title: Effect of estrogen on tissue elasticity of the ligament proper in rabbit anterior cruciate ligament: measurements using scanning acoustic microscopy.
abstract: BACKGROUND
  Previous epidemiological studies revealed that anterior cruciate ligament (ACL) injuries were more frequently seen in female athletes than in male athletes. To elucidate the pathogenetic roles of estrogen in ACL ruptures, the elasticity of ACL tissue was measured using a scanning acoustic microscope (SAM) in an estrogen-controlled animal model.
  
  
  METHODS
  A total of 40 ovariectomized Japanese white rabbits were randomly divided into four groups according to the administered dose of 17beta-estradiol (groups L, M, H, and C). Injection of 17beta-estradiol was performed 1, 2, 3, and 4 weeks after surgery, and doses in groups L, M, and H were 50, 100, and 500 microg/kg, respectively. Group C received no estradiol. Only groups L, M, and C were used for current analyses because their mean serum estrogen levels were within the physiological range (groups C, L, M, and H: 37, 50, 60, and 231 pg/ml, respectively). Five weeks after ovariectomy, the lateral portion of the ligament was harvested. Specimens were fixed with 10% neutralized formalin and embedded in paraffin. Then, 10 mum thick sections were cut perpendicular to the ligament fibers for routine histological staining and measurement with SAM.
  
  
  RESULTS
  The mean tissue sound speeds of groups C, L, and M were 1727 +/- 32, 1683 +/- 53, and 1665 +/- 63 m/s, respectively. Group M presented significantly lower tissue sound speed than group C (P = 0.021). Furthermore, a negative correlation was found between the mean serum estrogen level and mean tissue sound speed of the ACL among all animals in groups C, L, and M (r = 0.47, P = 0.016).
  
  
  CONCLUSIONS
  The results of the present study indicated that estrogen altered the tissue elasticity of rabbit ACL. Estrogen may constitute one of the pathogenetic factors in ACL rupture in female athletes.
authors: Department of Orthopaedic Surgery, Yamagata Prefectural Shinjo Hospital, Shinjo, Japan.
authors: Koshi
authors: K
authors: Hattori
authors: Hirotaka
authors: H
authors: Sano
authors: Tatsuro
authors: T
authors: Komatsuda
authors: Yoshifumi
authors: Y
authors: Saijo
authors: Takehiko
authors: T
authors: Sugita
authors: Eiji
authors: E
authors: Itoi
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging* / Q000502:physiology* / Q000648:ultrastructure; D004548:Elasticity / Q000502:physiology*; D004958:Estradiol / Q000502:physiology*; D005260:Female; D033401:Microscopy, Acoustic; D010052:Ovariectomy; D011817:Rabbits
chemical_list: D004958:Estradiol