Morphology and histology of the collapsed lunate in advanced kienböck disease.

Morphological and histological changes of 24 collapsed lunates in advanced Kienböck disease were investigated. Articular cartilage of a collapsed lunate were consistently attenuated or disappeared. The proximal articular cartilage facing the radius is generally more affected than the distal articular cartilage facing the capitate. There was one major fracture in addition to multiple minor fractures in the collapsed lunate. Fracture patterns were classified into three types according to the directions of major fracture, namely horizontal type, dual oblique type, and vertical type. There were viable and necrotic areas in the collapsed lunate. Active new bone formation was observed at the junction between the viable and necrotic bone area of the collapsed lunate in advanced Kienböck disease.