Torsional Stiffness Assessment of Femora

For the biomechanical evaluation of the femora, a test device that measures the torsional stiffness of bones was used as previously described [32 (link)]. Two hours before the testing, the femora (control group1: 9 samples, group 2: 7 samples; intervention group 3: 7 samples, group 4: 6 samples) were left to thaw at room temperature in saline solution and the plate osteosynthesis was removed. While using a fixture device, the proximal and distal ends of the bone were placed into two embedding molds (Technovit 4071, Heraeus Kulzer GmbH, Germany) so that the defect region remained free to be tested. Afterwards, the proximal part of the femora was fixed and the distal part was restrained in a pivoting axis. While a linear constant rotation (20°/min) was applied by the testing device, the resulting maximum torque was recorded (8661–4500–V0200, Burster, Germany). When the measurement showed a stable decrease, the maximum torque of 0.5 Nm was reached or the bone fractured, and the recording was stopped. The contralateral femora were tested in the same way.