Agreement and reliability of femoral varus measurements: a comparison of four techniques

TY - CONF

T1 - Agreement and reliability of femoral varus measurements: a comparison of four techniques

AU - Miles, James Edward

AU - Svalastoga, Eiliv Lars

AU - Eriksen, Thomas

PY - 2013

Y1 - 2013

N2 - Three different techniques have been described for measuring femoral varus radiographically in the dog, but how the measurements from these techniques compare is unknown. Further, measurement reliability has only been assessed for one technique. Seven grossly normal right femora were radiographed with the diaphysis positioned horizontally and inclined at both 12.5° and 25° to the horizontal. Radiographs were blinded, randomised and read twice by one observer using ImageJ. Using coordinate data, varus angles were calculated using Microsoft Excel for the three previously reported techniques and a novel method, which we believed would be more reliable. Reliability between readings was assessed using the within-subject standard deviation and repeatability coefficient, and the effect of angulation on varus measurement was assessed using a mixed model ANOVA. Two of the reported techniques varied significantly (P<.05) with femoral angulation, increasing by approximately 2° from horizontal to 25° angulation. At 25° femoral angulation the novel technique differed significantly (nearly 2°, P<.05) from one of the reported techniques, but otherwise results were similar for all methods. Although we hypothesised that the novel method would be more reliable than the other techniques, all values for the within-subject standard deviation and repeatability coefficient were broadly similar. Graphically, the novel method appeared to vary least with femoral angulation in this population, and its simplicity may offer advantages for clinical use. In the absence of an absolute cut-off for surgical intervention for femoral varus, none of the observed differences are necessarily clinically significant.

AB - Three different techniques have been described for measuring femoral varus radiographically in the dog, but how the measurements from these techniques compare is unknown. Further, measurement reliability has only been assessed for one technique. Seven grossly normal right femora were radiographed with the diaphysis positioned horizontally and inclined at both 12.5° and 25° to the horizontal. Radiographs were blinded, randomised and read twice by one observer using ImageJ. Using coordinate data, varus angles were calculated using Microsoft Excel for the three previously reported techniques and a novel method, which we believed would be more reliable. Reliability between readings was assessed using the within-subject standard deviation and repeatability coefficient, and the effect of angulation on varus measurement was assessed using a mixed model ANOVA. Two of the reported techniques varied significantly (P<.05) with femoral angulation, increasing by approximately 2° from horizontal to 25° angulation. At 25° femoral angulation the novel technique differed significantly (nearly 2°, P<.05) from one of the reported techniques, but otherwise results were similar for all methods. Although we hypothesised that the novel method would be more reliable than the other techniques, all values for the within-subject standard deviation and repeatability coefficient were broadly similar. Graphically, the novel method appeared to vary least with femoral angulation in this population, and its simplicity may offer advantages for clinical use. In the absence of an absolute cut-off for surgical intervention for femoral varus, none of the observed differences are necessarily clinically significant.

M3 - Poster

T2 - British Small Animal Veterinary Association Congress 2013

Y2 - 3 April 2013 through 7 April 2013

ER -