title: Tunnel convergence in combined anterior cruciate ligament and posterolateral corner reconstruction.
abstract: OBJECTIVE
  To examine the geometric relationship between tunnels created in the lateral femoral condyle in reconstruction of the anterior cruciate ligament (ACL) and the posterolateral structures.
  
  
  METHODS
  The geometric relationship between a standard ACL tunnel and 11 lateral femoral tunnel variations in synthetic femur specimens was examined. Tunnel collision frequency and tunnel separation were measured radiographically. Subsequent evaluation was performed on 7 paired cadaveric specimens (14 knees) to access the efficacy of 2 configurations.
  
  
  RESULTS
  Phase I-Tunnel collision frequency was 0% and 58% for 25-mm and 30-mm tunnel depths, respectively. Axial angles greater than 40 degrees and coronal angles > or =20 degrees resulted in unsafe configurations. The safest position for lateral tunnel placement was straight lateral approach (0 degrees in the coronal plane) with increased axial plane orientation (hand dropped toward the floor 40 degrees). The safe zone for lateral tunnel configuration was determined to be between [0,0] and [0,40] ([coronal, axial]). Phase II--Control group ([0,0]) collision frequencies were 43% and 86% for the 25-mm 30-mm tunnels, respectively. Experimental group ([0,40]) collision frequencies were 29% and 43% for the 25-mm and 30-mm tunnel, respectively. In femoral condyles measuring <35 mm, collision rates were 100% versus 0% in the control group ([0,0]) versus the experimental group ([0,40]). In specimens where no collision was seen, tunnel separation distance was 4.5 +/- 4.4 mm and 5.8 +/- 2.2 mm for the control and experimental groups, respectively (P = .39).
  
  
  CONCLUSIONS
  Tunnel collision occurred often. Tunnel collision is dependent on femoral condyle geometry, tunnel depth, and tunnel configuration. To minimize the potential for tunnel collision, the surgeon should maintain a neutral alignment in the coronal plane, limit lateral tunnel depth to < or =25 mm, and direct the lateral tunnel anteriorly in the axial plane to a maximum of 40 degrees.
  
  
  CONCLUSIONS
  This study describes guidelines for tunnel placement to prevent tunnel collision when performing combined ACL and posterolateral corner reconstruction.
authors.affiliation: Department of Orthopaedic Surgery, The Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Shuler
authors.forename: Louis E
authors.initials: LE
authors.lastname: Jasper
authors.forename: Peter B
authors.initials: PB
authors.lastname: Rauh
authors.forename: Michael E
authors.initials: ME
authors.lastname: Mulligan
authors.forename: Claude T
authors.initials: CT
authors.lastname: Moorman
mesh_terms: D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology* / Q000601:surgery*; D002102:Cadaver; D005269:Femur / Q000033:anatomy & histology* / Q000601:surgery*; D006801:Humans; D019637:Orthopedic Procedures