We have also seen a dramatic increase of amputation neuromas within the second interspace as well. Many patients who present with second metatarsal stress syndrome, pre-dislocation syndrome, or central metatarsal overload are diagnosed with second interspace neuroma. There may be some neuroma symptoms as swelling from the joint capsule may often irritate or put pressure on the nerves. Some of these patients are diagnosed with both second and third interspace neuromas and treated by removal using two dorsal incisions . Since the second metatarsal base is locked securely within the proximal articulations at Lisfranc joint, it is difficult to separate the second interspace for an adequate proximal resection. Due to this anatomy, these will often result in secondary amputation neuromas arising after nerve resection at the distal metatarsal level.

The best approach in resolving the chronic recurrent nerve syndrome is to resect the nerve more proximally and most likely implant it into a muscle or bone. Nerves exhibit a property called “neurotropism .” When a nerve is cut, there are chemotactic factors which are transmitted from the cut end in an attempt for the nerve fibers to find its other end and repair itself. As the nerve does so, it forms a mass of randomly directed nerve tissue, and hence an “amputation neuroma ” is born. The importance of nerve implantation is the ability for the nerve to calm down and not attempt to reconnect to its other end. If the nerve can be placed within richly innervated tissues, like a skeletal muscle or bone, then this will serve to turn off these chemotactic factors, suppress the regeneration potential of the transected nerve, and increase the chances of a successful outcome [4–7]. It is best to approach this revision with surgery through a plantar incision. The incision can either be longitudinal or in a curvilinear fashion . A curvilinear incision may be better to minimize scarring within the plantar aspect of the foot since this incision is oblique to the relaxed skin tension lines versus the longitudinal incision being perpendicular to these lines. In clinical practice, there is no clear difference in how these two different incisions heal, as long as they are protected non-weightbearing for 3–4 weeks. If dealing with multiple interspaces with amputation neuromas, then a curvilinear approach will offer better medial to lateral visualization for adjacent interspaces. After the skin incision is made, it is important to dissect down to and find the deep fascia, which is the plantar fascia in this area of the foot. It is important to keep the retracted skin full thickness, keeping the subcutaneous tissues attached to the skin. There will be natural septations within the distal plantar fascia which will divide out and insert at each metatarsal-phalangeal joint. There is a separation between the bands of the plantar fascia that can easily be found, and this separation can be extended more proximally, and the nerve is often visualized immediately underneath the plantar fascia. If there is any difficulty finding the nerve in question, look more superficially than deeply. The nerve may even be found adhered to the underside of the plantar fascia. In the third interspace, it is important to look for nerve branches from both the medial and lateral plantar nerves as they will both contribute into this interspace (Figs. 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 9.10, 9.11, and 9.12).

The goal of revision is to transect this nerve as proximally as possible so it will lie within the intrinsic soft tissues of the plantar muscles of the foot. If there is adequate surrounding muscle, then this nerve can just be transected and allowed to sit within an area of the intrinsic muscle [1, 3–5, 7–10]. Other techniques involve performing an epineuroplasty and then transposing and anchoring the nerve into either skeletal bone or an adjacent muscle to make sure the regeneration potential of the nerve is suppressed. With the epineural approach, it is possible to use 6-0 Prolene to tag the cuff of thin wispy tissue and use this to mobilize the nerve and also to anchor the nerve into the muscle effectively. The skeletal bone is also richly innervated and can serve to suppress the regeneration tendency of the nerve [5, 6].

When the nerve is implanted into the muscle, several principles exist. First, sutures which are used to help mobilize the nerve should not pierce the nerve itself. The sutures should only purchase the epineural tissue to assist in nerve mobilization. Secondly, the nerves should be anchored under minimal to no tension. This will prevent further irritation to the nerve branch with movement of the foot and ankle and during ambulation. Resect the nerve as distally as possible and then loop the nerve proximally to minimize tension during implantation. And third, authors have also stated that it is ideal to place the nerve into a muscle that has the least amount of excursion [11]. On the plantar aspect of the foot, this is the transverse head of the adductor hallucis . For plantar approaches into the bottom of the foot, the intrinsic muscles are readily available, and there is no clear benefit to finding the adductor when the other muscles are all present. In the posterior ankle/leg area, this is the soleus muscle.