Long term analysis of kinematic pattern during a repetitive work task using upper limbs

Abstract

the tibial plateau, were chosen to calculate the contact point (CP) as the barycentre of the selected femoral points (in the transversal plane). Finally, the anterior–posterior (AP) location of the medial and the lateral CP was estimated for each frame of the step up/down (SUD) and the chair rising/sitting (CRS) motor tasks. Results: The global behaviour of the AP translations versus the flexion–extension were similar for both SUD and CRS motor tasks, little differences were recognized between the lateral and the medial sides. In general, the largest posterior translation occurred in the first 20–30 ◦ of flexion in the lateral side, and in the first 10–15 ◦ of flexion in the medial one. Then, the CP moved slightly anteriorly. At intermediate angles of the tasks, an additional little posterior translation was observed. During the SUD (from 0 ◦ to 70 ◦ of flexion), the lateral CP moved posteriorly of 9.3 ± 1.9 mm and of 7.6 ± 3.7 mm, for the extension and the flexion movements respectively. The medial point moved posteriorly of 16.3 ± 4.3 mm and of 16.4 ± 3.2 mm, for the extension and the flexion movements respectively. During the CRS (from 0◦ to 90◦ of flexion), the lateral CP moved posteriorly of 7.0 ± 1.0 mm and of 8.1 ± 0.4 mm, for the extension and the flexion movements respectively. The medial point moved posteriorly of 13.1 ± 2.8 mm and of 9.2 ± 1.9 mm, for the extension and the flexion movements respectively. Discussion: The largest AP translation of the CP, which occurred at low of flexion angles, is due to the physiological rolling movement of the femur with respect to the tibial plateaus. At larger flexion angles, the sliding movement of the femur, guided by the cruciate ligaments and the articular surfaces [3], produced smaller AP translation of the CP. The higher variability obtained during the SUP with respect to the CRS can be explained by the use of one versus two legs and by higher inertial components which can occur in the SUP motor task. In conclusion, the devised model can provide a clinically important evaluation of the articular contact of the tibio-femoral joint during the execution of daily activities in living subjects.