Hydroxyapatite-coated external fixation pins in severe wartime fractures: risk factors for loosening

Abstract

Background Many service members returning from Iraq and Afghanistan with severe penetrating extremity injuries are treated with ring fixators and hydroxyapatite (HA) coated pins for limb salvage. The purpose of this study was to determine the pin loosening rate in these severe injuries and to identify factors associated with pin loosening. Methods A retrospective review identified 43 patients with severe open extremity fractures treated with ring external fixation, using 222 HA-coated half pins. A pin was considered loose if the pin site demonstrated erythema, pain, or discharge and concordant radiographs showed 1 mm of radiolucency on both sides of the proximal cortex around the pin. Chi-squared and logistic regression was used to test the association between pin loosening and categorical treatment and injury variables. Results Fifteen (6.8%) pins loosened in nine patients before completion of treatment. Fracture grade, type of tissue traversed, and pins within the zone of injury were associated with pin loosening (P Conclusions Ring external fixation utilizing HA-coated half pins are safe and effective for the treatment of severe wartime fractures. Pins that traverse muscle flaps or the zone of injury increase the risk of pin loosening. Preoperative planning before frame application should minimize pin placement through muscle compartments or mobile soft tissue.