Rotational knee laxity: reliability of a simple measurement device in vivo.
BACKGROUND
Double bundle ACL reconstruction has been demonstrated to decrease rotational knee laxity. However, there is no simple, commercially-available device to measure knee rotation. The investigators developed a simple, non-invasive device to measure knee rotation. In conjunction with a rigid boot to rotate the tibia and a force/moment sensor to allow precise determination of torque about the knee, a magnetic tracking system measures the axial rotation of the tibia with respect to the femur. This device has been shown to have acceptable levels of test re-test reliability to measure knee rotation in cadaveric knees.


METHODS
The objective of this study was to determine reliability of the device in measuring knee rotation of human subjects. Specifically, the intra-tester reliability within a single testing session, test-retest reliability between two testing sessions, and inter-tester reliability were assessed for 11 male subjects with normal knees.


RESULTS
The 95% confidence interval for rotation was less than 5 degrees for intra-tester, test-retest, and inter-tester reliability, and the standard error of measurement for the differences between left and right knees was found to be less than 3 degrees .


CONCLUSIONS
It was found that the knee rotation measurements obtained with this device have acceptable limits of reliability for clinical use and interpretation.
Tsai
Andrew G
AG
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA. andrew.g.tsai@gmail.com
Musahl
Volker
V
Steckel
Hanno
H
Bell
Kevin M
KM
Zantop
Thore
T
Irrgang
James J
JJ
Fu
Freddie H
FH
D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology; D053587:Arthrometry, Articular / Q000295:instrumentation* / Q000379:methods; D001696:Biomechanical Phenomena; D003196:Computer Graphics; D004867:Equipment Design; D005269:Femur / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008280:Magnetics / Q000295:instrumentation*; D008297:Male; D015588:Observer Variation; D016059:Range of Motion, Articular; D012016:Reference Values; D015203:Reproducibility of Results; D012399:Rotation; D013977:Tibia / Q000502:physiology; D019415:Torque