Posterior Cruciate Ligament Reconstruction with the Posterior Inlay Graft

Donald H. Johnson MD, FRCS

Key Points

The results of posterior cruciate ligament (PCL) reconstruction may be inconsistent due to the difficulty in reproducing the complex double bundle anatomy. It may also be due to the bending angle of the transtibial graft around the back of the tibia, the “killer tunnel angle.”
The indication for a posterior inlay graft is a symptomatic PCL deficient knee.
A contra-indication to the posterior inlay is a previous vascular repair.
The posterior tibia is approached with a posteromedial incision along the border of the tibia.
The bone block is fixed to the back of the tibia first, followed by tensioning and fixation in flexion of the anterolateral bundle. The posteromedial bundle is tensioned and fixed near complete knee extension. The knee is cycled through a full range of motion to ensure that there is no restriction of motion.
Postoperative rehab is slow. The patient is braced in extension, with a pad under the calf to push the tibia forward.

The surgical outcome of posterior cruciate ligament (PCL) reconstruction has been somewhat inconsistent, and this may be due to a number of factors that include:

The PCL is a double bundle ligament. The single femoral tunnel may not reproduce the anatomy as well as the double femoral tunnel.
The reconstructed graft has the continuous posterior effect of gravity that may lead to loosening in the postoperative period.
The results may not be optimum due to the technique of transtibial tunnel reconstruction. The posterior inlay may reduce the bending angle around the posterior aspect of the tibia, and thus reduce the thinning and attenuation of the graft.
Due to the harvest site morbidity, the use of autogenous grafts may not be as optimum as using a larger allograft.

The posterior inlay was initially described by Berg (1) in 1995. The original technique used a patellar tendon graft, and screwed a bone block to the posterior aspect of the tibia. The purported advantage of the posterior inlay was to reduce the killer tunnel angle around the back of the tibia. It was felt that with continued range of motion of the knee the graft would be thinned as it emerged from the tibial tunnel. The posterior inlay technique avoided this stress point.

Basic Science

There is basic laboratory science to support the use of the posterior inlay graft. Bergfeld et al. (2) has shown that with cyclic loading the graft in the transtibial tunnel procedure is thinned and attenuated around the tibia leading to graft failure. Markolf et al. (3) compared the inlay and transtibial tunnel and concluded that the inlay technique of PCL replacement was superior to the tunnel technique with respect to graft failure, graft thinning, and permanent increase in graft length.

In another study Markoff et al. (4) showed that if the bone block of the graft is put in the very proximal end of the tibial tunnel, there is little difference compared to the posterior inlay graft. Mannor et al. (5) and Harner et al. (6) have
studied the two bundle reconstruction in the lab and felt that this technique improves the kinematics. Margheritini (7) studied the kinematics and has shown that there is very little difference between the posterior inlay and the transtibial tunnel techniques.

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