Expert Insights On Detecting Lisfranc's Injuries
Lisfranc’s injuries, as found at the tarsometatarsal joint, are rare, according to the literature. Only 1 percent of all fractures are found at the tarsometatarsal articulation with an incidence of one per 55,000 people per year.1 These injuries are two to four times more likely to occur among young to middle-aged men as opposed to female patients.1-3 Overall, though, the injury is still a rare phenomenon. Aitken and Poulson reviewed 82,500 fractures over a 15-year period and found only 16 cases of Lisfranc’s fractures.4
But are these injuries as rare as we think they are? The historically low reported incidence may be a function of often misdiagnosed and/or “underappreciated” tarsometatarsal injuries. Indeed, these injuries often present with subtle clinical and radiographic findings. Clearly, a strong appreciation of the complex functional anatomy and an appropriate index of suspicion are essential to detecting and treating Lisfranc’s joint injuries.
Reviewing The Anatomy Of The Lisfranc’s Joint
The Lisfranc’s joint or tarsometatarsal articulation is comprised of five metatarsal bases, three cuneiforms and the cuboid. The skeletal elements are joined together by dorsal, interosseous and plantar ligaments and the articular capsule of the joints.
Transversely, the Lisfranc’s complex forms a convex arch anteriorly. In the frontal plane, it forms a symmetric arch, with the wedge-shaped base of the second metatarsal acting as the “keystone,” affording a high degree of osseous stability in this plane.5
Metatarsals one, two and three articulate respectively with the medial, intermediate and lateral cuneiforms, which in turn articulate with each other. The architecture of the second cuneiform creates a recess of sort for the interposition of the second metatarsal base, which articulates with each cuneiform. This creates a mortise and “locks” the entire tarsometatarsal complex.6
The skeletal elements of this complex are joined together by capsuloligamentous restraints. The articular capsule is divided into the medial, central and lateral compartments. This capsule is formed by a fibrous membrane lined internally with synovium. The first metatarsal and medial cuneiform compromise the medial compartment, while the central compartment includes the second and third metatarsal and their respective cuneiforms. Finally, the lateral compartment is defined as the fourth and fifth metatarsals and the cuboid.
DePalma, Santucci and Sabetta studied 20 cadaveric feet and found significant variability exists in the course and structure of the reinforcing ligaments across Lisfranc’s joint.5 All specimens showed a ligamentous system consistent with dorsal, interosseous and plantar ligaments.
The dorsal ligaments follow a longitudinal, oblique or transverse course. The longitudinal and oblique ligaments unite the bases of the metatarsals with their respective tarsal bones while the transverse ligaments include the dorsal intertarsal and intermetatarsal ligaments.
The interosseous ligaments transversely connect the lateral four metatarsals, but are absent between the first and second. Instead, the second metatarsal is connected to the first tarsometatarsal joint obliquely from the proximal medial aspect of the second metatarsal base to the lateral distal aspect of the medial cuneiform by the Lisfranc’s ligament.1, 5-7 This ligament is the largest of the complex. The absence of a ligament connecting the first metatarsal to the tarsal bones is an inherent weakness of this complex and is responsible for the specific injury patterns you would see with these injuries. The interosseous ligaments connect the cuneiforms and cuboid, and are the most powerful attachments between these bones.