Isolated injuries of the sacral bone are rare. The pathomechanism of these injuries are usually high velocity accidents or falls from large heights. The computer-assisted implantation of iliosacral screws (SI-screw) becomes more important in the treatment of dorsal pelvic ring fractures. The advantage of the minimal-invasive screw placement is the reduction of the non-union and deep wound infection rate. Another advantage of computer-navigated SI-screw placement is the reduction of intraoperative radiation for the patient and the surgical staff. The purpose of this study was to analyse the position of navigated iliosacral screws. In the study group 74 screws (49 patients) were included and radiologically analysed. All screws were implanted using 3D-navigation (BrainLAB Vector Vision, Brainlab, Germany). Navigation was always executed with the same 3D c-arm (ARCADIS Orbic 3D, Siemens, Germany) and navigation system. We determined the grade of perforation and angular deviation in the postoperative CT-scans in all screws. The classification was performed according to Smith et al in 4 grades. Grade 0 implies no perforation and grade 1 a perforation less than 2 mm. Grade 2 correlates a perforation of 2–4 mm and grade 3 a perforation of more than 4 mm. Furthermore the intra- and postoperative complications as well as the body-mass-index, the co-morbidities and the duration of radiation were documented. The statistical analysis was executed using Microsoft Excel 2003.INTRODUCTION
METHODS
Fusion is the main goal in the surgical management of the injured and unstable spine. A wide variety of implants is available to enhance this. Our study was performed to evaluate the stabilising characteristics of several anterior, posterior and combined systems of fixation. Six thoracolumbar (T11 to L2) spines from 13-week-old calves were first tested intact. Then the vertebral body of T13 was removed and the defect replaced and supported by a wooden block to simulate bone grafting. Dorsal implants consisting of a Universal Spine System (USS) fracture system and an AO The dorsal systems limited ROM in flexion below 0.9° and in extension between 3.3° and 3.6° (median values). The improved Kaneda System SR yielded a mean ROM of 1.8° in flexion and in extension. The median rotation found with the VentroFix (SC/DR) was 3.2° for flexion and 2.8° for extension. Reinforcement of the ventral constructs with a dorsal system reduced the ROM in flexion and extension in all cases to 0.4° and lower. In rotation, the median ROM of the anterior systems ranged from 2.7° to 5.1° and for the posterior systems from 3.9° to 5.7°, while the combinations provided a ROM of 1.2° to 1.9°. In lateral bending, the posterior implants restricted movement to 1.1°, whereas the anterior implants allowed up to 5.2°. The combined systems provided the highest stability at less than 0.6°. Our study revealed distinct differences between posterior and anterior approaches in all primary directions. Also, different stabilisation characteristics were found within the anterior and posterior groups. Combinations of these two approaches provided the highest stability in all directions.
