SURGICAL TREATMENT OF LUMBAR SPINAL STENOSIS WITH INTERSPINOUS IMPLANTABLE DEVICES
Leningrad Regional Clinical Hospital,
North-Western State Medical University named after I.I. Mechnikov,
Russian Scientific Neurosurgery Institute named after Professor A.L. Polenov, the branch of North-western Federal medical Research Center,
Saint Petersburg, Russia
Degenerative dystrophic diseases of the spine take a leading place in etiology of vertebrogenic myeloradiculopathy. The proportion of degenerative spinal injuries achieves 52 % among all neurologic diseases, with 81 % of disorders in the lumbosacral spine [1]. Up to the present time, microdiscectomy was the standard for surgical treatment of degenerative dystrophic diseases of the lumbar spine causing spinal stenosis. During the recent years many leading clinics implemented the concept of dynamic stabilization as the supplement to microdiscectomy. Various types and methods of dynamic stabilization for spinal segments were developed. They are based on the various biomechanical principles and are designed for anterior and posterior spinal fixation. One of the new types of devices for spinal stabilization is the interspinous implants Coflex and StenoFix. Spinal implants, which are placed into interspinous space for dynamic stabilization of the spine, present the compressed U-shaped titan devices, which are implanted into the interspinous space. This type of the devices was developed by French surgeon-orthopedist Samani J in 1994 (9). Coflex and StenoFix provide fast recovery of spinal segments in concordance with natural biomechanical state and gives the possibilities for salvation of natural anatomic architectonics with preservation of rotation center and with prevention of reconfiguration of the spinal segment. The mechanism of the interspinous devices for treating lumbar spinal stenosis is associated with increasing foraminal height and decreasing load to the articular processes and the posterior parts of the intervertebral disk. However, according to some international authors, the interspinous implants showed high rates of complications in treatment of spondylolisthesis when used as replacement of spondylodesis during surgical treatment of lumbar spinal stenosis [11, 13]. Therefore, the question about a method of efficient stabilization of the spinal motional segment after microsurgical discectomy and about the algorithm for use of various low invasive implants is still actual and it requires the appropriate solution.
The objective of the study – on the basis of the results of objective tests and clinical symptoms to select the optimal tactics of surgical treatment of degenerative-dystrophic diseases causing lumbar stenosis.
MATERIALS AND METHODS
The prospective randomized study included the data about all stages of surgical treatment of 114 patients with lumbar spinal stenosis who were operated in the neurosurgery department of Leningrad Regional Clinical Hospital in 2012-2015. There were 67 men (59 %) and 47 women (41 %). There were no statistically significant differences in the demographic data between two groups (p < 0.05). The table 1 shows the distribution of the prepared levels in both groups.
The patients were distributed into two groups in dependence on surgical treatment. The first group (group A) included the patients with microsurgical lumbar spinal decompression with placement of the interspinous dynamic devices (n = 56). The control group (group B) included the patients with microsurgical decompression without implants (n = 58).
The following examination methods were used: clinical neurological and radiologic examination, magnetic resonance imaging.
The criteria for inclusion into the study:
- clinical and radiological signs of lumbar spinal stenosis;
- one or two levels of lumbar spinal stenosis;
- no previous surgical interventions for the lumbar spine;
- patients with 1st class of lumbar spondylolisthesis (the degree 1 – the posterior edge of the vertebra is displaced to ¼ in relation to the inferior vertebra).
The patients with injuries, infections and spondylolisthesis of more than 2nd class were excluded from the study.
Surgical technique
For two groups of dynamic interspinous implants adequate decompression was achieved with partial hemilaminectomy and removal of the hypertrophied yellow ligament. The first group received implantation of the device. After resection of the interspinous ligament the size of the device was chosen with use of the templates. The device was inserted and tightened with clips around the spinous processes. The electronic optical converter was used for controlling the effect of a chosen template (Fig. 1).
Figure 1
The scheme of implantation of the interspinous device Stenofix:
a – placement of a test probe; b – placement of the interspinous implant; c – fixation with use of specific forceps.
a 
b 
c
Clinical criteria of estimation
We estimated the time trends of neurologic status and intensity of pain syndrome. Visual analog scale (VAS) is the most simple, comfortable and widely used scale for estimation of pain severity. VAS presents the line space of 10 cm. The patient makes a note according to his/her pain intensity. The initial point of the interval presents absence of pain – 0. The end of the interval (10) corresponds to unbearable pain. The distance between the left end of the interval and the patient’s note is measured with millimeters.
Also we calculated the intensity of disorders in functional activity of the patients according to Oswestry Disability Index (ODI). ODI is a widely use scale for estimation of degree of disorders of vital activity conditioned by spinal pathology. ODI was developed by Jeremy C.T. Fairbank in 1980, when we worked in Agnes Hunt Orthopaedic Hospital, Oswestry, UK. At the present time, Oswestry questionnaire 2.1a is available. It consists of 10 sections. For each section the maximal point is 5. The first item means 0, the last one – 5.
Radiologic criteria
The radiologic analysis was made with the presurgical images. The results of treatment were analyzed within the time intervals from 6 months to 2 years by means of the radiologic criteria (3):
1. Posterior height of the disk was measured as the perpendicular line from the posterior-inferior edge of the endplate of the superjacent vertebra to the plane of the endplate of the subjacent vertebra.
2. Foraminal height – the maximal distance between the inferior edge of the pedicle of the arch of the superior vertebra and the superior edge of the pedicle of the arch of the inferior vertebra (Fig. 2).
Figure 2
The radiologic criteria: foraminal height is indicated with red color; posterior height of the disk is indicated with blue color.
Statistica 6.1 and Microsoft Office Excel 2010 were used for the statistical analysis. Quantitative variables were described as mean arithmetic (M) and standard error (m). The analysis of qualitative signs was made with Fisher test. P = 0.05 was the level of statistical significance in comparison of qualitative and quantitative variables in the examined groups.
All persons gave their written consent for participation in the study. The study was conducted with approval from the local ethical committee of North-Western State Medical University named after I.I. Mechnikov.
RESULTS
The mean age was slightly higher in the group A: 47.2 ± 6.7 vs. 44.4 ± 6.1. 87 % of the patients of the group A were operated at one level, four patients – at two levels. The segment L4-5 was the most common segment for surgical intervention. By contrast, in the group B @ patients were operated at one level and 5 patients at two levels (table 1).
| Table 1 | ||||
| Distribution of treated levels in the groups | ||||
Besides identification of complaints and anamnesis data, we conducted the clinical examination including proper neurological testing and correlation between the data and the results of the instrumental examination. The leading neurologic manifestations of the operated patients were syndromes of mono- and polyradicular compression, local and reflected reflectory pain syndrome, with neurologic deficiency in the region of innervation of compressed spinal roots. These patients had some sensitivity disorders in combinations with absence or decrease of reflex, weakness in the lower extremities and limited mobility in the lumbar spine. Laterality of the symptoms was observed in all patients with lesions of the lumbar spine (table 2, 3).
| Table 2 | |||
| Dynamics of changes in ODI values | |||
| Table 3 | |||
| Pain intensity according to VAS (points) | |||
Within two years of follow-up both groups showed significant clinical improvement in functional activity index according to ODI and VAS (p < 0.05). There were no statistical differences between two groups in the above-mentioned groups before surgery (p < 0.05).
There were no differences in posterior height of the disk and foraminal height in two examined groups (p < 0.05). During two years of the follow-up we found significant increase in the above-mentioned values in the group of the patients who had received the interspinous implants (table 4, 5).
| Table 4 | |||||||
| The radiologic parameters before and after surgical treatment in the group A | |||||||
| Table 5 | |||||||
| The radiologic parameters before and after surgical treatment in the group B | |||||||
Infectious complications after installation of the interspinous implants were not found. One case of recurrent surgery after a fracture of the interspinous implant was found. Recurrent operations were conducted for two patients in the control group.
The spaces between the implant and the spinous processes were found in 6 patients (11 % in the group of dynamic implants). The spaces were especially noticeable around the pricks of the dynamic device.
DISCUSSION
The new direction in surgical treatment of degenerative stenosis is the interspinous fixators (Coflex, Stenofix). The advantage of such implants is simplicity of installation, load relief for posterior departments of the intervertebral discs and the facet joints [4, 6]. The implants are used for the following spinal diseases: discogenic radiculitis, facet joint syndrome, intervertebral hernia or unstable lumbar spine. Minimal invasiveness and simplicity of implantation are favorable for usage in older patients.
Installation of the fixators is considered not only as a way of removal of instability, but also as a measure for active prevention after hernia excision by means of interlaminar approach. It is known that distraction of the spinous processes is accompanied by tension of the yellow ligament, posterior departments of the fibrous ring and reclination of the articular processes resulting in increasing sizes of the spinal canal and the intervertebral foramina.
There were several studies of the interspinous implants for degenerative dystrophic diseases of the spine. The studies found significant increase in the relationship of height of posterior discs. Most studies were based on short periods of follow-up [4, 6, 7, 10]. But some authors disputed these propositions.
The experimental studies show that the interspinous implants, such as Coflex, provide flexion and distraction of the posterior supporting structures of VMS, remove central and foraminal dynamic stenosis, but significantly increase the volume of lateral inclinations, decrease the square of contact of joint facets and cause a subluxation of facet joints with progression of spondylarthrosis [8, 12].
Celik H. et al. [2] conducted the study and concluded that additional implantation of the interspinous implants is inappropriate in surgical treatment of the lumbar spine.
Usage of dynamic implants for lumbar spine stenosis is inappropriate. Also unfavorable radiologic outcomes are possible: appearance of spaces between the dynamic implant and, as result, a fracture of the spinous process. Clarification and spaces were especially notable around the pricks of the implant [5]. In our study bone erosion was observed in only 6 patients (11 %). The results are based on the short period of the follow-up. Considering these estimations it was difficult to evaluate long term perspectives of the above-mentioned implants.
Xu C. et al. [14] conducted one of the first long term studies in 2015 [14]. The study estimated appropriateness and substantiation of use of the interspinous dynamic implants in surgical treatment of degenerative diseases of the lumbar spine at L5/S1 level. The retrospective study included 33 patients with degenerative stenosis of the lumbar spine at L5/S1 level. The dynamic devices were implanted within the period from November, 2007 to September, 2010. During 4 years of the follow-up all patients demonstrated both the clinical (VAS, ODI) and radiologic values (height of the intervertebral discs). Also absence of changes in the range of motions in the adjacent segment was observed.
CONCLUSION
Usage of the interspinous dynamic devices for lumbar spinal stenosis gives some advantages such as low invasiveness, simple installation, absent injuries to surrounding tissues. Our results encourage further search of the ways of improvement of existing ways of surgical treatment, but it is necessary to continue the work according to more strict selection of patients for each type of implants.