A bone cutting guide system (110) includes a bone cutting guide assembly (111) and a positioning guide (114). The bone cutting guide assembly (111) includes a base pin (112) and a guide mounting arrangement comprising a placement pin guide (113). The pin (112) has an elongate cylindrical shaft (115) having a penetrating end (117). The positioning guide (114) includes a moulding (116) and a hollow cylindrical guide post (118) fixed to the moulding (116). The moulding (116) is constructed from anatomical data obtained by means of a radiographic scan of the head (55) of the femur (14) prior to surgery. The placement pin guide (113) has a handle (121) and a hollow cylindrical guide sleeve (119) dimensioned to slidingly receive the guide pin (112) therein. In use, the moulding (116) is fitted to the head (55) of the femur. The guiding formation (119) of the pin placement guide (113) is received in the post (118) for guiding the insertion of the pin (112) into the head (55) of the femur (14).
