Retrieval analysis of an explanted Mobi-C cervical disc replacement: A case study

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Spinal Biomechanics

Background:

• Artificial disc replacement aims to restore spinal function.
• The Mobi-C cervical disc features a mobile polyethylene insert between cobalt chromium endplates.
• Previous studies present conflicting findings on Mobi-C's biomechanical restoration and migration.

Purpose of the Study:

• To analyze an explanted Mobi-C cervical disc at nano and macro scales.
• To investigate the causes of insert migration and spinal cord compression.
• To contribute to the understanding of Mobi-C artificial disc performance and potential failure mechanisms.

Main Methods:

• Ex vivo analysis of an explanted Mobi-C artificial cervical disc.
• Nano and macro scale surface roughness measurements (Sa) of endplates and insert.
• Microscopic examination for damage, impingement, and subsurface defects.

Main Results:

• The Mobi-C insert had excessively migrated, causing spinal cord compression.
• Significant changes in surface roughness were observed on the inferior plate.
• The insert exhibited severe damage, including burnishing, scratches, subsurface whitening, and internal cracking.

Conclusions:

• The explanted Mobi-C disc demonstrated insert migration and significant wear.
• Observed damage and migration raise concerns about the long-term performance and safety of the Mobi-C artificial disc.
• Further research is needed to understand and mitigate failure modes in artificial cervical disc implants.