Abstract: Indirect lumbo-sacral fixation makes use of intact powerful ligaments joining the ilium to the sacrum by providing internal ilio-lumbar fixation in which tulip type pedicle screws (30) are screwed into the pedicles (46,48) at one side of the lowest lumbar vertebrae (47, 49) and are rigidly connected to a pelvic plate (31) secured by bone screws (52) to the posterior face of the adjacent ilium (51), the connection comprising a bent rod (32) having a knurled (or splined) spinal portion (33) secured in the pedicle screws by grubscrews (37) and locking screws (38) and having a non-circular male pelvic portion (35) fitting a mating female hole (40) and secured therein by a locking screw (41). Alternatively, the connection can include a universal joint between the pelvic portion of the bent rod and the pelvic plate, with three mutually perpendicular lockable pivotal connections.