Explaining and predicting the increased thorax injury in aged females: age and subject-specific thorax geometry coupled with improved bone constitutive models and age-specific material properties evaluated in side impact conditions.

Predicting and understanding thorax injury is fundamental for the assessment and development of safety systems to mitigate injury risk to the increasing and vulnerable aged population. While computational human models have contributed to the understanding of injury biomechanics, contemporary human body models have struggled to predict rib fractures and explain the increased incidence of injury in the aged population. The present study enhanced young and aged human body models (HBMs) by integrating a biofidelic cortical bone constitutive model and population-based bone material properties. The HBMs were evaluated using side impact sled tests assessed using chest compression and number of rib fractures. The increase in thoracic kyphosis and the associated change in rib angle with increasing age, led to increased rib torsional moment increasing the rib shear stress. Coupled with and improved cortical bone constitutive model and aged material properties, the higher resulting shear stress led to an increased number of rib fractures in the aged model. The importance of shear stress resulting from torsional load was further investigated using an isolated rib model. In contrast, HBM chest compression, a common thorax injury-associated metric, was insensitive to the aging factors studied. This study proposes an explanation for the increased incidence of thorax injury with increasing age reported in epidemiological data, and provides an enhanced understanding of human rib mechanics that will benefit assessment and design of future safety systems.

Effect of muscle pre-tension and pre-impact neck posture on the kinematic response of the cervical spine in simulated low-speed rear impacts.

Computational human body models (HBMs) can identify potential injury pathways not easily accessible through experimental studies, such as whiplash induced injuries. However, previous computational studies investigating neck response to simulated impact conditions have neglected the effect of pre-impact neck posture and muscle pre-tension on the intervertebral kinematics and tissue-level response. The purpose of the present study was addressing this knowledge gap using a detailed neck model subjected to simulated low-acceleration rear impact conditions, towards improved intervertebral kinematics and soft tissue response for injury assessment. An improved muscle path implementation in the model enabled the modeling of muscle pre-tension using experimental muscle pre-stretch data determined from previous cadaver studies. Cadaveric neck impact tests and human volunteer tests with the corresponding cervical spine posture were simulated using a detailed neck model with the reported boundary conditions and no muscle activation. Computed intervertebral kinematics of the model with pre-tension achieved, for the first time, the S-shape behavior of the neck observed in low severity rear impacts of both cadaver and volunteer studies. The maximum first principal strain in the muscles for the model with pre-tension was 27% higher than that without pre-tension. Although, the pre-impact neck posture was updated to match the average posture reported in the experimental tests, the change in posture was generally small with only small changes in vertebral kinematics and muscle strain. This study provides a method to incorporate muscle pre-tension in HBM and quantifies the importance of pre-tension in calculating tissue-level distractions.

Atorvastatin in dyslipidaemia of the nephrotic syndrome.

The combined dyslipidaemia that accompanies the nephrotic syndrome increases the cardiovascular risk and appears to worsen long-term renal function. Our aim was to determine the efficacy and safety of 10 mg atorvastatin in the control of dyslipidaemia in these patients. We carried out a prospective, open, 6 month study of 10 patients with primary or secondary nephrotic syndrome (proteinuria >3.5 g/day, hypoalbuminaemia, oedema and hyperlipidaemia). The changes in lipids and plasma lipoproteins were measured, as well as the safety profile (transaminases, creatine phosphokinase, fibrinogen and antithrombin III activity) and parameters of renal function. The addition of 10 mg atorvastatin daily for 6 months resulted in a 41% reduction in low density lipoprotein (LDL) cholesterol and 31% in triglycerides (both P < 0.05), and a 15% increase in high density lipoprotein (HDL) cholesterol (NS). The drug was well tolerated and there was no change in the safety profile or deterioration in renal function. In fact, the levels of proteinuria fell in all but one patient (6.2 +/- 2.6 vs 4.8 +/- 2.5 g/24 h; P < 0.05). Atorvastatin, at the above dose, and for the time used proved to be a safe drug that effectively reduced dyslipidaemia in patients with nephrotic syndrome.