Early radiographic differentiation of infantile tibia vara from physiologic bowing using the femoral-tibial ratio

James J. McCarthy, Randal R. Betz, Andrew Kim, Jon Davids, Richard S. Davidson

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

The authors hypothesized that the ratio of the femoral to tibial metaphyseal-diaphyseal angles (femoral-tibial ratio [FTR]) more accurately differentiates physiologic bowing from infantile tibial vara than the tibial metaphyseal-diaphyseal angle (TMDA). The purpose of this study was threefold: to determine the false-negative and false-positive error rate of the FTR and TMDA; to determine to the effect of rotation on the FTR and TMDA; and to determine the reliability of the FTR and TMDA measurements. An FTR < 1 resulted in a false-negative error rate of 10% and a false-positive error rate of 7%, whereas a TMDA > 13° resulted in a false-negative error rate of 23% and a false-positive error rate of 10%. The difference between internal and external rotation was not significant for the FTR, whereas it was for the TMDA. The FTR was found to have good interobserver and intraobserver reliability (0.78 and 0.98, respectively).

Original languageEnglish (US)
Pages (from-to)545-548
Number of pages4
JournalJournal of Pediatric Orthopaedics
Volume21
Issue number4
DOIs
StatePublished - 2001
Externally publishedYes

Keywords

  • Blount disease
  • Femoral metaphyseal-diaphyseal angle
  • Infantile tibia vara
  • Physiologic bowing

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Surgery
  • Orthopedics and Sports Medicine

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