A Biomechanical Analysis of Two Reconstructive Approaches to the Posterolateral Corner of the Knee

The objective of this study was to evaluate the effects of the biceps femoris tenodesis and popliteofibular ligament reconstruction on knee biomechanics. Ten human cadaveric knees were tested in the intact, posterolateral corner (PLC)-deficient, and PLC-reconstructed conditions using a robotic/universal force moment sensor testing system. The knees were subjected to: (1) a 134 N posterior tibial load, and (2) a 10 Nm external tibial torque applied to the tibia at full extension, 30 degrees and 90 degrees of flexion. External tibial rotation of the intact knee ranged from 18.3+/-4.6 degrees at full extension to 27.9+/-4.6 degrees at 30 degrees under the 10 Nm external tibial torque. These values increased after sectioning the PLC by 2.8 degrees -7.5 degrees at 30 degrees and 90 degrees respectively. After the popliteofibular ligament reconstruction, external tibial rotation values were not significantly different from those for the intact knee at any angle tested, while values following the biceps tenodesis were as much as 5.7 degrees greater than the intact knee. Under the 134 N posterior tibial load, there were minimal decreases in posterior tibial translation of up to 0.9 mm with the biceps tenodesis and up to 1.6 mm with the popliteofibular ligament reconstruction compared to the intact knee. The in situ forces in the biceps tenodesis were not significantly different than the intact PLC at full extension or 30 degrees, while the in situ forces in the popliteofibular graft were not significantly different at any flexion angle. Our data suggests that by restoring external tibial rotation the popliteofibular ligament reconstruction more closely reproduces the primary function of the PLC as compared to the biceps tenodesis.