Measurement of posterior tibial translation in the posterior cruciate ligament-reconstructed knee: significance of the shift in the reference position.
BACKGROUND
The measurement of anterior or posterior tibial translation depends on the existence of a repeatable and accurate reference position of the knee from which the corresponding translation is measured.


OBJECTIVE
Clinical measurements of posterior tibial translation alone do not accurately reflect the laxity of posterior cruciate ligament-reconstructed knees.


METHODS
Controlled laboratory study.


METHODS
Ten human cadaveric knees were tested by using a robotic/universal force-moment sensor testing system. The reference positions and the resulting kinematics in response to a 134-N anterior-posterior tibial load were determined for the intact and reconstructed knees. Posterior cruciate ligament reconstruction was performed with the graft tensioned and fixed at two different positions: 1) 90 degrees of knee flexion with a 134-N anterior tibial load and 2) full extension with no load.


RESULTS
Posterior cruciate ligament reconstruction with graft fixation at full extension with no load resulted in anterior shift of the reference position by 1.5 to 3.2 mm. The reconstruction resulted in an overconstrained knee with significantly decreased total anterior-posterior translation of 2.6 to 3.2 mm. However, the posterior tibial translation measured was not significantly different from that of the intact knee. Posterior cruciate ligament reconstruction with graft fixation performed at 90 degrees of flexion with a 134-N anterior tibial load resulted in kinematics similar to those of the intact knee.


CONCLUSIONS
Posterior tibial translations that are measured clinically can be misleading because the reference position of the knee can be shifted significantly after posterior cruciate ligament reconstruction.


CONCLUSIONS
The measurement of total anterior-posterior translation may be a more accurate way to assess kinematics of the reconstructed knee.
Ma
C Benjamin
CB
Musculoskeletal Research Center, Department of Orthopaedic Surgery University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
Kanamori
Akihiro
A
Vogrin
Tracy M
TM
Woo
Savio L-Y
SL
Harner
Christopher D
CD
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007717:Knee / Q000502:physiology*; D008875:Middle Aged; D016119:Posterior Cruciate Ligament / Q000293:injuries* / Q000601:surgery*; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures