Biomechanical analysis of a new anterior spine implant for post-corpectomy instability

Corpectomies in the lumbar and thoracic spine are sometimes necessary in the treatment of vertebral tumor, trauma, and degeneration. The resultant defect creates marked instability. Present methods to correct this problem involve spanning the defect with structural bone graft and applying either anterior or posterior instrumentation. Some investigators have designed vertebral replacements that distract and wedge into the corpectomy site. This study investigates a proposed prosthesis with a unique method of fixation: a vertebral replacement is fixed to the bodies above and below by screws that are oriented rostrally and caudally. This fixation prevents cantelever bending of the screws, migration of the implant, and possibly visceral damage by the placement of the device. This study investigates the biomechanical performance of this device in flexion, extension, and axial loading in a calf spine model. In comparison with normal spines, this device restored the biomechanical strength of the spine to at least normal levels in all planes tested. It appears that a device of this design may be useful for the reconstruction of vertebral diseases and may reduce the need for more extensive surgeries.