Morphological and functional analysis of the knee joint for implant design optimization

  • Morphologische und funktionelle Analyse des Kniegelenks zur Optimierung des Implantatdesigns

Asseln, Malte; Radermacher, Klaus (Thesis advisor); Wirtz, Dieter Christian (Thesis advisor)

Düren : Shaker (2019, 2020)
Book, Dissertation / PhD Thesis

In: Aachener Beiträge zur Medizintechnik 57
Page(s)/Article-Nr.: 1 Online-Ressource ( 281 Seiten) : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2019


The knee joint is one of the most complex joints in the human body from a biomechanical perspective. The mechanism is vulnerable to injuries and damages, such as osteoarthritis. The replacement of the natural joint by artificial components is widely accepted as a successful surgical intervention. However, the patient dissatisfaction is in the range of 10 % to 30 % and implant survivorship is limited. Many limitations can be associated to the implant design, which insufficiently reflects the patient-specific biomechanical situation and cannot adapt in contrast to the soft-tissue. The aim of this thesis was to provide fundamental morphological and morpho-functional information and to develop an integrated computer-assisted image-based workflow for implant design optimization. For the morphological analysis of the native knee joint overall 59 geometrical features of the knee were identified, fully automatically extracted from a dataset of 831 knee geometries, and used for a comprehensive statistical analysis. Most of the features showed statistically significant gender-specific differences. Subsequently, the features were classified according to the direction of their measurement and normalized. However, large inter-individual variations remained after normalization, suggesting that patient-specific design solutions are required for an optimized implant design, regardless of gender. The overall knee dimensions were used to calculate an adequate number of implant component sizes. The results indicated that there are more sizes necessary than currently offered by the market. Another major aspect was dedicated to the morpho-functional analysis. Parameterized functional surface models of the articulating surfaces of the femur, tibia, and patella were developed to allow systematic and repeatable shape variations of selected design parameters. Furthermore, we developed a patient-specific biomechanical in silico model of the lower extremity as well as an experimental in vitro knee testing rig to analyze the relation between design parameters and knee function. The patient-specific adaptation of the in silico model was based on data which is commonly available in the daily clinical routine. The mean simulation time per patient was in the range of <8 min for a deep knee bend. The feasibility of the morpho-functional analysis was demonstrated in the example of a patient-specific implant. The results of the kinematic analysis might have direct consequences on knee implant design optimization in terms of compatibility and sensitivity of design parameters.