Orbital floor and cranioplasty repair with press-formed titanium implants; a means to assess the technical reproducibility of computer planning, fabrication and surgery

Introduction

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.