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Magnetic resonance imaging findings in bipartite medial cuneiform – a potential pitfall in diagnosis of midfoot injuries: a case series
© Elias et al; licensee BioMed Central Ltd. 2008
Received: 02 November 2007
Accepted: 13 August 2008
Published: 13 August 2008
The bipartite medial cuneiform is an uncommon developmental osseous variant in the midfoot. To our knowledge, Magnetic Resonance Imaging (MRI) characteristics of a non-symptomatic bipartite medial cuneiform have not been described in the orthopaedic literature. It is important for orthopaedic foot and ankle surgeons, musculoskeletal radiologists, and for podiatrists to identify this osseous variant as it may be mistakenly diagnosed as a fracture or not recognized as a source of non-traumatic or traumatic foot pain, which may sometimes even require surgical treatment.
In this report, we describe the characteristics of three cases of bipartite medial cuneiform on Magnetic Resonance Imaging and contrast its appearance to that of a medial cuneiform fracture.
A bipartite medial cuneiform is a rare developmental anomaly of the midfoot and may be the source of midfoot pain. Knowledge about its characteristic appearance on magnetic resonance imaging is important because it is a potential pitfall in diagnosis of midfoot injuries.
Case 1: Bipartite medial cuneiform
Case 2: Bipartite medial cuneiform
Case 3: Fractured medial cuneiform
Case 4: Bipartite medial cuneiform developing arthritis
The bipartite medial cuneiform was originally described by Barlow in 1942 . Subsequent cadaveric study demonstrated that the incidence of this variant is between 0.3% and 2.4% . In cases of medial cuneiform bipartition, the cuneiform bone is divided horizontally by a synchondrosis, and the plantar segment is larger. Portions of the posterior tibial and peroneus longus tendons attach to the proximal inferomedial and distal inferolateral portions of the plantar segment. The anterior tibial tendon inserts on the proximal superomedial dorsal segment and the dorsal and plantar bundles of the Lisfranc ligament attach to the respective portions of the medial cuneiform .
It is believed that the normal medial cuneiform develops from one primary ossification center. In the setting of two primary ossification centers, these may fail to fuse, resulting in bipartition. Ossification of the lateral cuneiform begins in the first year of life, followed by the medial and middle cuneiforms in the second and third years, respectively . Most cases of a bipartite medial cuneiform have been reported incidentally; however, some authors have identified and successfully treated chronic foot pain believed to be associated with a bipartite cuneiform. In two patients, one of whom was a marathon runner and the other a military recruit, excision of the dorsal segment and steroid injection into the joint have been reported as successful treatments [2, 6]. A third patient with chronic foot pain after remote trauma has reportedly been successfully treated with fixation using a trans-cortical screw .
A fracture of the synchondrosis between the two segments of a bipartite medial cuneiform has also been reported in a pediatric patient . From an imaging standpoint, it is important to identify a bipartite medial cuneiform and differentiate it from a fracture. A bipartite medial cuneiform should demonstrate smooth, well corticated margins. The two portions of the bipartite cuneiforms together are usually larger than the expected normal, or fractured medial cuneiform as for example seen in case #3. Also, we found in all cases of a bipartite medial cuneiform that the proximal articular surface of the first metatarsal bone was larger than usual.
A bipartite medial cuneiform is a rare developmental anomaly of the midfoot and has a characteristic appearance on MRI (E-Sign). Knowledge of the presence and appearance of this osseous variant is important in being able to identify this entity and to differentiate it from a fracture because this may potentially be a pitfall in diagnosis of midfoot injuries. Even in the absence of a fracture, a bipartite medial cuneiform may be the source of midfoot pain, which can be treated with various techniques, including surgery .
This study was approved by the Institutional Review Board (IRB) of the Thomas Jefferson University Hospital. Written informed consent could not be obtained in these cases since the patients are untraceable. We believe this case series contains a worthwhile clinical lesson, which could not be as effectively made in any other way. We expect the patients not to object to the publication since every effort has been made so that they remain anonymous.
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