Yu Yamamoto

Quantitative analysis of cation mixing and local valence states in LiNixMn2−xO4 using concurrent HARECXS and HARECES measurements

Cation mixing in positive electrode materials for rechargeable lithium ion batteries, LiNixMn2-xO4 (x = 0, 0.2, 0.5) and Li0.21Ni0.7Mn1.64O4-δ (denoted as x = 0.7), is analyzed by high-angular-resolution electron-channeling X-ray/electron spectroscopy (HARECXS/HARECES) techniques, using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. Mixing between the tetrahedral lithium sites and the octahedral transition metal sites is quantified, and the site-dependent valence states of the transition metals are examined. In the non-doped (x = 0) sample, Mn was found to occupy only octahedral sites as either Mn(3+) or Mn(4+) For x = 0.2-0.7, some of the nickel ions (6-13% depending on x) occupy tetrahedral anti-sites. All the nickel ions are in the divalent state, regardless of the occupation site. For x = 0.2 and 0.7, manganese ions occupy both octahedral and tetrahedral sites; those in the octahedral sites are tetravalent, while the tetrahedral sites contain a mixture of divalent and trivalent ions. For x = 0.5, manganese occupies only the octahedral sites, with all ions determined to be in the tetravalent state (within experimental accuracy). All the samples substantially satisfied the local charge neutrality conditions. This study demonstrates the feasibility of using HARECXS/HARECES for quantitative analysis of the atomic configuration and valence states in lithium manganese oxide spinel materials.

Hybrid Method of Transvertebral Foraminotomy Combined with Anterior Cervical Decompression and Fusion for Multilevel Cervical Disease

Transvertebral foraminotomy (TVF) combined with anterior cervical decompression and fusion (ACDF) can be used to treat multilevel cervical spondylotic myelopathy and radiculopathy; however, the radiological outcomes and effectiveness of this hybrid procedure are unknown. We retrospectively assessed 22 consecutive patients treated with combined TVF and ACDF between January 2007 and May 2016. The Japanese Orthopedic Association (JOA) score and Odom’s criteria were analyzed. Radiological assessment included the C2–7 sagittal Cobb angle (CA) and range of motion (ROM). The tilting angle (TA), TA ROM, and disc height (DH) of segments adjacent to the ACDF were also measured. Adjacent segment degeneration, which includes disc degeneration, was evaluated. The mean postoperative follow-up was 41.7 months. All surgeries were performed at two adjacent segments, with ACDF and TVF of the upper and lower segments, respectively. The JOA scores significantly improved. There were no significant differences in the C2–7 CA, C2–7 ROM, TA, and TA ROM, but there was a statistically significant decrease in DH of the lower adjacent segment to ACDF. Progression of disc degeneration was identified in two patients, with no progression in the criterion of adjacent segment degeneration over the follow-up. The TVF combined with ACDF produced excellent clinical results and maintained spinal alignment, albeit with a reduction in DH. TVF was safely performed at the lower segment adjacent to the ACDF, although this might result in earlier degeneration. In conclusion, this hybrid method is less invasive and beneficial for reduction of the number of fused levels.

Clinical and Radiological Outcomes of Microscopic Lumbar Foraminal Decompression: A Pilot Analysis of Possible Risk Factors for Restenosis

A single-center retrospective comparative study was designed to identify the risk factors for restenosis of lumbar foraminal stenosis (LFS) after microscopic foraminal decompression (MFD). 21 consecutive patients who underwent single-level MFD with an average of 19-month follow-up were divided into two study groups based on clinical outcomes; group 1 (7 patients with poor outcomes requiring revision surgery), group 2 (14 patients with good outcomes with no revision surgery required). Changes of lumbar spinal alignment on plain standing radiographs were compared and analyzed between two study groups to investigate the pathology and risk factors associated with restenosis after MFD. Preoperative disc wedging (DW) angle was significantly larger in group 1 than in group 2 (3.5 ± 1.0° vs 1.1 ± 0.2°, P < 0.01). Postoperatively, disc height (DH) and foraminal height (FH) decreased (P < 0.05), and DW deteriorated (P < 0.01) significantly in group 1, while there were no significant changes in group 2. Lumbar lordosis (LL) remarkably improved postoperatively in group 2 (24.7 ± 8.0 to 32.0 ± 7.0, P < 0.001), contrary to limited improvement in group 1 (25.1 ± 9.2 to 27.0 ± 12.0, P = 0.45). Postoperative LL is a predictive factor for restenosis after MFD. Decrease in DH or progression of DW was contributing to restenosis. LFS presenting with large DW and lumbar degenerative kyphosis should be excluded from surgical indications for MFD without instrumented fusion, considering the high recurrence rate.

Balloon Kyphoplasty under Three-dimensional Radiography Guidance

Percutaneous balloon kyphoplasty (PBKP) is generally performed under two-dimensional (2D) radiography guidance (lateral- and anteroposterior (A-P) views) using C-arm fluoroscopy. However, 2D images taken by single-plane or bi-plane fluoroscopy cannot provide information regarding axial views, particularly the Z axis. Lack of information regarding the Z axis prevents the creation of three-dimensional (3D) images. Currently, there has been a progress in interventional X-ray systems, and they are capable of providing 3D radiographic images using a rotational angiography mode which is used to create 3D angiographies. In this report, we described the usefulness of 3D radiography guidance. Patients treated by PBKP was designed to evaluate the efficacy of 3D radiography guidance. These patients experienced osteoporotic vertebral fractures with severe pain. We retrospectively analyzed patients who underwent PBKP from February to December 2016. All patients had a single-level vertebral fracture and underwent surgery by 2D or 3D radiography guidance. We performed 16 patients in 3D radiography guidance, and 10 patients in traditional 2D radiography guidance. This 3D radiography guided PBKP increase the amount of the polymethyl methacrylate (PMMA) injection compared with ordinary 2D method. As a result, postoperative vertebral height and alignment were significantly improved. Both groups have no complication. To confirm the final results and make PBKP more effective, 3D radiography guidance is feasible and safe for balloon kyphoplasty.

O-arm Imaging and Naviation Systems for Transvertebral Anterior Cervical Foraminotomy

Introduction Anterior cervical discectomy and fusion (ACDF) results in excellent initial clinical results for herniated cervical disc and an osteophyte. On the other hand, the development of adjacent segment disease after ACDF is well recognized. However, most patients do not require total discectomy and vertebral fusion because most radiculopathies are caused by focal lesions of the intervertebral foramen. Especially, in patients who have unilateral radiculopathy with physiological alignment, we should avoid removal of healthy discs. Transvertebral anterior cervical foraminotomy (TVACF), nonfusion and nondiscectomy technique, can preserve intervertebral disc and reduce adjacent intervertebral degeneration compared with intervertebral fusion. Therefore, we have reported the advantages and usefulness of TVACF. However, TVACF requires skillfulness, especially for the appropriate drilling direction control for the keyhole. Recently, O-arm imaging and navigation systems were progressed. This navigation systems help to make the correct direction of the keyhole. Material and Methods We have performed TVACF under O-arm imaging and naviation systems. The patient was placed in the supine position. A lateral radiograph was used to identify the skin incision level. A 3.5cm transverse skin incision was made at half a level higher than the affected disc level. We approached the anterior surface of the vertebra from the affected side. After then, O-arm imaging and navigation systems were applied. We determined the appropriate keyhole position under the navigation. The lateral and caudal side trajectory of the tunnel was also decided under the navigation. The tunnel was ~6 mm in diameter. Results Under O-arm imaging and navigation systems, we were able to easily determine the appropriate keyhole position and the lateral and caudal side trajectory of the tunnel. Intraoperative findings and postoperative computed tomography imaging showed the accuracy of keyhole position. Conclusion Successful surgery is possible with using O-arm imaging and navigation systems. This navigation facilitate TVACF. As a result, TVACF is able to be more widely used among spinal surgeons in safe.

Biomechanical Analysis of a Pedicle Screw-Rod System with a Novel Cross-Link Configuration

Study Design The strength effects of a pedicle screw-rod system supplemented with a novel cross-link configuration were biomechanically evaluated in porcine spines. Purpose To assess the biomechanical differences between a conventional cross-link pedicle screw-rod system versus a novel cross-link instrumentation, and to determine the effect of the cross-links. Overview of Literature Transverse cross-link systems affect torsional rigidity, but are thought to have little impact on the sagittal motion of spinal constructs. We tested the strength effects in pullout and flexion-compression tests of novel cross-link pedicle screw constructs using porcine thoracic and lumbar vertebrae. Methods Five matched thoracic and lumbar vertebral segments from 15 porcine spines were instrumented with 5.0-mm pedicle screws, which were then connected with 6.0-mm rods after partial corpectomy in the middle vertebral body. The forces required for construct failure in pullout and flexion-compression tests were examined in a randomized manner for three different cross-link configurations: un-cross-link control, conventional cross-link, and cross-link passing through the base of the spinous process. Statistical comparisons of strength data were analyzed using Students t-tests. Results The spinous process group required a significantly greater pullout force for construct failure than the control group (p=0.036). No difference was found between the control and cross-link groups, or the cross-link and spinous process groups in pullout testing. In flexion-compression testing, the spinous processes group required significantly greater forces for construct failure than the control and cross-link groups (p<0.001 and p=0.003, respectively). However, there was no difference between the control and cross-link groups. Conclusions A novel cross-link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and flexion-compression testing compared to un-cross-link constructs. This configuration provided more resistance to middle-column damage under flexion-compression testing than conventional cross-link configuration.

Site-by-site electronic structure analysis of al-containing complex compounds using channeling EELS and first principles calculations

Al K ELNES of oxide ceramics, which show reverse spinel and garnet structures containing two types of Al sites, are investigated site-selectively using TEM-EELS under electron channeling conditions. We applied a self-modeling curve resolution (SMCR) technique to separate a set of experimental spectra into individual spectra of individual atomic sites. The refined spectra after SMCR were in consistent with the theoretical spectra obtained by the first principles electronic structure calculations. The spectral difference of the six-coordinated aluminum between the two materials was discussed in terms of the cationic coordination.