RELIABILITY OF LIGAMENT COMPLIANCE AND TIBIAL DISPLACEMENT MEASURES OBTAINED FROM TWO KNEE ARTHROMETERS

Abstract

PURPOSE: We evaluated inter- and intratester reliability of ligament compliance and anterior tibial displacement using a modified knee arthrometer (Telos GA-II/E, interfaced with LigMaster© Version 0.62 software), and compared these reliability estimates to a second arthrometer (KT-2000 with bundled software). Ten (5M, 5F) healthy adults (28.5 ± 6.3yrs, 168.4 ± 10.1cm, 68.5 ± 14.1kg) were tested on each leg with one of the two devices, by two experienced investigators. METHODS: Each tester completed 2 sets of 5 trials with each device, with a 2' rest between sets and testers to remove and reposition the participant each time (counterbalanced). KT-2000 data were averaged every 4N from 6–126N to provide consistent data points across all trials and subjects, and Telos data were acquired every 2 N from 50–150N. Displacement (D) was recorded as the anterior tibial translation (mm) at 126N and 150N respectively and compliance (C) was recorded as the slope of the line (mm/N) from 6 - 126N and 50–150N respectively. For each test set, trials 2–4 were averaged for data analysis. Intratester reliability between test sets 1 and 2, and intertester reliability between test set 1 were calculated for each device using ICC (2, k) and the standard error of measurement. RESULTS: Both testers (T1, T2) demonstrated excellent test-retest reliability for D on both the KT2000 [ICC = .95, SEM = .38mm (T1); ICC = .97, SEM = .38 (T2)] and the Telos [ICC = .85, SEM = 1.5mm (T1); ICC = .88, SEM = 1.3mm (T2)]. Intratester reliability for C was similar [KT2000: ICC = .96, SEM = .003 (T1); ICC = .97, SEM = .003 (T2); Telos: ICC = .90, SEM = .075 (T1); ICC = .92, SEM = .052 (T2). While intertester reliability was high for the KT 2000 on D (ICC = .92, SEM = .50) and C (ICC = .91, SEM = .005), it was somewhat lower for Telos measures of D (ICC = .73, SEM = 1.5) and C (ICC = .72, SEM = .122). CONCLUSION: The positioning of subjects in the Telos device is in sidelying, with the lumbar spine in neutral, hips and shoulders level and perpendicular to the testing table, and knee flexed to 30 degrees. The complexity of the Telos positioning is likely responsible for the lower intertester reliability coefficients. Our results suggest that experienced testers can obtain consistent measures with the modified arthrometer, but that considerable training is necessary to obtain consistent positioning and measures between testers. Sponsor NIH Grant #1 RO3 AR 47178–01