The surgical reduction of spondylolisthesis.

The Schnöllner operation for reduction of spondylolisthesis was performed through a transversal incision. After removal of the disc, two pedunculus screws with two different threads are inserted. Over these screws the reduction is performed against a slotted sacral plate. The operations were performed at the following levels: 48 at L5-S1, seven at L4-L5, and two at both levels. 70.8% of the patients had preoperative lumboischialgia, 23.3% lumbalgia. Postoperatively, 92.1% were without pain. Twenty-seven patients had preoperative sensory disturbances, while only five had such disorders five years after operation. New sensory disturbances occurred after operation in 11 patients, seven of these persisted. Before operation, 27 patients had pareses of the foot and toe extensors; after operation, ten of them. Paresis occurred in 12 cases, of which three persisted. In 13 cases the reposition was complete, in 17 cases the displacement after operation ranged from 11% to 30%. The lumbosacral angle was markedly diminished.