title: Characterization of a frozen shoulder model using immobilization in rats.
abstract: BACKGROUND
  The objective of this study was to investigate serial changes for histology of joint capsule and range of motion of the glenohumeral joint after immobilization in rats. We hypothesized that a rat shoulder contracture model using immobilization would be capable of producing effects on the glenohumeral joint similar to those seen in patients with frozen shoulder.
  
  
  METHODS
  Sixty-four Sprague-Dawley rats were randomly divided into one control group (n = 8) and seven immobilization groups (n = 8 per group) that were immobilized with molding plaster for 3 days, or for 1, 2, 3, 4, 5, or 6 weeks. At each time point, eight rats were euthanized for histologic evaluation of the axillary recess and for measurement of the abduction angle.
  
  
  RESULTS
  Infiltration of inflammatory cells was found in the synovial tissue until 2 weeks after immobilization. However, inflammatory cells were diminished and fibrosis was dominantly observed in the synovium and subsynovial tissue 3 weeks after immobilization. From 1 week after immobilization, the abduction angle of all immobilization groups at each time point was significantly lower than that of the control group.
  
  
  CONCLUSIONS
  Our study demonstrated that a rat frozen shoulder model using immobilization generates the pathophysiologic process of inflammation leading to fibrosis on the glenohumeral joint similar to that seen in patients with frozen shoulder. This model was attained within 3 weeks after immobilization. It may serve as a useful tool to investigate pathogenesis at the molecular level and identify potential target genes that are involved in the development of frozen shoulder.
authors.affiliation: Department of Rehabilitation Medicine, Dongsan Medical Center, School of Medicine, Keimyung University, Daegu, South Korea.
authors.forename: Du Hwan
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Orthopedic Surgery, Keunmadi Hospital, Kyungju, South Korea.
authors.forename: Kil-Ho
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Department of Biochemistry, School of Medicine, Keimyung University, Daegu, South Korea.
authors.forename: Yun-Mee
authors.initials: YM
authors.lastname: Lho
authors.affiliation: Department of Biochemistry, School of Medicine, Keimyung University, Daegu, South Korea.
authors.forename: Eunyoung
authors.initials: E
authors.lastname: Ha
authors.affiliation: Department of Pathology, Dongsan Medical Center, School of Medicine, Keimyung University, Daegu, South Korea.
authors.forename: Ilseon
authors.initials: I
authors.lastname: Hwang
authors.affiliation: Pain Research Center, Department of Orthopedic Surgery, Dongsan Medical Center, School of Medicine, Keimyung University, 56 Dalseong-ro, Jung-gu, Daegu, 41931, South Korea.
authors.forename: Kwang-Soon
authors.initials: KS
authors.lastname: Song
authors.affiliation: Pain Research Center, Department of Orthopedic Surgery, Dongsan Medical Center, School of Medicine, Keimyung University, 56 Dalseong-ro, Jung-gu, Daegu, 41931, South Korea. oscho5362@dsmc.or.kr.
authors.forename: Chul-Hyun
authors.initials: CH
authors.lastname: Cho
mesh_terms: D000818:Animals; D002062:Bursitis / Q000209:etiology* / Q000473:pathology*; D004195:Disease Models, Animal; D007103:Immobilization / Q000009:adverse effects*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
keywords: Animal model; Frozen shoulder; Immobilization; Rat