title: Characteristics of hip involvement in patients with ankylosing spondylitis in Korea.
abstract: OBJECTIVE
  To evaluate the clinical course of hip arthritis and the risk factors for hip joint replacement in patients with ankylosing spondylitis (AS).
  
  
  METHODS
  In this retrospective analysis, we evaluated 488 AS patients at a single tertiary hospital. At baseline and the most recent visit to the outpatient clinic from the patients with hip arthritis in AS, radiographic hip arthritis was evaluated using the Bath Ankylosing Spondylitis Radiology Hip Index (BASRI-h). Also the average of the hip joint space width (interbone distance) at three distinct sites between the acetabulum and femoral head was recorded.
  
  
  RESULTS
  Among 488 patients with AS, 60 patients (12.3%) had hip arthritis. Erythrocyte sedimentation rate were associated with hip involvement (odds ratio, 1.01; 95% confidence interval [CI], 1.00 to 1.02;p= 0.004). Long disease duration and advanced axial disease were associated with severe hip arthritis (3 ≥ BASRI-h) at baseline. BASRI-h and interbone distance did not significantly change in patients with hip involvement during the follow-up period of 81.4 ± 35.7 months. Five patients had hip joint replacement surgery during follow-up period. The body mass index (BMI) and BASRI-h at baseline were associated with joint replacement surgery (hazard ratio [HR], 1.30; 95% CI, 1.00 to 1.67;p= 0.049 and HR, 20.64; 95% CI, 2.39 to 178.11;p= 0.006, respectively).
  
  
  CONCLUSIONS
  Most of the patients with hip arthritis in AS showed no significant radiographic progression during the follow-up period. High BMI and advanced hip arthritis at baseline were associated with hip joint replacement surgery in patients with AS.
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hyemin
authors.initials: H
authors.lastname: Jeong
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Yeong Hee
authors.initials: YH
authors.lastname: Eun
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: In Young
authors.initials: IY
authors.lastname: Kim
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hyungjin
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jaejoon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Eun-Mi
authors.initials: EM
authors.lastname: Koh
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hoon-Suk
authors.initials: HS
authors.lastname: Cha
mesh_terms: D000293:Adolescent; D000328:Adult; D019644:Arthroplasty, Replacement, Hip; D015992:Body Mass Index; D016009:Chi-Square Distribution; D018450:Disease Progression; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000209:etiology / Q000601:surgery; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D066106:Seoul; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000150:complications*; D062606:Tertiary Care Centers; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: Body mass index; Hip; Spondylitis, ankylosing