title: Bleeding from the bone marrow enhances remodeling of the in situ frozen-thawed anterior cruciate ligament.
abstract: BACKGROUND
  The purpose of this study is to biomechanically and histologically evaluate the effect of bleeding from bone marrow on remodeling of the in situ frozen-thawed anterior cruciate ligament.
  
  
  METHODS
  Forty-four rabbits were used. Eight rabbits were used to evaluate the amount of bleeding at days 1-4. Thirty-six rabbits were divided into two groups, after the right anterior cruciate ligament underwent the freeze-thaw treatment. In Group I, no treatments were applied. In Group II, a tunnel was drilled into the bone marrow the femoral intercondylar notch. Each rabbit was sacrificed at 6 or 12 weeks. We examined the mechanical properties, and the histology of the anterior cruciate ligament.
  
  
  RESULTS
  A small amount of blood clot was observed only on the first day in Group I, while a large amount of blood clot was seen around the anterior cruciate ligament for 3 days after surgery in Group II. In the midsubstance, a number of cells were scattered in Group II, no cells were seen in Group I at 6 weeks. The tangent modulus showed some tendency of difference between Groups I and II at each period.
  
  
  CONCLUSIONS
  Bleeding from the bone marrow obviously enhanced extrinsic cell infiltration into the in situ frozen-thawed anterior cruciate ligament at 6 weeks, and showed some effects on its mechanical properties. This study implied that, in anterior cruciate ligament reconstruction, the blood from a bone tunnel play an important role in graft remodeling.
authors.affiliation: Department of Sports Medicine and Joint Reconstruction Surgery, Hokkaido University School of Medicine, Kita-15 Nishi-7, Kita-ku, Sapporo 060-8638, Japan. yasukaz@med.hokudai.ac.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yasuda
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Sakai
authors.forename: Eiji
authors.initials: E
authors.lastname: Kondo
authors.forename: Shin
authors.initials: S
authors.lastname: Onodera
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000166:cytology* / Q000502:physiology*; D001777:Blood Coagulation / Q000502:physiology*; D001853:Bone Marrow / Q000502:physiology*; D001854:Bone Marrow Cells / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods*; D005260:Female; D011817:Rabbits