Clinical application of computer-designed polystyrene models in complex severe spinal deformities: a pilot study

Surgical treatment of complex severe spinal deformity, involving a scoliosis Cobb angle of more than 90° and kyphosis or vertebral and rib deformity, is challenging. Preoperative two-dimensional images resulting from plain film radiography, computed tomography (CT) and magnetic resonance imaging provide limited morphometric information. Although the three-dimensional (3D) reconstruction CT with special software can view the stereo and rotate the spinal image on the screen, it cannot show the full-scale spine and cannot directly be used on the operation table. This study was conducted to investigate the application of computer-designed polystyrene models in the treatment of complex severe spinal deformity. The study involved 16 cases of complex severe spinal deformity treated in our hospital between 1 May 2004 and 31 December 2007; the mean ± SD preoperative scoliosis Cobb angle was 118° ± 27°. The CT scanning digital imaging and communication in medicine (DICOM) data sets of the affected spinal segments were collected for 3D digital reconstruction and rapid prototyping to prepare computer-designed polystyrene models, which were applied in the treatment of these cases. The computer-designed polystyrene models allowed 3D observation and measurement of the deformities directly, which helped the surgeon to perform morphological assessment and communicate with the patient and colleagues. Furthermore, the models also guided the choice and placement of pedicle screws. Moreover, the models were used to aid in virtual surgery and guide the actual surgical procedure. The mean ± SD postoperative scoliosis Cobb angle was 42° ± 32°, and no serious complications such as spinal cord or major vascular injury occurred. The use of computer-designed polystyrene models could provide more accurate morphometric information and facilitate surgical correction of complex severe spinal deformity.