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8th Dutch Bio-Medical Engineering Conference
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12:30   Spine
Chair: Chris Baten
12:30
15 mins
Proton density fat fraction of the spinal column: An MRI cadaver study
Merle S. Losch, Akash Swamy, Adrian Elmi-Terander, Erik Edström, Benno H. W. Hendriks, Jenny Dankelman
Abstract: Significance: The increased popularity of minimally invasive spinal surgery calls for a revision of guidance techniques to prevent injuries of nearby neural and vascular structures. Lipid content has previously been proposed as a distinguishing criterion for different bone tissues to provide guidance along the interface of cancellous and cortical bone. Aim: This study aims to investigate how fat is distributed throughout the spinal column to confirm or refute the suitability of lipid content for guidance purposes. Approach: Proton density fat fraction (PDFF) was assessed over all vertebral levels for six human cadavers between 53 and 92 years of age, based on fat and water MR images. According to their distance to the vertebra contour, the data points were grouped in five regions of interest (ROIs): cortical bone (-1 mm to 0 mm), pre-cortical zone (PCZ) 1 to 3 (0 mm to 1 mm; 1 mm to 2 mm; 2 mm to 3 mm), and cancellous bone (≥ 3 mm). Results: For PCZ1 vs. PCZ2, a significant difference in mean PDFF of between -7.59 pp and -4.39 pp on average was found. For cortical bone vs. PCZ1, a significant difference in mean PDFF of between -27.09 pp and -18.96 pp on average was found. Conclusion: A relationship between distance from the cortical bone boundary and lipid content could be established, paving the way for guidance techniques based on fat fraction detection for spinal surgery.
12:45
15 mins
Intervertebral motion analysis during flexion and extension cinematographic recordings in the cervical spine
Valérie Schuermans, Inge Caelers, Toon Boselie, Anouk Smeets, Henk Van Santbrink
Abstract: Objective: To investigate the normal sequence of segmental contributions in the lower cervical spine during maximum flexion and extension in asymptomatic individuals between 55 and 70 years old. General Significance: Physiological motion in the spine is a subject of interest as abnormal motion is believed to be a contributing factor in the development of degenerative spinal pathologies. A commonly used method to define motion of the spine is segmental range of motion (sROM), although studies show a high intra- and interindividual variability. Our research group previously developed a new method to determine the sequence of segmental contributions of movement of the cervical spine in young individuals. A program which uses image recognition algorithms to track vertebrae through the series of frames in a fluoroscopic recording of flexion and extension was developed. The program follows structures within user- defined template areas throughout all frames, using a best-fit principle to match normalized gradient field images. A consistent pattern in the lower cervical spine of young asymptomatic individuals during the second half of extension (C4-C5 followed by C5-C6, and finally C6-C7) [1] was defined as ‘normal’ motion . Moreover, this method can reliably differentiate between normal and abnormal motion of the cervical spine on an individual level. Research Method: This ‘Cervical Motion’ study analyses the physiological motion of the cervical spine in asymptomatic individuals of 55 to 70 years, aiming to determine whether the previously defined normal motion in young individuals is also present in this population. Cinematographic flexion and extension recordings were made at two time points with a minimum two-week interval in between. Results: Currently, cinematographic recordings from the Cervical Motion study are analysed. Furthermore, another study has started that evaluates motion patterns in individuals several years after anterior cervical decompression surgery for radiculopathy. In this study, motion in patients with fusion surgery will be compared to those with arthroplasty. Conclusion: The analysis of the sequence of segmental contributions in the spine has proved to be a reliable method to distinguish normal from abnormal movement in the lower cervical spine in young individuals. This study aims to prove that this normal movement is also present in an older population.
13:00
15 mins
Intervertebral motion analysis during flexion and extension cinematographic recordings in the lumbar spine
Inge Caelers, Valerie Schuermans, Toon Boselie, Anouk Smeets, Henk Van Santbrink
Abstract: Objective: Defining sequence of segmental contribution in the lumbar spine (L1-S1) during maximum flexion and extension in asymptomatic individuals. General Significance: Physiological motion of the lumbar spine is a subject of interest, as abnormal motion is believed to be related to lumbar pathology and complaints. However, an adequate definition of physiological motion of the lumbar spine is still lacking. A commonly used method to define motion is segmental range of motion (sROM) or sequence of segmental initiation in sagittal rotation, although this method shows high intra-, and inter-individual variability. Our research group investigated sequence of segmental contribution, instead of sROM and sequence of segmental initiation, during flexion and extension in the cervical spine. A consistent pattern was confirmed in young asymptomatic individuals and defined as ‘normal’ motion1. Moreover, this method can reliably differentiate between normal and abnormal motion of the cervical spine on an individual level. A custom developed program, which uses image recognition algorithms to track vertebrae through the series of frames in a cinematographic recording, was used. The program follows structures within user-defined template areas throughout all frames, using a best-fit principle to match normalized gradient field images. Research Method: Cinematographic recordings were performed of L1 to S1 in eleven asymptomatic, young males (18-25 years) without a history of spine problems. Cinematographic flexion and extension recordings were made at two time points with a minimum two-week interval in between. Preliminary Results: Comparable with the cervical motion study, sequences in extension cinematographic recordings were more consistent than in flexion cinematographic recordings. These were therefore used for analysis to define ‘normal’ motion. A consistent sequence of segmental contribution was identified in the last phase of the extension. It consisted of a peak in rotation L3-L4, followed by a peak in L2-L3, and finally in L1-L2. Furthermore, intraclass correlation coefficient appeared to be higher than 0.60, which indicates adequate reliability. Conclusion: Defining physiological motion patterns in the lumbar spine might provide new insights in spinal pathologies by distinguishing between normal and abnormal motion. In the future, differences in biomechanics can potentially be linked to physical complaints like low back pain. 1. Boselie TFM, van Santbrink H, de Bie RA, van Mameren H. Pilot Study of Sequence of Segmental Contributions in the Lower Cervical Spine During Active Extension and Flexion: Healthy Controls Versus Cervical Degenerative Disc Disease Patients. Spine (Phila Pa 1976). 2017;42(11):E642-E647. doi:10.1097/BRS.0000000000001914
13:15
15 mins
Yeditepe spine mesh: Modeling and validation of a parametric finite element model of the lumbar spine
Oğulcan Güldeniz, Fethi Okyar
Abstract: ABSTRACT Finite element analysis is a powerful tool that is often used to study the biomechanical response of the spine. Anatomical meshes that are used for such analysis are often fixed, hence preventing the tuning of morphometrical parameters [1]. Parametric CAD models allow the independent tuning of the morphometric parameters based on patient data. This could accelerate the patient-specific finite element model development process significantly [2]. The primary objective of this study was to develop a new parametric CAD model and validate its finite element model. Two finite element models of the L4-L5 spinal level were developed from the same patient’s CT scan data. The first was developed using well-known segmentation methods, whereas the second was developed from the new parametric CAD model. The CAD model was constructed using morphometric parameter measurements from the patient’s CT scan [3]. Both models were subjected to the same loading and boundary conditions. Mesh verification was performed by an extensive convergence study. Results of both models were compared with each other and with the literature for validation. Convergence was achieved for both models after a couple of refinements. The segmented finite element model was observed to be in good agreement with the literature. The parametric finite element model results were also observed to be in good agreement with the segmented finite element model and with the literature except under extension. The non-symmetric nature of the spine was observed to be heavily influencing the model predictions. The main cause of failure to validate the parametric finite element model in extension is thought to be due to misrepresentation of facet joint geometry in the CAD model. Future study on the facet joint geometry and the non-symmetric nature of the vertebrae geometry is proposed. REFERENCE 1. Dreischarf M, et al. Comparison of eight published static finite element models of the intact lumbar spine: Predictive power of models improves when combined together. J Biomech 2014; 47: 1757–1766. 2. Pellegrino A, Solitro GF, Naddeo A. Spinal FEM analyses based on parametric CAD model of vertebra. Computer Methods in Biomechanics and Biomedical Engineering Conference, Porto (Portogallo) 2008. 3. Okyar F, et al. A holistic parametric design attempt towards geometric modeling of the lumbar spine. Comput Methods Biomech Biomed Eng Imaging Vis 2020; 8: 65-75.


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