title: Risk factors for avascular necrosis after closed reduction for developmental dysplasia of the hip.
abstract: OBJECTIVE
  The purpose of this study was to identify and evaluate risk factors of avascular necrosis (AVN) after closed treatment for developmental dysplasia of the hip (DDH).
  
  
  METHODS
  A retrospective review of children diagnosed with DDH at a tertiary-care children's hospital between 1986 and 2009 was performed. The presence of AVN was assessed according to Salter's classification system.
  
  
  RESULTS
  Eighty-two affected hips in 70 children with an average age of 10 months at closed reduction (range 1-31 months) and 5 years (range 2-19 years) of follow-up met the inclusion criteria. Twenty-nine (of 82, 35 %) affected hips developed AVN. The use of pre-reduction traction (p = 0.019) increased the risk of AVN, while preoperative Pavlik harness or brace trial (p = 0.28), presence of ossific nucleus at the time of closed reduction (p = 0.16), and adductor tenotomy (p = 0.37) were not significant factors. Laterality (right vs. left) was also not a significant risk factor (p = 0.75), but patients who underwent closed reduction for bilateral DDH were less likely to develop AVN (p = 0.027). Overall, the degree of abduction did not affect the rate of AVN (p = 0.87). However, in patients treated with closed reduction younger than 6 months of age, the rate of AVN was increased with abduction ≥50° (9/15, 60 %) compared to abduction <50° (0/8, 0 %) (p = 0.007). Patients who developed AVN were more likely to require subsequent surgery (p = 0.034) and more likely to report a fair/poor clinical outcome (p = 0.049).
  
  
  CONCLUSIONS
  The risk of AVN (35 %) following closed reduction and spica casting for DDH is high. The degree of abduction in spica casts appears to be a risk factor in patients ≤6 months old. The authors recommend that abduction in spica casts should be limited to <50° in children younger than 6 months of age.
  
  
  METHODS
  IV.
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 Sunset Boulevard, Mailstop #69, Los Angeles, CA, 90027, USA.
authors.forename: Mathew D
authors.initials: MD
authors.lastname: Schur
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 Sunset Boulevard, Mailstop #69, Los Angeles, CA, 90027, USA.|Department of Orthopaedic Surgery, University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Children's Hospital of Philadelphia, Philadelphia, PA, USA.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Arkader
authors.affiliation: Department of Orthopaedic Surgery, University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Catalano
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 Sunset Boulevard, Mailstop #69, Los Angeles, CA, 90027, USA. pchoi@chla.usc.edu.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Choi
keywords: Abduction angle; Avascular necrosis; Closed reduction; Developmental dysplasia of the hip