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


METHODS
Radiographic and anatomic study.


METHODS
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.


CONCLUSIONS
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.
Department of Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA. Ross.Palmer@ColoState.edu
Ross H
RH
Palmer
Courtney L
CL
Ikuta
Jill M
JM
Cadmus
D000818:Animals; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000662:veterinary*; D004283:Dog Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004285:Dogs; D005269:Femur / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007592:Joint Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000662:veterinary*; D015588:Observer Variation; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011859:Radiography; D015203:Reproducibility of Results; D016037:Single-Blind Method; D014102:Torsion Abnormality / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000662:veterinary*