SUBJECT SPECIFIC MUSCLE TENDON LENGTH AND MOMENT ARM QUANTIFICATION FOR MUSCLE- SKELETAL MODELING: NON-INVASIVE ESTIMATE USING DIRECT AND ULTRASOUND CALIBRATION

The determination of the length and of the line of action of muscles personalised to subject morphology is one of the most critical aspects in the development of reliable musculoskeletal models. The aim of this study is to improve the accuracy of these estimations using ultrasound images for identifying muscle insertions, origins and via points of a specific subject. One healthy young subject participated in the study. A three segment model of the subject right lower limb was obtained. Origins, insertions and via points of gastrocnemius, soleus and tibialis anterior were calibrated using manual pointing and ultrasound images and then reconstructed during a walking task. Different methods showed similar trends for muscle tendon length during motion, while absolute value varied of about 5%. Moment arm results showed between method differences of 30%-40% of medium muscle arm values, indicating how big errors can implicitly bring these inaccuracies to joint moment estimation in muscle-skeletal model predictions. Moreover variation of via point positions with movement can add errors in model estimations.