The role of the inter-/supraspinous ligament complex in stand-alone interspinous process devices: a biomechanical and anatomic study

Comparison of two FDA-approved interspinous spacers for treatment of lumbar spinal stenosis: Superion versus X-STOP-a meta-analysis from five randomized controlled trial studies

BACKGROUND

Decompressive laminectomy (DI) is a standard operation for lumbar spinal stenosis (LSS) patient with severe claudication symptoms for many years. However, patients whose symptom severity does not meet undergoing invasive surgery make therapeutic options into dilemma. Interspinous spacers (ISP) bridge the gap between surgical interventions and CC in management of LSS. In our study, we aim to systematically assess the two FDA-approved interspinous spacers for treatment of lumbar spinal stenosis: Superion versus X-STOP.

METHODS

Electronic databases, including PubMed, Embase, MEDLINE, Cochrane Library were searched to retrieve clinical trials concerning the comparison between Superion and X-STOP in treatment for lumbar spinal stenosis before April 2017. The following outcome measures were extracted: (1) Zurich Claudication Questionnaire (ZCQ) patient satisfaction score, (2) axial pain severity, (3) extremity pain severity, (4) back-specific functional impairment, (5) reoperation, and (6) complication. The data analysis was conducted with Review Manager 5.3.

RESULTS

Five randomized controlled trials (RCTs) with 1118 patients were included in this meta-analysis. The pooled analysis indicated that the Superion group is superior to X-STOP in axial pain severity (SMD: 0.03; 95% CI 0.15, 0.45; p < 0.0001, I² = 41%, p = 0.16), ZCQ patient satisfaction score (SMD: 0.23; 95% CI 0.08, 0.38; p = 0.002, I² = 0%, p = 0.61). However, Superion group showed similarity outcome in extremity pain severity (SMD: 0.18; 95% CI - 0.06, 0.43; p = 0.14, I² = 62%, p = 0.05), back-specific functional impairment (SMD: 0.04; 95% CI - 0.10, 0.19; p = 0.56, I² = 0%, p = 0.77), reoperation rate (RR: 1.10; 95% CI 0.82, 1.48; p = 0.51, I² = 19%, p = 0.30), and complication (RR: 0.98; 95% CI 0.63, 1.53; p = 0.92, I² = 0%, p = 0.83).

CONCLUSION

Both the Superion and X-STOP interspinous spacers can relieve symptoms of LSS. In addition, the Superion spacer may represent a promising spacer for patient with LSS. As we know, the effectiveness and safety of ISP is still considered investigational and unfavor clinical results in the medical literature may continue to limit the appeal of IPS to many surgeons in the future. However, because of the advantage of IPS technique, it will win a wide place in the future degenerative lumbar microsurgery.

Interspinous posterior devices: What is the real surgical indication?

Interspinous posterior device (IPD) is a term used to identify a relatively recent group of implants used to treat lumbar spinal degenerative disease. This kind of device is classified as part of the group of the dynamic stabilization systems of the spine. The concept of dynamic stabilization has been replaced by that of dynamic neutralization of hypermobility, with the intention of clarifying that the primary aim of this kind of system is not the preservation of the movement, but the dynamic neutralization of the segmental hypermobility which is at the root of the pathological condition. The indications for the implantation of an IPD are spinal stenosis and neurogenic claudication, assuming that its function is the enlargement of the neural foramen and the decompression of the roots forming the cauda equina in the central part of the vertebral canal. In the last 10 years, use of these implants has been very common but to date, no long-term clinical follow-up regarding clinical and radiological aspects are available. The high rate of reoperation, recurrence of symptoms and progression of degenerative changes is evident in the literature. If these devices are effectively a miracle cure for lumbar spinal stenosis, why do the utilization and implantation of IPD remain extremely controversial and should they be investigated further? Excluding the problems related to the high cost of the device, the main problem remains the pathological substrate on which the device is explicit in its action: the degenerative pathology of the spine.

Biomechanical and anatomical considerations in lumbar spinous process fixation--an in vitro human cadaveric model

BACKGROUND CONTEXT

Although multiple mechanisms of device attachment to the spinous processes exist, there is a paucity of data regarding lumbar spinous process morphology and peak failure loads.

PURPOSE

Using an in vitro human cadaveric spine model, the primary objective of the present study was to compare the peak load and mechanisms of lumbar spinous process failure with variation in spinous process hole location and pullout direction. A secondary objective was to provide an in-depth characterization of spinous process morphology.

STUDY DESIGN

Biomechanical and anatomical considerations in lumbar spinous process fixation using an in vitro human cadaveric model.

METHODS

A total of 12 intact lumbar spines were used in the current investigation. The vertebral segments (L1-L5) were randomly assigned to one of five treatment groups with variation in spinous process hole placement and pullout direction: (1) central hole placement with superior pullout (n=10), (2) central hole placement with inferior pullout (n=10), (3) inferior hole placement with inferior pullout (n=10), (4) superior hole placement with superior pullout (n=10), and (5) intact spinous process with superior pullout (n=14). A 4-mm diameter pin was placed through the hole followed by pullout testing using a material testing system. As well, the bone mineral density (BMD) (g/cm(3)) was measured for each segment. Data were quantified in terms of anatomical dimensions (mm), peak failure loads (newtons [N]), and fracture mechanisms, with linear regression analysis to identify relationships between anatomical and biomechanical data.

RESULTS

Based on anatomical comparisons, there were significant differences between the anteroposterior and cephalocaudal dimensions of the L5 spinous process versus L1-L4 (p<.05). Statistical analysis of peak load at failure of the four reconstruction treatments and intact condition demonstrated no significant differences between treatments (range, 350-500 N) (p>.05). However, a significant linear correlation was observed between peak failure load and anteroposterior and cephalocaudal dimensions (p<.05). Correlation between BMD and peak spinous processes failure load was approaching statistical significance (p=.08). 30 of 54 specimens failed via direct pullout (plow through), whereas 8 of 54 specimens demonstrated spinous process fracture. The remaining cases failed via plow through followed by fracture of the spinous process (16 of 54; 29%).

CONCLUSIONS

The present study demonstrated that variation in spinous process hole placement did not significantly influence failure load. However, there was a strong linear correlation between peak failure load and the anteroposterior and cephalocaudal anatomical dimensions. From a clinical standpoint, the findings of the present study indicate that attachment through the spinous process provides a viable alternative to attachment around the spinous processes. In addition, the anatomical dimensions of the lumbar spinous processes have a greater influence on biomechanical fixation than either hole location or BMD.