Stress shielding following stemless anatomic total shoulder arthroplasty

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Finite element analysis suggests stemless implants may reduce stress shielding.
• Proximal humeral bone adaptations after stemless anatomic total shoulder arthroplasty require assessment.

Purpose of the Study:

• To evaluate radiographic bone adaptations, specifically stress shielding, following stemless anatomic total shoulder arthroplasty.

Main Methods:

• Retrospective review of 152 prospectively followed stemless total shoulder arthroplasties.
• Radiographic assessment of stress shielding (mild, moderate, severe) at standard intervals.
• Analysis of clinical outcomes and influence of subscapularis management on stress shielding.

Main Results:

• Stress shielding observed in 41% of shoulders at 2 years postoperatively; severe shielding in 7%.
• No significant difference in clinical/functional outcomes between shoulders with and without stress shielding.
• Lesser tuberosity osteotomy was associated with significantly lower rates of stress shielding (p=0.021).

Conclusions:

• Stress shielding occurs more frequently than expected after stemless total shoulder arthroplasty.
• Observed stress shielding did not lead to implant loosening or migration at 2-year follow-up.
• Subscapularis management, specifically lesser tuberosity osteotomy, may mitigate stress shielding.