Background: Lumbar spinal fusion with rigid spinal fixators as one of the high risk factors related to adjacent-segment failure. The purpose of this study is to investigate how the material properties of spinal fixation rods influence the biomechanical behavior at the instrumented and adjacent levels through the use of the finite element method. Methods: Five finite element models were constructed in our study to simulate the human spine pre- and post-surgery. For the four post-surgical models, the spines were implanted with rods made of three different materials: (i) titanium rod, (ii) PEEK rod with interbody PEEK cage, (iii) Biodegradable rod with interbody PEEK cage, and (iv) PEEK cage without pedicle screw fixation (no rods). Results: Fusion of the lumbar spine using PEEK or biodegradable rods allowed a similar ROM at both the fusion and adjacent levels under all conditions. The models with PEEK and biodegradable rods also showed a similar increase in contact forces at adjacent facet joints, but both were less than the model with a titanium rod. Conclusions: Flexible rods or cages with non-instrumented fusion can mitigate the increased contact forces on adjacent facet joints typically found following spinal fixation, and could also reduce the level of stress shielding at the bone graft.

Minimally invasive spine surgery has become increasingly popular in clinical practice, and it offers patients the potential benefits of reduced blood loss, wound pain, and infection risk and also diminishes the loss of working time and length of hospital stay. However, surgeons require more intraoperative fluoroscopy and ionizing radiation exposure during minimally invasive spine surgery for localization, especially for guidance in instrumentation placement. In addition, computer navigation is not accessible in some facility-limited institutions.To demonstrate a method for percutaneous screws placement using only the anterior-posterior trajectory of intraoperative fluoroscopy.Technical report; a retrospective and prospective case series.Patients who received posterior fixation with percutaneous pedicle screws for thoraco-lumbar degenerative disease or trauma.We retrospectively reviewed the charts of consecutive 670 patients who received 4072 pedicle screws between December 2010 and August 2015. Another case series study was conducted prospectively in three additional hospitals, and 88 consecutive patients with 413 pedicle screws were enrolled from February 2014 to July 2016. The fluoroscopy shot number and radiation dose were recorded. In the prospective study, 78 patients with 371 screws received computed tomography at 3 months post-operatively to evaluate the fusion condition and screw positions.In the retrospective series, the placement of a percutaneous screw required 5.1 shots (2-14, SD = 2.366) of anterior-posterior fluoroscopy. One screw was revised due to a medial wall breach of the pedicle. In the prospective series, 5.8 shots (2-16, SD = 2.669) were required for one percutaneous pedicle screw placement. There were two screws with a grade 1 breach (8.6%), both at the lateral wall of the pedicle, out of 23 screws placed at the thoracic spine at T9-12. For the lumbar and sacral area, there were 15 grade 1 breaches (4.3%), 1 grade 2 breach (0.3%), and 1 grade 3 breach (0.3%). No revision surgery was necessary.This method avoids lateral shots of fluoroscopy during screw placement and thus decreases the operation time and exposes surgeons to less radiation. At the same time, compared with the computer-navigated procedure, it is less facility-demanding, and provides satisfactory reliability and accuracy.

Over the last few years, new treatments for a damaged intervertebral disc (IVD) have included strategies to repair, replace, or regenerate the degenerative disc. However, these techniques are likely to have limited success, due to insufficiently effective means to address the damaged anulus fibrosus (AF). Here, we try to develop a bioprocess method for decellularization of the xenogeneic AF tissue, with a view to developing a scaffold as a potential candidate for clinical application in spinal surgery. Porcine AFs were decellularized using freeze-thaw cycles, followed by various combined treatments with 0.1% sodium dodecyl sulfate (SDS) and nucleases. Hematoxylin and eosin (H & E) staining showed that decellularization was achieved through the decellularization protocols. Biochemical analyses revealed 86% reduction in DNA, but only 15.9% reduction in glycosaminoglycan (GAG) content, with no significant difference in the hydroxyproline content. There was no appreciable cytotoxicity of the acellular AF. Biomechanical testing of the acellular AF found no significant decline in stiffness or Young’s modulus. Porcine AF tissues were effectively decellularized with the preservation of biologic composition and mechanical properties. These results demonstrate that acellular AF scaffolds would be a potential candidate for clinical application in spinal surgery.