Artefact-reduced kinematics measurement using a geometric finger model with mixture-prior particle filtering.

It is challenging to measure the finger's kinematics of underlying bones in vivo. This paper presents a new method of finger kinematics measurement, using a geometric finger model and several markers deliberately stuck on skin surface. Using a multiple-view camera system, the optimal motion parameters of finger model were estimated using the proposed mixture-prior particle filtering. This prior, consisting of model and marker information, avoids generating improper particles for achieving near real-time performance. This method was validated using a planar fluoroscopy system that worked simultaneously with photographic system. Ten male subjects with asymptomatic hands were investigated in experiments. The results showed that the kinematic parameters could be estimated more accurately by the proposed method than by using only markers. There was 20-40% reduction in skin artefacts achieved for finger flexion/extension. Thus, this profile system can be developed as a tool of reliable kinematics measurement with good applicability for hand rehabilitation.

Functional workspace for precision manipulation between thumb and fingers in normal hands.

Prehensile functions of hand are based on thumb-finger relationships which are regarded as an essential element in various manipulations of our daily living activities. Although the maximal workspace provides clinicians a way to comprehend the ranges of digital movements, little is known about the "functional workspace" based on thumb-finger relationships. This study defines the functional workspace of the precision thumb-finger grasp as the range of all possible positions in which thumb-tip and each fingertip can simultaneously contact each other. We present a quantitative method for measuring the functional workspace of the human hand. The maximal motion trajectories of thumb-tip and fingertips of twenty subjects were recorded using a video-capture system. The functional workspace of the precision manipulation was calculated via numerical methods based on the maximal workspaces obtained of the thumb-tip and fingertip motions. The ratios of the functional workspace with respect to the maximal workspace of the index, middle, ring and little fingers were calculated as 33.7%, 27.1%, 23.5% and 19.1%, respectively. Although the present approach is still a descriptive work which might require more validations or evidences to justify, the results obtained may become normal standards for practical use in objective handicapped authentications, insurance claims, and rehabilitation programs as well as criteria for ergonomic design considerations in the near future.

Reliable model-based kinematics analysis system for articulated fingers.

the kinematical measurement is regarded as the major indicator of the kinetic functions. In this study, we focused on developing a novel measurement method for kinematics of articulated finger in motion by using biomechanical model prediction and real-time video-based image analysis technique. In contrast to the marker-based system, the proposed 3D model provides more information, appearing on multiple projected 2D images, to estimate more reliable finger kinematics. The proposed method is compact, fast, and can be operated with X-ray fluoroscopy simultaneously. It means that the system provides the capability of synchronous validation between motion video and X-ray fluoroscopy. The proposed system was implemented on a personal computer and can be a new tool in diagnosis and rehabilitation for hand diseases.