Paper 230: Morphology of the Tibial Insertion of the Posterior Cruciate Ligament

Abstract

The posterior cruciate ligament (PCL) has been described as the primary restraint to posterior tibial translation and consists of two functional bundles; the anterolateral (AL) and posteromedial (PM) bundles. Double-bundle PCL reconstruction showed to better restore normal knee kinematics and function; however, it is usually performed using either the tibial inlay or single tibial technique. To perform an anatomical double-bundle, a two tibial tunnel PCL reconstruction, it is necessary to define the tibial insertions of the PCL and its bundles. The aim of this study is to correctly identify the PCL tibial insertion and related bony landmarks. Eighteen fresh frozen cadaver knees were used in this study. The AL and PM insertions were outlined using fine pins and all soft tissue was removed using a sodium hydroxide solution. The knees were scanned by a laser three-dimensional (3-D) scanner (FARO Laser ScanArm V2, FARO Technologies Inc., Lake Mary, Florida), and then the pictures were analyzed using specific software (Rapidform XOV and XOR, INUS Technology Inc., South Korea). The all 3-D measurements were analyzed on the tibial plane basis. The tibial plane was created on the surfaces of the tibia plateau and rectangle was fitted to the plateau edges along the posterior condylar axis. The surface area, slope angle, length and width of each insertion were calculated and their insertion centers were also defined automatically as the centroids. To obtain geometric data, their centers were projected onto the tibial plane vertically and located by anteroposterior, mediolateral and vertical dimensions. The average surface area of the AL and PM insertion were 97.3mm2 and 165.0mm2. The average length and width of the AL insertion were 8.9mm and 10.6mm, PM insertion were 9.8mm and 16.9mm. The average distances from the anterior and medial margin of the tibial plane to the AL center were 85.7% and 47.5%, PM center were 94.5% and 44.1%. The AL bundle was attached to the superolateral aspect of the fossa, which was termed “AL slope”. The PM bundle was attached to inferomedial aspect, which was termed “PM slope” and also extended below the posterior rim. A clear change of slope was observed between the AL and PM slopes in all knees. The average angle between the AL and PM slopes was 13.6 degree. This study details the 3-D anatomical measurements and visualization of the tibial insertion PCL and its bundles. Our findings may assist in finding the bony landmarks that facilitate the accurate two tibial tunnel placements in anatomical double-bundle PCL reconstruction.