Special Issue: Musculoskeletal Models in a Clinical Perspective

After the pioneering work of Scott Delp and colleagues dated 1990 (An interactive graphics-based model of the lower extremity to study orthopaedic surgical procedures, [1]) a huge amount of work aimed at creating a virtual representation of the human movement has been completed. The increased computational power and graphics capacity of computers have been fundamental in this process. Early in 2008, a very ambitious project was launched at the European level, with the objective of modelling all of the physiological phenomena of a human being: The Virtual Physiological Human [2]. The evolution of musculoskeletal modelling can be seen as a component of that ambitious project. Musculoskeletal modelling consists of reproducing the anatomical structure and the dynamic behaviour of a human subject, or a part of it, and simulating the effects of movement and forces upon the internal components. The interest in these techniques is very wide, spanning from sports biomechanics to ergonomics and clinical applications. In these different areas, the objectives and the methods can be different, but in all cases, musculoskeletal models can provide information that could not be obtained in other ways, considering, for example, the internal forces in a joint, the tension of the ligaments and the effects of muscle contractions. This Special Issue was particularly aimed at collecting experience and points of view concerning the potential of the musculoskeletal models in clinical applications. The review paper of Killen et al. [3] makes a point on the impact that musculoskeletal models and dynamic simulation have on clinical practice and in rehabilitation in particular. The perspective paper of BJ Fregly [4] provides a vision of what the role of musculoskeletal modelling in clinics could be and the steps required to make these techniques widely available and useful. Other papers report on interesting examples of problems in which musculoskeletal models have been fundamental to answer clinical questions: the complex mechanism of swallowing [5], where the role of different muscles is very difficult to investigate in other ways; the problem of lower back pain in pregnancy [6]; the question of the effectiveness of a particular reinforcement treatment for the abductor muscles in subjects affected by hip dysplasia after total hip joint replacement [7]. One paper [8] then provides an example of how the dynamic simulation can help us to understand the role of muscles during walking and answer a typical ‘what if?’ question: what happens if the Rectus Femoris muscle increases or decreases its activity in a specific phase of the gait cycle? Two more papers lay in the original mainstream of musculoskeletal modelling applications, that is, clinical orthopaedics. One faces the technical problem of understanding the effect of changing the tibial insert thickness in the knee joint arthroplasty [9], and the other reports on the forces occurring on the knee joint ligaments and bone surfaces while walking [10]. The papers collected in this Special Issue are obviously far from covering all of the possible applications of musculoskeletal models, but they do offer a demonstration of the usefulness of the modelling approach. This is truly a fast-growing discipline that is producing an enhancement of knowledge in many different areas. Being conscious of the potential effects of this evolution, which could be in terms of the prevention of musculoskeletal damage, treatment planning, or load assessment, is fundamental for improving the quality of health care services offered to people affected by neuromusculoskeletal diseases. This Special Issue represents a contribution to the promotion of the continuous improvement and usage of this advanced methodology.