title: Hip Instability in Down Syndrome: A Focus on Acetabular Retroversion.
abstract: BACKGROUND
  The aim of this study is to compare acetabular anteversion between children with Down syndrome with or without hip instability. The second aim is to report the surgical experience at our institution in treating unstable hips for this population.
  
  
  METHODS
  All children with Down syndrome who were seen at our institution between 2004 and 2014 were reviewed, and those who had pelvic axial computed tomographic or magnetic resonance imaging scans were identified. Acetabular anteversion was compared between 2 groups: those with hip instability as a single hip pathology and those without hip instability. For patients who had surgery for their unstable hips, demographic, clinical, and surgical data were recorded. Preoperative and last visit radiographs were reviewed. Extrusion index and Tonnis, Sharp, lateral center edge, and neck shaft angles were measured. Presence of Shenton's line disruption, crossover, and posterior wall signs were recorded. Independent and paired t test, Wilcoxon signed-rank test, and χ test were used with a significance level at 0.05.
  
  
  RESULTS
  Out of 308 children with Down syndrome, there were 10 patients with 13 unstable hips and 13 patients with 26 stable hips who had computed tomographic or magnetic resonance imaging scans. Age and sex distributions were similar (P>0.3) with no difference in acetabular anteversion (P=0.926) between them. Twelve patients (6 boys and 6 girls) had reconstruction for 17 hips. The mean age was 9 years (3 to 15 y) and the mean follow-up was 7 years (1.2 to 17.6 y). Five hips were painful preoperatively and 1 hip was painful at last visit. Radiographic measurements improved significantly (P<0.05). Shenton's line disruption was found in fewer hips (P=0.001) at last visit with no difference in the crossover and posterior wall signs (P=0.177).
  
  
  CONCLUSIONS
  This report suggests that a wide range of acetabular anteversion measurements exist in children with Down syndrome. After detailed anatomic study of the hip, good results with a low complication rate can be expected over the intermediate term after hip reconstruction.
  
  
  METHODS
  Level IV-prognostic and therapeutic study.
authors.affiliation: Department of Orthopedics, Nemours/Alfred I. duPont Hospital for Children, Wilmington, DE.
authors.forename: Oussama
authors.initials: O
authors.lastname: Abousamra
authors.forename: Ilhan A
authors.initials: IA
authors.lastname: Bayhan
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rogers
authors.forename: Freeman
authors.initials: F
authors.lastname: Miller
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery; D000293:Adolescent; D018771:Arthralgia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D004314:Down Syndrome / Q000453:epidemiology*; D005260:Female; D006617:Hip Dislocation / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000601:surgery; D007870:Leg Length Inequality / Q000453:epidemiology; D008279:Magnetic Resonance Imaging; D008297:Male; D011379:Prognosis; D011859:Radiography; D012008:Recurrence; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed