Décompression et stabilisation dynamique sans fusion avec le système Dynesys® dans le traitement des spondylolisthésis dégénératifs lombaires (à propos d’une série prospective de 25 cas)

Diagnostic Importance of Axial Loaded Magnetic Resonance Imaging in Patients with Suspected Lumbar Spinal Canal Stenosis

OBJECTIVE AND BACKGROUND

To study the efficacy of lumbar (AL) magnetic resonance imaging (MRI) in patients with suspected lumbar spinal stenosis (LSS), with and without AL compression. Supine MRI is used in the assessment of patients with LSS. However, MRI findings may poorly correlate with neurologic findings because of the morphologic changes of the lumbar spinal canal between upright standing and supine positions. In patients without significant stenosis in routine lumbar MRI, by applying AL, MRI can show significant LSS.

METHODS

This study included 103 consecutive patients (188 disc levels) who presented with neurogenic claudication with and without low back pain. AL was performed using a nonmagnetic compression device for 5 minutes. T1- and T2-weighted axial and sagittal sequences were obtained during AL applied to the spine. The dural sac cross-sectional area (DSCA) appeared to be narrow at each disc level of L4-5 to L5-S1 in all patients and was measured using T2-weighted images in routine supine and AL images.

RESULTS

The groups included patients with a reduction in the DSCA (>15 mm²) according to patient age and DSCA in routine spine MRI. The mean DSCA of the disc levels without and with AL were 138 mm² and 123 mm², with a mean difference of 15 mm² at L4-5, 134 mm² and 125 mm² and a mean difference of 9 mm² at L5-S1, respectively.

CONCLUSIONS

The use of AL MRI in patients with clinically suspected LSS could reduce the risk of misdiagnosis of stenosis, leading to inappropriate treatment.

Degenerative lumbar spondylolisthesis: cohort of 670 patients, and proposal of a new classification

Degenerative spondylolisthesis is common in adults. No consensus is available about the analysis or surgical treatment of degenerative spondylolisthesis. In 2013, the French Society for Spine Surgery (Societe francaise de chirurgie du rachis) held a round table discussion to develop a classification system and assess the outcomes of the main surgical treatments. A multicentre study was conducted in nine centres located throughout France and Luxembourg. We established a database on a prospective cohort of 260 patients included between July 2011 and July 2012 and a retrospective cohort of 410 patients included in personal databases between 2009 and 2013. For patients in the prospective cohort clinical assessments were performed before and after surgery using the self-administered functional impact questionnaire AQS, SF12, and Oswestry Disability Index (ODI). Type of treatment and complications were recorded. Antero-posterior and lateral full-length radiographs were used to measure lumbar lordosis (LL), segmental lordosis (SL), pelvic incidence (PI), pelvic tilt (PT), sagittal vertical axis (SVA), and percentage of vertebral slippage. Mean follow-up was 10 months. We started a randomised clinical trial comparing posterior fusion of degenerative spondylolisthesis with versus without an inter-body cage. 60 patients were included, 30 underwent 180° fusion and 30 underwent 360° fusion using an inter-body cage implanted via a transforaminal approach. We evaluated the quality of neural decompression achieved by minimally invasive fusion technique. In a subgroup of 24 patients computed tomography (CT) was performed before and after the procedure and then compared. Mean age was 67 years and 73% of degenerative spondylolisthesis were located at L4-L5 level. The many surgical procedures performed in the prospective cohort were posterior fusion (39%), posterior fusion combined with inter-body fusion (36%), dynamic stabilization (15%), anterior lumbar fusion (8%), and postero-lateral fusion without exogenous material (2%). Peri-operative complications of any severity occurred in 17% of patients. The AQS, ODI and SF12 scores were improved significantly at follow-up. We found no differences in clinical improvements across surgical procedure types. Circumferential fusion (360°) was associated with greater relief of nerve root pain and better lordosis recovery after 1 year compared to postero-lateral fusion (180°). Post-operative CT images showed effective decompression of nervous structures after minimally invasive fusion. Longer follow-up of our patients is needed to assess the stability of the results of the various surgical procedures. Based on a radiological analysis, the authors propose a new classification with five types of degenerative spondylolisthesis: type 1, SL>5° and LL>PI-10°; type 2, SL<5° and LL>PI-10°; type 3, LL<PI-10°; type 4, LL<PI-10° and compensated sagittal balance with PT>25°; and type 5, sagittal imbalance with SVA>4 cm.

PROOF LEVEL

IV Observational cohort study. Retrospective review of prospectively collected outcome data.

Dynamic stabilisation in the treatment of degenerative disc disease with modic changes

Objective. Posterior dynamic stabilization is an effective alternative to fusion in the treatment of chronic instability and degenerative disc disease (DDD) of the lumbar spine. This study was undertaken to investigate the efficacy of dynamic stabilization in chronic degenerative disc disease with Modic types 1 and 2. Modic types 1 and 2 degeneration can be painful. Classic approach in such cases is spine fusion. We operated 88 DDD patients with Modic types 1 and 2 via posterior dynamic stabilization. Good results were obtained after 2 years of followup. Methods. A total of 88 DDD patients with Modic types 1 and 2 were selected for this study. The patients were included in the study between 2004 and 2010. All of them were examined with lumbar anteroposterior (AP) and lateral X-rays. Lordosis of the lumbar spine, segmental lordosis, and ratio of the height of the intervertebral disc spaces (IVSs) were measured preoperatively and at 3, 12, and 24 months after surgery. Magnetic resonance imaging (MRI) analysis was carried out, and according to the data obtained, the grade of disc degeneration was classified. The quality of life and pain scores were evaluated by visual analog scale (VAS) score and Oswestry Disability Index (ODI) preoperatively and at 3, 12, and 24 months after surgery. Appropriate statistical method was chosen. Results. The mean 3- and 12-month postoperative IVS ratio was significantly greater than that of the preoperative group (P < 0.001). However, the mean 1 and 2 postoperative IVS ratio was not significantly different (P > 0.05). Furthermore, the mean preoperative and 1 and 2 postoperative angles of lumbar lordosis and segmental lordosis were not significantly different (P > 0.05). The mean VAS score and ODI, 3, 12, and 24 months after surgery, decreased significantly, when compared with the preoperative scores in the groups (P = 0.000). Conclusion. Dynamic stabilization in chronic degenerative disc disease with Modic types 1 and 2 was effective.

Dynamic stabilization for challenging lumbar degenerative diseases of the spine: a review of the literature

Fusion and rigid instrumentation have been currently the mainstay for the surgical treatment of degenerative diseases of the spine over the last 4 decades. In all over the world the common experience was formed about fusion surgery. Satisfactory results of lumbar spinal fusion appeared completely incompatible and unfavorable within years. Rigid spinal implants along with fusion cause increased stresses of the adjacent segments and have some important disadvantages such as donor site morbidity including pain, wound problems, infections because of longer operating time, pseudarthrosis, and fatigue failure of implants. Alternative spinal implants were developed with time on unsatisfactory outcomes of rigid internal fixation along with fusion. Motion preservation devices which include both anterior and posterior dynamic stabilization are designed and used especially in the last two decades. This paper evaluates the dynamic stabilization of the lumbar spine and talks about chronologically some novel dynamic stabilization devices and thier efficacies.

Effect of graded facetectomy on biomechanics of Dynesys dynamic stabilization system

STUDY DESIGN

Finite element (FE) method was used to compare the biomechanics of L3-S1 lumbar spine with graded facetectomy before and after placement of Dynesys.

OBJECTIVE

To evaluate the biomechanics of Dynesys as a function of graded bilateral facetectomies.

SUMMARY OF BACKGROUND DATA

Spinal fusion or posterior dynamic stabilization systems are used to restore stability after facetectomies.

METHODS

The intact FE spine was modified to simulate decompression at L4-L5 with 50% and 75% and total facetectomy with/without dynamic stabilization with Dynesys. Biomechanics of the implanted level was investigated under different physiological loadings.

RESULTS

Total facetectomy increased the motion in extension (8.7° vs. 2.7° for intact) and axial rotation (8.4° vs. 2.4° for intact). However the decrease in motion in the Dynesys model ranged from 65% in axial rotation to 80% in flexion for all facetectomies, except in the total facetectomy axial rotation case (motion higher than intact). The center of rotation of dynamic stabilized segment moved inferior/posterior in partial facetectomy and superior/posterior in total facetectomy with respect to the intact and destabilized cases. The Dynesys screws observed peak stresses up to 28% higher than those of a rigid fixation system in certain loadings, such as lateral bending and extension. The critical loosening torque applied to the screws in total facetectomy case was 6 times the partial facetectomy case in axial rotation.

CONCLUSION

Partial facetectomy had a minimal effect on range of motion on the Dynesys-implanted segment. However, in the case of total facetectomy the motion increased by almost 40% in flexion and by 200% in axial rotation. The higher stresses applied to the screws in Dynesys in specific loadings may lead to higher risk of screw failure in Dynesys than in a generic rigid fixation construct.

Minimum two-year follow-up of cases with recurrent disc herniation treated with microdiscectomy and posterior dynamic transpedicular stabilisation

The objective of this article is to evaluate two-year clinical and radiological follow-up results for patients who were treated with microdiscectomy and posterior dynamic transpedicular stabilisation (PDTS) due to recurrent disc herniation. This article is a prospective clinical study. We conducted microdiscectomy and PDTS (using a cosmic dynamic screw-rod system) in 40 cases (23 males, 17 females) with a diagnosis of recurrent disc herniation. Mean age of included patients was 48.92 +/- 12.18 years (range: 21-73 years). Patients were clinically and radiologically evaluated for follow-up for at least two years. Patients' postoperative clinical results and radiological outcomes were evaluated during the 3rd, 12th, and 24th months after surgery. Forty patients who underwent microdiscectomy and PDTS were followed for a mean of 41 months (range: 24-63 months). Both the Oswestry and VAS scores showed significant improvements two years postoperatively in comparison to preoperative scores (p<0.01). There were no significant differences between any of the three measured radiological parameters (alpha, LL, IVS) after two years of follow-up (p > 0.05). New recurrent disc herniations were not observed during follow-up in any of the patients. We observed complications in two patients. Performing microdiscectomy and PDTS after recurrent disc herniation can decrease the risk of postoperative segmental instability. This approach reduces the frequency of failed back syndrome with low back pain and sciatica.