Os acromiale is a rare cause of shoulder pain. Axial radiographs allow the size of the os acromiale and its relation to the acromioclavicular joint to be judged. With CT and MRI scans and by the use of ultrasound the os acromiale can be visualised without superimposing structures, but they are not mandatory. Pain on clinical examination and pain relief after injection of a local anaesthetic allow diagnosis of a symptomatic os acromiale. Surgical intervention is reserved for patients who do not respond to conservative treatment. Treatment options include open excision of the fragment, open reduction and internal fixation, and arthroscopic decompression. To plan surgical intervention, the status of the rotator cuff and the ac joint need to be taken into account. With an intact rotator cuff and asymptomatic ac joint, arthroscopic decompression should be performed without risk of hardware complications. Open fragment excision can lead to deltoid dysfunction and should therefore be reserved for small fragments or after failed internal fixation. Open reduction and internal fixation allows both preservation of large fragments and anterior deltoid function. An anterior deltoid-off approach compromises the blood supply of the OA and a transacromial approach could be considered. Fusion techniques using cannulated screws or a figure eight tension band wiring across two Kirschner wires provide good clinical results, despite a frequent rate of non-union and the second surgical intervention for hardware removal. Bone graft, either taken from the lateral clavicle or from the iliac crest, could improve bone healing, but is rarely mandatory.

Ein Os acromiale (OA) ist selten alleinige Ursache für Schulterschmerzen. Die Diagnosestellung kann am einfachsten auf der axialen Röntgenaufnahme erfolgen. MRT, CT oder Sonographie ermöglichen eine überlagerungsfreie Abbildung, sind jedoch für die Diagnose nicht unbedingt notwendig. Eine Schmerzbefreiung nach sonografisch gesteuerter Injektion von Lokalanästhetikum in den Spalt des OA erlaubt die Diagnose eines symptomatischen OA.