Steeper posterior tibial slope correlates with greater tibial tunnel widening after anterior cruciate ligament reconstruction.

Abstract

To investigate the correlation between posterior tibial slope (PTS) and tibial tunnel widening after anterior cruciate ligament reconstruction (ACL-R). Twenty-five patients underwent anatomic single-bundle ACL-R using quadriceps tendon autograft. Six months after surgery, each patient underwent high-resolution computed tomography (CT). Tibial tunnel aperture location was evaluated using a grid method. Medial and lateral PTS (°) was measured based on a previously described method. To evaluate tibial tunnel widening, cross-sectional area (CSA) of the tibial tunnel beneath the aperture was measured using CT axial slice. Nominal elliptical area was calculated using the diameter of a dilator during the surgery and the angle between the axial slice and the tunnel axis. Percentage of tunnel widening (%) was determined by dividing the CSA by the nominal area. Pearson correlation coefficient was used to explore the association between medial/lateral PTS and tibial tunnel widening (P < 0.05). Location of tibial tunnel aperture was 29.8 ± 6.3% in anterior-posterior direction, and 45.7 ± 2.1% in medial-lateral direction. Medial and lateral PTS were 3.7° ± 2.5° and 4.9° ± 2.4° respectively. Tibial tunnel widening was 97.2 ± 20.3%. Tibial tunnel widening was correlated with medial PTS (r = 0.558, P = 0.004) and lateral PTS (r = 0.431, P = 0.031). Steeper medial and lateral PTS correlated with greater tibial tunnel widening. The clinical relevance is that surgeons should be aware that PTS may affect tibial tunnel widening after ACL-R. Thus, subjects with steeper PTS may need to be more carefully followed to see if there is greater tibial tunnel widening, which might be important especially in revision ACL-R. III.