Osteoid osteoma - phalanx

Though CT is an excellent tool for the diagnosis of osteoid osteomas, as seen in last week's post, high-resolution MRI is also usually diagnostic.

This 10-years old boy had severe pain in the tip of the thumb. The plain radiograph (Fig. 1) showed ill-defined sclerosis anteriorly, but an obviously nidus was not seen. An MRI was then performed (Figs. 2, 3), which clearly showed the nidus (arrows). The lesion was then excised and the patient improved immediately.