Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid...

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Surgical innovation

Background:

• Conventional reverse shoulder arthroplasty (RSA) designs are linked to scapular notching, prosthetic instability, and reduced shoulder mobility.
• Metallic lateralization in RSA can increase torque at the baseplate-glenoid interface, risking component failure.

Purpose of the Study:

• To evaluate bony lateralization of RSA as an alternative to humeral medialization.
• To determine if bony lateralization avoids RSA complications without increasing glenoid component torque or shear forces.

Main Methods:

• Prospective study of 42 patients with rotator cuff deficiency undergoing bony increased-offset RSA.
• Autologous cancellous bone graft placed between the glenoid and baseplate, secured with a lengthened peg and screws.
• Clinical, radiographic, and CT assessments performed at a minimum of 2 years post-surgery.

Main Results:

• Complete graft incorporation in 98% of patients; no graft resorption, loosening, or instability observed.
• Inferior scapular notching occurred in 19% of cases.
• Significant improvement in Constant-Murley score (31 to 67) and internal rotation (86% reaching over sacrum).

Conclusions:

• Glenoid bone grafting in RSA effectively achieves lateralization, creating a "long-necked scapula" with improved functional outcomes.
• Bony increased-offset RSA demonstrates low rates of scapular notching, instability, and improved shoulder contour and rotation.
• Bony lateralization maintains the prosthetic center of rotation, reducing torque on the glenoid component compared to metallic lateralization.