Three-Dimensional Analysis of Bone Tunnel Changes After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Using Multidetector-Row Computed Tomography

Abstract

Background: The femoral and tibial bone tunnel enlargement after anatomic double-bundle anterior cruciate ligament reconstruction (ACL-R) has not been fully documented. Purpose: To evaluate the region-specific bone tunnel volume changes and those transpositions using 3-dimensional multidetector-row computed tomography (MDCT) after anatomic double-bundle ACL-R. Study design: Case series; Level of evidence, 4. Methods: Eleven patients who underwent unilateral double-bundle ACL-R with hamstring tendon autografts were included in this study. MDCT scanning of their knees was performed at 3 weeks and 1 year after surgery. The bone tunnel regions were extracted from the MDCT images, and the longitudinal axis of each bone tunnel was divided into 3 equal sections. The centroids of the outside and the articular thirds were then extracted from the bone tunnel position. Changes in the bone tunnel volume and the transposition of the articular third were calculated and compared. Results: At 1 year postoperatively, as compared with the 3-week postoperative value (set at 100%), the femoral bone tunnel volume of the anteromedial bundle (AMB) and posterolateral bundle (PLB) changed to 77.4% ± 15.3% and 102.3% ± 19.2% in the outside third and 122.3% ± 31.8% and 112.5% ± 34.4% in the articular third, respectively. The tibial bone tunnel volume of the AMB and the PLB changed to 108.6% ± 28.7% and 105.4% ± 22.6% in the tibial articular third and 54.9% ± 25.8% and 52.5% ± 26.9% in the outside third, respectively. The femoral outside third of the AMB and the tibial outside third of both the AMB and PLB were significantly reduced in bone tunnel volume. The centroid of the femoral articular third of the AMB moved 13°, 1.1 ± 0.6 mm posterodistally, and that of the PLB moved 35°, 0.8 ± 0.4 mm anterodistally. Furthermore, the centroid of the tibial articular third of the AMB moved 14°, 2.0 ± 1.6 mm posterolaterally, and that of the PLB moved 72°, 1.0 ± 1.3 mm posterolaterally. Conclusion: Compared with 3 weeks postoperatively, the articular side outlets of the femoral and tibial bone tunnels at 1 year postoperatively had enlarged slightly but statistically maintained their volume, and they had moved a little in the direction that the grafts were pulled.