This osteological study examined 2,367 scapulae from 1,198 skeletons in the Hamann-Todd Collection to define the true general-population frequency and anatomy of os acromiale. By sampling unselected cadaveric specimens, it avoided the selection bias of prior clinical radiographic studies of symptomatic shoulders.
The clinical anchor here: os acromiale sits in roughly 8 percent of the general population, so finding it in a painful shoulder does not prove it is the cause of the pain.
The author makes a pointed critical-appraisal argument. Prior radiographic frequency estimates (1-15 percent) came from imaging symptomatic shoulders, introducing selection bias. This cadaveric collection eliminated that bias by sampling unselected skeletons.
Remember the developmental anatomy for boards: three ossification centers (pre-, mes-, met-acromial) fuse by about age 18, and any unfused fragment persisting past age 22 is os acromiale rather than a normal apophysis. The meso-acromion (failure between mes- and met-acromial centers) is the classic type.
The practical pitfall is the newly described fused os acromiale, which looks identical to a mobile ossicle on the axillary view. If you are contemplating surgery based on radiographs alone, get CT or MRI to confirm the fragment is truly unfused and mobile before committing to excision or fixation.
This osteological study examined 2,367 scapulae from 1,198 skeletons in the Hamann-Todd Collection to define the true general-population frequency and anatomy of os acromiale. By sampling unselected cadaveric specimens, it avoided the selection bias of prior clinical radiographic studies of symptomatic shoulders.
The clinical anchor here: os acromiale sits in roughly 8 percent of the general population, so finding it in a painful shoulder does not prove it is the cause of the pain.
The author makes a pointed critical-appraisal argument. Prior radiographic frequency estimates (1-15 percent) came from imaging symptomatic shoulders, introducing selection bias. This cadaveric collection eliminated that bias by sampling unselected skeletons.
Remember the developmental anatomy for boards: three ossification centers (pre-, mes-, met-acromial) fuse by about age 18, and any unfused fragment persisting past age 22 is os acromiale rather than a normal apophysis. The meso-acromion (failure between mes- and met-acromial centers) is the classic type.
The practical pitfall is the newly described fused os acromiale, which looks identical to a mobile ossicle on the axillary view. If you are contemplating surgery based on radiographs alone, get CT or MRI to confirm the fragment is truly unfused and mobile before committing to excision or fixation.