MRI analysis of the ISOBAR TTL internal fixation system for the dynamic fixation of intervertebral discs: a comparison with rigid internal fixation

The value of fixed segment mobility in posterior dynamic stabilization: a single-center retrospective study

PURPOSE

This study aims to compare the effects of two generations of the Isobar dynamic fixation system-Isobar TTL (first-generation, less mobile) and Isobar EVO (second-generation, more mobile)-on the surgical and adjacent intervertebral disc segments, based on MRI findings.

METHODS

A retrospective analysis was conducted on 29 patients treated with fenestrated decompression and Isobar EVO stabilization and 34 patients treated with fenestrated decompression and Isobar TTL stabilization. Clinical outcomes and radiographic parameters, including the disc height index (DHI) and range of motion (ROM) of the surgical and upper adjacent segments, lateral neural foraminal protrusion value (LNPV) of the upper adjacent segment, and Pfirrmann grading of disc degeneration, were evaluated and compared between the two groups.

RESULTS

At the 48-month follow-up, no significant differences in Visual Analog Scale (VAS) scores or Oswestry Disability Index (ODI) were observed between the two groups (P > 0.01). The EVO group demonstrated significantly higher surgical segment DHI and ROM compared to the TTL group (P < 0.01). Meanwhile, the upper adjacent segment ROM was significantly lower in the EVO group compared to the TTL group at the final follow-up (P < 0.01). Additionally, the upper adjacent segment LNPV was larger in the EVO group than in the TTL group (P < 0.01). Pfirrmann grading revealed greater degeneration in surgical segments treated with TTL compared to EVO (P = 0.008).

CONCLUSION

Compared to the first-generation, less mobile Isobar TTL, the second-generation, more mobile Isobar EVO offers superior preservation of the surgical segment and slows the progression of degeneration in the upper adjacent segments. These findings highlight the benefits of greater mobility in posterior dynamic stabilization devices.

Long-term Outcome of Isobar TTL System for the Treatment of Lumbar Degenerative Disc Diseases

OBJECTIVE

The Isobar TTL dynamic fixation system has demonstrated favorable outcomes in the short-term treatment of lumbar degenerative disc diseases (LDDs). However, there is a paucity of extensive research on the long-term effects of this system on LDDs. This study aimed to evaluate the long-term clinical and radiological outcomes of patients with LDDs who underwent treatment utilizing the Isobar TTL dynamic fixation system.

METHODS

The study analyzed the outcomes of 40 patients with LDDs who underwent posterior lumbar decompression and received single-segment Isobar TTL dynamic internal fixation at our hospital between June 2010 and December 2016. The evaluation of clinical therapeutic effect involved assessing postoperative pain levels using the visual analogue scale (VAS) and Oswestry disability index (ODI), both before surgery, 3 months after, and the final follow-up. To determine the preservation of functional motion in dynamically stable segments, we measured the range of motion (ROM) and disc height of stabilized and adjacent segments preoperatively and during the final follow-up. Additionally, we investigated the occurrence of adjacent segment degeneration (ASD).

RESULTS

Forty patients were evaluated, with an average age of 44.65 years and an average follow-up period of 79.37 months. Fourteen patients belonged to the spondylolisthesis group, while the remaining 26 were categorized under the stenosis or herniated disc group. The preoperative ROM of the stabilized segment exhibited a significant reduction from 8.15° ± 2.77° to 5.00° ± 1.82° at the final follow-up (p < 0.001). In contrast, there was a slight elevation in the ROM of the adjacent segment during the final follow-up, increasing from 7.68° ± 2.25° before surgery to 9.36° ± 1.98° (p < 0.001). The intervertebral space height (IH) in the stabilized segment exhibited a significant increase from 10.56 ± 1.99 mm before surgery to 11.39 ± 1.90 mm at the one-week postoperative follow-up (p < 0.001). Conversely, there was a notable decrease in the IH of the adjacent segment from 11.09 ± 1.82 mm preoperatively to 10.86 ± 1.79 mm at the one-week follow-up after surgery (p < 0.001). The incidence of ASD was 15% (6/40) after an average follow-up period of 79.37 months, with a rate of 15.38% (4/26) in the stenosis or herniated disc group and 14.29% (2/14) in the spondylolisthesis group; however, no statistically significant difference was observed in the occurrence of ASD among these groups (p > 0.05).

CONCLUSION

The Isobar TTL dynamic fixation system is an effective treatment for LDDs, improving pain relief, quality of life (QoL) and maintaining stabilized segmental motion. It has demonstrated excellent long-term clinical and radiographic results.

Biomechanical and clinical research of Isobar semi-rigid stabilization devices for lumbar degenerative diseases: a systematic review

While lumbar spinal fusion using rigid rods is a prevalent surgical technique, it can lead to complications such as adjacent segment disease (ASDis). Dynamic stabilization devices serve to maintain physiological spinal motion and alleviate painful stress, yet they are accompanied by a substantial incidence of construct failure and subsequent reoperation. Compared to traditional rigid devices, Isobar TTL semi-rigid stabilization devices demonstrate equivalent stiffness and effective stabilization capabilities. Furthermore, when contrasted with dynamic stabilization techniques, semi-rigid stabilization offers improved load distribution, a broader range of motion within the fixed segment, and reduced mechanical failure rates. This paper will review and evaluate the clinical and biomechanical performance of Isobar TTL semi-rigid stabilization devices. A literature search using the PubMed, EMBASE, CNKI, Wanfang, VIP, and Cochrane Library databases identified studies that met the eligibility criteria. Twenty-eight clinical studies and nine biomechanical studies were included in this systematic review. The VAS, the ODI, and Japanese Orthopedic Association scoring improved significantly in most studies. UCLA grading scale, Pfirrmann grading, and modified Pfirrmann grading of the upper adjacent segments improved significantly in most studies. The occurrence rate of ASD was low. In biomechanical studies, Isobar TTL demonstrated a superior load sharing distribution, a larger fixed segment range of motion, and reduced stress at the rod-screw/screw-bone interfaces compared with titanium rods. While findings from mechanical studies provided promising results, the clinical studies exhibited low methodological quality. As a result, the available evidence does not possess sufficient strength to substantiate superior outcomes with Isobar semi-rigid system in comparison to titanium rods. To establish more conclusive conclusions, further investigations incorporating improved protocols, larger sample sizes, and extended follow-up durations are warranted.

Lumbar disc rehydration after dynamic stabilization: A systematic review

BACKGROUND

Interbody fusion combined with posterior screw fixation is a traditional method used for treating lumbar degenerative disease (LDD). But in recent years, there have been more and more reports about its complications. Dynamic Stabilization Systems (DSS) are another method for the treatment of LDD, but the clinical results are still inconclusive. The objective of this study is to review, analyze, and discuss the probability of disc rehydration by DSS designed for LDD by systematically reviewing previous relevant studies.

METHODS

The Pubmed, Web of Science, and Embase databases were searched using keywords for articles published before June 2022. The following keywords were used: rehydration, rehydrated, lumbar, spine, disc, spinal, degenerative disc disease, degenerative spine disease, vertebrae, vertebral column, thoracolumbar, and lumbosacral. The included studies were printed in English. Two independent investigators compiled all data. For the quality assessment, the Newcastle-Ottawa Scale was used to evaluate case-control studies, while the Joanna Briggs Institute critical appraisal checklist was used to evaluate the case series studies.

RESULTS

This systematic review included 7 studies comprised of 5 case series and 2 case-control studies. Seven articles involving 199 cases were enrolled for the data extraction. Of the 199 cases, 55 cases observed rehydration, as evaluated by Pfrimann grading on magnetic resonance imaging. The rehydration rate was 27.6% (55/199). DSS can provide positive clinical outcomes. Both visual analog scale and Oswestry Dysfunctional Index scores were significantly improved at the final follow-up.

CONCLUSION

DSS may promote disc rehydration and delay the development of LDD to some extent. Mechanical stretch may play an important role in the progress of intervertebral disc rehydration. It provides important evidence for the clinical application of DSS.

Comparison between single-segment Isobar EVO dynamic stabilization and Isobar TTL dynamic stabilization in the treatment of lumbar degenerative diseases: a single center retrospective study over 4 years

Objective

Posterior instrumented fusion is the most widely accepted surgical treatment for spinal stenosis and disc herniation. However, fusion can affect daily activities due to lumbar stiffness. In recent years, dynamic stabilization has been introduced to overcome the drawbacks of fusion, however, it is inconclusive whether dynamic stabilization requires the maintenance of a level of activity that is closer to the physiological state of activity for better clinical efficacy. The purpose of this study was to compare the effectiveness of dynamic stabilization with different levels of activity (Isobar EVO and TTL) in the treatment of spinal stenosis and disc herniation.

Methods

This study retrospectively reviewed 80 consecutive patients with lumbar degenerative diseases who were undergoing surgical treatment between March 2014 and July 2018. 41 patients (EVO group) and 39 patients (TTL group) underwent fenestrated decompression with Isobar EVO stabilization and Isobar TTL stabilization, respectively. Clinical outcomes, radiographic data, and postoperative complications were compared between the two groups.

Results

At an average follow-up of 52.23 ± 2.97 months, there were no significant differences in the oswestry disability index (ODI) (P > 0.05). The visual analog scale for back pain (VAS_back) and visual analog scale for the leg pain (VAS_leg) of the EVO group were lower compared with the TTL group (P < 0.05). The range of motion (ROM) of operated segments were significantly higher in the EVO group as compared to the TTL group (P < 0.05). The intervertebral space height (ISH) of upper adjacent segments were significantly higher in the EVO group as compared to the TTL group (P < 0.05). The overall complications were less in the EVO group, but the difference was not statistically significant (P > 0.05).

Conclusion

Both Isobar EVO dynamic stabilization and TTL dynamic stabilization can improve clinical outcomes of patients with spinal stenosis and disc herniation. Isobar EVO has advantages over Isobar TTL in terms of improving low back and leg pain, maintaining mobility of the operated segment, and preventing further degeneration of the upper adjacent segment.

Effects of posterior lumbar nonfusion surgery with isobar devices versus posterior lumbar interbody fusion surgery on clinical and radiological features in patients with lumbar degenerative diseases: a meta-analysis

Purpose

The aim of this study was to systematically evaluate the efficacy of posterior lumbar isobar nonfusion with isobar devices versus posterior lumbar interbody fusion (PLIF) in the treatment of patients with lumbar degenerative diseases (LDDs).

Materials and method

We performed a literature review and meta-analysis in accordance with the Cochrane methodology. The analysis included a Group Reading Assessment and Diagnostic Evaluation assessments, Jadad Quality Score evaluations, and Risk of Bias in Randomized Studies of Interventions assessments. The PubMed, Ovid, EMBASE, Web of Science, MEDLINE, CNKI, VIP and WanFang databases were searched to collect and compare relevant randomized controlled trials and cohort studies of isobar nonfusion and PLIF in the treatment of lumbar degenerative diseases. The retrieval time was from database inception to June 2021. Two evaluators independently screened the literature, extracted data, and evaluated the quality of the included studies. Outcome measures of interest included low back pain, disability, and radiological features. The protocol for this systematic review was registered on INPLASY (2021110059) and is available in full on inplasy.com (https://inplasy.com/inplasy-2021-11-0059/).

Results

Of the 7 RCTs, 394 patients met the inclusion criteria. The meta-analysis results showed that isobar nonfusion surgery shortened the surgical duration (P = 0.03), reducing intraoperative bleeding (P = 0.001), retained the ROM of surgical segment (P < 0.00001) and the ROM of the lumbar spine (P < 0.00001), and reduced the incidence of ASD (P = 0.0001). However, no significant difference in the postoperative ODI index (P = 0.81), VAS score of LBP (P = 0.59, VAS score of lower limb pain (P = 0.05, and JOA score (P = 0.27) was noted.

Conclusions

Posterior lumbar nonfusion surgery with isobar devices is superior to PLIF in shortening the surgical duration, reducing intraoperative bleeding, retaining the ROM of surgical segments and the lumbar spine to a certain extent, and preventing ASD. Given the possible publication bias, we recommend further large-scale studies.

Lumbar disc rehydration in the bridged segment using the BioFlex dynamic stabilization system: A case report and literature review

BACKGROUND

In recent years, the mechanical concept of intervertebral disc regeneration has become more and more popular due to the increasing awareness of the importance of preservation of spine movement. Interestingly, there is increasing evidence, however, that dynamic stabilization systems may compensate non-physiological loads, limit pathological movement, normalize disc height and intradiscal pressure, and provide an adaptive environment for disc regeneration.

CASE SUMMARY

The patient was a 54-year-old man, who presented with a 10-year history of mechanical back pain, which had become progressively serious and radiated into the left lower limb with numbness 3 mo prior. He had decreased muscle strength (class IV) of the left dorsal extensor and plantar flexor. Magnetic resonance imaging scans showed L3-S1 disc degeneration and L4-L5 disc herniation. Because the patient did not respond to various conservative treatments, he underwent a posterior L4-5 discectomy with fixation of the BioFlex dynamic stabilization system (Bio-Spine, Seoul, Korea). Preoperative symptoms were relieved and lumbar function was markedly improved after the operation. L4-L5 disc rehydration of instrumented segment was noted on magnetic resonance imaging at the 2-year follow-up.

CONCLUSION

Rehydration of the degenerated disc in our patient indicates that the BioFlex dynamic stabilization system may promote disc regeneration. Further research is needed to provide more evidence to support lumbar disc rehydration in the bridged segment using this system.

Effects of Lumbar Fusion Surgery with ISOBAR Devices Versus Posterior Lumbar Interbody Fusion Surgery on Pain and Disability in Patients with Lumbar Degenerative Diseases: A Meta-Analysis

Purpose/Aim: Lumbar degenerative diseases (LDDs) cause pain and disability and are treated with lumbar fusion surgery. The aim of this study was to evaluate the efficacy of lumbar fusion surgery with ISOBAR devices versus posterior lumbar interbody fusion (PLIF) surgery for alleviating LDD-associated pain and disability. Materials and Methods: We performed a literature review and meta-analysis conducted in accordance with Cochrane methodology. The analysis included Group Reading Assessment and Diagnostic Evaluation assessments, Jadad Quality Score evaluations, and Risk of Bias in Non-randomized Studies of Interventions assessments. We searched PubMed, MEDLINE, the Cumulative Index to Nursing and Allied Health Literature, the Cochrane Library, ProQuest, the Airiti Library, and the China Academic Journals Full-text Database for relevant randomized controlled trials and cohort studies published in English or Chinese between 1997 and 2017. Outcome measures of interest included general pain, lower back pain, and disability. Results: Of the 18 studies that met the inclusion criteria, 16 examined general pain (802 patients), 5 examined lower back pain (274 patients), and 15 examined disability (734 patients). General pain, lower back pain, and disability scores were significantly lower after lumbar fusion surgery with ISOBAR devices compared to presurgery. Moreover, lumbar fusion surgery with ISOBAR devices was more effective than PLIF for decreasing postoperative disability, although it did not provide any benefit in terms of general pain or lower back pain. Conclusions: Lumbar fusion surgery with ISOBAR devices alleviates general pain, lower back pain, and disability in LDD patients and is superior to PLIF for reducing postoperative disability. Given possible publication bias, we recommend further large-scale studies.

Low Magnitude of Compression Enhances Biosynthesis of Mesenchymal Stem Cells towards Nucleus Pulposus Cells via the TRPV4-Dependent Pathway

Mesenchymal stem cell- (MSC-) based therapy is regarded as a promising tissue engineering strategy to achieve nucleus pulposus (NP) regeneration for the treatment of intervertebral disc degeneration (IDD). However, it is still a challenge to promote the biosynthesis of MSC to meet the requirement of NP regeneration. The purpose of this study was to optimize the compressive magnitude to enhance the extracellular matrix (ECM) deposition towards discogenesis of MSCs. Thus, we constructed a 3D culture model for MSCs to bear different magnitudes of compression for 7 days (5%, 10%, and 20% at the frequency of 1.0 Hz for 8 hours/day) using an intelligent and mechanically active bioreactor. Then, the underlying mechanotransduction mechanism of transient receptor potential vanilloid 4 (TRPV4) was further explored. The MSC-encapsulated hybrids were evaluated by Live/Dead staining, biochemical content assay, real-time PCR, Western blot, histological, and immunohistochemical analysis. The results showed that low-magnitude compression promoted anabolic response where high-magnitude compression induced the catabolic response for the 3D-cultured MSCs. The anabolic effect of low-magnitude compression could be inhibited by inhibiting TRPV4. Meanwhile, the activation of TRPV4 enhanced the biosynthesis analogous to low-magnitude compression. These findings demonstrate that low-magnitude compression promoted the anabolic response of ECM deposition towards discogenesis for the 3D-cultured MSCs and the TRPV4 channel plays a key role on mechanical signal transduction for low-magnitude compressive loading. Further understanding of this mechanism may provide insights into the development of new therapies for MSC-based NP regeneration.

Comparison of Adjacent Segment Degeneration After Nonrigid Fixation System and Posterior Lumbar Interbody Fusion for Single-Level Lumbar Disc Herniation: A New Method of MRI Analysis of Lumbar Nucleus Pulposus Volume

PURPOSE

To evaluate the influence of a nonrigid fixation system and posterior lumbar interbody fusion on adjacent intervertebral disc degeneration by using MRI analysis of lumbar nucleus pulposus volume for single-level lumbar disc herniation.

MATERIALS AND METHODS

We selected 112 patients who underwent nonrigid fixation (17 men and 44 women) or posterior lumbar interbody fusion (13 men and 38 women) for this retrospective study. Based on the T2-weighted magnetic resonance imaging (MRI) scans taken preoperatively, and 6, 12, and 24 months after surgery, the nucleus pulposus in the upper segments of the operated level was considered an ellipsoid, and their volumes were measured respectively and then compared between the two groups.

RESULTS

The posterior lumbar interbody fusion group had significantly lower lumbar nucleus pulposus volume than the nonrigid fixation group at 12 (4.04 ± 1.42 vs. 5.25 ± 1.47 mm³) and 24 months (4.16 ± 0.89 vs. 5.06 ± 1.23 mm³), and had the highest nucleus pulposus. Meanwhile, the h value in the posterior lumbar interbody fusion group was notably smaller than the preoperative level at 12 (0.46 ± 0.03 vs. 0.55 ± 0.05 mm) and 24 months (0.44 ± 0.03 vs. 0.55 ± 0.05 mm).

CONCLUSIONS

MRI analysis of lumbar nucleus pulposus volume is a new and quantitative method of analysis, which is a considerable method and contributes to the detection of severe intervertebral disc degeneration. Based on this new method, nonrigid fixation demonstrates excellent outcomes on the adjacent segment in comparison with posterior lumbar interbody fusion.

Posterior Dynamic Stabilization With Direct Pars Repair via Wiltse Approach for the Treatment of Lumbar Spondylolysis: The Application of a Novel Surgery

STUDY DESIGN

A retrospective study to evaluate the clinical outcomes of a novel surgical method for treating patients with lumbar spondylolysis.

OBJECTIVE

The aim of this study was to investigate the effectiveness of posterior ISOBAR TTL stabilization of the lumbar spine with direct pars repair using Wiltse approach for the treatment of lumbar spondylolysis with or without slight spondylolisthesis and discuss the indications of this surgery.

SUMMARY OF BACKGROUND DATA

Surgical treatment of lumbar spondylolysis has yielded relatively good results. However, there are still many limitations of the current surgical methods, including, adjacent level degeneration, restricted indications, and soft tissue damage.

METHODS

Between August 2010 and January 2013, 13 (9 males and 4 females; mean age: 28.2 yrs), patients with lumbar spondylolysis with or without slight spondylolisthesis underwent posterior ISOBAR TTL stabilization of the lumbar spine, with direct pars repair via Wiltse approach. All patients were followed up for at least 24 months at outpatient visits or telephonically. Pre-operative and postoperative radiological assessments included anteroposterior, lateral and flexion extension radiographs, 3-dimensional reconstruction computed tomography (CT), and magnetic resonance imaging (MRI). Data pertaining to intraoperative blood loss, duration of operation, visual analog score (VAS), Oswestry disability index (ODI) scores, and other assessments were collected.

RESULTS

The median follow-up duration was 36 months (range, 24-53 months). Surgery was successful in all patients with no complications; bony fusion of pars was confirmed on CT scan at postoperative 2 years. Significant pain relief was achieved in all patients including those with discogenic pain, those >30 years of age, and those with severe disc degeneration (P < 0.01).

CONCLUSION

We evaluated a new surgical technique for the treatment of patients with spondylolysis with or without slight spondylolisthesis. Besides the good clinical results, the indications for this new surgery are much wider and can potentially overcome the limitations of earlier techniques.

LEVEL OF EVIDENCE

4.