What Is the Optimal Position of Low Tibial Tunnel in Transtibial Posterior Cruciate Ligament Reconstruction? A Quantitative Analysis Based on 2D CT Images and 3D Knee Models.

Objectives: There is currently no consensus on the optimal placement of the low tibial tunnel for posterior cruciate ligament (PCL) reconstruction. This study aimed to perform the quantitative measurements of the optimal tangential low tibial-tunnel (OTLT) parameters based on 2D CT images and 3D virtual knee models and expect to provide reference data for clinical creation of the OTLT during the arthroscopic transtibial PCL reconstruction.

Methods: This was a retrospective CT image study. A total of 101 patients between January 2018 and December 2020 were included in our study for analysis. The CT image data of included patients were imported into Mimics software to create the 3D knee models, and the OTLT for PCL reconstruction was simulated on 2D CT images and 3D knee models, respectively. With that, the distances of the tunnel's entry (ADT) and exit points (BDT) to the tibial plateau, the length of the tunnel (LT), and the angle of the tunnel (AT) were measured. Variables were compared using the independent t-test or the Mann-Whitney u test. Correlation analyses between the data and patient demographic factors were performed using the Pearson or Spearman correlation analysis. One-way ANOVA was used to compare differences among height subgroups.

Results: The mean ADT, LT, and AT on 2D CT images were 57.96 ± 5.34 mm, 39.92 ± 5.49 mm, and 37.23° ± 4.57° respectively, smaller than the values on 3D knee models (61.86 ± 6.80 mm, 45.56 ± 4.27 mm, and 48.17° ± 6.12°, all p values < 0.001). While the mean BDT on 2D CT images was significantly larger than 3D knee models (35.28 ± 3.07 mm vs. 29.72 ± 3.00 mm, p < 0.001). The BDT showed larger in males than females, the LT showed larger in the taller group, and the AT seemed to be larger in females and shorter people (all p values < 0.05).

Conclusion: The quantitative parameters of the OTLT based on 2D CT images and 3D knee models can be used as reference data for clinical surgeons to build an anteromedial OTLT during the arthroscopic transtibial PCL reconstruction.