An annuloplasty prosthesis is provided that includes a skeleton and a sleeve. The skeleton comprises a rigid posterior bar segment, which has first and second bar ends. The sleeve (a) comprises a flexible and substantially non-extensible fabric material, (b) covers the rigid posterior bar segment, (c) includes a first portion that extends at least 20 mm beyond the first bar end and a second portion that extends at least 25 mm beyond the second bar end, and (d) has a plurality of visually-sensible fiducial designators at respective longitudinal locations distributed along at least a portion of the sleeve, which fiducial designators are arranged to indicate a longitudinal center of the rigid posterior bar segment. The prosthesis is rigid along the rigid posterior bar segment, and is flexible or semi-rigid along at least 75% of the first portion of the sleeve and along at least 75% of the second portion of the sleeve.
