A new mechanical testing device for measuring anteroposterior knee laxity

Area of Science:

• Orthopedic biomechanics
• Medical device evaluation
• Knee joint kinematics

Background:

• A novel instrument, the Rolimeter, was evaluated for measuring anteroposterior (AP) translation in the knee.
• The Rolimeter's performance was benchmarked against the established KT-1000 arthrometer.

Purpose of the Study:

• To ascertain if the Rolimeter provides a valid, reproducible, and reliable method for assessing knee AP translation.
• To compare the Rolimeter's efficacy against the KT-1000 arthrometer.

Main Methods:

• Two observers assessed 16 healthy subjects (32 knees) and 36 patients (72 knees) with ligament ruptures.
• Measurements of total AP translation were taken twice, 30 minutes apart, using both the Rolimeter and KT-1000 at 20 and 80 degrees of knee flexion during a manual maximal Lachman test.

Main Results:

• The Rolimeter consistently measured approximately 1 mm less AP displacement than the KT-1000 under maximal manual stress.
• Rolimeter measurements demonstrated superior consistency across observers compared to the KT-1000.
• Both instruments exhibited equivalent sensitivity and specificity for detecting knee instability.

Conclusions:

• The Rolimeter is confirmed as a reproducible and reliable tool for measuring knee AP translation, on par with the KT-1000 arthrometer.
• The Rolimeter is a valid instrument for quantifying knee AP translation.
• Optimal accuracy for the KT-1000 was observed at 20 degrees flexion, while the Rolimeter showed higher accuracy at 80 degrees flexion.