[Reconstruction of open width of the spinal canal by internal fixator instrumentation and remodeling]

In 106 cases of unstable vertebral fractures treated with the ASIF internal fixator, the degree of restoration of the spinal canal could be studied in detail. Computer-aided planimetry was used to measure the area of the spinal canal. Three series could be studied, where the postoperative CT scans had been performed at different times. The first series of 58 cases had the CT scans taken immediately after surgery; the initial mean traumatic narrowing of the spinal canal had been 42.8%, but after surgery it was only 25.2%. The second series consisted of 74 CT scans performed after implant removal. At this time, a residual defect of only 3.7% was observed. In a third series 31 cases could be analysed where CT scans obtained both directly after surgery and after implant removal were available. This confirmed the first two series insofar as it demonstrated the existence of a further mechanism, i.e. remodeling, that served to increase the degree of restoration of the spinal canal. This biological-functional process operates to approximately the same degree at each fracture level, demonstrated by the almost parallel course of the graph showing reduction plus internal fixation and remodeling. In summary, the remaining deficit of 25% after surgery is restored almost to normal through remodeling and can be neglected, provided there is no neurologic damage.