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Bifurcate ligament

The bifurcate ligament is a strong Y-shaped ligament located on the dorsolateral aspect of the midfoot. It originates from the calcaneus and splits into two bands, anchoring onto the navicular and the cuboid bones. This structure stabilizes the Chopart (midtarsal) joint complex and prevents excessive movement between the hindfoot and midfoot.

It plays a crucial role in maintaining the lateral longitudinal arch and is considered the “key ligament” of the Chopart joint. Due to its position, it may be injured in midfoot sprains, inversion injuries, and Chopart dislocations.

Synonyms

  • Ligamentum bifurcatum

  • Chopart’s ligament

  • Calcaneonavicular part of bifurcate ligament

  • Calcaneocuboid part of bifurcate ligament

Attachments

  • Origin: Dorsal surface of the anterior process of the calcaneus

  • Course: Runs distally and divides into two distinct bands:

    • Calcaneonavicular band: Inserts onto the dorsolateral aspect of the navicular bone

    • Calcaneocuboid band: Inserts onto the medial aspect of the cuboid bone

  • The two bands form a Y-shaped structure supporting both sides of the Chopart joint articulation

Relations

  • Superiorly: Extensor digitorum brevis muscle and overlying skin/fascia

  • Inferiorly: Joint capsule of the calcaneocuboid and talonavicular joints

  • Medially: Talonavicular joint capsule

  • Laterally: Dorsolateral aspect of the cuboid bone

Function

  • Stabilization: Secures the calcaneus to the navicular and cuboid bones

  • Arch support: Maintains the lateral longitudinal and transverse arches of the foot

  • Joint integrity: Acts as the primary stabilizer of the Chopart joint complex

  • Motion restriction: Limits excessive inversion and abduction forces at the midtarsal joint

Clinical Significance

  • Sprains/tears: Injured in high-energy inversion or twisting trauma, especially midfoot sprains

  • Chopart injuries: Frequently disrupted in Chopart joint dislocations and fracture–dislocations

  • Chronic instability: Leads to midfoot pain, arch collapse, and functional limitation

  • Imaging role: Essential to evaluate in suspected midfoot trauma using MRI and CT

MRI Appearance

  • T1-weighted images:

    • Normal ligament: low signal (dark), well-defined band from calcaneus to navicular and cuboid

    • Tears: discontinuity or irregular thickening with intermediate to bright signal intensity

    • Adjacent fat planes: bright and sharply outline the ligament

  • T2-weighted images:

    • Normal: low signal (dark)

    • Partial tear: focal bright hyperintense signal within ligament substance

    • Complete tear: gap with fluid signal intensity between calcaneus and navicular/cuboid

  • STIR:

    • Normal: uniformly dark band

    • Pathology: bright hyperintensity indicating edema, strain, or tear

    • Useful for detecting peri-ligamentous soft tissue swelling

  • Proton Density Fat-Saturated (PD FS):

    • Normal: thin, sharply marginated low signal band

    • Tears: linear bright signal clefts through ligament fibers

    • Excellent for identifying partial disruptions and edema

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal or no enhancement

    • Pathology: enhancement of torn or inflamed fibers and surrounding synovium

    • Chronic scarring may also enhance heterogeneously

CT Appearance

Non-Contrast CT:

  • Ligament seen as a fine soft-tissue density at anterior calcaneal process

  • Difficult to delineate directly; best assessed by associated bony changes

  • Avulsion fractures from calcaneal origin or navicular/cuboid insertion may be visible

Post-Contrast CT (standard):

  • Ligament itself shows no significant enhancement

  • Adjacent capsular thickening or inflammatory changes may enhance

MRI images

Bifurcate ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Bifurcate ligament coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000