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Old 06-04-2014, 03:02 PM
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bayoglur bayoglur is offline
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Join Date: Feb 2014
Posts: 26
Default Ligament lengths reference

Hi AnyBody,

I am playing with the example SpineFixationWithForceDependentKinematics model (version 1.6.1). I saw that slack lengths of these ligaments were defined in the LigamentsLumbar.any file, but never used afterwards (although the variables are seen in ligament model definitions, they were commented out as shown below,

AnyLigamentModelPol PLLT12L1 = 
      //L0 = .pl_slack_length*1.5;
      eps1 = ..epsPLL[.li];
      F1 = ..kPLL[.li]*eps1*L0;

I wonder where these numbers come from and why they were not used in the ligament models?

AnyFolder LumbarSpineLigaments = {
   AnyFloat strainratio = 0.75;
   AnyFloat mm2m = 1000;
   AnyFloat al_slack_length = 1.2;
   AnyFloat pl_slack_length = 1.2;
   AnyFloat is_slack_length = 1.2;   
   AnyFloat ss_slack_length = 1.2;   
   AnyFloat lf_slack_length = 1.2;
Secondly, for each motion segment of the lumbar spine, ligament lengths were seen in the first part of each segment. I wonder where these numbers come from? Is there any reference?

One of the entries in T12L1Ligaments.any file:

// Ligament group index
    AnyIntVar li = 0; 
    // generic ligament lengths for the standard man 
    // (need to be calibrated if scaled)    
    ALLT12L1.L0 = 8.062257748298454e-003;
    PLLT12L1.L0 = 3.793040035359760e-003;
    IST12L1.L0 = 2.083866598417453e-002;
    SST12L1.L0 = 1.627882059609978e-002;
    FlavumT12L1.L0 = 7.786036276341179e-003;
I think this information is one of the critical parts of the model, and they deserve proper references. I would be happy if anyone comments on this please.
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