Tunnel Enlargement and Coalition After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With Hamstring Tendon Autografts: A Computed Tomography Study

Abstract

Background: Tunnel enlargement and coalition following double-bundle anterior cruciate ligament (ACL) reconstruction with hamstring tendon autografts has not yet been sufficiently studied.

Hypothesis: The incidence and the degree of femoral tunnel enlargement will be significantly greater than those for tibial tunnel enlargement after anatomic double-bundle ACL reconstruction using hamstring tendon autografts. There will be no significant correlation between tunnel enlargement and coalition and the postoperative knee laxity.

Study design: Case series; Level of evidence, 4.

Methods: Thirty-nine patients who underwent anatomic double-bundle ACL reconstruction using semitendinosus and gracilis tendon autografts were followed up for 1 year after surgery. The grafts were simultaneously fixed at 10° of knee flexion with EndoButtons and spiked staples. All patients were examined with computed tomography and the standard clinical evaluation methods at 2 weeks and 1 year after surgery.

Results: The degree of tunnel enlargement of the femoral anteromedial and posterolateral tunnels averaged 10% to 11% and 7% to 9%, respectively, while that of the tibial anteromedial and posterolateral tunnels averaged 3% to 7% and 1% to 6%. The degree and incidence of the anteromedial and posterolateral tunnel enlargement were significantly greater in the femur than in the tibia (P < .0335 and P < .0405, respectively). On the femoral and tibial intra-articular surface, tunnel outlet coalition was found in 5% and 77% of the knees, respectively, at 1 year after surgery. There was no significant correlation between tunnel enlargement and coalition and the clinical outcome.

Conclusion: The incidence and the degree of each tunnel enlargement in the femur were significantly greater than that in the tibia. However, the incidence of tunnel coalition in the femur was significantly less than that in the tibia after double-bundle ACL reconstruction with a transtibial technique. There was no significant correlation between tunnel enlargement and coalition and the clinical outcome.

Clinical relevance: The present study provides orthopaedic surgeons with important information on double-bundle ACL reconstruction with hamstring tendons.

Keywords: anterior cruciate ligament; clinical outcome; coalition; double-bundle reconstruction; hamstring tendon; tunnel enlargement.

Figure 1.

Schematic illustration of anatomic double-bundle anterior cruciate ligament reconstruction using hamstring tendon autografts. AM, anteromedial; PL, posterolateral.

Figure 2.

Computed tomographic images of the knee with anatomic double-bundle anterior cruciate ligament reconstruction at 2-week (top row) and 1-year (bottom row) follow-up. Sclerotic lines of the femoral anteromedial tunnel wall are enhanced in coronal (left), sagittal (center), and axial (right) views.

Figure 3.

Computed tomographic images of the knee with anatomic double-bundle anterior cruciate ligament reconstruction at 2-week (top row) and 1-year (bottom row) follow-up. Sclerotic lines of the tibial anteromedial tunnel wall are enhanced in coronal (left), sagittal (center), and axial (right) views.

Figure 4.

Three-dimensional computed tomography scan of (A) the femur and (B) the tibia with anatomic double-bundle anterior cruciate ligament reconstruction at 1 year after surgery.

Figure 5.

The thickness of the bony septum between the anteromedial and posterolateral tunnels in (A) the femoral and (B) tibial sides measured on 2-dimensional computed tomography images at 10 mm from the intra-articular outlet.

Figure 6.

(A) The quadrant method to evaluate the position of the femoral tunnel. A measurement grid was superimposed onto the intra-articular femoral tunnel outlet of the 3-dimensional computed tomographic (3D CT) image so that the superior limit of the grid was located on the femoral notch roof, and the anterior, posterior, distal, and proximal sides of the grid were located on the articular cartilage margin. An x-y coordinate system was placed on this grid, with the roof line of the intercondylar notch defined as the x-axis and the most proximal-posterior line of the grid lines perpendicular to the x-axis as the y-axis. On this coordinate system, the coordinates of the center of the anteromedial (AM) and posterolateral (PL) femoral tunnels were defined as follows: Xc, distance between the center and the y-axis; Yc, distance between the center and the x-axis. (B) The quadrant method to evaluate the position of the tibial tunnel. To analyze the center of the tunnel outlet position on the tibia, a rectangular grid was also superimposed onto the axial 3D CT image of the tibial plateau. The most medial-anterior corner was defined as the origin of the x-y coordinates, with the anterior line of the tibial plateau defined as the x-axis and the most medial line of the grid lines perpendicular to the x-axis defined as the y-axis. On this grid, the center of each tunnel was expressed using the above-described coordinate values (Xc, Yc). Red dots, center of the AM tunnel; blue dots, center of the PL tunnel.