Patient specific bone tracking using ultrasound for human movement analysis

Human motion analysis has numerous applications ranging from gait analysis to prosthetic manufacturing. Amongst various techniques, use of retroreflective markers placed on skin to estimate the underlying bone movement is well established. Most commonly used movement types such as flexion, abduction and circumduction often suffer from measurement errors due to displacement of markers placed on skin with respect to underlying bone. Hence, its use is limited in clinical and biomechanical applications. Here, we are elaborating the possibility of using ultrasound imaging as an ad hoc to track the movement of underlying femur bone during these movements. It is shown that the bone displacement varies significantly amongst subjects, movement type and probe placement on thigh. This will open the grounds of getting patient specific joint movements with more accuracy than motion capture alone. The approximated fitting of marker data is often useful but they are not seamlessly accurate. Previously [17] we have highlighted the use of ultrasound imaging to compensate the soft tissue error in finding functional hip joint centre through flexion movement. In this paper we have explained our methodology of extracting bone edges and tracking the underlying bone displacement using ultrasound imaging to compare how different movement types affect internal bone movements for different subjects which can be extended to be applied to other applications of human joint research.