Biomechanical comparison of C1-C2 posterior arthrodesis techniques

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Spinal Fusion Techniques

Background:

• Posterior atlantoaxial arthrodesis commonly uses Gallie or Brooks techniques combined with transarticular screws.
• Anatomical limitations can prevent unilateral or bilateral transarticular screw insertion.
• Assessing alternative fixation strategies is crucial for effective atlantoaxial stabilization.

Purpose of the Study:

• To biomechanically compare five posterior atlantoaxial arthrodesis techniques.
• To evaluate the efficacy of posterior wire constructs with one or two transarticular screws.

Main Methods:

• Biomechanical testing of ten human cadaveric upper cervical spine specimens.
• Specimens were tested intact, after injury (odontoidectomy, ligament section), and after stabilization with five techniques: Brooks-Jenkins cable fixation alone, with one screw, or with two screws; Gallie posterior wire construct with one screw or with two screws.
• Applied pure moments in flexion-extension, lateral bending, and axial torsion within physiologic limits.

Main Results:

• All five stabilization techniques significantly reduced range of motion (ROM) and neutral zone (NZ) compared to the injured state (P < 0.01).
• In flexion-extension, the Gallie construct with one screw showed significantly higher ROM than Brooks-Jenkins with one or two screws (P < 0.05).
• In axial torsion, the Gallie construct with one screw had a larger NZ and ROM than the other four constructs (P < 0.05).

Conclusions:

• Neither Gallie nor Brooks-Jenkins cable fixation alone is sufficient for atlantoaxial arthrodesis.
• When two transarticular screws are feasible, Gallie and Brooks techniques provide comparable stability.
• In cases requiring only a single screw, the Brooks-Jenkins technique is recommended over the Gallie technique for superior stability.