Abstract
PurposeThe purpose of this study was to determine the test–retest reliability and the repeatability over multiple days of a robotic testing device when used to measure laxity of the lower leg during a simulated dial test.MethodsTen healthy subjects were evaluated using an instrumented robotic lower leg testing system over 4 days. Three testing cycles were performed each day. Each leg was rotated into external and then internal rotation by servomotors until a torque threshold of 5.65 N m was reached. Load–deformation curves were generated from torque and rotation data. Both average-measure and single-measure intraclass correlation coefficients (ICC) were compared across the curves. ICC scores were also compared for features of the curves including: maximum external rotation at −5.65 N m of torque, maximum internal rotation at 5.65 N m of torque, rotation at torque 0, compliance (slope of load–deformation curve) at torque 0, endpoint compliance in external rotation, endpoint compliance in internal rotation, and play at torque 0. Play at torque 0 was defined as the width of the hysteresis curve at torque 0.ResultsAverage-measure ICC scores and test–retest scores were >0.95 along the entire load–deformation curve except around zero torque. ICC scores at maximum internal and external rotation ranged from 0.87 to 0.99 across the left and right knees. ICC scores for the other features of the curves ranged from 0.61 to 0.98. The standard error of the mean ranged from 0.0497 to 1.1712.ConclusionsThe robotic testing device in this study proved to be reliable for testing a subject multiple times both within the same day and over multiple days. These findings suggest that the device can provide a level of reliability in rotational testing that allows for clinical use of test results. Objective laxity data can improve consistency and accuracy in diagnosing knee injuries and may enable more effective treatment.
Highlights
To date, in order to diagnose pathology within the knee, physical examination and manual palpation of the knee have been performed through a series of manoeuvres/tests
A mean curve for both left and right knees with error bars representing the standard error of the mean (SEM) was constructed using the data from all days and all cycles (Fig. 5)
Pointwise intraclass correlation coefficients (ICC) scores along the entire load–deformation curves were calculated for all cycles within each day to evaluate test–retest reliability (Fig. 6)
Summary
In order to diagnose pathology within the knee, physical examination and manual palpation of the knee have been performed through a series of manoeuvres/tests. Examples of these tests include the Lachman–Trillat test, pivot shift test, varus and valgus stress tests, anterior and posterior drawer tests, and the dial test. The aforementioned tests were designed to test translational instability, rotational instability, or a combination of the two. The dial test is one method used to characterize rotatory instability
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