The cause of MN has not clearly been established (2, 9, 10). This confusion also leads to confusion in the choice of treatment. First of all, we need to know the reasons for the occurrence of MN to decide the treatment method. There are several anatomical explanations try to explain the cause. The most commonly known theory is compression at tunnel theory. The tunnel is anatomical box composed of two metatarsal heads, tendons and distal metatarsal transverse ligament (DTML) (4). The theory is based on compressing and pulling of interdigital nerve by DTML during walking in both the mid-stance and the heel-off stage (9). Unlike this knowledge, Kim’s anatomical study showed that; neuroma occurs more distally than DTML and does not change nerve-length with foot movements (4).
Another anatomical explanation for Morton neuroma is about neural anatomy (4). Tibial nerve divides into two medial and lateral plantar branches below medial malleolus. Medial plantar nerve also is divided to hallux digital nerve and common digital nerves for first, second and third interspace. Lateral plantar nerve forms fifth toe digital nerve and fourth interspace digital nerve. Anatomic nerve variation, present 66.2% of the cases, arises from the 4th interspace make anastomosis with the common digital nerve at 3th interspace. A bulge before bifurcation in the digital nerves just distal to DTML creates MN clinics (9).
In the light of this theories; staged treatment program began with footwear modification, progressed to steroid injection, and finally to surgical treatment (11).
Dorsal approach is more preferable because of its technically simple than plantar approach except revision for surgical treatment (5). However dorsal approach also has its own disadvantages (12, 13). Recurrent neuromas occur more at dorsal approach due to inadequate visualization of nerve tracts because of not fully transected metatarsal ligament or metatarsal heads and adjacent soft tissue swelling (3).
Recurrence after MN surgery is an undesirable outcome. Amis et al. found an anatomical cause in a cadaver study which aimed to investigate the causes of recurrence (3). They found plantarly directed nerve branches (PDNB) along the course of common digital nerves of second and third web spaces. Resected nerve stump may not move away from weight bearing area of the foot because of PDNB and this might be a cause of recurrence. Any injury to PDNB during excision of Morton neuroma may lead to formation of traumatic neuroma with similar clinical findings to Morton neuroma. In the light of revision surgery literature search is made; In revision surgery, it is not stated whether recurrence is stump-induced or traumatic PDNB-induced neuroma. Kim showed that, MN detected level of bifurcation and does not under DTML and length of DTML + interdigital nerves from the bifurcation of the common digital nerve to the anterior margin of the DTML were recorded 29,5 mm at second; 25,7 mm at third interdigital nerve and No statistical difference was found in the common digital nerve length between the foot movement position (4).
Amis stated that to prevent recurrence, after achieving a good visualization nerve must be resected at least 3 cm proximal to the deep transverse ligament because there are plantar directed nerve tetherings at 3 cm proximal to the proximal edge of DTML (3, 13). Anatomic studies showed that; mean DTML length recorded 11,7 mm and stated that MN was found to be an average of 7.5 mm beyond DTML (14). As a results Amis recommend to remove 4,92 cm (3 + 1,17 + 0,75 cm). On the other side, Kim stated that it is sufficient to remove 3 cm in total nerve resected length (4). In all of these anatomic studies; while these measurements were being made, the foot length was neglected. The length of the foot will affect the length of the nerve and therefore the length of the nerve to be excised. In our study, the mean value was found to be 2.05 and only 8 sample (10.5%) was bigger than 3 cm. Only two patients results only who had poor results; revision surgery was performed. The sizes of the samples taken in these patients were 2 and 2,1 cm. Although all diagnostic steps are applied correctly; one patient was a incorrect diagnosis as a polyneuropathy. Our results showed that our complication rate was 4,5% and revision surgery rate was 3%. Although the current literature gives revision rates of 15–50%; our cases samples were taken at a shorter size than the length suggested by the literature and our revision rates were found to be lower (15). During surgery, we removed the nerve as much as possible, regardless of foot size. It is a weak point of our study that the foot length is not specified in our study.