Lucie Hucke (Frankfurt a. M.; Cádiz / ES), Eva Böker (Leipzig), Dr.-med. Christian Roth (Leipzig), Prof. Dr. Maren Witt (Leipzig), Prof. Dr. Armin Huß (Frankfurt a. M.), Dr. Andreas Wittek (Frankfurt a. M.)
Abstract-Text (inkl. Referenzen und Bildunterschriften)
Repetitive stress and axial misalignment are discussed in the context of changes in adolescent articular cartilage [1, 2]. It is still unclear whether the mechanically identifiable stress zones on the joint are associated with preclinical cartilage changes.
In order to calculate the stresses in the articular surface of the knee, a finite element (FE) model of one left knee was created, containing the cartilage of the distal femur and the proximal tibia and both menisci. The bones were simplified as rigid bodies. The boundary conditions are the ground reaction forces and the respective position of the knee, which were measured over the gait cycle. The gait cycle was modelled using 10 quasi-static load cases. Independently of this, the cartilage status was determined using T2 mapping on 3T MRI.
The result of the FE simulation is the stress distribution in the joint surface over the gait cycle. An increased load on the lateral compartment can be observed in stance, as well as during the "two-leg phases" of the gait cycle. The highest ground reaction force occurs in mid stance, the stress is distributed evenly over the medial and lateral compartments. In terminal stance, the ground reaction force has a second peak, the resulting stress is concentrated on the medial compartment. As a result, the highest stresses over the gait cycle occur in the terminal stance phase, although this is not the overall peak of the ground reaction force.
The T2 mapping of the same patient shows only the final lesion of the cartilage. The location of this is congruent with the stress peaks in the medial femoral condyle from the FE simulation.
The FE simulation is probably suitable as a method for determining the location of the cartilage changes. To verify this, it needs to be applied to data from more patients.
References
[1] Flanigan (2010); Med Sci Sports Exerc, 42(10)
[2] Kriz (2011); Med. health, 94(7)