title: Predictive formula for the length of tibial tunnel in anterior crucitate ligament reconstruction.
abstract: 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.
  
  
  METHODS
  Thirty six patients (26 males, 14 females) 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 measured 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)
  
  
  CONCLUSIONS
  This proposed predictive formula can well predict the length of the tibial tunnel at preoperative period to avoid graft-tunnel mismatch.
authors.affiliation: Department of Orthopedics, Faculty of Medicine, Thammasat University, Pathumthani, Thailand. bancha61@yahoo.com
authors.forename: Bancha
authors.initials: B
authors.lastname: Chernchujit
authors.forename: Thomas
authors.initials: T
authors.lastname: Barthel
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001182:Arthroscopy / Q000379:methods; D016025:Bone Transplantation / Q000379:methods; D050376:Bone-Patellar Tendon-Bone Grafting / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013977:Tibia / Q000601:surgery*; D055815:Young Adult