Rapid prototyping in craniofacial surgery: Using a positioning guide after zygomatic osteotomy – A case report

Abstract

Introduction

The management of post-traumatic deformity in the midface region poses challenges for the maxillofacial surgeon. Ensuring symmetry after zygomatic osteotomy can be difficult and precise positioning of the osteotomised bony fragments requires careful treatment planning. It may be necessary to use a coronal flap to allow the surgeon to compare the contralateral zygomatic bone to allow symmetrical reduction.

The authors present a new technique for the positioning of osteotomised zygomatic bones using a combination of computer assisted surgical simulation and rapid prototyping.

Method

A patient presented to our unit with a post-traumatic zygomatic deformity. Using surgical simulation software the displaced zygomatic bone was osteotomised and placed in the idéal position on a three-dimensional computed tomography scan (3D CT). The position was determined by reference to the contralateral zygoma. In addition the repositioning of the soft tissues was simulated.

A surgical guide which allowed intraoperative positioning of the osteotomised zygoma was manufactured by a rapid prototyping process. Use of the guide allowed a minimally invasive approach to the affected zygoma. The post-operative results were compared to the predicted outcome.

Results

The post-operative appearance was satisfactory and corresponded well with the predicted result. There was a significant reduction in operative time compared to the previous management of similar cases.

Introduction

In craniofacial surgery involving the treatment of facial asymmetry, accurate positioning of the osteotomised bone fragments can be a technical challenge.

In maxillo/mandibular orthognathic surgery dental splints provide accurate spatial positioning of the osteotomised maxilla and mandible. This is not possible in the mid and upper face and the surgeon often uses visual comparison between the osteotomised and normal side for positioning.

The ability to transform CT data into three-dimensional models using stereolithography models (Kernan and Wimsatt, 2000, Murray et al., 2008) and more recently the use of simulation software (Murray et al., 2008, Marmulla and Niederdellmann, 1999), have enabled surgeons to plan osteotomies and distraction osteogenesis in three dimensions and to adapt osteosynthesis plates prior to surgery. Using different scanning techniques allowed to predict soft tissue changes (Pektas et al., 2007; Donatsky et al., 2009). Using these relatively new scanning techniques to plan surgery it is now possible to design flaps and place implants in a predetermined position (Rohner et al., 2000, Rohner et al., 2002). It is now also possible to create a virtual model from a CT scan, and using rapid prototyping, go directly to manufacturing an implant or plate without the need for a physical model (Wagner et al., 2004, Petzold et al., 1999, Eufinger and Wehmoller, 1998). This technique can also be used to manufacture a template for outlining osteotomy cuts or resection margins (Leiggener et al., 2009).

An alternative approach to the problem of accurate positioning of osteotomised bony segments has been the application of intraoperative navigation techniques. These were originally developed in neurosurgery (Watzinger et al., 1997, Marmulla and Niederdellmann, 1998, Klug et al., 2006, Lauer et al., 2006).

This paper describes a simple and reliable technique for positioning the osteotomised zygomatic bone in the treatment of post-traumatic deformity using computer assisted surgical simulation and a positioning template manufactured using rapid prototyping (RP) technology.