Teaching Case

The patient presented with mid-foot medial pain, due to a blunt trauma two days earlier. He had no functional limitation and had no relevant medical history.

MR images showed soft tissue oedema consistent with recent trauma (fig. 1), and a complete bipartite medial cuneiform with dorsal and plantar components. Sub-cortical degenerative changes with osseous edema were observed at the plantar segment (fig. 2).

Bipartite medial cuneiform (BMC) is a rare congenital variant at the Lisfranc joint. In humans, the incidence of this finding ranges from 0.3% to 2.4% in cadaveric studies [2, 3].
Bi-partition of the medial cuneiform is a malsegmentation defect based on the prevalence of two unfused primary ossification centres (dorsal and plantar segments) that remain apart through a fibrocartilaginous/cartilaginous synchondrosis. Normally, the medial cuneiform is formed by one ossification centre. Ossification of the medial cuneiform begins at the age of 2, in this case ensuing two fragments [2, 3].
Bipartite medial cuneiform can be assigned to one of three described morphological categories:
A. Complete bi-partition, in which the medial cuneiform is divided into two upper elements, dorsal and plantar (fig. 1).
B. Incomplete bi-partition, in which the two segments are partially fused, with clefts on the medial and lateral surfaces that demark dorsal and plantar segments (fig. 4).
C. Division of the distal articular surface only.
There is a slight predilection for males, bilaterality can be expected in 60% of the cases [4].
Diagnosis through plain radiographs can be challenging due to superimposition of osseous structures, lateral view proved to be the best perspective, moreover lateral oblique view (30 °) has been suggested to aid diagnosis [2, 4, 5]. The gap in the joint space between the ossicles of the BMC and the first ray, create a rift in “E” configuration, hence the “E sign” appreciated in a sagittal/lateral views [2-4, 6], (fig. 3). Sophisticated imaging techniques such as TC or MRI have shown great impact in high detailing this finding, with the use multiplanar reconstruction (along with 3D virtual rendering) and the possibility of depicting bone marrow oedema respectively [2-5].
BMC is vastly an asymptomatic finding, symptomatic BMC can cause midfoot chronic pain due to inflammation/disruption of fibrocartilaginous synchondrosis during high impact sporting activity, or after taking a direct blow [2-5].
The main differential diagnosis to consider is the medial cuneiform fracture, which has irregular edges, and usually splits the cuneiform vertically into an anterior and posterior fragment. Isolated medial cuneiform fractures are rare, only after a direct trauma [2-6].
When a BMC becomes symptomatic, treatment alternatives range from orthotics, immobilization, corticosteroid injections, to surgical interventions including fusion and excision of bone fragments [2-5].