title: Establishing percentile charts for hip joint capsule and synovial cavity thickness in apparently healthy children.
abstract: BACKGROUND
  The usefulness of musculoskeletal ultrasonography (MSUS) in paediatric population is limited by lack of reference values. One of such parameters is hip joint capsule thickness, postulated as an early measure for synovitis. However, the joint capsule is hardly a distinguished structure from slit synovial cavity in patients with little or no fluid collection. Therefore, in patients without effusion, it is more convenient to measure hip joint capsule thickness together with synovial cavity. The aim of the study was to establish percentile chart for hip joint capsule and synovial cavity thickness (HJC&SCT) in apparently healthy children.
  
  
  METHODS
  The analysis included 816 US of hip joint in 408 children without musculoskeletal disorders, distributed equally throughout the whole developmental period in 18 one-year subgroups. Hip joints US was performed according to standard protocol including measurement of HJC&SCT in a single rheumatology centre by three investigators.
  
  
  RESULTS
  The 3rd, 10th, 25th, 50th, 75th, 90th, and 97th HJC&SCT percentile curves were depicted in the age and height charts for the combined group of girls and boys. The median HJC&SCT values were increasing with age from 3.7 (C10 - C90: 3.3 - 4.2) mm in the first year of life up to 6.7 (5.8 - 7.3) in 16 years old, and above. In a similar way the increase was seen with height from 3.9 (3.5 - 4.7) mm in shorter than 95 cm to 6.9 (6.2 - 7.4) mm in taller than 169 cm subjects. Intra-observer and inter-observer mean precision was less than 1.8 and 12.5%, respectively.
  
  
  CONCLUSIONS
  The developed centile chart for hip joint capsule and synovial cavity thickness in the paediatric population is expected to improve detection of hip joint capsule disorders, including synovitis in juvenile idiopathic arthritis.
authors.affiliation: Department of Older Children with subunits of Neurology and Rheumatology, St. Louis Regional Specialised Children's Hospital, Krakow, Poland. zbyszekzuber@interia.pl.
authors.forename: Zbigniew
authors.identifier: http://orcid.org/0000-0001-9581-0601
authors.initials: Z
authors.lastname: Żuber
authors.affiliation: Department of Statistics, School of Pharmacy in Sosnowiec, Medical University of Silesia, Katowice, Poland.
authors.forename: Aleksander
authors.initials: A
authors.lastname: Owczarek
authors.affiliation: Department of Older Children with subunits of Neurology and Rheumatology, St. Louis Regional Specialised Children's Hospital, Krakow, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Sobczyk
authors.affiliation: Department of Older Children with subunits of Neurology and Rheumatology, St. Louis Regional Specialised Children's Hospital, Krakow, Poland.
authors.forename: Agata
authors.initials: A
authors.lastname: Migas-Majoch
authors.affiliation: Department of Older Children with subunits of Neurology and Rheumatology, St. Louis Regional Specialised Children's Hospital, Krakow, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Turowska-Heydel
authors.affiliation: Department of Older Children with subunits of Neurology and Rheumatology, St. Louis Regional Specialised Children's Hospital, Krakow, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Sternal
authors.affiliation: Department of Older Children with subunits of Neurology and Rheumatology, St. Louis Regional Specialised Children's Hospital, Krakow, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Michalczak
authors.affiliation: Department of Pathophysiology, Medical Faculty in Katowice, Medical University of Silesia, Katowice, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Chudek
mesh_terms: D000293:Adolescent; D002648:Child; D002657:Child Development / Q000502:physiology; D002675:Child, Preschool; D005260:Female; D006621:Hip Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D017746:Joint Capsule / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008297:Male; D015588:Observer Variation; D012016:Reference Values; D012044:Regression Analysis; D014463:Ultrasonography
keywords: Hip joint; Synovial joint space; Ultrasonography