Case report: Rare case of a traumatic isolated rupture of the conoid ligament

Acromioclavicular (AC) joint injuries can involve disruption of the AC and coracoclavicular ligaments. We report a case in aprofessional rugby player of an isolated disruption of the conoid ligament with no injury to the AC and trapezoid ligaments. A 24-year-old professional rugby player fell onto his outstretched hand, injuring his right shoulder. The differential diagnosis was an AC joint injury, coracoid fracture, stress fracture of the coracoid process, or subtle clavicle fracture, which could not be diagnosed on plain film X-ray. An MRI confirmed an isolated rupture of the conoid ligament. No injury to the AC ligament or trapezoid was identified. Five weeks after the injury, the patient returned to full contact training and match play. This case demonstrates that in AC joint injuries, it is possible that the trapezoid ligament and conoid ligament are not simultaneously disrupted, and management is per a Grade II/III AC joint injury.