| 1. |
- Ghandour, Salim, et al.
(författare)
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A model for the biomechanical assessment of discoplasty in a laboratory setting
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Percutaneous cement discoplasty is a spinal surgical technique which has been rarely tested outside the clinical setting. This study aimed at developing an ovine model framework to allow testing and optimization of discoplasty in a lab-controlled environment.
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| 2. |
- Ghandour, Salim, et al.
(författare)
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An ex-vivo Biomechanical Assessment of Cement Discoplasty
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spinal fusion is the golden standard for treating degenerative disc disease. However, elderly patients with underlying chronic conditions cannot undergo spinal fusion due to healing impairment, risks of infection, and/or even morbidity. Percutaneous Cement Discoplasty (PCD) is a relatively new procedure that involves injecting poly(methyl methacrylate) (PMMA) cement into the disc to reduce pain and attempt to maintain spinal curvature and height. Therefore, this minimally invasive method could be an advantageous option for patients for whom open surgery is deemed too risky [1]. While this technique has already been attempted clinically, to the authors knowledge, only one preliminary study on the biomechanics of PCD is currently available [2]. This study aims to develop a more clinically relevant and repeatable method to study PCD in a lab setting. To this end, ovine spine was tested in three different categories: healthy disc; injured disc; treated disc. A papain enzyme solution [3] was used to create the vacuum phenomena in the sheep spine to represent the injury as observed in a clinical setting. Preliminary compression testing showed promising results with a significant increase in stability of the segments after treatment. Further on, this testing method can be used to test different materials, surgical methods and biomechanical behaviour to further advance PCD.
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| 3. |
- Ghandour, Salim, et al.
(författare)
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An ex-vivo model for the biomechanical assessment of cement discoplasty
- 2022
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media S.A.. - 2296-4185. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Percutaneous Cement Discoplasty (PCD) is a surgical technique developed to relieve pain in patients with advanced degenerative disc disease characterized by a vacuum phenomenon. It has been hypothesized that injecting bone cement into the disc improves the overall stability of the spinal segment. However, there is limited knowledge on the biomechanics of the spine postoperatively and a lack of models to assess the effect of PCD ex-vivo. This study aimed to develop a biomechanical model to study PCD in a repeatable and clinically relevant manner. Eleven ovine functional spinal units were dissected and tested under compression in three conditions: healthy, injured and treated. Injury was induced by a papain buffer and the treatment was conducted using PMMA cement. Each sample was scanned with micro-computed tomography (CT) and segmented for the three conditions. Similar cement volumes (in %) were injected in the ovine samples compared to volumes measured on clinical PCD CT images. Anterior and posterior disc heights decreased on average by 22.5% and 23.9% after injury. After treatment, the anterior and posterior disc height was restored on average to 98.5% and 83.6%, respectively, of their original healthy height. Compression testing showed a similar stiffness behavior between samples in the same group. A decrease of 51.5% in segment stiffness was found after injury, as expected. The following PCD treatment was found to result in a restoration of stiffness—showing only a difference of 5% in comparison to the uninjured state. The developed ex-vivo model gave an adequate representation of the clinical vacuum phenomena in terms of volume, and a repeatable mechanical response between samples. Discoplasty treatment was found to give a restoration in stiffness after injury. The data presented confirm the effectiveness of the PCD procedure in terms of restoration of axial stiffness in the spinal segment. The model can be used in the future to test more complex loading scenarios, novel materials, and different surgical techniques.
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| 4. |
- Grzeszczak, Ana, 1995-, et al.
(författare)
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Mechanical and Structural Evaluation of Synthetic Trabecular Bone Models Printed with Stereolithography
- 2021
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Ingår i: Mechanical and Structural Evaluation of Synthetic Trabecular Bone Models Printed with Stereolithography.
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Konferensbidrag (refereegranskat)abstract
- Mechanical and Structural Evaluation of Synthetic Trabecular Bone Models Printed with StereolithographyA. Grzeszczak1, S. Lewin1, O. Eriksson2, J. Kreuger2, C. Persson11Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden2Department of Medical Cell Biology, Uppsala University, Uppsala, SwedenINTRODUCTION: Synthetic bone models are needed to train surgeons but also to test and design medical equipment. However, currently available models do not accurately mimic the complex structure of trabecular bone [1]. This study aimed to investigate the suitability of stereolithography (SLA) printing to produce synthetic trabecular bone models.METHODS: The synthetic bone models were printed by SLA using a CAD-model generated from micro-computed tomography (micro-CT) synchrotron images of human trabecular bone [2]. To adjust the printing parameters, the influence of the following variables on the mechanical properties was investigated: printer type, orientation, resolution and UV-curing time. Subsequently, the trabecular CAD-model was printed at the original scale (scale factor 1), and with several enlarging factors. Mechanical properties were evaluated by compression and screw pullout tests, and structure replicability was assessed with micro-CT.RESULTS & DISCUSSION: The elastic modulus of the control group was not statistically different from that of the other batches after the printing parameters configuration, standard parameters were therefore used. The orientation of the samples on the build platform of the printer did not seem to have an influence on the ratio Bone Volume/Total Volume for trabecular samples. For the bone models with scaling factors below 1.8, micro-CT image analysis showed major artefacts due to printing and a low accuracy in trabecular thickness distribution. Analysis of the total printed volume showed a difference to the original model higher than 50% for scale 1.5 and lower than 10% for scales 1.8 and above (Fig. 1). A refined overlap comparison with the original bone model showed that the scale 1.8 exhibited errors higher than 20%, implying printing inaccuracies of the smaller details. The pullout strength obtained for SLA-printed parts was higher than for existing synthetic models (Sawbones™) and cadaveric specimens, but within the same range as FDM-printed parts in poly(lactic acid) [2].CONCLUSIONS: Trabecular bone models with a scale factor of 1.8 or greater could be produced with acceptable accuracy, but models with smaller scale factors were not well printed. Nevertheless, for the same 3D model, a higher resolution was reached by SLA as compared to FDM [2].ACKNOWLEDGEMENTS: The authors are grateful to Adam Engberg at U-PRINT: Uppsala University’s 3D-printing facility at the Disciplinary Domain of Medicine and Pharmacy for support and advice on the printers. This research was funded by Sweden’s Innovation Agency VINNOVA, grant number 2019-00029.REFERENCES: [1] M. Poukalova et al., “Pullout strength of suture anchors: Effect of mechanical properties of trabecular bone,” J. Biomech., vol. 43, no. 6, pp. 1138–1145, Apr. 2010, doi: 10.1016/j.jbiomech.2009.12.007. [2] D. Wu, A. Spanou, A. Diez-Escudero, and C. Persson, “3D-printed PLA/HA composite structures as synthetic trabecular bone: A feasibility study using fused deposition modeling,” J. Mech. Behav. Biomed. Mater., vol. 103, p. 103608, Mar. 2020, doi: 10.1016/j.jmbbm.2019.103608.
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| 5. |
- Grzeszczak, Ana, 1995-, et al.
(författare)
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Stereolithography shows potential in additive manufacturing ofsynthetic trabecular bone structures
- 2021
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Ingår i: Stereolithography shows potential in additive manufacturing ofsynthetic trabecular bone structures.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Title and AuthorsTitle: Stereolithography shows potential in additive manufacturing of synthetic trabecular bone structures.Authors: Ana Grzeszczak, Susanne Lewin, Olle Eriksson, Johan Kreuger, Cecilia Persson IntroductionSynthetic bone models are needed to train surgeons but also to test and design medical devices such as screws for fracture fixation. However, currently available models do not accurately mimic the trabecular bone and its complex structure [1]. This study aimed to investigate if stereolithography (SLA) additive manufacturing could produce synthetic trabecular bone models with high accuracy. Experimental methods The synthetic bone models were printed by SLA (Formlabs Black resin, Form3 printer). The CAD-model had been generated from micro-computed tomography (micro-CT) synchrotron images of human trabecular bone [2]. The model was printed at the original scale (scale factor 1), and with upscaling factors up to 4.3. Structure replicability was assessed with micro-CT, and the mechanical properties were evaluated by compression and screw pullout tests. Dense cylinders of the printed material were also tested in compression for material characterization.Results and discussionThe elastic moduli obtained by compression of dense cylinders were approximately ten times lower than average values for human cortical bone. For the trabecular bone models with scaling factors below 1.8, micro-CT image analysis showed major artefacts due to printing and a low accuracy in trabecular thickness distribution. Analysis of the total printed volume showed a difference to the original model higher than 50% for scale 1.5 (Fig. 1). However, this difference was less than 10% for scales 1.8 and above, although a refined overlap comparison with the original bone model showed that the scale 1.8 exhibited errors higher than 20%, implying printing inaccuracies of the smaller details. The pullout strength of SLA-printed parts was higher than for existing synthetic models (Sawbones™) and cadaveric specimens, but within the same range as FDM-printed parts in poly(lactic acid) [2].ConclusionIn conclusion, trabecular bone models with a scale factor of 1.8 or larger could be printed with acceptable accuracy, but models with smaller scale factors were not well represented. However, for the same 3D model, a higher resolution was achieved by SLA as compared to FDM [2]. AcknowledgementsThe authors are grateful to Adam Engberg at U-PRINT: Uppsala University’s 3D-printing facility at the Disciplinary Domain of Medicine and Pharmacy for support and advice on the printers. This research was funded by Sweden’s Innovation Agency VINNOVA, grant number 2019-00029.References[1] M. Poukalova et al., “Pullout strength of suture anchors: Effect of mechanical properties of trabecular bone,” J. Biomech., vol. 43, no. 6, pp. 1138–1145, Apr. 2010, doi: 10.1016/j.jbiomech.2009.12.007.[2] D. Wu, A. Spanou, A. Diez-Escudero, and C. Persson, “3D-printed PLA/HA composite structures as synthetic trabecular bone: A feasibility study using fused deposition modeling,” J. Mech. Behav. Biomed. Mater., vol. 103, p. 103608, Mar. 2020, doi: 10.1016/j.jmbbm.2019.103608.
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| 6. |
- Grzeszczak, Ana, et al.
(författare)
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The Potential of Stereolithography for 3D Printing of Synthetic Trabecular Bone Structures
- 2021
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Ingår i: Materials. - : MDPI. - 1996-1944 .- 1996-1944. ; 14:13
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic bone models are used to train surgeons as well as to test new medical devices. However, currently available models do not accurately mimic the complex structure of trabecular bone, which can provide erroneous results. This study aimed to investigate the suitability of stereolithography (SLA) to produce synthetic trabecular bone. Samples were printed based on synchrotron micro-computed tomography (micro-CT) images of human bone, with scaling factors from 1 to 4.3. Structure replicability was assessed with micro-CT, and mechanical properties were evaluated by compression and screw pull-out tests. The overall geometry was well-replicated at scale 1.8, with a volume difference to the original model of <10%. However, scaling factors below 1.8 gave major print artefacts, and a low accuracy in trabecular thickness distribution. A comparison of the model-print overlap showed printing inaccuracies of similar to 20% for the 1.8 scale, visible as a loss of smaller details. SLA-printed parts exhibited a higher pull-out strength compared to existing synthetic models (Sawbones (TM)), and a lower strength compared to cadaveric specimens and fused deposition modelling (FDM)-printed parts in poly (lactic acid). In conclusion, for the same 3D model, SLA enabled higher resolution and printing of smaller scales compared to results reported by FDM.
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| 7. |
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| 8. |
- Johanen, Astera, et al.
(författare)
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Trabecular bone patterns as a fracture risk predictor: a systematic review
- 2021
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Ingår i: Acta odontologica Scandinavica. - : Informa UK Limited. - 1502-3850 .- 0001-6357. ; 79:7, s. 482-491
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this systematic review was to evaluate the assessment of trabecular bone patterns in dental radiographs, for fracture risk prediction, compared with the current diagnostic methods.The PRISMA guidelines were followed. According to predefined inclusion criteria (PICO), literature searches were focussed on published studies with analyses of trabecular bone patterns on intraoral and/or in panoramic radiographs, compared with Dual X-ray Absorptiometry (DXA) and/or Fracture Risk Assessment Tool (FRAX), with the outcomes; fracture and/or sensitivity and specificity for osteoporosis prediction. The included studies were quality-assessed using the QUADAS-2 tool and the certainties of evidence was assessed using the GRADE approach.The literature searches identified 2913 articles, whereas three were found to meet the inclusion criteria. Two longitudinal cohort studies evaluated the use of trabecular bone patterns to predict bone fractures. In one of the studies, the relative risk of fracture was significantly higher for women with sparse bone pattern, identified by visual assessment of dental radiographs, and in the other study by digital software assessment. Visual assessment in the second study did not show significant results. The cross-sectional study of digital analyses of trabecular bone patterns in relation to osteoporosis reported a sensitivity of 0.70 and a specificity of 0.69.Based on low certainty of evidence, trabecular bone evaluation on dental radiographs may predict fractures in adults without a prior diagnosis of osteoporosis, and based on very low certainty of evidence, it is uncertain whether digital image analyses of trabecular bone can predict osteoporosis.
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| 9. |
- Lewin, Susanne, et al.
(författare)
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Additively manufactured mesh-type titanium structures for cranial implants : E-PBF vs. L-PBF
- 2021
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- A patient-specific titanium-reinforced calcium phosphate (CaP–Ti) cranial implant has recently shown promising clinical results. Currently, its mesh-type titanium structure is additively manufactured using laser beam powder bed fusion (L-PBF). Nevertheless, an electron-beam (E-PBF) process could potentially be more time efficient. This study aimed to compare the geometrical accuracy and mechanical response of thin titanium structures manufactured by L-PBF (HIPed) and E-PBF (as-printed). Tensile test (ø = 1.2 mm) and implant specimens were manufactured. Measurements by μCT revealed a deviation in cross-sectional area as compared to the designed geometry: 13–35% for E-PBF and below 2% for L-PBF. A superior mechanical strength was obtained for the L-PBF specimens, both in the tensile test and the implant compression tests. The global peak load in the implant test was 457 ± 9 N and 846 ± 40 N for E-PBF and L-PBF, respectively. Numerical simulations demonstrated that geometrical deviation was the main factor in implant performance and enabled quantification of this effect: 34–39% reduction in initial peak force based on geometry, and only 11–16% reduction based on the material input. In summary, the study reveals an uncertainty in accuracy when structures of sizes relevant to mesh-type cranial implants are printed by the E-PBF method.
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