Inset glenoid component stability and bone removal by implantation depth

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Biomaterials science

Background:

• Aseptic loosening of cemented glenoid components in total shoulder arthroplasty (TSA) is a primary driver for revision surgeries.
• The rocking-horse phenomenon may accelerate loosening, prompting the development of inset glenoid implants.
• Optimal inset depth for minimizing micromotion and preserving bone is not well-established.

Purpose of the Study:

• To evaluate the impact of different inset depths on glenoid component micromotion and bone preservation.
• To determine an optimal inset depth for TSA glenoid components.
• To compare micromotion, bone removal, and bone density at various inset depths.

Main Methods:

• Finite element models of osteoarthritic scapulae were created from CT scans.
• Circular inset glenoid components were virtually implanted at 25%, 50%, 75%, and 100% depths.
• Simulated glenohumeral joint loading was applied, and micromotion, bone removal volume, and sub-component bone density were analyzed.

Main Results:

• No significant correlation was found between inset depth and tangential or normal micromotion.
• Deeper insetting (up to 100%) significantly increased bone removal compared to shallower depths (25%).
• Bone density beneath the component was highest at 25% inset depth and decreased significantly with greater depths.

Conclusions:

• Inset depth did not significantly affect glenoid component micromotion, though deeper insetting showed a trend toward reduction.
• Deeper insetting necessitates greater bone removal and results in lower bone density, potentially compromising long-term stability.
• An inset depth of approximately 25-50% is recommended to balance implant stability, bone preservation, and supporting bone density in TSA.