Test Cases¶
The individual experimental laxity tests that were performed are referred to as a “test case”. Not all of the test cases were used for model calibration. This section describes which test cases were used for model calibration, and which test cases were used to evaluate the results of the model (referred to as “Confirmation” test cases).
Calibration Test Cases¶
The calibration load cases are the the experimental tests that are simulated as part of the objective function evaluation. These load cases are a subset of the available data. The objective function includes the maximum applied loads during the anterior-posterior drawer and varus-valgus tests at \(0^\circ\) and \(90^\circ\) flexion.
Confirmation Test Cases¶
The experimental test cases that were excluded from the optimization are used to evaluate the estimated ligament properties. These tests include the anterior-posterior drawer and varus-valgus tests at \(30^\circ\) and \(60^\circ\) flexion, and the internal-external rotation tests at \(0^\circ\), \(30^\circ\), \(60^\circ\) and \(90^\circ\) flexion. This evaluation will use the calibrated model to simulate these test cases and measure the error between the calibrated model and experimentally measured kinematics.
Note
Additional test cases and/or test points will be added to the set of calibration test cases if (1) the optimization does not converge or (2) there is excessive error between the calibrated model and experimentally measured kinematics for the calibration and confirmation test cases. Excessive error is defined as kinematic RMS errors that are equal to or greater than \(4^\circ\) for rotations and 4 mm for translations, as would be roughly consistent with recent modeling efforts [EKH+15] and [HCA+16].
[EKH+15] | Joseph A. Ewing, Michelle K. Kaufman, Erin E. Hutter, Jeffrey F. Granger, Matthew D. Beal, Stephen J. Piazza, and Robert A. Siston. Estimating patient-specific soft-tissue properties in a TKA knee. Journal of Orthopaedic Research, pages n/a–n/a, September 2015. URL: http://onlinelibrary.wiley.com/doi/10.1002/jor.23032/abstract, doi:10.1002/jor.23032. |
[HCA+16] | Michael D. Harris, Adam J. Cyr, Azhar A. Ali, Clare K. Fitzpatrick, Paul J. Rullkoetter, Lorin P. Maletsky, and Kevin B. Shelburne. A Combined Experimental and Computational Approach to Subject-Specific Analysis of Knee Joint Laxity. Journal of Biomechanical Engineering, 138(8):081004–081004, June 2016. URL: http://dx.doi.org/10.1115/1.4033882, doi:10.1115/1.4033882. |