Lunate osteochondroma: a case report.

We report a case of osteochondroma of the lunate. A 16-year-old boy had a 6-year history of irritable snapping of the right wrist associated with numbness of the ipsilateral middle finger. At surgery we found that the median nerve became caught on the lunate osteochondroma while the wrist was extended and slipped over it when the wrist was flexed rapidly, thereby causing a snapping phenomenon. The symptoms disappeared completely after the protruding lesion was excised. Several cases of solitary carpal osteochondroma have been reported previously.