Fig. 4

BPOP arising from the distal ulnar diaphysis. On X-rays, frontal (a) and lateral (b) views show a mineralized mass, which is contiguous to the distal diaphysis of the ulna. On axial T2-weighted MRI sequence (c), the mass is hyperintense with higher signal at the periphery representing cartilage covering (dashed arrow). Longitudinal B-mode ultrasound image (d) depicts a calcified mass, which is contiguous to the palmar aspect of the ulna and impinges on the flexor muscles. Axial B-mode ultrasound image (e) shows a thin hypoechoic layer (calipers) superficial to the mineralized mass, which is in keeping with cartilage covering. No increased vascularity is seen on power Doppler imaging (f). After biopsy, surgical resection was performed and BPOP was pathologically proven. White arrow points at BPOP in all images