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- Lewin, Susanne
(författare)
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Functional Aspects of Cranial Implants : Mechanical and Regenerative Properties
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In several neurosurgical procedures, the skull must be temporarily opened. The resulting bone defect can subsequently be reconstructed with a cranial implant. However, the complication rate of this surgical procedure is high (~20%). The most common complication for cranial implants is infection. Currently, the most frequently used implant materials are titanium alloys, PMMA or PEEK. An improved clinical outcome – in terms of increased bone regeneration, vascularization and soft tissue compatibility – could possibly be obtained through the use of bioactive and osteoconductive materials such as calcium phosphates (CaP).This thesis focuses on CaP–titanium composite (CaP–Ti) implants. This recently developed implant type is increasingly used with a promising outcome. However, a thorough understanding of its functional properties is lacking, something that is of high importance for their clinical use, but also for future biomaterial development. The overall aim of this thesis is to increase the knowledge of the in vivo functional aspects of CaP–Ti composite implants, with a specific focus on the mechanical and regenerative properties.The mechanical properties of the implant were investigated experimentally and numerically at quasi-static and impact loading rates. An important finding was that the titanium structure makes the CaP–Ti implant capable of cerebral protection in impact situations comparable to the one that was tested. Moreover, the mechanical response of the CaP–Ti implants could be predicted by the developed numerical models at both quasi-static and impact loading rates. The developed numerical framework makes an important contribution to future evaluations of patient-specific CaP–Ti cranial implant designs in various loading scenarios. A comparison of two additive manufacturing (3D-printing) processes demonstrated that lower geometrical accuracy and higher surface roughness made electron beam produced implants inferior in terms of mechanical strength, as compared to laser melted implants.In order to assess the regenerative properties, the volumetric balance of the implant was investigated by CT in ten patients. After one year, the total volume of the implant had decreased – mainly at the outside of the implants in the direction of the scalp. However, all patients had a volumetric increase at the interface between the implant and the bone defect. In a histological analysis of a retrieval specimen from one of the patients, the volumetric increase could be confirmed as bone regeneration, and the decrease as CaP degradation. Remodeling of the CaP into bone was also observed, but was not detected in the clinical CT. In retrieval specimens from an animal study, it was found that correlation of some µCT cross-sections to histology can result in improved and more robust quantitative µCT evaluations.
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| 2. |
- Lewin, Susanne, et al.
(författare)
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Implicit and explicit finite element models predict the mechanical response of calcium phosphate-titanium cranial implants
- 2020
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 112
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Tidskriftsartikel (refereegranskat)abstract
- The structural integrity of cranial implants is of great clinical importance, as they aim to provide cerebral protection after neurosurgery or trauma. With the increased use of patient-specific implants, the mechanical response of each implant cannot be characterized experimentally in a practical way. However, computational models provide an excellent possibility for efficiently predicting the mechanical response of patient-specific implants. This study developed finite element models (FEMs) of titanium-reinforced calcium phosphate (CaP-Ti) implants. The models were validated with previously obtained experimental data for two different CaP-Ti implant designs (D1 and D2), in which generically shaped implant specimens were loaded in compression at either quasi-static (1 mm/min) or impact (5 kg, 1.52 m/s) loading rates. The FEMs showed agreement with experimental data in the force-displacement response for both implant designs.The implicit FEMs predicted the peak load with an underestimation for D1 (9%) and an overestimation for D2 (11%). Furthermore, the shape of the force-displacement curves were well predicted. In the explicit FEMs, the first part of the force-displacement response showed 5% difference for D1 and 2% difference for D2, with respect to the experimentally derived peak loads. The explicit FEMs efficiently predicted the maximum dis-placements with 1% and 4% difference for D1 and D2, respectively. Compared to the CaP-Ti implant, an average parietal cranial bone FEM showed a stiffer response, greater energy absorption and less deformation under the same impact conditions.The framework developed for modelling the CaP-Ti implants has a potential for modelling CaP materials in other composite implants in future studies since it only used literature based input and matched boundary conditions. Furthermore, the developed FEMs make an important contribution to future evaluations of patient specific CaP-Ti cranial implant designs in various loading scenarios.
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| 3. |
- Lewin, Susanne, et al.
(författare)
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Mechanical behaviour of composite calcium phosphate-titanium cranial implants : Effects of loading rate and design
- 2020
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 104
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Tidskriftsartikel (refereegranskat)abstract
- Cranial implants are used to repair bone defects following neurosurgery or trauma. At present, there is a lack of data on their mechanical response, particularly in impact loading. The aim of the present study was to assess the mechanical response of a recently developed composite calcium phosphate-titanium (CaP-Ti) implant at quasi-static and impact loading rates. Two different designs were tested, referred to as Design 1 (D1) and Design 2 (D2). The titanium structures in the implant specimens were additively manufactured by a powder-bed fusion process and subsequently embedded in a self-setting CaP material. D1 was conceptually representative of the clinically used implants. In D2, the titanium structure was simplified in terms of geometry in order to facilitate the manufacturing. The mechanical response of the implants was evaluated in quasi-static compression, and in impact using a drop-tower. Similar peak loads were obtained for the two designs, at the two loading rates: 808 ± 29 N and 852 ± 34 for D1, and 840 ± 40 N and 814 ± 13 for D2. A strain rate dependency was demonstrated for both designs, with a higher stiffness in the impact test. Furthermore, the titanium in the implant fractured in the quasi-static test (to failure) but not in the impact test (to 5.75 J) for D1. For D2, the displacement at peak load was significantly lower in the impact test than in the quasi-static test. The main difference between the designs was seen in the quasi-static test results where the deformation zones, i.e. notches in the titanium structure between the CaP tiles, in D1 likely resulted in a localization of the deformation, compared to in D2 (which did not have deformation zones). In the impact test, the only significant difference between the designs was a higher maximum displacement of D2 than of D1. In comparison with other reported mechanical tests on osteoconductive ceramic-based cranial implants, the CaP-Ti implant demonstrates the highest reported strength in quasi-static compression. In conclusion, the titanium structure seems to make the CaP-Ti implant capable of cerebral protection in impact situations like the one tested in this study.
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| 4. |
- Lundesjö Kvart, Susanne, 1969-
(författare)
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Konsten att undervisa ryttare : En studie om ridlärares pedagogiska praktik
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns how riding teachers’ reflect upon their teaching and how they teach. The overall aim of the thesis is to contribute with knowledge about how riding lessons are organized, regarding both the accomplishment of lessons as activity systems and the interactional organization of instructional work. Horseback riding can be understood as an embodied and practical knowledge, and includes communication and collaboration between horse and rider, sometimes referred to as equestrian feel (Dashper, 2016). Two different theoretical perspectives were applied to explore how such knowledge is taught. Activity theory (Engeström, 1987) was used to analyze interviews with and observations of ten riding teachers about their understanding and implementation of their pedagogical practice. Teachers’ and students’ interactions during riding lessons were examined using an ethnomethodological and conversation analytic approach (Goodwin, 2000; Schegloff, 1996). The analyses were based on video-recordings of ten group lessons and 40 one-on-one riding lessons.The results show that riding lessons can be conceptualized as activity systems where the focus of teaching constantly changes; from horse to student to routine. Traditions and safety regulations are shown to generate contradictions that may hinder the teachers from developing their teaching. However, the teachers express a wish to use more student collaborative methods, and display an intention to communicate with students about equestrian feel. Another result unveils how the teacher and the individual students, within the mobile context of riding lessons, make instructional sequences possible by co-creating instructional spaces. A third result illuminates the participants’ collaborative work to make equestrian feel available for instruction. The teacher molds equestrian feel through online instructions, i.e., instructions produced during the students’ active riding. These instructions shift focus between the students’ seat and influence, the horse’s actions and the student’s embodied feel. Moreover, the teachers are shown to use visual, verbal and embodied resources as they interpret equestrian feel for the student. In sum, the studies shed light on the complex art of teaching practical and embodied knowledge of riding.
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| 5. |
- Mustamäki, Noora, et al.
(författare)
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Fjällbacka, Västerhavet, 1989–2019; Torhamn, södra Egentliga Östersjön, 2002–2019; Kvädöfjärden, Egentliga Östersjön, 1981–2019; Holmöarna, Bottniska viken, 1989–2019
- 2020
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Ingår i: Faktablad från integrerad kustfiskövervakning.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Inom den nationella miljöövervakningen av kust och hav bedrivs årligen sedan slutet av 1980-talet ett program för integrerad kustfiskövervakning i fyra nationella referensområden, ett vardera i Bottniska viken, Egentliga Östersjön, södra Egentliga Östersjön och Västerhavet. Syftet med programmet är att kartlägga fiskbeståndens status samt fiskens hälsotillstånd och miljögiftsbelastning för att upptäcka förändringar som indikerar storskalig påverkan av miljöhot som eutrofiering, miljögifter, klimatförändringar och andra miljöfaktorer. Detta faktablad sammanfattar resultaten från den integrerade kustfiskövervakningen i alla fyra områden under tidsperioden 1980–2019.
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| 6. |
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| 7. |
- Söderlund, Stina, et al.
(författare)
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Plasma proteomics of biomarkers for inflammation or cancer cannot predict relapse in chronic myeloid leukaemia patients stopping tyrosine kinase inhibitor therapy
- 2020
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Ingår i: Leukemia research. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0145-2126 .- 1873-5835. ; 90
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have now shown that chronic myeloid leukaemia (CML) patients in deep molecular remission may discontinue tyrosine kinase inhibitor (TKI) treatment with a treatment free remission (TFR) rate of approximately 40-60 %. Some factors influencing the possibility of TFR have been described but better tools are needed for individual prediction of long-term TFR. Herein, two multiplex panels were utilised to analyse a total of 162 different plasma proteins from 56 patients included in the TKI stopping trial EURO-SKI (Saussele a al., 2018). The purpose was to identify possible plasma protein markers for prediction of successful TKI discontinuation and to evaluate effects of TKI discontinuation on plasma protein profiles. No protein biomarkers sampled before TKI discontinuation could separate relapse cases from non-relapse cases but some plasma proteins differed between patients who relapsed and those who remained in TFR when followed over time after TKI cessation. In conclusion, the plasma protein markers in this study could not predict relapse after TKI discontinuation but may be of use to understand the mechanisms involved in maintenance of TFR.
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| 8. |
- Åkesson, Lynn, et al.
(författare)
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Fastighetsnära källsortering ur de boendes perspektiv : blev det lätt och rätt?
- 2020
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Ingår i: Ekostaden Augustenborg : erfarenheter och lärdomar - erfarenheter och lärdomar. - 9789151978673 ; 78, s. 234-244
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Bokkapitel (refereegranskat)abstract
- Studien handlar om hur de som bor i stadsdelen Augustenborg i Malmö använde och upplevde den avfallshantering som introducerades 2008. Hur hållbara avfallssystem kan åstadkommas diskuteras med utgångspunkt i användning och upplevelse av den lokala avfallshanteringen. De primära frågeställningarna är:• Vilka begrepp och kategorier skapar och använder invånarna när det gäller avfall i vardagen? Hur fungerar dessa kategorier i praktiken när avfall ska sorteras, hur lärs de in och blir till självklarheter?• Hur väl fungerar källsorteringen? Hur mycket är sorterat och hur mycket är korrekt sorterat?• Hur förhåller sig invånarnas sätt att tänka om källsortering och deras faktiska agerande, till det sorteringssystem som finns i Augustenborg? Finns det lärdomar att dra om hur klyftan mellan avfallssystemet och användarnas uppfattningar och vanor kan överbryggas?
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