An implantable prosthesis intended, primarily for the repair of muscle wall defects such as occur in inguinal hernias is fabricated from a surgically compatible mesh material having a prismatic external mesh wall (1). The prismatic shape includes three lobes (2), providing a generally triangular cross-sectional shape. The shape is maintained by internal reinforcing ribs (3), which here extend the length of the prism. The ribs are formed through the connection of three individual mesh strips (4), with each rib comprising two strip parts forming a lamination extending the length of the prism. With this construction closure of elongate legions is readily achieved and a wide range of elongate shapes and dimensions of hernias can be treated.
