IMPROVING THE DETECTION OF RADIOGRAPHICALLY OCCULT ANKLE FRACTURES - POSITIVE PREDICTIVE VALUE OF AN ANKLE JOINT EFFUSION

Objective: To assess the value of an ankle effusion on plain radiograp hs as a predictor of radiographically occult fracture after acute ankl e trauma. Patients: Consecutive patients with acute ankle trauma and r adiographic evidence of an ankle joint effusion, Patients were exclude d if ankle trauma was sustained more than 48 h previously or if a frac ture was visible on initial photographs Methods: All subjects (n = 26) underwent computed tomography (CT) of the ankle in sagittal and coron al planes, Ankle effusion size was measured from initial lateral ankle radiographs. Results: Twelve patients (46%) had radiographically occu lt fractures identified with CT, Fracture sites included: posterior or lateral malleoli (n = 4), calcaneus (n = 1), or talus (n = 7), Ankle effusion size was 11.2 mm in the group without fracture and 17.1 mm in the group with fracture (P < 0.0001), The positive predictive value o f an effusion 15 mm or greater was 83%. CT detected significant soft-t issue injuries in four (15%) patients including peroneal retinaculum t ear (n = 1), anterior talofibular ligament avulsion (n = 1), and tears of the peroneus longus (n = 1) and tibialis posterior (n = 1) tendons . Conclusions: The presence of a large ankle effusion of radiographs a fter acute ankle trauma suggests an underlying fracture, An ankle effu sion of greater than or equal to 15 mm is a reasonable threshold to pr ompt additional imaging, Computed tomography provides good visualizati on of subtle bone injuries and may detect clinically imported soft-tis sue injuries.