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This study is about a biomechanical comparison of some stabilization solutions for the occipitocervical junction. Four kinds of occipito-cervical fixations are analysed in this work: lateral plates fixed by two kinds of screws, lateral plates fixed by hooks and median plate. To study mechanical rigidity of each one, tests have been performed on human skulls by applying loadings and by studying mechanical response of fixations and bone. For this experimental analysis, a specific setup has been developed to impose a load corresponding to the flexion-extension physiological movements. 3D mark tracking technique is employed to measure 3D displacement fields on the bone and on the fixations. Observations of displacement evolution on the bone according to the fixation show different rigidities given by each solution.

ABSTRACT This work presents a novel methodology to generate in vitro burst fracture of spinal segments in conditions closest to trauma. Validation of this new experimental method of burst fracture production is aligned with an original experimental biomechanical analysis method. To pre-select the vertebral level of the burst fracture generation, a slight vertebral body embrittlement is envisaged. Experimental tests were performed on two groups of ovine spinal segments. An Izod impact machine was used to generate burst fracture. In one group of spinal segments, the central vertebra of each specimen was embrittled by holes of 0.8 mm diameter before impact. Both groups of spinal segments (with embrittlement and without embrittlement) were impacted and fractured. X-ray tomography was used to confirm burst fracture morphological characterization for both groups. Furthermore, to follow the mechanical response of each group, strain values were determined during impact by using non-invasive optical methods, and the compression consequences were recorded using a high-speed digital camera in real time. All fractured specimens were found to have the expected burst fracture configuration. Strain measurements allowed us to study the mechanical behaviour of spinal disks and determine the strain value (at least 5%) required to cause a burst fracture. [ABSTRACT FROM AUTHOR]

The article presents a study on the development of an experimental process in generating burst fractures. It states that an Izod machine was used to carry out impact test on spinal samples to produce burst fracture. Results show that the impact speed measures 3.4 meter per second (m/s) that corresponds to an energy approximately 80 joules (J), while 11% strain of the segment.

The article investigates the biomechanical behaviour of occipitocervical junctions that allows the determination of stiffness. It mentions that the optical method has been used to measure the range of motion (ROM) of the bone. It states that the occipitocervical fusion is obtained with a rigid fixation from an osteosynthesis between occipital bone and upper cervical spine that analyse the mechanical response of different occipital fixations.

Background: Occipito-cervical fusion can be necessary in case of cranio-cervical junction instability. Proximal stabilisation is usually ensured by bi-cortical occipital screws implanted through one median or two lateral occipital plate(s). Bone thickness variability as well as the proximity of vasculo-nervous elements can induce substantial morbidity. The choice of site and implant type remains difficult for surgeons and is often empirically based. Given this challenge, implants with smaller pitch to increase bone interfacing are being developed, as is a surgical technique consisting in inverted occipital hook clamps, a potential alternative to plate/screws association. We present here a biomechanical comparison of the different occipito-cervical fusion devices., Methods: We have developed a 3D mark tracking technique to measure experimental mechanical data on implants and occipital bone. Biomechanical tests were performed to study the mechanical stiffness of the occipito-cervical instrumentation on human skulls. Four occipital implant systems were analysed: lateral plates+large pitch screws, lateral plates+hooks, lateral plates+small pitch screws and median plate+small pitch screws. Mechanical responses were analysed using 3D displacement field measurements from optical methods and compared with an analytical model., Findings: Paradoxical mechanical responses were observed among the four types of fixations. Lateral plates+small pitch screws appear to show the best accordance of displacement field between bone/implant/system interface providing higher stiffness and an average maximum moment around 50 N.m before fracture., Interpretation: Stability of occipito-cervical fixation depends not only on the site of screws implantation and occipital bone thickness but is also directly influenced by the type of occipital implant., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The multiplicity of clinical presentations and the lack of consensus explain that the treatment of spine metastasis remains controversial. Optimal treatment requires a truly multidisciplinary approach, involving oncologists, interventional radiologists, radiation oncologists, rheumatologists and spine surgeons. Recent progress in all these areas have allowed to provide safe and effective therapeutic solutions tailored to each situation. We remind, in this work, the main progress in the surgical field, specifying the role of surgery in the current therapeutic arsenal.

Background and Importance: There is large variation in the success of decompressive surgery for pudendal neuralgia (PN), the most chronic, disabling form of perineal pain. We attempt to determine whether spinal cord stimulation using new-generation multicolumn leads could form part of the treatment algorithm for refractory PN., Clinical Presentation: A man with PN that was unresponsive to conventional treatment demonstrated a neuropathic component and had a negative response to nerve infiltrations (so he was not indicated for decompressive surgery) and a positive response to perianal transcutaneous electrical nerve stimulation and was implanted with a 16-contact surgical lead at the level of conus medullaris, allowing multicolumn stimulation. Using transverse combinations, it was possible to obtain 100% paresthesia over the perineal area without unwanted dorsal root stimulation. Perineal and radicular pain was successfully relieved for up to 12 months (80% and 60% reduction in the visual analogue scale scores, respectively), with an improvement in all quality of life domains and a reduction in drug consumption., Conclusion: Spinal cord stimulation using a 16-contact lead may be a viable therapeutic option for patients with refractory PN for whom decompressive surgery is contraindicated.

Background: Failed back surgery syndrome represents one of the most frequent etiologies of chronic back pain and is a major public health issue. Neurostimulation has currently not been validated in the treatment of back pain because of technological limitations in implantable spinal cord stimulation (SCS) systems. New-generation leads using several columns of stimulation can generate longitudinal and/or transverse stimulation fields into the spinal cord., Objective: To investigate, through extensive stimulation testing, the capacity of multicolumn tripolar leads to achieve back territory paresthesia coverage in refractory failed back surgery syndrome patients., Methods: Eleven patients implanted with a 16-contact spinal cord stimulation lead (Specify 5-6-5, Medtronic Inc) were assessed with a systematic exploration of 43 selected stimulation configurations to generate bilateral back paresthesia in addition to leg territory coverage., Results: The tripolar lead successfully generated paresthesia in both bilateral back and leg territories in 9 patients (81.8%). Success rates of multicolumn stimulation patterns were significantly higher than for longitudinal configurations for lombodorsal paresthesia coverage. Six months after implantation, significant pain relief was obtained compared with preoperative evaluation for global pain (Visual Analog Scale, 2.25 vs 8.2 preoperatively; P < .05), leg pain (Visual Analog Scale, 0.5 vs 7.6 preoperatively; P < .05), and back pain (Visual Analog Scale, 1.5 vs 7.8 preoperatively; P < .05)., Conclusion: These results suggest that multicolumn leads can reliably generate back pain coverage and favor pain relief outcomes. This may lead physicians to reconsider new indications for spinal cord stimulation. Expanding neurostimulation perspectives to intractable back pain syndromes could become realistic in the near future.

Introduction: To our knowledge, there is little reference in literature with regards to alpha3-isoform of Na+,K+-ATPase in human peripheral nerves. The aim of this study was to determine the expression of the neuronal alpha3-isoform of Na+,K+-ATPase in human sural nerves from patients with a permanent medullary central nervous system injury., Materials and Methods: We studied the immunolocalization of alpha3-isoform of Na+,K+-ATPase using a polyclonal antibody against the amino sequence near the phosphorylation site of the alpha3-isoforms of Na+,K+-ATPase using immunohistochemistry and confocal laser scanning microscopy. An antibody specific for alpha2-isoform of Na+,K+-ATPase was used to label the Schwann cells., Results: Morphometric analysis of longitudinal section of human sural nerves showed that the alpha3-isoform of Na+,K+-ATPase was distributed along the length of axolemma. The myelin sheath of the Schwann cells showed clearly a distribution of alpha3- but not alpha2-isoforms of Na+,K+-ATPase at the level of Schmidt-Lanterman incisures., Conclusion: The human sural nerve shows a specific localization of the Na+,K+-ATPase alpha3-isoform in the Schmidt-Lanterman incisures of Schwann cells in addition to its localization in axonal membranes.