Failure of PCL Reconstructions . . . The Unrepaired PLC

abstract & commentary

Synopsis: This biomechanical study demonstrates that a posterior cruciate ligament (PCL) reconstruction can restore normal knee kinematics. However, an unrepaired posterolateral corner (PLC) significantly increases translational motion in the knee as well as the forces in the reconstructed PCL ligament.

Source: Harner CD, et al. Biomechanical analysis of a posterior cruciate ligament reconstruction. Deficiency of the posterolateral structures as a cause of graft failure. Am J Sports Med 2000;28(1):32-39.

This is a biomechanical analysis of the human knee comparing the translation, forces, and moments in knees that were intact, PCL deficient, PCL reconstructed, and PCL reconstructed with surgical resection of the PLC. Test conditions included a posterior force, external torque, and varus moments at 30° and 90° of knee flexion. A previously described robot was used to test the translation, forces, and moments. An 11-mm Achilles graft was used for the anatomic PCL reconstructions. The testing procedure followed the order of: intact knee, PCL deficient, PCL reconstructed, and, lastly, PCL reconstructed and PLC deficient.

The results demonstrated that, using this surgical technique and under these testing conditions, the PCL-reconstructed knee kinematics were within 3 mm of the intact knee. However, sectioning of the PLC increased external rotation, varus, and posterior tibial translation. Furthermore, sectioning of the PLC caused an increase in the forces transmitted to the reconstructed PCL graft.

Comment by James R. Slauterbeck, MD

PCL reconstruction historically does not yield the same good results as anterior cruciate reconstructions. Many factors may lead to this, including improper diagnosis, poor surgical technique, poor graft choice, and improper rehabilitation emphasizing early hamstring activity and the supine position. Appropriate rehabilitation for the PCL-reconstructed knee was reported in the March Sports Medicine Reports review of the Hoher et al article addressing the importance of the quadriceps in the early rehab phases.1

This well-designed study addresses biomechanically how untreated PLC injuries could adversely affect surgical results of PCL reconstructions by increasing anteroposterior (AP) and rotational translation and placing higher than desired forces on the PCL-reconstructed graft. In addition, this study demonstrates that immediately after a PCL reconstruction, relatively normal knee kinematics can be obtained in a cadaver model. This is important to document because many studies demonstrate increasing knee laxity postoperatively and others have questioned the ability to properly restore the knee kinematics with surgery.

This study highlights the need for the physician to thoroughly diagnose all clinical laxity in the knee. Posterior and rotational testing of the knee at both 30° and 90° is important. Demonstration of increased external rotational laxity and posterior tibial translation at 30° and 90° should lead one to make the diagnosis of a combined ligament injury involving the PCL and PLC. Isolated PLC injuries will demonstrate excessive external rotation at 30° with decreasing external rotation at 90°. Isolated PCL injuries will demonstrate increased AP laxity at 30° and 90° without concomitant increases in rotation. Increases in hyperextension and rotation at 30° and 90° should lead one to search for combined ligament injury involving the PCL and the posterolateral structures.

This paper provides sound biomechanical evidence to support my opinion that anatomic reconstructions for the PCL can be successful if care is taken to reconstruct the ligament and all associated posterior lateral corner injuries. An appropriate rehabilitation program must be strictly followed.

Reference

1. Slauterbeck JR. How muscle forces affect loads on the PCL. Sports Med Rep 2000;2(3):21-22.

A probable cause for failure of PCL reconstructive surgery is the:

a. use of a nonirradiated Achilles allograft.

b. use of a patellar tendon 11-mm allograft.

c. use of a patellar tendon 11-mm autograft.

d. failure to recognize concomitant PLC injury to the knee.