A surgical distractor comprising: a base plate (2, 102, 202, 302, 402); a distraction plate (4, 104, 204, 304, 404); and one or more intermediate stages (6, 106a, 106b, 206a, 206b, 306a, 306b); wherein one of the one or more intermediate stages is telescopically coupled to the base plate by a telescopic coupling, wherein the telescopic coupling is generally circular and comprises helical structures formed upon the base plate and the intermediate stage coupled to the base plate, which convert relative rotary movement between the base plate and the intermediate stage coupled to the base plate into relative linear movement between the base plate and the intermediate stage coupled to the base plate along the axis of rotation, wherein the telescopic coupling comprises three helical structures such that the base plate and the intermediate stage coupled to the base plate are coupled together at three points spaced apart around the circumference of the telescopic coupling, wherein one of the one or more intermediate stages is telescopically coupled to the a distraction plate by a telescopic coupling, wherein the telescopic coupling is generally circular and comprises helical structures formed upon the distraction plate and the intermediate stage coupled to the distraction plate, which convert relative rotary movement between the distraction plate and the intermediate stage coupled to the distraction plate into relative linear movement between the distraction plate and the intermediate stage coupled to the distraction plate along the axis of rotation, wherein the telescopic coupling comprises three helical structures such that the distraction plate and the intermediate stage coupled to the distraction plate are coupled together at three points spaced apart around the circumference of the telescopic coupling, whereby the distraction plate is arranged to move towards or away from the base plate. a base plate (2, 102, 202, 302, 402); a distraction plate (4, 104, 204, 304, 404); and one or more intermediate stages (6, 106a, 106b, 206a, 206b, 306a, 306b); wherein one of the one or more intermediate stages is telescopically coupled to the base plate by a telescopic coupling, wherein the telescopic coupling is generally circular and comprises helical structures formed upon the base plate and the intermediate stage coupled to the base plate, which convert relative rotary movement between the base plate and the intermediate stage coupled to the base plate into relative linear movement between the base plate and the intermediate stage coupled to the base plate along the axis of rotation, wherein the telescopic coupling comprises three helical structures such that the base plate and the intermediate stage coupled to the base plate are coupled together at three points spaced apart around the circumference of the telescopic coupling, wherein one of the one or more intermediate stages is telescopically coupled to the a distraction plate by a telescopic coupling, wherein the telescopic coupling is generally circular and comprises helical structures formed upon the distraction plate and the intermediate stage coupled to the distraction plate, which convert relative rotary movement between the distraction plate and the intermediate stage coupled to the distraction plate into relative linear movement between the distraction plate and the intermediate stage coupled to the distraction plate along the axis of rotation, wherein the telescopic coupling comprises three helical structures such that the distraction plate and the intermediate stage coupled to the distraction plate are coupled together at three points spaced apart around the circumference of the telescopic coupling, whereby the distraction plate is arranged to move towards or away from the base plate.