Abstract
Introduction: Recently frameless stereotaxy has been introduced to assist with the spinal instrumentation. The mobility of individual vertebra however limits its accuracy and ease of use. The authors have developed a novel method of spinal stereotaxy using exact plastic copies of the spine manufactured using biomodelling technology.
Methods: Fifteen patients with complex spinal disorders requiring instrumentation were recruited. A 3D CT scan of their spine was performed and the data were transferred via DICOM network to a computer workstation. ANATOMICS BIOBUILD software was used to generate the code required to manufacture exact acrylate biomodels of each spine using rapid prototyping. The biomodels were used to obtain informed consent from patients and simulate surgery. Simulation was performed using a standard power drill to place trajectory pins in the appropriate pedicles. Acrylate drill guides were manufactured using the biomodels as templates. The biomodels and templates were sterilised and used intra-operatively to assist with the placement of the instrumentation.
Results: The biomodels were found to be highly accurate and of great assistance in the planning and execution of the surgery. The ability to drill optimum screw trajectories in the biomodel and then accurately replicate the trajectory was judged especially helpful. Accurate screw placement was confirmed with post-operative CT scanning. The design of the first two templates was suboptimal as the contact surface area was too great and complex. Approximately 20 minutes was spent pre-operatively preparing each biomodel and template. Operating time was reduced, as less reliance on intra-operative X-ray was necessary. Minimal invasive surgery was greatly facilitated in planning and execution. Patients stated that the biomodels improved informed consent.
Conclusion: Biomodel spinal stereotaxy is a simple and accurate technique which may have advantages over frameless stereotaxy.
The abstracts were prepared by I. B. McPhee. Correspondence should be addressed to the Spine Society of Australia Secretariat, The Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, PO Box 14, Rundle Mall, Adelaide SA 5000, Australia.
