First-Principles Investigations on the Semiconductor-to-Metal Phase Transition of 2D Si2Te3 for Reversible Resistive Switching.

Si2Te3 is attracting attention due to its compatibility with Si technology while still showing advantages as a two-dimensional layered material. Although recent experimental studies have observed the resistive switching process in Si2Te3-based memristors, the mechanism has not been clearly identified. In this study, first-principles density functional theory calculations are employed to understand the relationship between the phase transition of Si2Te3 and the reversible resistive switching of the Si2Te3-based memristor. Our calculation results show that although semiconducting Si2Te3 is energetically more stable than two metallic Si2Te3 phases (α and ß), two metallic Si2Te3 can be energetically stabilized by excess holes. The enhanced energetic preference of two metallic Si2Te3 by excess holes is explained by the reduced occupation of antibonding states between Si and Te. Our study finds that the energy barrier for the phase transition between semiconducting Si2Te3 and α-metallic Si2Te3 varies significantly by excess charge carriers so the phase transition can be directly connected to the reversible resistive switching of the Si2Te3-based memristor under external bias. Our finding will serve as a cornerstone for optimizing the resistive switching process of the Si2Te3-based memristor.

Cooperative coupling of anisotropic phonon modes intensifies visible thermochromism in layered α-MoO3.

Applications that provide versatile, high temperature warnings require the development of thermochromic materials based on solid-state oxides. To boost the visible thermochromic properties, a fundamental approach to reveal the unclear roles of local structure on band structure modulation should be considered by scrutinizing the thermal motion of phonon modes. Herein, we demonstrate that selective coupling of intra-layer phonon modes intensifies the visible thermochromism of layered oxides α-MoO3. As a result of thermally induced band gap reduction in α-MoO3, the observed color reversibly changes from white at 25 °C to yellow at 300 °C owing to a red shift of the absorption edge with an increase of temperature. This high-temperature thermochromism is attributed to the anisotropic change of layered α-MoO3 crystal structures characterized by synchrotron X-ray diffraction. Notably, quantitative characterizations combined with theoretical calculations reveal that the cooperative coupling of active Raman modes in intra-layer [MoO6] octahedra are responsible for the band gap reduction at high temperature; this defies the general belief regarding the origin of visible thermochromism in layered oxides as the modulation of a van der Waals inter-layer distance. These original results can aid the development of a new strategy to further intensify high-temperature thermochromism by anion doping for highly sensitive temperature-indicating applications.

Highly Stable Germanium Microparticle Anodes with a Hybrid Conductive Shell for High Volumetric and Fast Lithium Storage.

The ability to realize a highly capacitive/conductive electrode is an essential factor in large-scale devices, requiring a high-power/energy density system. Germanium is a feasible candidate as an anode material of lithium-ion batteries to meet the demands. However, the application is constrained due to low charge conductivity and large volume change on cycles. Here, we design a hybrid conductive shell of multi-component titanium oxide on a germanium microstructure. The shell enables facile hybrid ionic/electronic conductivity for swift charge mobility in the germanium anode, revealed through computational calculation and consecutive measurement of electrochemical impedance spectroscopy. Furthermore, a well-constructed electrode features a high initial Coulombic efficiency (90.6%) and stable cycle life for 800 cycles (capacity retention of 90.4%) for a fast-charging system. The stress-resilient properties of dense microparticle facilitate to alleviate structural failure toward high volumetric (up to 1737 W h L-1) and power density (767 W h L-1 at 7280 W L-1) of full cells, paired with highly loaded NCM811 in practical application.

A-Site Effect on the Oxidation Process of Sn-Halide Perovskite: First-Principles Calculations.

Tin-halide perovskite solar cells (Sn-PSCs) are promising candidates as an alternative to toxic lead-halide PSCs. However, Sn2+ is easily oxidized to Sn4+, so Sn-PSCs are unstable in air. Here, we use first-principles density functional theory calculations to elucidate the oxidation process of Sn2+ at the surface of ASnBr3 [A = Cs or CH3NH3 (MA)]. Regardless of the A-site cation, adsorption of O2 leads to the formation of SnO2, which creates a Sn vacancy at the surface. The A-site cation determines whether the created vacancies are stabilized in the bulk or at the surface. For CsSnBr3, the Sn vacancy is stabilized at the surface, so further oxidation is limited. For MASnBr3, the Sn vacancy moves into bulk region, so additional Sn is supplied to the surface; as a result, a continuous oxidation process can occur. The stabilization of Sn vacancy is closely related to the polarization that the A-site cation causes in the system.

First-Principles Investigations to Evaluate the Spin-Polarized Metal-to-Insulator Transition of Halide Cuprite Perovskites for Smart Windows.

Although smart windows have received wide attention as energy-saving devices, conventional metal-to-insulator materials such as VO2 hinder their commercial usage because of their high transition temperature and low solar energy modulation. Further development can be achieved by finding a new material system that can effectively overcome these limitations. In this study, first-principles density functional theory calculations are used to investigate the possibility of exploiting a spin-polarized band gap material for smart window applications. Halide cuprite perovskites (A2CuX4) were chosen because they have a spin-polarized band gap that can be tuned by element selection at sites A and X. Our study shows that the optical transmittance of the insulating phase is increased by a violation of the selection rule. The spin-polarized band gap is closely related to the metal-to-insulator transition temperature and can be modulated by chemical engineering, strain engineering, or both. Therefore, A2CuX4 is a promising candidate for smart windows.

Electron-hole separation in ferroelectric oxides for efficient photovoltaic responses.

Despite their potential to exceed the theoretical Shockley-Queisser limit, ferroelectric photovoltaics (FPVs) have performed inefficiently due to their extremely low photocurrents. Incorporating Bi2FeCrO6 (BFCO) as the light absorber in FPVs has recently led to impressively high and record photocurrents [Nechache R, et al. (2015) Nat Photonics 9:61-67], which has revived the FPV field. However, our understanding of this remarkable phenomenon is far from satisfactory. Here, we use first-principles calculations to determine that such excellent performance mainly lies in the efficient separation of electron-hole (e-h) pairs. We show that photoexcited electrons and holes in BFCO are spatially separated on the Fe and Cr sites, respectively. This separation is much more pronounced in disordered BFCO phases, which adequately explains the observed exceptional PV responses. We further establish a design strategy to discover next-generation FPV materials. By exploring 44 additional Bi-based double-perovskite oxides, we suggest five active-layer materials that offer a combination of strong e-h separations and visible-light absorptions for FPV applications. Our work indicates that charge separation is the most important issue to be addressed for FPVs to compete with conventional devices.

Hydrogen-doped Brookite TiO2 Nanobullets Array as a Novel Photoanode for Efficient Solar Water Splitting.

As a representative photocatalyst for photoelectrochemical solar water splitting, TiO2 has been intensively studied but most researches have focused on the rutile and anatsase phases because brookite, another important crystalline polymorph of TiO2, rarely exists in nature and is difficult to synthesize. In this work, hydrogen doped brookite (H:brookite) nanobullet arrays were synthesized via a well-designed solution reaction for the first time. H:brookite shows highly improved PEC properties with excellent stability, enhanced photocurrent, and significantly high Faradaic efficiency for overall solar water splitting. To support the experimental data, ab initio density functional theory calculations were also conducted. At the interstitial doping site that has minimum formation energy, the hydrogen atoms act as shallow donors and exist as H+. which has the minimum formation energy among three states of hydrogen (H+. H0, and H-). The calculated density of states of H:brookite shows a narrowed bandgap and an increased electron density compared to the pristine brookite. The combined experimental and theoretical results provide frameworks for the exploration of the PEC properties of doped brookite and extend our knowledge regarding the undiscovered properties of brookite of TiO2.

The nature of hydrogen-bonding interaction in the prototypic hybrid halide perovskite, tetragonal CH3NH3PbI3.

In spite of the key role of hydrogen bonding in the structural stabilization of the prototypic hybrid halide perovskite, CH3NH3PbI3 (MAPbI3), little progress has been made in our in-depth understanding of the hydrogen-bonding interaction between the MA(+)-ion and the iodide ions in the PbI6-octahedron network. Herein, we show that there exist two distinct types of the hydrogen-bonding interaction, naming α- and ß-modes, in the tetragonal MAPbI3 on the basis of symmetry argument and density-functional theory calculations. The computed Kohn-Sham (K-S) energy difference between these two interaction modes is 45.14 meV per MA-site with the α-interaction mode being responsible for the stable hydrogen-bonding network. The computed bandgap (Eg) is also affected by the hydrogen-bonding mode, with Eg of the α-interaction mode (1.73 eV) being significantly narrower than that of the ß-interaction mode (2.03 eV). We have further estimated the individual bonding strength for the ten relevant hydrogen bonds having a bond critical point.

A Biomechanical Analysis of an Artificial Disc With a Shock-absorbing Core Property by Using Whole-cervical Spine Finite Element Analysis.

STUDY DESIGN: A biomechanical comparison among the intact C2 to C7 segments, the C5 to C6 segments implanted with fusion cage, and three different artificial disc replacements (ADRs) by finite element (FE) model creation reflecting the entire cervical spine below C2. OBJECTIVE: The aim of this study was to analyze the biomechanical changes in subaxial cervical spine after ADR and to verify the efficacy of a new mobile core artificial disc Baguera C that is designed to absorb shock. SUMMARY OF BACKGROUND DATA: Scarce references could be found and compared regarding the cervical ADR devices' biomechanical differences that are consequently related to their different clinical results. METHODS: One fusion device (CJ cage system, WINNOVA) and three different cervical artificial discs (Prodisc-C Nova (DePuy Synthes), Discocerv (Scient'x/Alphatec), Baguera C (Spineart)) were inserted at C5-6 disc space inside the FE model and analyzed. Hybrid loading conditions, under bending moments of 1 Nm along flexion, extension, lateral bending, and axial rotation with a compressive force of 50 N along the follower loading direction, were used in this study. Biomechanical behaviors such as segmental mobility, facet joint forces, and possible wear debris phenomenon inside the core were investigated. RESULTS: The segmental motions as well as facet joint forces were exaggerated after ADR regardless of type of the devices. The Baguera C mimicked the intact cervical spine regarding the location of the center of rotation only during the flexion moment. It also showed a relatively wider distribution of the contact area and significantly lower contact pressure distribution on the core than the other two devices. A "lift off" phenomenon was noted for other two devices according to the specific loading condition. CONCLUSION: The mobile core artificial disc Baguera C can be considered biomechanically superior to other devices by demonstrating no "lift off" phenomenon, and significantly lower contact pressure distribution on core. LEVEL OF EVIDENCE: N/A.

Clinical significance of achieving a flexion limitation with a tension band system in grade 1 degenerative spondylolisthesis: a minimum 5-year follow-up.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: To evaluate the effect of the limitation of flexion rotation clinically and radiologically after interspinous soft stabilization using a tension band system in grade 1 degenerative spondylolisthesis. SUMMARY OF BACKGROUND DATA: Although several studies have been published on the clinical effects of limiting rotatory motion using tension band systems, which mainly targets the limitation of flexion rather than that of extension, they were confined to the category of pedicle screw-based systems, revealing inconsistent long-term outcomes. METHODS: Sixty-one patients with a mean age of 60.6 years (range, 28-76 yr) who underwent interspinous soft stabilization after decompression for grade 1 degenerative spondylolisthesis with stenosis between 2002 and 2004 were analyzed. At follow-up, the patients were divided into 2 groups on the basis of their achievement or failure to achieve flexion limitation. The clinical and radiological findings were analyzed. A multiple linear regression analysis was performed to determine the prognostic factors for surgical outcomes. RESULTS: At a mean follow-up duration of 72.5 months (range, 61-82 mo), 51 patients were classified into the flexion-limited group and 10 into the flexion-unlimited group. Statistically significant improvements were noted only in the flexion-limited group in all clinical scores. In the flexion-unlimited group, there were significant deteriorations in flexion angle (P = 0.009), axial thickness of the ligamentum flavum (P = 0.013), and the foraminal cross-sectional area (P = 0.011), resulting in significant intergroup differences. The preoperative extension angle was identified as the most influential variable for the flexion limitation and the clinical outcomes. CONCLUSION: The effects of the limitation of flexion rotation achieved through interspinous soft stabilization using a tension band system after decompression were related to the prevention of late recurrent stenosis and resultant radicular pain caused by flexion instability. The extension potential at the index level was recognized as a major prognostic factor that can predict the flexion limitation and the clinical results. LEVEL OF EVIDENCE: 4.

Unsuccessful percutaneous endoscopic lumbar discectomy: a single-center experience of 10,228 cases.

BACKGROUND: Percutaneous endoscopic lumbar discectomy (PELD) has remarkably evolved with successful results. Although PELD has gained popularity for the treatment of herniated disc (HD), the risk of surgical failure may be a major obstacle to performing PELD. We analyzed unsuccessful cases requiring reoperation. OBJECTIVE: To find common causes of surgical failure and elucidate the limitations of the conventional PELD technique. METHODS: A retrospective review was performed on all patients who had undergone PELD between January 2001 and December 2012. Unsuccessful PELD was defined as a case requiring reoperation within 6 weeks after primary surgery. Chart review was done, and preoperative, intraoperative, and postoperative radiographic reviews were performed. All unsuccessful PELD cases were classified according to the type of HD, location of herniation, extruded disc migration, working channel position, and intraoperative and postoperative findings. RESULTS: In 12 years, 10,228 patients had undergone PELD; 436 (4.3%) cases were unsuccessful. The causes were incomplete removal of HDs in 283 patients (2.8%), recurrence in 78 (0.8%), persistent pain even after complete HD removal in 41 (0.4%), and approach-related pain in 21 (0.2%). Incomplete removal of the HD was caused by inappropriate positioning (95 cases; 33.6%) of the working channel and occurred in central HDs (91 cases; 32.2%), migrated HDs (70 cases; 24.7%), and axillary type HDs (63 cases; 22.3%). CONCLUSION: Proper surgical indications and good working channel position are important for successful PELD. PELD techniques should be specifically designed to remove the disc fragments in various types of HD.

Clinical and radiographic changes after percutaneous endoscopic cervical discectomy: a long-term follow-up.

OBJECTIVE: Results following anterior cervical discectomy (ACD) without fusion are not well reported because of skepticism that the disturbed cervical spine anatomy after ACD might compromise clinical outcome. The purpose of this study was to determine whether ACD without fusion prompts the degenerative process significantly, and whether it is necessary to preserve disc height and cervical alignment for the sake of better clinical outcome following cervical spine surgery. BACKGROUND DATA: Out of 56 consecutive patients, 37 patients who replied and consequently underwent postoperative MRI from April to June 2009 were included in this study. MATERIAL AND METHODS: A total of 37 consecutive patients diagnosed as having cervical monoradiculopathy and treated with percutaneous endoscopic cervical discectomy (PECD) were investigated. Angle of cervical lordosis, change in cervical range of motion, disc height change, and degree of degenerative changes at the corresponding level were evaluated. The visual analogue scale (VAS) score for neck and arm pain and the neck disability index (NDI) were compared preoperatively and at the final follow-up. The mean follow-up period was 45.5 months. RESULTS: Despite prompted radiological deterioration such as loss of disc height (the posterior disc heights and central disc height ratio were significantly decreased from 3.6 to 2.6 mm, from 30.3% to 24.5%, respectively, p<0.05) or degenerative progression (from average grade of 2.8 to 4.1, p<0.05), the patients achieved significant improvement in clinical outcomes (VAS for neck and arm dropped from mean 6.3 and 7.5 to 2.7 and 2.6, respectively, and NDI score improved from 46.8% to 17.2%, p<0.05) after PECD. CONCLUSIONS: Neither loss of disc height nor progression of degeneration at disc space compromised clinical outcome after PECD without fusion on long-term follow-up.

Comparison of cervical kinematics between patients with cervical artificial disc replacement and anterior cervical discectomy and fusion for cervical disc herniation.

BACKGROUND CONTEXT: Although anterior cervical discectomy and fusion (ACDF) is an effective treatment option for patients with cervical disc herniation, it limits cervical range of motion, which sometimes causes discomfort and leads to biomechanical stress at neighboring segments. In contrast, cervical artificial disc replacement (ADR) is supposed to preserve normal cervical range of motion than ACDF. A biomechanical measurement is necessary to identify the advantages and clinical implications of ADR. However, literature is scarce about this topic and in those available studies, authors used the static radiological method, which cannot identify three-dimensional motion and coupled movement during motion of one axis. PURPOSE: The purpose of this study was to compare the clinical parameters and cervical motion by three-dimensional motion analysis between ACDF and ADR and to investigate the ability of ADR to maintain cervical kinematics. STUDY DESIGN: This was a prospective case control study. PATIENT SAMPLE: Patients who underwent ADR or ACDF for the treatment of single-level cervical disc herniation. OUTCOME MEASURES: Visual analog scale (VAS), Korean version of Neck Disability Index (NDI, %), and three-dimensional motion analysis were used. METHODS: The patients were evaluated by VAS and the Korean version of the NDI (%) to assess pain degree and functional status. Cervical motions were assessed by three-dimensional motion analysis in terms of sagittal, coronal, and horizontal planes. Markers of 2.5 cm in diameter were attached at frontal polar (Fpz), center (Cz), and occipital (Oz) of 10-20 system of electroencephalography, C7 spinous process, and both acromions. These evaluations were performed preoperatively and 1 month and 6 months after surgery. RESULTS: The ACDF and ADR groups revealed no significant difference in VAS, NDI (%), and cervical range of motion preoperatively. After surgery, both groups showed no significant difference in VAS and NDI (%). In motion analysis, significantly more range of motion was retained in flexion and extension in the ADR group than the ACDF group at 1 month and 6 months. There was no significant difference in lateral tilt and rotation angle. In terms of coupled motion, ADR group exhibited significantly more preserved sagittal plane motion during right and left rotation and also showed significantly more preserved right lateral bending angle during right rotation than ACDF group at 1 month and 6 months. There was no significant difference in other coupled motions. CONCLUSION: Three-dimensional motion analysis could provide useful information in an objective and quantitative way about cervical motion after surgery. In addition, it allowed us to measure not only main motion but also coupled motion in three planes. ADR demonstrated better retained cervical motion mainly in sagittal plane (flexion and extension) and better preserved coupled sagittal and coronal motion during transverse plane motion than ACDF. ADR had the advantage in that it had the ability to preserve more cervical motions after surgery than ACDF.

The efficacy of hydroxyapatite for screw augmentation in osteoporotic patients.

The stability of screw constructs is of considerable importance in determining the outcome, especially in spinal osteoporosis. Polymethylmethacrylate (PMMA) has been proven as an effective material for increasing the pullout strength of pedicle screws inserted into the osteoporotic bones. However, PMMA has several disadvantages, such as its exothermic properties, the risk of neural injury in the event of extravasation, and difficulties in performing revision surgery. In the current study, we used hydroxyapatite (HA) cement for screw augmentation in spinal osteoporosis. We conclude that HA cement is a useful tool for screw augmentation and recommend it as a promising option for spinal instrumentation in osteoporotic patients.

Radiation exposure to the surgeon during percutaneous endoscopic lumbar discectomy: a prospective study.

STUDY DESIGN: A prospective study. OBJECTIVE: The purpose of this study was to determine the radiation dose to which the surgeons are exposed during percutaneous endoscopic lumbar discectomy (PELD) and to calculate the allowable number of cases per year. SUMMARY OF BACKGROUND DATA: Transforaminal PELD is a minimally invasive technique for soft disc herniation. Minimal invasiveness can be achieved through the use of fluoroscopy and endoscopy. The radiation dose to the surgeon during PELD is unknown. METHODS: The occupational radiation dose absorbed by 3 spinal surgeons performing 30 consecutive PELDs (33 levels) during a 3-month period was evaluated. Transforaminal PELDs were performed according to the standard technique. The radiation exposure of the neck, chest, arm, and both hands of the surgeons was measured. Occupational exposure guidelines of National Council on Radiation Protection & Measurements were used to calculate the allowable number of procedures per year. RESULTS: The mean operation time was 49.8 minutes, and the mean fluoroscopy time was 2.5 minutes. No significant correlations were found between operation time and fluoroscopy time. The calculated radiation doses per operated level were as follows: neck, 0.0785 mSv; chest, 0.1718 mSv; right upper arm, 0.0461 mSv; left ring finger, 0.7318 mSv; and right ring finger, 0.6694 mSv. The protective effects of a lead collar and lead apron were demonstrated by the reduction of the radiation dose by 96.9% and 94.2%, respectively. Therefore, with regard to whole-body radiation, 5379 operations can be performed per year using a lead apron, whereas only 291 operations can be performed without using a lead apron. Moreover, 1910 operations can be performed within the occupational exposure limit for the eyes (150 mSv), and 683 operations can be performed within the occupational exposure limit for the hands (500 mSv). CONCLUSION: Without radiation shielding, a surgeon performing 291 PELDs annually would be exposed to the maximum allowable radiation dose. Given the measurable lifetime radiation hazards to the surgeon, the use of adequate protective equipment is essential to reducing exposure during PELD.

Factors affecting clinical outcomes in treating patients with grade 1 degenerative spondylolisthesis using interspinous soft stabilization with a tension band system: a minimum 5-year follow-up.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: To explore the factors influencing the clinical outcomes and motion-preserving stabilization after interspinous soft stabilization (ISS) with a tension band system for grade 1 degenerative spondylolisthesis (DS). SUMMARY OF BACKGROUND DATA: Despite increasing recognition of the benefits of dynamic stabilization systems for treating lumbar degenerative disorders, the factors affecting the clinical and radiological outcomes of these systems have rarely been identified. METHODS: Sixty-five patients (mean age, 60.3 years) who underwent ISS with a tension band system between 2002 and 2004 were analyzed. The mean follow-up period was 72.5 months. The patients were divided according to the postsurgical clinical improvements into the optimal (n = 44) and suboptimal groups (n = 21), and the radiological intergroup differences were analyzed. Multiple linear regression analysis was performed to determine the impact of the radiological factors on the clinical outcomes. RESULTS: Significant intergroup differences were observed on the follow-up clinical examination. Radiologically, total lumbar lordosis (TLL) and segmental lumbar lordosis (SLL) were significantly improved only in the optimal group, resulting in significant intergroup differences in TLL (P = 0.023), SLL (P = 0.001), and the L1 tilt (P = 0.002). All these measures were closely associated with postoperative segmental lumbar lordosis, which also was the most influential radiological variable for the clinical parameters. CONCLUSION: In the patients with grade 1 DS, the back pain relief and functional improvement following ISS were affected by the improvements in the sagittal spinal alignment through the achievement of segmental lumbar lordosis. ISS can be an alternative treatment to fusion surgery for grade 1 DS in patients who do not require fixation or reduction.

Spinal meningeal melanocytoma in the S-1 nerve root sheath with paraspinal extension mimicking schwannoma.

BACKGROUND: Spinal melanocytomas are variants that can be extradural or intradural and are most often located in the intradural extramedullary compartment of the main thecal sac as in schwannomas. However, origin of this variant from the pure peripheral compartment of rootlets is exceedingly rare. CASE DESCRIPTION: The authors present a case of spinal melanocytoma with confusing pathologic and radiologic features. This patient presented clinically with severe radiating pain on the right lower extremity. Before surgery, clinical and radiologic findings were consistent with a schwannoma. However, on operation, a coal-black pigmented lesion mimicking old blood clot was found inside the right S-1 root sheath, attached to the dura. The mass was completely removed and consequently the patient's symptoms improved. CONCLUSIONS: The spinal melanocytoma should be included as a differential diagnosis before giving a presumptive diagnosis of schwannoma or hemorrhage for the patient with a space-occupying lesion at a peripheral rootlet. Intraoperative gross morphology and histopathologic findings facilitate differential diagnosis.

Dural tears in percutaneous endoscopic lumbar discectomy.

The objective of the study was to demonstrate the clinical characteristics of dural tears during percutaneous endoscopic lumbar discectomy (PELD) and to discuss how to prevent this unintended complication. The study used data from 816 consecutive patients who underwent PELD between 2003 and 2007. A total of nine patients (1.1%) experienced symptomatic dural tears. The clinical outcomes were evaluated using the visual analogue scale (VAS), the Oswestry disability index (ODI), and modified MacNab criteria. Intractable radicular pain was the most common symptom, while classical manifestations, such as CSF leakage or wound swelling, were rare. In three of the nine cases, the dural tears were detected intraoperatively, while the remaining six cases were not recognized during the procedure. Among the unrecognized patients, two patients were found with nerve root herniation causing profound neurological deficits. All patients were managed by secondary open repair surgeries. The mean follow-up period was 30.8 months. The mean VAS of radicular leg pain improved from 8.3 to 2.6, and that of back pain improved from 4.1 to 2.6. The mean ODI improved from 69.6 to 29.2%. The final outcomes were excellent in one, good in five, fair in one, and poor in two patients. As application of the endoscopic procedure has been broadened to more complex cases, the risk of dural tears may increase. Unrecognized dural tear with nerve root herniation may cause permanent neurological sequelae. Accurate information and proper technical considerations are essential to prevent this unpredictable complication.

Comparison of multilevel oblique corpectomy with and without image guided navigation for multi-segmental cervical spondylotic myelopathy.

OBJECTIVE: Multilevel Oblique Corpectomy (MOC) is an emerging technique for surgical treatment of multi-segmental cervical spondylotic myelopathy (CSM) featuring extensive ossification of the posterior longitudinal ligament (OPLL). However, the use of an oblique drilling plane is unfamiliar to most surgeons and there is no anatomical landmark present on the posterior portion of the vertebral body. To overcome these difficulties, the authors used intraoperative C-arm-based image guided navigation (IGN), and this study was conducted to evaluate the efficacy of IGN in MOC. METHODS: Following the introduction of IGN for MOC, 24 patients underwent MOC procedures at our institution. Two patients who had undergone previous cervical operations were excluded from the present study. Of the remaining 22 patients, 11 underwent MOC with IGN, and 11 underwent MOC without IGN support. The completeness of MOC (CMOC) is measured as the sum of the bilateral remaining posterior body minus the remaining approach-side anterior body in millimeters at the most compressive level. For each patient, the preoperative Japanese Orthopaedic Association Score (JOAS) and postoperative 5th day JOAS were collected as well as several other perioperative parameters. RESULTS: The mean CMOC was 0.89 mm for the IGN group and 5.9 mm for the control group. The mean change in JOAS was 5.58 for the IGN group and 3.34 for the control group at 1-year follow-up. In the control group, two patients underwent re-exploration due to remaining OPLL. Despite the intraoperative IGN set-up time, the mean operation time for the IGN group was shorter than that for the control group (248 min versus 259 min). Mean treated levels were 3.55 for the IGN group and 3.36 for the control group. CONCLUSION: Through the use of image guided navigation, it was possible to accomplish faster and more complete MOC.

Spinopelvic alignment after interspinous soft stabilization with a tension band system in grade 1 degenerative lumbar spondylolisthesis.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: The purpose of this study was to examine the changes in spinopelvic alignment after interspinous soft stabilization (ISS) with a tension band system and to identify the lumbosacral parameters related to those changes and to determine their impact on the clinical outcomes compared with posterior lumbar interbody fusion (PLIF) in patients with low-grade degenerative spondylolisthesis (DS). SUMMARY OF BACKGROUND DATA: The sacropelvic morphometric changes after fusion surgery have received much research attention. However, few reports have addressed the issue after use of dynamic or soft stabilization systems. METHODS: From April 2001 to November 2003, 45 patients presenting with grade 1 DS with stenosis underwent either ISS with a tension band system (ISS group) or PLIF with pedicle screw fixation (PLIF group). The mean follow-up period was 76.8 months. Three pelvic parameters, the sacral slope (SS), pelvic tilt (PT), and pelvic incidence, were investigated to address the sacropelvic morphometric change. Clinical outcomes were assessed using the visual analog scale score, the Oswestry Disability Index, and the patient's satisfaction index. RESULTS: Both groups showed significant improvements in all of the clinical outcomes, with no significant differences between groups. In the ISS group, the SS increased and PT decreased, whereas in the PLIF group, the SS decreased and PT increased, resulting in pelvic anteversion and retroversion, respectively, with significant intergroup differences in SS and PT (SS: P = 0.047; PT: P = 0.01). The positive association of lumbar lordosis with SS (r = 0.448) and its negative association with PT (r = -0.674) in the respective groups indicate the influence of changes in lumbar lordosis on pelvic positional changes. Significant correlations between follow-up segmental lumbar lordosis and the visual analog scale score for leg pain (r = -0.685) and Oswestry Disability Index score (r = -0.425) were found in the ISS group alone. CONCLUSION: Segmental lordotic change after ISS with a tension band system was the possible decisive factor in the development of pelvic anteversion while maintaining sagittal lumbar balance; lack of lumbar lordosis led to compensatory pelvic retroversion in the PLIF group. Considering the comparable clinical results with PLIF surgery and the achievement of physiologic sagittal spinopelvic balance, the ISS procedure can be a feasible alternative to fusion surgery in patients with grade 1 DS with stenosis.