An anchor unit, an instrument for deploying the anchor unit, and methods of treating or preventing vaginal vault prolapse and/or uterine prolapse in conditions of utero-vaginal prolapse are disclosed. The anchor unit can include an anchor housing and an anchor blade assembly. The anchor housing can include a first peripheral wall and a second peripheral wall which can be arranged in the shape of a knife blade. The anchor blade assembly can include a plurality of blades for securing the anchor unit to body tissue. The anchor blade assembly can be configured to be rotatable with respect to the anchor housing to allow the deployment of the plurality of blades into body tissue in a deployed state of the anchor unit.