Posterior Flange Cyclic Loading in a Novel Total Elbow Arthroplasty

Area of Science:

• Orthopedic biomechanics
• Biomaterials science
• Surgical implant design

Background:

• Total elbow arthroplasty (TEA) is a surgical procedure to replace the elbow joint.
• The posterior flange is a critical component for the stability and function of TEA.
• Understanding the mechanical properties of TEA components is essential for improving patient outcomes.

Purpose of the Study:

• To evaluate the static and dynamic strength of the posterior flange in a new total elbow arthroplasty design.
• To assess the loosening resistance of the posterior flange under cyclic loading.
• To analyze forces on the ulnohumeral joint and posterior olecranon during simulated elbow use.

Main Methods:

• Static stress analysis was conducted on three different flange sizes.
• Failure testing involved cyclic loading of five flanges (one medium, four small) up to 10,000 cycles or until failure.
• Safety factors were calculated, and implant failure or loosening was monitored.

Main Results:

• Static testing showed safety factors of 6.6, 5.74, and 4.53 for small, medium, and large flanges, respectively.
• The medium flange withstood 1,000 N for 10,000 cycles before failing at 23,000 cycles.
• Small flanges showed varied failure points under different load conditions, but no screw loosening was observed.

Conclusions:

• The posterior flange of the novel total elbow arthroplasty design demonstrates sufficient strength to withstand expected in vivo forces.
• Cyclic loading and static strength analysis indicate that the medium-sized posterior flange offers superior strength compared to the small-sized flange.
• Ensuring secure connectivity of the ulnar body and posterior flange with the polyethylene wear component is crucial for the function of this non-mechanically linked arthroplasty.