Evaluating trunnionosis in modular anatomic shoulder arthroplasties: a retrieval study

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Failure Analysis

Background:

• Shoulder arthroplasty, including anatomic total shoulder arthroplasty (aTSA) and shoulder hemiarthroplasty (HA), is increasingly performed.
• Modular implant designs offer customization but may be susceptible to fretting and corrosion.
• Increased primary procedures have led to a rise in revision surgeries, partly due to implant wear.

Purpose of the Study:

• To evaluate the types and severity of damage in retrieved aTSA and HA components.
• To identify factors contributing to fretting and corrosion in shoulder arthroplasty implants.
• To inform future implant design for improved longevity.

Main Methods:

• Analysis of 265 retrieved aTSA and HA explants (humeral stem, head, and glenoid liner components).
• Macroscopic evaluation for standard damage modes and microscopic examination of taper junctions for fretting and corrosion.
• Correlation of damage with implant design features (e.g., taper size, metal composition) and patient data.

Main Results:

• All explanted components showed macroscopic damage.
• Fretting and corrosion were prevalent, with higher average grades on male stem components compared to female.
• Wider male tapers (>11 mm) and matched metal compositions were associated with significantly less fretting and corrosion.

Conclusions:

• Substantial fretting and corrosion damage were observed in retrieved shoulder arthroplasty components.
• Small-tapered male stems, small/thin female heads, and mismatched metal compositions are risk factors for increased implant wear.
• Optimizing modular implant design is essential for enhancing the long-term success of shoulder arthroplasty.