A modified Larson's method of posterolateral corner reconstruction of the knee reproducing the physiological tensioning pattern of the lateral collateral and popliteofibular ligaments

Abstract

Background: Consensus has been lacking as to how to reconstruct the posterolateral corner (PLC) of the knee in patients with posterolateral instability. We describe a new reconstructive technique for PLC based on Larson's method, which reflects the physiological load-sharing pattern of the lateral collateral ligament (LCL) and popliteofibular ligament (PFL).

Findings: Semitendinosus graft is harvested, and one limb of the graft comprises PFL and the other comprises LCL. Femoral bone tunnels for the LCL and popliteus tendon are made at their anatomical insertions. Fibular bone tunnel is prepared from the anatomical insertion of the LCL to the proximal posteromedial portion of the fibular head, which corresponds to the insertion of the PFL. The graft end for popliteus tendon is delivered into the femoral bone tunnel and secured on the medial femoral condyle. The other end for LCL is passed through the fibular tunnel from posterior to anterior. While the knee is held in 90 of flexion, the graft is secured in the fibular tunnel using a 5 mm interference screw. Then, the LCL end is passed into the femoral bone tunnel and secured at the knee in extension.

Conclusions: Differential tension patterns between LCL and PFL is critical when securing these graft limbs. Intrafibular fixation of the graft using a small interference screw allows us to secure these two graft limbs independently with intended tension at the intended flexion angle of the knee.

Figure 1

Schematic representation of surgical landmarks over the skin (left panel). Incision is made down to the layer of the iliotibial band and biceps femoris to expose the lateral epicondyle and fibular head, respectively (right panel).

Figure 2

Preparation of two femoral tunnels and one transfibular tunnel. Both entrances of the transfibular tunnel ideally correspond to anatomical attachments for the LCL and PFL.

Figure 3

When the fibular head is small, position of the LCL insertion should preferably be shifted anteriorly to avoid the risk of avulsion of the fibular head by the reamer (A). Dynamic excursion between the two pins sticking in femoral and fibular attachments should be checked during knee flexion and extension before making the bone tunnels (B).

Figure 4

Semitendinosus tendon graft has been secured within the popliteus femoral tunnel using an Endobutton^TM, delivered below the ITB, and passed through the transfibular tunnel (A). The graft is fixed in the fibular tunnel with a metal interference screw under 10N force of pretension at 90° knee flexion (B).

Figure 5

The graft end for the LCL is delivered under the biceps and ITB (A), and is passed into the femoral bone tunnel from the lateral epicondyle to medial cortex of the femur. The graft is then secured using an interference screw under 10N force pretension with the knee in extension (B).

Figure 6

The reconstructed PFL and LCL cross over each other (A). Postoperative radiography shows hardware to be used for securing ACL, LCL, and PFL (B). When either ACL or PCL is reconstructed simultaneously, particularly with a double-bundle technique, great care should be taken with positioning of each bone tunnel to avoid overlap of these tunnels.