal bones and structure of the forefoot? Maybe both structural and functional? Or is it something else that has yet to be defined in the literature. When it comes to the treatment of Morton's neuroma, I think as a professional we need to think outside the box and come up with some new and better treatment methods. And for starters, more use of the EDIN procedure would be a good place to begin.
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