Figure 1. Anteroposterior view.
Figure 2. Lateral view.
Figure 3. Mortise view.
Figure 4. Axial CT showing the pattern of ankle fracture.
An 11-year-old girl presents to the emergency department with severe left ankle pain after twisting her ankle and falling while running earlier in the day. On physical examination, the skin on her left ankle is intact with mild swelling over the medial and lateral aspects of the ankle. Ankle range of motion is limited due to pain and swelling. Radiographic series of the left ankle is ordered (Figures 1-3). For a better look at the fracture elements, an axial computed tomography (CT) image is ordered (Figure 4).
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Ankle fractures account for only 5% of pediatric fractures and approximately 15% of pediatric ankle fractures involve growth plates.1 It is important to identify these fractures, however, as physeal injuries can cause growth arrest leading to leg length discrepancies and angular deformities of the leg.1
Certain fracture patterns are more likely to cause growth arrest. Most epiphyseal fractures are categorized by the Salter-Harris classification.2 For instance, growth arrest is very unlikely after Salter-Harris (SH) I and II fractures but can be as high as 56% in patients who have had closed reduction after SH III and IV fractures. An SH III fracture line traverses the physis and exits out of the epiphysis. An SH IV fracture passes through the epiphysis, through the physis, and exits out of the metaphysis.1,2
Tillaux fractures are Salter-Harris III fractures through the anterolateral aspect of the distal tibia epiphysis. Tillaux fractures are seen in children nearing skeletal maturity or just before the physis closes. Triplane ankle fractures are Salter-Harris IV fractures with sagittal, coronal, and transverse components. Triplane fractures can look like Tillaux fractures on an anteroposterior radiograph but can be distinguished by the Salter-Harris II vs IV components on a lateral radiograph.1,2
Computed tomography imaging is necessary for suspected triplane ankle fractures for preoperative planning as radiographs may fail to show all fracture fragments.1,2 The CT image of this patient shows the classic 3 pointed star or Mercedes-Benz configuration consistent with a triplane ankle fracture. Fractures with greater than 2-mm displacement require open and closed reduction with internal fixation.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopaedics for Physician Assistants.
1. Kay RD, Matthys GA. Pediatric ankle fractures: evaluation and treatment. J Am Acad Orthop Surg. 2001;9(4):268-278. doi:10.5435/00124635-200107000-00007
2. Schnetzler KA, Hoernschemeyer D. The pediatric triplane ankle fracture. J Am Acad Orthop Surg. 2007;15(12):738-747. doi:10.5435/00124635-200712000-000072.