[A biomechanical study on the stability of the injured thoraco-lumbar spine fixed with spinal instrumentation]

The purpose of this study was to evaluate the stabilizing effect of various types of spinal instrumentation now used for reconstruction of injured spine. Six types of moments were applied on fixed human thoracolumbar cadaveric spines with posterior and middle column injury. Stereophotogrammetry was used to evaluate the spinal movements three-dimensionally. Achievement of stabilization against axial rotation was most difficult in all kinds of instrumentations, though transpedicular external fixator and the Kaneda device with transverse fixators provided relatively good stability for this load mode. These two devices were also stable enough for other load modes. From the view point that sufficient stability should be obtained by short instrumentation area, these two forms of spinal instrumentation are optimal among those tested in this study. Regarding transpedicular external fixator and the Kaneda device with transverse fixators, the stability was reinforced with interbody bone grafting and application of compressive force on it.