Methods:
13 patients (10m, 3f, ø36,8J, range:18-48J) undergoing primary posterior cruciate ligament single bundle reconstruction (PCLR) without any injury of the contralateral limb were included. 9 patients underwent PCLR without posterolateral corner reconstruction (PLCR). 4 patients received combined PCLR with PLCR in modified Larson technique. Tibiofemoral rotational stability was measured with a novel developed device. An axial torque of 3 Nm is manually applied to the knee while synchronized fluoroscopic images of the tibia and femur are acquired. 3D surfaces of femur and tibia were reconstructed from MRI-imaging. The surfaces were registered to the fluoroscopic images and the tibiofemoral axial rotation calculated. The patients were evaluated preoperatively, and at a mean of 6 months (1. follow-up = 1FU) and 12 months (2. follow-up = 2FU) postoperatively with a knee flexion angle of 90°, 60° and 30°.

Results

The patients showed less stability in external rotation (ER) of the injured knee (IK) compared to the healthy knee (HK) at 90°, 60° and 30° knee flexion: ø ER for HK vs IK at 90°: 12,6°(±3,4°) vs. 18,4°(±5,7°),(p<0,01); 60°:10,0°(±3,8°) vs. 13,2°(±5,4°),(p=0,06); 30°: 7,6(±3,1°) vs. 9,5(±5,4°),(p=0,27). At the 1FU and 2FU the ER of the operated knee was reduced compared to the injured status: øER: 90°: 1FU: 15,5°(±5,0°), 2FU: 15,1°(±3,4°); 60°: 1FU: 12,3°(±4,6°), 2FU: 11,8°(±3,9°); 30°: 1FU: 8,5°(±2,8°), 2FU: 8,3°(±3,5°). The subgroup PCLR with PLCR showed preoperatively significant higher tibiofemoral instability in ER than PCLR without PLCR at all flexion angles: øER for PCLR without PLCR vs. PCLR with PLCR preoperatively: 90°: 16,1°(±5,3°) vs. 23,6°(±2,2°),(p=0,03); 60°:11,6°(±5,8°) vs. 16,8°(±2,6°),(p=0,15); 30°: 7,1(±3,5°) vs. 14,9(±5,1°),(p=0,02). The subgroup PCLR without PLCR showed preoperatively a slight but significant higher instability in external rotation of the injured knee compared to the healthy knee at 90°: øER for HK vs IK at 90°: 11,9°(±3,0°) vs.16,1°(±5,3°),(p=0,03), which was not restored after surgery: 1FU: 16,8°(±4,8°), 2FU: 15,3°(±3,6°). The subgroup PCLR with PLCR showed full restoration of instability in tibiofemoral ER after surgery at all flexion angles.

Discussion

The analysed patients undergoing single bundle reconstruction of the PCL showed preoperatively significant less stability in external tibiofemoral rotation of the injured knee compared to the healthy knee at 90° and a trend to less stability at 60° and 30° knee flexion. The subgroup with additive reconstruction of the posterolateral corner showed preoperatively higher tibiofemoral instability then the subgroup without reconstruction of the posterolateral corner at all flexion angles. Restoration of the tibiofemoral rotational stability with additive reconstruction of the posterolateral corner could be achieved. In order to restore optimal rotational stability in patients with PCL injury and to choose the optimal treatment a standardized method for measuring the tibiofemoral rotational stability, as already standardized for the anterior-posterior stability, appears to be useful.