A patient-matched prosthesis for thumb amputations: Design, mechanical and functional evaluation

Area of Science:

• Biomedical Engineering
• Reconstructive Surgery
• Prosthetics

Background:

• Thumb amputations significantly impair hand functionality, with existing treatments like microsurgery and vacuum prostheses having limitations.
• Osseointegration offers a promising alternative, but patient-matched devices for thumb amputations are scarce due to variations in residual bone anatomy.
• Current prosthetic solutions lack customization, failing to address the diverse characteristics of remaining bone in amputated limbs.

Purpose of the Study:

• To present the first patient-matched osseointegrated medical device specifically designed for thumb amputations.
• To optimize the design of the osseointegrated fixture, abutment, and external prosthesis through computational and experimental analysis.
• To evaluate the mechanical performance of the novel device for restoring thumb functionality in daily activities.

Main Methods:

• Development of a three-component system: an implanted osseointegrated fixture, an abutment, and an external digital prosthesis.
• Design optimization using computational and experimental analyses focusing on preserving the implant fixture and bone integrity.
• Mechanical testing, including pinch force analysis, comparing device performance against healthy subject data (approx. 80 N maximum pinch force).

Main Results:

• The novel patient-matched osseointegrated device successfully achieves mechanical performance required for daily activities.
• Computational and experimental analyses confirmed the device's ability to meet functional demands.
• Failure analysis indicated that under loads exceeding daily use, failure is likely to occur in the external abutment component, not the internal fixture or bone.

Conclusions:

• The developed patient-matched osseointegrated prosthesis represents a significant advancement in treating thumb amputations.
• The device shows potential for restoring crucial hand functionality, with a safety mechanism where excessive force leads to external component failure.
• Further clinical studies are necessary to validate the device's long-term efficacy and gather patient/surgeon feedback, particularly regarding the bone-implant interface dynamics.