Institutions

1 Department of Craniofacial Surgery, Chelsea & Westminster Hospital

2 Cavendish Implants, London

3 Cavendish Imaging, London

4 Dawood&Tanner Dental Practice

Aim of investigation

To develop a novel method of using custom surgical templates to provide intra-operative guides for facial bone contouring to treat massive fibrous dysplasia.

Material & Methods

CT data was manipulated in 3D to determine the best possible final contour within the significantly expanded temporal, orbital, zygomatic, maxillary and mandibular components of the disease (Figure 1). These plans were based on normal anatomy from the contralateral side. Custom-made surgical templates were made using rapid-prototyping to allow the operating surgeon to drill to pre-determined depths within the abnormal bone using 3.8mm zygomatic implant drill bits (Figure 2). These multiple drill holes then acted as multiple “depth gauges” for bony re-contouring using conventional methods.

Results and Conclusions

This technique allows the operating surgeon to quickly and accurately contour bone, of particular benefit when normal anatomy is significantly altered by pathology. This facilitated delivery of optimal postoperative symmetrisation and reduced both surgical time and morbidity. From our careful search of the literature we believe that this is the first time such a technique has been used in the facial skeleton.

We present a novel method of designing and using surgical drill guides of variable thickness to permit accurate drilling to pre-determined depths using a single drill bit. This allows the operating surgeon to quickly and accurately contour bone, of particular benefit when normal anatomy is significantly altered by pathology. From our careful search of the literature we believe that this is the first time that such a technique has been used in the facial skeleton.

We will illustrate the usefulness of this technique with a case of hemifacial recontouring performed for massive, stable polyostic fibrous dysplasia. We will demonstrate how the 3D computer modelling and drill guides manufactured by rapid prototyping significantly facilitated the recontouring procedure. This reduced both surgical time and morbidity, and allowed delivery of the optimal post-operative symmetrisation.

To evaluate the use of computer-assisted designed and manufactured (CAD/CAM) orbital wall and floor implants for late reconstruction of extensive orbital fractures.

Methods

We performed a retrospective data review on 29 patients treated for extensive orbital fractures from January 1, 1997, through December 31, 2007, at the University College London Hospitals. The use of a CAD/CAM technique based on cross-sectional computed tomographic scans, generating an accurate stereolithographic model, enabled surgeons and technicians to plan and create the best dimension and position of the implant. Sheet titanium was then pressed to shape from a design outlined on a counterdie of the new reconstructed model.

Results

Twenty-nine patients with late enophthalmos due to complex orbital fractures underwent successful reconstruction surgery. Enophthalmos was corrected in all patients. Diplopia was improved in 14 patients, and extraocular movement was improved in 13.

Conclusions

The CAD/CAM implants represent a financially viable method for secondary reconstruction of the orbit. This method enables the surgeon to plan the operation in detail, facilitates the surgical procedure, and can help to improve the outcome.

The successful production of accurate titanium implants for the reconstruction of craniofacial and maxillofacial bony defects from Computer Tomography (CT) scan data and computer assisted design and manufacturing methods is now commonplace, but little data exists to demonstrate the technical precision of this approach to orbital repair.

This paper demonstrates how the planned and achieved result may be compared and evaluated at the time of manufacture and subsequently, postoperatively.

Method

The orbital defect was assessed on an interactive display showing simultaneously the patients sagittal, coronal and transverse CT cross-sections and 3D reconstruction. A mirror-image of the undamaged orbit was created to 'virtually' repair the defect.

A rapid prototype stereo lithographic model of the repaired defect was fabricated and used to cold-press a titanium form, which was further refined to create the finished implant. A notch in the implant vertically above the infraorbital nerve was added to help the surgeon to position the implant. The implants were developed in conformance with Medical Devices regulations for customised implants.

Before a distribution of the finished implant the stereo lithographic modal was scanned in a Cone Beam Computer Tomography Scanner with the implant in place. A similar postoperative scan of the patient was also taken of the repaired defect with implant in place.

Result

Co-registration of these scans enabled an assessment of the accuracy of the implant manufacturing process, and the correlation between planned and achieved surgical result.

Conclusion

This work shows the design and the anatomical landmarks well-suited for accurate positioning of the implant in theatre.