Joint Loading & Musculoskeletal Analysis
The loads acting in joint prostheses and other orthopaedic implants is still partially unknown. The acting loads are required for different purposes.
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Musculoskeletal computer models apply mechanical principles to a system composed of bones, muscles and ligaments in order to estimate internal loading conditions. The models use limited information available from direct measurements of movement and external forces to estimate quantities that cannot be easily measured in vivo, like joint contact and muscle forces. This significantly extends the possibilities to analyze the influence of external and internal factors on the dynamic internal loading of the anatomic structures. The obtained internal loading information can be utilized to perform further detailed analyses of the loading distribution within individual anatomical structures like bones. The models require validation against joint contact forces measured in vivo in a limited set of patients with instrumented joint implants. EMG measurements of muscle activity can be used as an additional mean of validation or as input for the models.
From a history of expertise in understanding the internal loading conditions present in the musculoskeletal structures of the human body, the Musculoskeletal Biomechanics group is able to determine how muscles and the specific anatomy of the lower limb interact to define the internal loads. Our group was the first to demonstrate that the musculoskeletal loading conditions could be predicted using computer modelling techniques and has directly validated these results against forces measured in vivo [1]. Our research has also developed an improved understanding of musculoskeletal motion at both the organ and limb levels. Specifically, we are able to measure whole body motion using motion capture systems, together with new approaches to deal with soft tissue artefacts [2], which are crucial for accurate musculoskeletal models.
Our computational models also allow for quantification of dynamic loading conditions at the patello-femoral joint, which show that the patella-femoral contact force can reach levels of more than three times bodyweight during daily activities of daily living [3]. Further, we have investigated the relationship between internal loading at the knee and external knee moments, which are widely used as a proxy measure for the internal loads. Here we were able to show that this often assumed relationship is present, but also highly subject-specific [4, 5].
As part of the OVERLOAD-PrevOp network, we are currently investigating the impact of training methods on osteoarthritis progression in patients with an anterior cruciate ligament rupture. In order to determine detailed cartilage loading in those patients, we are combining our musculoskeletal computer modeling expertise with efficient finite element methods developed by our cooperation partners at the Zuse Institute Berlin (ZIB).
