The determinants of change in tibial plateau bone area in osteoarthritic knees: a cohort study

Bone is integral to the pathogenesis of osteoarthritis (OA). Whether the bone area of the tibial plateau changes over time in subjects with knee OA is unknown. We performed a cohort study to describe this and identify factors that might influence the change. One hundred and twenty-six subjects with knee OA underwent baseline knee radiography and magnetic resonance imaging on their symptomatic knee. They were followed up with a repeatmagnetic resonance image of the same knee approximately 2 years later. The bone area of the tibial plateau was measured at baseline and follow-up. Risk factors assessed at baseline were tested for their association with change in tibial plateau bone area over time. One hundred and seventeen subjects completed the study. The medial and lateral tibial plateau bone areas increased by 2.2 ± 6.9% and 1.5 ± 4.3% per year, respectively. Being male (P = 0.001), having a higher body mass index (P = 0.002), and having a higher baseline grade of medial joint-space narrowing (P = 0.01) were all independently and positively associated with an increased rate of enlargement of bone area of the medial tibial plateau. A larger baseline bone area of the medial tibial plateau was inversely associated with the rate of increase of that area (P < 0.001). No factor examined affected the rate of increase of the bone area of the lateral tibial plateau. In subjects with established knee OA, tibial plateau bone area increases over time. The role of subchondral bone change in the pathogenesis of knee OA will need to be determined but may be one explanation for the mechanism of action of risk factors such as body mass index on knee OA

Empirical study of user experience on mobile data collection for chronic low back pain

The majority of all IS implementation projects fails. McFarlan (1981) identified risk factors associated with organizational IT projects and created a model to predict project risk. The McFarlan Risk Model (MRM) provides a useful approach for the diagnosis and mitigation of IT project risks but can be improved in its predictive ability. In this paper, we suggest to augment the model, beyond its original three dimensions. Based on recent literature, which points to the importance of culture, specifically corporate culture, we develop an extension to McFarlan’s model and assess the added value of this extended model through the evaluation of two business cases. Expert evaluations using the Extended McFarlan Risk Model (EMRM) indicate higher predictive power in the differentiation of project success and failure, based on differences in the model’s culture dimension

Slice Thickness in the Assessment of Medial and Lateral Tibial Cartilage Volume and Accuracy for the Measurement of Change in a Longitudinal Study

P e r s o n a l n o n -c o m m e r c i a l u s e o n l y . T h e J o u r n a l o f R h e u m a t o l o g y . C o p y r i g h t © 2 0 0 4 . A l l r i g h t s r e s e r v e d ABSTRACT. Objective. The optimal magnetic resonance image (MRI) slice thickness required to assess cartilage volume accurately and efficiently in cross-sectional and longitudinal studies is unknown. We compared cartilage volume measured from MRI of the knees using different slice thicknesses (1.5 to 7.5 mm) and assessed longitudinal change. Methods. A total of 123 subjects with osteoarthritis had baseline and followup MRI on their symptomatic knee at 2 years. Medial and lateral tibial cartilage volumes were calculated using increasing slice thickness by extracting each second, third, fourth, or fifth slice area to calculate total volume, which was compared to the &quot;gold standard&quot; volume calculated from the original 1.5 mm slices. Results. There was little difference in the average medial and lateral tibial cartilage volume observed as the slice thickness increased from 1.5 to 7.5 mm; medial tibial cartilage volume ranged from 1750 µl to 1787 µl and lateral tibial cartilage volume ranged from 1949 µl to 2007 µl. There was also little absolute difference in the average change in medial and lateral tibial cartilage volume measured over 2 years. However, with increasing slice thickness, there was a decreased correlation between the tibial cartilage volume change calculated from the increased slice thickness, with the lowest correlation being 0.77 (p &lt; 0.001) when the lateral cartilage volume calculated from the 7.5 mm slice was compared to the 1.5 mm slices. Conclusion. Increasing slice thickness may provide sufficiently accurate measurement of tibial cartilage volume and change over time in some studies. This would result in reduction in MRI scanning and postimaging processing time, which has the potential of increasing the feasibility of this technique. (J Rheumatol 2004;31:2444-8

Optimal sampling of MRI slices for the assessment of knee cartilage volume for cross-sectional and longitudinal studies

BACKGROUND: MRI slices of 1.5 mm thickness have been used in both cross sectional and longitudinal studies of osteoarthritis, but is difficult to apply to large studies as most techniques used in measuring knee cartilage volumes require substantial post-image processing. The aim of this study was to determine the optimal sampling of 1.5 mm thick slices of MRI scans to estimate knee cartilage volume in males and females for cross-sectional and longitudinal studies. METHODS: A total of 150 subjects had a sagittal T1-weighted fat-suppressed MRI scan of the right knee at a partition thickness of 1.5 mm to determine their cartilage volume. Fifty subjects had both baseline and 2-year follow up MRI scans. Lateral, medial tibial and patellar cartilage volumes were calculated with different samples from 1.5 mm thick slices by extracting one in two, one in three, and one in four to compare to cartilage volume and its rate of change. Agreement was assessed by means of intraclass correlation coefficient (ICC) and Bland & Altman plots. RESULTS: Compared to the whole sample of 1.5 mm thick slices, measuring every second to fourth slice led to very little under or over estimation in cartilage volume and its annual change. At all sites and subgroups, measuring every second slice had less than 1% mean difference in cartilage volume and its annual rate of change with all ICCs ≥ 0.98. CONCLUSION: Sampling alternate 1.5 mm thick MRI slices is sufficient for knee cartilage volume measurement in cross-sectional and longitudinal epidemiological studies with little increase in measurement error. This approach will lead to a substantial decrease in post-scan processing time