Morton’s Neuroma (MN) appears primarily in the female sex, with a female: male ratio of 4:1 [1
]. Mean age at time of surgery is 50 years and it occurs bilaterally in 21%. It affects the third space in 66% of cases, the second in 32%, and the fourth in 2% [2
]. The most common symptom is burning pain in the plantar aspect of the foot, located between the metatarsal heads, often radiating to the two corresponding toes. Hypesthesia and dysesthesia in the affected toes are often described [3
]. Various causes of MN have already been discussed with regard to etiology like trauma [6
], bursitis [6
], anatomical variations [9
], ankle equinus [12
], metatarsus proximus [7
], pronation [5
], and entrapment by the deep transverse metatarsal ligament [6
]. The MN is usually located proximal to the bifurcation in the digital nerves, just distal to the dorsal metatarsal transverse ligament (DMTL) and consists of a thickening of the interdigital nerve [15
]. Macroscopically it has a fusiform configuration, a soft consistency and a white to yellowish appearance. Neural degeneration, epineural and endovascular hyalinization, and perineural fibrosis can be seen histologically [16
]. The diagnosis is usually made clinically. In addition, diagnostics are supplemented with imaging such as MRI or ultrasound [18
]. Dorsal-plantar (DP) X-rays of the foot are essential to investigate other causes of metatarsalgia like tarsal–metatarsal joint pathologies, Freiberg’s disease, toe deformities or metatarsal–phalangeal instabilities [19
]. A simple radiographic measurement of digital divergence might be highly helpful to facilitate the diagnosis of a MN that sometimes can be difficult to distinguish from other forefoot disorders, especially when an MRI or an experienced ultrasound examiner is not available. An increased digital divergence in the intermetatarsal space affected by MN, that can be seen radiographically, was described before [21
]. Previous studies investigated a digital divergence radiographically caused by the MN, but failed to demonstrate a significant relationship [23
Reasons might be the measuring of subjects with MN in both intermetatarsal spaces 2/3 and 3/4 [24
], no surgical histological confirmation of MN [24
], the inclusion of patients with hallux valgus, cavus foot, hammer toes and arthritic deformities [23
], different measuring methods [23
] or the lack of a 1:1 matched case-control study design [23
]. In addition, none of these studies investigated the correlation between IPA and IMA using an MRI of the MN.
To overcome these limitations, a further analysis using an adequately powered case-control matching design is warranted.
By using weightbearing DP X-rays of the foot, we aimed to review this issue and analyze, if there is an association between MN and an increased interphalangeal angle (IPA) or intermetatarsal angle (IMA) in the affected interspace. Furthermore, a potential correlation of MN size and radiographic measurement in the MRI was evaluated.