title: Biomechanical comparison of hamstring and patellar tendon graft anterior cruciate ligament reconstruction techniques: The impact of fixation level and fixation method under cyclic loading.
abstract: OBJECTIVE
  To mechanically test different reconstruction techniques of the anterior cruciate ligament (ACL) under incremental cyclic loading and to evaluate the impact of the level and method of graft fixation on tensile properties of each technique.
  
  
  METHODS
  In vitro biomechanical study.
  
  
  METHODS
  Four hamstring and 1 patellar tendon reconstruction techniques were performed on 40 young to middle-aged human cadaveric knees (average age, 39 years). An anterior drawer with increasing loads of 20 N increments was applied at 30 degree of knee flexion. Anatomic, direct interference screw fixation was tested in 2 hamstring and in the patellar tendon groups. Nonanatomic (extracortical) graft anchorage was tested in the remaining 2 hamstring groups with indirect graft fixations on both sides and the combination of indirect tibial and direct femoral fixation. Structural properties were determined throughout the cyclic loading test.
  
  
  RESULTS
  The more anatomic reconstruction techniques provided significantly higher structural properties and smaller loss of fixation compared with nonanatomic, extracortical fixation, with indirect repair on both fixation sites resulting in the lowest structural properties. The tibial fixation site was the weakest link in all of the anatomic reconstructions. Patellar tendon fixation with attached bone blocks in both bone tunnels significantly improved construct stiffness and decreased graft slippage.
  
  
  CONCLUSIONS
  The results of this study suggest that anatomic fixation should be preferred for anchorage of hamstring tendons and linkage materials should be avoided. Direct soft-tissue fixation with interference screws still allows considerable graft slippage, which can be limited by using a bone block or application of a backup or hybrid fixation, especially on the tibial fixation site.
authors.affiliation: Department of Trauma and Reconstructive Surgery, Sports Traumatology and Arthroscopy Service, Charité, Campus Virchow-Clinic, Humboldt-University of Berlin, Germany.
authors.forename: Sven U
authors.initials: SU
authors.lastname: Scheffler
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Südkamp
authors.forename: Andreas
authors.initials: A
authors.lastname: Göckenjan
authors.forename: Reinhard F G
authors.initials: RF
authors.lastname: Hoffmann
authors.forename: Andreas
authors.initials: A
authors.lastname: Weiler
mesh_terms: D020341:Absorbable Implants; D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators; D008875:Middle Aged; D010329:Patella; D019651:Plastic Surgery Procedures / Q000379:methods*; D013710:Tendons / Q000502:physiology / Q000637:transplantation*; D013718:Tensile Strength