The Importance of Posterior Capsule During the Tibial Inlay PCL Reconstruction (SS-09)

Abstract

The purpose of this study was to measure the effect of a posterior capsule incision made during the tibial inlay PCL reconstruction technique on the posterior laxity of the tibia. The posterior translation of the tibia was measured under a posterior load of 130 N at 0, 30, 60, 90, and 120° of flexion with the knee joint intact. Next, the PCL was resected and the 130N load was applied again as the robot measured the resulting translation of the tibia. In order to simulate the approach of a tibial inlay reconstruction (sham operated knee), a longitudinal incision with medial and lateral soft tissue stripping sufficient to mount an inlay bone block and pass an 11mm Achilles tendon graft into the knee was made in the oblique popliteal ligament, muscle belly of the popliteus, and posterior capsule. A two way repeated measures ANOVA was performed to detect differences in the translation of the PCL deficient and sham operated knee at each of the flexion angles. The greatest differences between the deficient and sham-operated knee were observed at full extension and 120° of flexion. At full extension, the translation in the sham-operated knee averaged 1.06 ± 0.22 mm more than in the deficient knee and at 120° of flexion 1.00 ± 0.29 mm more than in the deficient knee. These values were all statistically significant (p<0.05). A small relative increase in posterior translation was noted in the current study. However, it is important to note that the poor results noted after PCL reconstruction are most likely due to multiple factors, rather than one factor alone. Although an additional 1 mm of translation is not enough to make a result poor, 1 mm added to an already imperfect operation may be significant. Therefore, it is important to consider all the small steps of the operation to make it as close to restoring normal knee kinematics as possible. A posterior capsule incision alone without associated posteromedial or posterolateral injuries may produce an additional posterior tibial translation compared to a PCL deficient knee with an intact capsule. This may help to explain a portion of the residual posterior laxity noted clinically after PCL reconstruction.