Prior studies have suggested that biomodels enhance patient education, preoperative 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. Our objective was to quantify the surgeon's perceptions on the usefulness of biomodels compared to standard visualisation modalities for preoperative planning and intra-operative anatomical reference. Physical biomodels were manufactured for a series of 26 consecutive patients with complex spinal pathologies using a stereolithographic technique based on CT data. The biomodels were used preoperatively for surgical planning and customising implants, and intraoperatively for anatomical reference. Following surgery, a detailed biomodel utility survey was completed by the surgeons, and informal telephone interviews were conducted with patients. Using biomodels, 21 deformity and 5 tumour cases were performed. Surgeons stated that the anatomical details were better visible on the biomodel than on other imaging modalities in 65% of cases, and exclusively visible on the biomodel in 11% of cases. Preoperative use of the biomodel led to a different decision regarding the choice of osteosynthetic materials used in 52% of cases, and the implantation site of osteosynthetic material in 74% of cases. Surgeons reported that the use of biomodels reduced operating time by a mean of 8% in tumour patients and 22% in deformity procedures. This study supports biomodelling as a useful, and sometimes essential tool in the armamentarium of imaging techniques used for complex spinal surgery.

Anterior column reconstruction of the thoracolumbar spine by structural allograft has an increased potential for biological fusion when compared to synthetic reconstructive options. Estimation of cortical union and trabecular in-growth is, however, traditionally based on plain radiography, a technique lacking in sensitivity. A new assessment method of bony union using high-speed spiral CT imaging is proposed which reflects the gradually increasing biological stability of the construct. Grade I (complete fusion) implies cortical union of the allograft and central trabecular continuity. Grade II (partial fusion) implies cortical union of the structural allograft with partial trabecular incorporation. Grade III (unipolar pseudarthrosis) denotes superior or inferior cortical non-union of the central allograft with partial trabecular discontinuity centrally and Grade IV (bipolar pseudarthrosis) suggests both superior and inferior cortical non-union with a complete lack of central trabecular continuity. Twenty-five patients underwent anterior spinal reconstruction for a single level burst fracture between T4 and L5. At a minimum of two years follow up the subjects underwent high-speed spiral CT scanning through the reconstructed region of the thoracolumbar spine. The classification showed satisfactory interobserver (kappa score = 0.91) and intraobserver (kappa score = 0.95) reliability. The use of high-speed CT imaging in the assessment of structural allograft union may allow a more accurate assessment of union. The classification system presented allows a reproducible categorization of allograft incorporation with implications for treatment.

The intervertebral discs and the spinal cord do not seem to be in danger of thermal damage during vertebroplasty. The measured energy does not seem to be sufficient for the palliative effect achieved by vertebroplasty.