Boileau et al. define and validate the RSA angle — a new measurement of inferior glenoid inclination — to address the question of whether standard glenoid inclination measurements (β/TSA angle) accurately reflect the inclination a reverse baseplate will actually experience. The study compares both angles across plain radiographs, 2D CT, and 3D software in 47 shoulders with rotator cuff tear arthropathy, stratified by Favard erosion type.
When planning RSA, measure the RSA angle (inferior glenoid inclination) rather than the β/TSA angle — the β angle will underestimate superior tilt by ~10° on average and up to 12° in Favard E1 glenoids, leading you to undercorrect.
If the RSA angle on preoperative CT is 20°, you need 20° of correction to achieve neutral inclination; inferior reaming alone risks medialization, so consider a superior augmented baseplate or angled BIO-RSA.
Boileau et al. define and validate the RSA angle — a new measurement of inferior glenoid inclination — to address the question of whether standard glenoid inclination measurements (β/TSA angle) accurately reflect the inclination a reverse baseplate will actually experience. The study compares both angles across plain radiographs, 2D CT, and 3D software in 47 shoulders with rotator cuff tear arthropathy, stratified by Favard erosion type.
When planning RSA, measure the RSA angle (inferior glenoid inclination) rather than the β/TSA angle — the β angle will underestimate superior tilt by ~10° on average and up to 12° in Favard E1 glenoids, leading you to undercorrect.
If the RSA angle on preoperative CT is 20°, you need 20° of correction to achieve neutral inclination; inferior reaming alone risks medialization, so consider a superior augmented baseplate or angled BIO-RSA.