Dae-Gon Woo

Relationship between nutrition factors and osteopenia: Effects of experimental diets on immature bone quality

To investigate the influence of experimental diets on morphological and mechanical characteristics of immature bone, this study thoroughly examined the nutrition-bone connection. A non-destructive evaluation method involving high-resolution in-vivo micro-computed tomography and finite element (FE) analysis was used to investigate the relationship between obesity and osteopenia-two disorders of body composition. Correlation of nutritional deficiency with bone characteristics was also investigated. Some recent studies have shown that both obesity and osteopenia share several common genetic and environmental factors. However, there have been few studies correlating these pathologies in-vivo from a structural and biomechanical point of view. In the present study, detailed changes in morphological and mechanical characteristics of trabecular bone architecture were detected and tracked by longitudinal studies of morphometric parameters and simulated compression testing. Rats were randomized into three groups: overeaten diet (OD) for formation of obesity, normal diet (ND), and restricted diet (RD) in which rats received 65% of the normal diet. In the OD and ND groups, all structural parameters changed significantly (p<0.05). The degree of alteration in the structural parameters of the ND group was similar to that of the RD group (p<0.05). In simulated compression tests using FE models, the effective modulus of the OD group significantly decreased, depending on measuring time (p<0.05), whereas that of the ND and RD groups significantly increased (p>0.05). The key finding of the present study is that fat mass is morphologically and mechanically inversely correlated with bone mass when the mechanical loading effects of greater body weight on bone mass are applied.

Simulation of the Disc Degeneration with a Poroelastic Finite Element Model

To predict the degeneration process in the intervertebral disc, a finite element model of the spinal motion segment model was developed. The relationship between the biomechanical characteristics of fluid and solid matrix of the disc and cancellous core of the vertebral body, modeled as 20 node poroelastic elements, during the degeneration process was investigated. Excess von Mises stress in the disc element was assumed to be a possible source of degeneration under compressive loading condition. Recursive calculation was continued until the desired convergence was attained by changing the permeability and void ratio of those elements. The degenerated disc model showed that relatively small compressive stresses were generated in the nucleus elements compared to normal disc. Its distribution along the sagittal plane was consistent with a previously reported experimental result. Contrasts to this result, pore pressures in the nucleus were higher than those in the normal disc. Total stress, sum of compressive stress and pore pressure, indicated similar values for two different models. This study presented a new approach to study the likely mechanism responsible for the initiation and progression of the degenerative process within the intervertebral disc.

Relationship Between Obesity and Osteopenia in Lumbar Spines of Rats Using Mechanical and Morphological Studies

Obesity (OB) and osteopenia (OP), grave consequences for human health, quality of life, and even the efficiency of the labor force and economy, are two common complex diseases. Two public health problems have exploded in prevalence over the past decade [1]. OB, now a major epidemic in the developed world and frequent among elderly subjects, is a condition of excessive body fat that causes or exacerbates several risk of developing non-insulin dependent diabetes mellitus, cardiovascular disease, cancer and other diseases [2]. OP is defined as a systemic skeletal disease caused by low bone mass and microstructural deterioration of the bone.© 2008 ASME