Factors associated with the development of avascular necrosis of the femoral head after non-displaced femoral neck fracture treated with internal fixation

To identify the factors with influence on the development of avascular necrosis of the femoral head (ANFH) in patients with non-displaced femoral neck fractures treated with internal fixation. Retrospective study of cases and controls. We included non-displaced femoral neck fractures treated with internal fixation, and that presented ANFH with a postoperative follow-up of at least 2 years. The baseline variables, active comorbidities of the patients, the time for surgery and the number of screws used for osteosynthesis were recorded. Comparisons were made between the groups, those that presented ANFH and those that did not. By area under the curve, the cut-offs of age and time for surgery were located. An association between sex, active comorbidities and number of screws used and the development of ANFH was not observed. The cut-off points for age and time for surgery were≤69 years and≤43hours, respectively. No significant correlation was observed for the cut-off time for surgery. In the multivariate analysis, age≤69 years was a significant predictor of the development of ANFH (OR 4.6; 95% CI 1.1 to 17.9; P=.028). The patients aged 69 years or younger were at increased risk of developing ANFH after undisplaced femoral neck fracture treated with percutaneous screws.