Which is the ideal point of time to perform intraoperative 3D imaging in dorsal stabilisation of thoracolumbar spine fractures? A matched pair analysis

Abstract

Introduction: After dorsal stabilisation of vertebral fractures by an internal fixateur the postoperative computed tomography is a standard procedure to control the positions of the pedicle screws, the success of the reposition, the clearance of the spinal canal and to plane an additive secondary ventral stabilisation. An intraoperative scan with a 3D image intensifier may clarify these questions directly after the implantation with the possibility of an immediate correction of the implants. The aim of this study was to find out the optimal point of time to perform an intraoperative 3D scan and if a postoperative computed tomography is dispensable.

Patients and methods: Intraoperative 3D scans were carried out on 33 patients with thoracolumbar spine fractures (T11-L5) after bi-segmental fixateur interne montage (Group 1). A matched pair group of 33 patients (Group 2) with a 3D scan after implantation of pedicle screws was built. A postoperative computed tomography of the instrumented spinal section was done in all patients. The following measurements were done in sagittal and axial reconstruction planes and were compared: classification of screw positions, maximal axial diameter of pedicles, cortical perforation of the screws. Additionally in Group 1 the distance between the upper and lower end plates of the injured section, the height of posterior vertebral body wall, the dislocation of the posterior wall and the minimal diameter of the spinal canal were measured.

Results: The intraoperative scoring of pedicle screws positions and the measurement of pedicle width showed in both groups a significant accordance with the computed tomography determinations. The measurements "posterior wall dislocation" and "diameter of spinal canal" were only possible in 24 3D scans and showed a significant difference compared with the CT data. The picture quality in Group 2 was scored significantly better than for Group 1 with the complete assembly of the fixateur.

Conclusion: The ideal point of time for an intraoperative 3D imaging with the present intensifier generation is directly after pedicle screw insertion. The reliable determination of the spinal canal diameter, of posterior wall fragments and of the exact fracture morphology is only possible by postoperative computed tomography.