Hip Reference Frame

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1

Hello

After analysis in the gait laboratory, we put our data through Visual3D where we found unusually high hip flexion angles. For this reason, we decieded not to use the pelvic reference frame as the pelvis markers may have been misplaced due to using obese patients. Instead we have used the laboratory reference frame and the results in Visual3D look much better.

If I put the .C3D file through Anybody, I get the same results as I did in Visual3D in terms of hip motions with the hip flexing too much. I believe that you are using the pelvic reference frame to calculate hip motion. Is it possible to calculate hip motion with respect to the global/laboratory reference frame in Anybody? If so, could someone please explain to me how this would be done

Thank you in advance

Ammar

2

Dear Ammar,

Yes it is possible.

The only thing that you should do is to define your own kinematic measures.
In this case you can define your own AnyKinRotational class object between the global(laboratory) reference frame and the other reference frame in either pelvis or thigh as you want.

And you can read that value after the kinematics analysis.

Best regards,
Moonki

3

Hi

I have added the following code to the GaitLowerExtremity model

AnyKinRotational referencechange =
{
Type = RotAxesAngles;
Axis1 = z;
Axis2 = y;
Axis3 = x;
//AngVelOnOff = Off;
//AngVelGlobal = Off;
AnyRefFrame & Global = Main.Studies.HumanModel.BodyModel.Trunk.SegmentsLumbar.PelvisSeg;
AnyRefFrame & Thigh = Main.Studies.HumanModel.BodyModel.Right.Leg.Seg.Thigh;
};

I however do not see any change in results, I think I may have misdefined the Global reference frame.

Any help appreciated

4

Hi,

There is an easy way to measure the rotation w.r.t. the global coordinate system.

AnyKinRotational referencechange1 = 
  {
    Type = RotAxesAngles;
    Axis1 = z;
    Axis2 = y;
    Axis3 = x;
    //AngVelOnOff = Off;
    //AngVelGlobal = Off;
    AnyRefFrame & Global = Main.Studies.HumanModel.BodyModel.Trunk.SegmentsLumbar.PelvisSeg;
};

AnyKinRotational referencechange2 = 
  {
    Type = RotAxesAngles;
    Axis1 = z;
    Axis2 = y;
    Axis3 = x;
    //AngVelOnOff = Off;
    //AngVelGlobal = Off;
    AnyRefFrame & Thigh = Main.Studies.HumanModel.BodyModel.Right.Leg.Seg.Thigh;
  };

Then each AnyKinRotational will display the rotation angles of the corresponding AnyRefNode object.

Best regards,
Moonki