Os Acromionale

                                  Os Acromionale (Unfused Acromion)

Dr.Senthilvelan

Consultant Orthopaedic Surgeon

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Contact 9566222533/nexusortho@yahoo.com

                                                       Diagrammatic representation Unfused Acromion (Os Acromionale)

The acromion is the bone which can be felt prominently on top of the shoulder. This bone develops as four different parts from childhood. These fuse together (join) to form the definitive acromion by the age of 25 ¹

The parts of ossification are called Pre acromion, Mesoacromion, Metaacromion, and Basiacromion.

Sometimes these parts do not fuse completely leasing to condition called Os Acromionale. Most of times these are asymptomatic. But some patients experience pain secondary to motion at unfused site leading to arthritic changes. There also could be impingement secondary to unfused fragment.

This can present a clinical picture similar to subacromial impingement but with more tenderness over acromion.

                                          Axillary lateral view showing evidence of Os Acromionale

Investigations include X-rays, specifically Axillary lateral view.

Treatment

Initially Pain killers, physiotherapy, are tried. Injection directly into Osacromionale unfused site is then done, which can be both of both diagnostic and therapeutic value.

Surgery

Surgery is indicated if above measures fail.

For larger fragments Fixation and fusion of fragments are done either open or by arthroscopic method

If the unfused fragment is small then it can be excised arthroscopically.

1. Park GP, Lee JK, Phelps CT. Os acromiale associated with rotator cuff impingement: MR imaging of the shoulder. Radiology 1994; 193:255-257