Symptomatic hip impingement due to exostosis associated with supra-acetabular pelvic external fixator pin.

Expedient stabilization of unstable pelvic fractures has been shown to significantly reduce morbidity and mortality in the polytrauma patient. Application of a pelvic external fixator is one of the methods used to provide effective pelvic stability. However, pelvic external fixators are not without drawbacks. While pin tract infections and pin loosening are frequent complications, we describe a unique complication consisting of the formation of a symptomatic exostosis at the supra-acetabular pin site in a 35-year-old male with a pelvic fracture. To our knowledge this is the first description of hip impingement due to reactive bone formation secondary to a supra-acetabular pelvic external fixation pin. The impinging bone was completely excised utilizing the anterior approach to the hip. A 40° improvement in the patient's hip flexion range of motion was noted after exostosis excision.