Stereolithography in Maxillofacial Surgery

Stereolithography is an industrial process which uses data generated from computer-assisted design (CAD) to generate three-dimensional models. The data drives a laser over a bath of photosensitive resin which produces a series of stacked slices, which produce a accurate three-dimensional industrial prototype or model. This technique can be used by the maxillofacial surgeon to produce three-dimensional representations of facial bony structures using data from CT or MRI scans.

These so-called bio-models can be extremely useful in a number of particular clinical situations involving bony facial deformities, as this process allows the accurate visualisation of the facial skeleton. It is an invaluable aid to both the diagnosis and treatment planning of congenital, developmental and post-traumatic conditions affecting the facial region. In particular, it allows the maxillofacial surgeon to appreciate spatial displacements in all three dimensions and to make accurate measurement of the deformity.

The correction of post-traumatic or development facial asymmetry has always been difficult. Great accuracy is required to achieve a successful surgical result, due to the fact that facial deformity and asymmetry is often the result of relatively small magnitudes of bony displacement or deformity. The surgeon is then able to practice the surgery on the model, thereby allowing full appreciation of the osteotomy bone cuts required to achieve the desired results, together with any areas which may require augmentation with bone grafts. Finally, the means of fixation of the realigned bony segments can be predicted. Valuable theatre time can be saved, by allowing the pre-operative of bone plates to be used for fixation on the "post-operative" bio-model that demonstrates the planned realignment of the facial bones. This technique also ensures there is surgical accuracy in achieving the planned outcome for the patient.

Stereolithographic bio-models can also allow the measurement of volume estimation of both bony structures for possible implantation and of bony cavities for reconstructive purposes. Stereolithography has been used in maxillofacial surgery in the following situations :

• The diagnosis of and planning of corrective surgery for congenital
  facial deformities
• Late reconstruction of complex bony facial trauma
• Orbital volume estimation, for the correction of post-traumatic
  enophthalmos
• Orbital reconstruction, following ablative surgery for malignancy
• Evaluation of bone availability for the placement of osteo-integrated
  implants, both extra and intra oral
• The pre-operative adaptation of temporomandibular joint prostheses
  for the treatment of advanced, degenerative joint disease, or post-
  traumatic bony ankylosis