Retrospective study of posterior cervical fusions with rhBMP-2

Meta-Analysis on Efficacy and Complications of Bone Morphogenetic Protein-2 for Posterior Fusion of Cervical Spine

OBJECTIVE

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is effective for promoting robust fusion for long-level cervical deformity and revision surgeries. However, only a few studies have reported its efficacy and complications in posterior cervical fusion (PCF).

METHODS

Therefore we evaluated the efficacy and complications of rhBMP-2 application in PCF surgery by searching 3 electronic databases (PubMed, Cochrane Database, and EMBASE) for studies that evaluated the use of rhBMP-2 in PCF. Five studies (1 prospective and 4 retrospective) were included in the meta-analysis.

RESULTS

The quality of each study was assessed, and data on pseudarthrosis, wound infection, neurologic, and immediate medical complications were extracted and analyzed. We found that the use of rhBMP-2 in PCF showed significant benefits in terms of pseudarthrosis and no significant increases in the risk for neurologic and immediate medical complications regardless of the dose. However, high-dose (>2.1 mg/level) rhBMP-2 was a risk factor for wound infection after PCF.

CONCLUSIONS

Our meta-analysis of the currently available literature suggests that patients with PCF may benefit from BMP-2 usage without increasing the risk of complications. However, dose control and containment are important to ensure a low risk of complications.

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.

Pseudarthrosis of the Cervical Spine

Pseudarthrosis of the cervical spine represents a common and challenging problem for spine surgeons. Rates vary greatly from as low as 0%-20% to >60% and depend heavily on patient factors, approach, and number of levels. While some patients remain asymptomatic from pseudarthrosis, many require revision surgery due to instability, continued neck pain, or radiculopathy/myelopathy. We aimed to provide a practical, narrative review of cervical pseudarthrosis to address the following areas: (1) definitions, (2) incidence, (3) risk factors, (4) presentation and workup, (5) treatment decision-making, and (6) postoperative care. It is our hope the current review provides a concise summary for how to diagnose and treat challenging cervical nonunions.

Autologous Stem Cells in Cervical Spine Fusion

STUDY DESIGN

Systematic review.

OBJECTIVES

To systematically review, critically appraise and synthesize evidence on use of stem cells from autologous stem cells from bone marrow aspirate, adipose, or any other autologous sources for fusion in the cervical spine compared with other graft materials.

METHODS

A systematic search of PubMed/MEDLINE was conducted for literature published through October 31, 2018 and through February 20, 2020 for EMBASE and ClinicalTrials.gov comparing autologous cell sources for cervical spine fusion to other graft options.

RESULTS

From 36 potentially relevant citations identified, 10 studies on cervical fusion met the inclusion criteria set a priori. Two retrospective cohort studies, one comparing cancellous bone marrow (CBM) versus hydroxyapatite (HA) and the other bone marrow aspirate (BMA) combined with autograft and HA versus autograft and HA alone, were identified. No statistical differences were seen between groups in either study for improvement in function, symptoms, or fusion; however, in the study evaluating BMA, the authors reported a statistically greater fusion rate and probability of fusion over time in the BMA versus the non-BMA group. Across case series evaluating BMA, authors reported improved function and pain and fusion ranged from 84% to 100% across the studies. In general, complications were poorly reported.

CONCLUSIONS

The overall quality (strength) of evidence of effectiveness and safety of autologous BMA for cervical arthrodesis in the current available literature was very low. Based on currently available data, firm conclusions regarding the effectiveness or safety of BMA in cervical fusions cannot be made.

Reoperation for Symptomatic Nonunions in Atlantoaxial (C1-C2) Fusions with and without Bone Morphogenetic Protein: A Cohort of 108 Patients with >2 Years Follow-Up

OBJECTIVE

To determine if there is a difference in reoperation rates for symptomatic nonunions in atlantoaxial (C1-C2) fusions with or without bone morphogenetic protein (BMP) using data from a national spine registry and to analyze the different types of bone grafts used in the non-BMP group.

METHODS

Data from the Kaiser Permanente spine registry were used to identify patients with C1-C2 fusions with >2 years follow-up. Patient characteristics, diagnosis, operative times, length of stay, and reoperations were extracted from the registry. The data set was divided into patients with and without BMP. Further analysis was made of the different types of non-BMP grafts as well as the instrumentation used.

RESULTS

In our cohort, we found 58 patients (53.7%) with BMP and 50 patients (46.3%) without with an average follow-up time of 5 years (interquartile range, 2.04-8.49). The BMP versus non-BMP groups differed in admitting diagnosis, operative times, length of stay, and follow-up times. There were no reoperations for symptomatic nonunions in both groups. The non-BMP group included iliac crest graft (with or without allograft [+/-] allograft); lamina (+/- allograft); and allograft alone.

CONCLUSIONS

Using one of the largest retrospective studies on C1-C2 fusions with and without BMP, we found no difference in reoperation rates for symptomatic nonunions. For the non-BMP group, we found that lamina (+/- allograft) or allograft alone may also be just as effective as iliac crest graft (+/- allograft) in having no reoperations for symptomatic nonunions.

Postoperative Seroma Formation After Posterior Cervical Fusion with Use of RhBMP-2: A Report of Two Cases

CASE

We present 2 cases of postoperative seroma formation following posterior cervical fusion with the use of recombinant human bone morphogenetic protein-2 (rhBMP-2).

CONCLUSION

Although some who advocate for the off-label use of rhBMP-2 in patients undergoing posterior cervical spine fusion believe it to be safe, relatively little has been published regarding complication rates. We believe that rhBMP-2 carries a risk of seroma formation in patients who undergo posterior cervical fusion, which necessitates the use of a postoperative drain. Surgeons should have a low threshold for obtaining postoperative magnetic resonance imaging in a symptomatic patient.

The Posterior Use of BMP-2 in Cervical Deformity Surgery Does Not Result in Increased Early Complications: A Prospective Multicenter Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To describe the rate of short-term complications following the posterior use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in cervical deformity (CD) surgery.

METHODS

CD patients from 2013 to 2015 were enrolled in a prospective, multicenter database. Patients were divided into those receiving rhBMP-2 (BMP) and no rhBMP-2 (NOBMP). The relationship between BMP use, demographic variables surgical variables, radiographic parameters and complications was evaluated.

RESULTS

A total of 100 patients (47 BMP, 53 NOBMP) were included. Follow-up time averaged 7.6 months (range 3-12 months). An average of 13.6mg of BMP was used per person with 1.49 mg per level. Compared with the NOBMP group, patients in the BMP group were older (P = .03). BMP was more commonly used in patients that and had longer prior fusions (6.0 vs 2.5, P < .01). There were no differences between groups with regards to a history of surgery, Charlson Comorbidity Index, estimated blood loss, operation time, fusion levels, and surgical approach. The maintenance of radiographic parameters at 6-month follow-up was similar. There were no differences in terms of total complication incidence, total complications per person, major complications per person or any specific complication. Linear regression and Pearson correlation analysis did not reveal any strong r² values (r² = 0.09, 0.08, 0.06) between the use of BMP and complications (major or operative).

CONCLUSIONS

BMP use was not directly associated with an increased incidence of early complications in this prospective cohort of operative adult CD patients. Its use was associated with increased number of levels instrumented and fused.

Complications Related to the Recombinant Human Bone Morphogenetic Protein 2 Use in Posterior Cervical Fusion

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To compare the complications between posterior cervical fusions with and without recombinant human bone morphogenetic protein 2 (rhBMP2).

SUMMARY OF BACKGROUND DATA

Use of rhBMP2 in anterior cervical spinal fusion procedures can lead to potential complications such as neck edema, resulting in airway complications or neurological compression. However, there are no data on the complications associated with the "off-label" use of rhBMP2 in upper and lower posterior cervical fusion approaches.

MATERIALS AND METHODS

Patients from the PearlDiver database who had a posterior cervical fusion between 2005 and 2011 were identified. We evaluated complications within 90 days after fusion and data was divided in 2 groups: (1) posterior cervical fusion including upper cervical spine O-C2 (upper group) and (2) posterior cervical fusion including lower cervical spine C3-C7 (lower group). Complications were divided into: any complication, neck-related complications, wound-related complications, and other complications.

RESULTS

Of the 352 patients in the upper group, 73 patients (20.7%) received rhBMP2, and 279 patients (79.3%) did not. Likewise, in the lower group of 2372 patients, 378 patients (15.9%) had surgery with rhBMP2 and 1994 patients (84.1%) without. In the upper group, complications were observed in 7 patients (9.6%) with and 34 patients (12%) without rhBMP2. In the lower group, complications were observed in 42 patients (11%) with and 276 patients (14%) without rhBMP2. Furthermore, in the lower group the wound-related complications were significantly higher in the rhBMP2 group (23 patients, 6.1%) compared with the non-rhBMP2 group (75 patients, 3.8%).

CONCLUSIONS

Our data showed that the use of rhBMP2 does not increase the risk of complications in upper cervical spine fusion procedures. However, in the lower cervical spine, rhBMP2 may elevate the risk of wound-related complications. Overall, there were no major complications associated with the use of rhBMP2 for posterior cervical fusion approaches.

LEVEL OF EVIDENCE

Level III.

A doxycycline inducible, adenoviral bone morphogenetic protein-2 gene delivery system to bone

We report the novel use of a tuneable, non-integrating viral gene delivery system to bone that can be combined with clinically approved biomaterials in an 'off-the-shelf' manner. Specifically, a doxycycline inducible Tet-on adenoviral vector (AdTetBMP-2) in combination with mesenchymal stromal cells (MSCs), fibrin and a biphasic calcium phosphate ceramic (MBCP®) was used to repair large bone defects in nude rats. Bone morphogenetic protein-2 (BMP-2) transgene expression could be effectively tuned by modification of the doxycycline concentration. The effect of adenoviral BMP-2 gene delivery upon bone healing was investigated in vivo in 4 mm critically sized, internally fixated, femoral defects. MSCs were transduced either by direct application of AdTetBMP-2 or by pre-coating MBCP granules with the virus. Radiological assessment scores post-mortem were significantly improved upon delivery of AdTetBMP-2. In AdTetBMP-2 groups, histological analysis revealed significantly more newly formed bone at the defect site compared with controls. Newly formed bone was vascularized and fully integrated with nascent tissue and implanted biomaterial. Improvement in healing outcome was achieved using both methods of vector delivery (direct application vs. pre-coating MCBP). Adenoviral delivery of BMP-2 enhanced bone regeneration achieved by the transplantation of MSCs, fibrin and MBCP in vivo. Importantly, our in vitro and in vivo data suggest that this can be achieved with relatively low (ng/ml) levels of the growth factor. Our model and novel gene delivery system may provide a powerful standardized tool for the optimization of growth factor delivery and release for the healing of large bone defects. Copyright © 2016 John Wiley & Sons, Ltd.

Bone substitutes and expanders in Spine Surgery: A review of their fusion efficacies

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

This manuscript intends to provide a review of clinically relevant bone substitutes and bone expanders for spinal surgery in terms of efficacy and associated clinical outcomes, as reported in contemporary spine literature.

SUMMARY OF BACKGROUND DATA

Ever since the introduction of allograft as a substitute for autologous bone in spinal surgery, a sea of literature has surfaced, evaluating both established and newly emerging fusion alternatives. An understanding of the available fusion options and an organized evidence-based approach to their use in spine surgery is essential for achieving optimal results.

METHODS

A Medline search of English language literature published through March 2016 discussing bone graft substitutes and fusion extenders was performed. All clinical studies reporting radiological and/or patient outcomes following the use of bone substitutes were reviewed under the broad categories of Allografts, Demineralized Bone Matrices (DBM), Ceramics, Bone Morphogenic proteins (BMPs), Autologous growth factors (AGFs), Stem cell products and Synthetic Peptides. These were further grouped depending on their application in lumbar and cervical spine surgeries, deformity correction or other miscellaneous procedures viz. trauma, infection or tumors; wherever data was forthcoming. Studies in animal populations and experimental in vitro studies were excluded. Primary endpoints were radiological fusion rates and successful clinical outcomes.

RESULTS

A total of 181 clinical studies were found suitable to be included in the review. More than a third of the published articles (62 studies, 34.25%) focused on BMP. Ceramics (40 studies) and Allografts (39 studies) were the other two highly published groups of bone substitutes. Highest radiographic fusion rates were observed with BMPs, followed by allograft and DBM. There were no significant differences in the reported clinical outcomes across all classes of bone substitutes.

CONCLUSIONS

There is a clear publication bias in the literature, mostly favoring BMP. Based on the available data, BMP is however associated with the highest radiographic fusion rate. Allograft is also very well corroborated in the literature. The use of DBM as a bone expander to augment autograft is supported, especially in the lumbar spine. Ceramics are also utilized as bone graft extenders and results are generally supportive, although limited. The use of autologous growth factors is not substantiated at this time. Cell matrix or stem cell-based products and the synthetic peptides have inadequate data. More comparative studies are needed to evaluate the efficacy of bone graft substitutes overall.

Reoperation rates for symptomatic nonunions in posterior cervicothoracic fusions with and without bone morphogenetic protein in a cohort of 450 patients

OBJECTIVE

Fusions across the cervicothoracic junction have been challenging because of the large biomechanical forces exerted resulting in frequent reoperations for nonunions. The objective of this study was to investigate a retrospective cohort using chart review of posterior cervicothoracic spine fusions with and without bone morphogenetic protein (BMP) and to determine the reoperation rates for symptomatic nonunions in both groups.

METHODS

Between January 2009 and September 2013, posterior cervicothoracic spine fusion cases were identified from a large spine registry (Kaiser Permanente). Demographics, diagnoses, operative times, lengths of stay, and reoperations were extracted from the registry. Reoperations for symptomatic nonunions were adjudicated via chart review. Logistic regression was used to estimate odds ratios and 95% confidence intervals. Kaplan-Meier curves for the non-BMP and BMP groups were generated and compared using the log-rank test.

RESULTS

In this cohort there were 450 patients (32.7% with BMP) with a median follow-up of 1.4 years (interquartile range [IQR] 0.5–2.7 years). Kaplan-Meier curves showed no significant difference in reoperation rates for nonunions using the log-rank test (p = 0.088). In a subset of patients with more than 1 year of follow-up, 260 patients were identified (43.1% with BMP) with a median follow-up duration of 2.4 years (IQR 1.6–3.3 years). There was no statistically significant difference in the symptomatic operative nonunion rates for posterior cervicothoracic fusions with and without BMP (0.0% vs 2.7%, respectively; p = 0.137) for more than 1 year of follow-up.

CONCLUSIONS

This study presents the largest series of patients using BMP in posterior cervicothoracic spine fusions. Reoperation rates for symptomatic nonunions with more than 1 year of follow-up were 0% with BMP and 2.7% without BMP. No statistically significant difference in the reoperation rates for symptomatic nonunions with or without BMP was found.

Reoperation rates for symptomatic nonunions in posterior cervical (subaxial) fusions with and without bone morphogenetic protein in a cohort of 1158 patients

OBJECTIVE

Bone morphogenetic protein (BMP) was first approved in 2002 for use in single-level anterior lumbar fusions as an alternative to iliac crest grafts. Subsequent studies have concluded that BMP provides superior fusions rates and therefore reduces reoperations for nonunions. The purpose of this study was to determine the reoperation rates for symptomatic nonunions in posterior cervical (subaxial) spinal fusions with and without the use of BMP and to determine if the nonunion rates are statistically significantly different between the two groups.

METHODS

Between January 2009 and September 2013, the authors identified 1158 posterior cervical spinal fusion cases in the subaxial spine (C2–7) from a large spine registry (Kaiser Permanente). Patient characteristics, diagnoses, operative times, lengths of stay, and reoperations were extracted from the registry. Reoperations for symptomatic nonunions were adjudicated via chart review. Logistic regression was conducted to produce estimates of odds ratios (OR) and 95% confidence intervals (CIs). Kaplan-Meier curves for the non-BMP and BMP groups were generated and compared using the log-rank test.

RESULTS

In this cohort there were 1158 patients (19.3% with BMP) with a median follow up of 1.7 years (interquartile range [IQR] 0.7–2.9 years) and median duration to operative nonunion of 0.63 years (IQR 0.44–1.57 years). Kaplan-Meier curves showed no significant difference in reoperation rates for nonunions using the log-rank test (p = 0.179). In a subset of patients with more than 1 year of follow-up, 788 patients were identified (22.5% with BMP) with a median follow-up duration of 2.5 years (IQR 1.7–3.4 years) and a median time to operative nonunion of 0.73 years (IQR 0.44–1.57 years). There was no statistically significant difference in the symptomatic operative nonunion rates for posterior cervical (subaxial) fusions with BMP compared with non-BMP (1.1% vs 0.7%; crude OR 1.73, 95% CI 0.32–9.55, p = 0.527) for more than 1 year of follow-up.

CONCLUSIONS

This study presents the largest series of patients using BMP in posterior cervical (subaxial) spinal fusions. Reoperation rates for symptomatic nonunions with more than 1 year of follow-up were found to be 1.1% with BMP and 0.7% without BMP. There was no significant difference in the reoperation rates for symptomatic nonunions with or without BMP.

Exploratory meta-analysis on dose-related efficacy and morbidity of bone morphogenetic protein in spinal arthrodesis surgery

OBJECT

Bone morphogenetic protein (BMP) is frequently used for spinal arthrodesis procedures in an "off-label" fashion. Whereas complications related to BMP usage are well recognized, the role of dosage is less clear. The objective of this meta-analysis was to assess dose-dependent effectiveness (i.e., bone fusion) and morbidity of BMP used in common spinal arthrodesis procedures. A quantitative exploratory meta-analysis was conducted on studies reporting fusion and complication rates following anterior cervical discectomy and fusion (ACDF), posterior cervical fusion (PCF), anterior lumbar interbody fusion (ALIF), transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), and posterolateral lumbar fusion (PLF) supplemented with BMP.

METHODS

A literature search was performed to identify studies on BMP in spinal fusion procedures reporting fusion and/or complication rates. From the included studies, a database for each spinal fusion procedure, including patient demographic information, dose of BMP per level, and data regarding fusion rate and complication rates, was created. The incidence of fusion and complication rates was calculated and analyzed as a function of BMP dose. The methodological quality of all included studies was assessed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Data were analyzed using a random-effects model. Event rates are shown as percentages, with a 95% CI.

RESULTS

Forty-eight articles met the inclusion criteria: ACDF (n = 7), PCF (n = 6), ALIF (n = 9), TLIF/PLIF (n = 17), and PLF (n = 9), resulting in a total of 5890 patients. In ACDF, the lowest BMP concentration analyzed (0.2-0.6 mg/level) resulted in a fusion rate similar to the highest dose (1.1-2.1 mg/level), while permitting complication rates comparable to ACDF performed without BMP. The addition of BMP to multilevel constructs significantly (p < 0.001) increased the fusion rate (98.4% [CI 95.4%-99.4%]) versus the control group fusion rate (85.8% [CI 77.4%-91.4%]). Studies on PCF were of poor quality and suggest that BMP doses of ≤ 2.1 mg/level resulted in similar fusion rates as higher doses. Use of BMP in ALIF increased fusion rates from 79.1% (CI 57.6%-91.3%) in the control cohort to 96.9% (CI 92.3%-98.8%) in the BMP-treated group (p < 0.01). The rate of complications showed a positive correlation with the BMP dose used. Use of BMP in TLIF had only a minimal impact on fusion rates (95.0% [CI 92.8%-96.5%] vs 93.0% [CI 78.1%-98.0%] in control patients). In PLF, use of ≥ 8.5 mg BMP per level led to a significant increase of fusion rate (95.2%; CI 90.1%-97.8%) compared with the control group (75.3%; CI 64.1%-84.0%, p < 0.001). BMP did not alter the rate of complications when used in PLF.

CONCLUSIONS

The BMP doses used for various spinal arthrodesis procedures differed greatly between studies. This study provides BMP dosing recommendations for the most common spine procedures.

Ultra-low-dose recombinant human bone morphogenetic protein-2 for 3-level anterior cervical diskectomy and fusion

This study evaluated the safety of 3-level anterior cervical diskectomy and fusion (ACDF) with ultra-low-dose recombinant bone morphogenetic protein-2 (rhBMP-2). Thirty-seven consecutive patients with cervical spondylotic myelopathy who were treated with 3-level ACDF and rhBMP-2 were evaluated. Complications such as airway or cervical swelling or hematoma were not observed. The rate of dysphagia was no different at 1, 2, and 6 months postoperatively compared with reports in the literature without rhBMP-2. There were significant improvements in VAS neck/arm pain, Oswestry Neck Disability Index, and cervical lordosis. The use of ultra-low-dose rhBMP-2 for 3-level ACDF may be efficacious for surgically addressing 3-level spondylotic myelopathy.

Does bone morphogenetic protein change the operative nonunion rates in spine fusions?

STUDY DESIGN

A retrospective cohort study with medical record review.

OBJECTIVE

To determine if there is difference in the operative nonunion rates with and without the use of bone morphogenetic protein (BMP) after spinal fusions by analyzing data from an integrated health care system's spine registry.

SUMMARY OF BACKGROUND DATA

BMP was first approved in 2002 for use in single-level anterior lumbar fusions. Follow-up studies have advocated its use in reducing the need for reoperations for nonunions. Recent studies, however, have questioned these conclusions and the usefulness of BMP in spinal fusions has been highly debated.

METHODS

We identified 9425 spinal fusion cases between 2009 and 2011 from a spine registry in a large integrated health care organization. Patient characteristics, diagnosis, operative times, length of stay, and reoperations were extracted from the registry. Reoperations for nonunions were adjudicated via medical record review. Cox regression models were used to evaluate the risk of reoperation while adjusting for confounders.

RESULTS

In our cohort, there were 5456 BMP cases and 3969 non-BMP cases. The mean age was 60.4 years (standard deviation: 12.9 yr), with the majority being females (53%). The median follow-up time was 1.2 years (interquartile range: 0.6-2.0 yr). Reoperation rates for BMP versus non-BMP nonunions for all fusion cases with follow-up of 1 year or more (1.9% vs. 2.2%) and follow-up of 2 years or more (2.3% vs. 2.6%) were not statistically significantly different. Operative nonunion rates did not reach statistical significance for different spine regions and for different fused columns (anterior only, posterior only, or combined). After controlling for differences in patient characteristics, operative times, levels fused, and spinal regions, the risk of reoperation in the BMP versus non-BMP groups was 0.67 (95% CI: 0.42-1.06).

CONCLUSION

In this large cohort of spinal fusions at all spine regions involving all fused columns with and without BMP, we found no statistically significant difference in operative nonunion rates.

LEVEL OF EVIDENCE

3.

Inkjet-based biopatterning of SDF-1β augments BMP-2-induced repair of critical size calvarial bone defects in mice

BACKGROUND

A major problem in craniofacial surgery is non-healing bone defects. Autologous reconstruction remains the standard of care for these cases. Bone morphogenetic protein-2 (BMP-2) therapy has proven its clinical utility, although non-targeted adverse events occur due to the high milligram-level doses used. Ongoing efforts explore the use of different growth factors, cytokines, or chemokines, as well as co-therapy to augment healing.

METHODS

Here we utilize inkjet-based biopatterning to load acellular DermaMatrix delivery matrices with nanogram-level doses of BMP-2, stromal cell-derived factor-1β (SDF-1β), transforming growth factor-β1 (TGF-β1), or co-therapies thereof. We tested the hypothesis that bioprinted SDF-1β co-delivery enhances BMP-2 and TGF-β1-driven osteogenesis both in-vitro and in-vivo using a mouse calvarial critical size defect (CSD) model.

RESULTS

Our data showed that BMP-2 bioprinted in low-doses induced significant new bone formation by four weeks post-operation. TGF-β1 was less effective compared to BMP-2, and SDF-1β therapy did not enhance osteogenesis above control levels. However, co-delivery of BMP-2+SDF-1β was shown to augment BMP-2-induced bone formation compared to BMP-2 alone. In contrast, co-delivery of TGF-β1+SDF-1β decreased bone healing compared to TGF-β1 alone. This was further confirmed in vitro by osteogenic differentiation studies using MC3T3-E1 pre-osteoblasts.

CONCLUSIONS

Our data indicates that sustained release delivery of a low-dose growth factor therapy using biopatterning technology can aid in healing CSD injuries. SDF-1β augments the ability for BMP-2 to drive healing, a result confirmed in vivo and in vitro; however, because SDF-1β is detrimental to TGF-β1-driven osteogenesis, its effect on osteogenesis is not universal.

A consensus statement regarding the utilization of BMP in spine surgery

Recombinant human bone morphogenetic protein - 2 (rh-BMP-2) was first approved by the United States Food and Drug Administration (FDA) in 2002 for use in anterior lumbar interbody fusions. Since that time, it has been estimated that "off label" use accounts for 85 % of applications. Original, industry sponsored studies demonstrated superior fusion rates with decreased incidence of complications when compared with traditional iliac crest bone graft. These studies have been criticized for potential bias and newer research has detailed potential complications as well as alternative applications. Potential off label uses of rhBMP-2 include: anterior lumbar fusions, single level posterior lumbar fusions, multiple level posterior lumbar fusions, posterior cervical fusions, long deformity fusions, in the presence of vertebral osteomyelitis, and in patients with history of malignancy. A review of the literature related to rhBMP-2 was conducted to evaluate its use for the above-mentioned applications with a special focus on fusion rates, observed complications, and clinical or radiographic outcomes.

Complications of spinal fusion with utilization of bone morphogenetic protein: a systematic review of the literature

STUDY DESIGN

Systematic review.

OBJECTIVE

A systematic review was performed to identify the types of complications and complication rates associated with the use of bone morphogenetic protein (BMP) in both anterior and posterior cervical and lumbar spine surgery.

SUMMARY OF BACKGROUND DATA

There has been an increase in BMP use in various clinical situations typically in an "off-label" fashion. Associated with its use, however, have been reports of various complications.

METHODS

A MEDLINE search was conducted. All articles involving complications after spine surgery in patients receiving BMP were included. Articles were excluded on the basis of the following criteria: Non-English manuscripts and nonhuman subjects. A total of 29 articles met the inclusion and exclusion criteria and were used in the analysis. For each complication identified, the incidence was calculated by pooling the subjects from the studies that reported the complication. χ tests were used to compare the incidence rates between those that had received BMP and the control groups.

RESULTS

Of the 29 articles included, 7 reported complication rates in anterior cervical fusions, 3 in posterior cervical fusions, 4 in anterior lumbar interbody fusions (ALIF), 9 in posterior/transforaminal lumbar interbody fusions (PLIF/TLIF), and 6 in posterolateral lumbar fusions. Individual complication rates when BMP was used was in the range from 0.66% to 20.1% in anterior cervical fusions, 3.5% to 14.6% in posterior cervical fusions, 2.0% to 7.3% in ALIFs, 1.5% to 21.8% in PLIF/TLIFs, and 1.4% to 8.2% in posterolateral lumbar fusions. Pseudarthrosis rates were statistically significantly lower with the utilization of BMP in all procedures except for PLIF/TLIFs, which only approached significance (P = 0.07). The only individual complication that was statistically significantly greater with BMP utilization was retrograde ejaculation in ALIFs (7.3 vs. 2.3%; P = 0.03). The rate of dysphagia/swelling in anterior cervical fusions was greater with BMP (20.1 vs. 15.6%), however this only approached statistical significance (P = 0.07).

CONCLUSION

The body of literature reports complication rates with BMP ranging from 0.66% to 21.8%. However, the only statistically significant adverse complication rate was retrograde ejaculation in the ALIF population (7.3%). Despite the increased awareness of complications associated with BMP, complication rates remain spine site specific and low. Thorough patient education should be done with the physician to make an informative use regarding BMP utilization in spinal surgery.

LEVEL OF EVIDENCE

3.

Cervical corpectomy with ultra-low-dose rhBMP-2 in high-risk patients: 5-year outcomes

Twenty-four consecutive patients with cervical spondylosis who were treated with cervical corpectomy and recombinant human bone morphogenetic protein-2 (rhBMP-2) with standalone anterior instrumentation were evaluated. Mean number of levels fused was 2.4. There were significant improvements in visual analog scale neck pain and Oswestry Disability Index scores and cervical lordosis. Cervical corpectomy with a lower dose of rhBMP-2 was found to be safe and efficacious for patients who are at a higher risk for pseudarthrosis.

Hospital outcomes and complications of anterior and posterior cervical fusion with bone morphogenetic protein

STUDY DESIGN

Retrospective database analysis.

OBJECTIVE

A nationwide population-based database was analyzed to identify the incidence of complications and mortality associated with bone morphogenetic protein (BMP) utilization in cervical spine fusion surgery.

SUMMARY OF BACKGROUND DATA

"Off-label" use of BMP as an adjunct in cervical fusions has been associated with increased complication rates in small case series. The incidence of complications with utilization of BMP is not well characterized on a national level.

METHODS

Data from the Nationwide Inpatient Sample were obtained for each year from 2002-2009. Patients undergoing anterior cervical fusion (ACF) or posterior cervical fusion for diagnoses of cervical myelopathy and/or radiculopathy were identified and separated into cohorts ("BMP" and "No BMP"). Patient demographics and comorbidities were compared. Complications, length of stay, costs, and mortality rates were assessed. Student t test and χ test were used to assess significant differences. A P value of less than 0.0005 was used to denote significance.

RESULTS

A total of 213,421 ACFs and 20,334 posterior cervical fusions were identified from 2002-2009; 6.2% of all ACFs and 12.5% of posterior cervical fusions utilized BMP. Patients receiving BMP in the ACF group were older with greater comorbidities than patients who did not receive BMP (P < 0.0005). Both surgical groups with BMP experienced increased length of stay and costs. Overall complication rates were significantly greater when BMP was utilized in ACFs (P < 0.0005) due to a significantly higher rate of dysphagia (37.2 vs. 22.5 per 1000 cases) (P < 0.0005).

CONCLUSION

Our study found that "off-label" use of BMP as an adjunct to cervical fusions was associated with increased rates of dysphagia in ACFs and increased costs for all cervical fusions. Our study does not measure long-term outcomes after discharge; however, the impact of increased inhospital costs, length of stay, and incidence of dysphagia with utilization of BMP should be considered prior to its use in cervical fusions.