Association between avulsion fracture of the distal fibula and recurrent sprain in children with ankle sprain

Abstract

Category: Sports Introduction/Purpose: The incidence of ankle sprain is higher in children than in adolescents and adults. Avulsion fractures of the distal fibula, where the anterior tibiofibular ligament attaches, commonly occur with lateral ankle sprain in children. If the avulsion fracture remains ununited, it will become a subfibular ossicle (Figure), and can cause pain, instability, and recurrent sprain. However, the incidence and radiographic result of avulsion fracture, as well as the impact of the fracture on clinical outcomes, are not well-studied. The purposes of this study were 1) to clarify the incidence and union rate of distal fibular avulsion fracture with lateral ankle sprain in children, and 2) to assess the association between avulsion fracture and recurrent sprain. Methods: Patients who presented to four orthopaedic clinics were prospectively examined. Patients with a first-time inversion ankle sprain, aged from 6 to 12 years, and visiting the clinics within 48 hours after injury, were included. Patients underwent anteroposterior and lateral radiographs, and the ATFL view (Figure) at the first visit, and the incidence of avulsion fracture was assessed. The patients with avulsion fractures underwent follow-up radiographs after 8 weeks, and fracture union was assessed. Treatment was not standardized, and ranged from an elastic bandage to a non-weightbearing cast for 6 weeks. Recurrent sprain of the ipsilateral ankle was surveyed by a review of the medical record and the questionnaire that was sent to the patients regularly. Furthermore, patients were divided into 3 groups: patients with no avulsion fracture, fracture union, and fracture nonunion. The rates of recurrent sprain were compared among the groups using the chi-square test and multiple comparisons. Results: From April 2014 to August 2015, 144 ankles of 144 patients (53 female and 91 male) with a mean age of 8.8 years underwent the radiographs at the first visit. Recurrent sprain was assessed in 105 (73%) patients with a mean follow-up of 23months. The incidence of distal fibular avulsion fracture was 62% (89/144 patients). The union rate of avulsion fracture was only 17%. The overall rate of recurrent sprain was 32% (34/105 patients). The rates were 45% (5/11) in patients with fracture union and 39% (20/51) in patients with nonunion. These rates were significantly higher than that in patients with no avulsion fracture (21%, 9/43) (P=0.02). However, the rates were similar between patients with fracture union and nonunion. Conclusion: Avulsion fractures of the distal fibula were surprisingly common with ankle sprain in children, and the most of the fractures remained ununited. The rate of recurrent sprain was relatively high at a 23 month follow-up. The presence of avulsion fracture was associated with a higher risk of recurrent sprain, however achieving fracture union did not reduce the risk.