Hemifacial microsomia--a case report.

Hren, Natasa Ihan ; Drstvensek, Igor

1. INTRODUCTION

The human face holds many functions (eating, speaking, nonverbal communication etc) which combined with its appearance define and affect human psychosocial activities. Severe facial deformities, either congenital, traumatic or consequences of tumour removal are treated by reconstructive surgery procedures. The bone defects in maxillofacial region can be replaced by patients' own bone by different surgical principles as bone grafts or by engineering bone by distraction osteogenesis (Bell, 1992). These different autogenous bone grafts are "golden standard" for reconstruction procedures because they provide osteogenic cells, but they are of limited quantity and connected with risk of complications on donor site (Ellis III, 2003). The allogenic grafts or homografts are taken from another individual of the same species and need a lot of preparations before being used not to induce immunologic response; similar is with bone from unhuman species. So the need for bone substitutes--xenogenic grafts was the generator of great progress in developing inorganic bone substitutes, as biotechnology of bone cells cultivating. All these materials have advantages and disadvantages, but there is no ideal material yet. A good synthetic material needs to have following properties: biocompatibility, inertness, bone-similar weight or even lighter, capability to generate no artefacts on CT and MRI scans, ease of manufacturing, enough strength to resist functional stress, not being expensive and low or no thermal conductivity.

2. OBJECTIVES

The article presents the treatment of a severe facial deformity, where surgical procedures with autogenous bone graft, distraction osteogenesis, prefabricated and custom made xenogenic bone grafts were performed. Twenty four year old mentally healthy man was born with hemifacial microsomia. This is a severe asymmetry of facial bone and soft tissues in vertical, sagital and transverse plane combined with hearing impairment on the affected side (Proffit, 2003). He wasn't treated before his adulthood; all surgical procedures were done in Clinical department of maxillofacial and oral surgery, University clinical centre Ljubljana. He was treated by classical ortognathic surgical procedures (Le Fort I osteotomy and autogenous bone grafting) and by a modern surgical technology as distraction osteogenesis of mandible. After these bone surgical procedures the remaining defect of bone and soft tissues was partially compensated with on-lay xenogenic graft, later replaced with custom made titanium angular implant. His images before and after surgical procedures are presented on fig.1.

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3. METHOD

The treatment of an adult patient with hemifacial microsomia has the goal to achieve bone symmetry as good as possible, more difficult is to compensate the soft tissue deficiency. In presented patient the first surgery procedure was producing vertical part of his left lower jaw by distraction osteogenesis (fig.2).

Than his upper jaw was elongated and rotated by LeFort I osteotomy and his autogenous bone grafting (fig. 3). Because of the transverse discrepancy the on-lay xenogenic graft (Medpore mandible on-lay graft) was performed, but it was removed after more than one year because of the inflammation. Than we decided for custom made titanium angular implant (fig. 4), which was prepared on the basis of computer tomography (CT) scans, Computer Aided Design (CAD) and Rapid Manufacturing technologies (Laboratory for Intelligent Manufacturing Systems, of the University of Maribor, Faculty of Mechanical Engineering).

[FIGURE 2 OMITTED]

4. IMPLANT PRODUCTION

The production of bone implants starts by capturing a three-dimensional data set of the problematic area (scull, face, mandibular area ...). Usual and the most common way is transformation of sets of CT or MRI two-dimensional pictures into a three-dimensional, digital model. The model is then used as a base on which the modeling of defective--missing area takes place. If the defect is positioned in an area that has its "mirror image" on another side of the body than the form of the implant can relatively easily be produced by means of Boolean operators. In a case of "mirror less" features some more sophisticated methods and dedicated software have to be used to finish the implant. Presented case study deals with mirroring and some special finishing methods performed by dedicated animation software. Mirrored model of the jaw was used as a reference for modeling of the implant using standard CAD approaches. In a case of a jaw and other bones with attached muscle tissues simple Boolean subtraction can not be used to model a final shape of the implant. Positions of muscle attachments need to be taken in consideration, therefore the mirrored model is only used as guidance for shaping cross section polylines. The polylines are later used to guide a modeling of implant surfaces that shape the final form of the implant.

[FIGURE 3 OMITTED]

Finished digital model is then manufactured by one of the Rapid Manufacturing (RM) technologies. RM products are usually made of titanium or cobalt--chrome alloys since these are at the moment the only biocompatible materials available for RM technologies that can be directly used as implants. Research is going on in the field of so called Bio-plotters that are able to manufacture parts from bio-compatible and even biodegradable materials but there has not been a commercial brake-through yet what makes these technologies useless for surgical praxis.

[FIGURE 4 OMITTED]

5. DISSCUSION

The presented case report is an example of different surgical procedures used to correct a facial deformity with different surgical procedures. With standard orthognatic procedures (osteotomies of the bone, their correction in the position and volume) we can achieve better facial function and harmony, but not perfect (Cheng, 1998). The distraction osteogenesis is very innovative approach for forming patient's own bone (Samchucov, 2000) but at least in one dimension the quantity is not ideal (Bell & Guerrero, 2007). So there is still the need for xenografts as bone substitutes--in the majority of the facial deformity cases for esthetic correction of bone or soft tissue defects.

6. CONCLUSIONS

The medical needs and contemporary technological development are the fields that will be in close relation in the future in many fields of the medicine. For facial deformities, in spite of different surgical approaches, there is still a need for development of materials for xenogenic bone grafts and the technologic facilities can nowadays prepare custom made bone implants to achieve better esthetical results.

7. REFERENCES

8.

Bell, WH. (1992). Modern practice in orthognatic and reconstructive surgery. W. B. Saunders company, Philadelphia.

Bell, WH. & Guerrero, CA. (2007). Distraction osteogenesis of the facial skeleton. BC Decker Inc, Hamilton

Cheng, LHH.; Roles, D. & Telfer, MR. (1998). Orthognatic surgery: the patients' perspective. Brit J Oral Maxillofac Surg 36., 261-263,

Ellis III, E. (2003). Surgical reconstruction of defects of the jaw. In: Peterson,; Ellis,; Hupp, & Tucker. Maxillofacial surgery, 4rd edition. Mosby, New York, 646-659,

Proffit, WR. & Turvey, TA. Dentofacial asymetry. In: Proffit, WR.; White, RP. & Sarver, DM. (2003). Contemporary Treatment of Dentofacial Deformity. Mosby, St. Louis, 574-621,

Samchucov, ML.; Cope, JB. & Cherkashin, AM. (2000). Craniofacial distraction osteogenesis. Mosby, St Louis.