Rotational instability of the knee: internal tibial rotation under a simulated pivot shift test.
BACKGROUND
Recently, several publications investigated the rotational instability of the human knee joint under pivot shift examinations and reported the internal tibial rotation as measurement for instrumented knee laxity measurements. We hypothesize that ACL deficiency leads to increased internal tibial rotation under a simulated pivot shift test. Furthermore, it was hypothesized that anatomic single bundle ACL reconstruction significantly reduces the internal tibial rotation under a simulated pivot shift test when compared to the ACL-deficient knee.


METHODS
In seven human cadaveric knees, the kinematics of the intact knee, ACL-deficient knee, and anatomic single bundle ACL reconstructed knee were determined in response to a 134 N anterior tibial load and a combined rotatory load of 10 N m valgus and 4 N m internal tibial rotation using a robotic/UFS testing system. Statistical analyses were performed using a two-way ANOVA test.


RESULTS
Single bundle ACL reconstruction reduced the anterior tibial translation under a simulated KT-1000 test significantly compared to the ACL-deficient knee (P < 0.05). After reconstruction, there was a statistical significant difference to the intact knee at 30 degrees of knee flexion. Under a simulated pivot shift test, anatomic single bundle ACL reconstruction could restore the intact knee kinematics. Internal tibial rotation under a simulated pivot shift showed no significant difference in the ACL-intact, ACL-deficient and ACL-reconstructed knee.


CONCLUSIONS
In conclusion, ACL deficiency does not increase the internal tibial rotation under a simulated pivot shift test. For objective measurements of the rotational instability of the knee using instrumented knee laxity devices under pivot shift mechanisms, the anterior tibial translation should be rather evaluated than the internal tibial rotation.
Diermann
Nadine
N
Department of Trauma, Hand and Reconstructive Surgery, Westfalian Wilhelms University Muenster, Germany.
Schumacher
Tobias
T
Schanz
Steffen
S
Raschke
Michael J
MJ
Petersen
Wolf
W
Zantop
Thore
T
D000368:Aged; D016118:Anterior Cruciate Ligament / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D002102:Cadaver; D003198:Computer Simulation; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000502:physiology / Q000503:physiopathology; D008875:Middle Aged; D010808:Physical Examination; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures; D012371:Robotics; D013314:Stress, Mechanical