Experimental lumbar instability and artificial ligament

Clinical significance of achieving a flexion limitation with a tension band system in grade 1 degenerative spondylolisthesis: a minimum 5-year follow-up

STUDY DESIGN

Retrospective clinical study.

OBJECTIVE

To evaluate the effect of the limitation of flexion rotation clinically and radiologically after interspinous soft stabilization using a tension band system in grade 1 degenerative spondylolisthesis.

SUMMARY OF BACKGROUND DATA

Although several studies have been published on the clinical effects of limiting rotatory motion using tension band systems, which mainly targets the limitation of flexion rather than that of extension, they were confined to the category of pedicle screw-based systems, revealing inconsistent long-term outcomes.

METHODS

Sixty-one patients with a mean age of 60.6 years (range, 28-76 yr) who underwent interspinous soft stabilization after decompression for grade 1 degenerative spondylolisthesis with stenosis between 2002 and 2004 were analyzed. At follow-up, the patients were divided into 2 groups on the basis of their achievement or failure to achieve flexion limitation. The clinical and radiological findings were analyzed. A multiple linear regression analysis was performed to determine the prognostic factors for surgical outcomes.

RESULTS

At a mean follow-up duration of 72.5 months (range, 61-82 mo), 51 patients were classified into the flexion-limited group and 10 into the flexion-unlimited group. Statistically significant improvements were noted only in the flexion-limited group in all clinical scores. In the flexion-unlimited group, there were significant deteriorations in flexion angle (P = 0.009), axial thickness of the ligamentum flavum (P = 0.013), and the foraminal cross-sectional area (P = 0.011), resulting in significant intergroup differences. The preoperative extension angle was identified as the most influential variable for the flexion limitation and the clinical outcomes.

CONCLUSION

The effects of the limitation of flexion rotation achieved through interspinous soft stabilization using a tension band system after decompression were related to the prevention of late recurrent stenosis and resultant radicular pain caused by flexion instability. The extension potential at the index level was recognized as a major prognostic factor that can predict the flexion limitation and the clinical results.

LEVEL OF EVIDENCE

4.

Factors affecting clinical outcomes in treating patients with grade 1 degenerative spondylolisthesis using interspinous soft stabilization with a tension band system: a minimum 5-year follow-up

STUDY DESIGN

Retrospective clinical study.

OBJECTIVE

To explore the factors influencing the clinical outcomes and motion-preserving stabilization after interspinous soft stabilization (ISS) with a tension band system for grade 1 degenerative spondylolisthesis (DS).

SUMMARY OF BACKGROUND DATA

Despite increasing recognition of the benefits of dynamic stabilization systems for treating lumbar degenerative disorders, the factors affecting the clinical and radiological outcomes of these systems have rarely been identified.

METHODS

Sixty-five patients (mean age, 60.3 years) who underwent ISS with a tension band system between 2002 and 2004 were analyzed. The mean follow-up period was 72.5 months. The patients were divided according to the postsurgical clinical improvements into the optimal (n = 44) and suboptimal groups (n = 21), and the radiological intergroup differences were analyzed. Multiple linear regression analysis was performed to determine the impact of the radiological factors on the clinical outcomes.

RESULTS

Significant intergroup differences were observed on the follow-up clinical examination. Radiologically, total lumbar lordosis (TLL) and segmental lumbar lordosis (SLL) were significantly improved only in the optimal group, resulting in significant intergroup differences in TLL (P = 0.023), SLL (P = 0.001), and the L1 tilt (P = 0.002). All these measures were closely associated with postoperative segmental lumbar lordosis, which also was the most influential radiological variable for the clinical parameters.

CONCLUSION

In the patients with grade 1 DS, the back pain relief and functional improvement following ISS were affected by the improvements in the sagittal spinal alignment through the achievement of segmental lumbar lordosis. ISS can be an alternative treatment to fusion surgery for grade 1 DS in patients who do not require fixation or reduction.

Soft stabilization with interspinous artificial ligament for mildly unstable lumbar spinal stenosis: a multicenter comparison

INTRODUCTION

In an attempt to fill a gap between simple decompression alone and fusion in the spectrum of surgical treatment for degenerative lumbar spinal stenosis (DLSS), the authors sought to demonstrate the efficacy and reproducibility of soft stabilization with interspinous artificial ligament after microsurgical fenestration to prevent post-decompression segmental instability for mildly unstable DLSS.

MATERIALS AND METHODS

Clinical outcomes from 556 patients treated with soft stabilization with artificial ligament following microdecompression for mildly unstable DLSS from March 1998 to June 2006 were retrospectively obtained from three institutions in three countries. Outcomes were measured at a mean of 48.9 months after surgery using MacNab criteria. Peri- and postoperative complications and revision surgery cases were also analyzed.

RESULTS

Follow-up was achieved in 391 (70.3%) of the 556 patients. Clinical outcomes were excellent in 43.7%, good in 36.7%, fair in 12.2%, and poor in 7.4% of the patients. The overall clinical success rate was 80.4%. No major complications except postoperative hematoma and wound infection (6/391 cases, 1.5%) were observed, and few revision surgeries (2.3%) were done during follow-up.

CONCLUSION

We found favorable and reproducible results with soft stabilization with artificial ligament after microdecompression for mildly unstable DLSS from three institutions in three countries. Soft stabilization with artificial ligament may be concluded to represent an effective prevention of increased post-decompression instability with reliable reproducibility for mildly unstable DLSS in carefully selected patients.

Biomechanical evaluation of an interspinous stabilizing device, Locker

STUDY DESIGN

A biomechanical study.

OBJECTIVE

To evaluate the biomechanical properties of a novel dynamic interspinous device named Locke

SUMMARY OF BACKGROUND DATA

There has been no biomechanical study on this device.

METHODS

Five human cadaveric lumbar spine specimens (L2-S1) were tested in the following sequence: (1) intact state; (2) after removal of the interspinous ligaments of L3-L4; (3) after application of the Locker at the interspinous space; (4) after destabilization of the L3-L4 motion segments; and (5) after reapplication of the Locker to the destabilized segments. Range of motion (ROM) and intradiscal pressure were measured by a video-based motion capture system and needle transducers.

RESULTS

Applied to the intact spine, the Locker significantly reduced the ROM of the segment in extension and flexion without significant effect on lateral bending and/or axial rotation. When applied to the destabilized segment, it significantly reduced the ROM in all directions of movement except in axial rotation, where it failed to restore the ROM of the segment. The ROM of adjacent segments was not significantly affected by the application of the Locker. Pressures at the posterior anulus and central nucleus were decreased by application of the Locker.

CONCLUSION

The Locker showed a significant stabilizing effect on the spinal motion segment both in the intact and destabilized spine without any significant effect on adjacent segments. It also decreased the pressures of the posterior anulus and central nucleus significantly. However, in the destabilized spine, it showed no stabilizing effect in axial rotation. This biomechanical property should be considered in clinical application.