Comparison of Femoral Angulation Measurement Between Radiographs and Anatomic Specimens Across a Broad Range of Varus Conformations

Authors

  • Ross H. Palmer DVM, MS, Diplomate ACVS,

    Corresponding author
    • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO
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  • Courtney L. Ikuta DVM,

  • Jill M. Cadmus BS


  • Funding and materials provided by the Colorado State University—College of Veterinary Medicine & Biomedical Sciences Research Council and IMEX Veterinary, Inc.

  • Presented in part at the 35th Annual Conference of the Veterinary Orthopedic Society, Big Sky, MT, March 9–14, 2008.

Corresponding Author

Ross Palmer, DVM, MS, Diplomate ACVS, Department of Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Colorado State University, Fort Collins, CO 80523

E-mail: Ross.Palmer@ColoState.edu

Abstract

Objective

To determine if measurement of anatomic lateral distal femoral angle (aLDFA) from radiographs is valid across a broad range of femoral varus conformations.

Study Design

Radiographic and anatomic study.

Sample Population

Large breed canine cadavers (n = 5) and femora (n = 10).

Methods

Cadavers were held in dorsal recumbency and 8 craniocaudal radiographic projections made of each femur: 1 image pre- and postosteotomy and at each of 6 progressive levels of induced distal varus deformity. Femurs were collected. Three blinded examiners independently measured varus on each radiograph (R-aLDFA) and femoral specimen (S-aLDFA) on 3 separate occasions. Intra- and interobserver variance in R-aLDFA and S-aLDFA measurements were determined. The strength of relationship between R-aLDFA and S-aLDFA and positive and negative predictive values for R-aLDFA were calculated.

Results

Intra- and interobserver variance in R-aLDFA (mean, 0.54% and 0.40%, respectively) and S-aLDFA (mean, 0.43% and 0.41%, respectively) were acceptable. The strength of relationship between R-aLDFA and S-aLDFA (adjusted R2 = 78.2%) was marginally below the acceptance criterion of 80%. Using aLDFA ≥ 102° as an indication for corrective femoral osteotomy, radiography was successful in correctly identifying corrective femoral osteotomy candidates (positive predictive value) and noncandidates (negative predictive value) 72% and 96% of the time, respectively.

Conclusion

R-aLDFA did not reach the desired accuracy for femoral varus measurement across the range of conformations evaluated.

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