title: Does flexible tunnel drilling affect the femoral tunnel angle measurement after anterior cruciate ligament reconstruction?
abstract: OBJECTIVE
  To quantify the mean difference in femoral tunnel angle (FTA) as measured on knee radiographs between rigid and flexible tunnel drilling after anatomic anterior cruciate ligament (ACL) reconstruction.
  
  
  METHODS
  Fifty consecutive patients that underwent primary anatomic ACL reconstruction with a single femoral tunnel drilled with a flexible reamer were included in this study. The control group was comprised of 50 patients all of who underwent primary anatomic ACL reconstruction with a single femoral tunnel drilled with a rigid reamer. All femoral tunnels were drilled through a medial portal to ensure anatomic tunnel placement. The FTA was determined from post-operative anterior-to-posterior (AP) radiographs by two independent observers. A 5° difference between the two mean FTA was considered clinically significant.
  
  
  RESULTS
  The average FTA, when drilled with a rigid reamer, was 42.0° ± 7.2°. Drilling with a flexible reamer resulted in a mean FTA of 44.7° ± 7.0°. The mean difference of 2.7° was not statistically significant. The intraclass correlation coefficient for inter-tester reliability was 0.895.
  
  
  CONCLUSIONS
  The FTA can be reliably determined from post-operative AP radiographs and provides a useful and reproducible metric for characterizing femoral tunnel position after both rigid and flexible femoral tunnel drilling. This has implications for post-operative evaluation and preoperative treatment planning for ACL revision surgery.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Academic Medical Center, University of Amsterdam, P.O. Box 22660, 1100 DD, Amsterdam, The Netherlands. bart.muller@live.nl.
authors.forename: Bart
authors.initials: B
authors.lastname: Muller
authors.affiliation: Universitätsklinik für Unfallchirurgie, Medical University of Vienna, Vienna, Austria.
authors.forename: Marcus
authors.initials: M
authors.lastname: Hofbauer
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Akere
authors.initials: A
authors.lastname: Atte
authors.affiliation: Department of Orthopaedic Surgery, Academic Medical Center, University of Amsterdam, P.O. Box 22660, 1100 DD, Amsterdam, The Netherlands.
authors.forename: C Niek
authors.initials: CN
authors.lastname: van Dijk
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Freddie H
authors.initials: FH
authors.lastname: Fu
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000295:instrumentation / Q000379:methods*; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007717:Knee / Q000000981:diagnostic imaging / Q000601:surgery; D011184:Postoperative Period; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
keywords: Anterior cruciate ligament (ACL); Anterior cruciate ligament reconstruction; Femoral tunnel angle (FTA); Flexible tunnel drilling