A plate-rod device for treatment of cervicothoracic disorders: Comparison of mechanical testing with established cervical spine in vitro load testingdata

Posterior cervical internal fixation has long been accomplished using wires , hooks, and rods. More recently, the cervical lateral mass screw and plate or rod systems have been used effectively in unstable lower cervical spine disorders. Each form of fixation has its advantages and disadvantages. Int erspinous wiring and lateral mass screw placement obviate canal penetration in the cervical region but are associated with a potential neurologic risk as a result of canal encroachment. Minor canal intrusion by laminar hooks in the thoracic spine pose a lesser neurologic risk than in the cervical re gion. To exploit the benefits and safety features of spinal instrumentation , a combination plate rod construct (PRC) has been developed that obviates canal penetration in the cervical region by way of lateral mass and cervica l pedicle screw fixation and hooks or wires in the thoracic spine. A biomec hanical analysis of the PRC device was performed and compared with the in v ivo maximal load data of the cervical spine and established maximal load da ta of the Roy-Camille posterior cervical fixation system. The PRC has great er strength and resistance to failure than is necessary to sustain maximal in vivo cervical spine loads, and it has also compared favorably with the p arameters of the Roy-Camille system. The PRC device, or variations on it, i s an excellent option for spinal fixation across the cervicothoracic juncti on because of its superior biomechanical qualities and versatility in stabi lizing a complex anatomic junction of the spine.