Source of Support: None, Conflict of Interest: None
We carried out tetracycline double labeling with a definite dosage protocol in 21 patients, mean age 45 (10-65) years, with displaced intracapsular fracture neck of femur who were admitted untreated later than 3(3-39) weeks after injury. Undecalcified sections of bone samples from the femoral head were studied under fluorescent microscope and compared with findings of avascular necrosis on conventional radiographs. The presence of bands of fluorescence along the trabeculae were taken as evidence of viability of the head of femur. The radiographical criteria used were according to those laid down by Cohen et al (1990). Eleven femoral heads showed evidence of avascular necrosis in the initial radiographs and nine of these did not take up the tetracycline label. The sensitivity of the radiographs of avascular necrosis was 82 percent while the specificity was 80 percent. The conventional radiograph offers an economical yet sensitive method of diagnosis of avascular necrosis of the femoral head following fracture neck of femur in patients who report later than 3 weeks of injury.