Measurement of tension of tendon tissue based on electrical impedance

The objective of this study was to examine whether the tension of tendon tissue could be measured using electrical impedance and, if so, whether the errors in measurement of the initial tension of a reconstructed anterior cruciate ligament obtained using electrical impedance were small enough to allow its use in clinical practice. The patella-patellar tendon-tibia complex from 35 pig knees was dissected. The relationship between the impedance of the patellar tendon and the traction stress loaded on the patellar tendon, and the repeatability of stress-impedance curves was examined in 15 knees. The relationship between impedance and strain was examined in 5, the influence of the tendon traction direction on tendon impedance was examined in 5, and the influence of the axial torsional deformation of the tendon on tendon impedance was examined in 5. Moreover, the relationship between the initial tension of a reconstructed ligament measured using electrical impedance and the load applied to the reconstructed ligament was examined in the remaining 5 knees. The change in electrical impedance of the patellar tendon due to traction was mostly caused by the strain of the tendon. The mean repeatability was 9.1%, the mean error due to differences in traction direction was 9.7%, and the mean error due to axial torsional deformation was 6.8%. There was a very strong correlation between the tension of the reconstructed ligament measured using electrical impedance and the force applied to the reconstructed ligament. Therefore, electrical impedance can be used to measure tendon tension, and it serves to measure the initial tension of a reconstructed ligament consisting of tendon tissue.