Abstract
The analysis of failed spinal fusion usually always proves that either biomechanical or biological basic principles have not been observed. We find this in both fractures and tumors, but particularly also in degenerative changes within the region of the lumbar spine.
One must be aware of the fact that lumbar fusion which includes the lumbosacral hinge can have considerable impact on the entire sagittal profile of the spine. In particular in fusion over several in multisegmental fusion within the lumbar region this must be considered as in the case of an unfavorable position of the lumbosacral hinge and in fusion over several segments, no possibility remains for compensation of the malposition within the region of the lumbar spine.
It is obvious that an unfavorable sagittal profile with displacement of the gravity line anteriorly (lumbar kyphosis) results in an unfavorable distribution of the forces at the lumbosacral hinge so that a fusion is always jeopardized by the occurrence of higher bending moments and shearing forces.
Under this aspect, the restoration of an optimal sagittal profile with proper position of the sacrum above the hip joint should be given special attention. We know that the pseudarthrosis rate is significantly lower in correct position of the sagittal profile as in cases of potentially existing flattening of the lumbar spine in terms of a lumbar kyphosis.
There is a close link between the biomechanics and the biology of a fusion.
Particularly in older patients, these two parameters must be given considerable attention if fusion of the lumbar spine is intended, particularly if the lumbosacral hinge is included.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
