title: Feature selection using a principal component analysis of the kinematics of the pivot shift phenomenon.
abstract: The pivot shift test reproduces a complex instability of the knee joint following rupture of the anterior cruciate ligament. The grade of the pivot shift test has been shown to correlate to subjective criteria of knee joint function, return to physical activity and long-term outcome. This severity is represented by a grade that is attributed by a clinician in a subjective manner, rendering the pivot shift test poorly reliable. The purpose of this study was to unveil the kinematic parameters that are evaluated by clinicians when they establish a pivot shift grade. To do so, eight orthopaedic surgeons performed a total of 127 pivot shift examinations on 70 subjects presenting various degrees of knee joint instability. The knee joint kinematics were recorded using electromagnetic sensors and principal component analysis was used to determine which features explain most of the variability between recordings. Four principal components were found to account for most of this variability (69%), with only the first showing a correlation to the pivot shift grade (r = 0.55). Acceleration and velocity of tibial translation were found to be the features that best correlate to the first principal component, meaning they are the most useful for distinguishing different recordings. The magnitudes of the tibial translation and rotation were amongst those that accounted for the least variability. These results indicate that future efforts to quantify the pivot shift should focus more on the velocity and acceleration of tibial translation and less on the traditionally accepted parameters that are the magnitudes of posterior translation and external tibial rotation.
authors.affiliation: Laboratoire de recherche en imagerie et orthopédie, Centre de recherche, Centre hospitalier de l'Université de Montréal (CHUM), Montréal, Canada. dlabbe@gmail.com
authors.forename: David R
authors.initials: DR
authors.lastname: Labbe
authors.forename: Jacques A
authors.initials: JA
authors.lastname: de Guise
authors.forename: Neila
authors.initials: N
authors.lastname: Mezghani
authors.forename: Véronique
authors.initials: V
authors.lastname: Godbout
authors.forename: Guy
authors.initials: G
authors.lastname: Grimard
authors.forename: David
authors.initials: D
authors.lastname: Baillargeon
authors.forename: Patrick
authors.initials: P
authors.lastname: Lavigne
authors.forename: Julio
authors.initials: J
authors.lastname: Fernandes
authors.forename: Pierre
authors.initials: P
authors.lastname: Ranger
authors.forename: Nicola
authors.initials: N
authors.lastname: Hagemeister
mesh_terms: D000054:Acceleration; D016118:Anterior Cruciate Ligament / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D055590:Electromagnetic Phenomena; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007718:Knee Injuries / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D012399:Rotation; D012421:Rupture / Q000503:physiopathology