[Effect of lumbar discectomy and disc replacement on compressive load in proximal adjacent segment]

To examine the biomechanical effect of lumbar discectomy and disc replacement on compressive load in proximal adjacent segment, to understand the characteristics of the prosthesis and effects in spine after artificial disc replacement (ADR), and to evaluate long-term clinical effect in adjacent segments.

Complete human cadaveric ligamentous lumbar spine specimens were used to make 3 models: an intact sample, a discectomy sample, and a sample of ADR after the discectomy. The compressive load in proximal segment above the injury segment was measured separately in various loading cases on the 3 models.

The changes of intervertebral loads in the adjacent segments made the compressive load increase in the proximal segment after the discectomy. The compressive load in the proximal segment was lower in the ADR group than that in the injury group. There was no significant difference between the ADR group and intact group.

Discectomy increases the compressive load in the proximal segment, while ADR reduces it, showing the same compressive load level with the intact model in the proximal segment. Changes of compressive loading in adjacent level segments after discectomy and ADR, may be the cause of abnormal stress distribution and movements of adjacent segments, and be of benefit for the disc replacement.