Comparison of bone removed with reverse total shoulder arthroplasty

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device design

Background:

• Reverse shoulder arthroplasty (RSA) is a common treatment for complex shoulder pathologies.
• Implantation techniques and prosthesis design significantly influence surgical outcomes.
• Quantifying bone removal and implant contact is crucial for optimizing RSA performance.

Purpose of the Study:

• To compare bone removal and glenoid baseplate surface contact area for three different reverse shoulder prosthesis designs.
• To evaluate the impact of scapular erosion and inferior glenoid tilt on these parameters.

Main Methods:

• A computer model simulated the implantation of three RSA designs (Depuy Delta III, DJO RSP, Exactech Equinoxe).
• The model quantified bone resected (humeral and glenoid) and baseplate contact area.
• Simulations were performed on normal and eroded scapulae with and without inferior tilt.

Main Results:

• The Exactech Equinoxe removed the least humeral bone (31.7 cm³) and glenoid bone (3.3 cm³).
• The Equinoxe achieved the largest glenoid baseplate surface contact area (501.3 mm²).
• Scapular erosion and inferior tilt reduced baseplate contact and increased bone removal.

Conclusions:

• Prosthesis design significantly impacts bone preservation and implant seating.
• The Exactech Equinoxe demonstrated favorable bone conservation and contact characteristics.
• Surgical planning should consider patient-specific anatomy, including scapular erosion, for optimal RSA outcomes.