European Spine Journal. Dec 2010, Vol. 19 Issue 12, p2137, 12 p.
Clinical studies reported frequent failure with anterior instrumented multilevel cervical corpectomies. Hence, posterior augmentation was recommended but necessitates a second approach. Thus, an author group evaluated the feasibility, pull-out characteristics, and accuracy of anterior transpedicular screw (ATPS) fixation. Although first success with clinical application of ATPS has already been reported, no data exist on biomechanical characteristics of an ATPS-plate system enabling transpedicular end-level fixation in advanced instabilities. Therefore, we evaluated biomechanical qualities of an ATPS prototype C4--C7 for reduction of range of motion (ROM) and primary stability in a non-destructive setup among five constructs: anterior plate, posterior all-lateral mass screw construct, posterior construct with lateral mass screws C5 + C6 and end-level fixation using pedicle screws unilaterally or bilaterally, and a 360deg construct. 12 human spines C3--T1 were divided into two groups. Four constructs were tested in group 1 and three in group 2 the ATPS prototypes were tested in both groups. Specimens were subjected to flexibility test in a spine motion tester at intact state and after 2-level corpectomy C5--C6 with subsequent reconstruction using a distractable cage and one of the osteosynthesis mentioned above. ROM in flexion--extension, axial rotation, and lateral bending was reported as normalized values. All instrumentations but the anterior plate showed significant reduction of ROM for all directions compared to the intact state. The 360deg construct outperformed all others in terms of reducing ROM. While there were no significant differences between the 360deg and posterior constructs in flexion--extension and lateral bending, the 360deg constructs were significantly more stable in axial rotation. Concerning primary stability of ATPS prototypes, there were no significant differences compared to posterior-only constructs in flexion--extension and axial rotation. The 360deg construct showed significant differences to the ATPS prototypes in flexion--extension, while no significant differences existed in axial rotation. But in lateral bending, the ATPS prototype and the anterior plate performed significantly worse than the posterior constructs. ATPS was shown to confer increased primary stability compared to the anterior plate in flexion--extension and axial rotation with the latter yielding significance. We showed that primary stability after 2-level corpectomy reconstruction using ATPS prototypes compared favorably to posterior systems and superior to anterior plates. From the biomechanical point, the 360deg instrumentation was shown the most efficient for reconstruction of 2-level corpectomies. Further studies will elucidate whether fatigue testing will enhance the benefit of transpedicular anchorage with posterior constructs and ATPS.
European Spine Journal. Sept, 2011, Vol. 20 Issue 9, p1579, 1 p.
Byline: Heiko Koller (1,2), Rene Schmidt (3), Michael Mayer (1), Wolfgang Hitzl (4), Juliane Zenner (2), Stefan Midderhoff (5), Nicolaus Graf (5), H. Resch (1), Hans-Joachim Wilke (5) Author Affiliation: (1) Department for Traumatology and Sport Injuries, Paracelsus Medical University, Salzburg, Austria (2) German Scoliosis Center, Werner-Wicker-Clinic, Bad Wildungen, Germany (3) Department of Orthopedics and Traumatology, University Medical Center, Mannheim, Germany (4) Research Office, Department of Biostatistics, Paracelsus Medical University, Salzburg, Austria (5) Department of Orthopedic Research and Biomechanics, University of Ulm, Ulm, Germany Article History: Registration Date: 05/04/2011 Online Date: 20/04/2011 Article note: The online version of the original article can be found under doi: 10.1007/s00586-010-1503-x.
Surgical treatment of complex severe spinal deformity, involving a scoliosis Cobb angle of more than 90deg 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 118deg +- 27deg. 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 42deg +- 32deg, 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.
Lu, Sheng, Xu, Yong Q., Zhang, Yuan Z., Xie, Le, Guo, Hai, and Li, Dong P.
European Spine Journal. Sept, 2009, Vol. 18 Issue 9, p1379, 7 p.
Company business management and Rapid prototyping
The present method of C2 laminar screw placement relies on anatomical landmarks for screw placement. Placement of C2 laminar screws using drill template has not been described in the literature. The authors reported on their experience with placement of C2 laminar screws using a novel computer-assisted drill guide template in nine patients undergoing posterior occipito-cervical fusion. CT scan of C2 vertebrae was performed. 3D model of C2 vertebrae was reconstructed by software MIMICS 10.01. The 3D vertebral model was then exported in STL format, and opened in a workstation running software UG imageware12.0 for determining the optimal laminar screw size and orientation. A virtual navigational template was established according to the laminar anatomic trait. The physical vertebrae and navigational template were manufactured using rapid prototyping. The navigational template was sterilized and used intraoperative to assist the placement of laminar screw. Overall, 19 C2 laminar screws were placed and the accuracy of screw placement was confirmed with postoperative X-ray and CT scanning. There were not complications of related screws insertion. Average follow-up was 9 months (range 4--13 months), 77.8% of the patients exhibited improvement in their myelopathic symptoms in 22.2% the symptoms were unchanged. Postoperative computed tomographic (CT) scanning was available for allowing the evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. This study shows a patient-specific template technique that is easy to use, can simplify the surgical act and generates highly accurate C2 laminar screw placement. Advantages of this technology over traditional techniques include planning of the screw trajectory is done completely in the presurgical period as well as the ability to size the screw to the patient's anatomy.
European Spine Journal. May 2008, Vol. 17 Issue 5, p644, 6 p.
Full-scale three-dimensional (3D) models offer a useful tool in preoperative planning, allowing full-scale stereoscopic recognition from any direction and distance with tactile feedback. Although skills and implants have progressed with various innovations, rheumatoid cervical spine surgery remains challenging. No previous studies have documented the usefulness of full-scale 3D models in this complicated situation. The present study assessed the utility of full-scale 3D models in rheumatoid cervical spine surgery. Polyurethane or plaster 3D models of 15 full-sized occipitocervical or upper cervical spines were fabricated using rapid prototyping (stereolithography) techniques from 1-mm slices of individual CT data. A comfortable alignment for patients was reproduced from CT data obtained with the patient in a comfortable occipitocervical position. Usefulness of these models was analyzed. Using models as a template, appropriate shape of the plate-rod construct could be created in advance. No troublesome Halo-vests were needed for preoperative adjustment of occipitocervical angle. No patients complained of dysphasia following surgery. Screw entry points and trajectories were simultaneously determined with full-scale dimensions and perspective, proving particularly valuable in cases involving high-riding vertebral artery. Full-scale stereoscopic recognition has never been achieved with any existing imaging modalities. Full-scale 3D models thus appear useful and applicable to all complicated spinal surgeries. The combination of computer-assisted navigation systems and full-scale 3D models appears likely to provide much better surgical results.