Optimizing Marker Implantation for Three-Dimensional Kinematic Tracking in X-Ray Videos

For a detailed analysis of complex movements, such as disturbed locomotion, a combination of common approaches is helpful (calculation of 3D kinematics, measurements of myoelectrical activities, and ground reaction forces). The use of internal markers increased the accuracy of motion capturing and allowed the calculation of kinematics in 3D space, even long-axis rotation. Two implantation methods were designed and compared concerning their accuracy. Therefore, a double set of tantalum beads was implanted into the right forelimb of rats (test method versus glued reference). Our results showed that injecting the beads (1) via needle was the fastest method but caused considerable relative movements to the bones, which affected the angular 3D calculation (Ø root-mean-square (RMS) 3.4-31.6 deg), especially in the humerus. However, (2) embedding the internal markers into the muscles close to the periosteum enabled comparable results to the glued reference (Ø RMS 1.3-7.5 deg), while the surgery became easier and faster.