Journal of biomechanics
-
Journal of biomechanics · Jun 2012
Effect of subtalar arthroereisis on the tibiotalar contact characteristics in a cadaveric flatfoot model.
Previous studies reported the effect of flatfoot deformity on tibiotalar joint contact characteristics. The lateral shift of the load which occurred in flatfeet may be responsible for degenerative changes in the ankle joint. The purpose was to assess the pattern of joint contact stress of the tibiotalar joint in intact, flat, and corrected specimens with subtalar arthroereisis. ⋯ After subtalar arthroereisis with the Kalix implant for correction of the flatfoot deformity a maximum contact pressure of 1323.3±497.5 kPa was observed in the middle-lateral region. In a cadaver model, subtalar arthroereisis with Kalix implant failed to restore a normal intraarticular ankle joint pressure pattern. Further interventions should be considered to restore a normal pressure pattern.
-
Journal of biomechanics · Jun 2012
Mechanical interaction of center of pressure and force direction in the upright human.
Humans maintain upright bipedal posture by producing appropriate force against the environment through the interaction of neural controlled muscle force with the mechanics of the skeletal system. Characterizing these mechanics facilitates understanding of the neural control. We used a mechanical model of an upright human to analyze how the mechanical linkage aspects of the human body affect the force between the feet and the ground (F). ⋯ The Π was located above the center of mass when the hip and knee joints were modeled as rigid and was located near the knee when the hip and knee torques were held constant. Limb posture and the knee torque affected the location of Π. This Π behavior quantifies the purely mechanical effect of anterior-posterior center of pressure shifts on the direction of F, which has consequences for the control of whole body posture.
-
Limited knowledge exists regarding the forces which act on devices implanted to the heart's mitral valve. Developing a transducer to measure the peak force magnitudes, time rates of change, and relationship with left ventricular pressure will aid in device development. A novel force transducer was developed and implanted in the mitral valve annulus of an ovine subject. ⋯ Combined, this study provides the first quantitative assessment of septal-lateral and transverse forces within the contractile mitral annulus. The developed transducer was successful in measuring these forces whose methods may be extended to future studies. Upon additional investigation, these data may contribute to the safer development and evaluation of devices aimed to repair or replace mitral valve function.
-
Journal of biomechanics · May 2012
Flow resistance analysis of extracranial-to-intracranial (EC-IC) vein bypass.
Although brain bypass surgery has often been selected to treat internal carotid arteries (ICA) which are restricted by aneurysm or artery stenosis, its effectiveness has not been quantitatively evaluated. The purpose of this study is to propose an innovative approach for the evaluation of brain extracranial-to-intracranial (EC-IC) vein bypass surgery, based on the analysis of flow resistance in vein bypasses and within their contralateral carotid arteries through the use of computational fluid dynamics (CFD). Seven patients who underwent vein bypass surgery were examined with the use of high-resolution; computed tomography angiogram (CTA). ⋯ For the vein bypass, an average value of A was 0.0143 Pa/(ml/min)² and B 3.402 Pa/(ml/min), which was approximately that of a healthy ICA. However, in the case of a bypass utilising a venous conduit possessing a large-sized valve or existing size alteration, the flow resistance in that bypass would be higher than those found in the healthy ICA. An imbalance of flow resistances may impose conditions that could predispose hemodynamic failure or distal aneurysm development.