Sagittal deformity of Garden type I and II geriatric femoral neck fractures is frequently misclassified by lateral radiographs.

ABSTRACT

The objective of this study was to determine the validity and inter-rater reliability of radiographic assessment of sagittal deformity of femoral neck fractures. Design: This is a retrospective cohort study. Setting: Level 1 trauma center. Patients/Participants: Thirty-one patients 65 years or older who sustained low-energy, Garden type I/II femoral neck fractures imaged with biplanar radiographs and either computed tomography or magnetic resonance imaging were included. Main Outcome Measurements Preoperative sagittal tilt was measured on lateral radiographs and compared with the tilt identified on advanced imaging. Fractures were defined as "high-risk" if posterior tilt was ≥20 degrees or anterior tilt was >10 degrees. Results: Of 31 Garden type I/II femoral neck fractures, advanced imaging identified 10 high-risk fractures including 8 (25.8%) with posterior tilt ≥20 degrees and 2 (6.5%) with anterior tilt >10 degrees. Overall, there was no significant difference between sagittal tilt measured using lateral radiographs and advanced imaging (P = 0.84), and the 3 raters had good agreement between their measurements of sagittal tilt on lateral radiographs (interclass correlation coefficient 0.79, 95% confidence interval [0.65, 0.88], P < 0.01). However, for high-risk fractures, radiographic measurements from lateral radiographs alone resulted in greater variability and underestimation of tilt by 5.2 degrees (95% confidence interval [-18.68, 8.28]) when compared with computed tomography/magnetic resonance imaging. Owing to this underestimation of sagittal tilt, the raters misclassified high-risk fractures as "low-risk" in most cases (averaging 6.3 of 10, 63%, range 6 - 7) when using lateral radiographs while low-risk fractures were rarely misclassified as high-risk (averaging 1.7 of 21, 7.9%, range 1 - 3, P = 0.01). Conclusions: Lateral radiographs frequently lead surgeons to misclassify high-risk sagittal tilt of low-energy femoral neck fractures as low-risk. Further research is necessary to improve the assessment of sagittal plane deformity for these injuries. Level of Evidence Level IV diagnostic study.