A clinical, radiological and biomechanical study of the TARA hip prosthesis

We reviewed 60 patients with 72 TARA (total articular replacement arthroplasty) resurfacing hip prostheses. To analyse the behaviour of the femoral component a radiographic study was done and a two-dimensional finite element model was constructed. The stem of the femoral component plays a role in the load transfer mechanism. Stress shielding is seen in the proximal femur but depends on the interface conditions. When only the dome of the cup is assumed to be bonded to the bone, the stresses in the head increase dramatically and there is no more stress shielding. Five years after implantation radiographic signs of loosening of the femoral component were seen in 6.8% of the implants placed without notching in the femoral neck and in 28.6% of the components with notching (significant difference, P = 0.0005). Signs of loosening of the acetabular component were seen in 37.7% 5 years postoperatively. The cumulative survival rates of the femoral and acetabular components were 89.7% and 85.6% respectively 5 years after implantation. The overall clinical results are represented by an integration of the clinical results (Harris Hip Score System), the radiographic results and the survival analysis. This gave a success rate of only 72% 5 years after implantation

Acclimatisation and adaptive capacity of sea urchins in a changing ocean: Effects of ocean warming and acidification on early development and the potential to persist

Anthropogenic emissions of carbon dioxide are causing the oceans to simultaneously increase in temperature and acidification. As the life cycle of many marine invertebrates involves broadcast spawning, understanding the sensitivity of gametes, fertilisation and developmental stages is essential to determining species vulnerability to ocean change stressors. This thesis uses free spawning echinoids as model species to address this issue with an aim to identify effects of ocean acidification on the extracellular jelly coat of the egg with a focus on four sea urchin species; Centrostephanus rodgersii, Heliocidaris erythrogramma, Heliocidaris tuberculata, Echinometra mathaei. As sea urchins provide a tractable system for study of gamete and fertilisation responses to stressors, as well as investigation of genetic variation, the genetic basis of resistance to climate change stressors is also investigated in polar, tropical and temperate sea urchins: Sterechinus neumayeri, Pseudoboletia indiana and Heliocidaris erythrogramma. Data from the experiments across the all species show inherent differences in the response of gametes to ocean stressors, as well as differences in gamete compatibility which can drive differing responses to ocean change. Across polar, tropical and temperate sea urchins, the mechanisms that may facilitate persistence in a changing ocean differ, revealing the potential winners and losers

Health scares: professional priorities

Currently, many health scholars are concerned about health scares. But what do they mean by the term ‘health scare’ – are health scares an identifiable phenomenon, and how do we currently understand their causation and consequences? By collecting and analyzing published articles about events considered to be health scares, this paper maps the current views of scholars on their characteristics and causes. Results show that health scares are generally understood as events characterized by fears of catastrophic consequences but little actual mortality. However, the social and economic impacts of these events have often been severe. This survey shows that health scares can be usefully sorted into 6 categories, each with identifiable internal dynamics, suggesting different communications strategies to achieve resolution in each category. Using the social amplification of risk framework, the conditions under which risk signals were amplified were traced in general terms among major stakeholders. Simple causes for health scare events could not be identified, though some triggers did emerge. Importantly, public ignorance of real risk, media scaremongering, and political inaction could be dismissed as primary explanations, though they were sometimes factors in scare events. Implications for risk communication and for future research on risk and public health are discussed. Keywords: Health scare, Social amplification of risk, Expert, Media, Risk controversyfunded by the Sidney Sax Travelling Postdoctoral Research Fellowship in Public Health, National Health and Medical Research Council, Australia

Refractive and visual outcomes of femtosecond laser-assisted cataract surgery

Objective: To compare refractive and visual acuity outcomes of femtosecond laser-assisted cataract surgery (FLACS) to manual surgery. Participants: Consecutive series of patients in a private ophthalmic practice in Sydney, with 337 eyes undergoing FLACS on the LenSx platform and 230 eyes manual cataract surgery. Main Outcome Measures: Astigmatism, surgically-induced corneal astigmatism, achievement of target refraction and corrected and uncorrected distance visual acuity (UDVA). Results: The FLACS group had statistically less mean residual post-operative astigmatism by 0.18D (p<0.001) than the manual group. The femtosecond laser produced equivalent mean magnitude and variability of surgically-induced corneal astigmatism compared to manual cataract surgery. Both surgical methods had equivalent achievement of target spherical equivalent (69% within 0.5 D of target refraction, p=0.911). In eyes with good visual potential and an emmetropic target, post-operative UDVA was statistically better in the femtosecond group with an average improvement of 2.4 logMAR letters (p=0.020). Conclusions: Femtosecond cataract surgery produced less residual post-operative refractive astigmatism and better unaided distance visual acuity compared to manual cataract surgery. However there was no improvement in the achievement of target post-operative refraction

Design and Topology Optimisation of Tissue Scaffolds

Tissue restoration by tissue scaffolding is an emerging technique with many potential applications. While it is well-known that the structural properties of tissue scaffolds play a critical role in cell regrowth, it is usually unclear how optimal tissue regeneration can be achieved. This thesis hereby presents a computational investigation of tissue scaffold design and optimisation. This study proposes an isosurface-based characterisation and optimisation technique for the design of microscopic architecture, and a porosity-based approach for the design of macroscopic structure. The goal of this study is to physically define the optimal tissue scaffold construct, and to establish any link between cell viability and scaffold architecture. Single-objective and multi-objective topology optimisation was conducted at both microscopic and macroscopic scales to determine the ideal scaffold design. A high quality isosurface modelling technique was formulated and automated to define the microstructure in stereolithography format. Periodic structures with maximised permeability, and theoretically maximum diffusivity and bulk modulus were found using a modified level set method. Microstructures with specific effective diffusivity were also created by means of inverse homogenisation. Cell viability simulation was subsequently conducted to show that the optimised microstructures offered a more viable environment than those with random microstructure. The cell proliferation outcome in terms of cell number and survival rate was also improved through the optimisation of the macroscopic porosity profile. Additionally artificial vascular systems were created and optimised to enhance diffusive nutrient transport. The formation of vasculature in the optimisation process suggests that natural vascular systems acquire their fractal shapes through self-optimisation

Resection arthroplasty for luxation of the manubrio-sternal joint in rheumatoid arthritis—a case report

Contains fulltext : 89408.pdf (publisher's version ) (Open Access)1 juni 201

A sliding stem in revision total knee arthroplasty provides stability and reduces stress shielding: An RSA study using impaction bone grafting in synthetic femora

Contains fulltext : 87345.pdf (publisher's version ) (Open Access)BACKGROUND AND PURPOSE: In the reconstruction of unicondylar femoral bone defects with morselized bone grafts in revision total knee arthroplasty, a stem extension appears to be critical to obtain adequate mechanical stability. Whether stability is still assured by this reconstruction technique in bicondylar defects has not been assessed. The disadvantage of relatively stiff stem extensions is that bone resorption is promoted due to stress shielding. We therefore designed a stem that would permit axial sliding movements of the articulating part relative to the intramedullary stem. METHODS: This stem was used in the reconstruction with impaction bone grafting (IBG) of 5 synthetic distal femora with a bicondylar defect. A cyclically axial load was applied to the prosthetic condyles to assess the stability of the reconstruction. Radiostereometry was used to determine the migrations of the femoral component with a rigidly connected stem, a sliding stem, and no stem extension. RESULTS: We found a stable reconstruction of the bicondylar femoral defects with IBG in the case of a rigidly connected stem. After disconnecting the stem, the femoral component showed substantially more migrations. With a sliding stem, rotational migrations were similar to those of a rigidly connected stem. However, the sliding stem allowed proximal migration of the condylar component, thereby compressing the IBG. INTERPRETATION: The presence of a functional stem extension is important for the stability of a bicondylar reconstruction. A sliding stem provides adequate stability, while stress shielding is reduced because compressive contact forces are still transmitted to the distal femoral bone.1 juni 201