Efficacy of Escherichia coli-derived recombinant human bone morphogenetic protein-2 in posterolateral lumbar fusion: an open, active-controlled, randomized, multicenter trial

Biodegradable biomaterials in orthopedic surgery: A narrative review of the current evidence

BACKGROUND

Biomaterials are routinely used in orthopedic surgery to fill bone defects, improve bone healing, and as degradable fixation material. A wide range of materials are currently in use, and the materials are chosen according to their bioactive properties. Osteoinductive materials stimulate bone healing by promoting osteogenesis. Osteoconductive materials facilitate bone growth on the surface of the material. Despite the many materials in use and an increasing number of published studies, randomized controlled trials on the subject are scarce.

METHODS

This review aims to summarize the history of biodegradable biomaterials and also the published level I evidence currently available on orthopedic biomaterials.

RESULTS

Most of the studies have been superiority trials with non-significant differences compared to conventional treatment options, confirming that several biomaterials are suitable treatment options for multiple indications including bone and/or tendon fixation, filling bone defects, and spinal fusion. Biomaterials help to avoid donor site complications associated with autogenous bone grafts and often eliminate the need for implant removal. However, the surgical technique may in some cases be more demanding than with conventional methods. Careful consideration of the pros and cons is therefore recommended in clinical practice.

CONCLUSION

Biodegradable biomaterials complement the range of available treatment options in several fields of orthopedic surgery. However, some biomaterials performed worse than expected and were not recommended for clinical use, emphasizing the need for high-quality randomized trials. It is also noteworthy that several trials included only a limited number of patients, rendering the interpretation of the results of these underpowered studies challenging.

Fusion rate of Escherichia coli-derived recombinant human bone morphogenetic protein-2 compared with local bone autograft in posterior lumbar interbody fusion for degenerative lumbar disorders

BACKGROUND CONTEXT

The use of recombinant human bone morphogenetic proteins-2 (rhBMP-2) for spinal fusion has been reported to be effective. However, most studies have focused on posterolateral and anterior lumbar interbody fusion, and few have investigated posterior lumbar interbody fusion (PLIF).

PURPOSE

This study aimed to determine the effectiveness and safety of the delivery of Escherichia coli-derived rhBMP-2 (E.BMP-2) with hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) poloxamer hydrogel composite carriers for PLIF.

STUDY DESIGN

A retrospective study.

PATIENT SAMPLE

Patients who underwent 1 to 3 levels of PLIF for lumbar degenerative disc disorders between 2015 and 2020 with a follow-up of ≥1 year were enrolled. In total, 254 patients (357 levels) were included in the analysis. The evaluation was performed at each segment level. In the E.BMP-2 group, 160 patients (221 levels) received autologous local bone with E.BMP-2 (maximum 0.5 mg/level), and in the control group, 94 patients (136 levels) received only local bone graft.

OUTCOME MEASURES

The primary outcome of this study was to compare the X-ray and CT fusion rates between the two groups. Secondary outcomes included analysis of the patients' clinical outcomes and postoperative complications on CT scans.

METHODS

Clinical evaluations were performed using a visual analog scale for back pain, the Oswestry Disability Index for disability, and physical and mental component summaries of the Short Form 36-Item Form Health Survey to assess functional effects and quality of life. The fusion was evaluated using radiography and CT. On radiography, solid fusion was defined when the difference between extension and flexion was less than 5°. On CT, solid fusion was defined when the upper and lower vertebral bodies were connected by the trabecular bone (bone bridge formation). In addition, complications such as osteolysis, cage subsidence, and screw loosening were investigated using CT.

RESULTS

All clinical results for low back pain, disability, and quality of life in both groups were excellent and showed statistically significant improvements compared with baseline (p<.0001). According to the X-ray evaluations, fusion was achieved in 92.31% (204/221) of the patients in the E.BMP-2 group and 82.35% (112/136) of the patients in the control group (p=.0041). According to the CT evaluations, the fusion rates were 93.21% (206/221) and 88.24% (120/136) in the E.BMP-2 and control groups (p=.1048), respectively. Except for screw loosening, which had a significantly higher incidence in the control group (p=.0014), the rates of most postoperative complications were not significantly different between the groups.

CONCLUSIONS

This study demonstrated that the adjunctive use of a low dose of E.BMP-2 with HA and β-TCP hydrogel can effectively promote bone fusion, making it a promising option for patients with limited autograft availability or compromised bone quality in PLIF.

Application of Escherichia coli-Derived Recombinant Human Bone Morphogenic Protein-2 to Unstable Spinal Fractures

(1) Background: Recently, Escherichia coli-derived recombinant human bone morphogenetic protein-2 (E. coli-derived rhBMP-2) has been increasingly applied to different types of spinal surgeries and reported to achieve successful fusion. This pilot study aimed to evaluate the clinical efficacy and safety of rhBMP-2 in patients undergoing posterior instrumented fusions for unstable spinal fractures. (2) Methods: This study included ten consecutive patients undergoing spinal surgery using E. coli-derived rhBMP-2 with more than one year of follow-up. Radiologic outcomes were compared, including the average fracture healing period, local kyphosis correction, and clinical outcomes between preoperative and the last follow-up. (3) Results: The average time of radiographic union was 99.9 ± 45.4 (62-192) days, with an average use of 5.2 ± 3.9 months of anabolic agents. Radiologic parameters such as anterior vertebral height and vertebral wedge angle were significantly corrected postoperatively and at the last follow-up. Clinical outcomes other than leg pain were significantly improved after the surgery. In addition, four patients with preoperative neurologic deficits showed improved neurologic status. (4) Conclusions: Combined with the anabolic agents, applying E. coli-derived rhBMP-2 to the fractured vertebral body could be an effective surgical treatment for unstable spinal fractures. Further trials are needed to validate this result.

Application of nano-hydroxyapatite matrix graft in inter-vertebral fusion therapy: a meta-analysis

OBJECTIVE

Nano-hydroxyapatite and its composites(nHA) have been widely used as grafts in inter-vertebral fusion. However, the safety and efficacy of the graft in inter-vertebral fusion is controversial. This meta-analysis aimed at evaluating the safety and efficacy of nHA and non-hydroxyapatite grafts (noHA) (autologous bone, etc.) in inter-body fusion.

MATERIALS AND METHODS

A comprehensive search was performed in electronic database as follows: PubMed, EMBASE, the Cochrane Library, Web of Science, and China National Knowledge Internet (CNKI) from inception until October 2022. Clinical studies on the effect of nHA and noHA in spinal fusion were collected. Analysis of outcome indicators using RevMan 5.4 statistical software.

RESULTS

The meta-analysis showed that the operation time of patients who underwent inter-body fusion with nHA grafts was less than that of patients who underwent noHA (p < 0.05). Compared with the noHA group, the nHA group can achieve similar clinical effects in the fusion rate(OR = 1.29,95%CI: 0.88 to 1.88,p = 0.19),Subsidence rate(OR = 1.2,95%CI:0.44 to 3.28,p = 0.72), inter-vertebral space height(SMD = 0.04,95%CI:-0.08 to 0.15,p = 0.54),Cobb angle(SMD = 0.21,95%CI: 0.18 to 0.6,p = 0.21),Blood loss(SMD = -36.58,95%CI: -81.45 to 8.29,p = 0.11),operative time in 12 months(SMD = -5.82,95%CI: -9.98 to -1.67,p = 0.006) and in the final follow-up(SMD = -0.38,95%CI: -0.51 to -0.26,p < 0.00001),ODI(SMD = 0.68,95%CI: -0.84 to 2.19,p = 0.38), VAS(SMD = 0.17,95%CI: -0.13 to 0.48,p = 0.27) and adverse events(OR = 0.98,95%CI: 0.66 to 1.45,p = 0.92), and the differences are not statistically significant.

CONCLUSION

This meta-analysis suggests that nHA matrix grafts are similar to noHA grafts in the safety and efficacy of spinal reconstruction, and are an ideal material for inter-vertebral bone grafting.

Mid-term efficacy and safety of Escherichia coli-derived rhBMP-2/hydroxyapatite carrier in lumbar posterolateral fusion: a randomized, multicenter study

PURPOSE

This study aimed to evaluate the mid-term efficacy and safety of Escherichia coli-derived bone morphogenetic protein-2 (E.BMP-2)/hydroxyapatite (HA) in lumbar posterolateral fusion (PLF).

METHODS

This multicenter, evaluator-blinded, observational study utilized prospectively collected clinical data. We enrolled 74 patients who underwent lumbar PLF and had previously participated in the BA06-CP01 clinical study, which compared the short-term outcomes of E.BMP-2 with an auto-iliac bone graft (AIBG). Radiographs and CT scans were analyzed to evaluate fusion grade at 12, 24, and 36 months. Visual analog scale (VAS), Oswestry disability index (ODI), and Short Form-36 (SF-36) scores were measured preoperatively and at 36 months after surgery. All adverse events in this study were assessed for its relationship with E.BMP-2.

RESULTS

The fusion grade of the E.BMP-2 group (4.91 ± 0.41) was superior to that of the AIBG group (4.25 ± 1.26) in CT scans at 36 months after surgery (p = 0.007). Non-union cases were 4.3% in the E.BMP-2 and 16.7% in the AIBG. Both groups showed improvement in pain VAS, ODI, and SF-36 scores when compared to the baseline values, and there were no statistically significant differences between the two groups. No treatment-related serious adverse reactions were observed in either group. No neoplasm-related adverse events occurred in the E.BMP-2 group.

CONCLUSIONS

The fusion quality of E.BMP-2/HA was superior to that of AIBG. E.BMP-2/HA showed comparable mid-term outcomes to that of AIBG in terms of efficacy and safety in one-level lumbar PLF surgery.

Improving bone morphogenetic protein (BMP) production in CHO cells through understanding of BMP synthesis, signaling and endocytosis

Bone morphogenetic proteins (BMPs) are a group of growth factors with the clinical potential to regulate cartilage and bone formation. Functionally active mature recombinant human BMPs (rhBMPs), produced primarily in Chinese hamster ovary (CHO) cells for clinical applications, are considered difficult to express because they undergo maturation processes, signaling pathways, or endocytosis. Although BMPs are a family of proteins with similar mature domain sequence identities, their individual properties are diverse. Thus, understanding the properties of individual rhBMPs is essential to improve rhBMP production in CHO cells. In this review, we discuss various approaches to improve rhBMP production in CHO cells by understanding the overall maturation process, signaling pathways and endocytosis of individual rhBMPs.

Promoting angiogenesis and diabetic wound healing through delivery of protein transduction domain-BMP2 formulated nanoparticles with hydrogel

Decreased angiogenesis contributes to delayed wound healing in diabetic patients. Recombinant human bone morphogenetic protein-2 (rhBMP2) has also been demonstrated to promote angiogenesis. However, the short half-lives of soluble growth factors, including rhBMP2, limit their use in wound-healing applications. To address this limitation, we propose a novel delivery model using a protein transduction domain (PTD) formulated in a lipid nanoparticle (LNP). We aimed to determine whether a gelatin hydrogel dressing loaded with LNP-formulated PTD-BMP2 (LNP-PTD-BMP2) could enhance the angiogenic function of BMP2 and improve diabetic wound healing. In vitro, compared to the control and rhBMP2, LNP-PTD-BMP2 induced greater tube formation in human umbilical vein endothelial cells and increased the cell recruitment capacity of HaCaT cells. We inflicted large, full-thickness back skin wounds on streptozotocin-induced diabetic mice and applied gelatin hydrogel (GH) cross-linked by microbial transglutaminase containing rhBMP2, LNP-PTD-BMP2, or a control to these wounds. Wounds treated with LNP-PTD-BMP2-loaded GH exhibited enhanced wound closure, increased re-epithelialization rates, and higher collagen deposition than those with other treatments. Moreover, LNP-PTD-BMP2-loaded GH treatment resulted in more CD31- and α-SMA-positive cells, indicating greater neovascularization capacity than rhBMP2-loaded GH or GH treatments alone. Furthermore, in vivo near-infrared fluorescence revealed that LNP-PTD-BMP2 has a longer half-life than rhBMP2 and that BMP2 localizes around wounds. In conclusion, LNP-PTD-BMP2-loaded GH is a viable treatment option for diabetic wounds.

Anterior Cervical Discectomy and Fusion Using Escherichia coli-Derived Recombinant Human Bone Morphogenetic Protein-2: A Pilot Study

BACKGROUND

Recombinant human bone morphogenetic protein-2 (BMP-2) is an osteoinductive growth factor widely used in orthopedic surgery; it is also known to be associated with postoperative airway compromise or dysphagia when applied to anterior cervical discectomy and fusion (ACDF). However, there have been no reports on ACDF using Escherichia coli-derived BMP-2 (E.BMP-2) with hydroxyapatite (HA). This pilot study aimed to investigate the potential efficacy and safety of E.BMP-2 using HA as a carrier in ACDF prior to designing a larger-scale prospective study.

METHODS

Patients eligible for inclusion were those who underwent ACDF using 0.3 mg of E.BMP-2 with HA per segment for degenerative cervical disc disease between August 2019 and July 2020 and had at least 1 year of follow-up. Fusion rates were analyzed using computed tomography or flexion-extension radiographs. Visual analog scales for neck pain and arm pain and neck disability index were measured preoperatively and the final follow-up. In cases of cervical spondylotic myelopathy, modified Japanese Orthopaedic Association scores were also evaluated. Postoperative complications such as airway compromise, dysphagia, wound infection, neurologic deficit, hoarseness, heterotopic ossification, seroma, and malignancy were investigated.

RESULTS

A total of 11 patients and 21 segments were analyzed. All clinical outcomes significantly improved at the final follow-up compared with the preoperative indices (p < 0.05). Only 1 case of dysphagia and no cases of airway compromise, wound infection, neurologic deficit, hoarseness, heterotopic ossification, seroma, or malignancy were observed during the follow-up period. Of the 21 segments, 15 segments showed solid fusion at 3 months after surgery, 4 segments at 6 months, and 1 segment at 12 months. Only 1 segment showed pseudoarthrosis, resulting in a fusion rate of 95.2%.

CONCLUSIONS

The outcomes of ACDF could be enhanced using 0.3 mg of E.BMP-2 with HA per segment. Based on this study, larger-scale prospective studies can be conducted to evaluate the efficacy and safety of E.BMP-2 in ACDF.

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.

Effectiveness and Feasibility of Injectable Escherichia coli-Derived Recombinant Human Bone Morphogenetic Protein-2 for Anterior Lumbar Interbody Fusion at the Lumbosacral Junction in Adult Spinal Deformity Surgery: A Clinical Pilot Study

Objective

To explore the effectiveness and feasibility of injectable Escherichia coli‐derived recombinant human bone morphogenetic protein‐2 (injectable E‐rhBMP‐2, a combination of E. coli‐derived recombinant human bone morphogenic protein‐2 and a hydrogel type beta‐tricalcium phosphate carrier) as a bone substitute for anterior lumbar interbody fusion (ALIF) of the lumbosacral junction in adult spinal deformity (ASD) patients.

Methods

A prospective single‐institution therapeutic exploratory trial was conducted. Twenty patients (average age: 69.1 years; 19 female and one male; average fusion level: 7.95) diagnosed with ASD with sagittal imbalance who underwent surgical treatment including ALIF at the lumbosacral junction from December 2017 to January 2019 were evaluated. Injectable E‐rhBMP‐2 was prepared by dissolving 3 mg of E. coli‐derived recombinant human bone morphogenetic protein‐2 in 1.5 ml H₂O and mixing in situ with 9 g hydrogel type beta‐tricalcium phosphate. This bone graft substitute was loaded onto a metal ALIF cage and L₅–S₁ ALIF was performed in routine manner. Then posterior column osteotomy with multilevel oblique lumbar interbody fusion or pedicle subtraction osteotomy with accessory rod technique was performed to restore sagittal balance. Patients were followed up for 12 months. CT‐based fusion rates were examined at 6 and 12 months after surgery. Also, clinical outcomes (Oswestry Disability Index [ODI], Visual Analog Scale [VAS] score of the back and leg) were evaluated at 6 and 12 months after surgery. All postoperative adverse events were evaluated for the association with injectable E.BMP‐2.

Results

Of the 20 patients, loss to follow‐up occurred with one patient at 6 months after surgery and one patient at 12 months after surgery, resulting in a total of 18 patients who were available for follow‐up. Six months after surgery, 68.4% patients achieved solid fusion. Twelve months after surgery, 100% fusion rate was achieved. Compared to baseline values, ODI scores improved to 45.8% and 63.7%, VAS (back) improved to 69.2% and 72.8%, and VAS (leg) improved to 49.2% and 64.8%, respectively, at 6 and 12 months after surgery (p < 0.001 for all). Ten cases of adverse events occurred. But no adverse events were associated with injectable E‐rhBMP‐2.

Conclusion

Injectable E‐rhBMP‐2 will be an effective bone graft substitute when achieving solid interbody fusion in the lumbosacral junction.

BMP-2 Induced Signaling Pathways and Phenotypes: Comparisons Between Senescent and Non-senescent Bone Marrow Mesenchymal Stem Cells

The use of BMP-2 in orthopedic surgery is limited by uncertainty surrounding its effects on the differentiation of mesenchymal stem cells (MSCs) and how this is affected by cellular aging. This study compared the effects of recombinant human BMP-2 (rhBMP-2) on osteogenic and adipogenic differentiation between senescent and non-senescent MSCs. Senescent and non-senescent MSCs were cultured in osteogenic and adipogenic differentiation medium containing various concentrations of rhBMP-2. The phenotypes of these cells were compared by performing a calcium assay, adipogenesis assay, staining, real-time PCR, western blotting, and microarray analysis. rhBMP-2 induced osteogenic differentiation to a lesser extent (P < 0.001 and P = 0.005 for alkaline phosphatase activity and Ca²⁺ release) in senescent MSCs regardless of dose-dependent increase in both cells. However, the induction of adipogenic differentiation by rhBMP-2 was comparable between them. There was no difference between these two groups of cells in the adipogenesis assay (P = 0.279) and their expression levels of PPARγ were similar. Several genes such as CHRDL1, NOG, SMAD1, SMAD7, and FST encoding transcription factors were proposed to underlie the different responses of senescent and non-senescent MSCs to rhBMP-2 in microarray analyses. Furthermore, inflammatory, adipogenic, or cell death-related signaling pathways such as NF-kB or p38-MAPK pathways were upregulated by BMP-2 in senescent MSCs, whereas bone forming signaling pathways involving BMP, SMAD, and TGF- ß were upregulated in non-senescent MSCs as expected. This phenomenon explains bone forming dominance by non-senescent MSCs and possible frequent complications such as seroma, osteolysis, or neuritis in senescent MSCs during BMP-2 use in orthopedic surgery.

Therapeutics for enhancement of spinal fusion: A mini review

Objective

With the advances in biological technologies over the past 20 years, a number of new therapies to promote bone healing have been introduced. Particularly in the spinal surgery field, more unprecedented biological therapeutics become available to enhance spinal fusion success rate along with advanced instrumentation approaches. Yet surgeons may not have been well informed about their safety and efficacy profiles in order to improve clinical practices. Therefore there is a need to summarize the evidence and bring the latest progress to surgeons for better clinical services for patients.

Methods

We comprehensively reviewed the literatures in regard to the biological therapeutics for enhancement of spinal fusion published in the last two decades.

Results

Autograft bone is still the gold standard for bone grafting in spinal fusion surgery due to its good osteoconductive, osteoinductive, and osteogenic abilities. Accumulating evidence suggests that adding rhBMPs in combination with autograft effectively promotes the fusion rate and improves surgical outcomes. However, the stimulating effect on spinal fusion of other growth factors, including PDGF, VEGF, TGF-beta, and FGF, is not convincing, while Nell-1 and activin A exhibited preliminary efficacy. In terms of systemic therapeutic approaches, the osteoporosis drug Teriparatide has played a positive role in promoting bone healing after spinal surgery, while new medications such as denosumab and sclerostin antibodies still need further validation. Currently, other treatment, such as controlled-release formulations and carriers, are being studied for better releasing profile and the administration convenience of the active ingredients.

Conclusion

As the world's population continues to grow older, the number of spinal fusion cases grows substantially due to increased surgical needs for spinal degenerative disease (SDD). Critical advancements in biological therapeutics that promote spinal fusion have brought better clinical outcomes to patients lately. With the accumulation of higher-level evidence, the safety and efficacy of present and emerging products are becoming more evident. These emerging therapeutics will shift the landscape of perioperative therapy for the enhancement of spinal fusion.

Comparative Study of Radiological and Clinical Outcomes in Patients Undergoing Minimally Invasive Lateral Lumbar Interbody Fusion Using Demineralized Bone Matrix Alone or with Low-Dose Escherichia coli-Derived rhBMP-2

OBJECTIVE

To compare the results of interbody fusion in patients undergoing minimally invasive lateral lumbar interbody fusion (LLIF) using demineralized bone matrix (DBM) alone versus DBM+recombinant human bone morphogenetic protein-2 (rhBMP2).

METHODS

This retrospective case-controlled study was conducted in patients undergoing minimally invasive LLIF (n = 54) for lumbar interbody fusion; they were divided into 2 groups: DBM-only group and DMB+rhBMP2 group. The improvements of segmental and lumbar lordosis and restoration of disc height were measured, and the interbody fusion rates were determined using a modified Bridwell grading system. Clinical outcomes after surgery, such as visual analog scale scores of back pain and leg pain, and Oswestry disability index were compared.

RESULTS

There were no significant differences in disc height, lumbar and segmental lordosis, or interbody fusion rate between the 2 groups. However, the proportion of Bridwell grade 1 as complete interbody bridging was higher in the DBM+rhBMP2 group than in the DBM-only group at both 6 and 12 months (P < 0.001). Clinical parameters showed equally significant improvement during follow-up in both groups, with no significant differences between the groups.

CONCLUSION

In minimally invasive LLIF, adding Escherichia coli-derived rhBMP2 to DBM did not affect clinical outcomes or radiation parameters, but increased the speed of fusion and interbody bony bridging rate.

Effect of Whitlockite as a new bone substitute for bone formation in spinal fusion and ectopic ossification animal model

BACKGROUND

Bone substrates like hydroxyapatite and tricalcium phosphate have been widely used for promoting spinal fusion and reducing the complications caused by autograft. Whitlockite has been reported to promote better bone formation in rat calvaria models compare with them, but no study investigated its effect on spinal fusion yet. Also, the higher osteoinductivity of whitlockite raised concern of ectopic ossification, which was a complication of spinal fusion surgery that should be avoided.

METHODS

In this study, we compared the osteoinductivity of whitlockite, hydroxyapatite, and tricalcium phosphate porous particles with SD rat spine posterolateral fusion model and investigated whether whitlockite could induce ectopic ossification with SD rat abdominal pouch model.

RESULTS

The micro-CT result from the posterolateral fusion model showed whitlockite had slightly but significantly higher percent bone volume than tricalcium phosphate, though none of the materials formed successful fusion with surrounding bone tissue. The histology results showed the bone formed on the cortical surface of the transverse process but did not form a bridge between the processes. The result from the abdominal pouch model showed whitlockite did not induce ectopic bone formation.

CONCLUSION

Whitlockite had a potential of being a better bone substrate hydroxyapatite and tricalcium phosphate in spinal fusion with low risk of inducing ectopic ossification.

Comparison of demineralized bone matrix and hydroxyapatite as carriers of Escherichia coli recombinant human BMP-2

Background

Autograft has been widely used in various orthopedic and dental surgery for its superior osteogenicity, osteoinductivity and osteoconductivity. But the available volume of the autograft is limited and the efficacy of it is highly affected by the condition of the patients. Therefore, growth factors such as Escherichia coli bone morphogenetic protein-2 (ErhBMP-2) has been widely used in some countries and regions with various carriers that could affect the effects of the growth factors. Demineralized bone matrix (DBM) has been widely used as a bone graft substitute and growth factor carrier, but its effect as a carrier of ErhBMP-2 was less investigated.

Materials and methods

Rat calvaria defect model was used in this study. We implanted ErhBMP-2 with DBM or hydroxyapatite (HA) as a carrier in 8 mm calvaria defect and compared their bone regeneration effect in 4th week and 8th week after implantation with micro-CT and histology. The data was analyzed with one-way ANOVA method with Bonferroni post-hoc analysis.

Result

The group with DBM as the carrier showed significantly higher bone volume and bone thickness than the groups with HA as the carrier in both weeks. And the histology sections showed less adipose tissue formed in the groups with DBM as the carrier.

Conclusion

DBM could be a better carrier for ErhBMP-2 than HA.

Efficacy and safety of Escherichia coli-derived recombinant human bone morphogenetic protein-2 in additional lumbar posterolateral fusion: minimum 1-year follow-up

BACKGROUND CONTEXT

Recombinant human bone morphogenetic protein-2 (BMP-2) is the growth factor with the most striking osteoinductive performance in orthopedic operations; it is also able to induce heterotopic bone formation. However, there has been little clinical research on Escherichia coli-derived BMP-2 (E.BMP-2).

PURPOSE

To confirm the efficacy and safety of E.BMP-2 with a hydroxyapatite carrier when applied to one-sided posterolateral fusion (PLF) in addition to lumbar interbody fusion (LIF), and to measure the lower dose of E.BMP-2 ever reported achieving solid fusion.

STUDY DESIGN/SETTING

Retrospective case-control study PATIENT SAMPLE: A total of 121 patients who received surgery for one or two levels of fusion for lumbar degenerative spinal stenosis or spondylolisthesis from January 2009 to December 2019 were included.

OUTCOME MEASURES

Clinical and functional outcomes were evaluated using preoperative and final follow-up visual analogue scales for back pain (VAS-BP) and leg pain (VAS-LP), and Korean Oswestry disability index (K-ODI) scores. Fusion rates were evaluated by computed tomography at six months and one year after surgery. In addition, a subgroup analysis of group E according to number of fusion levels was conducted, and the fusion rates in the one-level and two-level fusion groups were compared.

METHODS

LIF and additional one-sided PLF was performed in all patients. They received autogenous iliac bone grafts (Group C, n=69) or 1mg of E.BMP-2 (Group E, n=52).

RESULTS

There were no significant differences between preoperative and final VAS-BP, VAS-LP and K-ODI. The PLF rate was 79.7% for Group C and 82.7% for Group E at postoperative six months, and 94.2% for Group C and 100% for Group E at postoperative one year (p =.679, 0.134, respectively). The LIF rate was 71.0% in Group C and 71.2% in Group E at six months after surgery, and 97.1% in Group C and 100% in Group E at one year (p =.987, 0.506, respectively). In terms of numbers of fusion levels in Group E, PLF rates at six months (p =.486) and one year after surgery were similar in the two groups, as were LIF rates at six months (p =.822) and one year after surgery. There were no cases of malignancy or radiculopathy in Group E during one-year of follow-up.

CONCLUSIONS

One milligram of E.BMP-2 is a safe and effective osteoinductive material in short-level lumbar PLF surgery.

Bone physiological microenvironment and healing mechanism: Basis for future bone-tissue engineering scaffolds

Bone-tissue defects affect millions of people worldwide. Despite being common treatment approaches, autologous and allogeneic bone grafting have not achieved the ideal therapeutic effect. This has prompted researchers to explore novel bone-regeneration methods. In recent decades, the development of bone tissue engineering (BTE) scaffolds has been leading the forefront of this field. As researchers have provided deep insights into bone physiology and the bone-healing mechanism, various biomimicking and bioinspired BTE scaffolds have been reported. Now it is necessary to review the progress of natural bone physiology and bone healing mechanism, which will provide more valuable enlightenments for researchers in this field. This work details the physiological microenvironment of the natural bone tissue, bone-healing process, and various biomolecules involved therein. Next, according to the bone physiological microenvironment and the delivery of bioactive factors based on the bone-healing mechanism, it elaborates the biomimetic design of a scaffold, highlighting the designing of BTE scaffolds according to bone biology and providing the rationale for designing next-generation BTE scaffolds that conform to natural bone healing and regeneration.

Bone morphogenetic protein-2 against iliac crest bone graft for the posterolateral fusion of the lumbar spine: A meta-analysis

BACKGROUND

The impact of bone morphogenetic protein-2 compared to autologous iliac crest bone graft to improve fusion rates for the posterolateral fusion of the lumbar spine remains inconclusive. This meta-analysis was performed to evaluate this relationship.

METHODS

A systematic literature search up to May 2020 was performed and 14 studies were detected with 1516 subjects with 789 of them were bone morphogenetic protein-2 and 727 of them were autologous iliac crest bone graft. They reported relationships between bone morphogenetic protein-2 and autologous iliac crest bone graft on fusion rates for the posterolateral fusion of the lumbar spine. Odds ratio (OR) with 95% confidence intervals (CIs) was calculated comparing the bone morphogenetic protein-2 or autologous iliac crest bone graft on the posterolateral fusion of the lumbar spine risks using the dichotomous and continuous method with a random- or fixed-effect model.

RESULTS

Bone morphogenetic protein-2 had significantly higher fusion rates (OR, 4.19; 95% CI, 2.82-6.20, P < .001); lower surgery time (OR, -26.64; 95% CI, -38.71 to -14.57, P < .001); lower blood loss (OR, -92.84; 95% CI, -131.71 to -53.97, P < .001); lower additional surgical procedures (OR, 0.46; 95% CI, 0.31-0.69, P < .001) and higher Oswestry Disability Index (OR, 1.49; 95% CI, 0.02-2.97, P = .05) compared to autologous iliac crest bone graft. However, no significant difference was found between bone morphogenetic protein-2 and autologous iliac crest bone graft in non-union rates (OR, 0.34; 95% CI, 0.08-1.53, P < .001); hospitalisation days (OR, -0.21; 95% CI, -0.48 to 0.07, P = .14) and adverse events (OR, 0.78; 95% CI, 0.52-1.16, P = .22).

CONCLUSIONS

Bone morphogenetic protein-2 significantly had a higher fusion rate, lower surgery time, lower blood loss, lower additional surgical procedures and higher Oswestry Disability Index compared to autologous iliac crest bone graft. This relationship forces us to recommend bone morphogenetic protein-2 for the posterolateral fusion of the lumbar spine to avoid any possible negative postoperative results.

Comparative Clinical Effectiveness and Safety of Bone Morphogenetic Protein Versus Autologous Iliac Crest Bone Graft in Lumbar Fusion: A Meta-analysis and Systematic Review

STUDY DESIGN

This is a systematic literature review and meta-analysis.

OBJECTIVE

We aimed to evaluate the efficacy and safety of recombinant human bone morphogenetic protein (RhBMP) and autologous iliac crest bone graft (ICBG) in lumbar fusion.

SUMMARY OF BACKGROUND DATA

RhBMP has been emphasized in lumbar fusion due to high fusion success rate. However, ICBG remains the criterion standard graft approach for lumbar fusion. The safety and effectiveness of rhBMP are controversial.

METHODS

Prospective randomized controlled trials were searched from PubMed, EMBASE, and Cochrane Central Register of Controlled Trails by using Medical Subject Headings terms "bone morphogenetic protein,' "bone transplantation,' and "spinal fusion.' Two independent investigators screened eligible studies, assessed the bias of original articles, extracted data including fusion success, Oswestry disability index improvement, improved short form 36 questionnaire scores, adverse events and re-operation, and a subgroup analysis. The GRADE approach was used to grade quality of evidence.

RESULTS

Twenty randomized controlled trials (2185 patients) met the inclusion criteria. There were higher fusion success rate (odds ratio [OR] 3.79, 95% confidence interval [CI] 1.88-7.63, P = 0.0002), better improvement of Oswestry Disability Index (mean difference 1.54, 95% CI 0.18-2.89, P = 0.03), and lower re-operation rate (OR 0.59, 95% CI 0.43-0.80, P = 0.0007) in rhBMP group. Heterogeneity was obvious in fusion success rate (I = 58%); hence, a subgroup analysis, based on protein type (rhBMP-2 or rhBMP-7), was performed, which suggested that only rhBMP-2 was better than ICBG for lumbar fusion. There was no difference in the incidence of adverse events between rhBMP and ICBG (OR 0.91, 95% CI 0.70-1.18, P = 0.47).

CONCLUSION

In lumbar fusion, rhBMP-2 exhibited a higher fusion success rate and reduced the risk of re-operation. No difference in complication rate is between rhBMP (rhBMP-2 and rhBMP-7) and ICBG. We suggest rhBMP especially rhBMP-2 as an effective substitute for ICBG for lumbar fusion.

LEVEL OF EVIDENCE

1.

Interbody fusion in degenerative lumbar spinal stenosis with additional posterolateral fusion using Escherichia coli-derived bone morphogenetic protein-2: A Pilot study

This case series investigated the efficacy and optimal dose of Escherichia coli-derived bone morphogenetic protein-2 (E.BMP-2) as a bone graft substitute for additional posterolateral spinal fusion, accompanying interbody fusion procedures, for treating lumbar degenerative spinal stenosis. This study focused on the optimal dose for each segment and the efficacy of E.BMP-2 as a substitute for autogenous iliac bone graft.Ten patients were enrolled from January 2015 to December 2015, and underwent an additional posterolateral fusion procedure, with 2.5 mg of E.BMP-2 followed by decompression, transpedicular fixation, and interbody fusion. The mean follow-up period was 13.9 months, and regular radiological examinations were performed in every case. Clinical outcomes were measured with a visual analog scale for back pain (VAS-BP), and leg pain (VAS-LP) and the Korean Oswestry Disability Index (K-ODI). All parameters were assessed preoperatively and postoperatively at 12 months.All 18 segments treated with E.BMP-2 completely fused in 6 months as observed on both simple radiography and computed tomography. The mean fusion period was 4.5 months on simple radiography. At 12 months follow-up, VAS-BP, VAS-LP, and K-ODI scores (1.9 ± 1.5, 1.9 ± 1.9, 11.0 ± 6.6, respectively) had improved significantly compared to preoperative scores (5.5 ± 1.9, 6.5 ± 1.9, and 49.9 ± 11.5, respectively, P < .05). There were no postoperative wound infections, neurological symptoms, or complications associated with the use of E.BMP-2 during the follow-up period.E.BMP-2 could be used to enhance the outcomes in posterolateral spinal fusion following interbody fusion surgery. In the present study, 2.5 mg of the E.BMP-2 per segment was sufficient to obtain bony union in posterolateral fusion surgery. Further large-scale trials with long-term follow-up are necessary to evaluate the various complications related to the use of E.BMP-2.

Superiority Claims for Spinal Devices: A Systematic Review of Randomized Controlled Trials

STUDY DESIGN

Systematic review.

OBJECTIVES

Superiority claims for medical devices are commonly derived from noninferiority trials, but interpretation of such claims can be challenging. This study aimed to (a) establish the prevalence of noninferiority and superiority designs among spinal device trials, (b) assess the frequency of post hoc superiority claims from noninferiority studies, and (c) critically evaluate the risk of bias in claims that could translate to misleading conclusions.

METHODS

Study bias was assessed using the Cochrane Risk of Bias Tool. The risk of bias for the superiority claim was established based on post hoc hypothesis specification, analysis of the intention-to-treat population, post hoc modification of a priori primary outcomes, and sensitivity analyses.

RESULTS

Forty-one studies were identified from 1895 records. Nineteen (46%) were noninferiority trials. Fifteen more (37%) were noninferiority trials with a secondary superiority hypothesis specified a priori. Seven (17%) were superiority trials. Of the 34 noninferiority trials, 14 (41%) made superiority claims. A medium or high risk of bias was related to the superiority claim in 9 of those trials (64%), which was due to the analyzed population, lacking sensitivity analyses, claims not being robust during sensitivity analyses, post hoc hypotheses, or modified endpoints. Only 4 of the 14 (29%) noninferiority studies provided low bias in the superiority claim, compared with 3 of the 5 (60%) superiority trials.

CONCLUSIONS

Health care decision makers should carefully evaluate the risk of bias in each superiority claim and weigh their conclusions appropriately.

Biomimetic UHMWPE/HA scaffolds with rhBMP-2 and erythropoietin for reconstructive surgery

A promising direction for the replacement of expanded bone defects is the development of bioimplants based on synthetic biocompatible materials impregnated with growth factors that stimulate bone remodeling. Novel biomimetic highly porous ultra-high molecular weight polyethylene (UHMWPE)/40% hydroxyapatite (HA) scaffold for reconstructive surgery with the porosity of 85 ± 1% vol. and a diameter of pores in the range of 50-800 μm was developed. The manufacturing process allowed the formation of trabecular-like architecture without additional solvents and thermo-oxidative degradation. Biomimetic UHMWPE/HA scaffold was biocompatible and provided effective tissue ingrowth on a model of critical-sized cranial defects in mice. The combined use of UHMWPE/HA with Bone Morphogenetic Protein-2 (BMP-2) demonstrated intensive mineralized bone formation as early as 3 weeks after surgery. The addition of erythropoietin (EPO) significantly enhanced angiogenesis in newly formed tissues. The effect of EPO of bacterial origin on bone tissue defect healing was demonstrated for the first time. The developed biomimetic highly porous UHMWPE/HA scaffold can be used separately or in combination with rhBMP-2 and EPO for reconstructive surgery to solve the problems associated with difference between implant architecture and trabecular bone, low osteointegration and bioinertness.

A meta-analysis of bone morphogenetic protein-2 versus iliac crest bone graft for the posterolateral fusion of the lumbar spine

The impact of autologous iliac crest bone graft versus BMP-2 to improve fusion rates for posterolateral fusion (PLF) of the lumbar spine remains unanswered. Single-institution-centered data dominate the literature, providing results that may be contradictory or inconclusive. The aim of this paper is to analyze data pooled from multiple well-controlled studies that examined both ICBG and BMP-2 for use in PLF. This meta-analysis also provides details of success in different subsets of patients with variable risk factors for delayed and non-unions. Six high-quality randomized clinical trials were selected. Efficacy, morbidity, quality of life, and safety were compared between the BMP-2 group and the ICBG group. A total of 908 patients were included in the study. At 24 months, 94% of patients achieved fusion in the BMP-2 group and 83% in the ICBG group. At 6 and 12 months, the fusion was also greater in the BMP-2 group (86% vs. 60% and 88% vs. 80%, respectively). Surgical time, intraoperative blood loss, and hospitalization days also showed significant differences in favor of the experimental group (p < 0.01). There were no differences between two groups in the Oswestry Disability Index, 36-Item Short Form Health Survey and Back Pain Score, whereas a greater number of additional surgical procedures were performed in the ICBG group (p = 0.001). In conclusion, the use of BMP-2 in PLF reduced the surgical morbidity and had more beneficial effects on the fusion rate. The quality of life based on clinical scores was the same in both groups.

Efficacy and safety of bone substitutes in lumbar spinal fusion: a systematic review and network meta-analysis of randomized controlled trials

PURPOSE

A variety of alternative grafts to autologous iliac crest bone (ICBG) have been developed for lumbar spondylodesis, due to frequent complications following ICBG harvest. The optimal alternative graft to ICBG, however, remains elusive till now. The purpose of this study was to compare the efficacy and safety of fusion materials in lumbar degeneration diseases and to provide a ranking spectrum of the grafts.

METHODS

Randomized controlled trials (RCTs) comparing different bone grafts in lumbar arthrodesis were eligible for inclusion. A network meta-analysis was performed for endpoints including fusion rate and incidence of adverse events.

RESULTS

Twenty-seven RCTs involving 2488 patients and 13 available interventions were included. rhBMP-2 provided the highest fusion rate, being significantly superior to that of ICBG (OR = 0.21, p < 0.001), autograft local bone (ALB) (OR = 0.18, p = 0.022), rhBMP-7 (OR = 0.15, p < 0.001), allograft (OR = 0.13, p = 0.009), and DBM + ALB (OR = 0.07, p = 0.048). The treatment efficacy of allograft could be significantly enhanced by bone marrow concentrate (BMC) supplying (OR = 0.16, p = 0.010). ICBG ranks second on the frequency of complications, which is significantly higher than that of allograft (OR = 0.14, p = 0.041) and ALB (OR = 0.14, p = 0.030). All of the other comparisons showed similar efficacy and safety profiles between groups.

CONCLUSION

Ranking spectrums of the efficacy and safety for various bone grafts were provided graphically. Though rhBMP-2 was of the highest success rate, the application should be taken with proper caution because of the widely proposed life-threatening adverse events. ALB, ALB plus synthetic ceramic materials and allograft mixed with BMC were also proved to be potentially effective alternative graft to ICBG. These slides can be retrieved under Electronic Supplementary Material.

BMP-2 Gene Delivery-Based Bone Regeneration in Dentistry

Bone morphogenetic protein-2 (BMP-2) is a potent growth factor affecting bone formation. While recombinant human BMP-2 (rhBMP-2) has been commercially available in cases of non-union fracture and spinal fusion in orthopaedics, it has also been applied to improve bone regeneration in challenging cases requiring dental implant treatment. However, complications related to an initially high dosage for maintaining an effective physiological concentration at the defect site have been reported, although an effective and safe rhBMP-2 dosage for bone regeneration has not yet been determined. In contrast to protein delivery, BMP-2 gene transfer into the defect site induces BMP-2 synthesis in vivo and leads to secretion for weeks to months, depending on the vector, at a concentration of nanograms per milliliter. BMP-2 gene delivery is advantageous for bone wound healing process in terms of dosage and duration. However, safety concerns related to viral vectors are one of the hurdles that need to be overcome for gene delivery to be used in clinical practice. Recently, commercially available gene therapy has been introduced in orthopedics, and clinical trials in dentistry have been ongoing. This review examines the application of BMP-2 gene therapy for bone regeneration in the oral and maxillofacial regions and discusses future perspectives of BMP-2 gene therapy in dentistry.

Escherichia coli BMP-2 showed comparable osteoinductivity with Chinese hamster ovary derived BMP-2 with demineralized bone matrix as carrier

Escherichia coli bone morphogenetic protein-2 (ErhBMP-2) had a larger yield but less osteoinductivity than Chinese hamster ovary cell bone morphogenetic protein-2 (CrhBMP-2). Since the release profile of rhBMP-2 affects its osteoinductivity, an appropriate carrier could improve the effect of ErhBMP-2. Demineralized bone matrix (DBM) was one of the most widely used bone substitutes, but few studies evaluated the osteoinductivity of ErhBMP-2 while it was carried by DBM. Therefore, we compared the osteoinductivity of ErhBMP-2 with CrhBMP-2 with DBM as the carrier of each. In vitro results showed ErhBMP-2 had slightly less osteoinductivity than CrhBMP-2. However, with DBM as the carrier, ErhBMP-2 induced significantly more bone regeneration in rat calvaria defects. Therefore, ErhBMP-2 might have comparable osteoinductivity with CrhBMP-2 while carried by DBM.

Evaluation of an increased strut porosity silicate-substituted calcium phosphate, SiCaP EP, as a synthetic bone graft substitute in spinal fusion surgery: a prospective, open-label study

Purpose

Silicate-substituted calcium phosphate-enhanced porosity (SiCaP EP, Inductigraft™, Altapore) is a synthetic bone graft material with enhanced strut porosity of 31–47%. SiCaP EP remains to be fully clinically evaluated in patients undergoing instrumented posterolateral fusion (PLF) surgery. We conducted a prospective, open-label, non-randomised, multicentre clinical study to evaluate efficacy of SiCaP EP as bone grafting material in PLF surgery with instrumentation for treatment of spinal disorders.

Methods

Patients with degenerative disc disease, spondylolisthesis or spinal stenosis underwent PLF surgery with SiCaP EP. The primary endpoint was evaluated in the per protocol population (N = 102) as solid fusion at postoperative month 12 assessed using computed tomography scans, with motion assessed using flexion–extension radiographs. Clinical outcomes included the Oswestry Disability Index, 36-item short-form health survey for quality-of-life, visual analog scale for pain scores and neurological assessments. Adverse events were recorded.

Results

Successful fusion was achieved in 59/89 (66.3%) patients at month 6, 88/102 patients (86.3%) at month 12 (primary endpoint) and 87/96 (90.6%) patients at month 24. Disability and pain reduced following surgery. Quality-of-life improved and neurological function was maintained postoperatively. Forty-three (33.3%) of the 129 patients who underwent surgery experienced adverse events; back pain was most frequent (n = 10); nine and 14 patients experienced serious adverse events judged related to device and procedure, respectively.

Conclusions

Enhanced strut porosity SiCaP EP provided high (month 12: 86.3%) spinal fusion success rates in PLF surgery. Fusion success was associated with improved clinical outcomes in patients within 12 months, relative to baseline.

ClinicalTrials.gov identifier

NCT01452022

Graphical abstract

These slides can be retrieved under Electronic Supplementary Material.

Bone regeneration strategies: Engineered scaffolds, bioactive molecules and stem cells current stage and future perspectives

Bone fractures are the most common traumatic injuries in humans. The repair of bone fractures is a regenerative process that recapitulates many of the biological events of embryonic skeletal development. Most of the time it leads to successful healing and the recovery of the damaged bone. Unfortunately, about 5-10% of fractures will lead to delayed healing or non-union, more so in the case of co-morbidities such as diabetes. In this article, we review the different strategies to heal bone defects using synthetic bone graft substitutes, biologically active substances and stem cells. The majority of currently available reviews focus on strategies that are still at the early stages of development and use mostly in vitro experiments with cell lines or stem cells. Here, we focus on what is already implemented in the clinics, what is currently in clinical trials, and what has been tested in animal models. Treatment approaches can be classified in three major categories: i) synthetic bone graft substitutes (BGS) whose architecture and surface can be optimized; ii) BGS combined with bioactive molecules such as growth factors, peptides or small molecules targeting bone precursor cells, bone formation and metabolism; iii) cell-based strategies with progenitor cells combined or not with active molecules that can be injected or seeded on BGS for improved delivery. We review the major types of adult stromal cells (bone marrow, adipose and periosteum derived) that have been used and compare their properties. Finally, we discuss the remaining challenges that need to be addressed to significantly improve the healing of bone defects.