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

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.

Evaluation of tibial tunnel placement in single case posterior cruciate ligament reconstruction: reducing the graft peak stress may increase posterior tibial translation

Background The killer turn has been documented as the primary drawback of posterior cruciate ligament (PCL) reconstruction. Fanelli advocated placing the tibial tunnel outlet in the inferior lateral part of the PCL fovea to reduce the killer turn. This study aimed to confirm the validity of Fanelli’s viewpoint regarding PCL reconstruction technique and to assess the specific Fanelli tunnel area on the inferior lateral part of the PCL fovea. Methods The geometrical data of the model were obtained by nuclear magnetic resonance (MRI) and computerized tomography (CT), with images taken from a healthy Chinese volunteer. The three-dimensional finite element model of the knee joint was established using Mimics, Geomagic Studio, 3-matic, and Ansys software. The finite analysis was performed after the material behavior, contact and boundary conditions, and loading were defined. The drawer tests were simulated with a posterior tibial load of 134 N at 0°, 30°, 60°, and 90° knee flexion. The PCL peak stress and tibial translation were recorded and compared among the 30 distinct tibial tunnel loci over a range of angles from 0° to 90°. Results In the area (Fanelli area, 5–20 mm inferior and 5–10 mm lateral to the PCL anatomical insertion), the lowest PCL peak stress in all sites with different flexion angles was lower than that of the PCL anatomical insertion site. The lowest PCL peak stress with different knee flexion angles was observed in the following location: 10 mm inferior and 5 mm lateral to the PCL anatomical insertion. In the Fanelli area, the tibial translations of three sites were lower and those of other sites were higher than that of the PCL anatomical insertion site. Conclusions PCL reconstruction in the Fanelli area, especially 10 mm inferior and 5 mm lateral to the PCL anatomical insertion, could reduce the peak stress of the graft and may reduce the killer turn. However, whether the posterior stability of the knee is affected needs to be further studied.

Avoiding tibia physeal injury during double-bundle posterior cruciate ligament reconstruction

BackgroundAnatomic studies of the paediatric posterior cruciate ligament (PCL) demonstrate that the tibial attachment spans the epiphysis, physis and metaphysis. To better reproduce the anatomy of the PCL and avoid direct physeal injury, a double-bundle PCL reconstruction technique that includes both an all-epiphysial and an all-metaphyseal tibial tunnel has been proposed. The purpose of this study was to evaluate tibial tunnel placement in a paediatric double-bundle PCL reconstruction technique that avoids direct physeal injury using a 3-D computer model.MethodsTen skeletally immature cadaveric knee specimens (ages 5–11) were used to create 3-D model reconstructions from CT scans. All-metaphyseal and all-epiphysial tibial tunnels were simulated with the goal of maintaining adequate spacing (≥2 mm) between the tibial physis and tunnels to avoid injury. The all-metaphyseal tunnel, simulated at sizes of 5, 6 and 7 mm, entered anteriorly, below the tibial tubercle (apophysis) and exited posteriorly in the metaphyseal PCL footprint, distal to the proximal tibial physis. Four-millimetre all-epiphysial proximal tibial tunnels were simulated to enter the epiphysis anteromedially and exit posteriorly at the central epiphysial region of the PCL footprint, proximal to the physis. The distance was measured from the all-metaphyseal tunnels to the physis posteriorly and from the all-epiphysial tunnels to the physis, both anteriorly and posteriorly.ResultsIn all specimens, the 4 mm all-epiphysial tunnel and the 5, 6 and 7 mm all-metaphyseal tunnels maintained adequate spacing, ≥2 mm from the physis. In the specimens aged 5–7 years, the 5, 6 and 7 mm all-metaphyseal tunnels measured a mean distance of 3.5, 2.8 and 2.5 mm from the physis, respectively. In the specimens aged 8–11 years, the 5, 6 and 7 mm all-metaphyseal tunnels measured a mean distance of 3.4, 2.9 and 2.6 mm from the physis. In the specimens aged 5–7 years, the all-epiphysial tunnel measured a mean of 2.1 mm to the physis anteriorly and a mean of 2.8 mm posteriorly. In the specimens aged 8–11 years, the all-epiphysial tunnel measured a mean of 2.2 mm to the physis anteriorly and 2.4 mm posteriorly.ConclusionThese computer-aided 3-D models of paediatric knees illustrate that 5, 6 and 7 mm all-metaphyseal tunnels as well as 4 mm all-epiphysial tunnels can be placed without direct injury to the proximal tibial physis. The margin of error for direct physeal injury is small, especially for the all-epiphysial tunnel. Further, the all-epiphysial tunnel, while reproducing the anatomy of the PCL epiphysial attachment, may also produce a more extreme ‘killer turn’ of the graft. Modifications to the all-epiphysial tunnel may be considered to reduce the impact of the high ‘killer turn’ angle on the tibia.Level of evidenceIV.