Kinematic analysis of the posterior cruciate ligament, part 1: the individual and collective function of the anterolateral and posteromedial bundles.
BACKGROUND
The posterior cruciate ligament (PCL) is composed of 2 functional bundles and has an essential role in knee function and stability. There is, however, a limited understanding of the role of each individual bundle through the full range of knee flexion.


OBJECTIVE
Both bundles provide restraint to posterior tibial translation across a full range of knee flexion. At higher angles of knee flexion (>90°), the intact PCL also imparts significant rotational stability.


METHODS
Controlled laboratory study.


METHODS
Twenty matched-paired, human cadaveric knees (mean age, 55.2 years; range, 51-59 years; 6 male and 4 female pairs) were used to evaluate the kinematics of an intact, anterolateral bundle (ALB) sectioned, posteromedial bundle (PMB) sectioned, and complete PCL sectioned knee. A 6 degree of freedom robotic system was used to assess knee stability with an applied 134-N posterior tibial load, 5-N·m external and internal rotation torques, 10-N·m valgus and varus torques, and a coupled 100-N posterior tibial load and 5-N external rotation torque at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120°.


RESULTS
All sectioned states had significant increases compared with intact in posterior translation, internal rotation, and external rotation at all tested flexion angles, with the exception of the ALB sectioned state at 75° of flexion for external rotation. The significant increases (mean ± standard deviation) in posterior translation during a 134-N posterior tibial load at 90° of flexion were 0.9 ± 0.6 mm, 2.6 ± 1.8 mm, and 11.7 ± 4.0 mm for the PMB, ALB, and complete PCL sectioned states, respectively, compared with the intact state. The largest significant increases in internal rotation were in the PMB and complete PCL sectioned states at 105° of flexion, 1.3° ± 1.0° and 2.8° ± 2.1°, respectively.


CONCLUSIONS
Both the ALB and the PMB assume a significant role in resisting posterior tibial translation, at all flexion angles, suggesting a codominant relationship. The PCL provided a significant constraint to internal rotation beyond 90° of flexion.


CONCLUSIONS
This information broadens the understanding of native knee kinematics and provides a template for the evaluation of single- and double-bundle PCL reconstructions.
Robert F. LaPrade, Steadman Philippon Research Institute, 181 West Meadow Drive, Suite 1000, Vail, CO 81657. drlaprade@sprivail.org.
Nicholas I
NI
Kennedy
Coen A
CA
Wijdicks
Mary T
MT
Goldsmith
Max P
MP
Michalski
Brian M
BM
Devitt
Asbjørn
A
Årøen
Lars
L
Engebretsen
Robert F
RF
LaPrade
D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology* / Q000601:surgery; D007718:Knee Injuries / Q000601:surgery; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures; D016119:Posterior Cruciate Ligament / Q000502:physiology* / Q000601:surgery; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures; D012399:Rotation; D013977:Tibia / Q000502:physiology* / Q000601:surgery; D019415:Torque
anterolateral bundle; knee kinematics; posterior cruciate ligament; posteromedial bundle