Dislocations of the foot are uncommon but potentially incapacitating injuries. The mechanism of injury may vary from a simple fall to a major motor vehicle collision (MVC). The foot is a complex structure, and injuries often occur in patients who sustain multiple trauma. The clinician must understand common patterns of injury and maintain a high index of suspicion in examining the appropriate radiographs to avoid missing foot dislocations.
The foot consists of 26 bones and 57 articulations. The foot is composed of 3 functional and anatomic regions. The hindfoot consists of the talus and the calcaneus. The midfoot consists of the navicular, the cuboid, and the 3 cuneiforms. The forefoot contains the 5 metatarsals and 14 phalanges.
The foot also contains numerous accessory centers of ossification that are occasionally mistaken for avulsion injuries. The presence of a smooth cortical surface and lack of associated soft-tissue edema helps to differentiate these normal variants from fractures.
The articulations between the hindfoot and the midfoot are the midtarsal or Chopart joints. These joints are the talonavicular and the calcaneocuboid joints. The articulations between the midfoot and the forefoot are termed the Lisfranc joints and consist of the 5 tarsometatarsal joints.
The subtalar joint, between the talus and the calcaneus, accounts for most inversion and eversion injuries to the hindfoot. Adduction and abduction of the forefoot primarily occurs through the midtarsal joints. Flexion and extension primarily occurs at the metatarsophalangeal (MTP) and interphalangeal (IP) joints.
All dislocations in the foot (with the exception of simple dislocations of the toes) are uncommon injuries. The most common of these injuries is a dislocation that involves the Lisfranc joint complex. The rarity of these injuries makes diagnosis difficult. A significant proportion of the more subtle dislocations are not diagnosed upon initial presentation. Dislocations through the Lisfranc joint complex are thought to have an incidence of about 1 in 50,000 persons with orthopedic trauma per year, representing fewer than 1% of all dislocations.
Dislocations of the foot are commonly associated with other significant injuries sustained during falls or MVCs. Delay in recognition of dislocations is common because of the distracting effect of the associated injuries or because of the subtle nature of these injuries. Early reduction and immobilization may reduce morbidity.
Many complications, including avascular necrosis, compartment syndrome, and degenerative arthritis, have been reported. Additionally, residual pain and loss of function is a common consequence of the complex biomechanics of the foot.
The male-to-female ratio is 6:1. This differential is largely due to the higher number of young males who sustain significant trauma.
Injury may occur at any age, although the more severe forms of dislocation associated with MVCs are more common in young adult males.
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