title: Proximal Femoral Growth Modification: Effect of Screw, Plate, and Drill on Asymmetric Growth of the Hip.
abstract: BACKGROUND
  Guided growth has long been used in the lower extremities but has not been applied to varus or valgus deformity in the hip, as may occur in children with cerebral palsy or developmental dysplasia of the hip. The purpose of this study was to determine if screw, plate, or drilling techniques decreased the femoral neck-shaft angle (NSA) and articular trochanteric disease (ATD), as well as describe growth plate structural changes with each method.
  
  
  METHODS
  Twelve 8-week-old lambs underwent proximal femoral hemiepiphysiodesis (IACUC approved) using either a screw (n=4), plate (n=4), or drilling procedure (n=4). Postoperative time was 6 months. Radiographs taken after limb harvest were used to measure NSA and ATD. Differences between treated and control sides were determined by 1-tailed paired t tests and Bonferroni (α=0.05/3). Histology was obtained for 1 limb pair per group. Proximal femurs were cut in midcoronal plane and the longitudinal growth plates were examined for structural changes.
  
  
  RESULTS
  The mean NSA measured 7 degrees less than controls in this model using the screw technique, and this difference was statistically significant. Differences between the control and the treated groups did not reach statistical significance for either the plate or the drill group. Differences in ATD were not statistically significant, although there was a trend for larger ATD measurements using the screw technique. Histologically, physeal changes were observed on the operative sides in screw and plate specimens, but not drill specimens, compared with contralateral sham control. The screw specimen exhibited the most severe changes, with growth plate closure over half the section. The plate specimen showed focal loss of the physis across the section, but with no evidence of closure.
  
  
  CONCLUSIONS
  This study builds on previous work that indicates screw hemiepiphysiodesis can effectively alter the shape of the proximal femur, and result in a lower neck-shaft ankle (or lesser valgus). This study suggests that implantation of a screw is likely to be more effective than a plate or drilling procedure in decreasing the NSA in skeletally immature hips.
  
  
  CONCLUSIONS
  If further preclinical, and later clinical, studies demonstrate reproducible efficacy, guided growth of the proximal femur may eventually become a viable option for treatment or prevention of hip deformity in select patients.
authors.affiliation: Department of Orthopaedic Surgery, University of Cincinnati.
authors.forename: Albert
authors.initials: A
authors.lastname: d'Heurle
authors.affiliation: Division of Orthopedics.
authors.forename: James
authors.initials: J
authors.lastname: McCarthy
authors.affiliation: Division of Orthopedics.
authors.forename: David
authors.initials: D
authors.lastname: Klimaski
authors.affiliation: Pathology Department, Cincinnati Children's Hospital, Cincinnati, OH.
authors.forename: Keith
authors.initials: K
authors.lastname: Stringer
mesh_terms: D000818:Animals; D001848:Bone Diseases, Developmental / Q000503:physiopathology; D001860:Bone Plates; D001863:Bone Screws / Q000009:adverse effects*; D002648:Child; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging / Q000254:growth & development / Q000473:pathology / Q000601:surgery*; D006132:Growth Plate / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008297:Male; D023421:Models, Animal; D010027:Osteotomy; D011859:Radiography; D012756:Sheep