Obturator internus pyomyositis. A case report.

Pyomyositis appears to be increasing in prevalence in temperate climates, and often the orthopaedist is integral in the decision making and care of these patients. This is the first reported case of spontaneous bacterial pyomyositis involving the obturator internus muscle. Deep pelvic infections involving the psoas, iliacus, piriformis, and obturator internus can be a significant cause of morbidity and mortality. The infection subsequently may exit the pelvis, and conceivably may progress to a septic hip, bursitis, or lower extremity cellulitis. Improvements in noninvasive imaging such as ultrasound, computed tomography, and magnetic resonance imaging have produced finer resolution of tissue planes. Because of the pathology's deep location within the pelvis of the patient described here, all 3 tests were integral in the surgical planning, exposure, and proper diagnosis. Although 95% of pyomyositis cases are caused by Staphylococcus aureus, cases of pyomyositis with negative cultures have been described. Consideration should be made of disseminated Neisseria gonorrhoeae in sexually active individuals, and cultures should include Thayer-Martin agar to decrease the likelihood of a false-negative culture result.