J Orthopaed Traumatol (2010) 11:251–255 253 Fig. 3 Coronal magnetic resonance imaging (MRI) T1 turbo spin echo (TSE) (a), MR angiography (b), and digital angiography (c). MR angiography (b) identiﬁes the pseudoaneurysm arising from the compressed brachial artery, with extravasation of contrast medium into the mass, well demonstrated also by the angiography (c) Fig. 4 Axial magnetic resonance imaging (MRI) T2 (a), proton- density fat saturation (PD fat-sat) (b), T1 turbo spin echo (TSE) (c), T1-TSE fat-sat (d) sequences of the osteochondroma underlying the pseudoaneurysm. Note hyperintensity of the medulla adjacent to the lesion on PD sequences (b) and enhancement of the medulla itself after contrast media (arrow) (d) 123