gms | German Medical Science

Purpose: The purpose of this study was to determine static stabilizing effects of the posterolateral corner by dissecting all fibers and ligaments (the arcuat complex, AC) around the popliteus tendon (PT) and the influence on lateral stability in the lateral collateral ligament (LCL) intact-state.

Methods: Kinematics were examined in 13 fresh-frozen human cadaveric knees using a robotic/UFS testing system with an optical tracking system. The knee kinematics were determined for 134N anterior/posterior loads, 10Nm valgus/varus loads and 5Nm internal/external rotational loads in 0°, 20°, 30°, 60° and 90° of knee flexion. The posterolateral corner structures were consecutively dissected: The I.) intact knee joint, II.) with dissected posterior cruciate ligament, III.) meniscofibular/-tibial fibers, IV.) popliteofibular ligament, V.) popliteotibial fascicle (last structure of static AC), VI.) PT and VII.) LCL. Statistics were calculated performing an RM-ANOVA, with significance level at p<0.05.

Results: The external rotation angle (Figure 1 [Fig. 1]) increased significantly by 2.6° to 7.9° (P<0.05) in 0° to 90° of knee flexion and posterior tibial translation increased by 2.9mm to 5.9mm in 20° to 90° of knee flexion (P<.05) after cutting the AC/PT structures (state VI, intact LCL) in contrast to the PCL deficient knee. Differences between dissected static AC and dissected PT were only found in 60° (by 2.1°; P=0.0331) and 90° external rotation tests (by 3.1°; P=.0005). In the other 28 kinematic tests, no significant differences between PT and AC were found. Cutting the AC/PT complex did not further decrease varus, valgus or anterior tibial stability in any flexion angle in comparison to the PCL dissected state.

Conclusion: The arcuat complex is an important static stabilizer for external rotation and posterior tibial loads of the knee, even in the lateral collateral ligament intact-state. After dissecting the major parts of the arcuat complex, the static stabilizing function of the popliteus tendon is lost. The arcuat complex has no varus-stabilizing function.

Clinical relevance: The anatomy and function of these structures for external-rotational and posterior-translational stabilization should be considered when performing surgery in the posterolateral corner.