Biomechanical investigations on the meniscus under dynamic and shock loading conditions

• Applicant: Professor Dr. Lutz Dürselen
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 255994026

Partial meniscal resection is still the most frequent surgical procedure performed on the meniscus. It results in an increased contact pressure leading to a higher risk of premature cartilage degeneration. To overcome this problem some attempts have been conducted to replace the meniscus. However, due to the insufficient mechanical properties of the used materials these approaches have not yet been successful. By now, it is not completely understood, which mechanical loads meniscal implants are exposed to. Biomechanical investigations revealed only low tensile loads acting in the meniscal attachments during quasistatic loading conditions and during slow knee flexion-extension movements. This contradicts to the high strength of these ligaments. It is therefore hypothesized that these forces are considerably higher during dynamic movements and shock loads, as they typically occur e.g. in sports. This might have strong implications for the requirements and the design of meniscal replacement implants. To investigate this, a new dynamic knee joint simulator should be developed, which enables the creation of almost physiological loading conditions, as they occur e.g. during jump landing or under axial or rotational shock loads. The simulator will be based on an Oxford-Rig design, in which the knee joint specimen is mounted. A vertically moving cross head driven by a hydraulic actuator dynamically moves the knee joint under consideration of all required degrees of freedom. To achieve realistic joint and ground reaction forces the most important knee spanning muscle groups are simulated. The magnitude of these muscles forces and their transient characteristics during dynamic activities are calculated using inverse dynamics by a subcontractor. After designing and manufacturing the simulator will be validated with an idealized knee joint model. Subsequently, in vitro experiments on 20 knee joint specimens will be carried out to determine the loads acting on the menisci and their attachments under dynamic and shock loads. During all experiments the strain occurring in the meniscal attachments and in the meniscal periphery and the tibiofemoral contact pressure are continuously registered. Finally, tensile tests on isolated meniscal attachments are carried out to deduce the forces from the strains, which were measured during the simulator experiments. Furthermore, the new knee joint simulator will enable for a variety of other experiments requiring dynamic or shock loading conditions on e.g. meniscus, ligaments or knee joint arthroplasty.

• DFG Programme: Research Grants
• Major Instrumentation: Hydraulischer Linearantrieb
• Instrumentation Group: 2910 Dynamische Prüfmaschinen und -anlagen, Pulser