Application of three-level navigation template in surgery for hemivertebrae in adolescents

Abstract

Objective. To assess efficacy and safety of using a three-level navigation template in the surgical treatment of congenital spinal deformities. Material and Methods. Three-level navigation templates were used in surgical treatment of four consecutively operated 10–17-year-old patients with congenital scoliosis associated with thoracic hemivertebrae. The correctness of screw position was evaluated according to CT data using a 2-mm increment method: class 0 – intraosseous screw position; class 1 – the screw extends beyond the pedicle cortex by less than 2 mm; class 2 – by 2–4 mm; and class 3 – by more than 4 mm. Preoperative DICOM data were processed with free software. The model of target zone and navigation template were 3D printed and used in surgery. Results. Four of 16 (25 %) pedicles were narrower than 4.35 mm and were estimated as difficult for implantation with a planned viola- tion of the integrity of the endplate. Perforation of the outer cortical layer took place in all these cases, and screw position corresponded to class 2 only in pedicle width of 1.9 mm. In pedicles wider than 4.35 mm, 11 of 12 (91.7 %) screws were implanted intraosseously. One screw extended beyond the pedicle cortex by 0.8 mm (class 1). Conclusion. Three-level navigation template can be considered as an effective means of positioning transpedicular screws in secondarily changed segments adjacent to anomalous one and confounding implantation. Free software is sufficient for preparing 3D-model of target zone and navigation template, and such a model is a highly informative reference object that is convenient to use during the operation. A navigation template made using 3D printing does not require the use of expensive equipment, which can make surgery for congenital scoliosis more accessible.

Keywords

• 3d printing
• navigation template
• congenital scoliosis