- Pediatric talus fractures are uncommon.
- The mechanism of injury in pediatric talus fractures is often an axial load on a dorsiflexed foot.
- Non-displaced injuries may be managed non-operatively with cast immobilization.
- Displaced injuries may be treated with either closed or open reduction. Internal fixation is recommended for any instability following reduction.
- The most significant complication of talus fractures is avascular necrosis (AVN) due to the non-redundant blood supply of the talus. Fractures of the talar neck are at greatest risk for AVN.
Description:Talus fractures are relatively rare injuries in children. The incidence, outcomes and rates of complications are based on small series in the literature. Because these are relatively rare injuries in children, much of the understanding of outcomes is based upon the adult literature. However, due to the cartilaginous nature of the talus in younger children, it may be more resistant to torsional forces than the adult talus. (Letts, 1980) Talus fractures encompass fractures of the neck, body, medial or lateral process, as well as osteochondral fractures. The healing potential of these fractures in higher energy injuries is of concern given the tenuous blood supply which is easily disrupted with fracture displacement. (Ribbans, 2005)
Epidemiology:While there are several small series of pediatric talus fractures in the literature, the rare nature of these injuries has precluded large epidemiologic studies. The incidence has been reported to be anywhere between 0.01% and 0.08%. (Schmidt, 1990) The most common fracture location in children is the talar neck. (Ribbans, 2005)
Clinical Findings:Patients with talus fractures generally present with pain and swelling just distal to the anterior aspect of the ankle. There is pain with or inability to weight-bear on the affected extremity. In non-displaced injuries, the presentation may be subtle with suspicion for injury based upon location of tenderness to palpation and mechanism of injury. With higher energy injuries a large degree of soft tissue damage and clinical deformity is often evident with concomitant fractures elsewhere in the foot or about the ankle commonly encountered.
Imaging Studies:As with all trauma to the foot, radiographic evaluation of a suspected talus fracture should start with three views of the foot, to include AP, lateral and oblique views (Figure 1). An improved AP image has also been described in which the foot is pronated 15 degrees and the x-ray beam angled 75 degrees from table. (Canale, 1978) Advanced imaging is often necessary to better characterize the fracture pattern or extent of injury. In the case of a comminuted fracture, CT imaging may better delineate the fracture fragments, the degree of displacement and assist in determining the need for operative intervention.
When no fracture is visualized on plain films and suspicion is high based on clinical exam, an MRI is useful to identify either a non-displaced or minimally displaced fracture as the etiology of pain. The edema pattern seen on MRI can also be helpful in delineating an occult fracture.
Talar neck fractures are classified using the system originally described by Hawkins and further modified by Canale and Kelly. (Hawkins, 1970; Canale, 1978) The classification described in the adult literature encompasses Type I-IV fracture patterns and correlates with the severity of injury and risk of developing avascular necrosis. Type I fractures are non-displaced with a very low risk of avascular necrosis. This risk increases to 41% in Type II fractures, which include displaced subluxation or dislocation of the subtalar joint. Type III fractures demonstrate subluxation or dislocation of the talar body from both the ankle and subtalar articulations and have a 91% risk of avascular necrosis. Type IV fractures involve subluxation or dislocation of the subtalar, ankle, and talonavicular joints. These severe injuries carry a rate of AVN greater than 90%. While fracture patterns generally adhere to this classification system, case reports have described variant patterns. (Yazdi, 2010)
It is important to note that talus fractures can also be seen with concomitant fractures elsewhere in the foot. Even in the setting of an obvious talus fracture, radiographs must be scrutinized to rule out additional injuries. Talar neck fractures have been described in association with compression injuries of the calcaneocuboid joint. (Godoy-Santos, 2013) Talus fracture may also be associated with fractures of the distal tibia. Hawkins Type I fractures have also been described in association with Salter Harris III fractures of distal tibia. (Prasad, 2013) In higher energy mechanisms with displaced talus fractures, associated SH IV distal tibia fractures have been described. (Nenopoulos, 2003)
Treatment:The majority of pediatric talus fractures are non-displaced and are managed non-operatively with non-weight bearing in a long leg cast for 6 to 8 weeks. Immobilization may be discontinued when there is radiographic evidence of healing. If it is difficult to assess for healing on plain radiographs, CT may be obtained to confirm osseous union. In displaced fractures, less than 5 mm of displacement and fewer than 5 degrees of malalignment on an AP radiograph is considered acceptable in children. (Canale, 1978) Non-displaced fractures treated with immobilization in the healthy child generally have a good prognosis for healing. (Jensen, 1994). Internal fixation may be advisable for non-displaced or minimally displaced fractures if there is concern of potential noncompliance with weight bearing restrictions.
When significant displacement or angulation is present, operative intervention for reduction and, in many cases, fixation is needed. Reduction should be performed under a general anesthetic after which the stability of the reduction is assessed. If the stability is questionable, internal fixation with screws is indicated. Either cannulated or non-cannulated screws may be used for fixation. The majority of the talus is articular cartilage so screws may be passed from posterior to anterior through the small non-articular portion of the bone. Approach is based on the fracture pattern and the need for both open reduction and fixation versus closed reduction and fixation. Reduction of talar neck fractures may be performed through a dorsomedial approach and fixation placed through a posterior approach. Articular fractures may require an anterolateral or anteromedial approach and internal fixation. (Figure 2) Patients are immobilized post operatively in a short leg cast or splint and kept non-weight bearing. Due to the concern for the development of avascular necrosis, patients must be followed with serial radiographs. Nondisplaced fractures should be followed for at least 18 months and more severe fracture patterns followed well beyond that timeline. (Ribbans, 2005)
Complications:Avascular necrosis of the talus may occur after fracture and is correlated with the degree of subluxation or dislocation as graded by the Hawkins classification. Talar avascular necrosis can lead to significant disability and arthrosis. Other complications associated with talus fractures include non-union, malunion, posttraumatic arthrosis, infection, neuropraxia and wound healing issues. (Jindal, 2014) Reported avascular necrosis rates after talus fractures range from 0% -66%. (Jensen, 1994; McKeever, 1943; Prasad, 2004) Even in fracture patterns with no or minimal displacement, avascular necrosis may be seen. (Rammelt, 2000; Talkhani 2000) Due to tenuous blood supply, avascular necrosis is seen most frequently in fractures of the talar neck. Avascular necrosis usually develops between several weeks to 6 months after injury. During this time period, radiographs should be scrutinized for the presence of a Hawkins sign, which is a subchondral lucency in the talar dome indicating re-vascularization of the talus. The Hawkins sign is generally seen at 6-8 weeks after injury and is a good prognostic indicator for healing.
Smith et. al. studied 29 children with talus fractures including fractures of the body, neck and head. (Smith, 2010) In this population, avascular necrosis occurred in 7% of patients. Other complications included arthrosis in 17%, delayed union in 1%, neuropraxia in 7% and surgical complications in 10%. Posttraumatic complications were found to correlate with higher mechanisms of injury, greater amounts of displacement, and more advanced age.
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