Interspinous ligamentoplasty.

Lumbar spinal stenosis is a common cause of lowback pain and neurogenic claudication in the adult population. Moreover, degenerative spondylolisthesis ac c ounts for a substantial proportion of lumbar spinal stenosis in this age group. Spinal fusion has become the established operative treatment for unstable degenerative spondylolisthesis.2 However, there are several disadvantages and issues related to posterior instrumented fusion including adjacent-segment degeneration, pseudarthrosis, and other potential complications.7,8 In light of these issues, surgeons have developed an increasing interest in examining alternative approaches to lumbar fusion, which is the basis of the article on interspinous ligamentoplasty by Hong et al.3 in this issue of the Journal of Neurosurgery: Spine. Adjacent-segment disease after lumbar fusion has been well documented in the literature and the awareness of this complication among our community is high. Its incidence ranges in some studies from 25 to 40% with the radiographic incidence approaching 100% and the symptomatic incidence nearly 25%.5 Of particular relevance to the article by Hong et al., Ghiselli et al.1 reported only 3% symptomatic caudal adjacent-segment disease for singlelevel fusion at L4–5 after a mean follow-up of 7.3 years. Hong et al. had an adjacent-segment disease incidence of 4% (1 case out of 23), which is comparable to the rate following single-level fusion at the same level. The above-mentioned issues have provided the impetus for spine surgeons to examine new devices, including dynamic implants. A number of semirigid implant designs have been developed to improve segmental stability, unload posterior elements, and restrict painful motion while otherwise enabling movement. The aim is to attempt to reestablish the “neutral zone” of spinal motion where the range of displacement occurs with force-free motion, as elucidated by White and Panjabi.9 So far, the most studied interspinous device, the X-STOP has only provided us with shortand medium-term results.10–12 The concept of interspinous ligamentoplasty (ILP) was first introduced by Senegas.6 A modified technique was first reported by authors from the same institution as Hong and colleagues (Wooridul Spine Hospital) in 2005.4 Conceptually, ILP restricts flexion of the lumbar spine with augmentation of the interspinous and supraspinatus ligaments. Intuitively, this should limit translation in cases of degenerative spondylolisthesis. The article by Hong et al.3 in this issue is essentially a case series, in which the authors performed their modified ILP in 32 patients (following up 23 patients or 72%) who had Grade 1 spondylolisthesis at L4–5 and were symptomatic for spinal stenosis and in whom conservative management for at least 6 months had failed. Only patients who exhibited sagittal listhesis with central canal stenosis and lateral recess stenosis were included in the study. All other forms of spinal stenosis that were associated with scoliosis, lateral translation, severe disc collapse, or foraminal stenosis were excluded. A control group of 18 patients who underwent bilateral laminotomies was also included, although this group was not prospectively defined and the extent of matching is not clear. The follow-up assessments were made with outcome scores based on the Oswestry Disability Index (ODI) and visual analog scale (VAS) scores, as well as radiological measurements. The mean duration of follow-up was just over 5 years, which qualifies as medium-term results. The clinical outcome showed improvement in the ODI as well as the VAS. Radiological analysis showed consistent improvement in lordosis but there was increased slippage as well as disc collapse, although the latter 2 radiological outcomes did not appear to affect the clinical outcome. What appears to be most significant is that the canal area was increased postoperatively at the referenced level of L4–5. This is obviously a result of the decompression that was performed. It is therefore not proven that ILP is superior to a formal decompression laminectomy, and it is not known if the positive clinical outcome was contributed by a combination of ILP and the decompression, or if decompression alone would have been adequate. It is thus wise not to over-interpret the clinical outcomes of this paper. With regard to complications related to ILP, the auJ Neurosurg Spine 13:24–26, 2010 See the corresponding article in this issue, pp 27–35.