Biomechanical Evaluation of a C1-C2 Posterior Arch Screw Construct

Area of Science:

• Biomechanics
• Spinal Surgery
• Orthopedics

Background:

• Atlantoaxial instability can result from injuries or degeneration, necessitating surgical fixation.
• Posterior atlantoaxial fixation aims to restore stability to the C1-C2 segment.
• The Harms procedure is a common technique for posterior atlantoaxial fixation.

Purpose of the Study:

• To biomechanically compare a C1-C2 posterior arch screw (PAS) construct with the Harms procedure for posterior atlantoaxial fixation.
• To evaluate the range of motion (ROM) of the C1-C2 segment using different fixation constructs in a human cadaveric model.

Main Methods:

• An in-vitro biomechanical study using nine human cadaveric cervical specimens (C0-C3).
• Range of motion (ROM) testing was performed on four configurations: intact, destabilized, Harms construct, and C1-C2 PAS construct.
• A pure moment of 1.5 Nm was applied to measure ROM in flexion-extension, lateral bending, and axial rotation.

Main Results:

• Both the Harms and PAS constructs significantly reduced ROM compared to the destabilized state in most modes.
• The Harms construct increased ROM in flexion-extension compared to the intact condition, while the PAS construct did not.
• No significant difference in ROM was found when comparing the Harms and PAS constructs across all tested modes.

Conclusions:

• The C1-C2 PAS construct provides biomechanical stability comparable to the established Harms procedure.
• The PAS construct demonstrates potential as an effective alternative for posterior atlantoaxial fixation.
• Further research may explore the long-term clinical outcomes of the PAS construct.