Presentation
Pain in foot and ankle after tripping.
Patient Data
Findings:
Small ankle joint effusion. Thin fragment immediately superior to the talar articular surface of the navicular bone on the lateral view of the ankle.
Questionable irregularity at the medial aspect of the anterior calcaneal process on the oblique view of the foot.
Impression:
Dorsal talonavicular ligament avulsion injury, suggestive of a midtarsal (Chopart) sprain.
Findings:
Bone marrow edema-like signal of the plantar talar head, the inferior part of the navicular bone, the anterior calcaneus with the sustentaculum tali and the posteroinferior medial talar body.
The dorsal talonavicular ligament is thickened and hyperintense with a small rim of fluid signal intensity at the distal insertion site above the navicular bone.
The dorsal calcaneocuboid ligament is also hyperintense and thickened and with it the lateral capsule or accessory lateral band.
Edema is also visible at the cuboid insertion of the short plantar ligament and higher up in the calcaneonavicular part of the bifurcate ligament.
Also, the superomedial, medioplantar oblique and inferoplantar longitudinal parts of the spring ligament complex show a higher signal than in a healthy individual.
The lateral ankle ligament complex (anterior talofibular ligament, calcaneofibular ligament, posterior talofibular ligament), the deltoid ligament and the tibiofibular syndesmosis are intact.
Impression:
Multiligament injury of calcaneonavicular, talonavicular, bifurcate and calcaneocuboid ligaments in keeping with midtarsal sprain
Findings:
CT shows mild offset at the calcaneocuboid and talonavicular joint. There are also bony avulsions at the following locations:
- superior to the talar articular surface of the navicular bone at the distal insertion of the dorsal talonavicular ligament
- at the superolateral portion of the anterior calcaneal process at the proximal insertion of the dorsal calcaneocuboid ligament
- lateral to the cuboid bone, corresponding to the distal insertion of an accessory lateral band of the dorsal calcaneocuboid ligament
Impression:
Dorsal talonavicular and calcaneocuboid ligament avulsions in the setting of a midtarsal sprain.
Key findings:
- dorsal talonavicular ligament thickened and hyperintense (red arrowhead) with bony avulsion (red arrow) visible on x-ray and confirmation on CT
- dorsal calcaneocuboid ligament hyperintense and thickened (blue arrowheads), especially the lateral accessory band visible on axial images (light blue arrowheads) also with bony avulsion injuries of the origin (blue arrow) and the distal insertion of the accessory lateral band (light blue arrow)
- the calcaneonavicular component of the bifurcate ligament also hyperintense and thickened (yellow arrowhead) with partial avulsion in the area corresponding to the proximal origin, hardly visible on x-ray and CT (yellow arrows)
- bone marrow edema-like signal in the talar head (orange star) and sustentaculum tali (yellow star) from impaction injury
- the superomedial (orange arrowheads) medioplantar oblique (light green arrowheads) and inferoplantar longitudinal (dark green arrowhead) components of the spring ligament complex are continuously visible
- the calcaneocuboid component of the bifurcate ligament (yellow arrow) looks irregular and torn
- note: only mild bone marrow edema-like signal associated with those avulsion injuries
Case Discussion
There is a discrepancy in relation to the frequency of isolated midtarsal sprain suggesting that this clinical entity is often underdiagnosed 1-3.
In addition imaging findings are often overlooked because they are subtle and lacking knowledge about injury patterns and Chopart joint anatomy on the radiological side 1,2.
Furthermore, midtarsal sprains also occur in conjunction with lateral ankle sprains, which are much more common and enjoy a higher degree of familiarity. Similar to the latter, midtarsal sprains are usually treated conservatively. The accurate diagnosis is however important, since inappropriate management or premature weight-bearing may cause instability as a cause of chronic foot pain 1.
In the visible radiograph, the tiny shell-like fragment above the navicular bone (the distal insertion site for the dorsal talonavicular ligament) points towards the diagnosis and should prompt the search for further avulsion fractures
In MRI the bone marrow edema pattern in the plantar talar head and sustentaculum tali are further immediately visible signs.
The dorsal calcaneocuboid ligament avulsion fracture at the anterior process of the calcaneus and the dorsal talonavicular ligament avulsion injury suggest inversion accompanied by plantar flexion as a mechanism. This can happen with high-heeled shoes 2.