title: Tunnel widening after anatomic double-bundle and mid-position single-bundle anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  The purpose of this study was to compare the amount of postoperative bone tunnel enlargement after anatomic double-bundle (DB) and single-bundle (SB) anterior cruciate ligament (ACL) reconstruction 6 to 8 months after surgery.
  
  
  METHODS
  Twenty-one consecutive patients undergoing anatomic 4-tunnel DB ACL reconstruction and 24 patients undergoing anatomic 2-tunnel SB ACL reconstruction were included in this study. In both groups a hybrid fixation technique with interference screw and extracortical fixation at the tibia and an extracortical fixation technique at the femur were used. Magnetic resonance imaging was performed on the second postoperative day and at a mean of 8 months' follow-up (range, 6.8 to 8.3 months) to assess intraoperative and postoperative bone tunnel enlargement. Tunnel widening was determined in different planes by digitally measuring the diameters of the bone tunnels. Tunnel position was measured and classified according to Harner et al. (femoral) and Stäubli et al. and Petersen et al. (tibial).
  
  
  RESULTS
  Magnetic resonance imaging showed that all bone tunnels were anatomically placed within the area of the original ACL insertion zone. Compared with the intraoperative drill diameter, we observed only a slight increase in tunnel diameter in both groups on the second postoperative day. At 8 months postoperatively, significant bone tunnel widening occurred in all bone tunnels (P < .001). However, no significant differences were found between tunnel enlargement in the DB group and tunnel enlargement in the SB group (P > .05), either on the tibial side or on the femoral side. In 2 cases tibial tunnel communication was noted at follow-up.
  
  
  CONCLUSIONS
  With the use of anatomic SB and DB ACL reconstruction techniques, the results of bone tunnel enlargement were comparable; no significant difference was observed between the tibial and femoral tunnels.
  
  
  METHODS
  Level III, prospective comparative study.
authors.affiliation: Department of Orthopaedic and Trauma Surgery, Martin Luther Hospital, Berlin, Germany. a.achtnich@mlk-berlin.de
authors.forename: Andrea
authors.initials: A
authors.lastname: Achtnich
authors.forename: Heiner
authors.initials: H
authors.lastname: Stiepani
authors.forename: Phillipp
authors.initials: P
authors.lastname: Forkel
authors.forename: Sebastian
authors.initials: S
authors.lastname: Metzlaff
authors.forename: Enrique Lopes
authors.initials: EL
authors.lastname: Hänninen
authors.forename: Wolf
authors.initials: W
authors.lastname: Petersen
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001863:Bone Screws; D005260:Female; D005269:Femur / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D010027:Osteotomy / Q000379:methods; D011446:Prospective Studies; D013977:Tibia / Q000601:surgery*