title: Correlation of interference screw insertion torque with depth of placement in the tibial tunnel using a quadrupled semitendinosus-gracilis graft in anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  To evaluate the insertion torque of a soft-tissue interference screw in relation to depth of insertion into the tibial tunnel when used for fixation of a quadrupled semitendinosus-gracilis autograft in anterior cruciate ligament reconstruction.
  
  
  METHODS
  Biomechanical cadaver study.
  
  
  METHODS
  Ten quadrupled semitendinosus-gracilis grafts were harvested from fresh-frozen cadaver knees and fixed in donor proximal tibias using 10-mm bioabsorbable interference screws (Arthrex, Naples, FL). A cannulated torque screwdriver was used to measure screw insertion torque at 3 depths in the tibial tunnel: the outer cortex (distal third), the articular surface (proximal third), and between these 2 points (middle third).
  
  
  RESULTS
  The mean insertion torques for the distal third, middle third, and proximal third were 8.7, 4.7, and 4.3 in/lb, respectively. The insertion torque was significantly higher at the outer cortex (distal third) than the middle third and proximal third (joint line of the tibial tunnel) ( P < .05).
  
  
  CONCLUSIONS
  Our results indicate a correlation between insertion torque and depth of placement of bioabsorbable interference screws used for fixation of a semitendinosus-gracilis graft. Lower insertion torque at the articular surface, resulting in lower peak load or pullout strength, may outweigh the proposed benefits of joint-line fixation of a semitendinosus-gracilis graft used for anterior cruciate ligament reconstruction.
  
  
  CONCLUSIONS
  Studies have suggested that anatomic proximal fixation of ACL grafts in the tibial tunnel produces stability similar to intact knees. The results of our study indicate that lower insertion torque at the articular surface results in lower peak load and pullout strength of the graft, which may outweigh the proposed benefits of joint-line fixation.
authors.affiliation: Department of Orthopaedic Surgery, University of Tennessee-Campbell Clinic, Memphis, Tennessee, USA. lmjones@utmem.edu
authors.forename: Barry B
authors.initials: BB
authors.lastname: Phillips
authors.forename: E Lyle
authors.initials: EL
authors.lastname: Cain
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Dlabach
authors.forename: Frederick M
authors.initials: FM
authors.lastname: Azar
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods; D013710:Tendons / Q000637:transplantation*; D013977:Tibia