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The use of physical biomodeling in complex spine surgery

THE USE OF PHYSICAL BIOMODELING IN COMPLEX SPINE SURGERY 
 
Maree T Izatt, Paul LPJ Thorpe, Paul S D’Urso, Otto von Arx, Robert G Thompson, Clayton J Adam, John WS Earwaker, Robert D Labrom, Geoffrey N Askin. 
 
Paediatric Spine Research Group, Brisbane, Australia. 
 
INTRODUCTION Prior studies have suggested that biomodels enhance patient education, pre-operative planning and intra-operative stereotaxy, however the usefulness of biomodels compared to regular imaging modalities such as x-ray, CT and MR has not been quantified. (1) The aim of this study was to quantify surgeons' perceptions on the usefulness of biomodels compared to standard visualisation modalities for pre-operative planning and intra-operative anatomical reference. 
 
METHOD Physical biomodels were manufactured for a consecutive series of 26 patients with complex spinal pathologies using a stereolithographic technique based on CT data1. Patients were selected for the technique by the surgeons, if the pathoanatomy was not considered to be clearly displayed by standard imaging techniques . The biomodels were used pre-operatively for assessment of spinal pathology, parent and patient education, obtaining informed consent, surgical planning and customising implants. Intra-operatively, the sterilized biomodel was useful for anatomical reference, surgical navigation and as a teaching aid. Following surgery, a detailed biomodel utility survey was completed by the surgeons (GNA and RDL) for all cases where a biomodel was ordered. 
 
RESULTS Twenty one deformity and five tumour cases were performed using biomodels. Surgeons stated that the anatomical detail was better visible on the biomodel than on other imaging modalities in 17 (65%) cases, and exclusively visible on the biomodel in 3 (11%) cases. Preoperative use of the biomodel led to a different decision regarding the choice of osteosynthetic materials used in 14 (52%) cases, and the implantation site of osteosynthetic material in 20 (74%) cases. Biomodels were found to be highly accurate in relation to anatomy identified during the surgery when compared with other visualization modalities and resulted in improved communication with patients/parents and informed consent in 25 (96%) cases. Surgeons reported that the use of biomodels reduced operating times in 23 (89%) cases by a mean of 63 minutes per case (range 0-180mins) which included 8% (range 0-125mins) in tumour patients and 22% (range 30-180mins) in deformity procedures, and therefore surgical costs were often subsequently reduced despite the additional cost of the biomodel. In all cases, the surgeons reported the model had a positive effect on the outcome of the surgical procedure and that they would order a biomodel again should a similar case present. 
 
DISCUSSION This study supports physical biomodeling as a useful, and sometimes essential tool in the armamentarium of imaging techniques used for complex spinal surgery. 
 
REFERENCES 1.D’Urso PS, Askin GN, Earwaker WJS, Merry GS, Thompson RG, Barker TM, Effeney DJ. Spinal Biomodeling, SPINE 24(12): 1247-51, 1999.