O.352 Trefoil mapping system – a basis to classify orbital defects

Oral Presentations defect 3 days after surgery. The MRI showed a flattening at the eye bulb in opposite of the expander. We suspected distortion caused by too much volume and pressure of the implant. The expander surface was shaped slightly concave to fit the eye bulb exactly in a revision operation. After the revision the eyesight was normal again and we observed no further problems. Conclusions: The HOE was extremely biocompatible and showed no desorption even in the revised case. It is recommended to control the patients postoperatively within the first week daily by clinical observation and at least one time by MRI. This would be necessary for early determination of badly fitting implants affecting the eye bulb. Nevertheless the HOE proved to be a favourable and stable material for treatment of orbital volume deficiency. O.352 Trefoil mapping system – a basis to classify orbital defects C. Jaquiery, C.P. Cornelius, C. Buitrago-Tellez, C. Kunz, B. Hammer. Abteilung f¨ur Kiefer-und Gesichtschirurgie, Universit¨atsspital, Basel, Switzerland The internal bony orbit can be graphically displayed in a trefoil manner in order to precisely document orbital wall fractures and defects in adults. The 3-dimensional bony cavity is unfolded like peeling a banana and each of the orbital walls is depicted approximately in 1:1 scale allowing for geometric mapping of the fracture or defect topography in correlation to CT imaging in axial and coronal planes. Using a preliminary 5 type fracture classification derived from clinical experience, the CT scans of a series of 35 patients with varying orbital fractures were reviewed and compared with the trefoil system. As a result the effectiveness and suitability of the trefoil system could be confirmed. Beyond the rapidly intelligible information on anatomic fracture location and defect size, the extent and the technical difficulties of surgical reconstruction may be anticipated, since the size and shape of bone grafts or alloplastic implants such as titanium meshes can be accurately outlined preoperatively. Consequently, surgical reconstruction is facilitated. The trefoil design is intended to allow for the integration into the AO/ASIF analogue tripartion concept of craniofacial/midfacial fractures. The development of a software program that reformats CT scans according to the graphic trefoil mapping system is a current project of our working group. O.353 Use silicon and negative pressure in contracted orbital socket M. Goisis, V. Bonanno, R. Monteverdi, P. Formillo, A.B. Giann`ı. IRCCS Galeazzi, Milano, Italy Objectives: Based on the pathology of the anophthalmic socket contraction, two different classes of patients can be recognized: Class I: Those who only have eye socket contraction with normal orbital volume. Clas II: Patients who have inadequate socket lining, as well as orbital volume deficit. A simple technique to treat these classes of patient is described. Methods: A 3 1/2 year study of 11 patient with socket contraction was conducted. 6 patients were class I, 5 were class II. The causative pathologies included 4 retinoblastomas, 2 congenital abnormalities and 4 childhood traumas. The surgical treatment was a skin or mucosa graft for class I, a dermofat graft for class II. A simple technique based on a silicon stent and a negative pressure between the graft and the recipient bed was used in all of patients. Results: The average duration of follow up was 18 months (range 4−42 months). All patients are able to wear a prosthetic eye with comfort and a good cosmetic appearance. Conclusion: The choice of treatment of socket contraction should be established according to the degree of orbital volume deficit

Orthognathic surgery I

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and the amount of residual conjunctiva. In the case of severe volume deficit, the use of dermofat graft can expand the socket and can augment orbital volume.

Tuesday, 9 September 2008, 08.30–10.30

Sala Italia

Orthognathic surgery I O.354 3D analysis of skeletal changes after a BSSO M.T.P. Naphausen1 , J.-M. Plooij2 , T.J.J. Maal2 , W.A. Borstlap2 , F.A.C. Schutyser2 , G.R.J. Swennen3 , S.-J. Berg´e2 , F. NijmegenBruges1 . 3D Facial Imaging Research Group Nijmegen–Bruges. 1 Radboud University Nijmegen Medical Center, Nijmegen, Netherlands; 2 Dept OMF Surgey, RUNMC, The Netherlands; 3 Div OMF Surgery, St. Jan, Belgium Objective: Three-dimensional (3D) reconstruction of conebeam CT (CBCT) data, makes it possible to superimpose pre- and postoperative 3-D datasets, so enabling accurate 3D cephalometric comparison of the hard tissue changes in sagittal split osteotomies. The aim of this study were to assess the hard tissue positional changes in bilateral sagittal split osteotomies and to study the lingual side of the ramus. Methods: In a prospective study 20 consecutive patients with a mandibular hypoplasia were treated with a sagittal split osteotomy (Hunsuck modification). After superimpositioning of the pre and postoperative 3-D datasets changes of the position of the proximal and distal segments of the mandible were observed and compared using specifically developed landmarks for 3D linear, angular and proportional measurements. Results: Besides the expected anterior movement of the distal segments of the mandible, unexpected rotational and translational movements of the proximal segments of the mandible were visualized, resulting in obviously changed positions of the condyles in the fossae. Furthermore, wide variations of the direction of the fracture at the lingual side of the ramus were observed. Conclusion: Three-dimensional imaging and superimpositioning of pre- and postoperative 3-D datasets are useful tools to analyse surgical outcome of sagittal split osteotomies and have the potential to provide substantial additional data on the position of the proximal segments. O.355 3D analysis of soft tissue changes caused by a BSSO J.-M. Plooij1 , T.J.J. Maal1 , W.-A. Borstlap1 , S.J. Berg´e1 . 3D Facial Imaging Research Group Nijmegen–Bruges. 1 Dept OMF Surgery, Radboud University Nijmegen Medical Centre Nijmegen, The Netherlands Objective: Due to the lack of accurate 3D information of hard and soft tissue changes induced by orthognathic surgery, accurate surgical treatment planning and prediction of surgical outcome is currently not available. With three-dimensional (3D) image fusion of stereophotogrammetrical images and conebeam CT (CBCT) data, pre- and postoperative data sets can be easily superimposed now. This enables accurate comparison of the soft tissue changes caused by skeletal changes in sagittal split osteotomies. The aim of this study was to analyse the rational soft tissue changes in bilateral sagittal split osteotomies. Methods: In a prospective study 20 consecutive patients with a mandibular hypoplasia were treated with a bilateral sagittal split osteotomy (Hunsuck modification). The preoperative and 1 year postoperative data sets were matched to observe and compare the facial proportions using 3D hard- and soft tissue cephalometric analysis. Results: The linear, angular and proportional changes of the facial soft tissue caused by orthognathic surgery were clearly