Nonanatomic tunnel position in traditional transtibial single-bundle anterior cruciate ligament reconstruction evaluated by three-dimensional computed tomography.

BACKGROUND: Transtibial drilling techniques are widely used for arthroscopic reconstruction of the anterior cruciate ligament, most likely because they simplify femoral tunnel placement and reduce surgical time. Recently, however, there has been concern that this technique results in nonanatomically positioned bone tunnels, which may cause abnormal knee function. The purpose of this study was to use three-dimensional computed tomography models to visualize and quantify the positions of femoral and tibial tunnels in patients who underwent traditional transtibial single-bundle reconstruction of the anterior cruciate ligament and to compare these positions with reference data on anatomical tunnel positions.
METHODS: Computed tomography scans were performed on thirty-two knees that had undergone transtibial single-bundle reconstruction of the anterior cruciate ligament. Three-dimensional computed tomography models were aligned into an anatomical coordinate system. Tibial tunnel aperture centers were measured in the anterior-to-posterior and medial-to-lateral directions on the tibial plateau. Femoral tunnel aperture centers were measured in anatomic posterior-to-anterior and proximal-to-distal directions and with the quadrant method. These measurements were compared with reference data on anatomical tunnel positions.
RESULTS: Tibial tunnels were located at a mean (and standard deviation) of 48.0% +/- 5.5% of the anterior-to-posterior plateau depth and a mean of 47.8% +/- 2.4% of the medial-to-lateral plateau width. Femoral tunnels were measured at a mean of 54.3% +/- 8.3% in the anatomic posterior-to-anterior direction and at a mean of 41.1% +/- 10.3% in the proximal-to-distal direction. With the quadrant method, femoral tunnels were measured at a mean of 37.2% +/- 5.5% from the proximal condylar surface (parallel to the Blumensaat line) and at a mean of 11.3% +/- 6.6% from the notch roof (perpendicular to the Blumensaat line). Tibial tunnels were positioned medial to the anatomic posterolateral position (p < 0.001). Femoral tunnels were positioned anterior to both anteromedial and posterolateral anatomic tunnel locations (p < 0.001 for both). CONCLUSIONS AND CLINICAL RELEVANCE: Transtibial anterior cruciate ligament reconstruction failed to accurately place femoral and tibial tunnels within the native anterior cruciate ligament insertion site. If anatomical graft placement is desired, transtibial techniques should be performed only after careful identification of the native insertions. If anatomical positioning of the femoral tunnel cannot be achieved, then an alternative approach may be indicated.