Ex vivo biomechanical comparison of pedicle screw and rod constructs with and without interbody fusion devices for equine cervical vertebral stabilization.

OBJECTIVE

To determine the biomechanical properties of pedicle screw and rod (PSR) constructs alone and with an interbody fusion device (PSRIFD) for equine ventral cervical vertebral stabilization.

STUDY

DESIGN

Cadaveric ex vivo biomechanical analysis.

SAMPLE POPULATION: A total of 14 (n = 14) adult equine cervical vertebral columns.

METHODS

Cervical vertebral columns were stabilized by PSR alone (n = 6) or PSRIFD (n = 5). Three columns were left unaltered as controls. Non-destructive biomechanical testing showed the kinematic range of motion (ROM), compliance, and neutral zone of each spinal unit in the three main kinematic directions (flexion-extension, lateral bending and axial rotation). Destructive testing was performed to identify mode of failure and stiffness in flexion. Non-destructive and destructive biomechanical data were compared by ANOVA between experimental groups.

RESULTS

In flexion-extension, PSR and PSRIFD had significantly lower ROM, compliance and neutral zone than controls (all p < .05). ROM, compliance and neutral zone were not different between PSR and PSRIFD groups. In axial rotation, the neutral zone of PSR was lower than PSRIFD (p = .013) and both were lower than controls (p < .0001 and p < .02, respectively). Stiffness and moment failure between PSR and PSRIFD groups were not different. All constructs failed through articular process joint dislocation, though the PSRIFD group also had ventral IFD migration.

CONCLUSION

PSR and PSRIFD groups have similar biomechanical properties and modes of failure, though PSRIFD had higher catastrophic injury potential.

CLINICAL SIGNIFICANCE: These findings support that PSR constructs provide comparable biomechanical stability to PSRIFD, reducing time and potential complications associated with IFD placement.