Abstract
Reverse TSA initially followed Grammont's dictum that the center of rotation (COR) must be in the bone (“medial” COR). Others have argued for a more lateral COR, which can be a challenge if glenoid bone stock has been medially eroded. When bone loss must be made up, and/or the COR lateralised, the options include use of bone graft or use of metal.
Metal constructs produce a cantilever-loading situation, with substantial bending moments applied to the bone-implant junction. Use of bone graft allows remodeling with living bone, so that ultimately the forces are applied to the bone-implant junction in a more compressive pattern.
The author's preference is to have at least 30% of the circumference of the baseplate contact living bone while the rest may be made up with bone graft which can remodel. It is important to have a deep keel penetrate the cortex medially.
