Reduction and stabilisation of severe spondylolisthesis. A report of three cases.

A modification of a previously reported one-stage technique for reduction and stabilisation of severe spondylolisthesis using a posterior route is described. Reduction is obtained by inserting Harrington rods to lift L5 vertically out of the pelvis and two double-threaded screws to pull it backwards. After reduction the rods are taken away and stabilisation achieved by means of screws and a sacral bar. With this modified technique lumbar vertebrae above L5 are never immobilised, compared with the previous method where the retention of the Harrington rods resulted in more lumbar vertebrae being immobilised than was necessary for fusion. Bone is resected from the sacrum and the fifth lumbar vertebra to avoid too much tension on the nerve roots. Bone grafts are not needed and lumbosacral fusion is achieved within six months due to close contact between the raw bone of the vertebral bodies. Three patients have been treated with this modified technique; there was no reslip, neither during the period when the metallic fixation was in situ nor after its removal.