Several weeks ago in the pre-op area, I greeted a patient and started going over the planned surgical procedures we had listed on her informed consent. She was here for her second extremity surgery. We had performed peripheral nerve decompressions for her six weeks previously. She did well and wanted to have the other side done.
When I saw her, she said her fibular sesamoid was really painful and hot in the right foot (the decompressed foot). “It also has a nervy feeling,” she said. Her tarsal tunnel syndrome, diagnosed bilaterally, responded well on the right side with decompression. Sadly, she had been accurately diagnosed years before with tarsal tunnel syndrome but no one wanted to operate on her. Accordingly, she traveled from out of state to see us.
Interestingly, she happens to be a practitioner at a very large, prestigious medical university. After seeing several of her colleagues, she told me she got the story of how “we can inject the nerve with a steroid” (http://bit.ly/mU52Zw  ). Her colleagues also told her maybe we could change her orthotics or start her on gabapentin, etc.
She finally became frustrated and came for a consultation. Interestingly, she had also received a diagnosis of bilateral fibular sesamoiditis, which I put on the back burner in spite of her overwhelming nerve entrapment. I thought to myself, “Oh, that can be taken care of when she gets back into her orthoses and we address her nerve problems.”
However, on this morning, she implored me to take another look at the sesamoid. “Okay, let’s look at it,” I capitulated. She had distinct pain with plantar palpation of the fibular sesamoid in addition to great exacerbation of the pain with forced dorsiflexion of the hallux together with palpation.
Aha! It was the sesamoid. I retook X-rays, obtaining every view you can imagine. We shot more radiographs than J Lo does dressing changes in a concert. I believe our tech concocted these views just to see how the patient could contort after a nerve decompression. It was the same deal. X-rays revealed normal osseous structure, perfect position and a normal joint space on axial view.
Dammit! I wanted to see a bipartite fracture, a spur, some type of irregularity of that painful sesamoid. “There is nothing there on X-ray,” I said to myself and then repeated this reluctantly to her. I can’t tell you how badly I yearned for there to be something there in glorious radiographic black and white. Nothing!
I started thinking that because we had now given her more sensation on the plantar aspect of the foot, maybe she was just feeling the sesamoid more. Confusingly, she had a similar type of pain on the left foot, which we were about to operate on, but the pain was milder.
“Why don’t you just make an incision on the bottom of my foot and look in there?” she said perfunctorily. After much discussion, internal cortical wrestling and explaining to the patient the caveat of painful scar tissue formation, which could add to her pain, and that we might find nothing, I reluctantly agreed to open it up. “Go ahead,” she insisted.
After careful placement of an incision just between the first and second metatarsal heads, I carried blunt dissection down to the level of the transverse intermetatarsal ligament. While searching for the common plantar digital nerve in its usual place (all under loupe magnification), I found nothing nerve-like. Nerves like to do that — run in different places. Those who do a lot of nerve cases realize that it is more often the rule than the exception.
“So let’s take a look at the fibular sesamoid,” I muttered to myself. At first, I could not believe my eyes, even with the big 4x loupes extending out of them. “Found it,” I said aloud to the operative team. My partner had his loupes on and spotted it at nearly the same time. The common plantar digital nerve to the first interspace was not coursing as the big boys like Sarrafian and Netter say it should, but was running in its own tunnel right over (directly beneath) the fibular sesamoid. Big as life, it had a distinct anatomical tunnel and with dorsiflexion of the hallux, you could actually visualize the nerve being pinched by the tunnel on the sesamoid itself.
“Wow. Could some ‘sesamoiditis’ really be a peripheral nerve entrapment?” I thought to myself. You bet your axon it can. I opened the tunnel, performed gentle neurolysis of the nerve, and transpositioned it laterally into the interspace where it belonged in the first place. We had just solved the problem.
Now why is it so hard for us to come to the conclusion that a nerve entrapment can exist in a place like this? Training for one. We almost always associate pain in this area as a disorder of the sesamoid. If there is nothing radiographic, then it is inflammatory. What about the pain from hallux valgus? Much of the same can be said.
Interestingly, we have been observing more closely the nerve over the medial eminence of the first metatarsal head with loupe magnification when performing dissection for hallux valgus reconstruction. There is a very high number of these cases that demonstrate real nerve entrapment of the dorsal medial digital nerve. We routinely perform neurolysis of these and have found that in symptomatic patients with a very small orthopedic bunion deformity, there is a higher association of this entrapment.
I can hear many the cognitive gears turning, releasing that silent inner cranial noise of you raising the question: What about “Joplin’s” neuroma? Good stuff but Joplin described his entrapment of the medial digital plantar nerve, and we are talking about the medial dorsal digital nerve.
So now that you have twisted your cortical neurons around a little, doesn’t it make sense that there is a reason that the little tiny bunion really does hurt and that the monster where the hallux is touching the fifth digit does not hurt? If it were only mechanical pain or degenerative joint disease, wouldn’t the monster kill the patient and the tiny one never hurt? We are trained as “bone cutters” and not “nerve releasers” so our lenses do not always pick up what is the most apparent pathology.
The next time that very mild hallux valgus case shows up with extreme pain, lightly tap over the medial eminence and see if you can elicit a Tinel’s sign. When the patient says “that goes all the way out to the end of my big toe,” you might have a different type of fish to fry. Additionally, when that sesamoid keeps hurting and the patient says if feels “nervy,” maybe we should listen just a little more, push out against our “bubble” and think in a different parameter.
Also, if you have any free time, we are still looking for some plantar fascia cases to be uploaded at: http://www.surveygizmo.com/s3/700292/bd3b26d9e831 
Best wishes and Happy New Year.