Diagnostic value of the radiographic muscle-to-bone thickness ratio between the pronator quadratus and the distal radius at the same level in undisplaced distal forearm fracture

PurposeTo investigate the value of the muscle-to-bone ratio (MBR), which is the ratio between the maximum pronator quadratus thickness (mPQT) and the distal radial thickness (DRT) at the same level, in comparison with mPQT in the diagnosis of undisplaced fractures in distal forearm (FDF) on radiographs.Material and methodsThis study was conducted with 210 wrists of 210 volunteers (79 male, 131 female) and 106 wrists of 106 patients with acute undisplaced FDF (53 male, 53 female). The mPQT was measured on lateral radiographs, and the MBR was calculated for each wrist.ResultsThe mean mPQT (7.37 ± 1.99 mm) and MBR (0.55 ± 0.15) in the fracture group were significantly larger than those (4.70 ± 1.42 mm and 0.31 ± 0.09) in the control group respectively (all P < 0.05). Sexual differences of mPQT were found in both control and fracture groups (all P < 0.05). There were no gender differences of MBR in either control or fracture group (all P > 0.05). ROC analysis revealed that the discriminating efficacy of MBR was significantly superior to that of mPQT (P < 0.01). The most optimal diagnostic discrimination was obtained by a MBR cut-off value of 0.4.ConclusionsThe MBR can be used as a new index for the diagnosis of undisplaced FDF, as well as a complementary means to detect occult fractures. If the MBR is larger than 0.4 in a patient with suspected or occult FDF, a further MRI examination will be justifiably needed.