BACKGROUND: The indications of non-operative treatment of undisplaced femoral neck fractures are controversial. The objective of this study was to assess whether two computed tomography (CT) parameters, the femoral neck impaction angle (IA) and the femoral neck posterior tilt angle (PTA), were effective in predicting the risk of secondary displacement after non-operative treatment of Garden I femoral neck fractures in patients aged 65 years or over. HYPOTHESIS: The working hypotheses were that the IA in the coronal plane and PTA in the axial plane predicted secondary displacement after non-operative treatment of Garden I femoral neck fractures, could be reproducibly and reliably measured on CT scans, and could serve to identify Garden I fractures at risk for secondary displacement after non-operative treatment. METHODS: Forty-nine patients aged 65 years or over with Garden I fractures treated non-operatively were included in a prospective single-centre study. CT images were used to measure the IA as the position of the fracture line relative to the femoral head in the coronal plane and the PTA as the position of the femoral head centre relative to the femoral neck axis in the axial plane. RESULTS: After non-operative treatment, secondary displacement occurred in 22 (45%) patients. The PTA was not significantly different between the groups with vs. without secondary displacement (p=0.62). IA values≤135° were significantly associated with secondary displacement (odds ratio, 11.73; 95% confidence interval [95%CI], 3.04-45.28; p=0.004). An IA≤135° was 72.73% sensitive and 81.48% specific for predicting secondary displacement. IA measurement was reproducible, with intra-class and inter-class Cohen's kappa values of 0.94 (95%CI, 0.90-0.97) and 0.9011 (95%CI, 0.83-0.94), respectively. DISCUSSION: The IA measured on CT images may hold promise for identifying Garden I hip fractures at high risk for secondary displacement after non-operative treatment. IA measurement is reproducible and reliable and may help to determine the indications of non-operative treatment. LEVEL OF EVIDENCE: II, prospective cohort study.
BACKGROUND: The indications of non-operative treatment of undisplaced femoral neck fractures are controversial. The objective of this study was to assess whether two computed tomography (CT) parameters, the femoral neck impaction angle (IA) and the femoral neck posterior tilt angle (PTA), were effective in predicting the risk of secondary displacement after non-operative treatment of Garden I femoral neck fractures in patients aged 65 years or over. HYPOTHESIS: The working hypotheses were that the IA in the coronal plane and PTA in the axial plane predicted secondary displacement after non-operative treatment of Garden I femoral neck fractures, could be reproducibly and reliably measured on CT scans, and could serve to identify Garden I fractures at risk for secondary displacement after non-operative treatment. METHODS: Forty-nine patients aged 65 years or over with Garden I fractures treated non-operatively were included in a prospective single-centre study. CT images were used to measure the IA as the position of the fracture line relative to the femoral head in the coronal plane and the PTA as the position of the femoral head centre relative to the femoral neck axis in the axial plane. RESULTS: After non-operative treatment, secondary displacement occurred in 22 (45%) patients. The PTA was not significantly different between the groups with vs. without secondary displacement (p=0.62). IA values≤135° were significantly associated with secondary displacement (odds ratio, 11.73; 95% confidence interval [95%CI], 3.04-45.28; p=0.004). An IA≤135° was 72.73% sensitive and 81.48% specific for predicting secondary displacement. IA measurement was reproducible, with intra-class and inter-class Cohen's kappa values of 0.94 (95%CI, 0.90-0.97) and 0.9011 (95%CI, 0.83-0.94), respectively. DISCUSSION: The IA measured on CT images may hold promise for identifying Garden I hip fractures at high risk for secondary displacement after non-operative treatment. IA measurement is reproducible and reliable and may help to determine the indications of non-operative treatment. LEVEL OF EVIDENCE: II, prospective cohort study.