Background: The disarranged fat stripe of the pronator quadratus muscle (PQ) on radiographs (the PQ sign) is\nreported to be predictive of subtle bone fractures. This study aimed to report the results of magnetic resonance\nimaging (MRI) study in the patients in whom bone injury was not radiographically detected around the wrist joint,\nand the PQ was sonographically swollen following acute trauma.\nMethods: We evaluated sonographically the PQ of 55 patients who showed normal radiographs following acute\ntrauma. The sonographic appearance of the PQ was checked on both longitudinal and transverse images. On the\nlongitudinal image, the probe was positioned along the flexor carpi radialis tendon. For the transverse image, we\nadopted the image of the same level in which the PQ of the unaffected hand showed maximal thickness. The PQ\nwas considered to be swollen with disproportionate hyperechogenicity and/or thickening compared with the\nunaffected side at least in one of the two images. Of the 55 patients, 25 patients whose PQ was considered to be\nswollen underwent MRI study. PQ thickness in millimeters was retrospectively measured on longitudinal and\ntransverse sonographic images.\nResults: Twenty-three patients (92.0%) had occult bone injury, and two adult patients (8.0%) showed only wrist\njoint effusion on MRI. Among these 23, the distal radius was the most frequent location of the occult bone injury\n(20 patients; 9 [36.0%] with an occult fracture line and 11 [44.0%] with bone bruising). In longitudinal image, the\nmean value of the PQ thickness of affected hands was 6.2 (3.7ââ?¬â??9.6 mm; standard deviation [SD], 1.5) and that of\nunaffected hands was 4.5 (2.3ââ?¬â??6.7 mm; SD, 1.2), respectively. In transverse image, that of dominant and nondominant\nhands was 7.6 (4.6ââ?¬â??13.2 mm; SD, 2.0) and 5.5 (3.6ââ?¬â??7.5 mm; SD, 1.1), respectively. The mean difference in PQ thickness\nbetween affected and unaffected hands was 1.7 (0.1ââ?¬â??5.0 mm; SD, 1.1) in longitudinal image and 2.0 (0.3ââ?¬â??6.8 mm;\nSD, 1.7) in transverse image.\nConclusions: Sonographic swelling of the PQ might be indicative of occult bone injury in patients with normal\nradiographs following acute trauma.
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