Radiographic Evaluation of the Normal Ankle Joint in Children and Adolescent

Abstract

Category: Ankle Introduction/Purpose: Although comparison to radiographic standards for ankle joint is critical for evaluation of syndemosis injuries, such standards are not well defined for children and adolescents. The purpose of this study was to determine the reliability of numerous radiographic measurements of the skeletally immature ankle joint, timing of ossification of medial malleolus and appearance of tibial incisura and differences in the values of radiographic measurements based on age and sex. Methods: This study included 590 subjects (0 to 15 years), who underwent ankle AP, lateral and mortise radiographs. Presence of the medial malleolus and incisura fibularis were recorded (Fig 1). Tibiofibular overlap, tibiofibular clear space, medial clear space, talar tilt, talocrural angle, relative fibular width and fibular position were measured (Fig 2). A inter- and intrareliability test was conducted before the main measurements using intraclass correlation coefficients (ICC). To determine the timing of the ossification center of medial malleolus and appearance of tibial incisura, multinomial logistic regression was used. The generalized linear model was used to estimate the radiographic measurements by age and sex. The 100-quantiles were calculated to determine the normal value of the tibiofibular clear space, tibiofibular overlap and medial clear space. Results: All radiographic measurements showed good to excellent intraobserver(ICC, 0.603–0.934) and interobserver reliability(ICC, 0.704–0.972). The timing of ossification of medial malleolus and appearance of tibial incisura between boys and girls were not different. Tibiofibular clear space on mortise view, and medial clear space on AP and mortise view significantly decreased by age. Tibiofibular overlap on AP and mortise views, relative fibular width on AP view significantly increased by age. Talocrural angle, tibiofibular overlap on AP view, tibiofibular clear space on AP and mortise views, medial clear space on AP and mortise views and fibular position were significantly larger in boys than in girls. The difference in tibiofibular overlap, tibiofibular clear space and medial clear space on mortise view of both sides was < 50% in 98.1%, 99.3%, and 100% of patients, respectively. Conclusion: Tibiofibular clear space, tibiofibular overlap and medial clear space can be parameter to assess distal tibiofibular syndesmosis or deltoid ligament injury in skeletally immature patients. For these patients, the criteria of absolute radiographic values used in adults cannot be applied, but comparison of both sides could help physicians to predict the need for additional evaluations.