Computer-assisted assembly and correction simulation for complex axis deviations using the Ilizarov fixator.

In axis correction with the Ilizarov ring fixator, the correction results are often insufficient or there are unexpected translation effects, which can be causally attributed to wrong preoperative planning or inaccurate assembly. To avoid such results, computerised simulation was developed. Via digitalisation of the bone outlines traced from X-radiographs with an additional scale, preoperative correction planning can be performed, simulated with normal software. This can be used while constructing the apparatus and positioning the joints. In addition, the translation effect of the bone fragments can be simulated by arbitrarily choosing the pivot of the correction. In transferring the X-radiograph true to scale, one can compare the ring planes before and after correction. It is possible to estimate the necessary distraction as well as compression and thus the postoperative distraction mode. Using computerised planning, the apparatus construction can be optimised and complications caused by misplanning avoided. Not only the inexperienced user can benefit from this aid.