The Reliability of Sensor-Assisted Soft Tissue Measurements in Primary Total Knee Arthroplasty

In pursuit to improve soft tissue balancing in total knee arthroplasties (TKAs), a wireless device was introduced to assess femorotibial pressures. The aim of this study was to evaluate the reliability of this device. After 33 TKAs were balanced by conventional techniques, contact pressures were measured using a wireless sensor 3 times in a row; twice while the examiner was blinded for the result (n = 29); and once while the examiner was able to see the result as visual feedback (n = 32). Femorotibial pressures were measured in the medial and lateral compartments with the knee in 10°, 45°, and 90° of flexion (6 measurements per TKA). Furthermore, both the combined pressure and the difference in pressure between the compartments was calculated throughout the 3 positions (together another 6 measurements per TKA). The intraclass correlation coefficient between the blind measurements was poor in 2 of the 12 (17%), moderate in 4 of 12 (33%), and good in 6 of 12 (50%) measurements. The intraclass correlation coefficient between the blind and observing measurement was poor in 2 of the 12 (17%), moderate in 6 of 12 (50%), and good in 4 of 12 (33%) measurements. Especially measurements in 10° of flexion are associated with poorer reliability. The wireless sensor has a moderate to good reliability in 83% of the measurements.