title: Decellularized Versus Fresh-Frozen Allografts in Anterior Cruciate Ligament Reconstruction: An In Vitro Study in a Rabbit Model.
abstract: BACKGROUND
  The common fresh-frozen allografts that are used for anterior cruciate ligament (ACL) reconstructions behave slower during the remodeling process and produce weaker tendon-bone integrations than do autografts. Decellularization of allogenic tendons results in a clean and porous collagen scaffold with low antigenicity and high compatibility, which may be more suitable for ACL reconstructions.
  
  
  OBJECTIVE
  Allograft decellularization will result in a tissue structure with suitable mechanical characteristics for ACL reconstruction, thereby promoting graft remodeling and enhancing tendon-bone healing.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Decellularized allograft tissues were prepared with a pH-modified decellularization process and evaluated for their biocompatibility and biomechanical character in vitro. Eighty New Zealand White rabbits were divided into 2 groups, with 40 in each group, to receive ACL reconstruction with either fresh-frozen (common) allografts or decellularized allografts on both knees. At 2, 4, 8, and 12 weeks postoperatively, the rabbits were euthanized for biomechanical testing, micro-computed tomography analysis, and histologic analysis.
  
  
  RESULTS
  The pH-modified decellularized allograft tissues kept excellent biocompatibility and biomechanical character during the in vitro study. Biomechanical testing indicated that the decellularized allograft had significantly higher ultimate load (P = .02) and stiffness (P = .01) levels than the common allograft at 12 weeks, and there was no significant difference between the 2 groups at any other time point. The micro-CT evaluation determined significantly higher bone mineral density (P < .01) in the decellularized allograft group than that in the common allograft group at 12 weeks, but no difference between the 2 groups was observed at any other time point. Regarding bone volume/total volume, there was no difference between the 2 groups at any time point. Fibroblast ingrowths, vascular formation, and connective tissue formation in the tendon-bone interface were better in the decellularized group within 8 weeks. New bone formation was more common in the decellularized allograft group. The collagen birefringence was restored more quickly in the decellularized allograft group than in the common allograft group at all time points.
  
  
  CONCLUSIONS
  The use of pH-modified decellularized allografts compared with the common allografts resulted in better cellularity, vascularity, collagen matrix remolding, new bone formation around the graft, enhanced tendon-bone healing, and higher ultimate failure load and stiffness of the graft after ACL reconstruction in the rabbit model.
  
  
  CONCLUSIONS
  The pH-modified decellularized allograft may be a better graft option than the common fresh-frozen allograft for knee ligament reconstructions.
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Shikui
authors.initials: S
authors.lastname: Dong
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Xiaoqiao
authors.initials: X
authors.lastname: Huangfu
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Guoming
authors.initials: G
authors.lastname: Xie
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Shen
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Xiaoxi
authors.initials: X
authors.lastname: Li
authors.affiliation: Shanghai Institute of Traumatology and Orthopaedics, Shanghai Jiao Tong University Affiliated Ruijin Hospital, Shanghai, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Qi
authors.affiliation: Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China zhaojinzhong@vip.163.com.
authors.forename: Jinzhong
authors.initials: J
authors.lastname: Zhao
mesh_terms: D064591:Allografts / Q000166:cytology; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000601:surgery; D003238:Connective Tissue / Q000502:physiology; D005615:Freezing; D006863:Hydrogen-Ion Concentration; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D011817:Rabbits; D013710:Tendons / Q000502:physiology / Q000637:transplantation*; D014184:Transplantation, Homologous; D014945:Wound Healing / Q000502:physiology; D055114:X-Ray Microtomography
keywords: allograft; anterior cruciate ligament; collagen birefringence; decellularization; reconstruction; semitendinosus tendon