1. EFFECTS OF Q-ANGLE AND TIBIAL SLOPE ON ANTERIOR CRUCIATE LIGAMENT STRAIN: A FINITE ELEMENT STUDY
1A Amerinatanzi, M Ingels, J Kinn, R Summers, E Nyman, A Kiapour, 2AM Kiapour, 3TE Hewett, 1V Goel
1 Engineering Center for Orthopaedic Research Excellence (ECORE), The University of Toledo, Toledo, OH, USA
2 Sports Medicine Research Laboratory, Dept of Orthopaedics, Boston Children's, Harvard Medical School, Boston, MA, USA
3 Mayo Biomechanics Laboratories & Mayo Clinic Sports Medicine, Mayo Clinic, Rochester, MN, USA
Hello everybody.
My name is Amir and I am pleased to present our current work in the knee area for you.

2. Background ~200,000+ ACL injuries per year (e.g., Soccer, Basketball)
~70% of ACL injuries result from a non-contact mechanism [1]
ACL Injury
ACL injury in football
Picture 1.
Picture 2.
Picture 3.
Picture 4.
An ACL injury mechanism during jumping
ACL injury in basketball

3. Why use Finite Element Technique?
Can assign different material properties
Realistic morphology
Kinematics, stresses, and strains
Parametric studies
Difficult to assess these parameters in-vitro and in vivo
However, FE models must be experimentally validated.
Extensive application and use. It applies to all physical problems in BVP or structural and solid mechanics.
The material properties in adjacent elements do not have to be the same. This allows application to composite materials.

4. From MRI to 3D Finite Element Model
2D Anatomical planes in Mimics
3D structure in Mimics
3D FE in Abaqus

5. Experimental Validation
Validation against ACL Force & Strain
Validation against Tibiofemoral Kinematics

6. Medial and Lateral Tibial Slopes
Hashemi et al’s [2] 2D methodology was used
Measurements were made from MRI
Left Knee
Medial
Lateral
5.66°
7.48°
The more modern method for calculating tibial slopes is presented by Hashemi’s work, which is shown here
2D tibial slope measurement method [2]

7. Q-Angle Measurement Q-Angle Left Knee
2D calculation from MRIs using Ramappa et al’s method [3]
Left Knee
Q-Angle
11.32°
2D Q-Angle measurement

8. Original Model vs. 5° Increase in Tibial Slope
5° increase in posterior-inferior lateral tibial slope
Differences in tibial plateau on lateral side
Original Model

9. Original Model vs. ± 5° change in Q-angle
11.32° +5°
Original Q-angle (11.32°)
11.32° -5°

10. Case Analyzed in FE:
15° flexion N Anterior Shear N Compression
FE Results

11. Results: Change in Q-Angle (Left Knee)

12. Results: Change in Tibial Slope (Left Knee)

13. Discussion Clinical Relevance 36% increase in ACL strain
Steeper Post. Lateral Tibial Slope % increase in tibia rotation
16x increase in anterior tibial displacement
±5° change in Q-Angle  No change in ACL strain
Supports sex-based increase in ACL injury observed clinically [4,5]
The variation in ACL strain and tibial kinematics found in the present study could be important considerations during the assessment of knee injury risk.
Clinical Relevance

14. Acknowledgements Marcel Ingels Joshua Kinn Rodney Summers
Dr. Edward Nyman, Jr.
Dr. Timothy E. Hewett
Dr. Vijay K. Goel
Work supported in part by the National Institutes of Health (R01 AR TEH)

15. References
Hashemi, Javad, et al. "The geometry of the tibial plateau and its influence on the biomechanics of the tibiofemoral joint." The Journal of Bone & Joint Surgery 90.12 (2008):
Ramappa, Arun J., et al. "The effects of medialization and anteromedialization of the tibial tubercle on patellofemoral mechanics and kinematics." The American journal of sports medicine 34.5 (2006):
Webb, Justin M., et al. "Posterior tibial slope and further anterior cruciate ligament injuries in the anterior cruciate ligament–reconstructed patient." The American journal of sports medicine (2013):
Feucht, Matthias J., et al. "The role of the tibial slope in sustaining and treating anterior cruciate ligament injuries." Knee surgery, sports traumatology, arthroscopy 21.1 (2013):

16. Thank You