A new mechanical testing device for measuring anteroposterior knee laxity

Background: The authors assessed a new instrument, the Rolimeter, for the measurement of anteroposterior translation in the knee; it was compared to the KT-1000 arthrometer. Purpose: To determine if the Rolimeter offers a valid method for the measurement of anteroposterior translation that is as reproducible and reliable as the KT-1000 arthrometer. Methods: Two of 3 observers examined 16 normal subjects (32 knees) and 36 patients (72 knees) with ligament ruptures twice, using both the Rolimeter and the KT-1000 arthrometers, 30 minutes apart. Total anteroposterior translation (manual maximal Lachman test) was recorded at 200 and 80degrees of knee flexion. Results: On average, the Rolimeter measured approximately 1 mm less anteroposterior displacement than the KT-1000 arthrometer at manual maximum stress. Rolimeter measurements were more consistent than the KT-1000 measurements as measured by our observers. Specificity and sensitivity were equivalent between the Rolimeter and the KT-1000 arthrometer. Conclusions: The Rolimeter is as reproducible and reliable as the KT-1000 arthrometer. It offers a valid method for the measurement of anteroposterior translation in the knee. Higher accuracy was obtained at 200 of flexion for the KT-1000 arthrometer and at 80degrees of flexion for the Rolimeter.