The relationship between scapular notching and reverse shoulder arthroplasty prosthesis design

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Radiology

Background:

• Inferior scapular notching is a frequent radiographic complication following reverse shoulder arthroplasty.
• Prosthesis design is a potential factor influencing the occurrence and severity of this complication.

Purpose of the Study:

• To evaluate the impact of different reverse shoulder arthroplasty prosthesis designs on the incidence and severity of inferior scapular notching.
• To compare notching rates between Tornier and Zimmer implant designs.

Main Methods:

• Retrospective review of 88 patients undergoing reverse shoulder arthroplasty with at least 12 months follow-up.
• Patients were grouped by prosthesis design: Tornier, Zimmer with nonretentive liner, and Zimmer with retentive liner.
• Notching was graded using the Sirveaux and a novel classification system.

Main Results:

• The Tornier prosthesis had a significantly higher incidence of notching (92%) compared to Zimmer designs (58%-71%).
• Tornier implants also showed significantly higher rates of high-grade notching and baseplate involvement.
• Retentive liners in Zimmer implants did not significantly alter notching rates compared to nonretentive liners.

Conclusions:

• The Tornier reverse arthroplasty demonstrated a higher incidence and severity of scapular notching than the Zimmer design at short-term follow-up.
• Differences in polyethylene morphology or glenosphere offset may contribute to the observed variations.
• Prosthesis design, alongside surgical technique, is crucial for mitigating scapular notching risk.