The Permissive Safe Angle of the Tibial Tunnel in Transtibial Posterior Cruciate Ligament Reconstruction: A Three-Dimensional Simulation Study.

OBJECTIVE

To determine the permissive safe angle (PSA) of the tibial tunnel in transtibial posterior cruciate ligament (PCL) reconstruction based on a three-dimensional (3D) simulation study.

METHODS

This was a computer simulation study of transtibial PCL reconstruction using 3D knee models. CT images of 90 normal knee joints from 2017 to 2020 were collected in this study, and 3D knee models were established based on CT data. The tunnel approaches were subdivided into the anterior 1/3 of the anteromedial tibia (T1), middle 1/2 of the anteromedial tibia (T2), the tibial crest (T3), anterior 1/3 of the anterolateral tibia (T4), middle 1/2 of the anterolateral tibia (T5). Five tibial tunnels (T1-T5) were simulated on the 3D knee models. The PSAs, in different tibial tunnel approaches were measured, and subgroup analyses of sex, age and height were also carried out.

RESULTS

The mean PSAs of the tibial tunnels with 5 different approaches (T1-T5) were 58.49° ± 6.82°, 61.14° ± 6.69°, 56.12° ± 7.53°, 52.01° ± 8.89° and 49.90° ± 10.53°, respectively. The differences of the mean PSAs between the anteromedial and anterolateral approaches were significant (P < 0.05). However, there was no significant difference of the mean PSA value between the two anteromedial tibial tunnel approaches (T1-T2) (P > 0.05), as well as between the two anterolateral tibial tunnel approaches (T4-T5). The patient's anthropomorphic characteristics of sex, age, and height were not associated with the PSAs.

CONCLUSIONS

The PSA varied with the anteromedial, tibial crest and anterolateral approaches for transtibial PCL reconstruction, and surgeons should limit the PCL drill guide by referring to the specific PSA for different surgical approaches.