The instrument 2 comprises implant attachment element 22 connected to actuation rod 20, and handle 4 having grip 6. Actuation rod 20 is moveable relative to handle 4. The attachment element may be a suction cup with an integral release cord 104, connected to the handle (see figure 18). A drive mechanism 24 mounted on handle 4 drives relative movement between actuation rod 20 and handle 4. Drive mechanism 24 comprises ratchet handle 56 which, when depressed, engages threaded portion 36 of rod 20, causing longitudinal movement of rod 20 when wheel 24 is rotated. In use, attachment 22 attaches to the prosthesis, wheel 24 disengages from the rod thread 36 so the handle 4 can move over rod 20, pushing impaction plate 16 against the acetabular cup rim (see figure 21). Wheel 24 and rod thread 36 are then engaged and wheel 24 is rotated, tensioning the rod 20, eventually locking via lugs 72. A method of release, also claimed, comprises displacing the suction cup 22 with respect to the handle 4 (by turning wheel 24 the opposite direction) until release cord 104 causes the edge 88 of the suction cup 22 to peel back.
