Intervertebral Disc Replacement Research Articles

Regenerative therapies for lumbar degenerative disc diseases: a literature review.

This review aimed to summarize the recent advances and challenges in the field of regenerative therapies for lumbar disc degeneration. The current first-line treatment options for symptomatic lumbar disc degeneration cannot modify the disease process or restore the normal structure, composition, and biomechanical function of the degenerated discs. Cell-based therapies tailored to facilitate intervertebral disc (IVD) regeneration have been developed to restore the IVD extracellular matrix or mitigate inflammatory conditions. Human clinical trials on Mesenchymal Stem Cells (MSCs) have reported promising outcomes exhibited by MSCs in reducing pain and improving function. Nucleus pulposus (NP) cells possess unique regenerative capacities. Biomaterials aimed at NP replacement in IVD regeneration, comprising synthetic and biological materials, aim to restore disc height and segmental stability without compromising the annulus fibrosus. Similarly, composite IVD replacements that combine various biomaterial strategies to mimic the native disc structure, including organized annulus fibrosus and NP components, have shown promise. Furthermore, preclinical studies on regenerative medicine therapies that utilize cells, biomaterials, growth factors, platelet-rich plasma (PRP), and biological agents have demonstrated their promise in repairing degenerated lumbar discs. However, these therapies are associated with significant limitations and challenges that hinder their clinical translation. Thus, further studies must be conducted to address these challenges.

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

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. 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. 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. 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 50mm) 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.

3D-printed titanium alloy cage in anterior and lateral lumbar interbody fusion for degenerative lumbar spine disease.

The most commonly used cages for intervertebral disc replacement in lumbar fusion procedures are made predominantly from polyetheretherketone (PEEK). There is sufficient data studying their subsidence and failure rates from a variety of approaches. A novel implant is now available for commercial use, 3D-printed porous titanium (3DppTi) alloy cages, which have recently become available for use in spinal procedures. They have been shown in ovine models to have superior efficacy and fusion rates compared to traditional cages. However, there is limited data on their use in clinical practice and long-term outcomes associated with them. A retrospective chart review was performed, of all patients in a single institution who underwent lumbar spine fusion surgery via an anterior or lateral approach with a 3D-printed titanium alloy cage, between January 2020 and February 2021. Clinic letters, imaging and operation reports were independently reviewed to assess for fusion, or evidence of subsidence on follow-up. Fifty patients were identified as meeting inclusion criteria, with a total of 66 operative levels. Of these operative levels, 32 were via an anterior approach and 34 via a lateral approach. One patient demonstrated a Marchi grade 0 subsidence, with recurrence of radiculopathy 2 months after an anterior approach, requiring posterior decompression and stabilization. A second patient demonstrated a Marchi grade 1 subsidence after a lateral approach, but did not require further surgery as they were asymptomatic at 2 years of follow-up. This study demonstrated an overall subsidence rate of 3.03%. There was a median follow-up time of 11.3 months for all patients. 3D-printed titanium alloy cages demonstrate a lower subsidence rate compared to historically published rates for alternative intervertebral cages, in anterior and lateral lumbar spine fusion surgery.

Are There Still Any Benefits to Drainage for Anterior Cervical Arthrodesis/Arthroplasty by Cervicotomy?

A retrospective single-center study between January 2019 and January 2023. The role and contribution of drainage in the anterior approach to the cervical spine (cervicotomy) is much debated, motivated primarily by the prevention of retropharyngeal hematoma, so are there still any benefits to drainage? The anterior approach to the cervical spine is a widespread and common procedure performed in almost all spine surgery departments for the replacement of cervical intervertebral discs and medullar or radicular decompression. The primary endpoint was the occurrence of symptomatic postoperative cervical hematoma. Four hundred thirty-one patients who had undergone cervical spine surgery by anterior cervicotomy for cervicarthrosis or cervical disc herniation (anterior cervical discectomy and fusion and anterior cervical disc replacement) were consecutively included. Patients were separated into 2 groups: (1) Group A, 140 patients (with postoperative drainage) and (2) Group B, 291 patients (without drainage). The mean follow-up was 2.8 months. The 2 groups were comparable on all criteria, but there was a predominance of arthroplasty ( P < 0.0001), use of anticoagulants/antiaggregants ( P < 0.0001) and a greater number of stages ( P < 0.0001) in group A. There were a total of 4/431 symptomatic postoperative hematomas (0.92%) in this study. Two hematomas occurred in group A (2/140, 1.4%) and 2 in group B (2/291, 0.68%; P < 0.0001). One patient in group A (0.71%) required surgical drainage for cavity hematoma revealed by marked dyspnea, swallowing, and neurological disorders. One case of hematoma diagnosed by dysphonia and neurological deficit was reported in group B (0.34%; P < 0.0001). The placement of a drain during anterior cervicotomy (anterior cervical discectomy and fusion/anterior cervical disc replacement) did not limit the occurrence of symptomatic postoperative hematoma.

Lumbar intervertebral disc replacement in Australia: An epidemiological study.

Favorable short- and long-term outcomes have been reported for lumbar intervertebral total disc replacement (L-TDR). However, there is little evidence regarding the uptake of L-TDR in practice. The objective of this study was to analyze Australian-based population trends in L-TDR over the past 5 years. The 5-year incidence of L-TDR from 2019 to 2023 in adult patients was analyzed using the Medicare Benefits Schedule (MBS) database. Data were stratified by sex and year, with an offset term introduced using population data from the Australian Bureau of Statistics to account for population changes over the study period. A total of 1558 L-TDRs were completed in Australia under the MBS in the 5 years of interest. The 5-year annual mean case volume was 311.6 cases per annum. A downtrend and plateau in the rate of L-TDR has been seen from 2021 onward. The distribution of L-TDR across ages showed a significantly higher concentration in the 35-44 and 45-54 age groups (P < 0.05). More operations were performed in males (n = 876, 56.2%) than females (n = 682, 43.8%). The uptake of L-TDR has declined throughout the 5-year study period in Australia. Despite modest use currently, the future of L-TDR will rely on more robust long-term outcome data.

Comparison of the effects of different artificial discs on hybrid surgery: A finite element analysis.

In recent years, artificial cervical discs have been used in intervertebral disc replacement surgery and hybrid surgery (HS). The advantages and disadvantages of different artificial cervical discs in artificial cervical disc replacement surgery have been compared. However, few scholars have studied the biomechanical effects of various artificial disc prostheses on the human cervical spine in HS which include the Anterior Cervical Discectomy and Fusion (ACDF) and Cervical Disc Arthroplasty (CDA). This study compared the biomechanical behavior of Mobi-C and Prestige LP in the operative and adjacent segments during two-level hybrid surgery. A three-dimensional finite element model of C2-C7 was first established and validated. Subsequently, clinical surgery was then simulated to establish a surgical model of anterior cervical fusion at the C4-C5 level. Mobi-C and Prestige-LP artificial disc prostheses were implanted at the C5-C6 level to create two hybrid models. All finite element models were fixed on the lower endplate of the C7 vertebra and subjected to a load of 73.6 N and different directions of 1 Nm torque on the odontoid process of the C2 vertebra to simulate human flexion, extension, lateral bending, and axial rotation. This paper compares the ROM, intervertebral pressure, and facet joint force after hybrid surgery with the intact model. The results show that compared with Prestige LP, Mobi-C can improve ROM of the replacement segment and compensate for the intervertebral pressure of the adjacent segment more effectively, but the facet joint pressure of the replacement segment may be higher.

Tricomponent polymer aerogels containing cellulose nanocrystals and chitin nanofibers and their use in aerogel/hydrogel hybrids as fibrocartilage replacements

AbstractConsidering the design of structures and materials for use as replacements for biological structures, polymer nanocomposites are desirable materials of construction since they have a large design space, allowing property customization. Biobased nanofibers are particularly suited for these applications since they have high specific mechanical properties and cytocompatibility. Motivated by these attributes, this work examines nanocomposite aerogels and an aerogel/hydrogel hybrid structure designed to mimic an intervertebral disc (IVD), with the aerogel and hydrogel serving as analogs for the annulus fibrosus and the nucleus pulposus, respectively. The aerogels and aerogel/hydrogel hybrid structure contain a mixture of biobased nanofibers, cellulose nanocrystals (CNCs) and chitin nanofibers (ChNFs), and a polyvinyl alcohol (PVA) matrix. Characterization of the structure and properties shows that the nanocomposite aerogels containing CNC/ChNF mixtures have larger pores and decreased mechanical properties as compared to aerogels containing only CNCs or only ChNFs. Building on these results, a hybrid comprised of a CNC/PVA aerogel and a CNC/ChNF/PVA hydrogel is constructed with mechanical properties similar to natural IVDs, providing initial validation of the hybrid concept for IVD replacements and pathways to customization through changing material composition in the aerogel and hydrogel and changing the aerogel and hydrogel fractions in the hybrid structure.

Combining Laminoplasty With Artificial Disc Replacement for the Treatment of Cervical Spondylotic Myelopathy With Congenital Cervical Stenosis.

Cervical spondylotic myelopathy (CSM) is a very common and devastating spinal disease. Congenital cervical stenosis (CCS) is the most common cause. We aimed to elucidate the security, effectivity, and feasibility of surgery combining laminoplasty with artificial disc replacement (ADR) to treat CSM patients with radiculopathy, especially for preserving the range of motion (ROM) of the cervical spine. Between August 2008 and April 2019, 39 patients with multiple CSM caused by CCS were enrolled in the present study. All patients received laminoplasty first and then ADR. We used a retrospective collection of data for evaluating the functional and radiologic outcomes, especially regarding preservation of ROM. Each patient underwent at least a 2-year postoperative follow-up. The Japanese Orthopedic Association score showed great improvements at 6 months. The ADR index-level ROM was preserved during follow-up. The subaxial Cobb angle could also be retained in the whole cervical spine, and the spinal canal diameter could be expanded by more than 52.6%. There were no severe complications or side effects, and no patients needed secondary surgery. We aimed to treat multiple levels of CSM with adequate decompression without too many intervertebral disc replacements. We were able to expand the spinal canal directly for these patients with CCS and needed only 1- or 2-level ADR to treat them with associated radiculopathy. This combined surgical strategy was secure, effective, and was able to preserve the ROM of the cervical spine.

Warp-knitted fabric structures for a novel biomimetic artificial intervertebral disc for the cervical spine

As an attempt to better replicate the complex kinematics of a natural disc, a novel biomimetic artificial intervertebral disc replacement (bioAID) has been developed containing a swelling hydrogel core as nucleus pulposus, a fiber jacket as annulus fibrosus and metal endplates to connect the device to the adjacent vertebrae. The first prototype consisted of a weft-knitted fiber jacket, in which only a single fiber was used to create the jacket structure. This can endanger the structural integrity of the complete device upon yarn damage. Therefore, in this study, several warp-knitted textile structures were assessed to (1) ensure structural integrity, (2) while allowing for swelling constraint of the hydrogel and (3) behaving as one integrated unit similar to the natural IVD. Moreover, the fiber jacket should (4) act as a scaffold that allows bone ingrowth to ensure long-term stability and (5) have a good durability, (6) be wear resistant and (7) have good manufacturing feasibility with good quality control. In this study, 4 different stitch patterns, including 2 × 1 and 1 × 1 lapping with and without a pillar stitch, were produced. The effect of the stitch pattern and stitch density on the fabric mechanical properties and device swelling and compressive strength was assessed. As a next step, the effect of using multiple layers of fabrics, mimicking the layered structure of annulus fibrosus, on the functional capacity of the bioAID was characterized. All textile structures were capable of limiting the swelling of the hydrogel while withstanding its internal pressure and showing sufficient wear resistance. However, only the 2 × 1 and 2 × 1 with pillar stitch had a pore size range that was suitable for cell infiltration to facilitate osseointegration as well as having the highest strength of the complete device to ensure safety under compression loading. Incorporating different number of jacket layers of these two stitch patterns did not show any significant effect. When also taking the structural parameters into consideration, the 2 × 1 lapping design with 4 layers was able to constrain hydrogel swelling, provide a high compressive strength, could facilitate cell infiltration and had dimensions within the range of a natural intervertebral disc.

Textile Design of an Intervertebral Disc Replacement Device from Silk Yarn

Low back pain is often due to degeneration of the intervertebral discs (IVD). It is one of the most common age- and work-related problems in today's society. Current treatments are not able to efficiently restore the full function of the IVD. Therefore, the aim of the present work was to reconstruct the two parts of the intervertebral disc-the annulus fibrosus (AF) and the nucleus pulposus (NP)-in such a way that the natural structural features were mimicked by a textile design. Silk was selected as the biomaterial for realization of a textile IVD because of its cytocompatibility, biodegradability, high strength, stiffness, and toughness, both in tension and compression. Therefore, an embroidered structure made of silk yarn was developed that reproduces the alternating fiber structure of +30° and -30° fiber orientation found in the AF and mimics its lamellar structure. The developed embroidered ribbons showed a tensile strength that corresponded to that of the natural AF. Fiber additive manufacturing with 1 mm silk staple fibers was used to replicate the fiber network of the NP and generate an open porous textile 3D structure that may serve as a reinforcement structure for the gel-like NP.

Mechanical characterization of a novel biomimetic artificial disc for the cervical spine

A novel biomimetic artificial intervertebral disc (bioAID) replacement implant has been developed containing a swelling hydrogel representing the nucleus pulposus, a tensile strong fiber jacket as annulus fibrosus and titanium endplates with pins to primarily secure the device between the vertebral bodies. In this study, the design safety of this novel implant was evaluated based on several biomechanical parameters, namely compressive strength, shear-compressive strength, risk of subsidence and device expulsion as well as identifying the diurnal creep-recovery characteristics of the device.The bioAID remained intact up to 1 kN under static axial compression and only 0.4 mm of translation was observed under a compressive shear load of 20 N. No subsidence was observed after 0.5 million cycles of sinusoidal compressive loading between 50 and 225 N. After applying 400 N in antero-posterior direction under 100 N axial compressive preload, approximately 2 mm displacement was found, being within the range of displacements reported for other commercially available cervical disc replacement devices. The diurnal creep recovery behavior of the bioAID closely resembled what has been reported for natural intervertebral discs in literature.Overall, these results indicate that the current design can withstand (shear-compression loads and is able to remain fixed in a mechanical design resembling the vertebral bodies. Moreover, it is one of the first implants that can closely mimic the poroelastic and viscoelastic behavior of natural disc under a diurnal loading pattern.

A Tunable Calcium Phosphate Coating to Drive in vivo Osseointegration of Composite Engineered Tissues

Varying degrees of hydroxyapatite (HA) surface functionalization have been implicated as the primary driver of differential osteogenesis observed in infiltrating cells. The ability to reliably create spatially controlled areas of mineralization in composite engineered tissues is of growing interest in the field, and the use of HA-functionalized biomaterials may provide a robust solution to this challenge. In this study, we successfully fabricated polycaprolactone salt-leached scaffolds with two levels of a biomimetic calcium phosphate coating to examine their effects on MSC osteogenesis. Longer duration coating in simulated body fluid (SBF) led to increased HA crystal nucleation within scaffold interiors as well as more robust HA crystal formation on scaffold surfaces. Ultimately, the increased surface stiffness of scaffolds coated in SBF for 7 days in comparison to scaffolds coated in SBF for 1 day led to more robust osteogenesis of MSCs in vitro without the assistance of osteogenic signaling molecules. This study also demonstrated that the use of SBF-based HA coatings can promote higher levels of osteogenesis in vivo. Finally, when incorporated as the endplate region of a larger tissue-engineered intervertebral disc replacement, HA coating did not induce mineralization in or promote cell migration out of neighboring biomaterials. Overall, these results verified tunable biomimetic HA coatings as a promising biomaterial modification to promote discrete regions of mineralization within composite engineered tissues.

A Finite Element Based Comparative Study of Lumbosacral Pedicle Screw Fixation and Artificial Disc Replacement

AbstractThe aim of this is to evaluate the biomechanical performance of double-level semirigid pedicle screw fixation and artificial intervertebral disc replacement in lumbar spine. Ti6Al4V and CFR-PEEK material are used for pedicle screw fixation and artificial disc replacement. In the present study, pedicle screw fixation and artificial intervertebral disc replacement are carried out between L3-L4-L5 regions under the application of moment 6,8,10 Nm and range of motion is compared during flexion, extension, and right-left lateral bending. Two-level pedicle screw fusion and total disc replacement are developed in the L3-L4-L5 of the lumber spine vertebrae. Carbon fiber reinforced (CFR-PEEK) and ultra-high molecular weight polyethylene (UHMWPE) are considered for the spinal fusion and the core part of the artificial disc respectively. Afterwards, applying the finite element analysis, it is detected that CFR-PEEK rod is able to increase range of motion at the implanted level in comparison to Ti6Al4V rod for both flexion–extension and lateral bending. In case of artificial intervertebral disc replacement hypermobility was observed. Hence, it is significant that rod material with CFR-PEEK is a better alternative for the treatment of degenerative diseases.

A biomechanical finite element study to assess the suitability of implantation on lumbar vertebrae L4-L5

Instability in the spinal section along with the cases of degeneration is commonly cured by the pedicle screw fixation system. The present work aims at the identification of suitable instrumentation at the spinal segment L4-L5 through finite element method and compared with an intact spine. Vertebral section (L3- Coccyx) upper surface L3 were subjected to various axial compressive forces for the body weights of 17, 67, 100 and 167 kg under the different physiological motion conditions such as rotation, flexion, extension and bending. Considering Intact as 100% the calculated results of equivalent stress on IVD-L34, L45 and L5S are as 90%, 43% and 76% during flexion, for extension 118%, 26% and 108%, during bending 58%, 58% and 80% and during rotation 57%, 46%, 74% respectively are the lowest for 6 mm instrumentation as compared to other instrumentation model. It was also observed that the load on the cortical and annulus region were highest as compared to the cancellous and nucleus region. The results of the present study can contribute to explaining fracture and intervertebral disc replacement cases subjected to pedicle screw implantation.

Comparative analysis of clinical efficacy between posterior percutaneous endoscopic discectomy and anterior cervical discectomy and fusion in the treatment of cervical spondylotic radiculopathy

To explore the clinical efficacy of posterior percutaneous endoscopic discectomy(PPECD) in the treatment of cervical spondylotic radiculopathy. A total of 56 patiens with single segment cervical spondylotic radiculopathy from December 2017 to October 2020, were randomly divided into observation group and control group. In observation group, there were 16 males and 11 females, including 8 cases of C4,5, 13 cases of C5,6 and 6 cases of C6,7 performed posterior percutaneous endoscopic discectomy, aged from 34 to 61 years old with an average of (51.15±6.29) years old. In control group, there were 19 males and 10 females with single segment cervical spondylotic radiculopathy including 10 cases of C4,5, 14 cases of C5,6 and 5 cases of C6,7 performed anterior cervical discectomy and fusion, aged from 40 to 65 years old with an average of (53.24±5.31) years old. The operative time, intraoperative blood loss, postoperative time of lying in bed and length of postoperative hospital stay were recorded. Visual analogue scale(VAS) and neck disability index(NDI) were used to evaluate the clinical efficacy. Cervical plain films or MRIs, CTs were taken for re-visiting patients. All patients were followed up more than 2 years. The observation group patients were followed up, the duration ranged from 24 to 42 months with an average of (30.48±4.91) months. The control group patients were followed up, the duration ranged from 25 to 47 months, with an average of (32.76±4.53) months. Compared with control group, operative time, intraoperative blood loss, postoperative time of lying in bed and length of postoperative hospital stay were decreased(P<0.05). Compared with pre-operation, VAS of neck and upper limb and NDI at the latest follow-up between two groups were significantly improved(P<0.05). Compared with control group, VAS of neck and upper limb at 1 day after operation in observation group were significantly reduced(P<0.05). There was no significant difference in VAS of neck and upper limb and NID at 1, 3 months and the latest follow-up after operation between two groups(P>0.05). In the observation group, one patient's deltoid muscle strength was weakened to grade 4 after operation, and returned to normal after 12 weeks of conservative treatment. In control group, there was 1 case of postoperative adjacent spondylosis with symptoms of spinal compression after 2 years operation, then underwent cervical artificial intervertebral disc replacement. And there was 1 case of dysphagia after operation in control group and improved after 1 year. There was no significant difference in incidence of complications between two groups. PPECD has advantages of shortening operative time, decreasing intraoperative blood loss, reducing postoperative time of lying in bed and length of postoperative hospital stay. However, applicable age range of patients and long-term clinical efficacy needs further study.

An in vitro comparison of three nucleus pulposus removal techniques for partial intervertebral disc replacement: An ultra-high resolution MRI study.

Nuclectomy, also known as nucleotomy, is a percutaneous surgical procedure performed to remove nucleus material from the center of the disc. Multiple techniques have been considered to perform a nuclectomy, however, the advantages and disadvantages of each are not well understood. This in vitro biomechanical investigation on human cadaveric specimens aimed to quantitatively compare three nuclectomy techniques performed using an automated shaver, rongeurs, and laser. Comparisons were made in terms of mass, volume and location of material removal, changes in disc height, and stiffness. Fifteen vertebra-disc-vertebra lumbar specimens were acquired from six donors (40 ± 13 years) and split into three groups. Before and after nucleotomy axial mechanical tests were performed and T2-weighted 9.4T MRIs were acquired for each specimen. When using the automated shaver and rongeurs similar volumes of disc material were removed (2.51 ± 1.10% and 2.76 ± 1.39% of the total disc volume, respectively), while considerably less material was removed using the laser (0.12 ± 0.07%). Nuclectomy using the automated shaver and rongeurs significantly reduced the toe-region stiffness (p = 0.036), while the reduction in the linear region stiffness was significant only for the rongeurs group (p = 0.011). Post-nuclectomy, 60% of the rongeurs group specimens showed changes in the endplate profile while 40% from the laser group showed subchondral marrow changes. From the MRIs, homogeneous cavities were seen in the center of the disc when using the automated shaver. When using rongeurs, material was removed non-homogeneously both from the nucleus and annulus regions. Laser ablation formed small and localized cavities suggesting that the technique is not suitable to remove large volumes of material unless it is developed and optimized for this application. The results demonstrate that both rongeurs and automated shavers can be used to remove large volumes of NP material but the reduced risk of collateral damage to surrounding tissues suggests that the automated shaver may be more suitable.

Graded-Three-Dimensional Cell-Encapsulating Hydrogel as a Potential Biologic Scaffold for Disc Tissue Engineering.

Intervertebral disk (IVD) degeneration, which can cause lower back pain, is a major predisposing factor for disability and can be managed through multiple approaches. However, there is no satisfactory strategy currently available to reconstruct and recover the natural properties of IVDs after degeneration. As tissue engineering develops, scaffolds with embedded cell cultures have proved critical for the successful regeneration of IVDs. In this study, an integrated scaffold for IVD replacement was developed. Through scanning electron microscopy and other mechanical measurements, we characterized the physical properties of different hydrogels. In addition, we simulated the physiological structure of natural IVDs. Nucleus pulposus (NP) cells and annulus fibrosus-derived stem cells (AFSCs) were seeded in gelatin methacrylate (GelMA) hydrogel at different concentrations to evaluate cell viability and matrix expression. It was found that different concentrations of GelMA hydrogel can provide a suitable environment for cell survival. However, hydrogels with different mechanical properties influence cell adhesion and extracellular matrix component type I collagen, type II collagen, and aggrecan expression. This tissue-engineered IVD implant had a similar structure and function as the native IVD, with the inner area mimicking the NP tissue and the outer area mimicking the stratified annulus fibrosus tissue. The new integrated scaffold demonstrated a good simulation of disc structure. The preparation of efficient and regeneration-promoting tissue-engineered scaffolds is an important issue that needs to be explored in the future. It is hoped that this work will provide new ideas and methods for the further construction of functional tissue replacement discs.

Multifunctional Nanofibrous Scaffolds with Angle-Ply Microstructure and Co-Delivery Capacity Promote Partial Repair and Total Replacement of Intervertebral Disc.

There is an urgent clinical need for the treatment of annulus fibrosus (AF) impairment caused by intervertebral disc (IVD) degeneration or surgical injury. Although repairing injured AF through tissue engineering is promising, the approach is limited by the complicated angle-ply microstructure, inflammatory microenvironment, poor self-repairing ability of AF cells and deficient matrix production. In this study, electrospinning technology is used to construct aligned core-shell nanofibrous scaffolds loaded with transforming growth factor-β3 (TGFβ3) and ibuprofen (IBU), respectively. The results confirm that the rapid IBU release improves the inflammatory microenvironment, while sustained TGFβ3 release enhances nascent extracellular matrix (ECM) formation. Biomaterials for clinical applications must repair local AF defects during herniectomy and enable AF regeneration during disc replacement, so a box defect model and total IVD replacement model in rat tail are constructed. The dual-drug delivering electrospun scaffolds are assembled into angle-ply structure to form a highly biomimetic AF that is implanted into the box defect or used to replace the disc. In two animal models, it is found that biomimetic scaffolds with good anti-inflammatory ability enhance ECM formation and maintain the mechanical properties of IVD. Findings from this study demonstrate that the multifunctional nanofibrous scaffolds provide inspirations for IVD repair.

A comparative finite element analysis of artificial intervertebral disc replacement and pedicle screw fixation of the lumbar spine

Titanium alloy-based Pedicle screw-rod fusion is a very common technique to provide higher fusion regularity than other methods. In recent times, Carbon-fibre-reinforced (CFR)-PEEK rod is used to better reduce the fusion rate. Alternatively, total disc replacement (TDR) is also very common for the non-fusion treatment method for degenerative disc disease (DDD). This study aims to investigate flexibility (ROM), stability, stress condition in implant, implant adjacent bone of the implanted lumbar spine during different physiological movements and loading environments. The finite element (FE) intact model of the lumbar spine (L2-L5) with two-level pedicle screw-rod fusion at L3-L4-L5 and two-level artificial disc replacement was developed. CFR-PEEK was taken for rod for semi-rigid fusion. UHMWPE was taken as core part of the artificial disc. The FE models were simulated under 6, 8 and 10 Nm moments in left right lateral bending, flexion and extension movements. The total ROM was reduced for two-level pedicle screw fixation and increased for the artificial disc replacement model during flexion extension compared to the intact spine. The total ROM was reduced by around 54% and 25% for two-level fixation and increased by 30% and 19.5% for artificial disc replacement spine, under flexion-extension and left-right lateral bending respectively. For screw fixation, the ROM increased by 15% and 18% reduced by 4.5% and 14% for disc replacement at the adjacent segments for flexion-extension and left-right lateral bending.

Tissue Engineering of Human Intervertebral Disc: A Concise Review.

Intervertebral disc (IVD) represents a structure of crucial structural and functional importance for human spine. Pathology of IVD institutes a frequently encountered condition in current clinical practice. Degenerative disc disease (DDD), the principal clinical representative of IVD pathology, constitutes an increasingly diagnosed spinal disorder associated with substantial morbidity and mortality in recent years. Despite the considerable incidence and socioeconomic burden of DDD, existing treatment modalities including conservative and surgical methods have been demonstrated to provide a limited therapeutic effect, being not capable of interrupting or reversing natural progress of underlying disease. These limitations underline the requirement for development of novel, innovative, and more effective therapeutic strategies for DDD management. Within this literature framework, compromised IVD replacement with a viable IVD construct manufactured with tissue-engineering (TE) methods has been recommended as a promising therapeutic strategy for DDD. Existing preliminary preclinical data demonstrate that proper combination of cells from various sources, different scaffold materials, and appropriate signaling molecules renders manufacturing of whole-IVD tissue-engineered constructs a technically feasible process. The aim of this narrative review was to critically summarize current published evidence regarding particular aspects of IVD-TE, primarily emphasizing in providing researchers in this field with practicable knowledge to enhance clinical translatability of their research and informing clinical practitioners about the features and capabilities of innovative TE science in the field of IVD-TE. Impact Statement Human intervertebral disc (IVD) pathology represents an extremely frequent condition in current clinical practice. Given the considerable limitations of available treatment options, deployment of novel and groundbreaking therapeutic modalities constitutes a rather urgent need. Tissue engineering of entire human IVD, a technically feasible process within laboratory framework, is theoretically capable of overcoming limitations that characterize currently applied therapeutic measures. Optimization of laboratory manufacturing techniques in conjunction with more diligent in vivo evaluation of tissue-engineered constructs are expected to lay the foundations for clinical trials initiation.