PELVIX: Development of a physiologically relevant, biomechanical test setup considering internal muscle forces for the investigation of complex pelvic ring fractures

Status:

completed 07/2024

Aims:

The aim of the project was to develop a valid biomechanical test setup that is able to simulate the dynamic alternating load during walking on pelvic bones, taking into account relevant components of muscle forces. The newly developed test setup was used to compare the mechanical stability of three different treatment options used in the case of a symphysis rupture.

Activities/Methods:

A literature search and data from a multi-body simulation were used to define the forces and boundary conditions acting on the pelvis during walking. A test setup was designed and constructed on the basis of these requirements. The sensors and actuators were integrated into the setup and connected electronically to micro controllers. The program, which controls all actuators depending on the acting forces, the load cycle and sensor status, was programmed and iteratively adapted.

For the validation tests and the biomechanical tests on osteosyntheses for the symphysis, biomechanical synthetic bones were produced in-house and the three pelvic bones were screwed together, and attachment points for the application of muscle forces were integrated.

A simulated symphysis rupture was treated with three different osteosyntheses: symphysis plate with conventional screws, symphysis plate with locking screws, internal fixator. Five synthetic pelvises per group were tested in an increasing load protocol and the relative movements of the Os Pubi to each other were detected and evaluated.

Results:

In a validation study, it was shown that the new test setup makes it possible to apply the alternating forces that act on the pelvic bone during walking dynamically and in the correct ratio at the different force application points of the bone. A vertical force is applied to the sacrum and muscular forces are applied at two points on each side and these are transmitted alternately via the two hip joints without undesirable constraining forces occurring.

In the biomechanical study, in which three different treatment options for symphysis ruptures were tested, the stability of the entire pelvic ring is assessed on the basis of relative movements of the bone parts to each other. For a comprehensive evaluation of the measurement results, the relative movements at the symphysis and the sacroiliac joints must be set in relation to the respective complex load situation on the pelvis in a detailed analysis that is still pending. These results will be published and discussed in a scientific journal.

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