A tool for separating an acetabular shell of a hip prosthesis from the surrounding pelvic bone includes a fixture which attaches to the acetabular shell and has a chisel guide mounted on it. A chisel associated with the chisel guide is curved to conform to the outer periphery of the acetabular shell, and the chisel guide causes the chisel to circumscribe the acetabular shell as the chisel is inserted between the acetabular shell and the pelvis.