Os Acromiale

Introduction
An unfused secondary ossification center most common location is the junction of meso and meta acromion important to recognize os acromiale from acromial fractures Epidemiology incidence 3% bilateral in 60% Associated conditions shoulder impingement
Anatomy
3 Ossification centers meta-acromion (base) meso-acromion (mid) pre-acromion (tip)
Presentation
May present with signs and symptoms of impingement
Treatment
Nonperative observation and therapy indications mild symptoms Operative two stage fusion and acromioplasty indications symptomatic os acromiale with impingement technique direct excision can lead to deltoid dysfunction, therefore, a two stage procedure may be required. first fuse the os acromiale with a bone graft. then, in a second procedure perform an acromioplasty

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(OBQ07.156) A 22-year-old man presents with shoulder pain. Radiographs are shown in Figure A and B. What is the most likely cause? Topic

Review Topic

FIGURES: A

1. acute acromial fracture
2. type IV acromioclavicular separation
3. deltoid avulsion
4. failure of fusion between the meso-acromion and pre-acromion
5. failure of fusion between the meso-acromion and meta-acromion

PREFERRED RESPONSE ▶

DISCUSSION: By age 17, the acromion has consolidated to form three separate ossification centers along the periphery: the 1) PRE-ACROMIAL center which serves as the attachment for the coracoacromial ligament and the anterior tendinous origin of the deltoid; the 2) MESO-ACROMIAL center which anchors the middle tendinous fibers of the deltoid; and the 3) META-ACROMIAL center from which the posterior deltoid fibers originate. These three centers consolidate over the next year and ossify medially toward the clavicular facet by the time that the individual is eighteen years old (see illustration). The most common form of symptomatic os acromiale is failure of fusion between the meso-acromion and meta-acromion. Treatment is challenging and includes nonoperative management, ORIF of the fragment, open fragment excision or arthroscopic fragment decompression. All treatment modalities are fraught with benefits and disadvantages.

Illustrations: A

REFERENCES:

1. Kurtz CA, Humble BJ, Rodosky MW, Sekiya JK. Symptomatic os acromiale. J Am Acad Orthop Surg. 2006 Jan;14(1):12-9. PMID:16394163 (Link to Abstract)

2. Sammarco VJ. Os acromiale: frequency, anatomy, and clinical implications. J Bone Joint Surg Am. 2000 Mar;82(3):394-400. PMID:10724231 (Link to Abstract)

Question Authors:

Greg Galano MD, Guillem Lomas MD, Derek Moore,

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Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012

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Kurtz CA, Humble BJ, Rodosky MW, Sekiya JK. Symptomatic os acromiale. J Am Acad Orthop Surg. 2006 Jan;14(1):12-9. PMID:16394163 (Link to Abstract)
Sammarco VJ. Os acromiale: frequency, anatomy, and clinical implications. J Bone Joint Surg Am. 2000 Mar;82(3):394-400. PMID:10724231 (Link to Abstract)

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