eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics

Dislocation, Foot

Author: Christopher M McStay, MD, Assistant Professor, Department of Emergency Medicine, New York University, Bellevue Hospital Center
Coauthor(s): Moira Davenport, MD, Attending Physician, Departments of Emergency Medicine and Orthopedic Surgery, Allegheny General Hospital; Martin J Carey, MD, MB, BCh, MPH, FACEM, FRCS, Program Director, Assistant Professor, Department of Emergency Medicine, University of Arkansas for Medical Sciences
Contributor Information and Disclosures

Updated: May 27, 2008

Introduction

Background

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.

Pathophysiology

Anatomy

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.

Frequency

United States

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.

International

No information is available on international injury rates.

Mortality/Morbidity

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.

Sex

The male-to-female ratio is 6:1. This differential is largely due to the higher number of young males who sustain significant trauma.

Age

Injury may occur at any age, although the more severe forms of dislocation associated with MVCs are more common in young adult males.

Clinical

History

Both a detailed medical history and a history of the events surrounding the injury or appearance of symptoms are essential in identifying the type of injury and predisposition to complicating factors.

The history should include the following questions:

• What was the exact mechanism of injury?
• Has the patient been able to bear weight since the injury?
• Does the patient have an underlying medical condition, especially a history of diabetes mellitus?
  • People with diabetes mellitus may have denervation of the foot and are prone to develop Charcot joints. Charcot joints are joints that demonstrate a grossly disorganized structure, deformity, edema, extreme hypermotility, and often remarkably little pain. Function is generally good.
  • Early, accurate recognition of foot injury is particularly important in patients with diabetes mellitus because a delayed diagnosis is associated with the development of Charcot joints.
• Does the patient have a history of foot surgery or prior injury to the affected foot? (This may make interpretations of radiographs difficult.)

In general, patients who experience dislocations of the foot have other injuries related to the mechanism of injury. A full history of the event should be obtained from the patient or prehospital caregivers. Occasionally, these injuries may occur with minimal trauma. This is especially true with athletes. The history in these cases is usually of increasing pain and edema over a few days, resulting in a significant limitation of mobility, decreased performance, or both. Often, the patient gives no definitive history of a single traumatic event. The presumed mechanism of injury responsible for each type of dislocation is discussed with that dislocation.

Physical

Examination of the foot usually reveals an obvious deformity; however, some dislocations are accompanied by substantial soft-tissue edema. The exact nature of the injury may be unclear until radiography is performed.

• Neurovascular examination is critical both prior to and after any reduction.
• Assess the vascular status. If no pulse is palpable, urgent reduction of the dislocation is required. Confirm the absence of a pulse with Doppler studies in the emergency department (ED) if possible. Mark the position of the pulse on the skin; this simple measure confirms that a pulse was taken and that it was palpable and also indicates the ideal anatomic location for reassessment. Loss of a previously palpable pulse is a sign that urgent reduction is needed.
• Perform a thorough neurologic examination of the foot.
• Check for any breaks in the skin. Check for any tenting of the skin, which may necessitate urgent reduction.
• Findings may be subtle and nonspecific in persons who present with foot pain from a Lisfranc dislocation in which no single major traumatic event has occurred.¹ Edema and tenderness over the joint are usually present. Ecchymoses may develop after a few days. Vascular compromise is rare.

Causes

The risk factors for dislocation of the foot are the same as those for any major trauma (ie, youth, alcohol intake, drug intake). However, dislocations of the foot can result from an apparently simple fall (eg, twisting one's foot in a hole in the ground when jogging).

Numerous different types of dislocations of the foot are recognized. These dislocation types are discussed below with a review of their causes as follows:

• Subtalar or peritalar dislocation
  • This is a simultaneous dislocation of the talocalcaneal and talonavicular joints. Note that the talus remains in the ankle mortise. It is typically caused by falls from a height, MVCs, and severe twisting injuries (eg, basketball players who land on an inverted and plantar-flexed foot).
  • The dislocation is typically medial or lateral (rarely anterior or posterior), although medial dislocation is more common (80%). Inversion injuries result in medial dislocations and eversion injuries result in lateral dislocations. The navicular bone and forefoot are displaced medially with a medial subtalar dislocation and displaced laterally with a lateral dislocation. These dislocations are frequently associated with fractures of the involved bones and a small percentage are open.
• Total talar dislocation
  • A rare dislocation, this injury typically results from very high-energy trauma. The talus is completely out of the ankle mortise and is rotated such that the inferior articulation points posteriorly and the talar head points medially.
  • These dislocations are commonly open and result in avascular necrosis of the talus, loss of ankle motion due to traumatic arthritis, and ischemic skin loss from underlying skin pressure.
• Lisfranc dislocation
  • Dislocation fractures of the tarsometatarsal joints are referred to as Lisfranc injuries. This type of dislocation is caused by several mechanisms, including rotational forces about a fixed forefoot, axial loading in a plantar flexed foot, and crush injuries. These injuries may also be a manifestation of a developing neuropathic or Charcot joint arthropathy.
  • Tremendous energy is usually required to subluxate or dislocate the Lisfranc joint complex. This energy frequently results in extensive soft-tissue injury. Occasionally, minor rotational injuries may cause this problem. This is particularly well described in athletes and in older patients.
  • The clinician must be careful not miss these injuries. Evaluate the alignment of the metatarsal bones with their corresponding tarsal bones on radiographs. The first, second, and third metatarsals should line up with the medial, middle, and lateral cuneiforms respectively. The fourth and fifth metatarsals should line up with the cuboid.
  • A good starting point for evaluation is to inspect the medial aspect of the middle cuneiform to be directly in line with the medial aspect of the second metatarsal. Any disruption is indicative of a dislocation, which may have spontaneously reduced.
  • Lisfranc dislocations are classified according to the direction of injury in the horizontal plane and include the following:
    • Homolateral, in which all 5 metatarsals move in the same direction
    • Partial, or isolated, in which 1 or 2 metatarsals are displaced from the others
    • Divergent, in which the first metatarsal displaces medially, with one or more of the other metatarsals are displaced laterally
  • Some studies estimated that 20% of Lisfranc injuries are missed upon initial presentation to the ED. Subtle injuries to the Lisfranc joint do occur and may be difficult to diagnose. Slight widening (2-5 mm) of the space between the first and second metatarsals may be seen, as well as a widening of the space between the middle and medial cuneiforms.
• Metatarsophalangeal (MTP) and interphalangeal (IP) dislocation
  • First MTP dislocations, although rare given the inherent stability of the joints, typically result from large forces.² These dislocations are typically dorsal and are often open.
  • Dislocations of the other metatarsophalangeal joints are not unusual and typically are caused by trauma. The dislocation is most frequently a lateral or dorsal displacement of the digit on the metatarsal head.
  • IP dislocations are less common than MTP dislocations. Most occur in the first toe as a direct result of axial loading.
• Other dislocations
  • Although very rare, other dislocations in the foot have also been described.
  • Isolated fracture dislocation of the navicular on the talus has been described. It occurs following a fall from a height and is usually treated with open reduction and internal fixation.
  • Cuboid and cuneiform fractures are sometimes associated with tarsometatarsal dislocations, but they may present as isolated fracture-dislocation. They are unstable frequently and require open reduction and internal fixation.

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