The Interosseous Lisfranc Ligament (ILL)
The interosseous ligament is the most rigid and strongest component of the Lisfranc ligamentous complex, demonstrating superior biomechanical properties compared to the dorsal and plantar ligaments.
Anatomical and Biomechanical Evidence
The Lisfranc ligamentous complex consists of three distinct structures connecting the medial cuneiform to the second metatarsal base:
- Dorsal Lisfranc ligament (DLL) - smallest and weakest
- Interosseous Lisfranc ligament (ILL) - largest and strongest
- Plantar Lisfranc ligament (PLL) - intermediate strength
Structural Superiority of the Interosseous Ligament
The interosseous ligament demonstrates clear anatomical dominance 1, 2:
- Cross-sectional area: The ILL is approximately 4.5 times larger than the dorsal ligament and twice as large as the plantar ligament 2
- Thickness: Mean thickness of 13.74 ± 3.08 mm, compared to only 1.36 ± 0.42 mm for the dorsal ligament 3
- Insertional area: The ILL has the largest area of osseous attachment among all three ligaments 1
Biomechanical Rigidity
The mechanical testing data unequivocally establishes the interosseous ligament's superior rigidity 4:
- Stiffness: 189.7 ± 57.2 N/mm for the ILL versus only 66.3 ± 18.3 N/mm for the dorsal ligament
- Failure load: 368.8 ± 126.8 N for the ILL compared to 150.7 ± 33.1 N for the dorsal ligament
- Load resistance: The ILL demonstrates the highest resistance to load prior to failure when loaded parallel to its fiber orientation 1
Clinical Implications
The interosseous ligament's biomechanical dominance explains why:
- It serves as the primary stabilizer of the tarsometatarsal articulation 1
- Injury to this structure results in the most significant instability
- Surgical reconstruction efforts focus on restoring the interosseous component for functional stability 1
Important Caveat
While the dorsal ligament is amenable to direct ultrasound evaluation, this structure is not critical for stability of the Lisfranc joint 5. The interosseous ligament's deep position makes it the key structure for maintaining joint integrity, though more challenging to assess non-invasively.
The interosseous ligament's superior thickness, cross-sectional area, stiffness, and failure load collectively establish it as the most rigid stabilizing structure of the Lisfranc complex 1, 4, 2.