[Spondylolysis/spondylolisthesis--a new thesis of its etiology].

Attention is drawn to the mode of development of spondylolysis/spondylolisthesis and to the fact that the articular processes of the small vertebrae can exercise an action on the pars interarticularis only if the latter are in oblique position. It is pointed out that the requisite obliqueness of the pars interarticularis is only possible in conjunction with lordosis, so that the latter is an essential condition for the pathogenesis of spondylolysis/spondylolisthesis. It is also pointed out that excessive load due to upright position of the subject is the triggering factor for spondylolysis/spondylolisthesis, because it is only from this position that the articular processes of the small vertebrae can exercise an action on the pars interarticularis. In four-footed animals there is no excessive load on the articular processes because they do not walk or sit upright, which means the articular processes cannot act on the pars interarticularis to trigger spondylolysis/spondylolisthesis. Likewise, there are no vibrations of the vertebral column with lordosis as the inevitable result and consequently there is no spondylolysis/spondylolisthesis. Hence, it is only in humans that the preconditions and triggering factors for spondylolysis/spondylolisthesis exist at all.