title: Proximal Femoral Varus Derotation Osteotomy in Children with Cerebral Palsy: The Effect of Age, Gross Motor Function Classification System Level, and Surgeon Volume on Surgical Success.
abstract: BACKGROUND
  The purpose of this study was to evaluate mid-term results of proximal femoral varus derotation osteotomy (VDRO) in children with cerebral palsy and determine what effect age, Gross Motor Function Classification System (GMFCS) level, and surgeon volume had on surgical success.
  
  
  METHODS
  We analyzed a cohort of children with cerebral palsy who underwent VDRO for hip displacement at a tertiary-level pediatric hospital between 1994 and 2007. Age, sex, GMFCS level, preoperative radiographic parameters, previous botulinum toxin administration or soft-tissue release, adjunctive pelvic osteotomy, the performance of bilateral surgery at the index VDRO, and surgeon volume (the number of procedures performed) were recorded. Results were analyzed via univariate and multivariate analyses for association with the need for revision hip surgery. Kaplan-Meier survivorship curves were generated, determining the time from index surgery to failure (defined as the need for subsequent surgical procedures on the hip and/or pelvis, or a hip migration percentage of >50% at the time of final follow-up), and were further stratified according to osseous versus soft-tissue revision.
  
  
  RESULTS
  A total of 567 VDROs were performed in 320 children (mean age [and standard deviation], 8.2 ± 3.8 years). The mean follow-up was 8.3 years (range, three to eighteen years). Of the initial 320 patients, 117 (37%) were considered to have had failure. Multivariate Cox regression analysis confirmed that younger age at surgery (p < 0.001), increased GMFCS level (p = 0.01), and lower annual surgical hip volume (p = 0.02) were significant independent predictors of any type of surgical revision. Furthermore, soft-tissue release at VDRO was protective against revision (p = 0.02). Five-year survivorship analysis revealed a 92% success rate for children classified as GMFCS levels I and II compared with a 76% success rate for those of GMFCS level V (p < 0.01).
  
  
  CONCLUSIONS
  This study demonstrated a 37% failure rate after VDRO in children with cerebral palsy. Older age, lower GMFCS level, and increased surgeon volume were strong predictors of surgical success.
authors.affiliation: Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Hunnewell 221, 300 Longwood Avenue, Boston, MA 02115. E-mail address for B.J. Shore: Benjamin.shore@childrens.harvard.edu.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Shore
authors.affiliation: Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Hunnewell 221, 300 Longwood Avenue, Boston, MA 02115. E-mail address for B.J. Shore: Benjamin.shore@childrens.harvard.edu.
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.affiliation: Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Hunnewell 221, 300 Longwood Avenue, Boston, MA 02115. E-mail address for B.J. Shore: Benjamin.shore@childrens.harvard.edu.
authors.forename: Chantal
authors.initials: C
authors.lastname: Dufreny
authors.affiliation: Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Hunnewell 221, 300 Longwood Avenue, Boston, MA 02115. E-mail address for B.J. Shore: Benjamin.shore@childrens.harvard.edu.
authors.forename: Dustin
authors.initials: D
authors.lastname: Powell
authors.affiliation: Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Hunnewell 221, 300 Longwood Avenue, Boston, MA 02115. E-mail address for B.J. Shore: Benjamin.shore@childrens.harvard.edu.
authors.forename: Travis H
authors.initials: TH
authors.lastname: Matheney
authors.affiliation: Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Hunnewell 221, 300 Longwood Avenue, Boston, MA 02115. E-mail address for B.J. Shore: Benjamin.shore@childrens.harvard.edu.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Snyder
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002547:Cerebral Palsy / Q000150:complications* / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D051341:Dependent Ambulation; D005260:Female; D005269:Femur / Q000601:surgery*; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000209:etiology / Q000601:surgery*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D015999:Multivariate Analysis; D010027:Osteotomy / Q000379:methods*; D016016:Proportional Hazards Models; D012086:Reoperation; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult