During my studies I focused on probabilistic finite element analysis of biological structures and design optimization. My thesis topic was ‘Investigating the Relationship Between Material Property Axes and Strain Orientations in Cebus Apella Crania’. This research gave me the opportunity to collaborate with researchers in the medical, anthropological, and biological fields. Prior to joining the KNEEMO ITN and enrolling at AAU for my PhD studies, I worked in the biomedical industry at ConforMIS INC designing custom knee implants.
Musculoskeletal (MS) models are used by the scientific community to gain insight on how external forces and movements influence the human body internally. This allows researchers to quantify muscle, ligament, and joint contact forces without the use of invasive methods. The proposed research utilizes one of the leading computer modeling software systems, AnyBody Modeling System (AMS), to create subject-specific MS models. Advanced morphing methods available in AMS allow for customization of a generic cadaver-based model with respect to subject-specific morphology. Biomechanical studies have shown that individuals with knee osteoarthritis (KOA) tend to adjust their gait to alleviate pain and in turn alter their lower limb kinematics, kinetics, and muscle activities. Since those with KOA often deviate from the generalized MS model in AMS, there is a great need for individualization with regard to gait, knee laxity, muscle strength, bone geometry, and cartilage integrity.
The first goal of this project is to investigate varying levels of knee joint model complexity using subject-specific data. The initial model will allow for tibial internal rotation by integrating a sliding hinge joint controlled by knee flexion. A more realistic model will follow, devised of 11 degree-of-freedom (amongst the tibiofemoral and patellofemoral joints) and solved using force-dependent kinematics (FDK). These conceptual models provide an estimate of muscle, ligament and contact forces and secondary knee joint kinematics. The next stage of this project will merge finite element analysis (FEA) and MS modeling; establishing a subject-specific multi-scale model. A multi-scale model is necessary to examine how mechanical load distribution affects cartilage and bone integrity in knee joints by interpreting resultant stresses and strains. The validation of these models is a significant challenge researchers have been trying to overcome to allow for broader acceptance and use in the clinical setting. The predicted secondary knee joint kinematics in each model will be validated against bi-planar fluoroscopy or dynamic MRI. Knee joint motion will be observed under various loading conditions to validate the trends of the model.
In order for clinics of varying socioeconomic backgrounds to be receptive of the proposed technology it is essential to establish a low cost and time efficient process. Which leads to the final objective of this project: computational efficiency with regards to development and performance of multi-scale subject-specific models. This will allow for future studies investigating the effect of interventions (brace, insoles, muscle strengthening) on full-body dynamics and consequently detailed joint mechanics. Although the main focus of this project examines subjects with healthy knees, the validated outcomes will provide groundwork for researchers to develop patient-specific models and tailor treatments through optimization methods for individuals suffering from KOA.