Posterior cruciate ligament tibial insertion anatomy and implications for tibial tunnel placement.

PURPOSE

The purposes of this study were (1) to predict the tibial insertion of the posterior cruciate ligament (PCL) and posterior cortex that aligned with the tibial tunnel (PCTT) by use of 2-dimensional plain radiographs by evaluating the relation between plain radiograph and computed tomography (CT) images and (2) to determine the safe angle of the tibial guide for preventing breakage of the posterior cortex.

METHODS

In 10 fresh cadaveric tibias, the soft tissues were dissected and the tibial footprint of the PCL was identified. The insertion of the PCL, the longest distance from the PCTT to the posterior cortex that aligned with the tibial plateau (PCTP), and the possible maximum angle of the tibial guide to the most posteriorly positioned cortical line were measured from simple anteroposterior (AP) and lateral radiographs, as well as CT.

RESULTS

The mean tibial insertion of the PCL from the joint line was located between 5.9 ± 1.1 and 17.4 ± 2.4 mm on the simple AP radiographs and between 2.2 ± 1.2 and 12.3 ± 1.5 mm on the simple lateral radiographs (P = .005). The PCL insertion was from the posterior 48% of the area of the posterior intercondylar fossa to the posterior cortex. The longest distance from the PCTT to the PCTP was 10.8 ± 2.2 mm. The maximum angle of the tibial guide to the PCTT possible on CT and the PCTP on lateral radiographs was 52° ± 5° and 62° ± 4.5°, respectively (P = .005).

CONCLUSIONS

The mean tibial insertion of the PCL from the joint line was located higher on the lateral radiographs than on the AP radiographs, and the PCL insertion was in the posterior 48% of the area of the PCL fovea to the posterior cortex. The maximum possible angle of the tibial guide to the PCTT based on CT was 52°. Therefore the angle of the tibial guide pin must be limited for tibial footprint reconstruction to prevent posterior wall breakage.

CLINICAL RELEVANCE

Increasing the tibial guide angle may have some advantages, but there is a limit because of posterior wall breakage.