Technical note: sensitivity analysis of the SCoRE and SARA methods for determining rotational axes during tibiofemoral movements using optical motion capture

Abstract

The first aim was to report the sensitivity of calculated tibiofemoral movements for the choice of placement of the set of femoral markers. The second aim was to report the influence of accuracy of the motion captured positions of the markers on the calculated tibiofemoral movements. Methods: Tibiofemoral kinematics during single leg hops for distance were calculated. For the first aim, an experiment was conducted in which four different setups of the femoral markers were used to calculated tibiofemoral movements. For the second aim, an experiment was conducted in which all raw marker positions were mathematically moved independently with the known Vicon position error with a distance and in a random direction in each frame, repeated a hundred times. Each time, the tibiofemoral movements were calculated. Results: The first experiment yields that the standard deviation of the calculated anterior tibia translation between marker setups was 0.88 mm and the standard deviation of the external tibia rotation between marker setups was 0.76 degrees. The second experiment yields that the standard deviation was 0.76 mm for anterior tibia translation and 0.38 degrees for external tibia rotation. Conclusion: A combined standard deviation of both experiments revealed that transients in anterior tibia translation less than 2.32 mm and external tibia rotations less than 1.70 degrees should be taken with caution. These results are 19.42% of the range of the anterior tibia translation and 13.51% of the rotation range during the jump task. The marker setup should be chosen carefully.

Copers and Noncopers Use Different Landing Techniques to Limit Anterior Tibial Translation After Anterior Cruciate Ligament Reconstruction

“…In another experiment in which we identified the sensitivity of the method used to quantify ATTd on marker placement (wobbling masses) and the Vicon position error, we found an error in the measured ATTd of 2.32 mm. 25 All differences between patients on 1 SLHD of less than 2.32 mm should be interpreted with caution. This limitation is used to interpret the results of the current study.…”

“…Thereby, previous studies showed comparable ATTd ranges with our study. 5 , 23 , 25 , 28 A third limitation is the method of normalization of muscle activity. We chose to normalize muscle activity to the percentage of the mean muscle activity during the SLHD.…”

“…The coefficient of variation for this procedure for determining ATTd across 16 healthy knees was 5.2% ± 1.2%, and excellent reproducibility was observed (intraclass correlation coefficient [ICC] (3,1) = 0.92). 14 Moreover, Keizer and Otten 25 showed that ATTd >2.32 mm is reliable in terms of wobbling masses and the Vicon position error. Previous studies have found a smaller variability with the KT-1000 arthrometer compared with other devices to measure ATTp.…”

“…After attaching the markers, calibration frames of a flexion-extension movement and a star-arc movement, as prescribed by the manufacturer’s instructions, were taken to be able to identify the hip and knee joint centers and axis of rotation of the knees. 16 , 17 See Keizer and Otten 25 for details on the entire procedure.…”

“…For the quantification of ATTd and knee angles, 2 coordinate systems were reconstructed in the tested knee using a customized MATLAB script based on the method of Boeth et al 14 One system was reconstructed in the femoral segment (parent system) and 1 in the tibial segment (child system). See Keizer and Otten 25 for the details of this procedure. The motion of each coordinate system was consistent with the movement of the respective segment.…”