Difference between revisions of "Additional Data"
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In addition to the in vivo measured joint loads, further kinetic and kinematic data are published at OrthoLoad.com. Short descriptions of these additional measures are given in this chapter. | In addition to the in vivo measured joint loads, further kinetic and kinematic data are published at OrthoLoad.com. Short descriptions of these additional measures are given in this chapter. | ||
Latest revision as of 15:56, 17 February 2017
In addition to the in vivo measured joint loads, further kinetic and kinematic data are published at OrthoLoad.com. Short descriptions of these additional measures are given in this chapter.
Contents
Instrumented Crutches
Fcont - Contralateral Crutch Force
Fipsi - Ipsilateral Crutch Force
2kN Force Transducer (KM 30z)
| Technical data: | |
| Bridge resistance: | 350 Ohm |
| Linearity error: | 0.1% |
| Hysteresis error: | 0.1% |
| Measurement amplifier | BA660 |
| Sensitivity: | 0.5mV/V |
| Bridge Voltage: | 5V |
| Output Voltage: | +/- 5V |
| Linearity error: | 0.02% |
| fc output filter: | 250Hz |
Bending Moment
The resultant bending moment Mbend , acts in the middle of the femoral neck and perpendicular to the neck axis, and is calculated with the following formula:
with 
The forces (Fx’, Fy’, Fz’) and moments (Mx’, My’, Mz’) are measured in the “implant coordinate system” x’, y’, z’ centered in the middle of the implant head. The force component Fx’ acts laterally, Fy’ anteriorly, and –Fz’ distally along the femur axis. The measured moment components Mx’, My’, and Mz’ turn right around the x’, y’, and z’ axes. N is the distance between the head center and the middle of the femoral neck and is equal to ½ L.
Mtne acts around the neck axis of the femur and represents the torsional loading of the neck. It is calculated by α = -45° rotation of the "bone coordinate system” around the y-axis.
Ground reaction forces
Ground reaction forces were measured using two 6 degrees of freedom force plates (AMTI, Watertown, MA). The coordinate system is a right-handed system.
Raw data:
| VARIABLE | DESCRIPTION | UNITS | SAMPLE RATE |
|---|---|---|---|
| Fx,y,z 1/2 | Ground reaction forces, forceplate 1 and 2 | N | 960 Hz |
| Mx,y,z 1/2 | Moments relative to the original forceplate coordinate system, forceplate 1 and 2 | Nmm | 960 Hz |
For the calculation of the center of pressure the following offsets were used. The true origins of the coordinate systems are located below the top surfaces, with a distance (zo).
Processed data
(see Comprehensive Data Sample):
| VARIABLE | DESCRIPTION | UNITS | SAMPLE RATE |
|---|---|---|---|
| Fgrx,y,zi | Ground reaction forces, ipsilateral leg | N | 90-110 Hz |
| COP_x,yi | Center of pressure, relative to forceplate center, ipsilateral leg | mm | 90-110 Hz |
| Tz_i | Torque around z-axis at CoP, ipsilateral leg | Nm | 90-110 Hz |
grf2f.eof data:
(Downsampled Ground Reaction Forces)
| VARIABLE | DESCRIPTION | UNITS | SAMPLE RATE |
|---|---|---|---|
| Fgrxi,yi,zi | Ground reaction forces, ipsilateral leg | N | 90-110 Hz |
| Fgrxc,yc,zc | Ground reaction forces, contralateral leg | N | 90-110 Hz |
| F | Resultant joint contact force (implant) | N | 90-110 Hz |
