Predictive Formula for the Length of Tibial Tunnel in Anterior Crucitate Ligament Reconstruction
Bancha Chernchujit MD*, Thomas Barthel MD**
Affiliation : * Department of Orthopedics, Faculty of Medicine, Thammasat University, Pathumthani, Thailand ** Department of Orthopaedics, Koenig-Ludwig Haus, University of Wuerzburg, Germany
Background : The anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon bone graft is
a common procedure in orthopedics. One challenging problem found is a graft-tunnel mismatch. Previous
studies have reported the mathematic formula to predict the tibial angle length and angle to avoid graft-
tunnel mismatch but these formulas have shown limited predictability.
Objective : To propose a predictive formula for the length of tibial tunnel and to examine its predictability.
Material and Method: Thirty six patients (26 males, 14females) with ACL injury were included in this study.
The preoperativemedial proximal tibial angle was measured. Intraoperatively, the tibial tunnel length and
tibial entry point were measured. The postoperative coronal and saggital angle of tibial tunnel were mea-
sured from knee radiograph. The data were analysed by using trigonometry correlation and formulate the
predictive formula of tibial tunnel length.
Results : we found that tibial tunnel length (T) has trigonometric correlation between the location of tibial
tunnel entry point (w), coronal angle of tibial tunnel (b), saggital angle of tibial tunnel (a) and the medial
proximal tibial slope (c) by using this formula T = Wcos(c)tan(b)/sin(a)
Conclusion : This proposed predictive formula can well predict the length of the tibial tunnel at preoperative
period to avoid graft-tunnel mismatch.
Keywords : ACL reconstruction, New formula, Angle, Length, Tibial tunnel
