Background context: Anterior cervical locking plates are currently used to provide secure fixation, which appears to help promote fusion, although the details of the in vivo biomechanical effects of plating on the spine are unknown.
Purpose: To determine if any motion was present initially in the plated anterior cervical discectomy and fusion (ACDF) and, if so, where the motion occurred.
Study design: A cohort of patients that were part of a prospective study on postoperative changes after cervical fusion were evaluated for motion at the fusion site about 2 weeks after ACDF.
Methods: Forty-eight segments in 27 patients undergoing ACDF with a cervical plate were evaluated. The patients underwent flexion and extension radiography approximately 2 weeks after surgery. Intervertebral motion at the fusion site was evaluated with validated quantitative motion analysis.
Results: Motion was perceived at 29 levels in 18 patients. The sources of motion were either actual bending of the plate itself, motion at the screw-bone interface, or screw-plate interface.
Conclusions: In many patients, anterior cervical plating after ACDF does not eliminate motion at the fusion site. Depending on the quality of bone, type of bone graft, and nature of the injury, this information may influence decisions regarding implants and postoperative bracing.