Evaluation of femoral tunnel positioning using 3-dimensional computed tomography and radiographs after single bundle anterior cruciate ligament reconstruction with modified transtibial technique

Abstract

Background: The purpose of this study is to report a modified transtibial technique to approach the center of anatomical femoral footprint in anterior cruciate ligament (ACL) reconstruction and to investigate the accurate femoral tunnel position with 3-dimensional computed tomography (3D-CT) and radiography after reconstruction.

Methods: From December 2010 to October 2011, we evaluated 98 patients who underwent primary ACL reconstruction using a modified transtibial technique to approach the center of anatomical femoral footprint in single bundle ACL reconstruction with hamstring autograft. Their femoral tunnel positions were investigated with 3D-CT and radiography postoperatively. Femoral tunnel angle was measured on the postoperative anteroposterior (AP) radiograph and the center of the femoral tunnel aperture on the lateral femoral condyle was assessed with 3D-CT according to the quadrant method by two orthopedic surgeons.

Results: According to the quadrant method with 3D-CT, the femoral tunnel was measured at a mean of 32.94% ± 5.16% from the proximal condylar surface (parallel to the Blumensaat line) and 41.89% ± 5.58% from the notch roof (perpendicular to the Blumensaat line) with good interobserver (intraclass correlation coefficients [ICC], 0.766 and 0.793, respectively) and intraobserver reliability (ICC, 0.875 and 0.893, respectively). According to the radiographic measurement on the AP view, the femoral tunnel angles averaged 50.43° ± 7.04° (ICC, 0.783 and 0.911, respectively).

Conclusions: Our modified transtibial technique is anticipated to provide more anatomical placement of the femoral tunnel during ACL reconstruction than the former traditional transtibial techniques.

Keywords: 3-Dimensional computed tomography; Anterior cruciate ligament reconstruction; Femoral tunnel; Transtibial technique.

Fig. 1

(A) The medial-lateral view of the lateral femoral condyle is obtained from the 3-dimensional computed tomography, and is rotated to the strictly lateral position. (B) A rectangular measurement frame is drawn over the medial-lateral view of the lateral femoral condyle described by Bernard et al. (C) Lateral inclination of the femoral bone tunnel was measured with reference to a line tangent to the femoral condyle.

Fig. 2

(A) The triangular shaped funnel trough is made in femoral anterior cruciate ligament insertion. (B) A picture of a triangular shaped funnel model. (C) The starting point of the tibial tunnel (blue circle) is the point of interaction between lateral to anterior margin of the medial collateral ligament (white arrow) and upper margin of pes anserinus (black arrow).

Fig. 3

(A) After creating a tibial tunnel whose size matches the diameter of the graft, the guide wire is inserted into the tibial tunnel by free-hand techniques. (B) The guide wire is inserted toward the triangular shaped funnel trough of the femur. (C) While the knee is extended gradually, the guide wire is slid into the anatomical footprint in the bony trough. (D) To prevent posterior wall blowout, the knee is flexed gradually until 90 degrees.

Fig. 4

Distributed mid-tunnel points of femoral tunnels according to our modified transtibial technique. Blue circle is the mid-tunnel point of femoral tunnel with traditional transtibial method.