Lower Tibial Tunnel Placement in Isolated Posterior Cruciate Ligament Reconstruction: Clinical Outcomes and Quantitative Radiological Analysis of the Killer Turn

Abstract

Background: The “killer turn” effect after posterior cruciate ligament (PCL) reconstruction is a problem that can lead to graft laxity or failure. Solutions for this situation are currently lacking. Purpose: To evaluate the clinical outcomes of a modified procedure for PCL reconstruction and quantify the killer turn using 3-dimensional (3D) computed tomography (CT). Study design: Case series; Level of evidence, 4. Methods: A total of 15 patients underwent modified PCL reconstruction with the tibial aperture below the center of the PCL footprint. Next, 2 virtual tibial tunnels with anatomic and proximal tibial apertures were created on 3D CT. All patients were assessed according to the Lysholm score, International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Tegner score, side-to-side difference (SSD) in tibial posterior translation using stress radiography, and 3D gait analysis. Results: The modified tibial tunnel showed 2 significantly gentler turns (superior, 109.87° ± 10.12°; inferior, 151.25° ± 9.07°) compared with those reconstructed with anatomic (91.33° ± 7.28°; P < .001 for both comparisons) and proximal (99° ± 7.92°; P = .023 and P < .001, respectively) tibial apertures. The distance from the footprint to the tibial aperture was 16.49 ± 3.73 mm. All patient-reported outcome scores (mean ± SD) improved from pre- to postoperatively: Lysholm score, from 46.4 ± 18.87 to 83.47 ± 10.54 ( P < .001); Tegner score, from 2.47 ± 1.85 to 6.07 ± 1.58 ( P < .001); IKDC sports activities score, from 19 ± 9.90 to 33.07 ± 5.35 ( P < .001); and IKDC knee symptoms score, from 17.87 ± 6.31 to 25.67 ± 3.66 ( P < .001). The mean SSD improved from 9.15 ± 2.27 mm preoperatively to 4.20 ± 2.31 mm postoperatively ( P < .001). The reconstructed knee showed significantly more adduction (by 1.642°), less flexion (by 1.285°), and more lateral translation (by 0.279 mm) than that of the intact knee ( P < .001 for all). Conclusion: Lowering the tibial aperture during PCL reconstruction reduced the killer turn, and the clinical outcomes remained satisfactory. However, SSD and clinical outcomes were similar to those of previously described techniques using an anatomic tibial tunnel.

Biomechanical Comparison of Anatomic Versus Lower of Anteromedial and Anterolateral Tibial Tunnels in Posterior Cruciate Ligament Reconstruction

“…Compared to the AM tibial tunnel, the AL, L‐AM, and L‐AL tibial tunnels can significantly reduce the sharpness of the “killer turn”. 18 , 19 We hypothesized that the AM group would have better biomechanical properties than other tunnel groups. However, the experimental results did not support our hypothesis.…”

Biomechanical comparison of proximal, distal, and anatomic tibial tunnel for transtibial posterior cruciate ligament reconstruction

“…These results were consistent with those in two recent studies, who reported the postoperative outcomes of the distal tibial tunnel in PCL reconstruction. 20,41 Lin et al 20 included 15 patients who underwent PCL reconstruction using distal tibial tunnel. They found that a distal tunnel significantly reduced the killer turn, but the clinical outcome was similar with that of anatomic tibial tunnel within a mean follow-up of 35.4 months.…”

“…The anatomic PCL tibial tunnel has been the most commonly used technique for transtibial PCL reconstruction. 19,20 Nevertheless, accurate placement of PCL tibial tunnel at the anatomic footprint is difficult due to the limited visualization under arthroscope. For obtaining a better arthroscopic visualization, a common mistake during surgery is placing the tibial tunnel too proximal related to the anatomic tunnel.…”

The tibial tunnel drilling angles of 60° provided a lower ultimate load to failure on a single bundle posterior cruciate ligament graft using interference screw fixation compared to 30°/45°

“…Our previous research showed that the mean maximum angle of the tibial tunnel in the anteromedial approach was 58° ± 8° [26]. In previous studies on PCL reconstruction, various angles of the tibial tunnel were utilised, and angles of 45° and 60° were most commonly used by surgeons [17, 19, 28]. To our knowledge, few studies have compared the biomechanical properties of graft‐screw‐tibia constructs for different angles of the tibial tunnel in transtibial PCL reconstruction.…”