title: Effect of graft tensioning on mechanical restoration in a rat model of anterior cruciate ligament reconstruction using free tendon graft.
abstract: OBJECTIVE
  Initial graft tensioning is important in anterior cruciate ligament reconstruction (ACLR), but its effect on graft healing is still not clear. Since all previous animal studies on graft tensioning used bone-patellar tendon-bone, this study aimed to investigate the effect of initial graft tensioning on ACLR using tendon graft.
  
  
  METHODS
  Fifty-five Sprague-Dawley rats underwent ACLR using flexor digitorum longus tendon graft. A constant force of 2 or 4 N was applied during graft fixation. At 0, 2, and 6 weeks, knee samples were harvested (n = 6) for static knee laxity test and graft pull-out test. Histological examination was performed at 2 and 6 weeks post-injury (n = 4).
  
  
  RESULTS
  At time zero, knee laxity was restored by ACLR with 2 or 4 N tensioning as compared to ACL-deficient group (p < 0.001), and the 4 N group exhibited a better restoration as compared to 2 N group (p = 0.031). At week 2 post-operation, the 4 N group still exhibited a better restoration in knee laxity (p = 0.001) and knee stiffness (p = 0.002) than the 2 N group; the graft pull-out force (p = 0.032) and stiffness (p = 0.010) were also higher. At week 6 post-operation, there was no significant difference between the 2 and 4 N group in knee laxity and graft pull-out strength. Histological examination showed that the beneficial effect of higher initial graft tension may be contributed by maintenance of graft integrity at mid-substance and reduction in adverse peri-graft bone changes in the femoral tunnel region.
  
  
  CONCLUSIONS
  A higher initial graft tension favours the restoration of knee laxity and promotes graft healing in ACLR using free tendon graft in the rat model.
authors.affiliation: Department of Orthopaedics and Traumatology, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China. bruma@cuhk.edu.hk
authors.forename: Sai-Chuen
authors.initials: SC
authors.lastname: Fu
authors.forename: Wai-Hang
authors.initials: WH
authors.lastname: Cheng
authors.forename: Yau-Chuk
authors.initials: YC
authors.lastname: Cheuk
authors.forename: Tsui-Yu
authors.initials: TY
authors.lastname: Mok
authors.forename: Christer G
authors.initials: CG
authors.lastname: Rolf
authors.forename: Shu-Hang
authors.initials: SH
authors.lastname: Yung
authors.forename: Kai-Ming
authors.initials: KM
authors.lastname: Chan
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D050376:Bone-Patellar Tendon-Bone Grafting; D004195:Disease Models, Animal; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013710:Tendons / Q000637:transplantation*; D014945:Wound Healing