Normal Range of Humeral Head Positioning on the Glenoid on Magnetic Resonance Imaging: Validation through Comparison of Computed Tomography and Magnetic Resonance Imaging

Abstract

Background: To determine the normal range of humeral head positioning on magnetic resonance imaging (MRI). Methods: We selected normal subjects (64 patients; group A) to study the normal range of humeral head positioning on the glenoid by MRI measurements. To compare the MRI measurement method with the computed tomography (CT), we selected group B (70 patients) who underwent both MRI and CT. We measured the humeral-scapular alignment (HSA) and the humeral-glenoid alignment (HGA). Results: The HSA in the control group was $1.47{\pm}1.05mm$, and the HGA with and without reconstruction were $1.15{\pm}0.65mm$ and $1.03{\pm}0.59mm$, respectively, on MRI. In the test group, HSA was $2.67{\pm}1.47mm$ and HGA with and without reconstruction was $1.58{\pm}1.16mm$ and $1.49{\pm}1.08mm$, on MRI. On CT, the HSA was $1.72{\pm}1.01mm$, and HGA with and without reconstruction were $1.54{\pm}0.96mm$ and $1.59{\pm}0.93mm$, respectively. HSA was significantly different according to image modality (p=0.0006), but HGA was not significantly different regardless of reconstruction (p=0.8836 and 0.9234). Conclusions: Although additional CT scans can be taken to measure decentering in patients with rotator cuff tears, reliable measurements can be obtained with MRI alone. When using MRI, it is better to use HGA, which is a more reliable measurement value based on the comparison with CT measurement (study design: Study of Diagnostic Test; Level of evidence II).

Fig. 1. Reconstruction to scapular axis of normal magnetic resonance imaging (MRI). After setting the axial, coronal, and sagittal views of the MRI to be visible at the same time, we reconstructed the plane passing through the angular inferior, trigonum scapulae, and glenoid center of the scapular using the image analysis software (RadiAnt DICOM viewer). The scapular axis, which is perpendicular to this plane and is the line representing this plane in the axial plane passing through the glenoid center, was obtained.

Fig. 2. Measuring of humeral head center. (A) Humeral-scapular alignment. The distance between the center of the circle and the line passing through the scapular axis. (B) Humeral-glenoid alignment. The distance between the center of the circle and the perpendicular line passing through the center of the line between the glenoid plane.

Table 1. Normal Range of Humeral Head Positioning (Group A)

Table 2. Comparison between CT and MRI Measurement (Group B)