Background The Congruent-Arc Latarjet is modification of the Latarjet open bony stabilisation for shoulder instability. It involves rotation of the coracoid so the curved under-surface lies congruent with the glenoid. The aim of this study was to define the relationship between the concave under surface of the coracoid and the glenoid.
Methods An initial study of 210 cadaveric scapulae was performed followed by a study measuring the same curves using 3D CT reconstruction on 20 scapulae from living patients.
Results Cadveric measurement revealed the glenoid's surface had a median radius of curvature of 30 mm and the coracoid had a median radius of curvature of 25 mm. The CT measurements revealed similar radii of curvature with the glenoid measuring 23.9 mm and the coracoid measuring 25.4 mm (p = 0.2488).
Conclusion The curvature of the glenoid in the cadaveric specimens was slightly larger than the corresponding coracoid curvature. In life this difference may be minimised by articular cartilage, labrum and the attachment of capsule. The CT study revealed similar curves, although in contrast to the cadaveric specimens the coracoid curvature was slightly larger. Overall the curvature of the under surface of the coracoid is similar to the glenoid, which supports this modification of the Latarjet procedure.