I am very new to Anybody modeling system and intend to fully exploit the capabilities of this software to achieve some of the objectives of my research project. My area of research is in [COLOR=black]non-contact ACL injury during single leg landing. My intent is first to conduct single leg landing trials in a gait lab to simualte “close to injury” situations. For these experiment Mocap, force plate and EMG data will be collected. From here I will then endeavor to replicate this motion in a virtual environment using an Anybody model. Given ACL injury cannot be replicated in a lab environment for obvious ethical reasons, the goal is to use a validated musculoskeletal model from Anybody to find the body kinematics and external forces to cause injury during single leg landing. Non-contact ACL injury entails numerous forces, factors and extreme conditions that happen simulataneously to cause injury. Given this I am not sure if even with a validated full body musculoskeletal model developed using Anybody I will be able to find the kinematics to cause injury. Moreover, I am not sure if Anybody can simulatenously consider numerous parameters, numerous constraints and perhaps numerous objectives in a single problem as is the case in non-contact ACL injury. For this reason I may use an AI method (specifically a genetic algorithm) coded in Matlab to call up Anybody to help find the kinematics and external forces to cause non-contact ACL injury during single leg landing. The data from experiments I see using as initial conditions. I am not sure if all this is at all possible with Anybody. [/COLOR]
Reviewing various threads I see little work on ACL injury. The work of Maja Rose is the only work that I can find. If there are any other work out there related to mine kindly let me know. For Maja Rose work does anyone know how she uses a musculoskeletal model to determine ACL strain. Moreover, if anyone in the anybody community is working on non-contact ACL injury I would be grateful if we can dialogue. Incidentially I just noticed someone looking at studying jump landing using AMS. This I must follow.
I think the reason for lack of ACL work with AnyBody is that the knee model in the repository is a simple hinge and therefore does not directly distribute the loads on the various structures of the knee. The problem here is that the displacement in the knee probably to some extent is dependent on force and this is at odds with AnyBody’s inverse dynamics approach. However, I know that a number of research groups are currently working with more detailed knee models.
With the current hinge knee model, the trick is to define the reaction forces in the coordinate system of the tibial plateau. This will separate the reaction forces into one component perpendicular to the plateau and to reactions parallel to the plateau. The anterior/posterior reaction component will be carried by the cruciate ligament in combination with the miniscii, so this reaction becomes an indirect measure of ACL load.
Thanks Dr. Rasmussen. Some have used anterior shear force as a metric to quantify loading see at the ACL. Others have simply assume anterior shear force is equal to the force seen at the ACL. The limitation with this assumption is the angle of the ACL during various movement is not taken into account. Far as I know this information is not readily available.
I will like to study other metrics as well such as GRF, quad loading, hamstings loading, gastroc loading, foot position on landing etc. to investigate its effect on ACL. Given musculoskeltal model does not include the ligaments forces then a way around this problem is perhaps to look at other known metrics that there is some concensus in the literature. For example valgus moment or high quad mucle forces during a jump is know to place the ACL an increased risk of injury. Then if during our landing studies we see as height of jump increases then knee valgus moment and quad loading increases for many trials and using many subjects we can make certain deductions on risk to ACL injury.
It is actually possible in AnyBody to switch off the reaction force of the hinge joint and define an ACL that inserts under the correct angle on the tibia and let that carry the shear load. However, in practice all the shear load is hardly carried by the ACL; there are other elastic structures such as the miniscus, to in reality there is probably some sharing of the load going on and modelling that part correctly requires a more detailed model.
Thanks Dr. Rasmussen. Great to see we may be able to incorporate the ligament perhaps via some sort of a muscle model. Yes a more detailed model will be required if we start looking into the soft tissues and their contribution. There are many limitations of FEMs and to date only one group I know that has looked at the entire lower extremity to study knee behaviour. For the most part many FEM studies in the literature focus on the knee joint only, do not include muscles and very few even use these models to study ACL injuries. A combined approach fusing data from different study approaches may be best for ACL injury studies.