The authors studied the effects of a ldquo;lumbar trapezoid platerdquo; (spinal plate and pedicle screwing), performed for lumbar spondylolisthesis, observing the effect on the remaining adjacent discs with regard to preoperative and postoperative instability. The authors examined changes in preoperative and postoperative lumbar ROM (range of motion), displacement of motor unit levels, and occurrence of instability in the remaining discs, such as horizontal and rotational displacement, in 26 patients who were followed up for a mean of 29 postoperative months; 13 patients had spondylolytic spondylolisthesis and 13 patients degenerative spondylolisthesis. The authors studied the effects of the fused vertebral angle and reduction of spondylolisthesis on the remaining upper and lower adjacent discs and the preoperative and postoperative fused disc heights. Intervertebral fusion must affect the remaining adjacent discs, but compensatory function of the remaining motor unit level was more influenced by the fused intervertebral angle than by repositioning of the spondylolisthesis. Fusion at a physiologically lordotic position is quite necessary. For this purpose, it is considered important to prevent grafted bones of the posterior lumbar interbody fusion (PLIF) from collapse and to maintain the achieved alignment of the lumbar spine.
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