Biphasic investigation of contact mechanics in natural human hips during activities

Abstract

The aim of this study was to determine the cartilage contact mechanics and the associated fluid pressurisation of the hip joint under eight daily activities, using a three-dimensional finite element hip model with biphasic cartilage layers and generic geometries. Loads with spatial and temporal variations were applied over time and the time-dependent performance of the hip cartilage during walking was also evaluated. It was found that the fluid support ratio was over 90% during the majority of the cycles for all the eight activities. A reduced fluid support ratio was observed for the time at which the contact region slid towards the interior edge of the acetabular cartilage, but these occurred when the absolute level of the peak contact stress was minimal. Over 10 cycles of gait, the peak contact stress and peak fluid pressure remained constant, but a faster process of fluid exudation was observed for the interior edge region of the acetabular cartilage. The results demonstrate the excellent function of the hip cartilage within which the solid matrix is prevented from high levels of stress during activities owing to the load shared by fluid pressurisation. The findings are important in gaining a better understanding of the hip function during daily activities, as well as the pathology of hip degeneration and potential for future interventions. They provide a basis for future subject-specific biphasic investigations of hip performance during activities.

Geometric parameterisation of pelvic bone and cartilage in contact analysis of the natural hip: An initial study

“…In this study, the maximum cartilage contact pressures were predicted to be 2.4–3.5 MPa for different activities when a spherical articulating surface and uniform cartilage thickness as well as a human body weight of 80 kg were considered. These contact pressures were found to be in good agreement with a previous FE study, 33 in which the cartilage contact pressures were reported to be 2.5–3.5 MPa for different activities when the same cartilage thickness and radial clearances were considered and the same kinematic and loading conditions were applied, providing some verification for the segmentation-based model and parameterised model in this study. Yoshida et al 16 developed dynamic discrete element models to predict hip joint contact pressures and reported peak values of 3.26, 3.77 and 5.71 MPa during walking, descending stairs and ascending stairs, respectively, which are also comparable with the results predicted in this study.…”

“… 1 , 3 Analysis of the contact mechanics is therefore limited to instantaneous behaviour, and although comparisons of contact mechanics between different geometric cases have merit for ranking the effect of geometric features, magnitudes are not representative of the in vivo case. Future studies using the parameterised hip model could therefore incorporate more sophisticated materials for the cartilage, such as biphasic properties, 1 , 3 , 10 , 33 and more parameters to represent the shape and thickness of the cartilage, 5 , 7 , 25 in order to achieve results more in line with the in vitro and in vivo performance.…”

A computational algorithm to simulate disorganization of collagen network in injured articular cartilage

“…Computational simulations have also shown that fluid phase can support around 80% of the cartilage load during and immediately after the load application (Li et al 2014;Quiroga et al 2017). If the load experienced by cartilage increases (e.g.…”

Unilateral total hip replacement patients with symptomatic leg length inequality have abnormal hip biomechanics during walking

“…Gait alterations were also found for the non-operated limbs of the LLI patients, with reduced peak loads and increased mid-stance joint force. As the properties and strength of the joint cartilage tend to adapt to regular level of stress ( Arokoski et al, 1999 ), the less dynamic joint load with reduced magnitude may, in the long term, alter the ultrastructure of the cartilage on the non-operated healthy hips for the LLI patients, potentially leaving healthy hips more vulnerable to insults involving sudden high loads ( Li et al, 2014a, 2014c; Swann and Seedhom, 1993 ).…”