Abstract
Leg Length Discrepancy (LLD) causes a shift of the Center of Mass (CoM) of the human body, as well as an asymmetry in load distribution on the lower extremities. Existing LLD evaluation methods do not take into account this shift in the human body’s CoM. In this paper, a methodology and mechatronic system for the Evaluation and Compensation of LLD for Human Body Balancing are described. The human body’s CoM is measured with two force plates located on two parallel manipulators. Since persons with LLD experience a shift in their CoM, by raising the force plate that is under the shorter leg, the human body can be balanced. For this purpose, the Human Body Balancing Algorithm (HBBA) was proposed and developed. By running the HBBA, the height difference between the force plates under the left and right leg can be measured, which then represents the LLD evaluation. Based on this evaluation, it is possible to design and make a shoe insole which compensates the influence of LLD with the goal of equalizing the load on the legs. A virtual mathematical model of the system was created and the simulation results of the HBBA are presented. The mechatronic system, developed and used to conduct experiments and measurements, is described in detail.
Highlights
Anisomelia or limb length discrepancy is an orthopedic condition involving significant inequality between paired limbs
Since the Leg Length Discrepancy (LLD) evaluation is affected by the posture of the human body during the compensation of LLD, we propose a vision system consisting of two cameras and 15 markers placed on predefined anatomical points of the human body to monitor the posture and further help the clinician determine the patient’s status
To test the new LLD evaluation and compensation methodology using the Human Body Balancing Algorithm (HBBA), a virtual simulation model was made in MATLAB/Simulink®, as shown in Figure 9
Summary
Anisomelia or limb length discrepancy is an orthopedic condition involving significant inequality between paired limbs. Inequality between lower extremities is known as Leg Length Discrepancy (LLD). If the LLD amounts to over 20 mm, it is considered to be significant, and what is concerning is that this condition occurs in 0.1% of the world’s population [2]. LLD is classified as structural or functional. Structural or anatomical LLD is defined as a difference in leg length caused by unequal bone structure. Functional or apparent LLD is defined as a mechanical change in the lower extremities, such as varus and valgus deformities of knees and feet, as well as scoliosis of the spine [7]. Even though our system allows for detection of functional LLD, in this study, we focused on anatomical LLD and prepared the system for clinical trials on this particular problem
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