Coracoacromial pins to augment external fixation of the upper humerus.

present as soft-tissue masses; they may be painful and progressively enlarge. Radiography may show some calci fication, but bony erosion is rare (Sim et al 1977). The lesion can be clearly defined by CT. Extra-articular synovial chondromatosis has a benign clinical course (Dahlin and Salvador 1974), but in unusual locations it may be misdiagnosed as a soft-tissue chon drosarcoma. Factors which may cause confusion include extension of the mass into adjacent bone and evidence of chondrocytic activity with some enlarged nuclei. The diag nosis is made by the synovial origin of the cartilaginous proliferation. Sim et al (1977) emphasised the importance of recognising the synovial origin of these lesions. Local excision is usually effective; accurate histological diagnosis can avoid radical surgery.