Design Factors Affecting the Fixation of Cervical Disc Replacements: A Biomechanical Analysis

Area of Science:

• Biomechanical engineering
• Spinal surgery
• Medical device design

Background:

• Cervical disc replacement (CDR) migration is a growing clinical concern.
• Limited biomechanical research exists on the link between CDR design and migration risk.

Purpose of the Study:

• To investigate the relationship between different cervical disc replacement designs and the risk of implant migration.
• To identify specific design features that may contribute to CDR migration.

Main Methods:

• A biomechanical study using polyurethane models of five CDR designs.
• Measurements of endplate roughness, keel/fin height, device height, ball contact arc, and coverage angle.
• Cyclic testing simulating spinal rotations and combined loading, with continuous micromotion measurement.

Main Results:

• Ball-and-socket CDR designs exhibited greater micromotions during certain movements.
• Smaller keel/fin height and coverage angle, and larger ball contact arc correlated with increased micromotion.
• Specific device features were identified as trends influencing micromotion.

Conclusions:

• This study quantifies initial fixation (micromotion) in CDR, correlating with clinical migration data.
• Identified device-specific trends may predict in vivo micromotion and migration.
• Findings can inform the selection of safer CDRs and guide future implant development.