Biomechanical Comparison of the Load Sharing Properties of Unidirectional and Bidirectional Multilevel Anterior Cervical Plates

Anterior cervical discectomy and graft fusion with spinal instrumentation is an accepted surgical method for the treatment of cervical spondylosis or other spinal disc diseases. Our previous biomechanical experiences with multi-level strut-graft mechanics have shown that constrained anterior instrumentation reverses the loading mechanics of a multi-level cervical strut-graft tested under physiologic flexion and extension conditions, which may promote graft pistoning [1]. The design of a constrained or static anterior cervical plate (ACP) may contribute to this phenomenon. Concurrently graft subsidence has also been noted with anterior cervical plate fusion surgery [2]. As the graft subsides, a gap can occur at the interface between the graft and vertebral end plates which can lead to pseudoarthrosis.