History
Both a detailed medical history and a history of 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.
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What was the exact mechanism of injury?
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Has the patient been able to bear weight since the injury?
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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 delayed diagnosis is associated with the development of Charcot joints.
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Does the patient have a history of foot surgery or prior injury to the affected foot? (This may make interpretation 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 from 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 significant limitation in 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.
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 before and after any reduction.
Assess 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 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 it 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. [4] Edema and tenderness are usually noted over the joint. Ecchymoses may develop after a few days. Vascular compromise is rare.
Following a thorough history and physical examination, including application of the Ottawa Ankle Rules, ED clinicians not only should provide a diagnosis but should rate the severity of soft tissue injuries, or the stability of fractures and dislocations, which are the pivotal decision points in guiding ED treatment, specialist referral, and the follow-up plan. [5]
Causes
Risk factors for dislocation of the foot are the same as those for any major trauma (ie, youth, alcohol intake, drug intake). However, dislocation 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.
Subtalar or peritalar dislocation
Subtalar or peritalar dislocation is a simultaneous dislocation of the talocalcaneal and talonavicular joints. Note that the talus remains in the ankle mortise. This type of dislocation typically is caused by falls from a height, MVCs, and severe twisting injuries (eg, basketball players who land on an inverted and plantar-flexed foot). [6]
Subtalar dislocation is seen with both high- and low-energy trauma. Sporting activities, commonly basketball, are often the cause of low-energy injuries. A majority of subtalar dislocations are accompanied by fractures of the hindfoot, including osteochondral fractures, calcaneus fractures, and fractures of the posterior process and tubercles of the talus. The diagnosis of subtalar dislocation is usually made on AP, lateral, and oblique radiographs of the foot or ankle. The nature of the deformity often limits radiographic positioning. [7]
These dislocations are typically medial or lateral (rarely anterior or posterior), although medial dislocation is more common (80%). Posterior dislocation may result from hyperplantar flexion. [8] Inversion injuries result in medial dislocation, and eversion injuries result in lateral dislocation. The navicular bone and the forefoot are displaced medially with a medial subtalar dislocation and laterally with a lateral dislocation. These dislocations are frequently associated with fractures of the involved bones, and a small percentage are open.
The effect of the direction of dislocation on long-term prognosis remains controversial. [2, 9, 10]
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 often result in avascular necrosis of the talus, loss of ankle motion due to traumatic arthritis, and ischemic skin loss from underlying skin pressure.
Talar dislocation with associated distal fibular fracture (Weber C) has been reported. [11] When total talar dislocation injuries occur with an open wound, the talus often has associated fractures with remaining soft tissue attachments. Initial radiographs are often obtained with nonconventional positioning. After initial reduction, CT is performed to further characterize associated injuries. [7]
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 plantarflexed foot, and crush injuries. These injuries may also be a manifestation of a developing neuropathic or Charcot joint arthropathy.
Although it was first described in the 1800s, the Lisfranc injury remains one of the most controversial topics in foot and ankle surgery. From the basic anatomy of the ligament complex to optimal diagnostic and management methods, new research both sharpens and confounds our understanding of this unique injury. [2]
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. [12] The clinician must be careful to 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 confirm that it is directly in line with the medial aspect of the second metatarsal. Any disruption is indicative of a dislocation that may have spontaneously reduced.
Lisfranc dislocations are classified according to the direction of injury in the horizontal plane; these classifications include the following.
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Homolateral, in which all 5 metatarsals move in the same direction
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Partial, or isolated, in which 1 or 2 metatarsals are displaced from the others
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Divergent, in which the first metatarsal displaces medially, with 1 or more of the other metatarsals displaced laterally
Some studies have 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 widening of the space between the middle and medial cuneiforms.
Lisfranc injuries are rare, are often missed, and may cause permanent structural deterioration of the tarsometatarsal joint, despite optimal management. Consequently, a Lisfranc injury may lead to disruption of the biomechanics of the normal foot during walking and may alter the plantar pressure distribution, which is essential for proper gait mechanics. Despite surgical management of Lisfranc injuries, the injured foot does not regain functional, radiologic, or pedobarographic levels as compared to the uninjured foot for 57 months or longer. [13]
Metatarsophalangeal (MTP) and interphalangeal (IP) dislocations
First MTP dislocations, although rare given the inherent stability of the joints, typically result from large forces. [14] These dislocations are typically dorsal and are often open.
Dislocations of the other metatarsophalangeal joints are not unusual and typically are caused by trauma. These dislocations most frequently involve 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 been described.
Isolated fracture dislocation of the navicular on the talus may occur 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 dislocations. They are frequently unstable and often require open reduction internal fixation (ORIF). An exhaustive inspection of these injuries is recommended through analysis of radiographs, CT scans, or magnetic resonance images, especially with unexposed lesions, with the goal of applying appropriate treatment and helping the patient achieve prompt recovery. [15]
