Computer model analysis of the Swanson and Sutter metacarpophalangeal joint implants

Area of Science:

• Biomaterials Engineering
• Orthopedic Biomechanics
• Medical Device Design

Background:

• Silastic finger metacarpophalangeal joint implants are used to restore function.
• Understanding implant behavior under physiological loading is crucial for improving patient outcomes.
• Previous studies have not fully elucidated the biomechanical differences between implant designs.

Purpose of the Study:

• To compare the biomechanical performance of the Sutter and Swanson finger joint implants using finite element analysis.
• To predict potential failure modes and identify areas of high stress concentration in both implant designs.
• To provide insights for the development of more robust and durable metacarpophalangeal joint implants.

Main Methods:

• A representative model of Silastic finger metacarpophalangeal joint implants was created using finite element software.
• The implants were subjected to simulated movements including flexion, lateral deviation, and combined motions.
• Stress fields and stem pistoning within the medullary cavities were analyzed for both implant types.

Main Results:

• Pistoning of implant stems was observed in both the Sutter and Swanson implants.
• The Sutter implant exhibited higher stress fields, particularly at the central hinge, compared to the Swanson implant for equivalent flexion.
• Lateral deviation significantly increased internal stress concentrations in both implant designs, more so than pure flexion.

Conclusions:

• The Swanson implant demonstrates lower stress magnitudes and is predicted to have a lower likelihood of failure compared to the Sutter implant.
• The Sutter implant is predicted to fail at its central hinge region.
• The Swanson implant is likely to fail at the central hinge-stem interface regions, suggesting areas for design improvement.