Femoral Neck Shaft Angle and Management of Proximal Femur Fractures: Is the Contralateral Femur a Reliable Template?

OBJECTIVES To: [1] Assess inter-rater reliability of a novel technique for measurement of NSA; [2] Use pelvic anteroposterior (AP) radiographs of unaffected hips to assess variability of NSA; [3] Evaluate the side-to-side variability of NSA to determine reliability of using the contralateral hip as a template. DESIGN Retrospective cohort study. SETTING Academic Level 1 regional trauma centerPatients/Participants: 406 femora (203 patients) with standing AP pelvis radiographs were selected. Exclusions included lack of acceptable imaging, congenital abnormalities, or prior hip surgery. INTERVENTION An anteroposterior pelvis radiograph in the standing position. MAIN OUTCOME MEASUREMENTS Bilateral NSA measurements obtained in a blinded fashion between two reviewers. Pearson coefficients and coefficient of determination assessed correlations and variability between left and right NSA. Concordance correlation coefficients assessed the inter-rater reliability between measurements performed by the two reviewers. RESULTS 203 patients (406 femora) were assessed. Male patients had a lower overall NSA mean of 131.56° ± 4.74 than females with 133.61° ± 5.17. There was no significant difference in NSA side to side in females (p=0.18, 0.3° (95% CI [-0.15, 0.75)) or males (p=0.68, 0.19° (95% CI [-0.74, 1.12)). There was a strong linear relationship between left and right femora (r2=0.70). 41% of patients fell within the 131-135° range bilaterally. 88% of patients had 10° difference. CONCLUSIONS There is no significant variability between bilateral femora in males and females. Use of this measurement method and contralateral NSA for proximal femur fracture planning is supported. LEVELS OF EVIDENCE Level III. See Instructions for Authors for a complete description of levels of evidence.