Differentiating os acromiale from normally developing acromial ossification centers using magnetic resonance imaging

Area of Science:

• Orthopedic imaging
• Adolescent musculoskeletal conditions

Background:

• Acromial fusion is incomplete in adolescents (up to age 25).
• Diagnosing os acromiale in adolescents is challenging due to potential confusion with developing ossification centers.

Purpose of the Study:

• To differentiate os acromiale from developing acromial ossification centers in adolescents using MRI.
• To establish imaging criteria for os acromiale diagnosis irrespective of patient age.

Main Methods:

• Retrospective review of 128 shoulder MRIs (56 adults with os acromiale, 72 adolescents).
• Radiologists assessed interface characteristics (orientation, margins, edema) between the distal acromion and ossification centers/os acromiale.
• MRIs were analyzed blindly and retrospectively.

Main Results:

• In adolescents, 92% showed normal acromial development with arched interfaces and lobulated margins.
• 4% of adolescent cases exhibited features consistent with os acromiale (transverse orientation, irregular margins).
• Adult os acromiale cases (100%) demonstrated transverse orientation and irregular margins, often with edema.

Conclusions:

• Adolescents can present with imaging findings indicative of os acromiale.
• MRI-based imaging features are crucial for diagnosing os acromiale, regardless of patient age.