PubMed · 10926248
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R J Gibson. Flexor surface material.. https://doi.org/10.1097/00005131-200006000-00014
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STUDY DESIGN: Cadaver and preliminary clinical study. OBJECTIVES: To enhance the precision of screw positions for posterior transarticular fixations according to Magerl at C1-C2. SUMMARY OF BACKGROUND DATA: The vertebral arteries are at risk during the Magerl operation and may be damaged in up to 4.1% of cases. Even intraoperative navigation, as often used nowadays, does not provide optimal screw positioning in all patients. METHODS: According to the three-dimensional CT data obtained for every individual cadaver or patient, a template was designed for the posterior course of C2: the template contains a drill guide allowing navigated screw positioning inside the left and right isthmus of C2. For a first series of five cadavers a template with clamps connecting only to the lamina of C2, excluding the spinous process from the interface, was carried out. For a second series of three cadavers the template was connected not only to the lamina but also to the spinous process of C2. Both cadaver series were performed without any fluoroscopic control at surgery. Eventually the technology was applied in two clinical cases. RESULTS: The rotational stability of the template toward the lamina C2 was insufficient in the first series, but for the second series both the entry points and screw trajectories were very satisfactory. CONCLUSIONS: Although the actual experience is limited, the idea of using a template with drill guide might simplify and shorten the surgical act and at the same time enhance the accuracy of C1-C2 transarticular screw positioning.
STUDY DESIGN: In this cadaveric study, a computer-assisted image guidance system was tested for accuracy of thoracic pedicle screw placement. OBJECTIVES: Evaluate the system's accuracy for thoracic pedicle screw placement in vitro. SUMMARY OF BACKGROUND DATA: The effective use and reliability of pedicle screw instrumentation in providing short-segment stabilization and correction of deformity is well known in the lumbar spine. Pedicle screw placement in the thoracic spine is difficult because of the small dimensions of the thoracic pedicles and risk to the adjacent spinal cord and neurovascular structures. Investigators have shown the improved accuracy of computer-assisted lumbar pedicle screw placement; but the accuracy of computer-assisted thoracic pedicle screw placement, which is becoming more widely used, has not been shown. METHODS: In five human cadavers, 120 thoracic pedicle screws were placed with computer-assisted image guidance. The largest clinically feasible screw was used based on the cross-sectional dimensions of each pedicle. The accuracy was assessed by postoperative computed tomography and visual inspection. RESULTS: The overall pedicle cortex violation was 23 of 120 pedicles (19.2%). Nine violations (7.5%) were graded as major and 14 (11.7%) as minor. A marked and progressive learning curve was evident with the perforation rates that decreased from 37.5% in the first cadaver to 4.2% in the last two cadavers. CONCLUSIONS: Accurate thoracic pedicle screw placement is feasible with computer-assisted surgery. However, as with any other new surgical technology, the learning curve must be recognized and incorporated into the necessary fundamental knowledge and experience for these procedures.