Isolate and irreducible radial head dislocation in children: A rare case of capsular interposition

Background: Radial head dislocation with no associated lesions, is a relatively uncommon injury in children. In this case report, it is reported a case of anteromedial locked radial head dislocation in children, and we discuss its clinical presentation and pathogenetic mechanism of injury. Case presentation: An 8-year-old girl fell off on her right forearm with her right elbow extended in hyperpronation. An isolated radio-capitellar dislocation was identified with no other fractures or neurovascular injuries associated. Elbow presented an extension-flexion arc limited (0°-90°), and the prono-supination during general anesthesia shows "a sling effect"from maximal pronation (+ 55°) and supination (+ 90°) to neutral position of forearm. The radial head dislocation was impossible to reduce and an open reduction was performed using lateral Kocher approach. The radial head was found "button-holed"through the anterior capsule. The lateral soft tissues were severely disrupted and the annular ligament was not identifiable. Only by cutting the lateral bundle of the capsule was possible to reduce the joint. At 50 moths follow-up, patient presented a complete Range of motion (ROM), complete functionality and no discomfort or instability even during sport activities. Discussion and conclusion: It is important to understand the pathogenic mechanisms of locked radial head dislocation in children. Some mechanism described are the distal biceps tendon or the brachialis tendon interposition. However even the anterior capsule can hinder reduction. A characteristic "sling-effect"of the forearm could be pathognomonic for capsular button-holing. Surgical release of the capsular bundle sometimes is the only way to reduce the dislocation and obtain a good outcome.