title: Differential pretensions of a flexor tendon graft for anterior cruciate ligament reconstruction: a biomechanical comparison in a porcine knee model.
abstract: OBJECTIVE
  The best way to apply the pretension force to the soft tissue graft during anterior cruciate ligament (ACL) reconstruction remains controversial. We compared manual, intra-, and extra-articular pretension techniques and determined the magnitude of displacement of the femur-graft-tibia complex in response to repetitive loading.
  
  
  METHODS
  A biomechanical-controlled study.
  
  
  METHODS
  Fresh porcine knees and profundus digital flexor tendons of hind limbs were used. Specimens were divided into 3 groups. Group A (manual pretension, n = 9) consisted of grafts that were pretensioned only by a maximal manual pull before final fixation on the tibial side. Group B (extra-articular pretension, n = 9) consisted of grafts that were pretensioned using a commercial tensiometer at 89 N for 15 minutes on the tendon preparation board, followed by pulling using maximal manual force before final fixation. Group C (intra-articular pretension, n = 9) consisted of grafts that were fastened on the femoral side first and then underwent application of a pretension force at 89 N for 5 minutes before final fixation on the tibial side. These femur-graft-tibia complexes from the 3 groups were loaded from 0 to 150 N at a frequency of 1 Hz for 1,000 cycles and then underwent a tensile load-to-failure test at a rate of 150 mm/min.
  
  
  RESULTS
  The displacement of the femur-graft-tibial complex in response to cyclic loading for group C (5.4 +/- 0.3 mm) was significantly lower than those for groups A (12.5 +/- 1.1 mm) and B (8.8 +/- 0.8 mm) (P < .001). The fixation stiffness of group C (47.9 +/- 17.6 N/mm) was significantly greater than that of group A (32.5 +/- 9.7 N/mm) (P < .05) but not significantly different from that of group B (53.1 +/- 9.1 N/mm). The ultimate failure load in each group was not significantly different.
  
  
  CONCLUSIONS
  Intra-articular pretension of the graft before final fixation can significantly minimize graft elongation at time 0 compared with manual and extra-articular pretension.
  
  
  CONCLUSIONS
  Intra-articular or in vivo pretension of the graft using instruments may minimize the graft elongation in the early period of rehabilitation after ACL reconstruction.
authors.affiliation: Department of Biomedical Engineering, Biomechanical Laboratory, Orthopaedic Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC. chianherlee@yahoo.com.tw
authors.forename: Chian-Her
authors.initials: CH
authors.lastname: Lee
authors.forename: Guo-Shu
authors.initials: GS
authors.lastname: Huang
authors.forename: Kuo-Hua
authors.initials: KH
authors.lastname: Chao
authors.forename: Shing-Sheng
authors.initials: SS
authors.lastname: Wu
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D005269:Femur / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D023421:Models, Animal; D019651:Plastic Surgery Procedures; D013552:Swine; D013710:Tendons / Q000601:surgery; D013718:Tensile Strength; D013977:Tibia / Q000601:surgery*; D017211:Treatment Failure; D016474:Weight-Bearing