Caudal foot placement superior to toe elevation for navicular palmaroproximal-palmarodistal-oblique image quality

Palmaroproximal-palmarodistal oblique (PaPr-PaDiO) radiographs are regularly obtained for a full evaluation of the navicular bone (NB). Despite their routine use, different acquisition techniques are described.

To determine optimal foot placement and beam angle for obtaining PaPr-PaDiO views.

In vitro experiment.

A convenience sample of 26 disarticulated forelimbs were placed in six different positions using a leg press to mimic the weight-bearing position. In each position, navicular PaPr-PaDiO images were obtained with eight different beam angles. The resulting 1248 radiographs were graded for their diagnostic quality and the compacta spongiosa demarcation of the NB.

Diagnostic quality and compacta-spongiosa demarcation was graded higher for feet positioned caudally and angle between 40° and 45°. Elevation of the toe significantly decreased the NB palmar border angle (elevated mean: 40.66, SD: 4.46, non-elevated mean: 42.06, SD: 4.70) (P < .01), but seemed to have no obvious positive influence on radiographs.

Using disarticulated legs could only mimic positions but, using a press, weight-bearing positions were replicated as closely as possible. The use of a convenience sample makes the results of the study exploratory only.

Caudal foot placement seems to improve the image quality of the navicular PaPr-PaDiO view. The widely used standard beam angle of 45° appears to be the favourable angle for acquisition with a varied range of -5°. Elevation of the toe, standard in most commercially available navicular skyline cassette holders, does not influence the obtained image quality.