An os acromiale can be found at the basi-acromion, meta-acromion, meso-acromion, or pre-acromion level, with a meso-acromion as the most common. The os is named for the most anterior portion on the unstable fragment.

The prevalence of os acromiale is 1% to 30%, with 42% to 61% being bilateral and a higher prevalence in the male and African American population.

Most patients with an os acromiale can be treated nonoperatively, but multiple surgical procedures have been reported in the treatment of a symptomatic os acromiale, including open or arthroscopic excision of the os fragment, open reduction and internal fixation (ORIF) with or without bone grafting, arthroscopic subacromial decompression with acromioplasty, and arthroscopically assisted reduction-internal fixation.

Open fragment excision has limited indications and is recommended for symptomatic pre-acromion with a relatively small fragment or as a salvage procedure after a failed ORIF. In the latter scenario, arthroscopic excision is probably a better option, as it has the possible benefit of less periosteal and deltoid attachment injury, possibly lending to better results than open excision.

ORIF techniques and approaches associated with the most success include those with rigid fixation and preservation of the vascularity of the os acromiale (likely the acromiale branch of the thoracoacromial artery). Even in cases of successful union, patients still may have hardware discomfort requiring hardware removal; however, there are minimal complications that arise from most ORIF cases.

Resection of the synchondrosis without excision of the entire os acromiale has shown promising results in a small number of patients with short-term follow-up and presents a novel approach to patients with a symptomatic os acromiale.