EXPERIMENTAL LUMBAR SPONDYLOLISTHESIS IN GROWING RABBITS

Lumbosacral spondylolisthesis was provoked experimentally in growing r abbits by means of a bilateral facet joint resection at the L7-S1 segm ent. The effects of additional immobilization of the L6-L7 segment wit h bone cement and of severing the lumbosacral disc on the development of the olisthesis were tested, A mean ventral slip of 21% was seen aft er 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 1 5%. Morphologic features of the slip were like those seen after a plai n facet joint resection, A different result was seen after facet joint resection was combined with severing of the lumbosacral disc, The mea n slip was only 6%, and sacral rounding was a prominent feature. This experiment shows that an upright posture of the spine is not a prerequ isite for the development of spondylolisthesis. A bilateral facet join t resection in a growing rabbit results in a human like spondylolisthe sis, This model may help further experimental studies concerning the c hanges in the olisthetic disc.