A Lisfranc injury involves damage to the midfoot, specifically affecting the Lisfranc joint complex. This type of injury can range from a seemingly simple sprain to more severe fractures and dislocations of the bones in the middle of the foot. Recognizing and properly diagnosing a Lisfranc injury is important because, if left untreated or misdiagnosed, it can lead to long-term complications such as chronic pain, instability, and even the collapse of the foot’s arch.
The Lisfranc Joint Anatomy
The Lisfranc joint complex is a group of bones and strong ligaments located in the midfoot, connecting the forefoot to the hindfoot. This complex includes the five long metatarsal bones and a cluster of smaller tarsal bones: the navicular, cuboid, and three cuneiform bones. These bones form the tarsometatarsal (TMT) joints.
The Lisfranc ligament is a key structure within this complex. This ligament connects the medial cuneiform bone to the base of the second metatarsal bone, providing stability to the midfoot arch. Unlike other metatarsals, there is no direct ligament connecting the first and second metatarsals, making this area vulnerable to injury. The arrangement of these bones, with the second metatarsal base recessed like a “keystone” between the cuneiforms, contributes to stability.
High-Impact Incidents
High-impact incidents cause severe and complex Lisfranc injuries due to the immense energy involved. These scenarios result in significant displacement of bones, multiple fractures, and extensive soft tissue damage.
Motor vehicle accidents are a common cause of high-energy Lisfranc injuries. In these crashes, the foot can be forcefully pushed against the floorboard or dashboard, transmitting significant force through the midfoot. This can lead to dislocations and fractures as the bones are shifted from their normal positions.
Falls from significant heights also result in severe Lisfranc injuries. Landing awkwardly on the foot can generate axial loads and twisting forces that overwhelm the midfoot’s structural integrity. Direct crushing injuries, such as a heavy object falling onto the foot, can cause damage to the bones and ligaments in the Lisfranc complex.
Twisting and Falling Injuries
Common causes of Lisfranc injuries involve twisting or indirect forces applied to the foot. Even seemingly minor incidents can lead to significant damage if the forces disrupt the midfoot structure. These injuries are often initially mistaken for a simple foot sprain, which can delay proper diagnosis and treatment.
Athletic activities contribute to Lisfranc injuries. For instance, football and soccer players are at risk when their foot is planted and flexed downward, and another player lands on the back of their heel. This mechanism can twist or compress the midfoot, leading to ligament tears or bone displacements. Other sports involving sudden changes in direction, pivoting movements, or direct impacts to the foot, such as basketball, gymnastics, and ballet, pose a risk.
Beyond sports, everyday missteps and falls can cause these injuries. Missing a step on stairs, stumbling, or twisting the foot awkwardly while walking on uneven surfaces can generate the forces to injure the Lisfranc joint. While the initial trauma might seem minor, the resulting damage to the Lisfranc complex can be significant, leading to pain and difficulty bearing weight.
Biomechanical Factors
Lisfranc injuries occur due to biomechanical forces that disrupt the stability of the midfoot. These mechanisms can involve axial load, twisting, or direct impact, leading to sprains, fractures, or dislocations. The foot’s position during the incident plays a role in how these forces affect the Lisfranc joint.
One common mechanism is an axial load combined with plantarflexion, where the foot is pointed downwards. This occurs when a person falls onto a foot that is already pointed, such as stepping into a hole or falling from a horse with the foot caught in a stirrup. The force is transmitted along the length of the foot, driving the metatarsals out of alignment from the tarsal bones.
Twisting or rotational forces are another cause. This happens when the forefoot twists relative to the hindfoot while the foot is fixed, seen in athletes whose foot gets caught or stepped on during a play. The rotational stress can tear the Lisfranc ligament and other surrounding ligaments, destabilizing the midfoot. This type of injury can result in the metatarsals being displaced dorsally or laterally.
Direct impact to the midfoot, such as a heavy object falling on it, causes Lisfranc injuries. The pressure from a direct blow can crush bones and rupture ligaments within the joint complex.