Revision of the Posterior Cruciate Ligament Reconstruction

The failure rate of posterior cruciate ligament reconstruction is reported to be 10–25%. The cause of PCL failure is reported as a single factor (44%) and multiple factors (56%) in our series. The most common cause of failure is failure to treat posterolateral rotational instability (PLRI) (40–67.6%) (cases 2 and 3); the next most common cause is tunnel misplacement (femoral and tibial tunnel) (case 3), more in femoral tunnel (31–44%), suboptimal rehabilitation, varus malalignment, primary repair, meniscal injury and cartilage lesion, etc. To achieve a successful PCL revision, the cause of the failure should first be carefully analyzed. If the location of the femoral-tibial tunnel is well analyzed and the placement of the tunnel is completely misplaced, a new tunnel can be created, but if the placement of the tunnel overlaps, the treatment method is more complicated. First, if the femoral tunnel is overlapping and widening, after 3–6 months of bone grafting (autogenous cortico-cancellous is better than allograft), the grafted bone is well incorporated, and the revision of PCL reconstruction is done. Second, with the use of a large enough bone block, an attached allograft could be used to cover the tunnel widening and overlap bone defect site in revision of PCL reconstruction with one stage. In addition, to get a successful revision of PCL reconstruction, we should not overlook associated ligament injury, such as posterolateral rotatory instability (PLRI) (case 2) and posteromedial instability (Case 2). Another thing was that if there was a previously grafted PCL or remnant PCL, it should be preserved as much as possible, as this is helpful to get stability, proprioception, blood supply to the new graft, etc. The alignment of the knee joint or lower extremity should also be carefully checked, and furthermore, if there is no posterior slope of the tibial plateau or reverse slope of the tibial plateau, the reconstructed PCL graft will be highly stressed (decreased posterior slope of the tibial plateau increases the loads on the reconstructed PCL graft) and may fail. In addition, if there was a PCL deficiency and PLRI in patients with a zero-degree posterior slope of the tibial plateau, genu recurvatum will occur, especially with a varus thrust gait when walking, so proximal tibial osteotomy should be performed first (case 4). If the tibial tunnel was good enough, it could be used to preserve the residual PCL graft. The recent use of rounded rectangular dilators or oval-shaped dilators is very helpful in preserving the graft or residual PCL as much as possible. Modified tibial inlay techniques are relatively easier to use in cases of poor tunnel position or malpositioning. If the location of the tunnel is not so good or malpositioned, it can be solved relatively easily with the modified tibial inlay technique, especially in tibial tunnel malposition. Combined injuries can be easily resolved by creating a posterolateral corner sling (PLCS) with a fibular head tunnel, especially if the grade of PLRI was 1–2°. However, for grade 3 PLRI, the stronger the ligament graft, the better, and a tibial tunnel will also be required, known as anatomic reconstruction. Sometimes, severe instability (grade 3 PLRI) of the lateral collateral ligament (LCL) with PLRI requires more reinforcement of the LCL, which will be better. When choosing a graft, a sufficiently strong ligament should be used whenever possible. In particular, the ALB reconstruction of the PCL uses the ligament diameter of at least 8–9 mm or larger and, at this time, a thickness of at least 8 mm, which is used by the tibialis allograft, Achilles allograft, or a mixture of allograft plus autogenous graft and PMB; another allograft should be used. The more the PCL bony insertion area is covered, the more we use a rounded rectangular dilator. Therefore, we can achieve good results even with a single-bundle PCL reconstruction. It is recommended to perform the interference screw fixation in the anatomically reduced anteromedial tibiofemoral condyle after 20–25 cycle loads with approximately 10–15 lbs. of tension. We can check the anteromedial step as on the normal side, usually 1 cm protrusion of the medial tibial condyle articular margin to the medial femoral condyle articular margin. In principle, the tibial side is also fixed with a post and tie after rigid fixation. It is recommended to use a double fixation (backup fixation) with a 5–6.5 mm screw and washer as the post and tie. For revision reconstruction of the posterior cruciate ligament, it is necessary to decide whether to use the tibial tunnel, i.e., the transtibial tunnel technique, or the modified tibial inlay technique. The transtibial tunnel technique can be used, but especially if the proximal tibia has a locally weakened bone or if there are too many tunnels, the modified tibial inlay technique is easier to perform. You should also consider when to perform a double-bundle reconstruction. If there is no remaining posterior cruciate ligament or graft and also if the patient’s bone size is very large, a double-bundle reconstruction will give better results. In our experience, when a tunnel is created with a rounded rectangular dilator, much more bone can be preserved and the tunnel is not enlarged as much as in the case of a conventional round tunnel (round tunnel—tunnel enlargement is about 110%, but when a rounded rectangular dilator is used, a rectangular tunnel is created, about 73% tunnel enlargement is reported in the cadaver study).