Computed Tomography Overestimates Roentgenographic Posterior Tilt in Geriatric Garden I/II Femoral Neck Fractures.

INTRODUCTION: Current best practice is to consider primary arthroplasty for elderly patients with a Garden I/II femoral neck fracture (FNF) when posterior tilt measures greater than 20° on the lateral radiograph. Although this evidence-based threshold stemmed from plain radiographs, clinicians similarly use it using CT when available. The correspondence of posterior tilt measured on radiograph versus CT is unknown.

METHODS: Patients older than 65 years presenting with a Garden I/II FNF during a 6.5-year period (January 2018 to August 2024) were retrospectively reviewed. Patients without concomitant radiograph and CT of the affected hip or with inadequate radiographs were excluded. Posterior tilt of the FNF was measured on lateral radiographs (PT-XR) and compared with CT (PT-CT).

RESULTS: After review of 1,244 records, a total of 100 patients averaging 82 ± 8 years old met inclusion criteria. Twenty-nine patients underwent internal fixation and 71 hemiarthroplasty. On average, PT-CT was larger than PT-XR (14° vs. 9°; P < 0.001). Lateral radiographs identified two patients (2%) with a posterior tilt ≥20°, while CT identified 17 (17%). For the 15 patients in whom increased posterior tilt was identified only by CT, the mean difference between PT-XR and PT-CT was 24 ± 15°.

CONCLUSION: In patients with Garden I/II FNFs, CT often generates larger posterior tilt measurements than plain radiographs. Using CT, an additional 15% of these patients are identified as having posterior tilt ≥20°. Therefore, advanced imaging of Garden I/II FNFs objectively increases the number of fractures considered too unstable for internal fixation. However, its use as an indication for primary arthroplasty is not yet evidence based.

LEVEL OF EVIDENCE: III.