Like all other bones of the skeleton, the component parts of the pelvic girdle are subject to the occurrence of foci of osteomyelitis. It is found that the forms of osteomyelitis usually resulting from or associated with various kinds of trauma are more prevalent than the orthodox hematogenous forms resulting as thromboembolic phenomena in the course of a general infection (sepsis, pyemia or bacteremia). ANATOMY The pelvic girdle is composed of two main divisions: (1) the sacrum1 and (2) the innominate bone. The sacral vertebrae conform in structure, external form and physiologic function with the other bones of the spine, except that they are fused during adolescence to form the adult entity known as the sacrum. The innominate bone is one of the most irregular bones of the body. The external physical form of its major segments resembles that of all the other bones of the skeleton, including the