RESUMO
Osteoporosis is a serious and multifactorial disease. The number of people affected with osteoporosis is increasing due to the lengthening of life expectancy. Currently, unlike the genetic, nutritional and hormonal factors that have been the focus of most studies of osteoporosis, mechanical stimuli that potentially can produce an increase in bone strength have not been well studied. Studies suggest that the relationship between the health of the bone and mechanical stimuli occurs through bone adaptive remodeling, which is activated by means of the shear stress transmitted by the interstitial fluid flow. The present work consists of a finite element analysis of a femur to simulate the basic movements of the hip (flexion, extension, abduction, and adduction) to compare the shear stresses in a common zone of fracture and in the critical mechanical strength zones of the femoral head. A comparison of the distribution and magnitude of the shear stresses was performed to estimate the movement that could induce a more rapid adaptive bone remodeling. This study is the first step in the development of a physical therapy for a preventive rehabilitation that helps to prevent patients with low bone mineral density to avoid suffering osteoporosis hip fractures. The finite element model was constructed using a free-access three-dimensional standardized femur obtained from the Instituti Ortopedici Rizzoli, Bologna, Italy. The mechanical properties and the muscular forces were obtained from a specialized bibliography. We conclude that the movements that exhibit a higher mean value and a good shear stress distribution in the femoral neck are hip extension and abduction.
Assuntos
Densidade Óssea/fisiologia , Fraturas Ósseas/prevenção & controle , Articulação do Quadril/fisiologia , Osteoporose/patologia , Remodelação Óssea/fisiologia , Fêmur/metabolismo , Cabeça do Fêmur/metabolismo , Colo do Fêmur/metabolismo , Análise de Elementos Finitos , Articulação do Quadril/metabolismo , Articulação do Quadril/patologia , Humanos , Estresse MecânicoRESUMO
The aim of this study was to determine the prevalence and risk factors for low bone mineral density (BMD) in women with systemic lupus erythematosus (SLE). A cross-sectional study was conducted among 100 pre-menopausal patients with SLE. Patients were evaluated using a questionnaire about the following variables: age, disease duration, disease activity, chronic disease damage, cumulative corticosteroid dose, and history of fracture. Lumbar spine and hip measurements of BMD were performed by dual absorptiometry. Univariate and multivariate statistical analyses were used to assess the relationship between risk factors and BMD. The mean age was 32.8 +/- 8.7 years, and the median duration of SLE was 73.2 +/- 65 months. The mean cumulative corticosteroid dose was 20.0 +/- 21.3 g. The mean BMD was 1.09 +/- .18 g/cm(2) in the lumbar spine and 1.0 +/- .14 g/cm(2) in the hip. Osteopenia was present in 40% of patients and osteoporosis in 5%. In the multiple regression analysis, low BMD in the lumbar spine was associated with chronic disease damage and low body mass index (BMI). Low BMD in the hip was associated with cumulative corticosteroid dose and low BMI. Chronic disease damage, low BMI, and cumulative corticosteroid dose are risks factors for low BMD in pre-menopausal SLE patients. Osteopenia was found in 40% of patients, while osteoporosis was found in only 5%.