Comparison of the predicted surgical results following virtual planning with those actually achieved following bimaxillary operation of dysgnathia.

Aim: To simulate the surgery of dysgnathia, several forms of computer software allowing two-dimensional 'virtual' planning are frequently used. However, in many cases it is not possible to transfer the virtual plan accurately to the surgical site. It is the purpose of this study to find the errors likely to occur when transferring the data.
Methods: In 22 bimaxillary osteotomies for dysgnathia, the results of preoperative planning were compared with the surgical outcomes. The programme WinCeph 4.19 (Compudent) was used for cephalometric analyses and simulation of the operations.
Results: Six major skeletal parameters were evaluated when comparing both the planned and the actual outcome, and the following results were recorded: Delta-SNA 1.53 degrees (+/-1.20), Delta-SNB 1.67 degrees (+/-1.29), Delta-ANB 1.62 degrees (+/-1.47), Delta-NL-NSL 3.9 degrees (+/-2.30), Delta-ML-NSL 3.6 degrees (+/-3.7) and Delta-ArGoMe 6.1 degrees (+/-4.6).
Conclusion: It was anticipated that the most important differences between planned and surgical outcomes were found to be in the vertical changes. Planning and data transfer was comparatively accurate with regard to sagittal data. Apart from several mechanical methods for data transfer, systems using navigation are therefore being discussed and used increasingly. They ensure accurate data transfer to the surgical site.