Prevalence, complications, and hospital charges associated with use of bone-morphogenetic proteins in spinal fusion procedures

The Use of Bone Morphogenetic Protein in the Intervertebral Disk Space in Minimally Invasive Transforaminal Lumbar Interbody Fusion: 10-year Experience in 688 Patients

STUDY DESIGN

Retrospective Cohort.

OBJECTIVE

The objective of this study was to characterize one surgeon's experience over a 10-year period using rhBMP-2 in the disk space for minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).

SUMMARY OF BACKGROUND DATA

MIS TLIF has been utilized as a technique for decreasing patients' immediate postoperative pain, decreasing blood loss, and shortened hospital stays. Effectiveness and complications of rhBMP-2's use in the disk space is limited because of its off-label status.

METHODS

Retrospective analysis of consecutive MIS TLIFs performed by senior author between 2004 and 2014. rhBMP-2 was used in the disk space in all cases. Patients were stratified based on the dose of rhBMP-2 utilized. Patients had 9 to 12 month computerized tomography scan to evaluate for bony fusion and continued follow-up for 18 months.

RESULTS

A total of 688 patients underwent a MIS TLIF. A medium kit of rhBMP-2 was utilized in 97 patients, and small kit was used in 591 patients. Fusion rate was 97.9% and this was not different between the 2 groups with 96/97 patients fusing in the medium kit group and 577/591 patients fusing in the small kit group. Five patients taken back to the operating room for symptomatic pseudoarthrosis, 4 reoperated for bony hyperostosis, and 10 radiographic pseudoarthroses that did not require reoperation. A statistically significant difference in the rate of foraminal hyperostosis was found when using a medium sized kit of rhBMP-2 was 4.12% (4/97 patients), compared with a small kit (0/591 patients, P=0.0004).

CONCLUSIONS

Utilization of rhBMP-2 in an MIS TLIF leads to high fusion rate (97.9%), with an acceptable complication profile. The development of foraminal hyperostosis is a rare complication that only affected 0.6% of patients, and seems to be a dose related complication, as this complication was eliminated when a lower dose of rhBMP-2 was utilized.

LEVEL OF EVIDENCE

Level IV.

Estimating a price point for cost-benefit of bone morphogenetic protein in pseudarthrosis prevention for adult spinal deformity surgery

OBJECTIVE

Bone morphogenetic protein (BMP) is associated with reduced rates of pseudarthrosis and has the potential to decrease the need for revision surgery. There are limited data evaluating the cost-benefit of BMP for pseudarthrosis-related prevention surgery in adult spinal deformity.

METHODS

The authors performed a single-center retrospective review of 200 consecutive patients with adult spinal deformity. Demographic data and costs of BMP, primary surgery, and revision surgery for pseudarthrosis were collected. Patients with less than 12 months of follow-up or with infection, tumor, or neuromuscular disease were excluded.

RESULTS

One hundred fifty-one patients (107 [71%] women) with a mean age of 65 years met the inclusion criteria. The mean number of levels fused was 10; BMP was used in 98 cases (65%), and the mean follow-up was 23 months. Fifteen patients (10%) underwent surgical revision for pseudarthrosis; BMP use was associated with an 11% absolute risk reduction in the rate of reoperation (17% vs 6%, p = 0.033), with a number needed to treat of 9.2. There were no significant differences in age, sex, upper instrumented vertebra, or number of levels fused in patients who received BMP. In a multivariate model including age, sex, number of levels fused, and the upper instrumented vertebra, only BMP (OR 0.250, 95% CI 0.078-0.797; p = 0.019) was associated with revision surgery for pseudarthrosis. The mean direct cost of primary surgery was $87,653 ± $19,879, and the mean direct cost of BMP was $10,444 ± $4607. The mean direct cost of revision surgery was $52,153 ± $26,985. The authors independently varied the efficacy of BMP, cost of BMP, and cost of reoperation by ± 50%; only reductions in the cost of BMP resulted in a cost savings per 100 patients. Using these data, the authors estimated a price point of $5663 in order for BMP to be cost-neutral.

CONCLUSIONS

Use of BMP was associated with a significant reduction in the rates of revision surgery for pseudarthrosis. At its current price, the direct in-hospital costs for BMP exceed the costs associated with revision surgery; however, this likely underestimates the true value of BMP when considering the savings associated with reductions in rehabilitation, therapy, medication, and additional outpatient costs.

Prospective Evaluation of Radiculitis following Bone Morphogenetic Protein-2 Use for Transforaminal Interbody Arthrodesis in Spine Surgery

Study Design

Prospective observational cohort study.

Purpose

This study aims to evaluate the safety and efficacy of bone morphogenetic protein-2 (BMP-2) in transforaminal lumbar interbody fusion (TLIF) with regard to postoperative radiculitis.

Overview of Literature

Bone morphogenetic protein (BMP) is being used increasingly as an alternative to iliac crest autograft in spinal arthrodesis. Recently, the use of BMP in TLIF has been examined, but concerns exist that the placement of BMP close to the nerve roots may cause postoperative radiculitis. Furthermore, prospective studies regarding the use of BMP in TLIF are lacking.

Methods

This prospective study included 77 patients. The use of BMP-2 was determined individually, and demographic and operative characteristics were recorded. Leg pain was assessed using the Visual Analog Scale (VAS) for pain and the Sciatica Bothersome Index (SBI) with several secondary outcome measures. The outcome data were collected at each follow-up visit.

Results

Among the 77 patients, 29 were administered with BMP. Postoperative leg pain significantly improved according to VAS leg and SBI scores for the entire cohort, and no clinically significant differences were observed between the BMP and control groups. The VAS back, Oswestry Disability Index, and Short-Form 36 scores also significantly improved. A significantly increased 6-month fusion rate was noted in the BMP group (82.8% vs. 55.3%), but no significant differences in fusion rate were observed at the 12- and 24-month follow-up. Heterotopic ossification was observed in seven patients: six patients and one patient in the BMP and control groups, respectively (20.7% vs. 2.1%). However, no clinical effect was observed.

Conclusions

In this prospective observational trial, the use of BMP in TLIF did not lead to significant postoperative radiculitis, as measured by VAS leg and SBI scores. Back pain and other functional outcome scores also improved, and no differences existed between the BMP and control groups. The careful use of BMP in TLIF appears to be both safe and effective.

Epidermal growth factor enhances spinal fusion: Posterolateral lumbar fusion model on rats

Objective

The aim of this study was to investigate the effects of human recombinant epidermal growth factor (EGF) on posterolateral lumbar fusion in a rat model.

Methods

36 male Sprague Dawley rats underwent posterolateral fusion at L4-5 level. They were randomly assigned to 3 groups: 1- Sham control group where no local augmentation was made, 2- Local Hydoxyapatite β-tricalcium phosphate (HA/β-TCP) augmentation group and 3- Local HA/β-TCP + EGF augmentation group. Rats were euthanized at 8 weeks post-surgery. 6 rats from each group were selected for manual palpation examination, micro-computed tomography analysis and histologic analysis; and the rest was used for biomechanical analysis.

Results

Based on manual palpation, there was no fusion in the sham control group. Fusion rate was 33.3% in the HA/β-TCP group and 66.7% in the HA/β-TCP + EGF group (p = 0.085). Micro-CT results revealed that new bone formation was higher in the HA/β-TCP + EGF group (BV/TV: 40% vs. 65%) (p = 0.004). Histologically newly formed bone tissue was more pronounced in the EGF group and compacted and bridging bone spicules were observed. The median maximum bending moment values were 0.51 Nmm (0.42–0.59), 0.73 Nmm (0.49–0.88) and 0.91 Nmm (0.66–1.03) in the sham control, HA/β-TCP and HA/β-TCP + EGF groups, respectively (p = 0.013). The median stiffness values were 1.69 N/mm (1.12–2.18), 1.68 N/mm (1.13–2.74) and 3.10 N/mm (1.66–4.40) as in the previous order (p = 0.087).

Conclusion

This study demonstrates that EGF enhances posterolateral lumbar fusion in the rat model. EGF in combination with ceramic grafts increased the fusion rates. Our findings may provide insights to further studies, investigating EGF's clinical usage as an alternative fusion enhancer.

Insights into complication rates, reoperation rates, and healthcare utilization associated with use of recombinant human bone morphogenetic protein–2 in patients with spine infections

OBJECTIVE

Use of recombinant human bone morphogenetic protein–2 (rhBMP-2) in patients with spine infections is controversial. The purpose of this study was to identify long-term complications, reoperations, and healthcare utilization associated with rhBMP-2 use in patients with spine infections.

METHODS

This retrospective study extracted data using ICD-9/10 and CPT codes from MarketScan (2000–2016). Patients were dichotomized into 2 groups (rhBMP-2, no rhBMP-2) based on whether rhBMP-2 was used during fusion surgery for spinal infections. Outcomes of interest were reoperation rates (index level, other levels), readmission rates, discharge disposition, length of stay, complications, and healthcare resource utilization at the index hospitalization and 1, 3, 6, 12, and 24 months following discharge. Outcomes were compared using nonparametric 2-group tests and generalized linear regression models.

RESULTS

The database search identified 2762 patients with > 24 months’ follow-up; rhBMP-2 was used in 8.4% of their cases. The patients’ median age was 53 years, 52.43% were female, and 15.11% had an Elixhauser Comorbidity Index ≥ 3. Patients in the rhBMP-2 group had higher comorbidity indices, incurred higher costs at index hospitalization, were discharged home in most cases, and had lower complication rates than those in the no–rhBMP-2 group. There was no statistically significant between-groups difference in complication rates 1 month following discharge or in reoperation rates at 3, 6, 12, and 24 months following the procedure. Patients in the no–rhBMP-2 group incurred higher utilization of outpatient services and medication refill costs at 1, 3, 6, 12, and 24 months following surgery.

CONCLUSIONS

In patients undergoing surgery for spine infection, rhBMP-2 use was associated with lower complication rates and higher median payments during index hospitalization compared to cases in which rhBMP-2 was not used. There was no significant between-groups difference in reoperation rates (index and other levels) at 3, 6, 12, and 24 months after the index operation. Patients treated with rhBMP-2 incurred lower utilization of outpatient services and overall payments. These results indicate that rhBMP-2 can be used safely in patients with spine infections with cost-effective utilization of healthcare resources and without an increase in complications or reoperation rates.

Spatiotemporal Control Strategies for Bone Formation through Tissue Engineering and Regenerative Medicine Approaches

Global increases in life expectancy drive increasing demands for bone regeneration. The gold standard for surgical bone repair is autografting, which enjoys excellent clinical outcomes; however, it possesses significant drawbacks including donor site morbidity and limited availability. Although collagen sponges delivered with bone morphogenetic protein, type 2 (BMP2) are a common alternative or supplement, they do not efficiently retain BMP2, necessitating extremely high doses to elicit bone formation. Hence, reports of BMP2 complications are rising, including cancer promotion and ectopic bone formation, the latter inducing complications such as breathing difficulties and neurologic impairments. Thus, efforts to exert spatial control over bone formation are increasing. Several tissue engineering approaches have demonstrated the potential for targeted and controlled bone formation. These approaches include biomaterial scaffolds derived from synthetic sources, e.g., calcium phosphates or polymers; natural sources, e.g., bone or seashell; and immobilized biofactors, e.g., BMP2. Although BMP2 is the only protein clinically approved for use in a surgical device, there are several proteins, small molecules, and growth factors that show promise in tissue engineering applications. This review profiles the tissue engineering advances in achieving control over the location and onset of bone formation (spatiotemporal control) toward avoiding the complications associated with BMP2.

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.

Association Between Recombinant Human Bone Morphogenetic Proteins and Postoperative Opioid Use in Lumbar Fusion Procedure Patients: A Propensity Score-Matched Analysis

BACKGROUND

Little is known about the effectiveness of recombinant human bone morphogenetic proteins (rhBMPs) in reducing the demand for opioids after surgery. We investigated the association between rhBMP use and the likelihood of achieving opioid independence and changes in opioid demand in the first postoperative year.

METHODS

Using the Multi-Payer Claims Database from 2007 to 2010, patients aged >20 years who had undergone a degenerative disc disease-indicated lumbar fusion procedure and had had ≥1 opioid prescription in the 3 months before surgery were identified. Propensity score matching (1:1) of rhBMP-exposed and rhBMP-unexposed patients was used to mitigate confounding. The outcomes of interest were opioid independence and decreases in opioid doses in morphine equivalent units, assessed at 3-6 and 9-12 months after the procedure. Logistic regression and analysis of covariance models were used.

RESULTS

The data from 318 patients were analyzed. Most patients were women (61%) and aged <65 years (68%). Few had achieved opioid independence at 3-6 (n = 71; 22.3%) or 9-12 (n = 115; 36.2%) months postoperatively. During the 3-6-month window, the rhBMP group reduced their opioid use rates (estimated mean difference. -28.4 vs. -19.5; P = 0.69) and achieved opioid independence (21.4% vs. 23.3%; odds ratio, 0.92; 95% confidence interval, 0.54-1.56; P = 0.74) at rates that were statistically comparable to their matched comparators. Similar patterns were observed during the 9-12-month window.

CONCLUSION

We found no evidence to suggest that rhBMP use during spinal fusion procedures is associated with either the discontinuation or decrease of opioid analgesic therapy. The continued opioid use after surgery warrants further clinical and research attention.

Variations in 30-day readmissions and length of stay among spine surgeons: a national study of elective spine surgery among US Medicare beneficiaries

OBJECTIVE

Pay-for-performance programs are targeting hospital readmissions. These programs have an underlying assumption that readmissions are due to provider practice patterns that can be modified by a reduction in reimbursement. However, there are limited data to support the role of providers in influencing readmissions. To study this, the authors examined variations in readmission rates by spine surgeon within 30 days among Medicare beneficiaries undergoing elective lumbar spine surgery for degenerative conditions.

METHODS

The authors applied validated ICD-9-CM algorithms to 2003–2007 Medicare data to select beneficiaries undergoing elective inpatient lumbar spine surgery for degenerative conditions. Mixed models, adjusting for patient demographics, comorbidities, and surgery type, were used to estimate risk of 30-day readmission by the surgeon. Length of stay (LOS) was also studied using these same models.

RESULTS

A total of 39,884 beneficiaries were operated on by 3987 spine surgeons. The mean readmission rate was 7.2%. The mean LOS was 3.1 days. After adjusting for patient characteristics and surgery type, 1 surgeon had readmission rates significantly below the mean, and only 5 surgeons had readmission rates significantly above the mean. In contrast, for LOS, the patients of 288 surgeons (7.2%) had LOS significantly lower than the mean, and the patients of 397 surgeons (10.0%) had LOS significantly above the mean. These findings were robust to adjustments for surgeon characteristics and clustering by hospital. Similarly, hospital characteristics were not significantly associated with readmission rates, but LOS was associated with hospital for-profit status and size.

CONCLUSIONS

The authors found almost no variations in readmission rates by surgeon. These findings suggest that surgeon practice patterns do not affect the risk of readmission. Likewise, no significant variation in readmission rates by hospital characteristics were found. Strategies to reduce readmissions would be better targeted at factors other than providers.

Treatment of ruptured and unruptured cerebral aneurysms in the USA: a paradigm shift

Background

Integration of data from clinical trials and advancements in technology predict a change in selection for treatment of patients with cerebral aneurysm.

Objective

To describe patterns of use and in-hospital mortality associated with surgical and endovascular treatments of cerebral aneurysms over the past decade.

Materials and methods

The data are 34 899 hospital discharges with a diagnosis of ruptured or unruptured cerebral aneurysm from 1998 to 2007 identified from the Nationwide Inpatient Sample (NIS). The rates of endovascular coiling and surgical clipping and in-hospital mortality among patients with an aneurysm are examined over a decade by hospital and patient demographic characteristics.

Results

From 1998 to 2007, 20 134 discharges with a ruptured aneurysm and 14 765 discharges with an unruptured aneurysm were identified. Over this decade, the number of patients discharged with a ruptured aneurysm was stable while the number discharged with an unruptured aneurysm increased significantly. The use of endovascular coiling increased at least twofold for both groups of patient (p<0.001) with the majority of unruptured aneurysms treated with coiling by 2007. Although whites were more likely than non-whites to undergo coiling versus clipping for a ruptured aneurysm (OR=1.30; 95% CI 1.13 to 1.48) and men with unruptured aneurysms were more likely than women to undergo coiling (OR=1.26; 95% CI 1.13 to 1.40), by 2007 differences in treatment selection by gender and racial subgroups were decreased or statistically non-significant. Over time the use of coiling spread from primarily large, teaching hospitals to smaller, non-teaching hospitals.

Conclusions

The majority of unruptured aneurysms in the USA are now treated with endovascular coiling. Although surgical clipping is used for treatment of most ruptured aneurysms, its use is decreasing over time. Dissemination of endovascular procedures appears widespread across patient and hospital subgroups.

The Effects of Age and Dose on Gene Expression and Segmental Bone Defect Repair After BMP-2 Delivery

Age is a well‐known influential factor in bone healing, with younger patients generally healing bone fractures more rapidly and suffering fewer complications compared with older patients. Yet the impact age has on the response to current bone healing treatments, such as delivery of bone morphogenetic protein 2 (BMP‐2), remains poorly characterized. It remains unclear how or if therapeutic dosing of BMP‐2 should be modified to account for age‐related differences in order to minimize potential adverse effects and consequently improve patient bone‐healing outcomes. For this study, we sought to address this issue by using a preclinical critically sized segmental bone defect model in rats to investigate age‐related differences in bone repair after delivery of BMP‐2 in a collagen sponge, the current clinical standard. Femoral defects were created in young (7‐week‐old) and adult (8‐month‐old) rats, and healing was assessed using gene expression analyses, longitudinal radiography, ex vivo micro‐computed tomography (µCT), as well as torsional testing. We found that young rats demonstrated elevated expression of genes related to osteogenesis, chondrogenesis, and matrix remodeling at the early 1‐week time point compared with adult rats. These early gene expression differences may have impacted long‐term healing as the regenerated bones of young rats exhibited higher bone mineral densities compared with those of adult rats after 12 weeks. Furthermore, the young rats demonstrated significantly more bone formation and increased mechanical strength when BMP‐2 dose was increased from 1 µg to 10 µg, a finding not observed in adult rats. Overall, these results indicate there are age‐related differences in BMP‐2‐mediated bone regeneration, including relative dose sensitivity, suggesting that age is an important consideration when implementing a BMP‐2 treatment strategy. © 2018 The Authors JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Insights Into Oropharyngeal Dysphagia From Administrative Data and Clinical Registries: A Literature Review

Purpose

The call for data-driven health care has been bolstered by the digitization of medical records, quality initiatives, and payment reform. Administrative databases and clinical registries are increasingly being used to study oropharyngeal dysphagia and to facilitate data-driven decision making. The objective of this work was to summarize key findings, etiologies studied, data sources used, study objectives, and quality of evidence of all original research articles that have investigated oropharyngeal dysphagia or aspiration pneumonia using administrative or clinical registry data to date.

Method

A literature search was completed in MEDLINE, Scopus, and Google Scholar (January 1, 1990, to February 1, 2017). Each study that met inclusion criteria was rated for quality of evidence on a 5-point scale.

Results

Eighty-four research articles were included in the final analysis (n = 221-1,649,871). Over the past 20 years, the number of new publications in this area has quintupled. Most of the administrative database and clinical registry studies of dysphagia have been retrospective cohort studies and cross-sectional studies and limited to quality of evidence levels of 3-4. In these studies, much has been learned about risk factors for dysphagia and pneumonia in defined populations and health care costs and usage. Little has been gleaned from these studies regarding swallowing physiology or dysphagia management.

Conclusions

Investigators are just beginning to develop the methods to study oropharyngeal dysphagia using administrative data and clinical registries. Future research is needed in all areas, from the fundamental issue of how to identify individuals with dysphagia with high sensitivity in these data sets to evaluating treatment effectiveness.

Supplemental Material

https://doi.org/10.23641/asha.6066515.

The Influence of Geography, Time, and Payer Type on the Utilization of Bone Morphogenetic Protein (BMP) Between 2005 and 2015

Bone morphogenetic protein (BMP) is a critical compound for endochondral bone formation and is used as a bone graft substitute to promote spinal fusion and fracture healing. We sought to identify rate, type, and applications of use of BMP in spinal fusion surgery during 2005 to 2015. The Medicare 5% national sample (SAF5) database and the Humana Orthopaedics database (HORTHO) were searched for patients who underwent spinal fusion with BMP. Rate of use over time and influence of geographic region and payer type on utilization of BMP during 2005 to 2015 were analyzed. A total of 9879 and 12,598 patients were treated with BMP within the SAF5 database and HORTHO databases, respectively. There was a statistically significant variation in use of BMP among geographic regions. Rate of BMP usage for patients above 65 years old was 11.02 and 58.91 patients per 100,000 members for SAF5 and HORTHO databases, respectively (P<0.001). Rate of use of BMP did not vary significantly during 2005 to 2012 within the SAF5 database (P=0.153). There was a trend toward lower use of BMP in the HORTHO database between 2007 and 2015 (P=0.081). BMP use was higher for private pay than Medicare.

Tissue Engineered Bone Differentiated From Human Adipose Derived Stem Cells Inhibit Posterolateral Fusion in an Athymic Rat Model

STUDY DESIGN

Biological augmentation spinal arthrodesis trial in athymic rats.

OBJECTIVE

To assess the efficacy of tissue-engineered bone to promote L4-L5 intertransverse process fusion in an athymic rat model.

SUMMARY OF BACKGROUND DATA

Each year in the United States, over 400,000 spinal fusion surgeries are performed requiring bone graft. The current gold standard for posterolateral lumbar fusion is autogenous iliac crest bone graft (ICBG), but the harvesting of ICBG is associated with increased operative time and significant complications. This being the case, an alternative cost-effective bone graft source is needed.

METHODS

Bovine bone cores were sterilized and decellularized for scaffold production. Human adipose derived mesenchymal stem cells (ADSC) were obtained and verified by tridifferentiation testing and seeded onto dried scaffolds. The seeded cores were cultured for 5 weeks in culture medium designed to mimic endochondral ossification and produce hypertrophic chondrocytes. Single-level intertransverse process fusions were performed at the L4-L5 level of 31 athymic rats. Fifteen rats were implanted with the hypertrophic chondrocyte seeded scaffold and 16 had scaffold alone. Half of the study rats were sacrificed at 3 weeks and the other half at 6 weeks. Spinal fusion was assessed using 2D and 3D micro computed tomography (μCT) analysis and tissue histology.

RESULTS

At 3 weeks, none of the tissue engineered rats had partial or complete fusion, whereas 62.5% of the decellularized rats fused and another 12.5% had partial fusions (P = 0.013). At 6 weeks, none of the tissue engineered rats fused and 50% had partial fusions, whereas 87.5% of the decellularized rats fused (P = 0.002).

CONCLUSION

Tissue engineered bone composed of hypertrophic chondrocytes inhibits posterolateral fusion in an athymic rat model and therefore does not represent a promising cost-effective bone graft substitute.

LEVEL OF EVIDENCE

N/A.

Postoperative Complications Associated With rhBMP2 Use in Posterior/Posterolateral Lumbar Fusion

STUDY DESIGN

Retrospective database review.

OBJECTIVE

Posterior/posterolateral lumbar fusion (PLF) is an effective treatment for a variety of spinal disorders; however, variations in surgical technique have different complication profiles. The aim of our study was to quantify the frequency of various complications in patients undergoing PLF with and without human recombinant bone morphogenetic protein 2 (rhBMP2).

METHODS

We queried the orthopedic subset of the Medicare database (PearlDiver) between 2005 and 2011 for patients undergoing PLF procedures with and without rhBMP2. Complication and reoperation rates were analyzed within 1 year of the index procedure. Complications assessed include: acute renal failure, deep vein thrombosis, dural tear, hematoma, heterotopic ossification, incision and drainage, cardiac complications, nervous system complications, osteolysis, pneumonia, pseudarthrosis, pulmonary embolism, radiculopathy, respiratory complications, sepsis, urinary retention, urinary tract infection, mechanical, and wound complications. Chi-square analysis was used to calculate the complication differences between the groups.

RESULTS

Our data revealed higher overall complication rates in patients undergoing PLF with rhBMP2 versus no_rhBMP2 (76.9% vs 68.8%, P < .05). Stratified by gender, rhBMP2 males had higher rates of mechanical complications, pseudarthrosis, and reoperations compared with no_rhBMP2 males (P < .05), whereas rhBMP2 females had higher rates of pseudarthrosis, urinary tract infection, and urinary retention compared with no_rhBMP2 females (P < .05).

CONCLUSION

Our data revealed higher overall complication rates in PLF patients given rhBMP2 compared with no_rhBMP2. Furthermore, our data suggests that rhBMP2-associated complications may be gender specific.

Trends Analysis of rhBMP2 Utilization in Single-Level Anterior Lumbar Interbody Fusion in the United States

STUDY DESIGN

Retrospective case study.

OBJECTIVE

To evaluate the trends and demographics of recombinant human bone morphogenetic protein 2 (rhBMP2) utilization in single-level anterior lumbar interbody fusion (ALIF) in the United States.

METHODS

Patients who underwent single-level ALIF from 2005 to 2011 were identified by searching ICD-9 diagnosis and procedure codes in the PearlDiver Patient Records Database (PearlDiver Technologies, Fort Wayne, IN), a national database of orthopedic insurance records. The year of procedure, age, gender, and region of the United States were analyzed for each patient.

RESULTS

A total of 921 patients were identified who underwent a single-level ALIF in this study. The average rate of single-level ALIF with rhBMP2 utilization increased (35%-48%) from 2005 to 2009, but sharply decreased to 16.7% in 2010 and 15.0% in 2011. The overall incidence of single-level ALIF without rhBMP2 (0.20 cases per 100 000 patients) was more than twice of the incidence of single-level ALIF with rhBMP2 (0.09 cases per 100 000 patients). The average rate of single-level ALIF with rhBMP2 utilization is highest in West (41.4%), followed by Midwest (33.3%), South (26.5%) and Northeast (22.2%). The highest incidence of single-level ALIF with rhBMP2 was observed in the group aged less than 65 years (compared with any other age groups, P < .001), with an incidence of 0.21 per 100 000 patients.

CONCLUSIONS

The incidence of rhBMP2 utilization in single-level ALIF increased from 2006 to 2009, but decreased in 2010 and 2011. The Northeast region had the lowest incidence of rhBMP2 utilization. The group aged less than 65 years trended to have the higher incidence of single-level ALIF with rhBMP2 utilization.

BMP and Beyond: A 25-Year Historical Review of Translational Spine Research at Emory University

A high rate of symptomatic spinal pseudoarthrosis and a wide range of complications associated with the use of iliac crest bone graft (the gold standard) have prompted the spine surgery community to seek alternative options to promote spinal fusion. Emory University has been one of the global leaders in this endeavor. This invited review covers the last 25 years of Emory's contributions to translational spine research, focusing specifically on our work with bone morphogenetic proteins (BMP) and the BMP signaling pathway. As a result of this work, recombinant human BMP-2 is the only Food and Drug Administration approved biologic bone graft substitute. It has been shown to significantly increase spinal fusion rates across the spinal column because of its potent ability to stimulate local bone formation through the recruitment of mesenchymal stem cells. This review covers our development of animal models of spinal fusion, our body of work regarding the translation of BMP from the benchtop to the clinic, the discovery of LMP-1 and strategies to enhance cellular responsiveness to BMPs, and the design of various small molecule drugs that can enhance local bone formation.

Tailored biomimetic hydrogel based on a photopolymerised DMP1/MCF/gelatin hybrid system for calvarial bone regeneration

Searching for effective osteoinduction factors with higher specificity and biosafety for the preparation of biomimetic materials, which mimic the natural bone extracellular matrix (ECM), seems to be an optimum strategy for achieving ideal bone regeneration.

Incidence of Cancer in Spinal Deformity Patients Receiving High-Dose (≥40 mg) Bone Morphogenetic Protein (rhBMP-2)

STUDY DESIGN

Level III, Retrospective observational study.

OBJECTIVE

To determine if there is an increased risk of developing cancer after exposure to high-dose recombinant human bone morphogenetic protein-2 (rhBMP-2) and if risk is dose and/or exposure-dependent.

SUMMARY OF BACKGROUND DATA

Concerns have been raised regarding a relationship between rhBMP-2 and cancer.

METHODS

A total of 642 adult deformity patients from a single institution receiving a cumulative rhBMP-2 dose ≥40 mg from July, 2002 to July, 2009 were identified. Patients with a history of surveillance, epidemiology, and end result (SEER) cancer before rhBMP-2 exposure were excluded. To determine the occurrence of a cancer event, questionnaires were mailed and telephone follow up attempted for nonresponders. Only cancers tracked by the National Cancer Institute (NCI) SEER registry were included. Observed cancer counts were compared to expected cancer counts based on general population incidence rates within 5-year age strata. Cumulative incidence competing risk (CICR) modeling was used to evaluate the association between rhBMP-2 exposure and cancer controlling for potential confounding variables.

RESULTS

Forty-nine patients were lost-to-follow up, leaving 593 patients (92.4%; 138 males/455 females) available for analysis. Mean age was 52.8 years at the time of first exposure. Mean cumulative rhBMP-2 dose was 113.5 mg with 85% having one exposure (range: 1-8). Mean follow-up [date of exposure to date of death (regardless of cause) or returned completed questionnaire] was 5.6 ± 1.9 years; median follow up was 5.4 years. A total of 342 patients have greater than 5-year follow up. Minimum follow up was 2.0 years or until occurrence of a SEER cancer. Our total 8-year cumulative incidence of new SEER cancer accounting for the competing risk of death was 7.4% for 30 cancers in 593 patients. Fewer cancers were observed than expected based on general population rates, though the difference was not statistically significant (expected = 34; standardized incidence ratio = 0.88, 95% confidence interval, CI = 0.60-1.26). CICR found neither cumulative rhBMP-2 dose (hazard ratio, HR = 0.995, 95% CI 0.988-1.003; P = 0.249) nor number of exposures (HR = 0.776, 95% CI 0.359-1.677; P = 0.519) increased the risk of developing a postexposure cancer after controlling for known cancer risk factors.

CONCLUSION

The incidence of a SEER cancer after rhBMP-2 exposure was similar to incidence reported by the NCI. There were no significant rhBMP-2 dose or multi-exposure related risks of developing a life-threatening cancer.

LEVEL OF EVIDENCE

3.

An effective delivery vehicle of demineralized bone matrix incorporated with engineered collagen-binding human bone morphogenetic protein-2 to accelerate spinal fusion at low dose

The aim of this study was to investigate the feasibility and efficacy of a new delivery matrix using demineralized bone matrix (DBM) incorporated with collagen-binding bone morphogenetic protein-2 (CBD-BMP-2) in the rat inter-transverse spinal fusion model. Sixty rats undergoing posterolateral (inter-transverse) spinal fusion were divided into 3 groups according to the fusion materials containing different components (n = 20 per group). Group A were implanted with DBM, Group B with combination of DBM and BMP-2 and Group C with combination of DBM and CBD-BMP-2. After surgery, the spinal fusion of all the rats was assessed by plain radiography, CT + 3D reconstruction, manual palpation and histological evaluation. Significant difference was found in terms of solid fusion rate among the three groups, with 95% in Group C, 65% in Group B and 0% in Group A (P < 0.001). Compared with Groups B and A, new bone formation was observed earlier and was obvious larger, trabecular bone microarchitecture assessment was better and bone mineral density was statistically larger in Group C. In addition, more newly woven bone and osteocytes were shown by histological evaluation in Group C at 4 weeks post-operation. The present study showed CBD domain could help BMP-2 to improve the efficiency of posterolateral spinal fusion. DBM scaffold activated by collagen-binding BMP-2 was a feasible and promising bone repair vehicle. The present study showed better results in terms of plain radiography, CT + 3D reconstruction, manual palpation and histological evaluation in the rat inter-transverse spinal fusion model using DBM+CBD-BMP-2, compared with DBM+BMP-2 and DBM alone, indicating DBM scaffold activated by collagen-binding BMP-2 was a feasible and promising bone repair vehicle.

Stem Cells in Spinal Fusion

STUDY DESIGN

Review of literature.

OBJECTIVES

This review of literature investigates the application of mesenchymal stem cells (MSCs) in spinal fusion, highlights potential uses in the development of bone grafts, and discusses limitations based on both preclinical and clinical models.

METHODS

A review of literature was conducted looking at current studies using stem cells for augmentation of spinal fusion in both animal and human models.

RESULTS

Eleven preclinical studies were found that used various animal models. Average fusion rates across studies were 59.8% for autograft and 73.7% for stem cell-based grafts. Outcomes included manual palpation and stressing of the fusion, radiography, micro-computed tomography (μCT), and histological analysis. Fifteen clinical studies, 7 prospective and 8 retrospective, were found. Fusion rates ranged from 60% to 100%, averaging 87.1% in experimental groups and 87.2% in autograft control groups.

CONCLUSIONS

It appears that there is minimal clinical difference between commercially available stem cells and bone marrow aspirates indicating that MSCs may be a good choice in a patient with poor marrow quality. Overcoming morbidity and limitations of autograft for spinal fusion, remains a significant problem for spinal surgeons and further studies are needed to determine the efficacy of stem cells in augmenting spinal fusion.

Clinical and Radiographic Outcomes in Patients Undergoing Single-level Anterior Cervical Arthrodesis: A Prospective Trial Comparing Allograft to a Reduced Dose of rhBMP-2

STUDY DESIGN

A prospective study with historical controls.

OBJECTIVES

To evaluate and compare the safety and effectiveness of recombinant human bone morphogenetic protein-2 (rhBMP-2) with allograft for anterior cervical discectomy and fusion (ACDF) in patients with symptomatic single-level cervical degenerative disk disease.

SUMMARY OF BACKGROUND DATA

rhBMP-2 is an osteoinductive protein that has been shown to induce fusion when used as an implant with a suitable carrier in spine surgery. However, some previous studies have shown rhBMP-2 use to be associated with a higher complication rate.

METHODS

Investigational patients (224) with single-level cervical degenerative disk disease underwent ACDF with rhBMP-2 at a dose of 0.6 or 1.05 mg and were compared with historical control patients (486) treated with allograft spacer and cervical plate.

RESULTS

At 24 months, improvement was significantly greater in the investigational group (37.1 points) than in the control group for Neck Disability Index (P=0.002) and arm pain (P=0.031). The overall neurological success rate was higher in the investigational group (P<0.001). Neck pain and general health status (SF-36 PCS and MCS) were similar. Fusion rate in the investigational group was higher than in the control group (99.4% vs. 87.2%, P=0.002).Cumulative adverse event rates at 24 months were similar; however, higher rates of dysphagia (P=0.001), local swelling (P=0.024), oropharyngeal pain (P=0.013), neck pain (P=0.019), and foraminal stenosis (P=0.002) were observed in the investigational group. Heterotopic ossification was also higher in the investigational group.

CONCLUSIONS

At doses of 0.6 or 1.05 mg in a PEEK interbody cage, rhBMP-2 was effective in inducing fusion and improving Neck Disability Index and arm pain in single-level ACDF patients; however, higher rates of certain adverse events were observed in the investigational group.

LEVEL OF EVIDENCE

Level 2.

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.

Osteogenic Potential of Tauroursodeoxycholic Acid as an Alternative to rhBMP-2 in a Mouse Spinal Fusion Model

The non-union rate after lumbar spinal fusion is potentially as high as 48%. To support efficient bone regeneration, recombinant human bone morphogenetic protein-2 (rhBMP-2) is commonly used as it is regarded as the most potent bone-inducing molecule. However, recently, there have been increasing concerns on the use of rhBMP-2 such as serious complications, including seroma and heterotopic ossification, and the low quality of bone at the center of fusion mass. Thus, many studies were conducted to find and to develop a potential alternative to rhBMP-2. In this study, we investigated the osteogenic potential of tauroursodeoxycholic acid (TUDCA) in the mouse fusion model and compared its effects with rhBMP-2. Twenty-four mice underwent bilateral posterolateral lumbar spinal fusion bone formation at L4-L5. Collagen sponge infused with saline, TUDCA, or rhBMP-2 was implanted at the fusion area. Two and 4 weeks postimplantation, bone formation and tissue regeneration were evaluated via micro-computed tomography and histological analysis. Compared with the TUDCA-treated group, the rhBMP-2 treatment produced a higher amount of bone fusion formation after 2 weeks but also showed higher resorption of the centralized bone after 4 weeks. Interestingly, the TUDCA-treated group developed higher trabecular thickness compared with rhBMP-2 after 4 weeks. Moreover, TUDCA treatment showed distinct angiogenic activity in human umbilical vein endothelial cells as confirmed by an in vitro tube formation assay. Our findings suggest that TUDCA is comparable to rhBMP-2 in supporting bone regeneration and spinal bone formation fusion by increasing trabecular thickness and promoting angiogenesis. Finally, our results indicate that TUDCA can be utilized as a potential alternative to rhBMP-2.

Comparison of the osteogenesis and fusion rates between activin A/BMP-2 chimera (AB204) and rhBMP-2 in a beagle's posterolateral lumbar spine model

BACKGROUND CONTEXT

Activin A/BMP-2 chimera (AB204) could promote bone healing more effectively than recombinant bone morphogenetic protein 2 (rhBMP-2) with much lower dose in a rodent model, but there is no report about the effectiveness of AB204 in a large animal model.

PURPOSE

The purpose of this study was to compare the osteogenesis and fusion rate between AB204 and rhBMP-2 using biphasic calcium phosphate (BCP) as a carrier in a beagle's posterolateral lumbar fusion model.

STUDY DESIGN

This is a randomized control animal study.

METHODS

Seventeen male beagle dogs were included. Bilateral posterolateral fusion was performed at the L1-L2 and L4-L5 levels. Biphasic calcium phosphate (2 cc), rhBMP-2 (50 µg)+BCP (2 cc), or AB204 (50 µg)+BCP (2 cc) were implanted into the intertransverse space randomly. X-ray was performed at 4 and 8 weeks. After 8 weeks, the animals were sacrificed, and new bone formation and fusion rate were evaluated by manual palpation, computed tomography (CT), and undecalcified histology.

RESULTS

The AB204 group showed significantly higher fusion rate (90%) than the rhBMP-2 group (15%) or the Osteon group (6.3%) by manual palpation. On x-ray and CT assessment, fusion rate and the volume of newly formed bone were also significantly higher in AB204 group than other groups. In contrast, more osteolysis was found in rhBMP-2 group (40%) than in AB204 group (10%) on CT study. In histologic results, new bone formation was sufficient between transverse processes in AB204 group, and obvious trabeculation and bone remodeling were observed. But in rhBMP-2 group, new bone formation was less than AB204 group and osteolysis was observed between the intertransverse spaces.

CONCLUSIONS

A low dose of AB204 with BCP as a carrier significantly promotes the fusion rate in a large animal model when compared with the rhBMP-2. These findings demonstrate that AB204 could be an alternative to rhBMP-2 to improve fusion rate.

Trends, Costs, and Complications of Anterior Cervical Discectomy and Fusion With and Without Bone Morphogenetic Protein in the United States Medicare Population

STUDY DESIGN

Retrospective database review.

OBJECTIVES

After the Food and Drug Administration approved bone morphogenetic protein-2 (BMP) in 2002, BMP was used off-label in the cervical spine to increase bone growth and bony fusion. Since then, concerns have been raised regarding complication rates and safety. This study was conducted to examine the use of BMP in anterior cervical discectomy and fusion (ACDF) in the Medicare population and to determine risk of complications and associated costs within 90 days of surgery.

METHODS

Patients who underwent ACDF were identified using Current Procedural Terminology (CPT) and International Classification of Diseases, Ninth Revision Procedure codes (ICD9-P). Complications were identified using ICD9 diagnostic codes. Charges were calculated as amount billed, and reimbursements were calculated as amounts paid by Medicare. Data for these analyses came from a nationwide claims database.

RESULTS

A total of 215 047 patients were identified who had ACDF from 2005 to 2011. For the majority of the procedures (89.0%), BMP was not used. BMP use rose from 11.84% in 2005 to a peak of 16.73% in 2007 before decreasing to 12.01% in 2011. BMP was used 16% more in women than men. BMP use was the highest in the West (13.6%) followed by Midwest (11.8%), South (10.6%), and Northeast (7.5%). There was a higher overall complication rate in the BMP group (2.1%) compared with the non-BMP group (1.9%) (odds ratio [OR] = 1.11, 95% CI = 1.01-1.22). The BMP group also had a higher rate of wound complications (0.98% vs 0.76%, OR = 1.29, 95% CI = 1.12-1.48). In this study population, there was no difference in dysphagia/hoarseness, neurologic, medical, or other complications. During the 90-day perioperative period, BMP surgeries were charged at 17.6% higher than non-BMP surgeries.

CONCLUSIONS

The use of BMP in ACDF in the Medicare population has decreased since a peak in 2007. The rate of wound and overall complications for BMP use with ACDF was higher than without. Our results regarding dysphagia/hoarseness did not show a statistically meaningful difference, which is in contrast with many other studies. Charges associated with BMP use were higher during the 90-day perioperative period.

Trends Analysis of rhBMP Utilization in Single-Level Posterior Lumbar Interbody Fusion in the United States

STUDY DESIGN

Retrospective study.

OBJECTIVES

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely used in spinal fusion surgery, but there is little information on rhBMP-2 utilization in single-level posterior lumbar interbody fusion (PLIF). The purpose of our study was to evaluate the trends and demographics of rhBMP-2 utilization in single-level PLIF.

METHODS

Patients who underwent single-level PLIF from 2005 to 2011 were identified by searching ICD-9 diagnosis and procedure codes in the PearlDiver Patient Records Database, a national database of orthopedic insurance records. The year of procedure, age, gender, and region of the United States were recorded for each patient. Results were reported for each variable as the incidence of procedures identified per 100 000 patients searched in the database.

RESULTS

A total of 2735 patients had single-level PLIF. The average rate of single-level PLIF with rhBMP-2 maintained at a relatively stable level (28% to 31%) from 2005 to 2009, but decreased in 2010 (9.9%) and 2011 (11.8%). The overall incidence of single-level PLIF without rhBMP-2 (0.68 cases per 100 000 patients) was statistically higher (P < .01) compared to single-level PLIF with rhBMP-2 (0.21 cases per 100 000 patients). The average rate of single-level PLIF with rhBMP-2 utilization was the highest in West (30.1%), followed by Midwest (26.9%), South (20.5%), and Northeast (17.8%). The highest incidence of single-level PLIF with rhBMP-2 was observed in the age group <65 years (0.3 per 100 000 patients).

CONCLUSIONS

To our knowledge, this is the first study to report on the demographics associated with rhBMP-2 use in single-level PLIF. There was a 3-fold increase in the rate of PLIF without rhBMP-2 compared to PLIF with rhBMP-2, with both procedures being mainly done in patients less than 65 years of age.

Bone Morphogenetic Proteins in Pediatric Spinal Arthrodesis: A Statewide Analysis of Trends and Outcome of Utilization

INTRODUCTION

Bone morphogenetic protein (BMP) is considered off-label when used to augment spinal arthrodesis in children and adolescents. There is a paucity of longer-term information on BMP use in this population. The purpose of this study was to determine the rate of BMP utilization in pediatric spinal arthrodesis, assess factors associated with BMP use in this population, and evaluate long-term outcome.

METHODS

Spinal arthrodeses in patients 18 years and younger performed in New York State between 2004 and 2014 were identified through the Statewide Planning and Research Cooperative System database. All cases had a minimum 1-year follow-up. The primary outcome was revision arthrodesis. The primary outcome, as well as short-term and longer-term complications were identified using time-to-event analysis. Multivariable Cox proportional hazards models were used to assess the association between BMP and outcomes.

RESULTS

Of 7312 children and adolescents who underwent spinal arthrodesis, 462 (6.7%) received BMP. Utilization spiked between 2008 and 2010 when (8.6%) of cases received BMP, but subsequently BMP use returned to pre-2008 levels (2004 to 2007: 5.3%; 2011 to 2014: 5.5%). BMP was more likely to be used in children who were older (P=0.027), white and with higher mean family income (P<0.001 for race and income). BMP was more likely to be used for revision surgery, 2 to 3 level fusions, and spondylolisthesis (P<0.001 for all). Revision rates did not differ based on BMP utilization status. Patients receiving BMP did not have increased risk of short-term complications although at 5-year follow-up, BMP was associated with a statistically significant increased risk of mechanical complications (hazard ratio 1.48; 95% confidence interval, 1.02-2.14).

CONCLUSIONS

Off-label use of BMP for pediatric spinal arthrodesis increased until 2008 and now appears to be decreasing. Racial/ethnic minorities and lower socioeconomic status patients are less likely to receive BMP. The rate of revision after spinal arthrodesis does not differ between those treated with and without BMP. Further long-term studies are required to delineate appropriate guidelines for BMP utilization in children.

LEVEL OF EVIDENCE

Level III.

Complication Rates After Bone Morphogenetic Protein (BMP) Use in Orthopaedic Surgery in Children: A Concise Multicenter Retrospective Cohort Study

BACKGROUND

The use of bone morphogenetic protein (BMP) has been associated with a number of complications in adult patients. However, this association is less established in children. The aim of this study was to evaluate the safety of BMP use in children by determining the complication rates after BMP use at multiple institutions.

METHODS

In a retrospective study (2000 to 2013), the medical records of all patients who received BMP at any of the 5 institutions were reviewed. Demographic information, preoperative data, and postoperative follow-up data were collected on those patients who were under the age of 18 at the time of surgery.

RESULTS

A total of 312 pediatric patients underwent surgery with BMP application during the study period. The surgical procedures consisted of 228 spinal fusions, 39 pars repairs, 33 nonunion repair, and 12 other various procedures. Overall 21% (65/312) of patients who had BMP utilized had a complication. Fifty-five percent (36/65) of patients with a complication required a revision surgery. The average follow-up was 27 months (range, 3 to 96 mo); 80% of patients had a follow-up period of >12 months. The average age at the time of surgery was 13 years (range, 1 to 17 y). Males and females were almost equally represented in the study: 143 males (46%) and 168 females (54%). Of the patients who received BMP, 9% had minor complications and 13% had major complications. Wound dehiscence without infection was the most common minor complication and occurred in 59% (16/27) of patients with minor complications. Infection and implant failures were the most frequent major complications, occurring in 38% (15/39) and 33% (13/39) of patients with major complications, respectively. Five of 312 (2%) patients had neurological injury, 3 of which were only temporary.

CONCLUSIONS

This multicenter study demonstrates a relatively high rate of complications after the use of BMP in children. However, further study is needed to attribute the complications directly to the use of BMP.

LEVEL OF EVIDENCE

Level IV.

Implementation of a stratified approach and gene immobilization to enhance the osseointegration of a silk-based ligament graft

A silk scaffold exhibits high potential for the human anterior cruciate ligament (ACL) reconstruction due to its exceptional mechanics as well as biocompatibility. Inefficient ACL interface restoration is thought to be a major hurdle for the common implementation of a silk-based ligament graft. By integrating a stratified approach and gene immobilization, here we developed a gene-immobilized triphasic silk scaffold to enhance ACL osseointegration. Isotropic silk was divided into three regions (respectively corresponding to a ligament, fibrocartilage and the bone region of the native ACL interface) using a custom-made divider, and the lentiviral vector-encoded transforming growth factor beta-3 (TGF-β3) and bone morphogenetic protein-2 (BMP2) was further, respectively, immobilized to phosphatidylserine (PS)-coated fibrocartilage and the bone region of the triphasic silk scaffold. The in vitro assessments displayed that this gene-immobilized triphasic silk scaffold significantly promotes bone marrow mesenchymal stem cell (BMSC) proliferation and differentiation into corresponding cell lineage. Moreover, the gene-modified triphasic silk scaffold combined with BMSCs alone, which was rolled into a compact shaft to be implanted onto rabbit ACL-defect models, revealed roughly complete osseointegration restoration as a result of apparent three-layered tissue formation and robust mechanical ability as early as 12 weeks postoperatively. These outcomes demonstrated that employing the stratified approach and gene immobilization efficiently expedites silk-mediated ACL interface formation, expanding the therapeutic potential of the silk-based ligament graft for ACL reconstruction.

Small molecule-mediated tribbles homolog 3 promotes bone formation induced by bone morphogenetic protein-2

Although bone morphogenetic protein-2 (BMP2) has demonstrated extraordinary potential in bone formation, its clinical applications require supraphysiological milligram-level doses that increase postoperative inflammation and inappropriate adipogenesis, resulting in well-documented life-threatening cervical swelling and cyst-like bone formation. Recent promising alternative biomolecular strategies are toward promoting pro-osteogenic activity of BMP2 while simultaneously suppressing its adverse effects. Here, we demonstrated that small molecular phenamil synergized osteogenesis and bone formation with BMP2 in a rat critical size mandibular defect model. Moreover, we successfully elicited the BMP2 adverse outcomes (i.e. adipogenesis and inflammation) in the mandibular defect by applying high dose BMP2. Phenamil treatment significantly improves the quality of newly formed bone by inhibiting BMP2 induced fatty cyst-like structure and inflammatory soft-tissue swelling. The observed positive phenamil effects were associated with upregulation of tribbles homolog 3 (Trib3) that suppressed adipogenic differentiation and inflammatory responses by negatively regulating PPARγ and NF-κB transcriptional activities. Thus, use of BMP2 along with phenamil stimulation or Trib3 augmentation may be a promising strategy to improve clinical efficacy and safety of current BMP therapeutics.

BMP Use and the Risk of Revision Surgery After Long Posterolateral Fusions in the Elderly

STUDY DESIGN

Retrospective database review.

OBJECTIVE OF THE STUDY

The objective of the study was to assess whether bone morphogenetic protein (BMP) decreases the risk of revision surgery in elderly patients treated with 3-7 level or 8 or greater level fusions.

SUMMARY OF BACKGROUND DATA

Revision spine surgery in the elderly is a complex undertaking, highlighting the importance of discovering methods to decrease the risk of repeat procedures. The role of BMP in modulating risk of future revision surgery is not well studied in the elderly.

MATERIALS AND METHODS

The PearlDiver database (2005-2012) was queried for elderly adult spinal deformity patients treated with a primary thoracolumbar posterolateral fusion of 3 or more levels. To compare how BMP modifies revision surgery rates in 3-7 level versus 8 level or greater fusions, 4 mutually exclusive cohorts were created and matched to one another: 1043 patients treated with 8 or greater level fusions with BMP; 1111 patients with 8 or greater level fusions without BMP; 2813 patients with 3-7 level fusions with BMP; and 4770 patients with 3-7 level fusions without BMP. Revision and complication rates were compared. Complications included seroma formation, heterotopic ossification, and postoperative neuritis within 90 days.

RESULTS

Patients treated with BMP during an 8 or greater level fusion were significantly less likely to require a revision surgery than matched controls (relative risk, 0.75, P=0.015). BMP use was not associated with a decreased risk of revision surgery in 3-7 level fusions (relative risk, 0.89, P=0.20). Patients treated with BMP during 3-7 level fusions were significantly less likely to develop any of the assessed complications (P=0.02). There were no other significant differences in pairwise comparisons of subcohorts of each of the fusion lengths.

CONCLUSIONS

BMP use decreases revision rates in elderly adult spinal deformity patients treated with 8 or greater level fusions, but not in those treated with 3-7 level fusions.

LEVEL OF EVIDENCE

Level III.

Simultaneous delivery of hydrophobic small molecules and siRNA using Sterosomes to direct mesenchymal stem cell differentiation for bone repair

The use of small molecular drugs with gene manipulation offers synergistic therapeutic efficacy by targeting multiple signaling pathways for combined treatment. Stimulation of mesenchymal stem cells (MSCs) with osteoinductive small molecule phenamil combined with suppression of noggin is a promising therapeutic strategy that increases bone morphogenetic protein (BMP) signaling and bone repair. Our cationic Sterosome formulated with stearylamine (SA) and cholesterol (Chol) is an attractive co-delivery system that not only forms stable complexes with small interfering RNA (siRNA) molecules but also solubilizes hydrophobic small molecules in a single vehicle, for directing stem cell differentiation. Herein, we demonstrate the ability of SA/Chol Sterosomes to simultaneously deliver hydrophobic small molecule phenamil and noggin-directed siRNA to enhance osteogenic differentiation of MSCs both in in vitro two- and three-dimensional settings as well as in a mouse calvarial defect model. These results suggest a novel liposomal platform to simultaneously deliver therapeutic genes and small molecules for combined therapy.

STATEMENT OF SIGNIFICANCE

Application of phenamil, a small molecular bone morphogenetic protein (BMP) stimulator, combined with suppression of natural BMP antagonists such as noggin is a promising therapeutic strategy to enhance bone regeneration. Here, we present a novel strategy to co-deliver hydrophobic small molecule phenamil and noggin-targeted siRNA via cationic Sterosomes formed with stearylamine (SA) and high content of cholesterol (Chol) to enhance osteogenesis and bone repair. SA/Chol Sterosomes demonstrated high phenamil encapsulation efficiency, supported sustained release of encapsulated drugs, and significantly reduced drug dose requirements to induce osteogenic differentiation of mesenchymal stem cells (MSCs). Simultaneous deliver of phenamil and noggin siRNA in a single vehicle synergistically enhanced MSC osteogenesis and calvarial bone repair. This study suggests a new non-phospholipid liposomal formulation to simultaneously deliver small molecules and therapeutic genes for combined treatment.

Counting the Cost of Failed Spinal Fusion for Relief of Low Back Pain: Does Primary Fusion With Bone Morphogenetic Protein Make Economic Sense From a Primary Payer Perspective?

STUDY DESIGN

A retrospective cohort study.

OBJECTIVES

To investigate the unknown direct costs of failed instrumented lumbar fusion using iliac crest bone graft (ICBG) and subsequent reoperation utilizing recombinant human bone morphogenetic protein-2 (rhBMP-2) from a primary payer perspective.

SUMMARY OF BACKGROUND DATA

Recent evidence has demonstrated increased rates of instrumented lumbar fusion and utilization of rhBMP-2 to treat a range of conditions causing lower back pain. For health care providers with finite financial resources, there is an increasing demand to evaluate economic costs of available treatment modalities. The high cost of rhBMP-2 has often been cited as a leading reason for delaying its universal acceptance as a preferred substitute to ICBG. It has been hypothesized that rhBMP-2 may demonstrate cost-effectiveness if pseudarthrosis and reoperation rates are decreased, thus avoiding subsequent expenditure.

METHODS

This was a retrospective cohort study of patients who underwent instrumented lumbar fusions utilizing rhBMP-2. Hospital finance records were used to calculate direct total expenditure incurred by the primary payer for the procedure using rhBMP-2. For patients who received rhBMP-2 in a secondary lumbar fusion, additional total expenditure related to the patients' failed primary instrumented fusion with ICBG was also sought.

RESULTS

The mean total costs associated with failed instrumented lumbar fusion using ICBG and reoperation using rhBMP-2 totaled £47,734 per patient. The total direct costs of a policy of primary instrumented lumbar fusion with rhBMP-2 were less at £26,923 per patient; however, this was not significant.

CONCLUSIONS

To date, this is the first study to report the costs of failed primary instrumented lumbar fusions using ICBG and subsequent secondary fusions using rhBMP-2 from a primary payer perspective. On the basis of this evidence, a policy of using rhBMP-2 in all patients undergoing a primary instrumented lumbar fusion cannot be recommended.

Characteristics of Orthopedic Publications in High-Impact General Medical Journals

Orthopedic studies are occasionally published in high-impact general medical journals; these studies are often given high visibility and have significant potential to impact health care policy and inform clinical decision-making. The purpose of this review was to investigate the characteristics of operative orthopedic studies published in high-impact medical journals. The number of orthopedic studies published in high-impact medical journals is relatively low; however, these studies demonstrate methodological characteristics that may bias toward nonoperative treatment. Careful analysis and interpretation of orthopedic studies published in these journals is warranted. [Orthopedics. 2017; 40(3):e405-e412.].

Genetic and pharmacological inhibition of retinoic acid receptor γ function promotes endochondral bone formation

The nuclear retinoic acid receptors (RARs) play key roles in skeletal development and endochondral ossification. Previously, we showed that RARγ regulates chondrogenesis and that pharmacological activation of RARγ blocked heterotopic ossification (HO), pathology in which endochondral bone forms in soft tissues. Thus, we reasoned that pharmacological inhibition of RARγ should enhance endochondral ossification, leading to a potential therapeutic strategy for bone deficiencies. We created surgical bone defects in wild type and RARγ-null mice and monitored bone healing. Fibrous, cartilaginous, and osseous tissues formed in both groups by day 7, but more cartilaginous tissue formed in mutants within and around the defects compared to controls. Next, we implanted a mixture of Matrigel and rhBMP2 subdermally to induce ectopic endochondral ossification. Administration of RARγ antagonists significantly stimulated ectopic bone formation in wild type but not in RARγ-null mice. The antagonist-induced increases in bone formation were preceded by increases in cartilage formation and were accompanied by higher levels of phosphorylated Smad1/5/8 (pSmad1/5/8) compared to vehicle-treated control. Higher pSmad1/5/8 levels were also observed in cartilaginous tissues forming in healing bone defects in RARγ-null mice, and increases in pSmad1/5/8 levels and Id1-luc activity were observed in RARγ antagonist-treated chondrogenic cells in culture. Our data show that genetic or pharmacological interference with RARγ stimulates endochondral bone formation and does so at least in part by stimulating canonical BMP signaling. This pharmacologic strategy could represent a new tool to enhance endochondral bone formation in the setting of various orthopedic surgical interventions and other skeletal deficiencies. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1096-1105, 2017.

Predicting complication risk in spine surgery: a prospective analysis of a novel risk assessment tool

OBJECTIVE The ability to assess the risk of adverse events based on known patient factors and comorbidities would provide more effective preoperative risk stratification. Present risk assessment in spine surgery is limited. An adverse event prediction tool was developed to predict the risk of complications after spine surgery and tested on a prospective patient cohort. METHODS The spinal Risk Assessment Tool (RAT), a novel instrument for the assessment of risk for patients undergoing spine surgery that was developed based on an administrative claims database, was prospectively applied to 246 patients undergoing 257 spinal procedures over a 3-month period. Prospectively collected data were used to compare the RAT to the Charlson Comorbidity Index (CCI) and the American College of Surgeons National Surgery Quality Improvement Program (ACS NSQIP) Surgical Risk Calculator. Study end point was occurrence and type of complication after spine surgery. RESULTS The authors identified 69 patients (73 procedures) who experienced a complication over the prospective study period. Cardiac complications were most common (10.2%). Receiver operating characteristic (ROC) curves were calculated to compare complication outcomes using the different assessment tools. Area under the curve (AUC) analysis showed comparable predictive accuracy between the RAT and the ACS NSQIP calculator (0.670 [95% CI 0.60-0.74] in RAT, 0.669 [95% CI 0.60-0.74] in NSQIP). The CCI was not accurate in predicting complication occurrence (0.55 [95% CI 0.48-0.62]). The RAT produced mean probabilities of 34.6% for patients who had a complication and 24% for patients who did not (p = 0.0003). The generated predicted values were stratified into low, medium, and high rates. For the RAT, the predicted complication rate was 10.1% in the low-risk group (observed rate 12.8%), 21.9% in the medium-risk group (observed 31.8%), and 49.7% in the high-risk group (observed 41.2%). The ACS NSQIP calculator consistently produced complication predictions that underestimated complication occurrence: 3.4% in the low-risk group (observed 12.6%), 5.9% in the medium-risk group (observed 34.5%), and 12.5% in the high-risk group (observed 38.8%). The RAT was more accurate than the ACS NSQIP calculator (p = 0.0018). CONCLUSIONS While the RAT and ACS NSQIP calculator were both able to identify patients more likely to experience complications following spine surgery, both have substantial room for improvement. Risk stratification is feasible in spine surgery procedures; currently used measures have low accuracy.

A Retrospective Analysis of Complications Associated With Bone Morphogenetic Protein 2 in Anterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective review.

OBJECTIVE

The aim of our study was to quantify the frequency of complications associated with recombinant human bone morphogenetic protein 2 (rhBMP-2) use in anterior lumbar interbody fusion (ALIF).

METHODS

The orthopedic subset of the Medicare database (PearlDiver) was queried for this retrospective cohort study using International Statistical Classification of Diseases 9 (ICD-9) and Current Procedure Terminology (CPT) codes for ALIF procedures with and without rhBMP-2 between 2005 and 2010. Frequencies of complications and reoperations were then identified within 1 year from the index procedure. Complications included reoperations, pulmonary embolus, deep vein thrombosis, myocardial infarction, nerve-related complications, incision and drainage procedures, wound, sepsis, pneumonia, urinary tract infections, respiratory, heterotopic ossification, retrograde ejaculation, radiculopathy, and other medical complications. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the statistical significance.

RESULTS

We identified a total of 41 865 patients who had an ALIF procedure. A total of 14 384 patients received rhBMP-2 while 27 481 did not. Overall, 6016 (41.8%) complications within 1 year from surgery were noted within the group who received rhBMP-2 and 12 950 (47.1%) complications within 1 year from surgery were recorded in those who did not receive rhBMP-2 (OR = 0.81, CI = 0.77-0.84). Overall, exposure to rhBMP-2 was associated with significantly decreased odds of complications with exception to reoperation rates (0.9% rhBMP-2 vs 1.0% no rhBMP-2; OR = 0.88, CI = 0.71-1.09) and radiculopathy (4.4% rhBMP-2 vs 4.3% no rhBMP-2; OR = 1.02, CI = 0.93-1.13).

CONCLUSIONS

The use of rhBMP-2 in patients undergoing ALIF procedure was associated with a significantly decreased rate of complications. Further studies are needed to elucidate a true incidence of complication.

Formulation, Delivery and Stability of Bone Morphogenetic Proteins for Effective Bone Regeneration

Bone morphogenetic proteins (BMPs) are responsible for bone formation during embryogenesis and bone regeneration and remodeling. The osteoinductive action of BMPs, especially BMP-2 and BMP-7, has led to their use in a range of insurmountable treatments where intervention is required for effective bone regeneration. Introduction of BMP products to the market, however, was not without reports of multiple complications and side effects. Aiming for optimization of the therapeutic efficacy and safety, efforts have been focused on improving the delivery of BMPs to lower the administered dose, localize the protein, and prolong its retention time at the site of action. A major challenge with these efforts is that the protein stability should be maintained. With this review we attempt to shed light on how the stability of BMPs can be affected in the formulation and delivery processes. We first provide a short overview of the current standing of the complications experienced with BMP products. We then discuss the different delivery parameters studied in association with BMPs, and their influence on the efficacy and safety of BMP treatments. In particular, the literature addressing the stability of BMPs and their possible interactions with components of the delivery system as well as their sensitivity to conditions of the formulation process is reviewed. In summary, recent developments in the fields of bioengineering and biopharmaceuticals suggest that a good understanding of the relationship between the formulation/delivery conditions and the stability of growth factors such as BMPs is a prerequisite for a safe and effective treatment.

BMP-2-induced bone formation and neural inflammation

Bone morphogenetic protein-2 (BMP-2), a potent osteoinductive cytokine from the transforming growth factor beta (TGF-β) family, is currently the most commonly used protein-based bone graft substitute. Although clinical use of BMP-2 has significantly increased in recent years, its prominence has also highlighted various adverse events, including induction of inflammation. This review will elucidate the relationship between BMP-2 and inflammation, with an emphasis on peripheral nerve inflammation and its sequelae. As well, we review the potential additive roles of nerve released factors with BMP2 in the context of bone formation.

Application of a three-dimensional graft of autologous osteodifferentiated adipose stem cells in patients undergoing minimally invasive transforaminal lumbar interbody fusion: clinical proof of concept

BACKGROUND

The authors applied a scaffold-free osteogenic three-dimensional (3D) graft made of adipose-derived mesenchymal stem cells (AMSCs) in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MI-TLIF).

METHODS

Three patients (two patients and one patient with 1 and 2 levels, respectively) with degenerative spondylolisthesis underwent MI-TLIF with 3D graft made of AMSCs. To obtain the AMSCs, fatty tissue was collected from the abdomen by lipoaspiration and differentiated afterwards in our Cell/Tissue bank. Clinical outcomes, including the Oswestry Disability Index (ODI) and visual analog scale (VAS) as well as fusion status were assessed preoperatively and up to 12 months postoperatively.

RESULTS

At 12 months, all four operated AMSC levels could be assessed (n = 4). Grade 3 fusion could be confirmed at two levels out of four. Mean VAS score improved from 8.3 to 2 and ODI also improved from 47 to 31%. No donor site complication was observed. The final AMSC osteogenic product was stable, did not rupture with forceps manipulation, and was easily implanted directly into the cage with no marked modification of operating time.

CONCLUSIONS

A scaffold-free 3D graft made of AMSCs can be manufactured and used as a promising alternative for spinal fusion procedures. Nevertheless, further studies of a larger series of patients are needed to confirm its effectiveness.

Complications Associated With Bone Morphogenetic Protein in the Lumbar Spine

Complications associated with the use of recombinant human bone morphogenetic protein in the lumbar spine include retrograde ejaculation, ectopic bone formation, vertebral osteolysis and subsidence, postoperative radiculitis, and hematoma and seroma. These complications are controversial and remain widely debated. This article discusses the reported complications and possible implications for the practicing spine surgeon. Understanding the complications associated with the use of recombinant human bone morphogenetic protein and the associated controversies allows for informed decision making by both the patient and the surgeon. [Orthopedics. 2017; 40(2):e229-e237.].