Endoscopic Transnasal Odontoidectomy

Background Odontoidectomy may represent the treatment of choice for symptomatic ventral craniovertebral junction stenosis in selected cases. An endoscopic transnasal approach has been proposed as an alternative to a classic transoral approach. Method We report a case of a patient with a craniovertebral junction stenosis due to the ossification of the posterior ligament. The clinical and radiological records of the patient and a step-by-step description of the surgical technique are presented (Fig. 1). Conclusion Endoscopic transnasal odontoidectomy provides a direct access to the dens and adjacent structures of the anterior upper cervical spine with a less invasive burden on the oropharingeal structures.The link to the video can be found at: https://youtu.be/Ofrk1sFTV9I.

Individualized artificial titanium alloy spinal lamina with 3D printing technology

Background: Laminectomy and decompression is a common procedure for treating spine diseases. However, due to the lack of a posterior, bony braced structure, the dural sac and nerve roots can adhere to the surrounding tissues, and scar formation can occur in muscle and soft tissues. This can cause new compression post surgery, and failure of the operation. Objective: This study aimed to produce an individualized titanium alloy spine lamina using 3D printing technology, and to evaluate its effectiveness by implantation in human cadaveric spines. Methods: Six adult lumbar cadaver specimens were used, and computed tomography (CT) was used to obtain DICOM medical digital image standard data. The lumbar vertebrae structure was reconstructed by three-dimensional (3D) modeling software, and then simulated lumbar laminectomy was performed. Based on the characteristics of the original lamina, an artificial spine lamina was designed, including suture holes at the posterior ligament attachment point and a locking screw hole for fixation. A titanium alloy spine lamina was fabricated by 3D printing, and a guide plate to assist artificial lamina implantation was designed. Using the guide plated, L4 lumbar vertebrae segment laminectomy was performed on the 6 lumbar spine specimens, titanium alloy spine lamina were implanted and fixed with cortical bone trajectory screws. After implantation, CT was performed to record the length of the screw, the trajectory of the screw in the pedicle, and changes of bony spinal canal volume and anteroposterior diameter of the spinal canal. Results: The morphology of artificial spine lamina matched that of the original lamina. The artificial lamina was easy to implant, and matched the original lamina. The laminas were fixed by 12 cortical screws (diameter, 4.5 mm; median length, 34.67 ± 1.97 mm). CT scan indicated that all screws passed through the pedicle cortex by < 2 mm (2 screws penetrated the inner wall). The bony canal volume of the L4 vertebral pedicle was 311.23 ± 38.17 mm2 before operation and 356.17 ± 43.11 mm2 after operation, and there was statistical difference (P < 0.001). The anteroposterior diameter of spinal canal was 17.82 ± 2.03 mm before surgery and 20.67 ± 2.38 mm after surgery, and they were statistically different (P < 0.001). Conclusion: An individualized artificial titanium alloy spine lamina designed and produced with 3D printing technology can be used to reconstruct the structure of the posterior spine complex after lumbar laminectomy. The artificial lamina can increase the volume of the spinal canal and provide a posterior ligament reconstruction attachment point.

Shear stiffness in the lower cervical spine: Effect of sequential posterior element injury

The aim of this study was to determine the effect of the posterior ligaments and facet joints on the shear stiffness of lower cervical functional spinal units in anterior, posterior, and lateral shear. Five functional spinal units were loaded in anterior, posterior, and right lateral shear up to 100 N using a custom-designed apparatus in a materials testing machine. Specimens were tested in three conditions: intact, with the posterior ligaments severed, and with the facet joints removed. There was a significant decrease in anterior stiffness in the 20–100 N load range from 186 (range: 98–327) N/mm in the intact condition to 105 (range: 78–142) N/mm in the disc-only condition (p = 0.03). Posterior stiffness between these condition decreased significantly from 134 (range: 92–182) N/mm to 119 (range: 83–181) N/mm (p = 0.03). There was no significant effect of posterior ligament removal on shear stiffness. No significant differences were found in the lateral direction or in the 0–20 N range for any direction. Under a 100-N shear load, the facet joints played a significant role in the stiffness of the cervical spine in the anterior–posterior direction, but not in the lateral direction.

Assessment of Interobserver Variability for CT Scan–Based Evaluation of Posterior Ligament Complex Injury in Thoracolumbar Fractures: An International Multicenter Pilot Study

Study Design: A multicenter, pilot study, for radiological assessment of thoracolumbar spine fractures was performed with the participation of 7 centers in Africa, Europe, Asia, and South America as a part of the AO Foundation network. Objectives: To determine the interobserver variability for computed tomography (CT) scan–based evaluation of posterior ligament complex (PLC) injury in thoracolumbar fractures. Methods: Forty-two observers including 1 principal investigator at each participating center performed variability assessment. Each center contributed toward a total of 91 patient images with A3 or A4 thoracolumbar burst fractures (T11-L2) with or without suspected PLC injury. Pathological fractures, multilevel injuries, obvious posterior bony element injury and translation/dislocation injuries were excluded. Ten patients were randomly selected and commonly reported CT parameters indicating PLC injury, including superior inferior endplate angle, vertebral body height loss, local kyphotic deformity, interspinous distance and interpedicular distance were assessed for variability. Observer values were compared with an experienced gold rater in spinal trauma. Analysis of variability was performed for all observers, between the principal investigators and also between observers participating in each center. Results: The studied parameters showed considerable variability in measurements among all observers and amongst all participating centers. The variability between the principal investigators was lower, but still substantial. The deviation of observer measurements from the gold rater were also significant for all CT parameters. Conclusions: CT-based radiological parameters previously reported to be suggestive of PLC injury showed considerable variability and magnetic resonance imaging verification of a PLC injury in all doubtful cases is suggested.