The Measurement of the Lateral Center-Edge Angle Is Underestimated on Radiographs Compared With 3-Dimensional Computed Tomography

Abstract

Purpose

To determine if there is a significant difference using femoral heads (FHs) as an anatomic horizon when measuring the lateral center-edge angle (LCEA) compared to floor, acetabular teardrops, and ischial tuberosities (ITs) and to determine their accuracy by comparing to a computed tomography (CT) scan with commercially available software.

Methods

Between June 2019 and May 2020, patients with preoperative supine anteroposterior pelvis radiographs and CT scans were included and retrospectively analyzed. The LCEA was measured on all preoperative supine anteroposterior pelvis radiographs 4 times per hip, using the 4 methods. The 4 anatomic horizons used to measure LCEA were compared to each other to determine statistically significant difference. The LCEA measured in the CT scan at the 12-o’clock position was used to compare and determine radiographs’ LCEA accuracy.

Results

Ninety-six patients (100 hips) met the inclusion criteria. Sixty-two were women (65%), and the mean age was 35.2 ± 15 years. The mean value for LCEA in CT was 32.2 and 31.1 for the 4 anatomic horizons on x-ray (P < .001). The lowest mean difference between CT scan and x-ray was obtained using the FHs (2.3 ± 2.4). Less mean difference was obtained between FHs and ITs (1.0 ± 0.8).

Conclusions

In this study, radiographic measurements underestimated LCEA compared with those from CT scans. Using the FHs as an anatomic horizon on radiographs was a more accurate method to measure LCEA than using acetabular teardrops, ITs, or floor. While this difference is statistically significant, it is not likely to be clinically significant.

Clinical Relevance

Assessment of acetabular coverage is an essential aspect of diagnosing and managing hip pathologies. One of the methods used for this is the LCEA measurement, which is based on a radiographic analysis of the hip joint. It is important to compare the measurements using different horizons and increasingly sophisticated imaging modalities to provide the most accurate information to guide clinical decision making.