Os Acromiale: Current Concepts in Anatomy, Diagnosis, and Management.

Os acromiale is a developmental anomaly resulting from the failure of fusion of acromial secondary ossification centers. Although often an incidental finding, it may occasionally be associated with shoulder pain, functional limitation, and other shoulder pathologies. Despite its relatively common occurrence in the general population, the clinical significance and optimal management of os acromiale remain subjects of ongoing debate. The acromion develops from the pre-, meso-, and meta-acromion centers, which typically fuse during adolescence or early adulthood. Failure of fusion most commonly occurs between the meso-acromion and meta-acromion, with reported prevalence varying across studies. Diagnosis is primarily clinical and radiological, with the axillary lateral radiograph being the most sensitive initial tool. Magnetic resonance imaging and single-photon emission computed tomography (CT), when combined with CT, are reserved for assessing fragment stability and associated soft-tissue pathology. Initial management typically starts with a conservative treatment period of variable duration before considering further interventions. Surgical treatment may be considered in patients with persistent symptoms despite prolonged conservative therapy, with fragment excision, acromioplasty, or internal fixation representing the most widely studied techniques. However, no single gold-standard technique has been established. Os acromiale is a common anatomical variant whose direct contribution to shoulder dysfunction is not always clear. Diagnosis requires a meticulous "exclusion-based" approach to ensure the fragment is the true pain generator. While conservative treatment remains the first-line approach, surgical intervention can provide satisfactory outcomes in selected symptomatic cases. Given the inconsistent clinical outcomes and high complication rates associated with some stabilization techniques, surgical intervention should be approached with caution and tailored to fragment size and patient demand. However, a universally accepted management pathway has yet to be established.