The intervertebral disc has an important role in the spinal biomechanics. The influence of lumbar discectomy on the disc space height is still uncleared. This study was performed to evaluate the long term influence of lumbar discectomy on intervertebral disc space height.

The author analysed the disc space height in 25 patients who had performed open discectomy for the disc herniation at least two years age. The height was compared with that of unoperated disc and evaluated the role of discectomy in the change of disc space height.

The decrease of disc space height was 3.3mm in average. The loss of anterior height was 4.1mm and that of posterior height was 2.5mm. This discrepancy was statistically significant(p<0.05). Although the difference of disc height loss in each disc space was not significant. the loss in L4-5 disc space was greater than that of other disc space.

These data suggest that lumbar discectomy accelerate the loss of disc height and influence the process of vertebral degeneration by change of spinal biomechanics in long term period.