In a first aspect the present invention provides a glenoid
prosthesis assembly for use in
shoulder joint arthroplasty to address conditions where deterioration of the
rotator cuff mechanism of the
shoulder joint is severe, the
assembly comprising a first shell component to be affixed to a
scapula by fixing means, and a smaller second component adapted to
nest within the first component and having an articulation surface for articulating with a humeral head, the first component being over-sized relative to the glenoid surface of a
scapula whereby the first component may be first affixed to at least two of the glenoid,
acromion and
coracoid processes of the
scapula in use by the fixing means and the second component may be cemented in place within the first component allowing initial adjustability in the
poise of the second component relative to the first component. Amongst other aspects the invention also provides a modular proximal humeral
prosthesis system for use in
shoulder joint arthroplasty which enables the proximal humeral
prosthesis to be changed between anatomical and reverse of anatomical configurations to address differing degrees of shoulder joint deterioration.