title: Unilateral subtalar coalition: contralateral sustentaculum tali morphology.
abstract: OBJECTIVE
  To measure and compare the dimensions of the sustentaculum tali (ST) in pediatric patients with unilateral subtalar coalition to determine if the contralateral side has altered morphology.
  
  
  METHODS
  The institutional review board approved this study, which was HIPAA compliant. Informed consent was waived. Radiology records were reviewed to identify 35 patients with unilateral subtalar coalition undergoing computed tomography (CT) (21 male, 14 female; mean age, 14.54 years) and 33 control patients with triplane fracture (21 male, 12 female; mean age, 13.48 years). CT images were reviewed, and reformatted images through the subtalar joint (on the side opposite the coalition) were created. Anteroposterior measurements of the middle facet (MF) and the ST were recorded by two observers with electronic calipers. The MF/ST ratio and the ST length extending posterior to the MF were calculated. Measurements between groups were compared by using Wald tests based on linear regressions. Inter- and intraobserver variabilities were determined by means of a component of variance model.
  
  
  RESULTS
  The lengths of the MF and ST for the study and control groups were 12.86 and 16.82 mm (P < .001) and 23.83 and 22.06 mm (P = .053), respectively. Intra- and interobserver correlations for both measurements were 0.94 and 0.92 and 0.86 and 0.77, respectively. MF/ST ratio was 0.54 versus 0.76 (P < .001), and ST length extending posterior to the MF was 10.97 versus 5.24 mm (P < .001).
  
  
  CONCLUSIONS
  The MF is smaller and the ST extends further beyond the MF in patients with a contralateral subtalar coalition than in control patients. The morphology of the ST may provide insight into the origins and development of coalitions.
authors.affiliation: Department of Radiology, Children's Hospital Boston, 300 Longwood Ave, Boston, MA 02115, USA. sarah.bixby@childrens.harvard.edu
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Bixby
authors.forename: Delma Y
authors.initials: DY
authors.lastname: Jarrett
authors.forename: Travis
authors.initials: T
authors.lastname: Matheney
authors.forename: Patrick
authors.initials: P
authors.lastname: Johnston
authors.forename: James
authors.initials: J
authors.lastname: Kasser
authors.forename: Paul K
authors.initials: PK
authors.lastname: Kleinman
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted; D012044:Regression Analysis; D012189:Retrospective Studies; D013380:Subtalar Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D013639:Tarsal Bones / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*