Search

1 augustus 2012, Item does not contain fulltext, Previously, we showed that case-specific non-linear finite element (FE) models are better at predicting the load to failure of metastatic femora than experienced clinicians. In this study we improved our FE modelling and increased the number of femora and characteristics of the lesions. We retested the robustness of the FE predictions and assessed why clinicians have difficulty in estimating the load to failure of metastatic femora. A total of 20 femora with and without artificial metastases were mechanically loaded until failure. These experiments were simulated using case-specific FE models. Six clinicians ranked the femora on load to failure and reported their ranking strategies. The experimental load to failure for intact and metastatic femora was well predicted by the FE models (R(2) = 0.90 and R(2) = 0.93, respectively). Ranking metastatic femora on load to failure was well performed by the FE models (tau = 0.87), but not by the clinicians (0.11 < tau < 0.42). Both the FE models and the clinicians allowed for the characteristics of the lesions, but only the FE models incorporated the initial bone strength, which is essential for accurately predicting the risk of fracture. Accurate prediction of the risk of fracture should be made possible for clinicians by further developing FE models.

Contains fulltext : 80687.pdf (publisher's version ) (Open Access)

Contains fulltext : 81864.pdf (publisher's version ) (Closed access), PURPOSE: In clinical practice, there is an urgent need to improve the prediction of fracture risk for cancer patients with bone metastases. The methods that are currently used to estimate fracture risk are dissatisfying, hence affecting the quality of life of patients with a limited life expectancy. The purpose of this study was to assess if non-linear finite element (FE) computer models, which are based on Quantitative Computer Tomography (QCT), are better than clinical experts in predicting bone strength. MATERIALS AND METHODS: Ten human cadaver femurs were scanned using QCT. In one femur of each pair a hole (size 22, 40, or 45 mm diameter) was drilled at the anterior or medial side to simulate a metastatic lesion. All femurs were mechanically tested to failure under single-limb stance-type loading. The failure force was calculated using non-linear FE-models, and six clinical experts were asked to rank the femurs from weak to strong based on X-rays, gender, age, and the loading protocol. Kendall Tau correlation coefficients were calculated to compare the predictions of the FE-model with the predictions of the clinicians. RESULTS: The FE-failure predictions correlated strongly with the experimental failure force (r(2)=0.92, p<0.001). For the clinical experts, the Kendall Tau coefficient between the experimental ranking and predicted ranking ranged between tau=0.39 and tau=0.72, whereas this coefficient was considerably higher (tau=0.78) for the FE-model. CONCLUSION: This study showed that the use of a non-linear FE-model can improve the prediction of bone strength compared to the prediction by clinical experts.

Contains fulltext : 58480.pdf (publisher's version ) (Closed access), Objective. The functional role of HLA class II molecules in the pathogenesis of rheumatoid arthritis (RA) is unclear. HLA class II molecules are involved in the interaction between T and B lymphocytes required for long-lived B cell responses and generation of high-affinity IgG antibodies. We undertook this study to investigate the relationship between HLA class II gene polymorphisms and RA-specific IgG antibodies against cyclic citrullinated peptides (anti-CCP antibodies). Methods. High-resolution HLA-DR and DQ typing and anti-CCP-2 antibody testing were performed on 268 RA patients from the Early Arthritis Clinic cohort at the Department of Rheumatology of the Leiden University Medical Center. The presence of anti-CCP antibodies was analyzed in carriers of the different DR and DQ alleles. Disease progression was measured over a period of 4 years by scoring radiographs of the hands and feet using the Sharp/van der Heijde method. Results. Carriership of the individual alleles HLA-DRBt*0401, DRB1*1001, DQB1*0302, and DQBI*0501 was associated with the presence of antiCCP antibodies. Carriers of DQ-DR genotypes containing proposed RA susceptibility alleles were significantly more often anti-CCP antibody positive. Carriership of one or two HLA-DRB1 shared epitope (SE) alleles was significantly associated with production of anti-CCP antibodies (odds ratio [OR] 3.3, 95% confidence interval [95% CI] 1.8-6.0 and OR 13.3, 95% CI 4.6-40.4, respectively). An increased rate of joint destruction was observed in SE+, anti-CCP+ patients (mean Sharp score 7.6 points per year) compared with that in SE-, anti-CCP+ patients (2.4 points per year) (P = 0.04), SE+, anti-CCP- patients (1.6 points per year) (P < 0.001), and SE-, anti-CCP- patients (1.6 points per year) (11 < 0.001). Conclusion. HLA class II RA susceptibility alleles are associated with production of anti-CCP antibodies. Moreover, more severe disease progression is found in RA patients with both anti-CCP antibodies and SE al

Item does not contain fulltext