gms | German Medical Science

Restoration of the sagittal profile is a key goal in spinal surgery. Contrary to spinal fusion, disc arthroplasty allows individual re-balancing. Aim of this prospective clinical study was determination of factors, that allow preoperative prediction of profile-changes.

Between 06/2000 and 01/2005, 193 Prodisc™-devices were implanted in 168 patients. Most frequent indications were DDD (30,5%), Modic-type-I changes (29,9%) and postoperative disc-degeneration (20,7%). Whole-spine lateral x-rays were obtained, global and lumbar segmental lordosis, sacral slope, pelvic tilt and pelvic incidence were measured pre and postOP.

All preoperative parameters showed physiologic values.

68,8% of all patients had surgery on L5/S1. With subsequent increase of lumbosacral segmental lordosis, it decreased in all other lumbar levels, global lordosis remained unchanged, sacral slope increased. In 18,8% of all patients implantation was at L4/5, the sacral slope decreased significantly, likewise segmental lordosis of the other segments. For rebalancing, the pelvic tilt increased.

Implants in the 2 lowest levels triggered a decrease of the pelvic tilt angle and an increase of global lordosis, accompanied by lowered segmental lordosis in the superior lumbar levels.

Lumbar segments adjacent to an artificial disc show a decreased lordosis. Global lordosis is unchanged in single level and increased in double level implantation. Lumbosacral implantation triggers increased sacral slope, implantation at L4/5 increases the pelvic tilt angle. All parameters remain in the published normal range. Load changes of the facet joints and iliosacral joints can be predicted, preoperative clinical testing should include these structures.