Assessment of glenoid inclination on routine clinical radiographs and computed tomography examinations of the shoulder.
BACKGROUND
Accurate assessment of glenoid inclination is of interest for a variety of conditions and procedures. The purpose of this study was to develop an accurate and reproducible measurement for glenoid inclination on standardized anterior-posterior (AP) radiographs and on computed tomography (CT) images.


METHODS
Three consistently identifiable angles were defined: Angle α by line AB connecting the superior and inferior glenoid tubercle (glenoid fossa) and the line identifying the scapular spine; angle β by line AB and the floor of the supraspinatus fossa; angle γ by line AB and the lateral margin of the scapula. Experimental study: these 3 angles were measured in function of the scapular position to test their resistance to rotation. Conventional AP radiographs and CT scans were acquired in extension/flexion and internal/external rotation in a range up to ±40°. Clinical study: the inter-rater reliability of all angles was assessed on AP radiographs and CT scans of 60 patients (30 with proximal humeral fractures, 30 with osteoarthritis) by 2 independent observers.


RESULTS
The experimental study showed that angle α and β have a resistance to rotation of up to ±20°. The deviation from neutral position was not more than ±10°. The results for the inter-rater reliability analyzed by Bland-Altman plots for the angle β fracture group were (mean ± standard deviation) -0.1 ± 4.2 for radiographs and -0.3 ± 3.3 for CT scans; and for the osteoarthritis group were -1.2 ± 3.8 for radiographs and -3.0 ± 3.6 for CT scans.


CONCLUSIONS
Angle β is the most reproducible measurement for glenoid inclination on conventional AP radiographs, providing a resistance to positional variability of the scapula and a good inter-rater reliability.
Department of Orthopedic Surgery, University Hospital, Balgrist, Zürich, Switzerland.
Alexander
A
Maurer
Sandro F
SF
Fucentese
Christian W A
CW
Pfirrmann
Stephan H
SH
Wirth
Ali
A
Djahangiri
Bernhard
B
Jost
Christian
C
Gerber
D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D061165:Glenoid Cavity / Q000000981:diagnostic imaging* / Q000502:physiology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008962:Models, Theoretical; D015588:Observer Variation; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D015203:Reproducibility of Results; D012399:Rotation; D012540:Scapula / Q000000981:diagnostic imaging / Q000502:physiology; D012785:Shoulder Joint / Q000000981:diagnostic imaging* / Q000502:physiology; D014057:Tomography, X-Ray Computed / Q000379:methods