Abstract
BackgroundThe disarranged fat stripe of the pronator quadratus muscle (PQ) on radiographs (the PQ sign) is reported to be predictive of subtle bone fractures. This study aimed to report the results of magnetic resonance imaging (MRI) study in the patients in whom bone injury was not radiographically detected around the wrist joint, and the PQ was sonographically swollen following acute trauma.MethodsWe evaluated sonographically the PQ of 55 patients who showed normal radiographs following acute trauma. The sonographic appearance of the PQ was checked on both longitudinal and transverse images. On the longitudinal image, the probe was positioned along the flexor carpi radialis tendon. For the transverse image, we adopted the image of the same level in which the PQ of the unaffected hand showed maximal thickness. The PQ was considered to be swollen with disproportionate hyperechogenicity and/or thickening compared with the unaffected side at least in one of the two images. Of the 55 patients, 25 patients whose PQ was considered to be swollen underwent MRI study. PQ thickness in millimeters was retrospectively measured on longitudinal and transverse sonographic images.ResultsTwenty-three patients (92.0%) had occult bone injury, and two adult patients (8.0%) showed only wrist joint effusion on MRI. Among these 23, the distal radius was the most frequent location of the occult bone injury (20 patients; 9 [36.0%] with an occult fracture line and 11 [44.0%] with bone bruising). In longitudinal image, the mean value of the PQ thickness of affected hands was 6.2 (3.7–9.6 mm; standard deviation [SD], 1.5) and that of unaffected hands was 4.5 (2.3–6.7 mm; SD, 1.2), respectively. In transverse image, that of dominant and nondominant hands was 7.6 (4.6–13.2 mm; SD, 2.0) and 5.5 (3.6–7.5 mm; SD, 1.1), respectively. The mean difference in PQ thickness between affected and unaffected hands was 1.7 (0.1–5.0 mm; SD, 1.1) in longitudinal image and 2.0 (0.3–6.8 mm; SD, 1.7) in transverse image.ConclusionsSonographic swelling of the PQ might be indicative of occult bone injury in patients with normal radiographs following acute trauma.
Highlights
The disarranged fat stripe of the pronator quadratus muscle (PQ) on radiographs is reported to be predictive of subtle bone fractures
Moosikasuwan [3] speculated that this sign would be false-negative in such situations as the fractured level differs from the level of the PQ, the fascia covering the muscle is torn, or the radiograph is of poor quality
Annamalai and Raby [5] reported that the sensitivity and specificity of the PQ sign were even less, with values of 26% and 70%, respectively in the radiographically occult fractures detected on follow-up magnetic resonance imaging (MRI)
Summary
The disarranged fat stripe of the pronator quadratus muscle (PQ) on radiographs (the PQ sign) is reported to be predictive of subtle bone fractures. This study aimed to report the results of magnetic resonance imaging (MRI) study in the patients in whom bone injury was not radiographically detected around the wrist joint, and the PQ was sonographically swollen following acute trauma. MacEwan [1] reported the usefulness of the radiolucent plane overlying the pronator quadratus (PQ) seen on the lateral radiograph of the distal forearm in patients with undisplaced fractures of the radius and ulna, namely the “PQ sign”, which is an anterior bowing or obliteration of the stripe of fat plane paralleling between the PQ and flexor digitorum profundus muscle. Annamalai and Raby [5] reported that the sensitivity and specificity of the PQ sign were even less, with values of 26% and 70%, respectively in the radiographically occult fractures detected on follow-up magnetic resonance imaging (MRI). Ultrasonography has great benefits in its noninvasiveness, low cost, portability and rapidity which make it easier to use in the outpatient clinic and emergency room; one major disadvantage of this imaging modality is the inability in qualitative diagnosis of bone marrow
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