Figure 1.
The demonstration of the human shank, the tibia posterior bending angle and torsion angle.
A: anatomy of human shank. B: the demonstration of the posterior bending of the proximal tibia. αpos indicates the posterior bending angle. C: tibia torsion deformation. βtor indicates the internal torsion angle whist the tibia is twisted.
Figure 2.
Illustration of the surgical details and the application of the OST approach in this study.
A) The optical motion capture system with 8 high resolution cameras to track the retro-reflective markers affixed into tibial cortex, as well as two of the ten cameras for full body motion capturing; B) Implanted bone screws in the tibial cortex; C) Marker clusters were affixed to the endings of the bone screws; D) Cross-sectional pQCT image. The black arrow indicates the hole left behind after removal of the bone screw. OST: optical segment tracking.
Figure 3.
Illustration of the tibia segment deformation (example during the stance phase of an overground gait cycle).
Solid black line: AP bending angle of the proximal tibia with respect to the distal tibia. Dashed red line: torsion angle, dotted green line: ML bending angle, dash-dot blue line: vertical ground reaction force. Posp2p refers to the peak-to-peak AP bending angle during the stance phase of the gait cycle. Medp2p refers to the peak-to-peak ML bending angle of the proximal tibia. Torsionp2p refers to the peak-to-peak torsion angle. AP: antero-posterior, ML: medio-lateral. Pos: posterior, Med: medial, p2p: peak-to-peak.
Figure 4.
Illustration of individual tibia segment deformation during overground walking in relation to walking speed.
The AP bending (A), torsion (B) and ML bending angle (C) indicate the extent of AP bending, external torsion and ML bending of the proximal tibia with respect to the distal tibia, respectively. The regression lines were given only when correlation between deformation angle and the walking speed was significant. It can be appreciated from these data that a high correlation exists between overground speed and bone deformation. This is despite the fact that locomotor patterns will contain elements that will not scale linearly with speed, which may underline the validity of the bone deformation measurements. AP: antero-posterior, ML: medio-lateral.
Figure 5.
The relationship between the tibia segment deformation angles and the VGRF or VFM during walking.
A: AP bending angles under different VGRF (the first peak value) during the first half stance phase of the gait cycle. B: Torsion angles under different VGRF (the second peak value) during the second half stance phase of the gait cycle. C: Torsion angles under different VFM during the second half stance phase of the gait cycle. The regression lines are displayed only where correlations between tibia deformation angles and the walking speed were significant. AP: antero-posterior, ML: medio-lateral. VGRF: vertical ground reaction force, VFM: vertical free moment.
Figure 6.
Tibia segment deformation angles during walking and running on a treadmill at different speed.
A: tibia AP bending angles at different speed of walking and running. B: tibia torsion angle. C: tibia ML bending angle. *: p<0.05; ***: p<0.001. AP: antero-posterior, ML: medio-lateral.
Table 1.
Least-squares linear regression statistics for tibia bending angles versus walking speed.
Table 2.
Nonparametric statistical analysis for tibia bending angles versus walking speed.
Table 3.
Least-squares linear regression statistics for tibia deformation angles versus VGRF and VFM.
Table 4.
Nonparametric statistical analysis for tibia bending angles versus VGRF and VFM.
Table 5.
The variation across the walking and running cycles was assessed with the standard deviation (SD) of the deformation angles.
Figure 7.
The recording error analysis of the OST approach.
A: the deformation angle deviation αerror assumed from the absolute error of 21/2 * 1.8 = 2.55 µm for both ends of the markers in the marker cluster. Bold black line referred to the plane determined by three markers in the marker cluster. 25 mm indicated the maximum distance between the markers in one marker cluster. α refers to the angle between the marker clusters. B: the potential marker displacement (d) due to the vibration induced by the acceleration force (F) of the screw/cluster structure. The bold black line refers to the bone screw. The red spot indicates the position of the plane determined by the markers in this cluster. 26.6 mm indicates the distance between the plane determined by three markers in one marker cluster and the bone surface. OST: optical segment tracking.