Degree of swelling of the medial rectus muscle on CT images to differentiate old from new medial orbital wall fracture.

The aims of this study were to compare the degree of swelling of the medial rectus muscle (MR) in a recent fracture group, an old fracture group, and a normal group and to use this to differentiate old medial orbital wall fracture from recent fracture.We made measurements of the computed tomography images of 43 patients with a recent medial orbital wall fracture (the recent fracture group), 46 patients with depression of the medial wall and who were without a recent trauma history (the old fracture group), and 86 patients who were without any facial injury (the normal group). On the axial view, the width of the MR was measured bilaterally, and the width ratio to the contralateral side was calculated. On the coronal view, the height of the MR was measured bilaterally, and the height ratio to the contralateral side was calculated. The width-to-height ratio was also measured on the involved side.The width ratio of the recent fracture group was 1.42 ± 0.31, and it was significantly higher than that of the old fracture group (1.25 ± 0.15) or the normal group (1.00 ± 0.09). The width ratio of the old fracture group was also significantly higher than that of the normal group. The height ratio of the normal group (1.00 ± 0.04) was significantly higher than that of the recent fracture group (0.91 ± 0.15) or the old fracture group (0.86 ± 0.07). The height ratio of the recent fracture group was also significantly higher than that of the old fracture group (P = 0.043). The width-height ratio of the recent fracture group (0.63 ± 0.23) was significantly higher than that of the old fracture group (0.55 ± 0.09) or the normal group (0.37 ± 0.05). The height-to-width ratio of the old fracture group was also significantly higher than that of the normal group.We think the width ratio of the MR of the injured side to the MR of the contralateral side can be the better parameter to differentiate a recent fracture from an old fracture.