Anterior cervical graft and plate load sharing.

Anterior discectomy and fusion with an interbody bone graft and anterior plate is a common procedure in cervical spine surgical management. However, the graft may be shielded from some mechanical loading by the plate. Mechanical testing was performed on six cadaveric calf spines that were subjected to a simulated anterior cervical discectomy and fusion with an interbody bone graft alone and with an anterior plate to determine the amount of load sharing between the graft and plate. The load-displacement data were used to compute the amount of load sharing between the graft and the plate as a continuous function of the applied axial compression load. Although the percent load transmitted through the graft decreased (53 to 41%) as the axial load increased (45 to 90 N), the magnitude of load transmitted through the graft increased (24 to 37 N), with corresponding intervertebral strains <6%. In a single-level procedure, an anterior cervical plate serves as a load-sharing device rather than a load-shielding device, enabling graft consolidation as observed in clinical studies.