A non-invasive device to objectively measure tibial rotation: verification of the device

The purpose of this study was the correlation of the results of a new measurement device for tibial rotation (Rotameter) in comparison with the measurements of a knee navigation system as standard method. In a biomechanical laboratory study, all soft tissues were removed from 20 human cadaveric knees leaving only the intact capsule and the bone. Specific tracers were bicortically fixed in the bone in order to measure tibial rotation using a knee navigation system. The knees were fixed to a custom-made inside-boot to rule out undesirable rotation of the reconstruction inside the Rotameter measurement device. Internal and external rotation values were measured at an applied torque of 5, 10 and 15 Nm. The different methods to evaluate tibial rotation were compared using the Pearson correlation coefficient. The correlations were deemed to be reliable if a value of >or=0.80 was achieved. At 5 Nm of applied torque, high correlations for the internal rotation, external rotation and the entire rotational range were found in the Pearson correlation coefficient between the Rotameter testing device in comparison with the knee navigation system as invasive reference method. These results were also confirmed at an applied torque of 10 and 15 Nm. In conclusion, the Rotameter testing device showed high correlations compared with the knee navigation system as an invasive standard method. It might be used as a non-invasive and easy alternative to investigate tibial rotation.