Comment on topographic relations of neural and ligamentous structures of the lumbosacral junction: in vitro investigation. Spondylolisthesis--no reduction, partial reduction or total reduction?

Abstract

efit has been shown to be gained by reduction of a spondylolisthesis as opposed to in-situ fusion [1], reduction, even partial, increases the likelihood of a successful fusion, and the more complete the reduction, the easier it is to restrict the fusion level to the lumbosacral level. However, the fact that modern instrumentation and advances in surgical technique now make full reduction possible has encouraged some surgeons to aim at complete reduction and hence at returning the anatomy to “normal”. They have accepted that irreversible neurological injury to the fifth lumbar root occasionally occurs. Within the limits of an in vitro study of nonlisthetic spines in which an artificial spondylolisthesis is created, the paper goes some way to explain why such neurological injury occurs. The authors present a good case that the anatomically important factor is the variable anatomy of the iliolumbar ligament. In nearly half of their specimens, a portion of this ligament passes from the ventral surface of the fifth vertebra to the front of the sacrum, dorsally to the path of the fifth root. The latter is commonly adherent to the sides of the vertebra, and it was clear that, in patients with this anatomy, reduction must produce traction of the root, which is unpredictable in any particular patient as the anatomy cannot be visualized. The authors show that reposition of more than 22mm in a patient with this anatomy will produce significant root traction (not compression) and hence is likely to be associated with root injury. The root injury is delayed, so formal testing at the end of an operation is of no value. These studies would support the view that, if this involves a translation distance of more than 22 mm, which it almost inevitably will, total reduction of a spondylolisthesis in one session is not justified. If complete reduction is desired, then slow reduction over a period of several days is a much safer procedure [2, 3]. In major olisothesis, resection of the fifth vertebra would be expected to be a neurologically safer procedure, although reported results do not bear this out: in one series, 75% of patients had a post-operative neurological defect, half of which were new [4]. Whether this can be said to be restoring normal anatomy is debatable. Any surgeon dealing with these patients must recognize that partial reduction and correction of kyphosis has the advantage of increasing the likelihood of fusion and may allow such fusion to be restricted to one level [5]. The clinical benefits of this approach have not been established, and inevitably both inter-body and posterior stabilization is required. However, this paper explains that total reposition, which has no clear adREVIEWER’S COMMENT Eur Spine J (2001) 10 :133–134 DOI 10.1007/s005860000235