Structural Modeling of the Human Musculoskeletal System for Clinical Treatment by Applying Joint-Connected Multibody Dynamics and System Approach

Abstract

The objective of this paper is to establish a concise structural model of the human musculoskeletal system (HMS) that can be used to clinically treat malfunctions or distortions of the human body. This model must be uncomplicated for therapists to identify the problematic areas of the human body with adequate visualization while maintaining a theoretical thoroughness in mechanics. To achieve this objective, a system theory approach called the Interpretive Structural Modeling (ISM) has been applied to bridge multi-body dynamics and clinical observations. From a mechanical engineering viewpoint, this HMS system can be treated as a collection of joint connected 15 rigid bodies in a topological tree configuration with 35 Degrees-of-Freedom (DOF). Alternatively, from a clinical viewpoint, the functioning of the joints is a major concern since most malfunctions or distortions take place around the joints. Based on 20 years of accumulated clinical observation data, we have discovered that all HMS movements can be constructed by a combination of 35 fundamental motion elements, all having a certain degree of interaction with each other. By applying the ISM for a matrix representation of the HMS system, we have obtained the following results: 1) The association between the rotation of the joints and the fundamental motion elements is represented by a square matrix of dimension N, where N is twice of the DOF 2) The determinant of this matrix, corresponding to the N-square matrix in SE terminology, gives an evaluation criteria in selecting the fundamental elements; 3) Application of the ISM reveals a distinction between an active motion element with intention versus an associated motion element that is induced by another motion element(s). In addition, the ISM yields a tiered structure of the fundamental motion elements according to the degree of activeness; and 4) most important, an overall investigation of the matrix characteristics gives a means to identify imbalances or distortions within the HMS. With the help of a motion diagram for the purpose of visualization, this research can eventually be applied to clinical observations whereby an automated identification of malfunctioning parts can be achieved with computer software. The above stated results will contribute to a holistic and non-invasive approach for medical care and rehabilitation.