Byeongwoo Kim

Solidification sequence of the icosahedral quasicrystal forming Al–Cu–Fe alloys

Abstract The solidification sequence of the icosahedral quasicrystal forming Al–Cu–Fe alloys was investigated as functions of cooling rate during solidification, compositional variation, and additional Si amount. Annealing treatment was also carried out to obtain the single icosahedral quasicrystalline phase. Two different formation mechanisms of the icosahedral quasicrystalline phase can be suggested as a function of cooling rate. For a moderate cooling rate regime, the icosahedral phase is formed by a peritectic reaction, which is consistent with the previous reports. For a high cooling rate regime, where large undercooling of the liquid is obtainable, the i-phase (icosahedral phase) is formed directly from the undercooled melt, without the formation of the primary λ or β phases. The τ phase was formed at the inter-dendritic region of the i-phase grains from the remaining liquid at the final stage of solidification. As the Si element was added up to 5xa0at.%, the relative volume fraction of the i-phase gradually decreased in both as-cast and heat treated Al–Cu–Fe alloys. For an as-cast Al 50 Cu 20 Fe 15 Si 15 alloy, however, the major phase was identified as an i-phase related 1/1 simple cubic approximant.

Surgical outcome and prognostic factors of anterior decompression and fusion for cervical compressive myelopathy due to ossification of the posterior longitudinal ligament

BACKGROUND CONTEXTnAnterior decompression and fusion (ADF) for ossification of the posterior longitudinal ligament (OPLL) is technically demanding and associated with complications. Although various factors affecting clinical outcome have been investigated in posterior decompression, prognostic factors of ADF remain unclear.nnnPURPOSEnThe purpose of the study was to identify surgical outcome and prognostic factors of ADF for cervical myelopathy due to OPLL.nnnSTUDY DESIGNnThis was a retrospective case study.nnnPATIENT SAMPLEnBetween 2005 and 2012, 913 patients underwent decompression surgery for cervical OPLL at our institution. Among them, 131 who underwent ADF and 221 who underwent laminoplasty were enrolled. Inclusion criteria were (1) diagnosis of OPLL; (2) cervical compressive myelopathy; and (3) no trauma, infection, tumor, or previous surgery. We excluded 60 patients with ADF and 157 patients with laminoplasty owing to inadequate follow-up or absence of preoperative myelopathy. Finally, 71 patients with ADF and 64 patients with laminoplasty were enrolled in this study (mean follow-up, 48 vs 41 months).nnnOUTCOME MEASURESnNeurologic assessment was conducted using the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy. Rate of neurologic improvement was calculated by comparing preoperative and postoperative JOA scores.nnnMETHODSnWe investigated the effects of such variables as age, gender, body mass index (BMI), presence of diabetes mellitus (DM), smoking history, type of OPLL, shape of the ossified lesion, occupying ratio of OPLL, presence of intramedullary increased signal intensity (ISI) on magnetic resonance imaging (MRI), and sagittal alignment of the cervical spine on surgical outcome. Severity of ISI was classified into three groups based on T2-weighted sagittal MRI as follows: Grade 0, none; Grade 1, ISI limited to one disc level; or Grade 2, ISI beyond one disc level. This work was supported by the 2013 Korea Health Technology R&D Project of the Ministry of Health and Welfare of the Republic of Korea (A120254).nnnRESULTSnIn patients with an occupying ratio ≥60% or with presence of ISI on MRI, ADF yielded better surgical outcome than laminoplasty. A higher ISI grade (B=-28.5, p=.000) and a higher occupying ratio (B=0.88, p=.04) were significantly associated with a lower recovery rate (R=0.56, p=.006). Older age also was associated with a lower recovery rate. Gender, BMI, presence of DM, smoking history, type of OPLL, shape of the ossified lesion, and cervical alignment were not associated with recovery rate.nnnCONCLUSIONnAnterior decompression and fusion has favorable outcome in patients with an occupying ratio ≥60% or with presence of ISI on MRI. Presence of higher ISI grade, higher occupying ratio, and older age were associated with a poor long-term surgical prognosis. Therefore, evaluating ISI and occupying ratio on preoperative MRI is important for selecting the appropriate surgical approach and for predicting clinical outcome after surgery for cervical compressive myelopathy due to OPLL.

Relationship between T1 slope and loss of lordosis after laminoplasty in patients with cervical ossification of the posterior longitudinal ligament.

BACKGROUND CONTEXTnLaminoplasty is a major surgical method used to treat patients with cervical ossification of the posterior longitudinal ligament (OPLL). Sometimes, patients with cervical OPLL demonstrate postoperative kyphosis despite sufficient preoperative lordosis. Recently, the impact of T1 slope has emerged as a predictor of kyphotic alignment change after laminoplasty. However, the relationship between T1 slope and postoperative cervical alignment change is not yet fully established.nnnPURPOSEnThe goals of the present study were to investigate the relationship between T1 slope and loss of cervical lordosis (LCL), and to identify the role of T1 slope as a predictor of postoperative kyphosis after laminoplasty in patients with OPLL.nnnSTUDY DESIGNnThis is a retrospective case study.nnnPATIENT SAMPLEnBetween January 2011 and January 2012, 64 consecutive patients who underwent cervical laminoplasty for OPLL were enrolled (male:female ratio=47:17; mean age=55.9 years). Cervical spine lateral radiographs in neutral, flexion, and extension were taken before surgery and at 2-year follow-up.nnnOUTCOME MEASURESnThe C2-C7 Cobb angle, cervical range of motion (ROM), T1 slope, neck tilt, and C2-C7 sagittal vertical axis (SVA) were measured from lateral radiographs of the cervical spine preoperatively and postoperatively at 2-year follow-up.nnnMETHODSnPatients were divided into two groups according to preoperative T1 slope, and the postoperative cervical alignment change was compared between the groups. Postoperative kyphosis and LCL incidence were also evaluated at 2-year follow-up. The relationships between postoperative cervical alignment change and preoperative variables, including age, T1 slope, cervical ROM, C2-C7 SVA, and T1 slope minus C2-C7 Cobb angle (T1S-CL), were investigated.nnnRESULTSnPatients were divided into two groups above and below median preoperative T1 slope (23.2°). There were no differences in age, sex, type of OPLL, or operation level between the two groups. Patients with higher preoperative T1 slope demonstrated significantly more lordotic preoperative cervical alignment (p=.001). Patients with higher preoperative T1 slope were more likely to exhibit postoperative LCL (p=.03), and when it occurred the degree of LCL was greater (p=.06). In multiple linear regression analysis, higher T1 slope (B=0.414, p=.04) and lower T1S-CL (B=-0.412, p=.03) were significantly associated with more postoperative LCL. In spite of these results, postoperative kyphosis did not occur more frequently in patients with higher T1 slope (p=.64).nnnCONCLUSIONSnPatients with higher T1 slope had more lordotic curvature before surgery and demonstrated more LCL at 2-year follow-up. Cervical alignment was compromised after laminoplasty, and the degree of LCL was correlated with preoperative T1 slope. After laminoplasty for cervical OPLL, patients with higher T1 slope tended to exhibit a greater LCL yet did not drift into frank postoperative kyphosis.

Effect of Si addition on the formability of the icosahedral quasicrystalline phase in an Al65Cu20Fe15 alloy

Abstract The effect of Si addition on the icosahedral forming Al 65 Cu 20 Fe 15 alloy was investigated. Conventional casting and melt spinning were employed with the addition of Si element. As Si was added up to 5xa0at.% replacing the Al atoms, the volume fraction of the i-phase gradually decreased. However, with increasing Si content further up to 15xa0at.%, an 1/1 cubic approximant phase formed instead of the i-phase. After heat treatment at 750°C for 3xa0h, the volume fraction of the β-phase increased in an Al 64 Cu 20 Fe 15 Si 1 alloy, while the volume fraction of the 1/1 approximant phase increased in an Al 50 Cu 20 Fe 15 Si 15 alloy. The Al 50 Cu 20 Fe 15 Si 15 alloy showed a relatively high hardness and fracture toughness compared to the other Si containing Al–Cu–Fe alloys.

Feasibility Study of Utilization of action camera, GoPro Hero 4, Google Glass and Panasonic HX-A100 in Spine Surgery.

Study Design. Study for feasibility of commercially available action cameras in recording video of spine. Objective. Recent innovation of the wearable action camera with high-definition video recording enables surgeons to use camera in the operation at ease without high costs. The purpose of this study is to compare the feasibility, safety, and efficacy of commercially available action cameras in recording video of spine surgery. Summary of Background Data. There are early reports of medical professionals using Google Glass throughout the hospital, Panasonic HX-A100 action camera, and GoPro. This study is the first report for spine surgery. Methods. Three commercially available cameras were tested: GoPro Hero 4 Silver, Google Glass, and Panasonic HX-A100 action camera. Typical spine surgery was selected for video recording; posterior lumbar laminectomy and fusion. Three cameras were used by one surgeon and video was recorded throughout the operation. The comparison was made on the perspective of human factor, specification, and video quality. Results. The most convenient and lightweight device for wearing and holding throughout the long operation time was Google Glass. The image quality; all devices except Google Glass supported HD format and GoPro has unique 2.7K or 4K resolution. Quality of video resolution was best in GoPro. Field of view, GoPro can adjust point of interest, field of view according to the surgery. Narrow FOV option was the best for recording in GoPro to share the video clip. Google Glass has potentials by using application programs. Connectivity such as Wi-Fi and Bluetooth enables video streaming for audience, but only Google Glass has two-way communication feature in device. Conclusion. Action cameras have the potential to improve patient safety, operator comfort, and procedure efficiency in the field of spinal surgery and broadcasting a surgery with development of the device and applied program in the future. Level of Evidence: N/A

Role of Ethnicity in Alignment Compensation: Propensity Matched Analysis of Differential Compensatory Mechanism Recruitment Patterns for Sagittal Malalignment in 288 Asd Patients From Japan, Korea, and United States

Study Design. Retrospective review of adult spinal deformity patients in a multiethnic database. Objective. To investigate the role of ethnicity on recruitment of compensatory mechanisms for sagittal spinal deformity. Summary of Background Data. While the impacts of age, sex, and pelvic morphology on the ability to compensate for sagittal malalignment have been investigated, the role of ethnicity in compensatory mechanism recruitment is poorly understood. Methods. Patients from USA (85% Caucasian) >25u200ay/o were propensity matched by age, sex, and pelvic incidence with patients from Korea and Japan. Only primary patients or those with existing fusion below T12 were retained for analysis. Groups were subclassified by deformity severity (aligned: sagittal vertical axis (SVA)u200a<50u200amm; moderate malalignment: SVA 50–100u200amm; severe malalignment: SVA >100u200amm). Radiographic measurements including pelvic retroversion, thoracic kyphosis, loss of lumbar lordosis (PI minus LL), cervical lordosis, and cervical SVA were compared between the groups. Results. There were 288 patients (96 each in USA, KOR, JPN), with similar age (64–67 yr) and PI (49–53°). USA had smaller pelvic incidence minus lumbar lordosis in every alignment group (Pu200a<0.05). In moderate malalignment, JPN had more pelvic retroversion than USA (30° vs. 20°), and KOR had more thoracic hypokyphosis than USA (15 vs. 31°). In severe malalignment, JPN had more pelvic retroversion than USA (39° vs. 27°), and KOR had more thoracic hypokyphosis than USA (15° vs. 31°). KOR had smaller cSVA than USA in both aligned (11 vs. 27u200amm) and moderate (19 vs. 31u200amm) malalignment. In severe malalignment, KOR had less cervical lordosis (13° KOR vs. 15° USA vs. 27° JPN). All differences with Pu200a<0.05. Conclusion. Compensation for sagittal is ethnicity dependent. Korean patients favor thoracic compensation via hypokyphosis, and Japanese patients favor pelvic compensation via retroversion. Patient ethnicity should be considered when evaluating the sagittal plane and surgical correction strategies. Level of Evidence: 3

Characteristics of Cervical Spine Trauma in Patients with Ankylosing Spondylitis and Ossification of the Posterior Longitudinal Ligament

OBJECTIVEnTo compare the clinical characteristics of cervical spine trauma in patients with ankylosing spondylitis (AS) and cervical ossification of the posterior longitudinal ligament (OPLL) with those of a control group.nnnMETHODSnA total of 124 patients with cervical spine trauma from January 2004 to December 2013 were reviewed. Fourteen patients were diagnosed with AS and 25 patients were diagnosed with OPLL; 85 patients were controls. C-spine plain radiography, computed tomography, and magnetic resonance imaging were obtained for evaluation of cervical spine trauma. The American Spinal Injury Association impairment scale and Subaxial Cervical Spine Injury Classification were used to evaluate the neurologic status of patients and the fracture mechanism.nnnRESULTSnPatients with AS or OPLL had more spinal injuries associated with minor trauma than did the control group. All patients with AS had spinal fracture injuries after cervical spine trauma, but patients with OPLL mostly had spinal cord injuries without bony fractures. After cervical spine trauma, delayed diagnosis occurred in 3 patients with AS (21.4%) and 4 patients with OPLL (15.6%). Improvement from neurologic deficit after treatment showed better outcomes in patients with AS and OPLL than in controls (Pxa0= 0.106).nnnCONCLUSIONSnPatients with AS or OPLL who had cervical spine trauma showed different characteristics and outcomes than control patients. Proper surgical treatment led to better outcomes in both patients with AS and patients with OPLL than in control patients. Moreover, it is important to thoroughly examine patients with AS or OPLL after cervical trauma so as not to delay diagnosis.

Findings from frozen sections of spinal subependymomas: Is it possible to differentiate this diagnosis from other common spinal tumors?

Subependymomas are slow-growing, benign neoplasms that are rarely found in the spinal cord. Because of the differences in the treatment plans, it might be very helpful for neurosurgeons to intraoperatively establish a diagnosis of spinal subependymoma, differentiated from other spinal intramedullary tumors. In this study, we analyzed frozen sections of spinal subependymomas to identify potential histological clues of spinal subependymomas to differentiate them from tumors that mimic spinal subependymoma. We reviewed the frozen sections and the corresponding permanent slides for 7 cases of spinal subependymoma. The spinal subependymomas showed several characteristic patterns, including, most importantly, an eccentric or both central and eccentric location in the axial plane. Histologically, they showed a (1) well-demarcated and multinodular mass with (2) low or moderate cellularity, (3) a microlobular pattern, and (4) small clusters of neoplastic cells. These features appear to be very specific to spinal subependymomas and could help differentiate them from ependymomas or astrocytomas. Although we might not be able to provide an exact diagnosis of all spinal subependymomas using these histological features, we hope that they help neuropathologists and neurosurgeons to adequately diagnose and treat spinal subependymomas.