A Method for Prediction of Femoral Component of Hip Prosthesis Durability due to Aseptic Loosening by Using Coffin/Manson Fatigue Model

The purpose of this work is to develop a new model estimate of the fatigue life of a hip prosthesis due to aseptic loosening as a multifactorial phenomenon. The formula developed here is a three-parameter model based on Basquin’s law for fatigue, eccentric compression formula for the compressive stress and torsion in the prosthesis due to the horizontal components of the contact force. With our model, we can accurately predict the durability of a hip prosthesis due to the following four parameters: body weight, femoral offset, duration, and intensity of daily physical activities of a patient. The agreement of the prediction with the real life of the prosthesis, observed on 15 patients, is found to be adequate. Based on the formula derived for a particular implant, there was a high degree of concurrence between the model-predicted and actual values of aseptic loosening (durability) proved by the Mann–Whitney U test. By virtue of the validated model, it is possible to predict, quantitatively, the influence of various factors on the hip life. For example, we can conclude that a 10% decrease of a patient’s body mass, with all other conditions being the same, causes 5% increase of the hip fatigue life

Similarities and Differences in Epidemiology and Risk Factors of Cerebral and Myocardial Ischemic Disease

Ischemic heart disease and cerebral ischemia represent the leading causes of mortality worldwide. Both entities share risk factors, pathophisiology and etiologic aspects by means of a main common mechanism, atherosclerosis. The autors aimed to investigate differences and similarities in epidemiology and risk factors that could be found between both entities. In a retrospective sudy 403 patients were included and divided into two groups: group of 289 patients with history of myocardial infarction (AMI), and group of 114 patients with history of ischemic stroke (IS). All patients were evaluated for nonmodifiable risk faktors, which included age and sex, and modifiable, such as hypertension, dyslipidemia, diabetes, obesity, physical activity and smoking. Diff erences in some epidemiological aspects were also considered: occupation, marital status, alcohol consumption, exposure to stress. Patients with history of IS were significantly older then AMI patients (64.0 ± 9.9 vs 64.0 ± 9.9, p=0,028), with higher diastolic blood pressure (87,1 ± 10,2 vs 83,6 ± 10,4, p=0,003) and higher Sokolow-Lyon index in ECG, an also index of left ventricular hypertrophy (19,2 ± 9,1 vs 14,7 ± 6,5). Th ere were no significant differences between groups in the estimated body mass index and waist circumference. Differences between groups in stress exposure, occupation, alcohol consumption or physical activity were no significant. Patients in AMI group were more frequently male (199 (69%) vs 59 (52%), p=0,001), married (252 (87%) vs 88 (77%), p=0,037), smokers (162 (56%) vs 50 (44%), p=0,018) and with higher incidence od dyslipidemia (217 (75%) vs 73 (64%), p=0,019) compared with IS group. Incidence of arterial hypertension and diabetes was similar in both groups. Both entities share similar pathophysiological mechanisms and, consequently, main traditional risk factors. However, incidence of myocardial infarction increases with male sex, dyslipidemia, smoking and marital status, while incidense of ischemic stroke increases with age, higher diastolic blood pressure and also with ECG signs of left ventricular hypertrophy