Experimental lumbar spondylolisthesis in growing rabbits.

Lumbosacral spondylolisthesis was provoked experimentally in growing rabbits by means of a bilateral facet joint resection at the L7-S1 segment. The effects of additional immobilization of the L6-L7 segment with bone cement and of severing the lumbosacral disc on the development of the olisthesis were tested. A mean ventral slip of 21% was seen after the facet joint resection. The slip resembled the spondylolisthesis seen in humans in wedging of the olisthetic vertebra, sacral rounding, and increased sagittal rotation. Combining the facet joint resection with immobilization of the L6-L7 segment resulted in a mean slip of 15%. Morphologic features of the slip were like those seen after a plain facet joint resection. A different result was seen after facet joint resection was combined with severing of the lumbosacral disc. The mean slip was only 6%, and sacral rounding was a prominent feature. This experiment shows that an upright posture of the spine is not a prerequisite for the development of spondylolisthesis. A bilateral facet joint resection in a growing rabbit results in a human like spondylolisthesis. This model may help further experimental studies concerning the changes in the olisthetic disc.