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Khuyagbaatar, Batbayar,Kim, Kyungsoo,Park, Won Man,Kim, Yoon Hyuk Elsevier 2017 Journal of biomechanics Vol.57 No.-
<P><B>Abstract</B></P> <P>Post-operative C5palsies are among the most common complications seen after cervical surgery for ossification of the posterior longitudinal ligament (OPLL). Although C5 palsy is a well-known complication of cervical spine surgery, its pathogenesis is poorly understood and depends on many other factors. In this study, a finite element model of the cervical spine and spinal cord-nerve roots complex structures was developed. The changes in stress in the cord and nerve roots, posterior shift of the spinal cord, and displacement and elongation of the nerve roots after laminectomy for cervical OPLL were analyzed for three different cervical sagittal alignments (lordosis, straight, and kyphosis). The results suggest that high stress concentrated on the nerve roots after laminectomy could be the main cause of C5 palsy because ossification of ligaments increases spinal cord shifting and root displacement. The type of sagittal alignment had no influence on changes in cord stress after laminectomy, although cases of kyphosis with a high degree of occupying ratio resulted in greater increases in nerve root stress after laminectomy. Therefore, kyphosis with a high OPLL occupying ratio could be a risk factor for poor surgical outcomes or post-operative complications and should be carefully considered for surgical treatment.</P>
Khuyagbaatar, Batbayar,Kim, Kyungsoo,Park, Won Man,Kim, Yoon Hyuk Professional Engineering Publishing Ltd. 2016 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>Ossification of the posterior longitudinal ligament is a common cause of the cervical myelopathy due to compression of the spinal cord. Patients with ossification of the posterior longitudinal ligament usually require the decompression surgery, and there is a need to better understand the optimal surgical extent with which sufficient decompression without excessive posterior shifting can be achieved. However, few quantitative studies have clarified this optimal extent for decompression of cervical ossification of the posterior longitudinal ligament. We used finite element modeling of the cervical spine and spinal cord to investigate the effect of posterior decompression extent for continuous-type cervical ossification of the posterior longitudinal ligament on changes in stress, strain, and posterior shifting that occur with three different surgical methods (laminectomy, laminoplasty, and hemilaminectomy). As posterior decompression extended, stress and strain in the spinal cord decreased and posterior shifting of the cord increased. The location of the decompression extent also influenced shifting. Laminectomy and laminoplasty were very similar in terms of decompression results, and both were superior to hemilaminectomy in all parameters tested. Decompression to the extents of C3-C6 and C3-C7 of laminectomy and laminoplasty could be considered sufficient with respect to decompression itself. Our findings provide fundamental information regarding the treatment of cervical ossification of the posterior longitudinal ligament and can be applied to patient-specific surgical planning.</P>
Biomechanical Behaviors in Three Types of Spinal Cord Injury Mechanisms
Khuyagbaatar, Batbayar,Kim, Kyungsoo,Park, Won Man,Kim, Yoon Hyuk AMERICAN SOCIETY MECHANICAL ENGINEERS 2016 Journal of biomechanical engineering Vol.138 No.8
<P>Clinically, spinal cord injuries (SCIs) are radiographically evaluated and diagnosed from plain radiographs, computed tomography (CT), and magnetic resonance imaging. However, it is difficult to conclude that radiographic evaluation of SCI can directly explain the fundamental mechanism of spinal cord damage. The von-Mises stress and maximum principal strain are directly associated with neurological damage in the spinal cord from a biomechanical viewpoint. In this study, the von-Mises stress and maximum principal strain in the spinal cord as well as the cord cross-sectional area (CSA) were analyzed under various magnitudes for contusion, dislocation, and distraction SCI mechanisms, using a finite-element (FE) model of the cervical spine with spinal cord including white matter, gray matter, dura mater with nerve roots, and cerebrospinal fluid (CSF). A regression analysis was performed to find correlation between peak von-Mises stress/peak maximum principal strain at the cross section of the highest reduction in CSA and corresponding reduction in CSA of the cord. Dislocation and contusion showed greater peak stress and strain values in the cord than distraction. The substantial increases in von-Mises stress as well as CSA reduction similar to or more than 30% were produced at a 60% contusion and a 60% dislocation, while the maximum principal strain was gradually increased as injury severity elevated. In addition, the CSA reduction had a strong correlation with peak von-Mises stress/peak maximum principal strain for the three injury mechanisms, which might be fundamental information in elucidating the relationship between radiographic and mechanical parameters related to SCI.</P>
A Dependency Graph-Based Keyphrase Extraction Method Using Anti-patterns
( Khuyagbaatar Batsuren ),( Erdenebileg Batbaatar ),( Tsendsuren Munkhdalai ),( Meijing Li ),( Oyun-erdene Namsrai ),( Keun Ho Ryu ) 한국정보처리학회 2018 Journal of information processing systems Vol.14 No.5
Keyphrase extraction is one of fundamental natural language processing (NLP) tools to improve many textmining applications such as document summarization and clustering. In this paper, we propose to use two novel techniques on the top of the state-of-the-art keyphrase extraction methods. First is the anti-patterns that aim to recognize non-keyphrase candidates. The state-of-the-art methods often used the rich feature set to identify keyphrases while those rich feature set cover only some of all keyphrases because keyphrases share very few similar patterns and stylistic features while non-keyphrase candidates often share many similar patterns and stylistic features. Second one is to use the dependency graph instead of the word co-occurrence graph that could not connect two words that are syntactically related and placed far from each other in a sentence while the dependency graph can do so. In experiments, we have compared the performances with different settings of the graphs (co-occurrence and dependency), and with the existing method results. Finally, we discovered that the combination method of dependency graph and anti-patterns outperform the state-of-the-art performances.
Batbayar Khuyagbaatar,이상진,천마로,Temuujin Batbayar,Danaa Ganbat,김윤혁 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5
Instability of the distal radioulnar joint (DRUJ) is a common clinical problem due to a fall on the outstretched hand or unexpected forcible wrist rotations. Although there are many surgical treatments available for DRUJ instabilities, many of injuries can be managed conservatively, such as the wrist-wearing DRUJ stabilizer to provide the stability of the joint. However, there is a lack of research regarding use of the stabilizer on wrist joint biomechanics. In this study, a finite element (FE) model of the forearm was developed to investigate the effects of the stabilizer on DRUJ stability. The effect of the stabilizer on joint stability was quantified by laxity and rotation tests. Our results showed that use of a stabilizer may help to provide stability for the joint by reducing dorsal-volar translation of the radius and ulna, which might be helpful to prevent reoccurrence of a wrist joint injury related with instability.
Recent Developments in Finite Element Analysis of the Lumbar Spine
Batbayar Khuyagbaatar,Kyungsoo Kim,Yoon Hyuk Kim 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.2
Finite element (FE) modeling is widely used to study the biomechanical effect of material properties, surgical procedures, and loading and boundary conditions on the lumbar spine. Since several studies have presented FE analyses of the lumbar spine in relation to spine biomechanics, soft tissue modeling, intervertebral discs, facet joints, load-sharing behaviors of lumbar motion segments, and FE modeling methods, detailed analyses of disc degeneration or muscle force prediction have been little considered. This study focused on recent developments in FE modeling of the lumbar spine, including disc degeneration, muscle force prediction, and clinical applications. Modeling and analysis from the bone to soft tissue and muscle forces, as well as the validation and application of these models were provided and discussed with material properties, element types, loading and boundaries, geometric parameters, and muscle force modeling. Experimental data was summarized for validation of the FE model. Application studies were briefly reviewed, in which the majority of FE models focused on spinal degeneration diseases and surgical instrumentation techniques. Although muscle force prediction and optimization are challenging with FE modeling due to their complexity and redundancy, several studies have predicted muscle activation and spinal forces for injury prevention assessments and treatment strategies. The level of modeling prediction and representation can be improved with subject-specific data, and integration of FE and musculoskeletal models could generate a comprehensive analysis of the lumbar spine in clinical applications.