Femoral Neck Shaft Angle and Management of Proximal Femur Fractures: Is the Contralateral Femur a Reliable Template?
Miranda J. Rogers, Taylor L. King, Jaewhan Kim, Temitope F. Adeyemi, Thomas F. Higgins, Travis G. Maak
Abstract
OBJECTIVES: To (1) assess interrater reliability of a novel technique for measurement of neck shaft angle (NSA); (2) use pelvic anteroposterior (AP) radiographs of unaffected hips to assess variability of NSA; and (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 center. PATIENTS/PARTICIPANTS: Four hundred six femora (203 patients) with standing AP pelvis radiographs were selected. Exclusions included lack of acceptable imaging, congenital abnormalities, or prior hip surgery. INTERVENTION: An AP pelvis radiograph in the standing position. MAIN OUTCOME MEASUREMENTS: Bilateral NSA measurements obtained in a blinded fashion between 2 reviewers. Pearson coefficients and coefficient of determination assessed correlations and variability between left and right NSA. Concordance correlation coefficients assessed the interrater reliability between measurements performed by the 2 reviewers. RESULTS: Two hundred three patients (406 femora) were assessed. Male patients had a lower overall NSA mean of 131.56 degrees ± 4.74 than females with 133.61 degrees ± 5.17. There was no significant difference in NSA side-to-side in females (P = 0.18), 0.3 degrees [95% confidence interval (-0.15 to 0.75)], or males (P = 0.68), 0.19 degrees [95% confidence interval (-0.74 to 1.12)]. There was a strong linear relationship between left and right femora (r2 = 0.70). Forty-one percent of patients fell within the 131-135 degrees range bilaterally. Eighty-eight percent of patients had <5 degrees difference in NSA bilaterally and 0% had >10 degrees 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.