title: Transphyseal ACL Reconstruction in Skeletally Immature Patients: Does Independent Femoral Tunnel Drilling Place the Physis at Greater Risk Compared With Transtibial Drilling?
abstract: BACKGROUND
  Most studies examining the safety and efficacy of transphyseal anterior cruciate ligament (ACL) reconstruction for skeletally immature patients utilize transtibial drilling. Independent femoral tunnel drilling may impart a different pattern of distal femoral physeal involvement.
  
  
  OBJECTIVE
  To radiographically assess differences in distal femoral physeal disruption between transtibial and independent femoral tunnel drilling. We hypothesized that more oblique tunnels associated with independent drilling involve a significantly larger area of physeal disruption compared with vertically oriented tunnels.
  
  
  METHODS
  Cross-sectional study; Level of evidence, 3.
  
  
  METHODS
  We analyzed skeletally immature patients aged between 10 and 15 years who underwent transphyseal ACL reconstruction utilizing an independent femoral tunnel drilling technique between January 1, 2008, and March 31, 2011. These patients were matched with a transtibial technique cohort based on age and sex. Radiographic measurements were recorded from preoperative magnetic resonance imaging and postoperative radiographs.
  
  
  RESULTS
  Ten patients in each group were analyzed. There were significant differences between independent drilling and transtibial drilling cohorts in the estimated area of physeal disruption (1.64 vs 0.74 cm(2); P < .001), femoral tunnel angles (32.1° vs 72.8°; P < .001), and medial/lateral location of the femoral tunnel (24.2 vs 36.1 mm from lateral cortex; P = .001), respectively. There was a significant inverse correlation between femoral tunnel angle and estimated area of distal femoral physeal disruption (r = -0.8255, P = .003).
  
  
  CONCLUSIONS
  Femoral tunnels created with an independent tunnel drilling technique disrupt a larger area of the distal femoral physis and create more eccentric tunnels compared with a transtibial technique.
  
  
  CONCLUSIONS
  As most studies noting the safety of transphyseal ACL reconstruction have utilized a central, vertical femoral tunnel, surgeons should be aware that if an independent femoral tunnel technique is utilized during transphyseal ACL reconstruction, more physeal tissue is at risk and tunnels are more eccentrically placed across the physis when drilling at more horizontal angles. Prior studies have shown that greater physeal involvement and eccentric tunnels may increase the risk of growth disturbance.
authors.affiliation: Hasbro Children's Hospital, Providence, Rhode Island, USA.
authors.forename: Aristides I
authors.initials: AI
authors.lastname: Cruz
authors.affiliation: Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Nikita
authors.initials: N
authors.lastname: Lakomkin
authors.affiliation: Boston Children's Hospital, Boston, Massachusetts, USA.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Fabricant
authors.affiliation: The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
authors.forename: J Todd R
authors.initials: JT
authors.lastname: Lawrence
keywords: anterior cruciate ligament; athlete; knee; pediatric sports medicine; physis