The modular mould (1) for forming an orthopaedic spacer made of medical cement defines a moulding cavity delimited by a moulding surface (3, 3′；, 3″；) and configured for impressing a predetermined shape on said medical cement and realising said orthopaedic spacer. The mould (1, 1′；) comprises a first sector (7a, 7a′；, 7a″；), defining a first portion of said surface, and a second sector (7b, 7b′；) defining a second portion of the surface, the first and the second portion of the surface being variable, so as to obtain spacers having variable dimensions.
