Mid- to long-term results of total disc replacement for lumbar degenerative disc disease: a systematic review

Biomolecular therapies for chronic discogenic low back pain: A narrative review

Chronic low back pain caused by intervertebral disc (IVD) degeneration, also termed chronic discogenic low back pain (CD-LBP), is one of the most prevalent musculoskeletal diseases. Degenerative processes in the IVD, such as inflammation and extra-cellular matrix breakdown, result in neurotrophin release. Local elevated neurotrophin levels will stimulate sprouting and innervation of sensory neurons. Furthermore, sprouted sensory nerves that are directly connected to adjacent dorsal root ganglia have shown to increase microglia activation, contributing to the maintenance and chronification of pain. Current pain treatments have shown to be insufficient or inadequate for long-term usage. Furthermore, most therapeutic approaches aimed to target the underlying pathogenesis of disc degeneration focus on repair and regeneration and neglect chronic pain. How biomolecular therapies influence the degenerative IVD environment, pain signaling cascades, and innervation and excitability of the sensory neurons often remains unclear. This review addresses the relatively underexplored area of chronic pain treatment for CD-LBP and summarizes effects of therapies aimed for CD-LBP with special emphasis on chronic pain. Approaches based on blocking pro-inflammatory mediators or neurotrophin activity have been shown to hamper neuronal ingrowth into the disc. Furthermore, the tissue regenerative and neuro inhibitory properties of extracellular matrix components or transplanted mesenchymal stem cells are potentially interesting biomolecular approaches to not only block IVD degeneration but also impede pain sensitization. At present, most biomolecular therapies are based on acute IVD degeneration models and thus do not reflect the real clinical chronic pain situation in CD-LBP patients. Future studies should aim at investigating the effects of therapeutic interventions applied in chronic degenerated discs containing established sensory nerve ingrowth. The in-depth understanding of the ramifications from biomolecular therapies on pain (chronification) pathways and pain relief in CD-LBP could help narrow the gap between the pre-clinical bench and clinical bedside for novel CD-LBP therapeutics and optimize pain treatment.

On the suitability of additively manufactured gyroid structures and their potential use as intervertebral disk replacement - a feasibility study

Introduction

Intervertebral disk degeneration is a growing problem in our society. The degeneration of the intervertebral disk leads to back pain and in some cases to a herniated disk. Advanced disk degeneration can be treated surgically with either a vertebral body fusion or a disk prosthesis. Vertebral body fusion is currently considered the gold standard of surgical therapy and is clearly superior to disk prosthesis based on the number of cases. The aim of this work was the 3D printing of Gyroid structures and the determination of their mechanical properties in a biomechanical feasibility study for possible use as an intervertebral disc prosthesis.

Material and methods

Creo Parametric 6.0.6.0 was used to create models with various Gyroid properties. These were printed with the Original Prusa i3 MK3s+. Different flexible filaments (TPU FlexHard and TPU FlexMed, extrudr, Lauterach, Austria) were used to investigate the effects of the filament on the printing results and mechanical properties of the models. Characterization was carried out by means of microscopy and tension/compression testing on the universal testing machine.

Results

The 3D prints with the FlexHard and FlexMid filament went without any problems. No printing errors were detected in the microscopy. The mechanical confined compression test resulted in force-deformation curves of the individual printed models. This showed that changing the Gyroid properties (increasing the wall thickness or density of the Gyroid) leads to changes in the force-deformation curves and thus to the mechanical properties.

Conlcusion

The flexible filaments used in this work showed good print quality after the printing parameters were adjusted. The mechanical properties of the discs were also promising. The parameters Gyroid volume, wall thickness of the Gyroid and the outer wall played a decisive role for both FlexMed and FlexHard. All in all, the Gyroid structured discs (Ø 50 mm) made of TPU represent a promising approach with regard to intervertebral disc replacement. We would like to continue to pursue this approach in the future.

Lumbar Total Disc Replacements for Degenerative Disc Disease: A Systematic Review of Outcomes With a Minimum of 5 years Follow-Up

STUDY DESIGN

Systematic Review.

OBJECTIVES

To systematically review the clinical outcomes, re-operation, and complication rates of lumbar TDR devices at mid-to long-term follow-up studies for the treatment of lumbar degenerative disc disease (DDD).

METHODS

A systematic search was conducted on PubMed, SCOPUS, and Google Scholar to identify follow-up studies that evaluated clinical outcomes of lumbar TDR in patients with DDD. The included studies met the following criteria: prospective or retrospective studies published from 2012 to 2022; a minimum of 5 years post-operative follow-up; a study sample size >10 patients; patients >18 years of age; containing clinical outcomes with Oswestry Disability Index (ODI), Visual Analog Scale (VAS), complication or reoperation rates.

RESULTS

Twenty-two studies were included with data on 2284 patients. The mean follow-up time was 8.30 years, with a mean follow-up rate of 86.91%. The study population was 54.97% female, with a mean age of 42.34 years. The mean VAS and ODI pain score improvements were 50.71 ± 6.91 and 30.39 ± 5.32 respectively. The mean clinical success and patient satisfaction rates were 74.79% ± 7.55% and 86.34% ± 5.64%, respectively. The mean complication and reoperation rates were 18.53% ± 6.33% and 13.6% ± 3.83%, respectively. There was no significant difference when comparing mid-term and long-term follow-up studies for all clinical outcomes.

CONCLUSIONS

There were significant improvements in pain reduction at last follow-up in patients with TDRs. Mid-term follow-up data on clinical outcomes, complication and reoperation rates of lumbar TDRs were maintained longer term.

Long-Term Results of Charité Lumbar Disc Replacement: A 17-Year Follow-Up in a Workers' Compensation Cohort

BACKGROUND

Lumbar total disc replacement (TDR) is an alternative to lumbar fusion for the management of degenerative disc disease. This study aims to provide insight into the long-term clinical outcomes of lumbar TDR with a mean follow-up of 17.2 years in a group of workers' compensation patients.

METHODS

A total of 26 workers' compensation patients with radiographically confirmed discogenic low back pain were treated with the Charité total lumbar disc replacement. Visual analog scale (VAS) scores were assessed before and after the surgery. At follow-up, patients were assessed on quality of life, employment, further lumbar spine surgeries, and associated complications. Simple nonparametric statistical analysis was performed by the first author using Microsoft Excel.

RESULTS

Sixteen patients (62%) were able to be contacted with a mean follow-up time of 17.2 years. VAS scores at 17 years were significantly lower than their preoperation level. Of those 16 patients, 81% returned to work and worked for an average of 9.1 years after surgery. Additionally, 6 (38%) patients underwent further lumbar spinal surgery, of whom 4 underwent fusions of the adjacent segment. Nearly all patients (94%) were satisfied with the surgery.

CONCLUSION

This study suggests lumbar TDR may be a useful treatment for degenerative disc disease in select workers' compensation patients.

CLINICAL RELEVANCE

Clinically relevant improvements in pain and employment can be achieved with the charite lumbar TDR in the treatment of degenerative disc disease in workers' compensation patients. These results are sustained over the long term.

LEVEL OF EVIDENCE: 4

Clinical Efficacy and Safety of Human Mesenchymal Stem Cell Therapy for Degenerative Disc Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Degenerative disc disease (DDD) can cause severe low back pain, which will have a serious negative impact on the ability to perform daily tasks or activities. For the past few years, mesenchymal stem cell (MSC) transplantation has emerged as a promising strategy for the treatment of DDD. However, the clinical efficacy of MSC in the treatment of DDD still lacks clinical evidence and is controversial. We conducted a meta-analysis with randomized controlled trials (RCTs) to evaluate the clinical efficacy and safety of MSC transplantation in patients with DDD. We searched major databases using terms from the database's inception through March 2021. The Cochrane bias risk assessment tool was used to assess quality. The analysis showed that MSC therapy could decrease visual analog scale (VAS) scores (SMD = −0.50, 95%CI = −0.68 ~ −0.33, P < 0.00001) and Oswestry Disability Index (ODI) scores (SMD = −0.27, 95%CI = −0.44 ~ −0.09, P = 0.003). The outcomes with subgroup analysis showed that MSC therapy could decrease VAS scores in 3 months (P = 0.001), 6 months (P = 0.01), 12 months (P = 0.02), and ≥24 months (P = 0.002) and ODI scores in ≥24 months (P = 0.006). Pooled analysis showed that MSC therapy has a higher ratio of patients at most thresholds but particularly at the MIC (minimally important change) (P = 0.0002) and CSC (clinically significant change) (P = 0.0002) in VAS and MIC (P = 0.0005) and CSC (P = 0.001) pain responders in ODI. Adverse events (AE) of treatment-emergent adverse events (TEAE), back pain, arthralgia, and muscle spasms were not statistically significant between the two groups. However, our further statistical analysis showed that MSC therapy may induce AE of TEAE related to study treatment (OR = 3.05, 95%CI = 1.11 ~ 8.40, P = 0.03). In conclusion, this study pooled the main outcomes and showed that MSC therapy could significantly decrease VAS and ODI scores in patients with DDD. Distinctly, the findings of this meta-analysis suggest a novel therapeutic strategy for patients with chronic low back pain (LBP) and lumbar dysfunction by DDD.

Intervertebral Disk Degeneration: The Microenvironment and Tissue Engineering Strategies

Intervertebral disk degeneration (IVDD) is a leading cause of disability. The degeneration is inevitable, and the mechanisms are complex. Current therapeutic strategies mainly focus on the relief of symptoms, not the intrinsic regeneration of the intervertebral disk (IVD). Tissue engineering is a promising strategy for IVDD due to its ability to restore a healthy microenvironment and promote IVD regeneration. This review briefly summarizes the IVD anatomy and composition and then sets out elements of the microenvironment and the interactions. We rationalized different scaffolds based on tissue engineering strategies used recently. To fulfill the complete restoration of a healthy IVD microenvironment, we propose that various tissue engineering strategies should be combined and customized to create personalized therapeutic strategies for each individual.

Proper animal experimental designs for preclinical research of biomaterials for intervertebral disc regeneration

Low back pain is a vital musculoskeletal disease that impairs life quality, leads to disability and imposes heavy economic burden on the society, while it is greatly attributed to intervertebral disc degeneration (IDD). However, the existing treatments, such as medicines, chiropractic adjustments and surgery, cannot achieve ideal disc regeneration. Therefore, advanced bioactive therapies are implemented, including stem cells delivery, bioreagents administration, and implantation of biomaterials etc. Among these researches, few reported unsatisfying regenerative outcomes. However, these advanced therapies have barely achieved successful clinical translation. The main reason for the inconsistency between satisfying preclinical results and poor clinical translation may largely rely on the animal models that cannot actually simulate the human disc degeneration. The inappropriate animal model also leads to difficulties in comparing the efficacies among biomaterials in different reaches. Therefore, animal models that better simulate the clinical charateristics of human IDD should be acknowledged. In addition, in vivo regenerative outcomes should be carefully evaluated to obtain robust results. Nevertheless, many researches neglect certain critical characteristics, such as adhesive properties for biomaterials blocking annulus fibrosus defects and hyperalgesia that is closely related to the clinical manifestations, e.g., low back pain. Herein, in this review, we summarized the animal models established for IDD, and highlighted the proper models and parameters that may result in acknowledged IDD models. Then, we discussed the existing biomaterials for disc regeneration and the characteristics that should be considered for regenerating different parts of discs. Finally, well-established assays and parameters for in vivo disc regeneration are explored.

Segmental Lordosis Gain Is a Prognostic Radiological Factor of Good Functional Outcome After the Implantation of a Single-Level Prosthesis or a Hybrid Construct for Lumbar Disc Degeneration

OBJECTIVE

To identify radiological factors and functional outcomes associated with good results after implantation of a single lumbar disc prosthesis or a hybrid construct (anterior lumbar interbody fusion and lumbar disc prosthesis) in the setting of painful degenerative lumbar discopathy.

METHODS

This single-center, retrospective 10-year study included 92 patients ˃18 years old with chronic low back pain evolving for at least 1 year. The patients had degenerative disc disease and had failed conservative treatment and underwent lumbar arthroplasty. Radiographic and clinical outcomes were assessed preoperatively and 1 year after surgery. Functional evaluation was based on the Oswestry Disability Index (ODI) and a numerical rating scale. Radiological analysis was based on lumbar x-rays and magnetic resonance imaging parameters. Patients were assigned to 2 groups according to the reduction in ODI score (>15 points or <15 points), and statistical analysis was done in both groups to find predictive radiological factors for a satisfactory functional outcome.

RESULTS

Clinically, 60 patients (65.2%) had a satisfactory functional result and 32 patients (34.8%) had a poor outcome according to ODI score. Radiographically, gain in segmental lordosis was statistically associated with good functional outcomes (8.9° for ODI decrease >15 vs. 3.2° for ODI decrease <15).

CONCLUSIONS

This study determined that gain in segmental lordosis is associated with a satisfactory functional outcome after a single-level lumbar disc prosthesis or a hybrid construct. Our study demonstrates that segmental lordosis gain may represent a significative useful positive predictor factor of patient outcome.

Comparison of total disc arthroplasty and fusion in treatment of lumbar disc disease: A cohort study protocol

BACKGROUND

In recent years, the clinical efficacy of spinal fusion (SF) or total disc arthroplasty (TDA) in the treatment of the degenerative lumbar disc disease is still controversial. The objective of this retrospective clinical trial was to investigate whether TDA was superior to the SF in the complication rates and clinical outcome scores.

METHODS

This retrospective research was based on the Strengthening the Reporting of Observational studies in Epidemiology checklist. Internal clinical data sets for 2014 to 2018 were acquired and consolidated with the approval of the Institutional Review Committee of Shaoxing Hospital of Zhejiang University. Inclusion criteria in this present research included: low back pain without or with the leg pain for more than one year; failure of conservative treatment planned for more than three months; age was 25 to 60 years old; followed up for at least one year. The main outcome measure was disability and pain measured via the Norwegian version of Oswestry disability index 2.0. The other clinical outcomes included Short-Form Health Survey, reoperations, duration of surgery, complications, hospital stay length, as well as the blood loss. The significance was set at 0.05 level with the confidence intervals of 95%. The software package of SPSS (version 21.0; SPSS Inc, Chicago, IL, USA) was applied for all the analyses of statistics.

RESULTS

The null hypothesis is that there is no significant difference in outcomes between TDA and SF in the treatment of degenerative lumbar disc disease.

TRIAL REGISTRATION

This study protocol was registered in Research Registry (researchregistry5847).

ICR in human cadaveric specimens: An essential parameter to consider in a new lumbar disc prosthesis design

STUDY DESIGN

Biomechanical study in cadaveric specimens.

BACKGROUND

The commercially available lumbar disc prostheses do not reproduce the intact disc's Instantaneous centre of Rotation (ICR), thus inducing an overload on adjacent anatomical structures, promoting secondary degeneration.

AIM

To examine biomechanical testing of cadaveric lumbar spine specimens in order to evaluate and define the ICR of intact lumbar discs.

MATERIAL AND METHODS

Twelve cold preserved fresh human cadaveric lumbosacral spine specimens were subjected to computerized tomography (CT), magnetic resonance imaging (MRI) and biomechanical testing. Kinematic studies were performed to analyse range of movements in order to determine ICR.

RESULTS

Flexoextension and lateral bending tests showed a positive linear correlation between the angle rotated and the displacement of the ICR in different axes.

DISCUSSION

ICR has not been taken into account in any of the available literature regarding lumbar disc prosthesis. Considering our results, neither the actual ball-and-socket nor the withdrawn elastomeric nucleus models fit the biomechanics of the lumbar spine, which could at least in part explain the failure rates of the implants in terms of postoperative failed back syndrome (low back pain). It is reasonable to consider then that an implant should also adapt the equations of the movement of the intact ICR of the joint to the post-surgical ICR.

CONCLUSIONS

This is the first cadaveric study on the ICR of the human lumbar spine. We have shown that it is feasible to calculate and consider this parameter in order to design future prosthesis with improved clinical and biomechanical characteristics.

Revision surgery of spinal dynamic implants: a literature review and algorithm proposal

INTRODUCTION

Dynamic stabilization of the spine has been performed since the 1990s with the double purpose of restoring spinal segmental stability and allowing residual movement at the operated level. When we take into account the different motion-preserving devices and the spinal areas where they are applied, we can identify three categories of spinal implants: anterior cervical, anterior lumbar, and posterior lumbar. However, as in all prosthetic procedures performed in orthopedic surgery, the life span of a joint replacement device is a central topic of discussion, and this is true also for spinal dynamic devices, being revision surgery a complex procedure in specific cases.

MATERIALS AND METHODS

We performed a literature review on the different dynamic spinal implants and the most common causes of failure, providing clinical cases as illustrative options for revision surgery.

RESULTS

The review of the literature showed a 11.3% to 22.6% revision rate in posterior lumbar dynamic systems, with a peak of 40.6% in case of adjacent segment disease. In lumbar TDRs, infection and severe dislocations are the most frequent causes of anterior revisions, while posterior pedicle screw fixation could be a suitable option in minimal subsidence or TDR displacement. An algorithm for the planning of revision surgery is proposed.

CONCLUSIONS

Surgical revision of spinal dynamic implants could be a demanding surgery especially in anterior approaches. Anterior cervical revision remains globally safe, but careful preoperative evaluation of vessels and ureter are suggested to avoid intraoperative complications in the lumbar spine. In posterior revision, a proper sagittal alignment of the spine should be restored. These slides can be retrieved under Electronic Supplementary Material.

Artificial disc replacement in spine surgery

Total disc replacement (TDR) is an innovative procedure that has gained traction in spine surgery. A large amount of data in the literature report on the short-term outcomes of TDR surgery favorably. However, surgeons remain reluctant to opt for TDR surgery due to uncertainty of long-term outcomes. Recently, long term data regarding TDR surgery has become available, with some studies showing superior outcomes to fusion surgery. The goal of this review is to synthesize and clinically contextualize the recent literature on TDR surgery. This article also provides brief discussion of the biggest challenges currently facing disc arthroplasties and the ways in which they are being tackled.