The Reliability of Instrumented Knee and Ankle Orthopedic Special Tests Performed with A LigMasterTM Multijoint Arthrometer
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Context: Knee and ankle joint arthrometers are designed to increase the precision and objectivity of clinical measures of joint laxity and mechanical stiffness. The LigMaster™ is a relatively new multijoint arthrometer that can be used to perform instrumented orthopedic special tests at the knee, ankle, shoulder and elbow. To date, few lower extremity studies have been conducted with this device. Objective: To establish the intrarater test-retest reliability of measuring the mechanical properties of knee and ankle ligaments with the LigMaster™ multijoint arthrometer. Design: Cross-sectional study. Setting: Research laboratory. Participants: 40 healthy, physically-active adults (20 women, 20 men; age = 22.7±2.0 yrs; height = 171.1 + 12.1 cm; mass = 71.1 + 13.9 kg). Main Outcome Measures: At the knee, the Lachman, posterior drawer, varus and valgus stress tests were performed, with displacement and slope values obtained under loads of 90 N and 130 N. At the ankle, the anterior drawer test and inversion talar tilt test were performed, with displacement and slope values obtained at 125 N and 150 N loads. For each participant, these 6 tests were performed on two occasions on the same day and test results were used to calculate intrarater test-retest reliability. Results: The test-retest reliability of one examiner performing instrumented Lachman, posterior drawer, varus and valgus stress tests ranged from “excellent” to “good to fair” (ICC3,1 = 0.85 to 0.53). The intrarater reliability of the knee slope values for the posterior drawer test, varus and valgus stress tests were also “excellent” to “good to fair” (ICC3,1 = 0.82 to 0.51). The intrarater reliability of ankle degree for the inversion talar tilt test and ankle displacement for ankle anterior drawer test at 125 N and 150 N were between “excellent” and “good to fair” (ICC3,1 = 0.79 to 0.62). The intrarater reliability of the ankle slope value for the ankle anterior drawer test “good to fair” (ICC3,1 = 0.54). Conclusion: The instrumented Lachman, valgus, and varus stress tests at the knee and inversion talar tilt test as performed with the LigMaster™ arthrometer on healthy, physically-active adults had moderate reliability. Conversely, the posterior drawer test and the ankle anterior drawer test had markedly lower levels of intrarater reliability. While this device has capabilities unlike any other commercially-available arthrometer, the LigMaster™ software generates joint displacement and mechanical stiffness values that are proprietary and thus unique to this device. These non-standard values do not correspond with output from other commercially-available arthrometers, making direct comparisons with published knee and ankle arthrometer studies difficult, if not impossible.