Graft Materials and Biologics for Spinal Interbody Fusion

Clinical Implementation of Tissue-Sparing Posterior Cervical Fusion: Addressing Market Access Challenges

Background: The traditional open midline posterior cervical spine fusion procedure has several shortcomings. It can cause soft tissue damage, muscle atrophy, compromise of the lateral masses and painful prominent posterior cervical instrumentation or spinous process if there is dehiscence of the fascia. Additionally, patients frequently experience the rapid development of adjacent segment disease, which can result in the reemergence of debilitating pain and functional impairment. Clinical relevance: Tissue-sparing posterior cervical fusion is an alternative method for treating patients with symptomatic cervical degenerative disc disease. However, widespread clinical adoption has been challenged by ambiguity, misunderstandings and misinterpretations regarding appropriate procedural reimbursement coding. Technological advancement: The tissue-sparing posterior cervical fusion procedure was approved by the US Food and Drug Administration (FDA) in 2018 (CORUS™ Spinal System and CAVUX® Facet Fixation System (CORUS/CAVUX); Providence™ Medical Technology). This technique addresses the concerns with traditional spine fusion methods by achieving the stability and outcomes of posterior cervical fusion without the morbidity associated with significant muscle stripping in the traditional approach. This technology uses specialized implants and instrumentation to perform all of the steps required to facilitate bone fusion and provide stability while minimizing tissue disruption. The technique involves extensive bone preparation for fusion and placement of specialized stabilization implants that span the facet joint, promoting natural bone growth and fusion while reducing the need for extensive exposure. This procedure provides an effective, less invasive solution for patients with cervical degenerative disc disease. Reimbursement and coding clarity: The article provides a comprehensive rationale for appropriate reimbursement coding for tissue-sparing posterior cervical fusion. This is a critical aspect for the adoption and accessibility of medical technologies. This information is crucial for practitioners and healthcare administrators, ensuring that innovative procedures are accurately coded and reimbursed. Procedural details and clinical evidence: By detailing the procedural steps, instruments used and the physiological basis for the procedure, this article serves as a valuable educational resource for spine surgeons and payers to appropriately code for this procedure. Conclusions: The description of work for CORUS/CAVUX is equivalent to the current surgical standard of lateral mass screw fixation with decortication and onlay posterior grafting to facilitate posterior fusion. Thus, it is recommended that CPT codes 22600/22840 be used, as they best reflect the surgical approach, instrumentation, decortication, posterior cervical fusion and bone grafting procedures.

3D-Printed Demineralized Bone Matrix-Based Conductive Scaffolds Combined with Electrical Stimulation for Bone Tissue Engineering Applications

Bone is remodeled through a dynamic process facilitated by biophysical cues that support cellular signaling. In healthy bone, signaling pathways are regulated by cells and the extracellular matrix and transmitted via electrical synapses. To this end, combining electrical stimulation (ES) with conductive scaffolding is a promising approach for repairing damaged bone tissue. Therefore, "smart" biomaterials that can provide multifunctionality and facilitate the transfer of electrical cues directly to cells have become increasingly more studied in bone tissue engineering. Herein, 3D-printed electrically conductive composite scaffolds consisting of demineralized bone matrix (DBM) and polycaprolactone (PCL), in combination with ES, for bone regeneration were evaluated for the first time. The conductive composite scaffolds were fabricated and characterized by evaluating mechanical, surface, and electrical properties. The DBM/PCL composites exhibited a higher compressive modulus (107.2 MPa) than that of pristine PCL (62.02 MPa), as well as improved surface properties (i.e., roughness). Scaffold electrical properties were also tuned, with sheet resistance values as low as 4.77 × 105 Ω/sq for our experimental coating of the highest dilution (i.e., 20%). Furthermore, the biocompatibility and osteogenic potential of the conductive composite scaffolds were tested using human mesenchymal stromal cells (hMSCs) both with and without exogenous ES (100 mV/mm for 5 min/day four times/week). In conjunction with ES, the osteogenic differentiation of hMSCs grown on conductive DBM/PCL composite scaffolds was significantly enhanced when compared to those cultured on PCL-only and nonconductive DBM/PCL control scaffolds, as determined through xylenol orange mineral staining and osteogenic protein analysis. Overall, these promising results suggest the potential of this approach for the development of biomimetic hybrid scaffolds for bone tissue engineering applications.

The Categorization of Perinatal Derivatives for Orthopedic Applications

Musculoskeletal (MSK) pathology encompasses an array of conditions that can cause anything from mild discomfort to permanent injury. Their prevalence and impact on disability have sparked interest in more effective treatments, particularly within orthopedics. As a result, the human placenta has come into focus within regenerative medicine as a perinatal derivative (PnD). These biologics are sourced from components of the placenta, each possessing a unique composition of collagens, proteins, and factors believed to aid in healing and regeneration. This review aims to explore the current literature on PnD biologics and their potential benefits for treating various MSK pathologies. We delve into different types of PnDs and their healing effects on muscles, tendons, bones, cartilage, ligaments, and nerves. Our discussions highlight the crucial role of immune modulation in the healing process for each condition. PnDs have been observed to influence the balance between anti- and pro-inflammatory factors and, in some cases, act as biologic scaffolds for tissue growth. Additionally, we assess the range of PnDs available, while also addressing gaps in our understanding, particularly regarding biologic processing methods. Although certain PnD biologics have varying levels of support in orthopedic literature, further clinical investigations are necessary to fully evaluate their impact on human patients.

Bioactive Moldable Click Chemistry Polymer Cement with Nano-Hydroxyapatite and Growth Factor-Enhanced Posterolateral Spinal Fusion in a Rabbit Model

Spinal injuries or diseases necessitate effective fusion solutions, and common clinical approaches involve autografts, allografts, and various bone matrix products, each with limitations. To address these challenges, we developed an innovative moldable click chemistry polymer cement that can be shaped by hand and self-cross-linked in situ for spinal fusion. This self-cross-linking cement, enabled by the bioorthogonal click reaction, excludes the need for toxic initiators or external energy sources. The bioactivity of the cement was promoted by incorporating nanohydroxyapatite and microspheres loaded with recombinant human bone morphogenetic protein-2 and vascular endothelial growth factor, fostering vascular induction and osteointegration. The release kinetics of growth factors, mechanical properties of the cement, and the ability of the scaffold to support in vitro cell proliferation and differentiation were evaluated. In a rabbit posterolateral spinal fusion model, the moldable cement exhibited remarkable induction of bone regeneration and effective bridging of spine vertebral bodies. This bioactive moldable click polymer cement therefore presents a promising biomaterial for spinal fusion augmentation, offering advantages in safety, ease of application, and enhanced bone regrowth.

Novel Approach to Difficult Spinal Reconstruction: Bilateral Simultaneous Rib and Iliac Crest Vascularized Bone Graft Spinoplastic Surgery

Pseudoarthrosis is a severe complication of spinal fusion surgery with occurrence rates as high as 35%-40%. Current options of revision surgery to correct pseudoarthrosis frequently carry high failure rates and risk of developing junctional kyphosis. Pedicled vascularized bone grafts (VBGs) are an innovative approach to boost spinal fusion rates via improving structural integrity and increasing the delivery of blood to the donor site. This versatile technique can be performed at different spinal levels without additional skin incisions and with minimal added operative time. Here we present the first bilateral rib and iliac crest VBG spinoplastic surgery performed to augment spinal fusion in a 68-year-old woman with distal junctional kyphosis and severe positive sagittal balance with low back and neck pain and significant difficulty standing upright. The patient had history of multiple spinal operations with preoperative CT imaging demonstrating loosening and pull out of L3 and fracture of L2 screws. She underwent two-stage surgical treatment involving anterior lumbar interbody fusion L3-S1 followed by removal of hardware, T4 to pelvis fusion with L2-3 prone lateral interbody fusion, and T11-S1 posterior column osteotomies. The surgery was augmented by bilateral rib and iliac crest VBGs performed by plastic surgery. At three-month follow-up the patient demonstrated functional improvement, being able to maintain upright posture and walk; was satisfied with the result of the surgery; and demonstrated no graft-related complications. In conclusion, utilization of pedicled VBGs is a novel, promising approach to augment spinal surgery in high risk patients.

Budget Impact Analysis of Minimally Invasive versus Open Transforaminal Lumbar Interbody Fusion for Lumbar Degenerative Disease: A European Hospital Perspective

Purpose

When traditional therapies fail to provide relief from debilitating lower back pain, surgeries such as transforaminal lumbar interbody fusion (TLIF) may be required. This budget impact analysis (BIA) compared minimally-invasive (MI)-TLIF versus open (O)-TLIF for single-level fusion from an Italian hospital perspective.

Methods

The BIA compared costs of 100 MI-TLIF and 100 O-TLIF procedures from an Italian hospital perspective over a one-year time horizon. The base case included costs for length of hospital stay (LOS), blood loss, and sterilizing surgical trays. The scenario analysis also included operating room (OR) time and complication costs. Base case inputs were from the Miller et al meta-analysis; scenario analysis inputs were from the Hammad et al meta-analysis. The device costs for MI-TLIF and O-TLIF procedures were from Italian tender prices for Viper Prime™ System and Expedium™ Spine System, respectively.

Results

Base case deterministic analysis results showed cost savings of €207,370 for MI-TLIF compared with O-TLIF. MI-TLIF costs were lower for LOS (€215,277), transfusion for blood loss (€16,881), and surgical tray sterilization (€28,232), whereas device costs were lower for O-TLIF (€53,020). The probabilistic result was similar, with MI-TLIF resulting in savings of €211,026 (95% credible interval [CR]: €208,725 - €213,327). All 1000 base case probabilistic sensitivity analysis runs were cost saving. Deterministic scenario analysis results showed cost savings of €166,719 for MI-TLIF. MI-TLIF costs were lower for LOS (€190,813), transfusion for blood loss (€16,881), surgical tray sterilization (€28,232), and complications (€2076), whereas O-TLIF costs were lower for OR time (€18,263) and devices used (€53,020).

Conclusion

Despite the increase incremental cost for medical device innovation and OR time, this study demonstrates the economic savings of MI-TLIF compared to O-TLIF from a European hospital perspective. The findings will be useful to policy and hospital decision makers in assessing purchasing, funding and reimbursement decisions.

Bone Grafting Options for Single-Level TLIF: So Many Options, What Is the Evidence?

BACKGROUND

This review seeks to investigate the clinically relevant bone graft materials in single-level transforaminal lumbar interbody fusion (TLIF) procedures as defined by (1) primary outcomes (ie, fusion rates and complication rates) and (2) patient-reported outcomes (ie, visual analog scale [VAS] and Oswestry disability index [ODI]). Because of the advantages in stimulating bone growth, autologous bone grafts such as the iliac crest bone graft (ICBG) have been the gold standard. Numerous alternatives to ICBG have been introduced. Understanding the risks and benefits of bone graft options is vital to optimizing patient care.

METHODS

A PubMed search was performed for all clinical studies published between January 2008 and March 2023 that referenced the single-level TLIF procedure as well as one of the following grafts: autograft, allograft, bone morphogenetic protein (BMP), demineralized bone matrix, or mesenchymal stem cells (MSCs). Case studies and reports were excluded.

RESULTS

Twenty-eight studies met the inclusion criteria. Studies from the PubMed search demonstrated similarly high fusion rates across nearly all graft materials, the lone exception being MSCs, which showed lower fusion rates. ICBG grafts experienced higher rates of postoperative graft site pain. The BMP graft material had high rates of radiculitis, heterogeneous ossification, and vertebral osteolysis. Patients saw an overall improvement in VAS and ODI scores with all graft materials.

CONCLUSION

Local autografts and ICBG have been the most studied. Fusion rates during single-level TLIF were similar across all graft materials except MSCs. Patient-reported pain levels improved after TLIF surgery regardless of the type of grafts used. While BMP implants have shown promising benefits, they have introduced a new array of complications not normally seen in ICBG implants. The study is limited by the lack of evidence of certain graft materials as well as nonuniformity in metrics evaluating the efficacy of graft materials.

Osteobiologies for Spinal Fusion from Biological Mechanisms to Clinical Applications: A Narrative Review

Degenerative lumbar spinal disease (DLSD), including spondylolisthesis and spinal stenosis, is increasing due to the aging population. Along with the disease severity, lumbar interbody fusion (LIF) is a mainstay of surgical treatment through decompression, the restoration of intervertebral heights, and the stabilization of motion segments. Currently, pseudoarthrosis after LIF is an important and unsolved issue, which is closely related to osteobiologies. Of the many signaling pathways, the bone morphogenetic protein (BMP) signaling pathway contributes to osteoblast differentiation, which is generally regulated by SMAD proteins as common in the TGF-β superfamily. BMP-2 and -4 are also inter-connected with Wnt/β-catenin, Notch, and FGF signaling pathways. With the potent potential for osteoinduction in BMP-2 and -4, the combination of allogenous bone and recombinant human BMPs (rhBMPs) is currently an ideal fusion material, which has equalized or improved fusion rates compared to traditional materials. However, safety issues in the dosage of BMP remain, so overcoming current limitations will provide significant advancement in spine surgery. In the future, translational research and the application of clinical study will be important to overcome the current limitations of spinal surgery.

Advances and Evolving Challenges in Spinal Deformity Surgery

BACKGROUND

Surgical intervention is a critical tool to address adult spinal deformity (ASD). Given the evolution of spinal surgical techniques, we sought to characterize developments in ASD correction and barriers impacting clinical outcomes.

METHODS

We conducted a literature review utilizing PubMed, Embase, Web of Science, and Google Scholar to examine advances in ASD surgical correction and ongoing challenges from patient and clinician perspectives. ASD procedures were examined across pre-, intra-, and post-operative phases.

RESULTS

Several factors influence the effectiveness of ASD correction. Standardized radiographic parameters and three-dimensional modeling have been used to guide operative planning. Complex minimally invasive procedures, targeted corrections, and staged procedures can tailor surgical approaches while minimizing operative time. Further, improvements in osteotomy technique, intraoperative navigation, and enhanced hardware have increased patient safety. However, challenges remain. Variability in patient selection and deformity undercorrection have resulted in heterogenous clinical responses. Surgical complications, including blood loss, infection, hardware failure, proximal junction kyphosis/failure, and pseudarthroses, pose barriers. Although minimally invasive approaches are being utilized more often, clinical validation is needed.

CONCLUSIONS

The growing prevalence of ASD requires surgical solutions that can lead to sustained symptom resolution. Leveraging computational and imaging advances will be necessary as we seek to provide comprehensive treatment plans for patients.

Novelties for increased safety in cranio-vertebral surgery: a review

The cranio-vertebral junction (CVJ) was formerly considered a surgical "no man's land" due to its complex anatomical and biomechanical features. Surgical approaches and hardware instrumentation have had to be tailored in order to achieve successful outcomes. Nowadays, thanks to the ongoing development of new technologies and surgical techniques, CVJ surgery has come to be widely performed in many spine centers. Accordingly, there is a drive to explore novel solutions and technological nuances that make CVJ surgery safer, faster, and more precise. Improved outcome in CVJ surgery has been achieved thanks to increased safety allowing for reduction in complication rates. The Authors present the latest technological advancements in CVJ surgery in terms of imaging, biomaterials, navigation, robotics, customized implants, 3D-printed technology, video-assisted approaches and neuromonitoring.

Six-Year Follow-up of a Randomized Controlled Trial of i-FACTOR Peptide-Enhanced Bone Graft Versus Local Autograft in Single-Level Anterior Cervical Discectomy and Fusion

BACKGROUND

Previous analyses of the US Food and Drug Administration (FDA) Investigational Device Exemption study demonstrated the superiority of i-FACTOR compared with local autograft bone in single-level anterior cervical discectomy and fusion (ACDF) at 12 and 24 months postoperatively in a composite end point of overall success.

OBJECTIVE

To report the final, 6-year clinical and radiological outcomes of the FDA postapproval study.

METHODS

Of the original 319 subjects enrolled in the Investigational Device Exemption study, 220 participated in the postapproval study (106 i-FACTOR and 114 control).

RESULTS

The study met statistical noninferiority success for all 4 coprimary end points. Radiographic fusion was achieved in 99% (103/104) and 98.2% (109/111) in i-FACTOR and local autograft subjects, mean Neck Disability Index improvement from baseline was 28.6 (24.8, 32.3) in the i-FACTOR and 29.2 (25.6, 32.9) in the control group, respectively (noninferiority P < .0001). The neurological success rate at 6 years was 95.9% (70/73) in i-FACTOR subjects and 93.7% (70/75) in local autograft subjects (noninferiority P < .0001). Safety outcomes were similar between the 2 groups. Secondary surgery on the same or different cervical levels occurred in 20/106 (18.9%) i-FACTOR subjects and 23/114 (20.2%) local autograft subjects ( P = .866). Secondary outcomes (pain, SF-36 physical component score and mental component score) in i-FACTOR subjects were similar to those in local autograft subjects.

CONCLUSION

i-FACTOR met all 4 FDA-mandated noninferiority success criteria and demonstrated safety and efficacy in single-level anterior cervical discectomy and fusion for cervical radiculopathy through 6 years postoperatively. Safety outcomes are acceptable, and the clinical and functional outcomes observed at 12 and 24 months remained at 72 months.

Biomimetic Remineralized Three-Dimensional Collagen Bone Matrices with an Enhanced Osteostimulating Effect

Bone grafts with a high potential for osseointegration, capable of providing a complete and effective regeneration of bone tissue, remain an urgent and unresolved issue. The presented work proposes an approach to develop composite biomimetic bone material for reconstructive surgery by deposition (remineralization) on the surface of high-purity, demineralized bone collagen matrix calcium phosphate layers. Histological and elemental analysis have shown reproduction of the bone tissue matrix architectonics, and a high-purity degree of the obtained collagen scaffolds; the cell culture and confocal microscopy have demonstrated a high biocompatibility of the materials obtained. Adsorption spectroscopy, scanning electron microscopy, microcomputed tomography (microCT) and infrared spectroscopy, and X-ray diffraction have proven the efficiency of the deposition of calcium phosphates on the surface of bone collagen scaffolds. Cell culture and confocal microscopy methods have shown high biocompatibility of both demineralized and remineralized bone matrices. In the model of heterotopic implantation in rats, at the term of seven weeks, an intensive intratrabecular infiltration of calcium phosphate precipitates, and a pronounced synthetic activity of osteoblast remodeling and rebuilding implanted materials, were revealed in remineralized bone collagen matrices in contrast to demineralized ones. Thus, remineralization of highly purified demineralized bone matrices significantly enhanced their osteostimulating ability. The data obtained are of interest for the creation of new highly effective osteoplastic materials for bone tissue regeneration and augmentation.

The safe and effective use of supercritical CO2-processed bone allografts for cervical and lumbar interbody fusion: A retrospective study

Introduction

The clinical efficacy and safety of supercritical CO₂-processed bone allografts prepared from living donors has yet to be confirmed in spinal surgery. Here we report our clinical and surgical experience of using supercritical CO₂-processed bone allografts for lumbar and cervical fusion.

Methods

Sixteen patients underwent one or two level anterior cervical discectomy and fusion and 37 patients underwent anterior retroperitoneal route lumbar fusion using bone allografts processed using supercritical CO₂ extraction combined with chemical viral inactivation. Fusion success was assessed radiographically in the immediate postoperative period and at one month, six months, one year, and three years postoperatively. Function and pain were assessed using visual analog scales, Odom's criteria, the neck disability index (NDI), and the Oswestry disability index (ODI).

Results

At a mean of 43 and 47 months postoperatively, 95.3% and 90.5% of cervical and lumbar fusion patients had radiographic evidence of bone fusion, respectively. Over 80% of patients reported good to excellent outcomes according to Odom's criteria, the perception of pain significantly decreased, and the mean NDI and ODI scores significantly improved at the last follow-up compared with before the operations. There were no safety concerns. For the cervical group, the mean NDI score improved from 26.3 ± 6.01 preoperatively to 15.00 ± 8.03 and 17.60 ± 13.95 at immediate post-op (p = 0.02) and last follow-up visits (p = 0.037) respectively. For the lumbar cases, the mean ODI score improved from 28.31 ± 6.48 preoperatively to 14.68 ± 5.49 (p < 0.0001) and 12.54 ± 10.21 (p < 00001) at immediate post-op and last follow-up visits respectively.

Conclusion

Within the limitations of this study, the use of supercritical CO₂-processed bone allografts resulted in satisfactory clinical outcomes and fusion rates with acceptable safety for both cervical and lumbar surgeries.

Experience With Recombinant Human Bone Morphogenetic Protein-2 in Posterior Lumbar Interbody Fusion: A Retrospective Review of 1019 Procedures

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with an activated collagen scaffold (Infuse; Medtronic, MN) has been used to facilitate lumbar intervertebral fusion; however, data regarding its efficacy are inconsistent. We aimed to assess the efficacy of rhBMP-2 when used in posterior lumbar interbody fusion (PLIF) by analyzing the rate of reoperation for nonunion and patient-reported outcome measures in a large retrospective case series. We also aimed to assess the impact of patient and surgical factors on rates of reoperation and determine frequency of complications.

METHODS

Prospectively collected data from a single-surgeon database of consecutive PLIFs (minimum 18-month follow-up) were retrospectively analyzed. PLIF was performed with pedicle screw instrumentation, intervertebral spacers, and locally harvested bone graft to which rhBMP-2 and bone marrow aspirate (BMA) were added. Multivariate logistic regression was used to determine the influence of patient and surgical factors on the primary outcome: reoperation for confirmed nonunion.

RESULTS

A total of 1019 operations at 1485 levels across 908 patients were analyzed. Mean duration of follow-up was 51.7 ± 30.0 months (range 18-172). Twelve patients required reoperation for nonunion (1.2%). Increasing body mass index was found to be significant in predicting reoperation (OR 1.114, P = 0.046). Postoperative radiculitis was common (42%) but transient in most cases. There were significant and sustained improvements in patient-reported outcome measures postoperatively. Four cases of osteolysis and 5 of epidural cyst were recorded, and a reduction of rhBMP-2 dose seemed to ameliorate these sequelae.

CONCLUSION

In this large retrospective observational study, PLIF performed with rhBMP-2 and BMA resulted in a low rate of clinically significant nonunion and significant improvement in patient-reported outcomes. Transient radiculitis was common. Osteolysis and epidural cyst formation were rare and possibly related to dosage.

CLINICAL RELEVANCE

rhBMP-2 is effective when used in PLIF, resulting in a high rate of fusion and improved patient outcomes, and it has an acceptable safety profile.

LEVEL OF EVIDENCE: 3

Outstanding in vivo mechanical integrity of additively manufactured spinal cages with a novel "honeycomb tree structure" design via guiding bone matrix orientation

BACKGROUND CONTEXT

Therapeutic devices for spinal disorders, such as spinal fusion cages, must be able to facilitate the maintenance and rapid recovery of spinal function. Therefore, it would be advantageous that future spinal fusion cages facilitate rapid recovery of spinal function without secondary surgery to harvest autologous bone.

PURPOSE

This study investigated a novel spinal cage configuration that achieves in vivo mechanical integrity as a devise/bone complex by inducing bone that mimicked the sound trabecular bone, hierarchically and anisotropically structured trabeculae strengthened with a preferentially oriented extracellular matrix.

STUDY DESIGN/SETTINGS

In vivo animal study.

METHODS

A cage possessing an anisotropic through-pore with a grooved substrate, that we termed "honeycomb tree structure," was designed for guiding bone matrix orientation; it was manufactured using a laser beam powder bed fusion method through an additive manufacturing processes. The newly designed cages were implanted into sheep vertebral bodies for 8 and 16 weeks. An autologous bone was not installed in the newly designed cage. A pull-out test was performed to evaluate the mechanical integrity of the cage/bone interface. Additionally, the preferential orientation of bone matrix consisting of collagen and apatite was determined.

RESULTS

The cage/host bone interface strength assessed by the maximum pull-out load for the novel cage without an autologous bone graft (3360±411 N) was significantly higher than that for the conventional cage using autologous bone (903±188 N) after only 8 weeks post-implantation.

CONCLUSIONS

These results highlight the potential of this novel cage to achieve functional fusion between the cage and host bone. Our study provides insight into the design of highly functional spinal devices based on the anisotropic nature of bone.

CLINICAL SIGNIFICANCE

The sheep spine is similar to the human spine in its stress condition and trabecular bone architecture and is widely recognized as a useful model for the human spine. The present design may be useful as a new spinal device for humans.

Adult Isthmic Spondylolisthesis: A Radiographic and Outcomes Analysis Comparing Circumferential Fusions Versus TLIF Procedures

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

The objective of this study was to compare radiographic and patient-reported outcome measures (PROMs) between circumferential fusions and transforaminal lumbar interbody fusion (TLIF) for adult isthmic spondylolisthesis (IS).

SUMMARY OF BACKGROUND DATA

Definitive management of adult IS typically requires decompression and fusion. Multiple fusion techniques have been described, but literature is sparse in identifying the optimal technique.

METHODS

Patients with IS undergoing single-level or 2-level circumferential fusion or TLIF with a minimum 1-year follow-up were included. Patient demographics, surgical characteristics, and PROMs were extracted from patients' electronic medical records. Descriptive statistics and multivariate regression analysis compared outcomes with significance set at P -value <0.05.

RESULTS

A total of 78 circumferential fusions (48 open decompression and fusions and 30 circumferential fusions utilizing posterior percutaneous instrumentation) and 50 TLIF procedures were included. Length of stay was significantly longer when comparing circumferential procedures (3.56±0.96 d) versus TLIFs (2.88±1.14 d) ( P =0.002). The circumferential fusion group resulted in greater postoperative improvement in segmental lordosis [anterior/posterior (A/P): 6.45, TLIF: -1.99, P <0.001], posterior disk height (A/P: 12.6 mm, TLIF: 8.9 mm, P <0.001), and ∆disk height (A/P: 7.7 mm, TLIF: 3.6 mm, P <0.001). Both groups significantly improved in all PROMs ( P <0.001). While the circumferential fusion group had a significantly higher rate of perioperative surgical complications (12.82% vs. 2.00%, P =0.049), there was no difference in the rate of 30-day readmissions ( P =0.520) or revision surgeries between techniques ( P =0.057).

CONCLUSIONS

Circumferential fusions are associated with improvements in radiographic outcomes compared with TLIFs, but this is at the expense of longer hospital length of stay and increased risk for perioperative complications. The surgical technique did not result in superior postoperative PROMs or differences in readmissions or revisions.

Bovine-derived xenograft is a viable bone graft substitute in multilevel, instrumented, spinal fusion

Objective

To evaluate radiological outcomes following the use of xenogeneic bone graft substitute (BGS) in patients undergoing multisegmental spinal fusion.

Summery of Background Data

Data exists for single level and short segment fusions, there presently is a paucity of data on fusion rate after bone augmentation with BGS in multisegmental posterior spinal fusion (PSF). The leading concern is pseudarthrosis, which often leads to a loss of correction after PSF. Therefore, the bone graft is an essential aspect of PSF.

Methods

We retrospectively analysed the radiological data of a consecutive cohort of patients who had been treated for adolescent idiopathic scoliosis (AIS) via multisegmental spinal fusion, in whom a bovine derived BGS had been used and had a complete dataset of 24 months follow-up. The Cobb angle of the main curve was measured pre-operatively and then at 6, 12 and 24 months post-operatively. Loosening of the screws was recorded at the same post-operative time points.

Results

After applying inclusion and exclusion criteria, 28 patients were included. We found no significant change of the cobb angle from the main curve as well as the cobb angle from the thoracic kyphosis during the 24 months of follow up. No patient showed a lack of bony fusion. There was 1 revision surgery, which was due to trauma.

Conclusion

In this cohort, all patients showed successful bone fusion during a 24-month follow-up. Additionally, there was no change in the Cobb angle during the 2-year post-operative period. Our data indicates that the use of bovine-derived BGS supports bone fusion after multisegmental posterior instrumented fusion of the spine.

Fusion Revision Surgery With Reamer-Irrigator-Aspirator to Harvest Autograft After Spinal Pseudarthrosis

Background and purpose

Spinal pseudarthrosis (SPA) is a common complication after attempted cervical or lumbosacral spinal fusion surgery. Revision surgeries usually necessitate bone graft implementation as an adjunct to hardware revision. Iliac crest bone graft is the gold standard but availability can be limited and usage often leads to persistent postoperative pain at the donor site. There is scant literature regarding the use of reamer-irrigator-aspirator (RIA)-harvested bone graft in lumbar spinal fusion. This is a collaborative study between orthopedic surgery and neurosurgery departments to utilize femur intramedullary autograft harvested using the RIA system as an adjunct graft in SPA revision surgeries.

Materials and methods

A retrospective review was conducted at a single center between August 2014 and December 2017 of patients aged ≥ 18 years and diagnosed with cervical, thoracic, or lumbar SPA who underwent revision fusion surgery using femur intramedullary autograft harvested using the RIA system. Plain radiographs and CT scans were utilized to confirm successful fusion.

Results

Eleven patients underwent 12 SPA revision surgeries using the RIA system as a source for bone graft in addition to bone morphogenetic protein 2 (BMP-2) and allograft. The mean amount of graft harvested was 51.3 mL (range: 20-70 mL). Nine patients achieved successful fusion (81.8%). The average time to fusion was 9.1 months. Four patients (36.4%) had postoperative knee pain. Regarding patient position and approach for harvesting, 66.7% (n = 8) of cases were positioned prone and a retrograde approach was utilized in 91.7% (n = 11) of cases.

Interpretation

This is the first case series in known literature to report the RIA system as a reliably considerable source of autologous bone graft for SPA revision surgeries. It provides a useful adjunct to the known types of bone grafts. Patient positioning and the approach choice for graft harvesting can be adjusted according to the fusion approach and the surgeon’s preference.

A systematic review and meta-analysis of fusion rate enhancements and bone graft options for spine surgery

Our study aimed to evaluate differences in outcomes of patients submitted to spinal fusion using different grafts measuring the effectiveness of spinal fusion rates, pseudarthrosis rates, and adverse events. Applying the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, this systematic review and meta-analysis identified 64 eligible articles. The main inclusion criteria were adult patients that were submitted to spinal fusion, autologous iliac crest (AIC), allograft (ALG), alloplastic (ALP; hydroxyapatite, rhBMP-2, rhBMP-7, or the association between them), and local bone (LB), whether in addition to metallic implants or not, was applied. We made a comparison among those groups to evaluate the presence of differences in outcomes, such as fusion rate, hospital stay, follow-up extension (6, 12, 24, and 48 months), pseudarthrosis rate, and adverse events. Sixty-four studies were identified. LB presented significantly higher proportions of fusion rates (95.3% CI 89.7–98.7) compared to the AIC (88.6% CI 84.8–91.9), ALG (87.8% CI 80.8–93.4), and ALP (85.8% CI 75.7–93.5) study groups. Pseudarthrosis presented at a significantly lower pooled proportion of ALG studies (4.8% CI 0.1–15.7) compared to AIC (8.6% CI 4.2–14.2), ALP (7.1% CI 0.9–18.2), and LB (10.3% CI 1.8–24.5). ALP and AIC studies described significantly more cases of adverse events (80 events/404 patients and 860 events/2001 patients, respectively) compared to LB (20 events/311 patients) and ALG (73 events/459 patients). Most studies presented high risk-of-bias scores. Based on fusion rates and adverse events proportions, LB showed a superior trend among the graft cases we analyzed. However, our review revealed highly heterogeneous data and a need for more rigorous studies to better address and assist surgeons’ choices of the best spinal grafts.

Is Platelet-Rich Plasma Effective in Enhancing Spinal Fusion? Systematic Overview of Overlapping Meta-Analyses

STUDY DESIGN

Systematic review.

OBJECTIVES

We performed this systematic overview on overlapping meta-analyses that analyzed the role of platelet-rich plasma(PRP) in enhancing spinal fusion and identify which study provides the current best evidence on the topic and generate recommendations for the same.

MATERIALS AND METHODS

We conducted independent and duplicate electronic database searches in PubMed, Web of Science, Embase, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects till October-2020 for meta-analyses that analyzed the role of PRP in spinal fusion procedures. Methodological quality assessment was made using Oxford Levels of Evidence, AMSTAR scoring, and AMSTAR 2 grades. We then utilized the Jadad decision algorithm to identify the study with highest quality to represent the current best evidence to generate recommendations.

RESULTS

3 meta-analyses fulfilling the eligibility criteria were included. The AMSTAR scores of included studies varied from 5-8(mean:6.3) and all included studies had critically low reliability in their summary of results due to their methodological flaws according to AMSTAR 2 grades. The current best evidence showed that utilization of PRP was not associated with significant improvement in patient-reported outcomes such as Visual Analog Score for pain compared to the standard fusion procedure. Moreover, PRP was found to be associated with lower fusion rates.

CONCLUSION

Based on this systematic overview, the effectiveness of PRP as a biological agent in augmenting spinal fusion is limited. Current evidence does not support the use of PRP as an adjuvant to enhance spinal fusion.

Early bone ingrowth and segmental stability of a trussed titanium cage versus a polyether ether ketone cage in an ovine lumbar interbody fusion model

BACKGROUND CONTEXT

Lumbar interbody fusion is an effective treatment for unstable spinal segments. However, the time needed to establish a solid bony interbody fusion between the two vertebrae may be longer than twelve months after surgery. During this time window, the instrumented spinal segment is assumed to be at increased risk for instability related complications such as cage migration or subsidence. It is hypothesized that the design of new interbody cages that enable direct osseointegration of the cage at the vertebral endplates, without requiring full bony fusion between the two vertebral endplates, might shorten the time window that the instrumented spinal segment is susceptible to failure.

PURPOSE

To quantify the bone ingrowth and resulting segmental stability during consolidation of lumbar interbody fusion using two different cage types.

STUDY DESIGN

Preclinical ovine model.

METHODS

Seven skeletally mature sheep underwent bi-segmental lumbar interbody fusion surgery with one conventional polyether ether ketone (PEEK) cage, and one newly developed trussed titanium (TT) cage. After a postoperative time period of 13 weeks, non-destructive range of motion testing, and histologic analysis was performed. Additionally, sample specific finite element (FE) analysis was performed to predict the stability of the interbody fusion region alone.

RESULTS

Physiological movement of complete spinal motion segments did not reveal significant differences between the segments operated with PEEK and TT cages. The onset of creeping substitution within the cage seemed to be sooner for PEEK cages, which led to significantly higher bone volume over total volume (BV/TV) compared with the TT cages. TT cages showed significantly more direct bone to implant contact (BIC). Although the mean stability of the interbody fusion region alone was not statistically different between the PEEK and TT cages, the variation within the cage types illustrated an all-or-nothing response for the PEEK cages while a more gradual increase in stability was found for the TT cages.

CONCLUSIONS

Spinal segments operated with conventional PEEK cages were not different from those operated with newly developed TT cages in terms of segmental stability but did show a different mechanism of bone ingrowth and attachment. Based on the differences in development of bony fusion, we hypothesize that TT cages might facilitate increased early segmental stability by direct osseointegration of the cage at the vertebral endplates without requiring complete bony bridging through the cage.

CLINICAL SIGNIFICANCE

Interbody cage type affects the consolidation process of spinal interbody fusion. Whether different consolidation processes of spinal interbody fusion result in clinically significant differences requires further investigation.

Reconstructing Nanohydroxyapatite Prosthesis Based on CT-Scanning Data and Its Application in Spinal Injury

This study investigated the nanohydroxyapatite (nHA) prosthesis application effect based on CT-scanning data in spinal injury. This study chose 26 spinal injury patients treated in our hospital from September 2017 to September 2018, who were randomly divided into two groups. nHA prosthesis based on CT-scanning data was implanted in the nHA group, whereas titanium mesh was implanted in the titanium mesh group. Consequently, osteoblasts were cultured to test the biological activity of nHA and titanium alloy. In cell tests, we found osteoblasts could better adhere to nHA, and proliferation and activity were higher when planted on nHA material. After surgical treatment, all patients' spinal symptoms (VAS score, JOA score, and Cobb angle) had improved and did not cause obvious inflammatory foreign body reactions. During a two-year follow-up, the fusion time and support settlement in the nHA group was lower, and the vertebral fusion rate and ASIA score were higher than those in the titanium mesh group. Thus, CT-scanning data could further improve the vertebral fusion rate in the nHA group. Consequentially, nHA prosthesis based on CT-scanning data is a better choice for spinal injury therapy.

Biomechanical Evaluation of a Novel S-Type, Dynamic Zero-Profile Cage Design for Anterior Cervical Discectomy and Fusion with Variations in Bone Graft Shape: A Finite Element Analysis

BACKGROUND

Variations in cage design, material, and graft shape can affect osteointegration and adjacent segment range of motion (ROM) and stress after anterior cervical discectomy and fusion (ACDF) surgery. This study aimed to evaluate the biomechanical properties of a novel dynamic cervical cage design in both titanium (Ti) and polyether ether ketone (PEEK) with variations in bone graft shape using a single level ACDF (FE) model.

METHODS

A 3-dimensional C3-C6 FE model was developed using computed tomography scan data from a healthy male subject. The novel S-shaped dynamic interbody fusion cage with a zero-profile fixation was inserted at the C4-C5 level with 4 different bone graft shapes (square, circular, rectangular, and elliptical). Changes in segmental ROM and maximum von Mises stresses at the fusion and adjacent segments were analyzed.

RESULTS

Both Ti and PEEK cages showed decreased ROM at the fusion and adjacent levels for all shapes of bone graft when compared with the intact spine model. The elliptical graft, for both Ti and PEEK cages, showed a lower percentage of reduction in segmental ROM at the fusion and adjacent levels (0%-5.6%) when compared with other graft shapes (0%-12%). Maximum stresses at the fusion level were lowest in Ti cage with elliptical graft (229.8-347.6 MPa) when compared with other shapes (241.2-476.2 MPa) in flexion, extension, and lateral bending. For the bone graft, maximum stresses were highest on the elliptical-shaped bone graft in flexion and extension in the Ti cage, and in flexion and lateral bending in the PEEK cage.

CONCLUSIONS

Both Ti and PEEK cages showed decreased ROM at the fusion and adjacent levels for all shapes of bone graft when compared with the intact spine model. In the Ti and PEEK dynamic cages, the elliptical shape bone graft showed decreased stress on the cage and increased stress on the bone graft. Further experimental and clinical studies are needed to confirm these encouraging biomechanical results of this novel dynamic, zero-profile fusion device with elliptical bone graft in ACDF surgery.

Allografts and Spinal Fusion

BACKGROUND

Back pain is a common chief complaint within the United States and is caused by a multitude of etiologies. There are many different treatment modalities for back pain, with a frequent option being spinal fusion procedures. The success of spinal fusion greatly depends on instrumentation, construct design, and bone grafts used in surgery. Bone allografts are important for both structural integrity and providing a scaffold for bone fusion to occur.

METHOD

Searches were performed using terms "allografts" and "bone" as well as product names in peer reviewed literature Pubmed, Google Scholar, FDA-510k approvals, and clinicaltrials.gov.

RESULTS

This study is a review of allografts and focuses on currently available products and their success in both animal and clinical studies.

CONCLUSION

Bone grafts used in surgery are generally categorized into 3 main types: autogenous (from patient's own body), allograft (from cadaveric or living donor), and synthetic. This paper focuses on allografts and provides an overview on the different subtypes with an emphasis on recent product development and uses in spinal fusion surgery.

Understanding the Future Prospects of Synergizing Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery with Ceramics and Regenerative Cellular Therapies

Transforaminal lumber interbody fusion (TLIF) is the last resort to address the lumber degenerative disorders such as spondylolisthesis, causing lower back pain. The current surgical intervention for these abnormalities includes open TLIF. However, in recent years, minimally invasive TLIF (MIS-TLIF) has gained a high momentum, as it could minimize the risk of infection, blood loss, and post-operative complications pertaining to fusion surgery. Further advancement in visualizing and guiding techniques along with grafting cage and materials are continuously improving the safety and efficacy of MIS-TLIF. These assistive techniques are also playing a crucial role to increase and improve the learning curve of surgeons. However, achieving an appropriate output through TLIF still remains a challenge, which might be synergized through 3D-printing and tissue engineering-based regenerative therapy. Owing to their differentiation potential, biomaterials such as stem/progenitor cells may contribute to restructuring lost or damaged tissues during MIS-TLIF, and this therapeutic efficacy could be further supplemented by platelet-derived biomaterials, leading to improved clinical outcomes. Thus, based on the above-mentioned strategies, we have comprehensively summarized recent developments in MIS-TLIF and its possible combinatorial regenerative therapies for rapid and long-term relief.

Lactoferrin-Anchored Tannylated Mesoporous Silica Nanomaterials for Enhanced Osteo-Differentiation Ability

In the present study, we created lactoferrin-anchored mesoporous silica nanomaterials with absorbed tannic acid (LF/TA-MSNs) and evaluated the effect of these LF/TA-MSNs on the in vitro osteo-differentiation ability of adipose-derived stem cells (ADSCs) by testing alkaline phosphatase (ALP) level, calcium accumulation, and expression of osteo-differentiation-specific genes, including osteocalcin (OCN) and osteopontin (OPN). Both bare MSNs and LF/TA-MSNs exhibited round nano-particle structures. The LF/TA-MSNs demonstrated prolonged LF release for up to 28 days. Treatment of ADSCs with LF (50 μg)/TA-MSNs resulted in markedly higher ALP level and calcium accumulation compared to treatment with LF (10 μg)/TA-MSNs or bare MSNs. Furthermore, LF (50 μg)/TA-MSNs remarkably increased mRNA levels of osteo-differentiation-specific genes, including OCN and OPN, compared to MSNs or LF (10 μg)/TA-MSNs. Together, these data suggest that the ability of LF/TA-MSNs to enhance osteo-differentiation of ADSCs make them a possible nanovehicle for bone healing and bone regeneration in patients with bone defect or disease.

Trends in lumbar spinal fusion-a literature review

Over the past several decades, there has been an upward trend in the total number of spinal fusion procedures worldwide. Advanced spinal fusion techniques with or without internal fixation, additional innovations in surgical approaches, innovative implants including a wide variety of interbody devices, and new alternatives in bone grafting materials are some reasons for the increasing number of spine fusion procedures. Moreover, the indications for spinal fusion have broadened over time. Initially developed for the treatment of instability and deformity due to tuberculosis, scoliosis, and traumatic injury, spinal fusion surgery has now a wide range of indications like spondylolisthesis, congenital or degenerative deformity, spinal tumors, and pseudarthrosis, with degenerative disorders as the most common indication. This review emphasizes current lumbar fusion techniques and their development in the past decades.

Use of Local Morselized Bone Autograft in Minimally Invasive Transforaminal Lumbar Interbody Fusion: Cost Analysis

OBJECTIVE

Few studies have investigated the financial influence of surgical site local morselized bone autograft (LMBA) on the overall cost of spinal arthrodesis procedures. The purpose of this study is to evaluate the potential savings from introducing LMBA in spinal fusion procedures compared with no LMBA use.

METHODS

Retrospectively, cost analysis was conducted on a single-center data collected from 266 patients who underwent minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) ranging from L1 through S1 during a period of approximately 4 years. Cost data were obtained from individual patient invoices from the distributor. Sensitivity analyses were also conducted for different costs of allograft and LMBA.

RESULTS

A total of 282 levels were grafted in 266 subjects. The total quantity of LMBA harvested was 2433.5 mL, and a total of 1610 mL of allograft (Trinity Elite, ORTHOFIX, Lewisville, Texas, USA) were used. The overall cost savings from introducing LMBA in MI-TLIF surgery were $1,094,931 over the 4-year period with mean direct cost saving of $4116.28 per patient based on reduction in allograft. Results for cost savings per patient were sensitive to different direct costs of allograft and LMBA. A >95% fusion rate was achieved based on dynamic radiographs evaluated by an independent radiologist.

CONCLUSIONS

LMBA is a cost-saving bone graft extender option in MI-TLIF procedures while achieving high fusion rates. The savings are mainly achieved by reducing the amount of allograft needed and subsequent reduction in the total bone graft costs. Further research needs to be performed regarding long-term economic benefit.

Hydroxyapatite as a biomaterial - a gift that keeps on giving

The synthetic analogue to biogenic apatite, hydroxyapatite (HA) has a number of physicochemical properties that make it an attractive candidate for diagnosis, treatment of disease and augmentation of biological tissues. Here we describe some of the recent studies on HA, which may provide bases for a number of new medical applications. The content of this review is divided to different medical application modes utilizing HA, including tissue engineering, medical implants, controlled drug delivery, gene therapies, cancer therapies and bioimaging. A number of advantages of HA over other biomaterials emerge from this discourse, including (i) biocompatibility, (ii) bioactivity, (iii) relatively simple synthesis protocols for the fabrication of nanoparticles with specific sizes and shapes, (iv) smart response to environmental stimuli, (v) facile functionalization and surface modification through noncovalent interactions, and (vi) the capacity for being simultaneously loaded with a wide range of therapeutic agents and switched to bioimaging modalities for uses in theranostics. A special section is dedicated to analysis of the safety of particulate HA as a component of parenterally administrable medications. It is concluded that despite the fact that many benefits come with the usage of HA, its deficiencies and potential side effects must be addressed before the translation to the clinical domain is pursued. Although HA has been known in the biomaterials world as the exemplar of safety, this safety proves to be the function of size, morphology, surface ligands and other structural and compositional parameters defining the particles. For this reason, each HA, especially when it comes in a novel structural form, must be treated anew from the safety research angle before being allowed to enter the clinical stage.