A Predictive Method for the Femoral Head Necrosis by the Observation of the Bleeding from the Cannulated Screw in Patients of the Femoral Neck Fractures

Purpose: The aim of this study was to examine the validity of using cannulated screws as a method for predicting avascular necrosis of the femoral head after a fixation of fractures in patients with femoral neck fractures. Materials and Methods: Between March 1999 and January 2001, 44 patients with a femoral neck fracture that had been fixed with cannulated screws were enrolled in this study. The follow up period was more than 25 months and the mean age of the patients was 51 years (range, 18 to 76 year). Blood drainage in the holes of the screw head was checked. There were 38 cases in the bleeding group, and 6 cases in the non-bleeding group. The development of head necrosis was evaluated using plain radiography. The validity of the relationship between the two groups and head necrosis was evaluated by the sensitivity, specificity, the positive predictive value, and the negative predictive value. Results: An avascular necrosis of the femoral head developed in 7 cases (16%). Only one of the 38 patients in the bleeding group developed head necrosis (2.6%). However, all those in the non-bleeding group developed head necrosis (100%). The sensitivity was 86%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 97%. Conclusion: Bleeding from holes in the cannulated screws is a simple and accurate perfusion assessment for predicting the development of an avascular necrosis of the femoral head after a femoral neck fracture.