Biomechanics of Adjacent Segments with Number of Inter-body Bone Grafts and Spinal Intrumentations for a Multi-level Fusion Construct Using a Finite Element Model

Cervical fusion is a traditional procedure for the treatment of singleand multi-level spondylotic myleopathy or radiculopathy. The stand-alone graft has been shown to be less effective in providing the stability to construct especially with multi-level decompression. Additional stabilization of stand-alone grafting with anterior instrumentation (plate and screws), posterior instrumentation (rods and screws) or a combination of anterior and posterior instrumentation helps in achieving better fusion rates and reduces the possibility of graft dislodgement or subsidence. With the addition of spinal instrumentation and increase in the stiffness of the construct level, the adjacent levels are subjected to increased motion. In spite of previous in vivo and in vitro studies, the biomechanics of degeneration of adjacent segments after a multi-level fusion procedure is poorly understood. To date, no study exists in the literature showing the influence of number of inter-body grafts and instrumentations used for multi-level cervical decompression on the biomechanics of adjacent segments.