Acromion fractures after reverse shoulder arthroplasty occur in predictable clusters

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Acromion and scapular spine fractures (ASFs) occur in 3.9% of reverse total shoulder arthroplasty (RSA) cases.
• Fracture location significantly impacts nonoperative treatment outcomes, with medial fractures faring worse.
• Precise fracture localization is crucial for effective management of post-RSA ASFs.

Purpose of the Study:

• To precisely characterize the location of acromion and scapular spine fractures (ASFs) following reverse total shoulder arthroplasty (RSA).
• To utilize 3-dimensional computed tomography (CT) reconstruction for detailed fracture mapping.
• To inform future implant design and treatment strategies for post-RSA ASFs.

Main Methods:

• Retrospective review of 40 patients with post-RSA ASFs from institutional repositories.
• 3D CT reconstruction and segmentation using Mimics and 3-Matic Medical software.
• Classification of fracture locations using the modified Levy classification on normalized bone models.

Main Results:

• The study analyzed 40 patients (median age 76, 80% women) with post-RSA ASFs.
• Fracture distribution showed prevalence in lateral locations, with Type I (29%), Type IIa (26%), Type IIb (23%), and Type III (21%) zones.
• No fractures were observed in the Type IIc zone, suggesting it may not be a distinct fracture zone.

Conclusions:

• ASFs after RSA consistently occur within four predictable clusters.
• The Type IIc zone did not show any fracture clustering.
• This detailed understanding of ASF distribution is vital for developing improved implants and fixation devices.