"Floating-socket" total shoulder replacement: anatomical, biomechanical, and surgical rationale

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Materials Science

Background:

• Current shoulder prostheses can be limited by mechanical impingement and may not fully replicate natural glenohumeral motion.
• Developing implants that provide a greater range of motion and superior component fixation is crucial for improving functional outcomes in shoulder replacement surgery.

Purpose of the Study:

• To introduce and evaluate a novel "floating-socket" total shoulder replacement prosthesis.
• To assess the biomechanical advantages and clinical performance of this new implant design, focusing on range of motion and component fixation.

Main Methods:

• Development of a "floating-socket" prosthesis featuring a nondislocatable, dual spherical bearing system with offset centers to create a "floating fulcrum."
• Testing of the prosthesis in a chimpanzee model and six clinical cases.
• Construction of the device using Cobalt-Chromium-Molybdenum alloy and RCH-1000 polyethylene to prevent metal-on-metal contact.

Main Results:

• The prosthesis demonstrated a range of motion exceeding anatomical limits, with motion limited by soft tissues rather than mechanical impingement.
• Experimental and clinical results showed superior fixation strength for both glenoid and humeral components.
• The prosthesis exhibited functional adaptation without fracture of the fixturing bone or prosthetic dislocation in all tested cases.

Conclusions:

• The "floating-socket" total shoulder replacement offers a biomechanically advantageous design for improved glenohumeral motion.
• The prosthesis provides superior component fixation and demonstrates safe clinical performance, with no observed bone fracture or dislocation.
• This novel implant concept holds promise for enhancing outcomes in shoulder arthroplasty by allowing natural soft tissue constraints to guide motion.