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Design Innovation Papers

Combined in Vivo/in Vitro Method to Study Anteriomedial Bundle Strain in the Anterior Cruciate Ligament Using a Dynamic Knee Simulator

[+] Author and Article Information
Naveen Chandrashekar

e-mail: nchandra@uwaterloo.ca
Department of Mechanical and Mechatronics Engineering,
University of Waterloo,
Waterloo, ON, N2L 3G1, Canada

Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received December 5, 2011; final manuscript received December 18, 2012; accepted manuscript posted January 29, 2013; published online February 11, 2013. Assoc. Editor: Richard Neptune.

J Biomech Eng 135(3), 035001 (Feb 11, 2013) (8 pages) Paper No: BIO-11-1508; doi: 10.1115/1.4023520 History: Received December 05, 2011; Revised December 18, 2012; Accepted January 29, 2013

The mechanism of noncontact anterior cruciate ligament (ACL) injury is not well understood. It is partly because previous studies have been unable to relate dynamic knee muscle forces during sports activities such as landing from a jump to the strain in the ACL. We present a combined in vivo/in vitro method to relate the muscle group forces to ACL strain during jump-landing using a newly developed dynamic knee simulator. A dynamic knee simulator system was designed and developed to study the sagittal plane biomechanics of the knee. The simulator is computer controlled and uses six powerful electromechanical actuators to move a cadaver knee in the sagittal plane and to apply dynamic muscle forces at the insertion sites of the quadriceps, hamstring, and gastrocnemius muscle groups and the net moment at the hip joint. In order to demonstrate the capability of the simulator to simulate dynamic sports activities on cadaver knees, motion capture of a live subject landing from a jump on a force plate was performed. The kinematics and ground reaction force data obtained from the motion capture were input into a computer based musculoskeletal lower extremity model. From the model, the force-time profile of each muscle group across the knee during the movement was extracted, along with the motion profiles of the hip and ankle joints. This data was then programmed into the dynamic knee simulator system. Jump-landing was simulated on a cadaver knee successfully. Resulting strain in the ACL was measured using a differential variable reluctance transducer (DVRT). Our results show that the simulator has the capability to accurately simulate the dynamic sagittal plane motion and the dynamic muscle forces during jump-landing. The simulator has high repeatability. The ACL strain values agreed with the values reported in the literature. This combined in vivo/in vitro approach using this dynamic knee simulator system can be effectively used to study the relationship between sagittal plane muscle forces and ACL strain during dynamic activities.

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Figures

Grahic Jump Location
Fig. 1

A flow chart representing the inputs and outputs of in vivo, modeling, and in vitro parts of the experimental procedure

Grahic Jump Location
Fig. 2

The dynamic knee simulator system. The cadaver knee (K) is connected to the turnbuckles that are connected to surrogate hip (HI) and ankle (A) joints. The hip joint moves in the vertical direction (dark double head arrow) and the ankle moves in the horizontal direction (white double head arrow). The ankle joint also is unconstrained in the mediolateral direction (white double headed dotted arrow). Three muscle force actuators (Q, H, and G) are connected to the knee, and they apply dynamic quadriceps, hamstring, and gastrocnemius muscle forces (dark single head arrows). The hip moment actuator (HM) connected to the turnbuckle below the hip applies flexor-extensor moment. The load cells connected to the actuator rod ends are not seen in this view.

Grahic Jump Location
Fig. 3

A close-up view of the surrogate hip joint (a), muscle cable attachments on the cadaver knee (b), and the surrogate ankle joint (c) in the simulator

Grahic Jump Location
Fig. 4

The lower extremity model from AnyBody Modeling System

Grahic Jump Location
Fig. 5

The applied muscle force profiles (solid line) of quadriceps (a) and hamstring (b) muscle groups and the applied hip extensor moment (c). The input to the actuators is shown as dotted gray lines. The resulting ACL strain (dotted line) and the corresponding GRF (solid line) is also shown (d). In the x axis, −100 ms represents 100 ms before landing and 0 represents landing. The gray vertical line across the graphs shows the instance of ground contact. The data is smoothed to remove electrical and mechanical noise.

Grahic Jump Location
Fig. 7

The comparison between the net knee extensor moments in the knee derived from inverse dynamics (gray dotted line) and the grouped muscle moments calculated by the AnyBody model (dark solid line). The gray vertical line across the graph shows the instance of ground contact. The GRF (solid gray curve) is also given for comparison purposes.

Grahic Jump Location
Fig. 6

The intended (dotted line) and actual (solid line) hip and ankle motion profiles and the corresponding knee flexion angle (solid) compared to in vivo data (dotted line). In the x axis, −100 ms represents 100 ms before landing and 0 represents ground contact. The gray vertical line across the graph shows the instance of ground contact.

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