Computed tomographic evaluation of the position of the leg for mortise radiographs

We Investigated the most advantageous internal rotation angle of the leg fo r mortise radiographs. One hundred and twenty-eight feet of 64 healthy volu nteers with no histories of ankle or foot pathology (72 feet of 36 males, 5 6 feet of 28 females) were examined. The subjects had an average age of 29 years (range, 19 to 51 years), average height of 167 cm (range, 157 to 181 cm), and average foot length of 25 cm (range, 23 to 27 cm). We obtained a p lain axial view at the level of the central patella and 5 mm proximal to th e tibial plafond using computed tomography, and investigated the inclinatio n angle of the distal tibiofibular joint to a horizontal plane, regarding i t as a mortise angle. The mean mortise angle was 19.1 +/- 5.0 degrees. Howe ver, two peaks were observed at around 15 degrees and 20 degrees. This indi cated that the mean mortise angle of the males was 21.2 +/- 4.6 degrees, an d the mean mortise angle of the females was 16.4 +/- 4.1 degrees with a sig nificant difference between the males and the females' mortise angle (P < 0 .0001). There was no correlation between the mortise angle and the height ( P = 0.899 in the males, and P = 0.871 in the females), nor between the mort ise angle and the foot length (P = 0.359 in the males, and P = 0.512 in the females). Therefore, we concluded that the internal rotation angle of the leg for mortise radiography should be generally set up at about 20<degrees> on males and 15 degrees on females.