The Popliteus Bypass provides superior biomechanical properties compared to the Larson technique in the reconstruction of combined posterolateral corner and posterior cruciate ligament injury

Abstract

Purpose: This study aimed to compare the biomechanical properties of the popliteus bypass against the Larson technique for the reconstruction of a combined posterolateral corner and posterior cruciate ligament injury.

Methods: In 18 human cadaver knees, the kinematics for 134 N posterior loads, 10 Nm varus loads, and 5 Nm external rotational loads in 0°, 20°, 30°, 60,° and 90° of knee flexion were measured using a robotic and optical tracking system. The (1) posterior cruciate ligament, (2) meniscofibular/-tibial fibers, (3) popliteofibular ligament (PFL), (4) popliteotibial fascicle, (5) popliteus tendon, and (6) lateral collateral ligament were cut, and the measurements were repeated. The knees underwent posterior cruciate ligament reconstruction, and were randomized into two groups. Group PB (Popliteus Bypass; n = 9) underwent a lateral collateral ligament and popliteus bypass reconstruction and was compared to Group FS (Fibular Sling; n = 9) which underwent the Larson technique.

Results: Varus angulation, posterior translation, and external rotation increased after dissection (p < 0.01). The varus angulation was effectively reduced in both groups and did not significantly differ from the intact knee. No significant differences were found between the groups. Posterior translation was reduced by both techniques (p < 0.01), but none of the groups had restored stability to the intact state (p < 0.02), with the exception of group PB at 0°. No significant differences were found between the two groups. The two techniques revealed major differences in their abilities to reduce external rotational instability. Group PB had less external rotational instability compared to Group FS (p < 0.03). Only Group PB had restored rotational instability compared to the state of the intact knee (p < 0.04) at all degrees of flexion.

Conclusion: The popliteus bypass for posterolateral reconstruction has superior biomechanical properties related to external rotational stability compared to the Larson technique. Therefore, the popliteus bypass may have a positive influence on the clinical outcome. This needs to be proven through clinical trials.

Keywords: Biomechanics; Fibular sling; Knee; Larson; Popliteus bypass; Posterolateral corner reconstruction.