A model-based study of passive joint properties on muscle effort during static stance

Does Intensive Soccer Playing During the Growth Period Lead to Leg Length Discrepancies?

Leg length discrepancies (LLD) are a common reason for podiatry consultations and can affect up to 90% of the overall population. Furthermore, it is widely recognized that intensive participation in certain sports can alter bone development. The aim of this study is to explore any possible relation between playing soccer and the appearance or evolution of LLD, by means of a retrospective study based on the analysis of case reports of patients followed for foot or plantar troubles. Case reports were selected in the archives of a podiatric clinic for the period between 2002 and 2016 among patients who declared regular to intensive soccer playing, aged 13 years or more. LLD was detected in the vast majority of cases (95 cases out of 104). Pearson correlation coefficients were computed and revealed a strong correlation between the laterality of the kicking limb and that of the shorter leg. The shorter limb was on the side of the kicking leg in 96% of the cases when considering the players who began practice before the age of 13, and only 53% of the cases for others. Intensive soccer playing at a young age may encourage the appearance and evolution of a real LLD.

Application and evaluation of biomechanical models and scores for the planning of total hip arthroplasty

Intimate knowledge of the biomechanics of a given individual hip joint provides a potential advantage during the planning of total hip arthroplasty, and would thus have a positive influence over the outcome of such an intervention. In current clinical practise, the surgical planning is based solely on the status of the individual hip and its radiographic appearance. However, additional information could be gathered from the radiography to be used as input data for biomechanical models aimed at calculating the resultant force FR within the hip joint.

An investigation of the biomechanical models by Pauwels, Debrunner and Iglič was performed, where the magnitude of FR calculated by the models showed a favourable comparison to the in-vivo data from instrumented prostheses by Bergmann. The Blumentritt model returned abnormally high results. The computational results showed large variations for FR orientation, which tends to depend more on the model used than on patient-specific parameters.

Furthermore, a discrepancy was found between the data gathered from instrumented prostheses and the Standing Human Model within the ‘AnyBody Modeling System™’ software by AnyBody Tech. Additionally, the variations in inter-rater and intra-rater errors made while localizing radiographic landmarks were analysed with respect to their influence on Babisch-Layher-Blumentritt (BLB)-scoring using the Blumentritt hip model.

Influence of joint models on lower-limb musculo-tendon forces and three-dimensional joint reaction forces during gait

Several three-dimensional (3D) lower-limb musculo-skeletal models have been developed for gait analysis and different hip, knee and ankle joint models have been considered in the literature. Conversely to the influence of the musculo-tendon geometry, the influence of the joint models - i.e. number of degrees of freedom and passive joint moments - on the estimated musculo-tendon forces and 3D joint reaction forces has not been extensively examined.

In this paper musculo-tendon forces and 3D joint reaction forces have been estimated for one subject and one gait cycle with nine variations of a musculoskeletal model and outputs have been compared to measured electromyographic signals and knee joint contact forces. The model outputs are generally in line with the measured signals. However, the 3D joint reaction forces were higher than published values and the contact forces measured for the subject. The results of this study show that, with more degrees of freedom in the model, the musculo-tendon forces and the 3D joint reaction forces tend to increase but with some redistribution between the muscles. In addition, when taking into account passive joint moments, the 3D joint reaction forces tend to decrease during the stance phase and increase during the swing phase.

Although further investigations are needed, a five-degree-of-freedom lower-limb musculo-skeletal model with some angle-dependent joint coupling and stiffness seems to provide satisfactory musculo-tendon forces and 3D joint reaction forces.

Modeling of the passive mechanical properties of the musculo-articular complex: acute effects of cyclic and static stretching

The primary aim of this study was to implement a rheological model of the mechanical behavior of the passive musculo-articular complex (MAC). The second objective was to adapt this model to simulate changes in the passive MAC's mechanical properties induced by passive stretching protocols commonly performed in sport and rehabilitation programs. Nine healthy subjects performed passive ankle dorsi-flexion and plantar-flexion cycles at different velocities (from 0.035 to 2.09 rads(-1)) on an isokinetic dynamometer. This procedure enabled the articular angle to be controlled and the passive torque developed by the MAC in resistance to stretch to be measured. Our rheological model, dependent on nine parameters, was composed of two non-linear (exponential) springs for both plantar- and dorsi-flexion, a linear viscoelastic component and a solid friction component. The model was implemented with the Simulink software package, and the nine parameters were identified, for each subject, by minimizing the square-difference between experimental torque-angle relationships and modeled curves. This model is in good agreement with experiment, whatever the considered stretching velocity. Finally, the model was adapted to incorporate static stretching (4x2.5 min) and cyclic stretching (five loading/unloading cycles) protocols. Our results indicate that the model could be used to simulate the effects of stretching protocols by adjusting a single (different) parameter for each protocol.