The minimally effective dose of bone morphogenetic protein in posterior lumbar interbody fusion: a systematic review and meta-analysis

Anterior Versus Posterior and Transforaminal Lumbar Interbody Fusion for Spondylolisthesis: A Comparison of Radiographic, Clinical, and Patient Reported Outcomes

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

Lumbar spinal fusion is an increasingly utilized surgery within the United States attributed to an aging population with an increasing prevalence of degenerative spinal disease. Primary approaches include anterior lumbar interbody fusion (ALIF) and posterior or transforaminal lumbar interbody fusion (PLIF/TLIF), for which indications are preference driven. This study's objectives were to compare the clinical, radiographic, and functional outcomes of approaches for lumbar spondylolisthesis.

METHODS

We conducted a retrospective chart review of 1156 (267 ALIF; 889 PLIF/TLIF) patients who underwent ALIF or PLIF/TLIF due to spondylolisthesis at the L4-5, L5-S1, or L4-S1 levels at a large tertiary referral center from 2010 through 2018. Univariate and multivariable linear and logistic regressions were used to compare outcomes including radiologic fusion, change in lumbar lordosis, postoperative complications, and pre- to postoperative changes in quality-of-life (QoL) variables.

RESULTS

Between propensity-weighted cohorts, multivariate regression showed markedly increased odds of radiographic fusion for the ALIF cohort (Odds Ratio [OR]: 2.50, 95% Confidence Interval [CI]: 1.51-4.15). ALIF patients had shorter lengths of stay and less blood loss. However, there was no difference in the odds of reoperation within 1 year or any complications. There was also no significant group difference in change in Cobb angle or in any of the QoL variables.

CONCLUSIONS

These results indicate that ALIF may have greater radiologic success of fusion. However, when controlling for confounders, there is no difference in clinical outcomes between the approaches. Further research should evaluate the long-term cost-effectiveness of the 2 procedures.

Efficacy and safety of recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with autologous bone for the treatment of long bone nonunion: A report of a prospective case series

INTRODUCTION

Recombinant human Bone morphogenetic proteins have been used for the treatment of nonunions with promising results. We have been investigating both experimentally and clinically the efficacy of the rhBMP-2 with the macro / micro-porous hydroxyapatite carrier granules on the potency on the reconstruction of long bone defect. The purpose of this study was to prospectively evaluate the efficacy and safety of this specific rhBMP-2 with HA carrier granules mixed with autologous cancellous bone in patients with nonunion and bone defect resulted from the fracture related infection.

MATERIALS AND METHODS

This was a retrospective review of a prospective cohort at a university hospital. Patients diagnosed with nonunion under the definition of the United States Food and Drug Administration with bone defect after long bone fractures were enrolled from January 2020 to February 2021. We included patients with atrophic and oligotrophic nonunion, and hypertrophic nonunion with malalignment that needed to be corrected. The other patient group was consisted of segmental bone defect resulted from FRI. The maximum amount of rhBMP-2 allowed in this clinical study was 6 mg and was added to autologous bone at a 1:1 ratio. Autologous bone was added to the mixture if the volume of mixed graft was insufficient to fill the bone defect. Patients were followed 3, 6, and 12 months post-operatively. Each visit, a radiograph was taken for assessment. Visual analog scale (VAS), questionnaire for quality of life (SF-12 physical component summary [PCS], mental component summary [MCS]), and weight-bearing status were collected for functional outcome assessment. Drug safety was assessed by examining BMP-2 antibodies.

RESULTS

Of the 24 enrolled patients (mean age: 57 years), 15 (62.5 %), 2 (8.33 %), and 7 (29.17 %) presented atrophic nonunion, hypertrophic nonunion with deformity, and bone defect after fracture related infection, respectively. Thirteen patients had nonunion in the femur, 9 in the tibia, and 1 in the humerus and radius. The average amount of harvested autologous bone was 9.25 g and 4.96 mg of rhBMP-2. All 24 patients achieved union after 1-year follow up. The union rate was 95.83 % and 100 % at 6 and 12 months postoperatively, respectively. Preoperative SF-12 PCS (mean: 34.71) improved at 6 and 12 months postoperatively, respectively. Preoperative SF-12 MCS (mean: 42.89) improved 12 months postoperatively (49.13, p = 0.0338). Change of VAS was statistically significant 3 months postoperatively (p = 0.0012). No adverse effects or development of BMP-2 antibodies were observed.

CONCLUSION

BMP-2 combined with autogenous bone resulted in excellent radiographical and functional outcomes in a relatively small prospective series of patients with nonunion and bone defect, without adverse effects. Further investigations are necessary to support our finding and optimize treatment strategies in nonunion patients.

Assessing the potential role of ChatGPT in spine surgery research

Purpose

Since its release in November 2022, Chat Generative Pre-Trained Transformer 3.5 (ChatGPT), a complex machine learning model, has garnered more than 100 million users worldwide. The aim of this study is to determine how well ChatGPT can generate novel systematic review ideas on topics within spine surgery.

Methods

ChatGPT was instructed to give ten novel systematic review ideas for five popular topics in spine surgery literature: microdiscectomy, laminectomy, spinal fusion, kyphoplasty and disc replacement. A comprehensive literature search was conducted in PubMed, CINAHL, EMBASE and Cochrane. The number of nonsystematic review articles and number of systematic review papers that had been published on each ChatGPT-generated idea were recorded.

Results

Overall, ChatGPT had a 68% accuracy rate in creating novel systematic review ideas. More specifically, the accuracy rates were 80%, 80%, 40%, 70% and 70% for microdiscectomy, laminectomy, spinal fusion, kyphoplasty and disc replacement, respectively. However, there was a 32% rate of ChatGPT generating ideas for which there were 0 nonsystematic review articles published. There was a 71.4%, 50%, 22.2%, 50%, 62.5% and 51.2% success rate of generating novel systematic review ideas, for which there were also nonsystematic reviews published, for microdiscectomy, laminectomy, spinal fusion, kyphoplasty, disc replacement and overall, respectively.

Conclusions

ChatGPT generated novel systematic review ideas at an overall rate of 68%. ChatGPT can help identify knowledge gaps in spine research that warrant further investigation, when used under supervision of an experienced spine specialist. This technology can be erroneous and lacks intrinsic logic; so, it should never be used in isolation.

Level of Evidence

Not applicable.

A synthetic retinoic acid receptor γ antagonist (7C)-loaded nanoparticle enhances bone morphogenetic protein-induced bone regeneration in a rat spinal fusion model

BACKGROUND CONTEXT

Bone morphogenetic proteins (BMPs) have potent osteoinductivity and have been applied clinically for challenging musculoskeletal conditions. However, the supraphysiological doses of BMPs used in clinical settings cause various side effects that prevent widespread use, and therefore the BMP dosage needs to be reduced.

PURPOSE

To address this problem, we synthesized 7C, a retinoic acid receptor γ antagonist-loaded nanoparticle (NP), and investigated its potential application in BMP-based bone regeneration therapy using a rat spinal fusion model.

STUDY DESIGN

An experimental animal study.

METHODS

Fifty-three male 8-week-old Sprague-Dawley rats underwent posterolateral spinal fusion and were divided into the following five treatment groups: (1) no recombinant human (rh)BMP-2 and blank-NP (Control), (2) no rhBMP-2 and 1 μg 7C-NP (7C group), (3) low-dose rhBMP-2 (0.5 μg) and 1 μg blank-NP (L-BMP group), (4) low-dose rhBMP-2 (0.5 μg) and 1 μg 7C-NP (L-BMP + 7C group), and (5) high-dose rhBMP-2 (5.0 μg) and 1 μg blank-NP (H-BMP group). Micro-computed tomography and histologic analysis were performed 2 and 6 weeks after the surgery.

RESULTS

The spinal fusion rates of the Control and 7C groups were both 0%, and those of the L-BMP, L-BMP + 7C, and H-BMP groups were 55.6%, 94.4%, and 100%, respectively. The L-BMP + 7C group markedly promoted cartilaginous tissue formation during BMP-induced endochondral bone formation that resulted in a significantly better spinal fusion rate and bone formation than in the L-BMP group. Although spinal fusion was slower in the L-BMP + 7C group, the L-BMP + 7C group formed a spinal fusion mass with better bone quality than the spinal fusion mass in the H-BMP group.

CONCLUSIONS

The combined use of 7C-NP with rhBMP-2 in a rat posterolateral lumbar fusion model increased spinal fusion rate and new bone volume without deteriorating the quality of newly formed bone.

CLINICAL SIGNIFICANCE

7C-NP potentiates BMP-2-induced bone regeneration and has the potential for efficient bone regeneration with low-dose BMP-2, which can reduce the dose-dependent side effects of BMP-2 in clinical settings.

Mechanical performance of porous biomimetic intervertebral body fusion devices: an in vitro biomechanical study

BACKGROUND

Degenerative disc disease is one of the most common ailments severely affecting the quality of life in elderly population. Cervical intervertebral body fusion devices are utilized to provide stability after surgical intervention for cervical pathology. In this study, we design a biomimetic porous spinal cage, and perform mechanical simulations to study its performances following American Society for Testing and Materials International (ASTM) standards before manufacturing to improve design process and decrease cost and consumption of material.

METHODS

The biomimetic porous Ti-6Al-4 V interbody fusion devices were manufactured by selective laser melting (laser powder bed fusion: LPBF in ISO/ASTM 52900 standard) and subsequently post-processed by using hot isostatic pressing (HIP). Chemical composition, microstructure and the surface morphology were studied. Finite element analysis and in vitro biomechanical test were performed.

FINDINGS

The post heat treatment can optimize its mechanical properties, as the stiffness of the cage decreases to reduce the stress shielding effect between two instrumented bodies. After the HIP treatment, the ductility and the fatigue performance are substantially improved. The use of HIP post-processing can be a necessity to improve the physical properties of customized additive manufacturing processed implants.

INTERPRETATION

In conclusion, we have successfully designed a biomimetic porous intervertebral device. HIP post-treatment can improve the bulk material properties, optimize the device with reduced stiffness, decreased stress shielding effect, while still provide appropriate space for bone growth.

CLINICAL SIGNIFICANCE

The biomechanical performance of 3-D printed biomimetic porous intervertebral device can be optimized. The ductility and the fatigue performance were substantially improved, the simultaneously decreased stiffness reduces the stress shielding effect between two instrumented bodies; while the biomimetic porous structures provide appropriate space for bone growth, which is important in the patients with osteoporosis.

Advances in bone regeneration with growth factors for spinal fusion: A literature review

Bone tissue is regenerated via the spatiotemporal involvement of various cytokines. Among them, the bone morphogenetic protein (BMP), which plays a vital role in the bone regeneration process, has been applied clinically for the treatment of refractory orthopedic conditions. Although BMP therapy using a collagen carrier has shown efficiency in bone regeneration over the last two decades, a major challenge-considerable side effects associated with the acute release of high doses of BMPs-has also been revealed. To improve BMP efficiency, the development of new carriers and biologics that can be used in conjunction with BMPs is currently underway. In this review, we describe the current status and future prospects of bone regeneration therapy, with a focus on BMPs. Furthermore, we outline the characteristics and molecular signaling pathways involving BMPs, clinical applications of BMPs in orthopedics, clinical results of BMP use in human spinal surgeries, drugs combined with BMPs to provide synergistic effects, and novel BMP carriers.

Evaluation of the efficacy and safety of Escherichia coli-derived recombinant human bone morphogenetic protein-2 in transforaminal lumbar interbody fusion to treat degenerative spinal disease: a protocol of prospective, randomized controlled, assessor-blinded, open-label, multicenter trial

Background

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely used as an alternative bone graft in spine fusion surgery. However, clinical outcome such as effects and complications has not yet been revealed for transforaminal lumbar interbody fusion (TLIF). Although previous studies have reported some results, the evidence is weak. Therefore, the purpose of this trial is to evaluate the effectiveness and safety of Escherichia coli-derived rhBMP-2 combined with hydroxyapatite (HA) in TLIF.

Methods

This trial is designed as a prospective, assessor-blinded, open-label, multicenter, randomized controlled study. Participants will be recruited from six tertiary teaching hospitals. All randomized participants will be undergoing one- or two-level TLIF with rhBMP-2 (77 participants) as the active experimental group or with an auto-iliac bone graft (77 participants) as the control group. The primary interbody fusion rate outcome will be evaluated using computed tomography (CT) 12 months after surgery. The secondary outcomes will be as follows: clinical outcomes (visual analog scale score, EuroQol-5-dimensions-5-level score, Oswestry Disability Index score, and some surgery-related variables) and adverse effects (radiculitis, heterotrophic ossification, endplate resorption, and osteolysis). Radiological outcomes will be evaluated using simple radiography or CT. All outcomes will be measured, collected, and evaluated before surgery and at 12, 24, and 52 weeks postoperatively.

Discussion

This study will be the primary of its kind to evaluate the effectiveness and safety of E. coli-derived rhBMP-2 with HA in one- or two-level TLIF. It is designed to evaluate the equivalence of the results between rhBMP-2 with HA and auto-iliac bone graft using an appropriate sample size, assessor-blinded analyses, and prospective registration to avoid bias. This study will set up clear conclusions for using E. coli-derived rhBMP-2 with HA in TLIF.

Trial registration: This study protocol was registered at Korea Clinical Research Information Service (https://cris.nih.go.kr; number identifier: KCT0005610) on 19 November 2020. And protocol version is v1.1, January 2022.

Off-label usage of RhBMP-2 in posterior cervical fusion is not associated with early increased complication rate and has similar clinical outcomes

BACKGROUND CONTEXT

Arthrodesis is important for the success of posterior cervical fusion (PCF), however, there exists limited data regarding the safety and efficacy of bone morphogenic protein (BMP) in PCF.

PURPOSE

The primary objective was to evaluate early postoperative complications associated with BMP in PCF and determine whether BMP leads to adverse early clinical outcomes. A secondary objective was to determine the optimal location for BMP sponge placement, within the facet joint (IF) or elsewhere, and the optimal dosage/level.

DESIGN

Retrospective, consecutive case-control study.

PATIENT SAMPLE

Seven hundred sixty-five patients who underwent PCF OUTCOME MEASURES: Patient-reported outcomes (PROs), complications, arthrodesis, optimum dose/level of BMP METHODS: Surgical data, including preoperative diagnosis, levels fused, type of bone graft, BMP dose (when used), and fusion technique were recorded. Complications were assessed by reviewing the medical record encompassing the first 6-weeks postoperative. These included medical, neurological, and wound-related complications and reoperation. Neurological complications were defined as any new weakness, radicular pain, or numbness. PROs were collected, including SF36, VAS, EQ-5D, and NDI scores. To determine the optimal dosage and location for BMP placement, a sub-analysis was performed.

RESULTS

There were no significant differences between the BMP and no BMP group with regards to wound complications, neurological complications, or reoperation. There were no differences in PROs between BMP and no BMP. Placement of BMP for IF and at a dose of 0.87 mg/level minimized wound-related complications. The BMP group had a higher fusion rate compared to the no BMP group (96% vs. 91%, p=.02) when assessed 1 year post-operatively.

CONCLUSION

BMP was not associated with a higher rate of early complications after PCF when the dose was minimized. Complications thought to be associated with BMP, such as compressive seroma, radiculitis, and wound-related complications were not seen at a higher rate. PROs at early follow-up were similar. Placement of BMP for IF and at lower doses than previously reported may minimize complications.

Three interfaces of the dental implant system and their clinical effects on hard and soft tissues

Anatomically, the human tooth has structures both embedded within and forming part of the exterior surface of the human body. When a tooth is lost, it is often replaced by a dental implant, to facilitate the chewing of food and for esthetic purposes. For successful substitution of the lost tooth, hard tissue should be integrated into the implant surface. The microtopography and chemistry of the implant surface have been explored with the aim of enhancing osseointegration. Additionally, clinical implant success is dependent on ensuring that a barrier, comprising strong gingival attachment to an abutment, does not allow the infiltration of oral bacteria into the bone-integrated surface. Epithelial and connective tissue cells respond to the abutment surface, depending on its surface characteristics and the materials from which it is made. In particular, the biomechanics of the implant-abutment connection structure (i.e., the biomechanics of the interface between implant and abutment surfaces, and the screw mechanics of the implant-abutment assembly) are critical for both the soft tissue seal and hard tissue integration. Herein, we discuss the clinical importance of these three interfaces: bone-implant, gingiva-abutment, and implant-abutment.

Radiographic and Patient-Reported Outcomes of Lordotic Versus Non-lordotic Static Interbody Devices in Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Longitudinal Comparative Cohort Study

Introduction Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is increasingly used to treat lumbar degenerative pathology. Its effect on sagittal parameters remains controversial. Static and expandable lordotic interbody devices (cages) were developed to improve segmental and overall lumbar lordosis. This study aimed to compare the radiographic and patient-reported outcomes (PROs) between static lordotic and non-lordotic titanium cages in patients undergoing 1-2 level MI-TLIF for degenerative conditions.  Methods We reviewed consecutive eligible patients who underwent 1-2 level MI-TLIF (7/2017-11/2019) at a single institution by multiple surgeons. Standing X-rays and PROs were collected at preoperative, 1-month, and 6-month postoperative intervals. Using univariate analyses, we compared the two cohorts regarding confounders, radiographic parameters, and proportions of patients reaching minimal clinically important difference (MCID) for PROs. Results One-hundred-twenty-five patients were reviewed. Forty-seven had lordotic and seventy-eight non-lordotic cages. The lordotic cohort was significantly younger than the non-lordotic (55.9 years vs. 60.7 years, p= 0.042). The baseline radiographic parameters were not significantly different between cohorts. At the preoperative-6-month interval, the lordotic cohort had significant improvement in lumbar lordosis versus non-lordotic cohort (2.95° ± 7.2° vs. -0.3° ± 7.1°, p=0.024). Both cohorts showed improvement in segmental lordosis, anterior and posterior interspace height, and low subsidence grade with no significant difference between cohorts at all intervals. Overall, 69.1-83.8% of patients achieved MCID in all PROs with no significant difference between cohorts. Conclusions The use of a static lordotic titanium cage in 1-2 level MI-TLIF did not result in significantly different radiographic improvements or PROs compared with a non-lordotic cage.

Image Guidance-Assisted Decompression and Removal of Heterotopic Ossification Following the Use of Recombinant Human Bone Morphogenetic Protein-2 in Transforaminal Lumbar Interbody Fusion

Heterotopic ossification (HO) following the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in the setting of transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) is a troublesome and well-described postoperative complication. There is currently no consensus regarding the treatment of this offending pathology. In this report, we present a retrospective single-surgeon review of 14 patients who underwent image-guided decompression of HO. We describe a new technique where navigation demonstrates a safe and thorough decompression compared to that with fluoroscopy or anatomical landmarks alone. To evaluate successful decompression, we reviewed patient self-reported clinical outcomes. Seven patients demonstrated positive results, while three had mixed outcomes and four showed poor outcomes. While more studies are needed to determine the overall efficacy of intraoperative navigation-assisted decompression, findings from this small cohort of patients suggest that it is a useful technique in the setting of the removal of heterotopic bone.

Changes in Recombinant Human Bone Morphogenetic Protein-2 Use in Posterior Fusion Over the Past Two Decades

Background

In 2011, studies suggested that complications and cancer rates associated with bone morphogenetic protein (BMP) were greater than previously reported. However, later studies reported complication rates similar to prior literature and no increased cancer rate. We evaluated the pattern of clinical utilization of BMP in posteriorly based lumbar fusion by comparing two periods: 2002-2004 and 2017-2019.

Methods

Patients who received BMP from 2002-2004 (Early) and 2017-2019 (Late) from a single multi-surgeon institution who had a lumbar fusion were identified. One hundred patients from each cohort were randomly selected. Mean total BMP used at each level and the proportion of BMP placed in the interbody space versus posterolateral gutters were evaluated.

Results

In the transforaminal lumbar intebody fusion (TLIF) cohort, the total BMP dose in the Late group (6.15 mg) was nearly half of that used in the Early group (12.04 mg, p<0.000). The amount of BMP used in the posterolateral gutters remained similar (Early: 4.01 mg vs Late: 3.38 mg, p=0.222). The amount of BMP used in the interbody space was less in the Late group (2.76 mg) compared to the Early group (8.03 mg, p<0.000). In the posterior spinal fusion (PSF) cohort, the total BMP dose remained similar between the Early (11.96 mg) and the Late groups (10.82 mg, p=0.007).

Conclusion

Change in the use of BMP in TLIF cases was driven by the complications reported in the literature with no change in outcome. A similar impetus was not seen for PSF.

A BMP/Activin A Chimera Induces Posterolateral Spine Fusion in Nonhuman Primates at Lower Concentrations Than BMP-2

BACKGROUND

Supraphysiologic bone morphogenetic protein (BMP)-2 concentrations are required to induce spinal fusion. In this study, a BMP-2/BMP-6/activin A chimera (BV-265), optimized for BMP receptor binding, delivered in a recombinant human collagen:CDHA [calcium-deficient hydroxyapatite] porous composite matrix (CM) or bovine collagen:CDHA granule porous composite matrix (PCM), engineered for optimal BV-265 retention and guided tissue repair, was compared with BMP-2 delivered in a bovine absorbable collagen sponge (ACS) wrapped around a MASTERGRAFT Matrix (MM) ceramic-collagen rod (ACS:MM) in a nonhuman primate noninstrumented posterolateral fusion (PLF) model.

METHODS

In vivo retention of 125I-labeled-BV-265/CM or PCM was compared with 125I-labeled-BMP-2/ACS or BMP-2/buffer in a rat muscle pouch model using scintigraphy. Noninstrumented PLF was performed by implanting CM, BV-265/CM, BV-265/PCM, or BMP-2/ACS:MM across L3-L4 and L5-L6 or L3-L4-L5 decorticated transverse processes in 26 monkeys. Computed tomography (CT) images were acquired at 0, 4, 8, 12, and 24 weeks after surgery, where applicable. Manual palpation, μCT (microcomputed tomography) or nCT (nanocomputed tomography), and histological analysis were performed following euthanasia.

RESULTS

Retention of 125I-labeled-BV-265/CM was greater than BV-265/PCM, followed by BMP-2/ACS and BMP-2/buffer. The CM, 0.43 mg/cm3 BMP-2/ACS:MM, and 0.05 mg/cm3 BV-265/CM failed to generate PLFs. The 0.15-mg/cm3 BV-265/CM or 0.075-mg/cm3 BV-265/PCM combinations were partially effective. The 0.25-mg/cm3 BV-265/CM and 0.15 and 0.3-mg/cm3 BV-265/PCM combinations generated successful 2-level PLFs at 12 and 24 weeks.

CONCLUSIONS

BV-265/CM or PCM can induce fusion in a challenging nonhuman primate noninstrumented PLF model at substantially lower concentrations than BMP-2/ACS:MM.

CLINICAL RELEVANCE

BV-265/CM and PCM represent potential alternatives to induce PLF in humans at substantially lower concentrations than BMP-2/ACS:MM.

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.