Three-dimensional rotations of human three-joint fingers: an optoelectronic measurement. Preliminary results.

Longitudinal axial rotations of phalanges during flexion motions of digits have scarcely been analyzed with current anatomical or radiological methods. Recent optoelectronic systems were developed for three-dimensional (3D) kinematic analysis of human motion. These systems have the advantages of being non-invasive and non-irradiating. The current study was based on the VICON optoelectronic system. A validation of the protocol was made among a sample of volunteers for further direct clinical applications. An experimental protocol was set up with adaptations to the requirements of finger analyses (multiple infrared markers inside small-sized capture volumes). The set-up and the protocol details are described. Kinematic studies consisted in recording the movements of the right hand of six volunteers (free from any visible pathology). Results were displayed for the joints of each three-joint finger with calculation of 3D rotations. Metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) flexion angles ranged from 78 degrees to 118 degrees, 72 degrees to 119 degrees and 9 degrees to 66 degrees respectively. Lateral angles ranged from 5 degrees to 39 degrees (MCP), 4 degrees to 39 degrees (PIP) and 4 degrees to 30 degrees (DIP). Mean longitudinal axial rotations of MCP, PIP and DIP joints ranged from 11 degrees pronation to 26 degrees supination. The index finger was in a global pronation position (five of the six specimens). The fourth and fifth fingers were in a global supination position in every case. The third finger was in a more variable global rotation (pronation in four of the six specimens). An experimental protocol using an optoelectronic system (VICON) has been developed for a kinematic analysis of three-joint finger. A global measure study should be initiated among a wider sample of adults. A database should be created with direct clinical applications. Patients' kinematic deficits could be graded either for standard movements (flexion/extension and abduction/adduction) or for longitudinal axial rotations.