Knee Surgery, Sports Traumatology, Arthroscopy
Steeper posterior tibial slope correlates with greater tibial tunnel
widening after anterior cruciate ligament reconstruction
· Yasutaka Tashiro
· Elmar Herbst
· Tom Gale
· Joon Ho Wang
· James J. Irrgang
· Freddie H. Fu
Received: 16 March 2018 / Accepted: 30 May 2018
© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2018
Purpose To investigate the correlation between posterior tibial slope (PTS) and tibial tunnel widening after anterior cruci-
ate ligament reconstruction (ACL-R).
Methods 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).
Results 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).
Conclusion 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
Level of evidence III.
Keywords ACL · Anterior cruciate ligament reconstruction · Tunnel widening · Cross-sectional area · Posterior tibial
slope · Computed tomography · Bony morphology · Quadriceps tendon graft · Tibial tunnel location
ACL-R Anterior cruciate ligament reconstruction
PTS Posterior tibial slope
MRI Magnetic resonance imaging
CT Computed tomography
ICC Intraclass correlation coeﬃcient
CSA Cross-sectional area
Tunnel widening has been shown to occur following ante-
rior cruciate ligament reconstruction (ACL-R) [1, 3, 5,
15, 25, 39]. Although the majority of the previous studies
showed no signiﬁcant association between tunnel widening
and clinical outcome following primary ACL-R [3, 5, 15],
* Freddie H. Fu
Department of Orthopaedic Surgery, University
of Pittsburgh, Kaufmann Building Suite 1011, 3471 Fifth
Avenue, Pittsburgh, PA 15213, USA
Department of Orthopaedic Surgery, Kobe University
Graduate School of Medicine, Kobe, Japan
Department of Orthopaedic Sports Medicine, Klinikum
rechts der Isar, Technical University Munich, Munich,