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

The Acute Inflammatory Response to Absorbed Collagen Sponge Is Not Enhanced by BMP-2

Absorbed collagen sponge (ACS)/bone morphogenetic protein-2 (BMP-2) are widely used in clinical practise for bone regeneration. However, the application of this product was found to be associated with a significant pro-inflammatory response, particularly in the early phase after implantation. This study aimed to clarify if the pro-inflammatory activities, associated with BMP-2 added to ACS, were related to the physical state of the carrier itself, i.e., a wet or a highly dehydrated state of the ACS, to the local degree of vascularisation and/or to local biomechanical factors. ACS (0.8 cm diameter)/BMP-2 were implanted subcutaneously in the back of 12 eight-week-old Sprague Dawley rats. Two days after surgery, the implanted materials were retrieved and analysed histologically and histomorphometrically. The acute inflammatory response following implantation of ACS was dependent of neither the presence or absence of BMP-2 nor the degree of vascularization in the surrounding tissue nor the hydration state (wet versus dry) of the ACS material at the time of implantation. Differential micro biomechanical factors operating at the implantation site appeared to have an influence on the thickness of inflammation. We conclude that the degree of the early inflammatory response of the ACS/BMP-2 may be associated with the physical and chemical properties of the carrier material itself.

Comparison of two independent systematic reviews of trials of recombinant human bone morphogenetic protein-2 (rhBMP-2): the Yale Open Data Access Medtronic Project

BACKGROUND

It is uncertain whether the replication of systematic reviews, particularly those with the same objectives and resources, would employ similar methods and/or arrive at identical findings. We compared the results and conclusions of two concurrent systematic reviews undertaken by two independent research teams provided with the same objectives, resources, and individual participant-level data.

METHODS

Two centers in the USA and UK were each provided with participant-level data on 17 multi-site clinical trials of recombinant human bone morphogenetic protein-2 (rhBMP-2). The teams were blinded to each other's methods and findings until after publication. We conducted a retrospective structured comparison of the results of the two systematic reviews. The main outcome measures included (1) trial inclusion criteria; (2) statistical methods; (3) summary efficacy and risk estimates; and (4) conclusions.

RESULTS

The two research teams' meta-analyses inclusion criteria were broadly similar but differed slightly in trial inclusion and research methodology. They obtained similar results in summary estimates of most clinical outcomes and adverse events. Center A incorporated all trials into summary estimates of efficacy and harms, while Center B concentrated on analyses stratified by surgical approach. Center A found a statistically significant, but small, benefit whereas Center B reported no advantage. In the analysis of harms, neither showed an increased cancer risk at 48 months, although Center B reported a significant increase at 24 months. Conclusions reflected these differences in summary estimates of benefit balanced with small but potentially important risk of harm.

CONCLUSIONS

Two independent groups given the same research objectives, data, resources, funding, and time produced broad general agreement but differed in several areas. These differences, the importance of which is debatable, indicate the value of the availability of data to allow for more than a single approach and a single interpretation of the data.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42012002040 and CRD42012001907 .

Delivery vehicle effects on bone regeneration and heterotopic ossification induced by high dose BMP-2

Bone morphogenetic protein-2 (BMP-2), delivered on absorbable collagen sponge, is frequently used to treat bone defects. However, supraphysiological BMP-2 doses are common and often associated with complications such as heterotopic ossification and inflammation, causing pain and impaired mobility. This has prompted investigations into strategies to spatially control bone regeneration, for example growth factor delivery in appropriate scaffolds. Our objective was to investigate the spatiotemporal effects of high dose BMP-2 on bone regeneration as a function of the delivery vehicle. We hypothesized that an alginate delivery system would spatially restrict bone formation compared to a collagen sponge delivery system. In vitro, BMP-2 release was accelerated from collagen sponge compared to alginate constructs. In vivo, bone regeneration was evaluated over 12weeks in critically sized rat femoral segmental defects treated with 30μg rhBMP-2 in alginate hydrogel or collagen sponge, surrounded by perforated nanofiber meshes. Total bone volume, calculated from micro-CT reconstructions, was higher in the alginate group at 12weeks. Though bone volume within the central defect region was greater in the alginate group at 8 and 12weeks, heterotopic bone volume was similar between groups. Likewise, mechanical properties from ex vivo torsional testing were comparable between groups. Histology corroborated these findings and revealed heterotopic mineralization at 2weeks post-surgery in both groups. Overall, this study recapitulated the heterotopic ossification associated with high dose BMP-2 delivery, and demonstrated that the amount and spatial pattern of bone formation was dependent on the delivery matrix.

STATEMENT OF SIGNIFICANCE

Alginate hydrogel-based BMP-2 delivery has induced better spatiotemporal bone regeneration in animals, compared to clinically used collagen sponge, at lower BMP-2 doses. Lack of clear dose-response relationships for BMP-2 vis-à-vis bone regeneration has contributed to the use of higher doses clinically. We investigated the potential of the alginate system, with comparatively favorable BMP-2 release-kinetics, to reduce heterotopic ossification and promote bone regeneration, when used with a high BMP-2 dose. While defect mineralization improved with alginate hydrogel, the initial high-release phase and likely early tissue exposure to BMP-2 appeared sufficient to induce heterotopic ossification. The characterization presented here should provide the framework for future evaluations of strategies to optimize bone formation and minimize adverse effects of high dose BMP-2 therapy.

Growth factor-eluting technologies for bone tissue engineering

Growth factors are essential orchestrators of the normal bone fracture healing response. For non-union defects, delivery of exogenous growth factors to the injured site significantly improves healing outcomes. However, current clinical methods for scaffold-based growth factor delivery are fairly rudimentary, and there is a need for greater spatial and temporal regulation to increase their in vivo efficacy. Various approaches used to provide spatiotemporal control of growth factor delivery from bone tissue engineering scaffolds include physical entrapment, chemical binding, surface modifications, biomineralization, micro- and nanoparticle encapsulation, and genetically engineered cells. Here, we provide a brief review of these technologies, describing the fundamental mechanisms used to regulate release kinetics. Examples of their use in pre-clinical studies are discussed, and their capacities to provide tunable, growth factor delivery are compared. These advanced scaffold systems have the potential to provide safer, more effective therapies for bone regeneration than the systems currently employed in the clinic.

Change in Off-Label Use of Bone Morphogenetic Protein in Spine Surgery and Associations with Adverse Outcome

Study Design Retrospective cohort study. Objective The U.S. Food and Drug Administration issued a warning in 2008 against off-label bone morphogenetic protein (BMP-2) use. We aimed to determine (off-label) BMP-2 use in two periods and associations with complications. Methods We included 340,393 patients undergoing spinal fusions from the Premier Perspective database (2006 to 2012). BMP-2 use was determined from billing in 2006 to 2008 versus 2009 to 2012. Outcomes included revisions, length of hospital stay (LOHS), and cost of hospital stay (COH). Multilevel regressions measured associations between BMP-2 and outcomes; odds ratios (ORs) and 95% confidence intervals (CIs) are reported. Results BMP-2 use decreased from 18.7% in 2006 to 11.5% in 2012. Off-label use remains but is decreasing, particularly for cervical anterior (5.1 versus 2.0%) and cervical posterior procedures (15.3 versus 8.5%; both p < 0.01 comparing 2006 to 2008 with 2009 to 2012). BMP-2 remains associated with increased LOHS (median 2 versus 3 days; both periods) and COH (median $15,455 versus $27,881 in 2006 to 2008; $17,007 versus $30,331 in 2009 to 2012). Adjusted ORs for the association between BMP-2 and adverse outcomes were generally lower in 2009 to 2012 compared with 2006 to 2008. Most notably, we demonstrate lower ORs for revision after cervical fusions in 2009 to 2012 (OR 1.67, CI 1.01 to 2.78) compared with 2006 to 2008 (OR 2.43, CI 1.66 to 3.54). Conclusions Using a previously untapped data source, we show decreased (off-label) BMP-2 use in spinal fusions, particularly in cervical fusions. Although there was a tendency of decreased odds in 2009 to 2012, higher resource utilization and odds for complications remain in patients using BMP-2. A national registry or prospective observational studies will benefit the ongoing discussion.

Biomaterials to Facilitate Delivery of RNA Agents in Bone Regeneration and Repair

Bone healing after traumatic injuries or pathological diseases remains an important worldwide problem. In search of safer and more effective approaches to bone regeneration and repair, RNA-based therapeutic agents, specifically microRNAs (miRNAs) and short interfering RNA (siRNA), are beginning to be actively explored. In this review, we summarize current attempts to employ miRNAs and siRNAs in preclinical models of bone repair. We provide a summary of current limitations when attempting to utilize bioactive nucleic acids for therapeutic purposes and position the unique aspects of RNA reagents for clinical bone repair. Delivery strategies for RNA reagents are emphasized and nonviral carriers (biomaterial-based) employed to deliver such reagents are reviewed. Critical features of biomaterial carriers and various delivery technologies centered around nanoparticulate systems are highlighted. We conclude with the authors' perspectives on the future of the field, outlining main critical issues important to address as RNA reagents are explored for clinical applications.

RhBMP-2-induced radiculitis in patients undergoing transforaminal lumbar interbody fusion: relationship to dose

BACKGROUND CONTEXT

Recombinant human bone morphogenetic protein-2 (rhBMP-2) remains the primary synthetic osteoinductive material used in spinal fusion surgery today. The early inflammation reaction to rhBMP-2 manifesting with radicular symptoms has been previously reported in patients undergoing transforaminal lumbar interbody fusion (TLIF). There is a disagreement with regard to the factors affecting its occurrence and whether such symptoms are dose dependent.

PURPOSE

The purpose of this analysis was to determine the incidence of rhBMP-2-induced radiculitis and its relationship to dose.

STUDY DESIGN/SETTING

A retrospective cohort analysis was performed of the prospectively collected data.

PATIENT SAMPLE

All consecutive patients (n=204) who underwent one- or two-level TLIF and instrumented posterolateral fusion with an off-label rhBMP-2 use were included in this analysis.

OUTCOME MEASURES

The patients who developed new radicular symptoms after initial improvement postoperatively and had sterile fluid collections indicative of inflammatory process, or in the absence of any structural abnormalities that would explain these symptoms on imaging studies, were deemed to have rhBMP-2-induced radiculitis.

METHODS

Magnetic resonance imaging (MRI) scans were obtained for all patients who developed postoperative radicular symptoms. Correlations between the total rhBMP-2 dose, dose per spinal level, and incidence of radiculitis were evaluated while controlling for age, sex, number of TLIF levels, and surgeon.

RESULTS

The incidence of postoperative radiculitis was 11.3% (23 out of 204). The average total rhBMP-2 dose was 4.9 mg (range=2.1-12) and the average dose per spinal level was 3.8 mg (range=1.05-12). Logistic regression analysis did not identify any significant correlations between the rhBMP-2 doses and the incidence of radiculitis (p=.6).

CONCLUSION

The incidence of rhBMP-2-induced radiculitis in patients undergoing TLIF is quite high, but there were no dose-related correlations found. The study, however, cannot rule out a possibility that a larger variation in bone morphogenetic protein (BMP) doses could still be a factor in the development of rhBMP-2-associated radiculitis.

Meta-analysis of the Impact of Patient Characteristics on Estimates of Effectiveness and Harms of Recombinant Human Bone Morphogenetic Protein-2 in Lumbar Spinal Fusion

STUDY DESIGN

Meta-analysis of individual patient data from randomized controlled trials of recombinant human bone morphogenetic protein-2 (rhBMP-2) in lumbar spinal fusion.

OBJECTIVE

To determine how patient characteristics impact estimates of effectiveness and harms of rhBMP-2 versus iliac crest bone graft (ICBG) in lumbar spinal fusion.

SUMMARY OF BACKGROUND DATA

Patient characteristics are thought to impact rates of fusion in spinal fusion surgery, but no analyses examining the effect of patient characteristics on efficacy and safety of rhBMP-2 as compared with ICBG have been conducted.

METHODS

Using individual patient data obtained from the Yale Open Data Access Project, the impact of patient characteristics on the effects of rhBMP-2 on fusion, overall success, and harms were assessed using linear and generalized linear mixed effects models.

RESULTS

Ten industry-sponsored randomized controlled trials of rhBMP-2 were included in the analysis. There is preliminary support for an association between rhBMP-2 and improved outcomes for smokers (P = 0.01), individuals under the age of 60 years (P < 0.01), and patients of normal weight (P = 0.03), but not in patients who are nonsmokers, over the age of 60 years, obese or severely obese. RhBMP-2 usage was associated with decreased harms in individuals with no previous back surgeries but this was not seen in individuals with a previous back surgery (P < 0.01).

CONCLUSION

Effects of rhBMP-2 may vary according to patient characteristics. Future studies of rhBMP-2 should include planned subgroup analysis in patients over 60 years, smokers, patients that are obese and severely obese, and individuals with previous back surgeries to better identify those most likely to benefit.

LEVEL OF EVIDENCE

1.

Modified Mini-open Transforaminal Lumbar Interbody Fusion: Description of Surgical Technique and Assessment of Free-hand Pedicle Screw Insertion

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To describe a modified technique for mini-open transforaminal lumbar interbody fusion (TLIF) that improves visualization for decompression, fusion, and freehand pedicle screw insertion. Accuracy of freehand pedicle screw placement with this technique was assessed.

SUMMARY OF BACKGROUND DATA

Mini-open TLIF is a minimally invasive technique that allows limited visualization of the bone and neural anatomy via an expandable tubular retractor inserted through the Wiltse plane. No significant modification that of this technique has been described in detail.

METHODS

In this study, 92 consecutive patients underwent one-level modified mini-open TLIF (MOTLIF). MOTLIF modifications consisted of (i) transmuscular dissection through the multifidus muscle rather than intermuscular dissection in the Wiltse plane; (ii) microsurgical detachment of multifidus from the facet rather than muscle dilation; (iii) en bloc total facetectomy (unilateral or bilateral, as needed for decompression); (iv) facet autograft used for interbody fusion; and (v) solid pedicle screws placed bilaterally by a freehand technique under direct vision.

RESULTS

The mean age was 53 years. Mean follow-up was 35 months (minimum 2 yrs). By 6 months, mean Visual Analog Scale for back and leg pain had improved from 51 to 19 and from 58 to 17, respectively, and mean Oswestry Disability Index (ODI) improved from 53 to 16. These improvements persisted at 2 years. Solid fusion, defined by computed tomography at 1 year, was achieved in 88.1%, whereas satisfactory fusion was achieved in 95.2% of patients. Pedicle screws were accurately placed in 335 of 336 imaged pedicles (pedicle breach grades: 91.1% grade 1; 8.6% grade 2; and 0.3% grade 3). Mean fluoroscopy time was 29.3 seconds.

CONCLUSION

MOTLIF is a safe and effective minimally invasive technique with a high fusion rate. It allows accurate pedicle screw placement by a freehand technique. By eliminating bi-planar fluoroscopy, it helps reduce radiation exposure. This is the largest published report of mini-open TLIF to date.

LEVEL OF EVIDENCE

4.

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.

The Risk of Cancer With the Use of Recombinant Human Bone Morphogenetic Protein in Spine Fusion

STUDY DESIGN

Retrospective cohort study using the Washington State Comprehensive Hospital Abstract Reporting System, the Washington State Cancer Registry, and Washington State death certificates.

OBJECTIVE

To study the possible association between recombinant human bone morphogenetic protein (rhBMP) and cancer risk.

SUMMARY OF BACKGROUND DATA

The use of rhBMP in spine fusion surgery remains controversial with respect to its possible role in tumorigenesis.

METHODS

We compared adults who underwent spine fusion for degenerative disease with and without rhBMP between 2002 and 2010. Patients were matched on the basis of age, sex, and year of treatment. We excluded patients with a diagnosis of cancer before or at the index procedure. The primary outcome was the first diagnosis of cancer as identified in the records of the cancer registry.

RESULTS

We included 16,914 patients who had spine fusion, of whom 4246 received rhBMP. During the study period, 449 patients received a diagnosis of cancer: 117 (2.76% of 4246) in the rhBMP group and 332 (2.62% of 12 668) in the no rhBMP group. The incidence rate was similar between the rhBMP and no rhBMP 9.5 and 9.0 per 1000 person years, respectively (hazard ratio, 1.06; 95% confidence interval, 0.86-1.30). There were no differences in the rate of cancer between the two groups in subgroups defined on the basis of site of fusion or surgical method.

CONCLUSION

There was no increase in overall cancer incidence among those receiving rhBMP. An important limitation of this and other studies of rhBMP and cancer that have been conducted to date is their relatively limited duration of follow-up. The examination of cancer incidence following rhBMP administration must continue beyond just the first several years to adequately assess the potential of rhBMP to influence the occurrence of one or more types of malignancy.

LEVEL OF EVIDENCE

3.

Functional regeneration of ligament-bone interface using a triphasic silk-based graft

The biodegradable silk-based scaffold with unique mechanical property and biocompatibility represents a favorable ligamentous graft for tissue-engineering anterior cruciate ligament (ACL) reconstruction. However, the low efficiency of ligament-bone interface restoration barriers the isotropic silk graft to common ACL therapeutics. To enhance the regeneration of the silk-mediated interface, we developed a specialized stratification approach implementing a sequential modification on isotropic silk to constitute a triphasic silk-based graft in which three regions respectively referring to ligament, cartilage and bone layers of interface were divided, followed by respective biomaterial coating. Furthermore, three types of cells including bone marrow mesenchymal stem cells (BMSCs), chondrocytes and osteoblasts were respectively seeded on the ligament, cartilage and bone region of the triphasic silk graft, and the cell/scaffold complex was rolled up as a multilayered graft mimicking the stratified structure of native ligament-bone interface. In vitro, the trilineage cells loaded on the triphasic silk scaffold revealed a high proliferative capacity as well as enhanced differentiation ability into their corresponding cell lineage. 24 weeks postoperatively after the construct was implanted to repair the ACL defect in rabbit model, the silk-based ligamentous graft exhibited the enhancement of osseointegration detected by a robust pullout force and formation of three-layered structure along with conspicuously corresponding matrix deposition via micro-CT and histological analysis. These findings potentially broaden the application of silk-based ligamentous graft for ACL reconstruction and further large animal study.

Long-Segment Fusion for Adult Spinal Deformity Correction Using Low-Dose Recombinant Human Bone Morphogenetic Protein-2

BACKGROUND:

Although use of very high-dose recombinant human bone morphogenetic protein-2 (rhBMP-2) has been reported to markedly improve fusion rates in adult spinal deformity (ASD) surgery, most centers use much lower doses due to cost constraints. How effective these lower doses are for fusion enhancement remains unclear.

OBJECTIVE:

To assess fusion rates using relatively low-dose rhBMP-2 for ASD surgery.

METHODS:

This was a retrospective review of consecutive ASD patients that underwent thoracic to sacral fusion. Patients that achieved 2-year follow-up were analyzed. Impact of patient and surgical factors on fusion rate was assessed, and fusion rates were compared with historical cohorts.

RESULTS:

Of 219 patients, 172 (78.5%) achieved 2-year follow-up and were analyzed. Using an average rhBMP-2 dose of 3.1 mg/level (average total dose = 35.9 mg/case), the 2-year fusion rate was 73.8%. Cancellous allograft, local autograft, and very limited iliac crest bone graft (&lt;20 mL, obtained during iliac bolt placement) were also used. On multivariate analysis, female sex was associated with a higher fusion rate, whereas age, comorbidity score, deformity type, and 3-column osteotomy were not. There were no complications directly attributable to rhBMP-2.

CONCLUSION:

Fusion rates for ASD using low-dose rhBMP-2 were comparable to those reported for iliac crest bone graft but lower than for high-dose rhBMP-2. Importantly, there were substantial differences between patients in the present series and those in the historical comparison groups that could not be fully adjusted for based on available data. Prospective evaluation of rhBMP-2 dosing for ASD surgery is warranted to define the most appropriate dose that balances benefits, risks, and costs.

Lower cervical levels: Increased risk of early dysphonia following anterior cervical spine surgery

OBJECTIVES

The present study aimed to re-evaluate the incidence of early dysphonia after anterior cervical spine surgery (ACSS) and to determine the related risk factors.

CLINICAL MATERIALS AND METHODS

Patients underwent ACSS between January 2011 and December 2013 at two sites were identified retrospectively from hospital's patient databases. A total of 233 cases were included in this study. Dysphonia developed 1 month postoperatively was recorded. Follow-up was conducted in all positive-response patients. Those reporting severe or persistent voice symptoms were referred to otolaryngologists for further assessments and (or) treatments. Pre and intraoperative factors were collected to determine their relationships with dysphonia one month postoperatively.

RESULTS

45 patients developed dysphonia at one month, including 23 males and 22 females, yielding to an incidence of 19.3%. 34 cases resolved themselves in 3 months, leaving the remaining 11 patients considered to be severe or persistent cases. However, 10 of them recovered spontaneously in the next 9 months, while the last case received vocal cord medialization and returned to almost normal speech function at 18 months. In univariate analysis, only approaching level involving C6-C7 or (and) C7-T1 was significantly associated with postoperative dysphonia (P<0.001). This association was not weakened in multiple logistic regression analysis (OR 2.348, 95% CI 1.467-3.659, P<0.001).

CONCLUSION

The incidence of early dysphonia following ACSS was relatively high and approaching at lower cervical levels was an independent predictive factor.

Trends of Posterior Long Segment Fusion with and without Recombinant Human Bone Morphogenetic Protein 2 in Patients with Scoliosis

STUDY DESIGN

Retrospective study.

OBJECTIVE

Symptomatic scoliosis can be a source of severe pain and disability. When nonoperative treatments fail, spine fusion is considered as an effective procedure in scoliosis management. The purpose of this study was to evaluate the trends of patients with scoliosis undergoing posterior long segment fusion (PLSF) with and without recombinant human bone morphogenetic protein 2 (rhBMP-2).

METHODS

Patients within the orthopedic subset of Medicare database undergoing PLSF from 2005 to 2011 were identified using the PearlDiver Patient Records Database. Both diagnosis and procedural International Classification of Diseases, ninth edition and Current Procedural Terminology codes were used. The year of procedure, age, sex, region, and rhBMP-2 use were recorded.

RESULTS

In total, 1,265,591 patients with scoliosis were identified with 29,787 PLSF surgeries between 2005 and 2011. The incidence of PLSF procedures increased gradually from 2005 to 2009, decreased in 2010 (p < 0 0.01), and grew again in 2011. Patients over age 84 years had the highest incidence of PLSF. The lowest incidence of the procedures was in the Northeast, 5.96 per 100,000 patients. Sex differences were observed with a male-to-female ratio of 0.40 (p < 0.01). The use of rhBMP-2 for PLSF increased steadily from 2005 to 2009; the numbers dropped dramatically in 2010 and returned by 2011.

CONCLUSIONS

According to our study, patients with scoliosis demonstrated a 0.6575 average incidence increase of PLSF treatments annually. There were significant differences in incidence of PLSF procedure and patient demographics. Additionally, rhBMP-2 consumption significantly changed when we stratified it by sex, age, and region respectively.

Heparin-Based Polyelectrolyte Complex Enhances the Therapeutic Efficacy of Bone Morphogenetic Protein-2 for Posterolateral Fusion in a Large Animal Model

STUDY DESIGN

The study was based on porcine posterolateral fusion model.

OBJECTIVE

The study aims to prove that polyelectrolyte complex (PEC) carrier could enhance the efficacy and safety profile of bone morphogenetic protein-2 (BMP-2).

SUMMARY OF BACKGROUND DATA

BMP-2 was introduced to enhance posterolateral fusion; however, extremely high doses of this molecule were often used which contributed to various complications. This was attributed to the poor modulation capacity of the traditional carrier absorbable collagen sponge (ACS). To reduce the efficacious dose of BMP-2 and its associated complications, heparin-based PEC was introduced.

METHODS

L3/L4 and L5/L6 two-level posterolateral spinal fusion was performed on six pigs using two doses of BMP-2 with PEC or ACS: (1) PEC with 800 μg BMP-2 (n = 2); (2) PEC with 400 μg BMP-2 (n = 2); (3) ACS with 800 μg BMP-2 (n = 1); (4) ACS with 400 μg of BMP-2 (n = 1). The construct was loaded into a rigid bioabsorbable cage for implantation. Fusion rate and quality were assessed 2 months after operation.

RESULTS

Manual palpation revealed successful fusion in all groups. Radiological fusion score of PEC groups was, however, higher than that of ACS groups. The newly formed bone in PEC groups appeared to be well integrated into the native bone with no overgrowth into the adjacent structure. On comparison, in ACS groups, large gaps were observed between the newly formed bone and the fusion bed with heterotopic ossification into the psoas muscle. The microarchitecture on the newly formed bone in PEC groups was superior to that in ACS groups, which was demonstrated by higher three-dimensional parameters.

CONCLUSION

The present study demonstrated that BMP-2 delivered by PEC induced successful posterolateral fusion in porcine model. The efficacy of BMP-2 was improved and bony overgrowth was reduced. The microarchitecture of BMP-2-induced bone tissue was also enhanced by PEC.

LEVEL OF EVIDENCE

N/A.

A population-based review of bone morphogenetic protein: associated complication and reoperation rates after lumbar spinal fusion

OBJECT The authors compared the rates of postoperative adverse events and reoperation of patients who underwent lumbar spinal fusion with bone morphogenetic protein (BMP) to those of patients who underwent lumbar spinal fusion without BMP. METHODS The authors retrospectively analyzed the PearlDiver Technologies, Inc., database, which contains the Medicare Standard Analytical Files, the Medicare Carrier Files, the PearlDiver Private Payer Database (UnitedHealthcare), and select state all-payer data sets, from 2005 to 2010. They identified patients who underwent lumbar spinal fusion with and without BMP. The ICD-9-CM code 84.52 was used to identify patients who underwent spinal fusion with BMP. ICD-9-CM diagnosis codes identified complications that occurred during the initial hospital stay. ICD-9-CM procedural codes were used to identify reoperations within 90 days of the index procedure. The relative risks (and 95% CIs) of BMP use compared with no BMP use (control) were calculated for the association of any complication with BMP use compared with the control. RESULTS Between 2005 and 2010, 460,773 patients who underwent lumbar spinal fusion were identified. BMP was used in 30.7% of these patients. The overall complication rate in the BMP group was 18.2% compared with 18.7% in the control group. The relative risk of BMP use compared with no BMP use was 0.976 (95% CI 0.963-0.989), which indicates a significantly lower overall complication rate in the BMP group (p < 0.001). In both treatment groups, patients older than 65 years had a statistically significant higher rate of postoperative complications than younger patients (p < 0.001). CONCLUSIONS In this large-scale institutionalized database study, BMP use did not seem to increase the overall risk of developing a postoperative complication after lumbar spinal fusion surgery.

Recombinant Human Bone Morphogenetic Protein-2 in Posterolateral Spinal Fusion: What's the Right Dose?

STUDY DESIGN

Single center retrospective cohort analysis.

PURPOSE

The goal was to evaluate the influence of varying amount of recombinant human bone morphogenetic protein 2 (rhBMP-2) per level on fusion rates and complications in posterolateral spinal fusions.

OVERVIEW OF LITERATURE

rhBMP-2 has been utilized for lumbar posterolateral fusions for many years. Initial rhBMP-2 recommendations were 20 mg/level of fusion. Dose and concentration per level in current studies vary from 4.2 to 40 mg and 1.5 to 2.0 mg/mL, respectively. Variable fusion and complication rates have been reported.

METHODS

Patients (n=1,610) undergoing instrumented lumbar spinal fusion (2003-2009) with utilization of rhBMP-2 were retrospectively evaluated. Patient demographics, body mass index (BMI), comorbidities, number of levels, associated interbody fusion, and types of bone void filler were analyzed. Fusions rates and nonunions were subdivided into number of levels and amount of rhBMP-2 used per level.

RESULTS

Patients (n=559) were evaluated with 58.5% females having an average age of 63 years, BMI of 31 kg/m(2). Number of levels fused ranged from 1 to 8. rhBMP-2 averaged 7.3 mg/level (range, 1.5-24 mg/level) based upon length of collagen sponge in relation to length of fusion levels. Patients with non-union formation had lower rhBMP-2 dose per level (p=0.016). A significant difference in non-union rate was found between patients undergoing fusion with <6 mg/level compared to those with >6 mg/level (9.1% vs. 2.4%, χ(2)=0.012). No significant differences were noted between 6-11.9 mg/level and ≥12 mg/level. No threshold was found for seroma formation or bone overgrowth.

CONCLUSIONS

Previous recommendation of 20 mg/level of rhBMP-2 is more than what is required for predictable fusion rates of 98%. No dose related increase of infection, seroma formation, and bone overgrowth has been found. In order to provide variable dosing and cost reduction, industry generated rhBMP-2 kit size should be optimized.

Effects of a Commercial Insurance Policy Restriction on Lumbar Fusion in North Carolina and the Implications for National Adoption

STUDY DESIGN

An analysis of the State Inpatient Database of North Carolina, 2005 to 2012, and the Nationwide Inpatient Sample, including all inpatient lumbar fusion admissions from nonfederal hospitals.

OBJECTIVE

The aim of the study was to examine the influence of a major commercial policy change that restricted lumbar fusion for certain indications and to forecast the potential impact if the policy were adopted nationally.

SUMMARY OF BACKGROUND DATA

Few studies have examined the effects of recent changes in commercial coverage policies that restrict the use of lumbar fusion.

METHODS

We included adults undergoing elective lumbar fusion or re-fusion operations in North Carolina. We aggregated data into a monthly time series to report changes in the rates and volume of lumbar fusion operations for disc herniation or degeneration, spinal stenosis, spondylolisthesis, or revision fusions. Time series regression models were used to test for significant changes in the use of fusion operation following a major commercial coverage policy change initiated on January 1, 2011.

RESULTS

There was a substantial decline in the use of lumbar fusion for disc herniation or degeneration following the policy change on January 1, 2011. Overall rates of elective lumbar fusion operations in North Carolina (per 100,000 residents) increased from 103.2 in 2005 to 120.4 in 2009, before declining to 101.9 by 2012. The population rate (per 100,000 residents) of fusion among those under age 65 increased from 89.5 in 2005 to 101.2 in 2009, followed by a sharp decline to 76.8 by 2012. There was no acceleration in the already increasing rate of fusion for spinal stenosis, spondylolisthesis, or revision procedures, but there was a coincident increase in decompression without fusion.

CONCLUSION

This commercial insurance policy change had its intended effect of reducing fusion operations for indications with less evidence of effectiveness without changing rates for other indications or resulting in an overall reduction in spine surgery. Nevertheless, broader adoption of the policy could significantly reduce the national rates of fusion operations and associated costs.

LEVEL OF EVIDENCE

3.

A Review of the Clinical Side Effects of Bone Morphogenetic Protein-2

Bone morphogenetic protein-2 (BMP-2) is currently the only Food and Drug Administration (FDA)-approved osteoinductive growth factor used as a bone graft substitute. However, with increasing clinical use of BMP-2, a growing and well-documented side effect profile has emerged. This includes postoperative inflammation and associated adverse effects, ectopic bone formation, osteoclast-mediated bone resorption, and inappropriate adipogenesis. Several large-scale studies have confirmed the relative frequency of adverse events associated with the clinical use of BMP-2, including life-threatening cervical spine swelling. In fact, the FDA has issued a warning of the potential life-threatening complications of BMP-2. This review summarizes the known adverse effects of BMP-2, including controversial areas such as tumorigenesis. Next, select animal models that replicate BMP-2's adverse clinical effects are discussed. Finally, potential molecules to mitigate the adverse effects of BMP-2 are reviewed. In summary, BMP-2 is a potent osteoinductive cytokine that has indeed revolutionized the bone graft substitute market; however, it simultaneously has accrued a worrisome side effect profile. Better understanding of these adverse effects among both translational scientists and clinicians will help determine the most appropriate and safe use of BMP-2 in the clinical setting.

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.

Ectopic bone formation with joint impingement after posterior lumbar fusion with rhBMP-2

Recombinant human bone morphogenetic protein-2 (rhBMP-2) was recently licensed for local administration during posterior lumbar fusion. In this indication, considerable uncertainty remains about the nature and mechanisms of the many adverse effects of rhBMP-2, such as ectopic bone formation. We report a case of ectopic bone formation with impingement on a facet joint and incapacitating low back pain after minimally invasive transforaminal L5-S1 interbody fusion with local application of rhBMP-2 (InductOs(®)). Revision surgery was eventually performed to alleviate the symptoms by removing the ectopic bone. Caution is in order regarding the use of rhBMP-2 during posterior lumbar fusion. Every effort should be made to minimise the risk of complications.

OP-1 Compared with Iliac Crest Autograft in Instrumented Posterolateral Fusion: A Randomized, Multicenter Non-Inferiority Trial

BACKGROUND

Spinal fusion with the use of autograft is a commonly performed procedure. However, harvesting of bone from the iliac crest is associated with complications. Bone morphogenetic proteins (BMPs) are extensively used as alternatives, often without sufficient evidence of safety and efficacy. The purpose of this study was to investigate non-inferiority of osteogenic protein-1 (OP-1, also known as BMP-7) in comparison with iliac crest bone graft in posterolateral fusions.

METHODS

This study was a randomized, controlled multicenter trial. Patients who underwent a single-level instrumented posterolateral fusion of the lumbar spine for degenerative or isthmic spondylolisthesis with symptoms of neurological compression were randomized to receive OP-1 combined with local bone (OP-1 group) or autologous bone graft from the iliac crest combined with local bone (autograft group). The primary outcome was overall success, defined as a combination of clinical success and evidence of fusion on computed tomography (CT) scans, at one year postoperatively.

RESULTS

One hundred and nineteen patients were included in the study, and analysis of the overall outcome was performed for 113. Non-inferiority of OP-1 compared with iliac crest autograft was not found at one year, with a success rate of 40% in the OP-1 group versus 54% in the autograft group (risk difference = -13.3%, 90% confidence interval [CI] = -28.6% to +2.10%). This was due to the lower rate of fusion (the primary aim of OP-1 application) seen on the CT scans in the OP-1 group (54% versus 74% in the autograft group, p = 0.03). There were no adverse events that could be directly related to the use of OP-1.

CONCLUSIONS

OP-1 with a collagen carrier was not as effective as autologous iliac crest bone for achieving fusion and cannot be recommended in instrumented posterolateral lumbar fusion procedures.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Bone morphogenetic protein use in spine surgery-complications and outcomes: a systematic review

PURPOSE

Because of significant complications related to the use of autologous bone grafts in spinal fusion surgery, bone substitutes and growth factors such as bone morphogenetic protein (BMP) have been developed. One of them, recombinant human (rh) BMP-2, has been approved by the Food and Drug Administration (FDA) for use under precise conditions. However, rhBMP-2-related side effects have been reported, used in FDA-approved procedures, but also in off-label use.A systematic review of clinical data was conducted to analyse the rhBMP-2-related adverse events (AEs), in order to assess their prevalence and the associated surgery practices.

METHODS

Medline search with keywords "bone morphogenetic protein 2", "lumbar spine", "anterolateral interbody fusion" (ALIF) and the filter "clinical trial". FDA published reports were also included. Study assessment was made by authors (experienced spine surgeons), based on quality of study designs and level of evidence.

RESULTS

Extensive review of randomised controlled trials (RCTs) and controlled series published up to the present point, reveal no evidence of a significant increase of AEs related to rhBMP-2 use during ALIF surgeries, provided that it is used following FDA guidelines. Two additional RCTs performed with rhBMP-2 in combination with allogenic bone dowels reported increased bone remodelling in BMP-treated patients. This AE was transient and had no consequence on the clinical outcome of the patients. No other BMP-related AEs were reported in these studies.

CONCLUSIONS

This literature review confirms that the use of rhBMP-2 following FDA-approved recommendations (i.e. one-level ALIF surgery with an LT-cage) is safe. The rate of complications is low and the AEs had been identified by the FDA during the pre-marketing clinical trials. The clinical efficiency of rhBMP-2 is equal or superior to that of allogenic or autologous bone graft in respect to fusion rate, low back pain disability, patient satisfaction and rate of re-operations. For all other off-label use, the safety and effectiveness of rhBMP-2 have not been established, and further RCTs with high level of evidence are required.

Enhanced Osteogenesis of Adipose-Derived Stem Cells by Regulating Bone Morphogenetic Protein Signaling Antagonists and Agonists

Although adipose-derived stem cells (ASCs) are an attractive cell source for bone tissue engineering, direct use of ASCs alone has had limited success in the treatment of large bone defects. Although bone morphogenetic proteins (BMPs) are believed to be the most potent osteoinductive factors to promote osteogenic differentiation of ASCs, their clinical applications require supraphysiological dosage, leading to high medical burden and adverse side effects. In the present study, we demonstrated an alternative approach that can effectively complement the BMP activity to maximize the osteogenesis of ASCs without exogenous application of BMPs by regulating levels of antagonists and agonists to BMP signaling. Treatment of ASCs with the amiloride derivative phenamil, a positive regulator of BMP signaling, combined with gene manipulation to suppress the BMP antagonist noggin, significantly enhanced osteogenic differentiation of ASCs through increased BMP-Smad signaling in vitro. Furthermore, the combination approach of noggin suppression and phenamil stimulation enhanced the BMP signaling and bone repair in a mouse calvarial defect model by adding noggin knockdown ASCs to apatite-coated poly(lactic-coglycolic acid) scaffolds loaded with phenamil. These results suggest novel complementary osteoinductive strategies that could maximize activity of the BMP pathway in ASC bone repair while reducing potential adverse effects of current BMP-based therapeutics.

SIGNIFICANCE

Although stem cell-based tissue engineering strategy offers a promising alternative to repair damaged bone, direct use of stem cells alone is not adequate for challenging healing environments such as in large bone defects. This study demonstrates a novel strategy to maximize bone formation pathways in osteogenic differentiation of mesenchymal stem cells and functional bone formation by combining gene manipulation with a small molecule activator toward osteogenesis. The findings indicate promising stem cell-based therapy for treating bone defects that can effectively complement or replace current osteoinductive therapeutics.

Use of Recombinant Human Bone Morphogenetic Protein-2 in the Treatment of Degenerative Spondylolisthesis

STUDY DESIGN

A questionnaire survey.

OBJECTIVE

To report the current use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in lumbar fusion procedures for the treatment of degenerative spondylolisthesis (DS), and identify associated factors including fusion technique, surgeon location, surgeon specialty, or surgeon practice model.

SUMMARY OF BACKGROUND DATA

The prevalence of rhBMP-2 use in fusions increased dramatically from 0.7% in 2002 to 24.7% in 2006, however more recent studies have identified significant complications with its use. Furthermore, an independent review of the industry-sponsored trial data has demonstrated no significant difference in fusion rates or clinical results with the use of rhBMP-2 compared with iliac-crest autograft.

METHODS

In July 2014, a survey was sent requesting information on the usage of rhBMP-2 in the treatment of DS. Determinants included the fusion technique, geographic location, specialty, and associated practice models. No funding was received for this work.

RESULTS

Overall, 7.8% +/- 2.0% of surgeons reported using rhBMP-2 when performing an open L4-L5 posterolateral fusion for DS; 6.2% +/- 1.8% reported using rhBMP-2 for an open L4-L5 interbody fusion, and 12.1% +/- 2.5% reported using rhBMP-2 for a L4-L5 minimally invasive (MIS) interbody fusion. The variables that were statistically associated with the use of rhBMP-2 were North America surgeons (P < 0.0001) and the type of procedure (P = 0.0005).

CONCLUSION

Compared with historical data, there has been a dramatic decrease in the number of surgeons using rhBMP-2 in lumbar fusion procedures for the treatment of DS. Currently, rhBMP-2 is more commonly used by surgeons in North America and those performing MIS interbody fusions.

LEVEL OF EVIDENCE

N/A.

Stem cells, growth factors and scaffolds in craniofacial regenerative medicine

Current reconstructive approaches to large craniofacial skeletal defects are often complicated and challenging. Critical-sized defects are unable to heal via natural regenerative processes and require surgical intervention, traditionally involving autologous bone (mainly in the form of nonvascularized grafts) or alloplasts. Autologous bone grafts remain the gold standard of care in spite of the associated risk of donor site morbidity. Tissue engineering approaches represent a promising alternative that would serve to facilitate bone regeneration even in large craniofacial skeletal defects. This strategy has been tested in a myriad of iterations by utilizing a variety of osteoconductive scaffold materials, osteoblastic stem cells, as well as osteoinductive growth factors and small molecules. One of the major challenges facing tissue engineers is creating a scaffold fulfilling the properties necessary for controlled bone regeneration. These properties include osteoconduction, osetoinduction, biocompatibility, biodegradability, vascularization, and progenitor cell retention. This review will provide an overview of how optimization of the aforementioned scaffold parameters facilitates bone regenerative capabilities as well as a discussion of common osteoconductive scaffold materials.

Postoperative Cyst Associated with Bone Morphogenetic Protein Use in Posterior and Transforaminal Lumbar Interbody Fusion Managed Conservatively: Report of Two Cases

Bone morphogenetic protein use in spinal surgery for off-label indications continues to remain popular. One area where its use has known associated radicular complications is posterior or transforaminal lumbar interbody fusion. These complications include radiculitis, cyst development, and heterotopic ossification, amongst others. Typically, cyst development has been treated surgically. We present two cases of bone morphogenetic protein-related cysts treated medically and thus, present medical treatment as an alternative treatment option.

Ovariectomy-Induced Osteoporosis Does Not Impact Fusion Rates in a Recombinant Human Bone Morphogenetic Protein-2-Dependent Rat Posterolateral Arthrodesis Model

Study Design Randomized, controlled animal study. Objective Recombinant human bone morphogenetic protein-2 (rhBMP-2) is frequently utilized as a bone graft substitute in spinal fusions to overcome the difficult healing environment in patients with osteoporosis. However, the effects of estrogen deficiency and poor bone quality on rhBMP-2 efficacy are unknown. This study sought to determine whether rhBMP-2-induced healing is affected by estrogen deficiency and poor bone quality in a stringent osteoporotic posterolateral spinal fusion model. Methods Aged female Sprague-Dawley rats underwent an ovariectomy (OVX group) or a sham procedure, and the OVX animals were fed a low-calcium, low-phytoestrogen diet. After 12 weeks, the animals underwent a posterolateral spinal fusion with 1 μg rhBMP-2 on an absorbable collagen sponge. Representative animals were sacrificed at 1 week postoperative for alkaline phosphatase (ALP) and osteocalcin serum analyses. The remaining animals underwent radiographs 2 and 4 weeks after surgery and were subsequently euthanized for fusion analysis by manual palpation, micro-computed tomography (CT) imaging, and histologic analysis. Results The ALP and osteocalcin levels were similar between the control and OVX groups. Manual palpation revealed no significant differences in the fusion scores between the control (1.42 ± 0.50) and OVX groups (1.83 ± 0.36; p = 0.07). Fusion rates were 100% in both groups. Micro-CT imaging revealed no significant difference in the quantity of new bone formation, and histologic analysis demonstrated bridging bone across the transverse processes in fused animals from both groups. Conclusions This study demonstrates that estrogen deficiency and compromised bone quality do not negatively influence spinal fusion when utilizing rhBMP-2, and the osteoinductive capacity of the growth factor is not functionally reduced under osteoporotic conditions in the rat. Although osteoporosis is a risk factor for pseudarthrosis/nonunion, rhBMP-2-induced healing was not inhibited in osteoporotic rats.

LIPUS promotes spinal fusion coupling proliferation of type H microvessels in bone

Low-intensity pulsed ultrasound (LIPUS) has been found to accelerate spinal fusion. Type H microvessels are found in close relation with bone development. We analyzed the role of type H vessels in rat spinal fusion model intervened by LIPUS. It was found LIPUS could significantly accelerate bone fusion rate and enlarge bone callus. Osteoblasts were specifically located on the bone meshwork of the allograft, and were surrounded by type H microvessels. LIPUS could significantly increase the quantity of osteoblasts during spine fusion, which process was coupled with elevated angiogenesis of type H microvessels. Our results suggest that LIPUS may be a noninvasive adjuvant treatment modality in spinal fusion for clinical use. The treatment is recommended for usage for at least one month.

Use of Recombinant Bone Morphogenetic Protein Is Associated With Reduced Risk of Reoperation After Spine Fusion for Adult Spinal Deformity

STUDY DESIGN

Retrospective review.

OBJECTIVE

This study follows the inpatient-stay administrative data that were collected for a cohort of thousands of patients who had spine fusion surgery in the state of New York. We sought to examine adult spinal deformity (ASD) for reoperation events with and without the use of bone morphogenetic protein-2 (BMP).

SUMMARY OF BACKGROUND DATA

Randomized controlled trials have suggested that BMP may increase the likelihood of solid arthrodesis in spinal surgery. This would imply fewer reoperations for pseudarthrosis, but small cohort sizes are inadequate to monitor these events.

METHODS

The 2008-2011 New York State Inpatient Database was queried using International Classification of Diseases, Ninth Revision, Clinical Modification codes. Patients age 21 years and older with a diagnosis of scoliosis and an index fusion of greater than 2 spinal motion segments were included. Patient identifiers and linkage variables were used to identify revisits. The relative risk of reoperation was calculated. The use of BMP at the initial inpatient stay was used to define the 2 cohorts for relative risk assessment.

RESULTS

A total of 3751 patients of ASD were identified in 2008. The use of BMP at the initial visit was performed at a rate of 37.6% for ASD. For posterior fusion cases longer than 8 levels, the rate of reoperation for a pseudarthrosis was 23.4%. For ASD fusions greater than 8 levels, the rate of reoperation for pseudarthrosis after using BMP at the index surgery was 5% and 33.9% when BMP was not used, a relative risk of 7.5 (P < 0.001).

CONCLUSION

Using relevant inhospital patient records from the New York State Inpatient Sample, we found a 7.5-fold decrease in the risk of reoperation for pseudarthrosis after long fusions when using BMP. Decreased reoperation rates are caused by the improved fusion with the use of BMP. If subsequent unnecessary hospitals stays can be avoided, the economics of BMP use should be reexamined.

Immediate Effects of Use of Recombinant Bone Morphogenetic Protein in Children Having Spinal Fusion and Refusion Procedures in United States

STUDY DESIGN

Retrospective study of Nationwide Inpatient Sample (NIS).

OBJECTIVE

The objective of this study is to estimate the prevalence of complications in children who had insertion of recombinant human bone morphogenetic protein (rhBMP) at the time of spinal fusion procedures (SFP) and to examine if the use of rhBMP is associated with an increased risk of complications.

SUMMARY OF BACKGROUND DATA

Use of rhBMP for SFP has been associated with conflicting safety profile reports in adults.

METHODS

NIS (years 2004-2010) was used. All patients with age  < 18 years who had a SFP during hospitalization with or without insertion of rhBMP were selected. Complications were selected based on a literature review of studies examining outcomes of SFP. Association between insertion of rhBMP and occurrence of complications was examined by multivariable logistic regression models.

RESULTS

Of the 72,898 children who underwent SFP, 7.1% children had insertion of rhBMP. Overall complication rate was 14.34% (15.2% in rhBMP group and 14.3% in no-rhBMP group). There was no statistically significant difference in the overall complication rate [odds ratio (OR) = 1.08, 95% confidence intervals (CI) = 0.89-1.30] or among 14 different complications between rhBMP and no-rhBMP groups. Children who had rhBMP were associated with higher odds for "other infections" (OR = 2.09, 95% CI = 1.26-3.48, P = 0.004) when compared with their counterparts.

CONCLUSION

Despite the lack of Food and Drug Administration approval, rhBMP was not infrequently used in pediatric SFP. In this large retrospective study using administrative data, the use of rhBMP in children during SFP was not associated with higher risks for majority of assessed complications with the exception of "other infections". Future studies must examine the long-term impact of use of rhBMP in children with SFP.

LEVEL OF EVIDENCE

3.

Review of various treatment options and potential therapies for osteonecrosis of the femoral head

Size and location of the lesion, subchondral collapse occurrence, and articular cartilage involvement are general disease progression criteria for direct osteonecrosis of the femoral head (ONFH) classifications. Treatment options for ONFH are usually based on individual factors and lesion characteristics. Although spontaneous repair of ONFH occurs in some cases, untreated ONFH is unlikely to escape the fate of subchondral collapse and usually ends up with total hip arthroplasty. Operations to preserve the femoral head, e.g., core decompression and bone grafting, are usually recommended in younger patients. They are helpful to relieve pain and improve function in the affected femoral head without subchondral collapse, however, poor prognosis after surgical procedures remains the major problem for ONFH. Pharmacological and physical therapies only work in the early stage of ONFH and have also been recommended as a supplement or prevention treatment for osteonecrosis. Following advances in basic science, many new insights focus on bone tissue engineering to optimize therapies and facilitate prognosis of ONFH. In this review, disease classifications, current treatment options, potential therapies, and the relevant translational barriers are reviewed in the context of clinical application and preclinical exploration, which would provide guidance for preferable treatment options and translation into novel therapies.

Database and Registry Research in Orthopaedic Surgery: Part I: Claims-Based Data

The use of large-scale national databases for observational research in orthopaedic surgery has grown substantially in the last decade, and the data sets can be grossly categorized as either administrative claims or clinical registries. Administrative claims data comprise the billing records associated with the delivery of health-care services. Orthopaedic researchers have used both government and private claims to describe temporal trends, geographic variation, disparities, complications, outcomes, and resource utilization associated with both musculoskeletal disease and treatment. Medicare claims comprise one of the most robust data sets used to perform orthopaedic research, with >45 million beneficiaries. The U.S. government, through the Centers for Medicare & Medicaid Services, often uses these data to drive changes in health policy. Private claims data used in orthopaedic research often comprise more heterogeneous patient demographic samples, but allow longitudinal analysis similar to that offered by Medicare claims. Discharge databases, such as the U.S. National Inpatient Sample, provide a wide national sampling of inpatient hospital stays from all payers and allow analysis of associated adverse events and resource utilization. Administrative claims data benefit from the high patient numbers obtained through a majority of hospitals. Using claims, it is possible to follow patients longitudinally throughout encounters irrespective of the location of the institution delivering health care. Some disadvantages include lack of precision of ICD-9 (International Classification of Diseases, Ninth Revision) coding schemes. Much of these data are expensive to purchase, complicated to organize, and labor-intensive to manipulate--often requiring trained specialists for analysis. Given the changing health-care environment, it is likely that databases will provide valuable information that has the potential to influence clinical practice improvement and health policy for years to come.

Does Patient Sex Affect the Rate of Mortality and Complications After Spine Surgery? A Systematic Review

BACKGROUND

Available studies disagree regarding the influence of patient sex on mortality and complications after spine surgery. We sought to conduct a systematic review and pool the results of existing research to better understand this issue.

QUESTIONS/PURPOSES

We performed a systematic review to address two questions: (1) Does sex (male versus female) influence mortality after spine surgery? (2) Does sex impact the development of postoperative complications after spine surgery?

METHODS

This systematic review was performed through a query of PubMed using a structured search algorithm. Additional queries of Embase, SCOPUS, Web of Science, and the tables of contents of orthopaedic and neurosurgical journals were also conducted using search terms such as "sex factors", "male or female", "risk factors", and "spine surgery". Selected papers were independently abstracted by three of the authors (AJS, ENR, EIW) and pooling was performed. Our literature search returned 720 studies, of which 99 underwent full review. Of these, 50 were selected for final abstraction. The Cochrane Q test was used to assess study heterogeneity; significant study heterogeneity was present and so a random-effects model was used. A Harbord test was used to evaluate for the presence of publication bias; this analysis found no statistically significant evidence of publication bias.

RESULTS

Males were at increased odds of mortality after spine surgery (odds ratio [OR], 1.63; 95% confidence interval [CI], 1.35-1.97; p<0.001). No differences between the sexes were identified for the odds of complications (OR, 1.04; 95% CI, 0.95-1.13; p=0.42).

CONCLUSIONS

Our results determined that males were at elevated odds of mortality but not of complications after spine surgery. These results should be used to inform preoperative discussion and decision-making at the time of surgical consent. Future work should be directed at determining the underlying factors responsible for increased mortality among males and prospective studies specifically designed to evaluate sex-based differences in outcomes after spine surgery.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Synergy between IL-6 and soluble IL-6 receptor enhances bone morphogenetic protein-2/absorbable collagen sponge-induced bone regeneration via regulation of BMPRIA distribution and degradation

Bone morphogenetic protein-2/absorbable collagen sponge (BMP-2/ACS) implants have been approved for clinical use to induce bone regeneration. We previously showed that exaggerated inflammation characterized by elevated level of inflammatory cytokines including TNF-α, IL-1β, and IL-6 has been shown to inhibit BMP-2/ACS-induced bone regeneration. Furthermore, unlike the negative effects of TNF-α and IL-1β, IL-6 seemed not to affect BMP-2-induced osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs). We hypothesized that there may be a regulatory loop between IL-6 and BMP-2 singling to affect BMP-2/ACS-induced bone regeneration. Here, we established a BMP-2/ACS-induced ectopic bone formation model in rats and fund that IL-6 injection significantly increased BMP-2/ACS-induced bone mass. Consistent with this animal model, an in vitro study demonstrated that synergy between IL-6 and soluble IL-6 receptor (IL-6/sIL-6R) promotes BMP-2-induced osteoblastic differentiation of human BMSCs through amplification of BMP/Smad signaling. Strikingly, IL-6 injection did not activate osteoclast-mediated bone resorption in the ectopic bone formation model, and IL-6/sIL-6R treatment did not affect receptor activator of NF-κB ligand (RANKL)-induced osteoclastic differentiation of human peripheral blood mononuclear cells (PBMCs) in vitro. Furthermore, IL-6/sIL-6R treatment did not affect expression of BMP receptors, but enhanced the cell surface translocation of BMP receptor IA (BMPRIA) and inhibited the degradation of BMPRIA. Collectively, these findings indicate that synergy between IL-6 and sIL-6R promotes the cell surface translocation of BMPRIA and maintains the stability of BMPRIA expression, leading to enhanced BMP-2/ACS-induced bone regeneration.

Dual Delivery of EPO and BMP2 from a Novel Modular Poly-ɛ-Caprolactone Construct to Increase the Bone Formation in Prefabricated Bone Flaps

Poly-ɛ-caprolactone (PCL) is a biocompatible polymer that has mechanical properties suitable for bone tissue engineering; however, it must be integrated with biologics to stimulate bone formation. Bone morphogenetic protein-2 (BMP2) delivered from PCL produces bone when implanted subcutaneously, and erythropoietin (EPO) works synergistically with BMP2. In this study, EPO and BMP2 are adsorbed separately on two 3D-printed PCL scaffold modules that are assembled for codelivery on a single scaffold structure. This assembled modular PCL scaffold with dual BMP2 and EPO delivery was shown to increase bone growth in an ectopic location when compared with BMP2 delivery along a replicate scaffold structure. EPO (200 IU/mL) and BMP2 (65 μg/mL) were adsorbed onto the outer and inner portions of a modular scaffold, respectively. Protein binding and release studies were first quantified. Subsequently, EPO+BMP2 and BMP2 scaffolds were implanted subcutaneously in mice for 4 and 8 weeks, and the regenerated bone was analyzed with microcomputed tomography and histology; 8.6±1.4 μg BMP2 (22%) and 140±29 IU EPO (69.8%) bound to the scaffold and <1% BMP2 and 83% EPO was released in 7 days. Increased endothelial cell proliferation on EPO-adsorbed PCL discs indicated protein bioactivity. At 4 and 8 weeks, dual BMP2 and EPO delivery regenerated more bone (5.1±1.1 and 5.5±1.6 mm(3)) than BMP2 alone (3.8±1.1 and 4.3±1.7 mm(3)). BMP2 and EPO scaffolds had more ingrowth (1.4%±0.6%) in the outer module when compared with BMP2 (0.8%±0.3%) at 4 weeks. Dual delivery produced more dense cellular marrow, while BMP2 had more fatty marrow. Dual EPO and BMP2 delivery is a potential method to regenerate bone faster for prefabricated flaps.

Polyelectrolyte Complex Carrier Enhances Therapeutic Efficiency and Safety Profile of Bone Morphogenetic Protein-2 in Porcine Lumbar Interbody Fusion Model

STUDY DESIGN

Porcine lumbar interbody fusion model.

OBJECTIVE

This study evaluates the effect of polyelectrolyte complex (PEC) carrier in enhancing the therapeutic efficiency and safety profile of bone morphogenetic protein-2 (BMP-2) in a large animal model.

SUMMARY OF BACKGROUND DATA

Extremely large amounts of BMP-2 are administered to achieve consistent spinal fusion, which has led to complications. Heparin-modified PEC carrying reduced BMP-2 doses of 0.5 μg was demonstrated to achieve consistent spinal fusion with reduction of complications in rodent model. The purpose of this study was to evaluate whether PEC could improve the therapeutic efficiency of BMP-2 in porcine model.

METHODS

Three-segment (L3-L6) anterior lumbar interbody fusions with instrumentation were performed on 6 pigs using 3 different doses of BMP-2, namely, (1) 50 μg, (2) 150 μg, and (3) 300 μg. The BMP-2 was delivered using heparin-modified alginate microbeads loaded into biodegradable cage. Fusion performance was evaluated after 3 months.

RESULTS

Manual palpation and micro-computed tomography showed consistent fusion in all experimental groups. Heterotopic bone formation beyond the cage implant area was more evident in group 2 and group 3 than in group 1. Similarly, superior bone microstructure was observed in the new bone with the lowered BMP-2 dose. Biomechanical evaluation revealed enhanced stiffness of the operated segments compared with nonoperated segments (P < 0.05). Mechanical stability was maintained despite dose reduction of BMP-2. Although the mineral apposition rate was higher in group 3, unsatisfactory bony microstructure with decreased trabecular number was observed in group 3 compared with group 1.

CONCLUSION

PEC carrying low doses of BMP-2 achieved consistent interbody fusion. We observed dose-related reduction in heterotopic ossification without compromising the stability of the fused segments. PEC carrier reduces the efficacious doses of BMP-2. This could enhance the safety profile of BMP-2 and reduce dose- and carrier-related complications.

LEVEL OF EVIDENCE

N/A.

Routine use of recombinant human bone morphogenetic protein-2 in posterior fusions of the pediatric spine and incidence of cancer

OBJECT The aim of this study was to determine the safety of recombinant human bone morphogenetic protein-2 (rhBMP-2) use in posterior instrumented fusions in the pediatric population, focusing on cancer risk. In a previous study, the authors reported the short-term (mean follow-up of 11 months) safety and efficacy of rhBMP-2 in the pediatric age group. The present study reports their results with a minimum of 24 months' follow-up. METHODS The authors retrospectively reviewed 57 consecutive cases involving pediatric patients who underwent posterior occiptocervical, cervical, thoracic, lumbar, or lumbosacral spine fusion from October 1, 2007, to June 30, 2011, at Texas Children's Hospital. Seven cases were excluded from further analysis because of loss to follow-up. Three patients died during the follow-up period and were placed in a separate cohort. RESULTS The patients' average age at the time of surgery was 11 years, 4 months (range 9 months to 20 years). The mean duration of follow-up was 48.4 months (range 24-70 months). Cancer status was determined at the most recent encounter with the patient and/or caretaker(s) in person, or in telephone follow-up. Twenty-four or more months after administration of rhBMP-2, there were no cases of new malignancy, degeneration, or metastasis of existing tumors. The cause of death of the patients who died during the study period was not related to BMP or to the development, degeneration, or metastasis of cancer. CONCLUSIONS Despite the large number of adult studies reporting increased cancer risk associated with BMP use, the authors' outcomes with rhBMP-2 in the pediatric population suggest that it is a safe adjunct to posterior spine fusions of the occipitocervical, cervical, thoracic, lumbar, and lumbosacral spine. There were no new cases of cancer, or degeneration or metastasis of existing malignancies in this series.

Initial Experience With a New Intraoral Midface Distraction Device

Maxillary hypoplasia that necessitates surgical advancement affects approximately 25% of patients born with cleft lip and palate. Syndromic conditions such as Crouzon may also be accompanied by significant maxillary hypoplasia. Severe maxillary hypoplasia can result in airway obstruction, malocclusion, proptosis, and facial disfigurement. For optimal stability, severe hypoplasia is best addressed with maxillary distraction osteogenesis. Twenty-two patients (15 boys, 7 girls, ages 6–16 years, mean age 10 years) with severe midface hypoplasia underwent midface distraction with new internal maxillary distraction (IMD) device at our institution. Total distraction distances ranged from 15 to 30 mm. There were no major complications, and all of them had improvement in functional and aesthetic parameters. There were 2 minor complications and 2 patients failed to distract the full distance because of converging vectors. Early maxillary distraction in patients with severe midface hypoplasia is a useful technique to provide interval correction of severe maxillary hypoplasia before skeletal maturity and definitive orthognathic surgery is contemplated, and it is a good tool to improve occlusion, aesthetics, and self-perception in younger patients.

The bone morphogenetic protein-2/7 heterodimer is a stronger inducer of bone regeneration than the individual homodimers in a rat spinal fusion model

BACKGROUND CONTEXT

Bone morphogenetic proteins (BMPs) are a group of dimeric growth factors that belong to the transforming growth factor super family and are capable of eliciting new bone formation. Previous studies have suggested that the coexpression of two different BMP genes in a cell can result in the production of BMP heterodimers that are more potent than homodimers. However, because of the difficulty in optimizing the level of BMP gene expression, the coexpression of two different BMP genes also produces BMP homodimers as a by-product. These homodimers could, in theory, interact with the heterodimers.

PURPOSE

To elucidate the effects of a BMP-2/7 heterodimer, which were investigated in depth using purified BMP-2/7 heterodimers, BMP-2 homodimers, and BMP-7 homodimers in a rat spinal fusion model.

METHODS

Bilateral posterolateral fusion at L4-L5 was performed in four different groups: control group animals were implanted with collagen carriers alone; BMP-7 group animals with collagen carriers+1 μg of BMP-7 homodimer; BMP-2 group animals with collagen carriers+1 μg of BMP-2 homodimer; and BMP-2/7 group animals with collagen carriers+1 μg of the BMP-2/7 heterodimer. The following assessments were performed: bone microstructural analysis of the fusion mass and tissue volume (TV) with microcomputed tomography (micro-CT); fusion assessment with manual palpation testing and three-dimensional CT images; and bone histomorphometrical analysis of the fusion mass.

RESULTS

The fusion scores, as determined by radiography, and the TV of the newly formed bone, as determined by micro-CT, were significantly higher in the BMP-2/7 heterodimer group than the other groups (p<.0001). The microstructural indices of the newly formed bone did not differ between the groups. Moreover, histologic analysis of the fused spines revealed that the formation of the trabecular bone bridging the transverse process was the highest in this group.

CONCLUSIONS

This study demonstrated that BMP-2/7 heterodimer is a stronger inducer of bone regeneration than BMP-2 or -7 homodimers. The use of a purified BMP-2/7 heterodimer may represent an efficient alternative to the current clinical use of BMP-2 or -7 homodimers. Further studies as to the side effects of BMP-2/7 heterodimer are required.

The collagen I mimetic peptide DGEA enhances an osteogenic phenotype in mesenchymal stem cells when presented from cell-encapsulating hydrogels

Interactions between cells and the extracellular matrix (ECM) are known to play critical roles in regulating cell phenotype. The identity of ECM ligands presented to mesenchymal stem cells (MSCs) has previously been shown to direct the cell fate commitment of these cells. To enhance osteogenic differentiation of MSCs, alginate hydrogels were prepared that present the DGEA ligand derived from collagen I. When presented from hydrogel surfaces in 2D, the DGEA ligand did not facilitate cell adhesion, while hydrogels presenting the RGD ligand derived from fibronectin did encourage cell adhesion and spreading. However, the osteogenic differentiation of MSCs encapsulated within alginate hydrogels presenting the DGEA ligand was enhanced when compared with unmodified alginate hydrogels and hydrogels presenting the RGD ligand. MSCs cultured in DGEA-presenting gels exhibited increased levels of osteocalcin production and mineral deposition. These data suggest that the presentation of the collagen I-derived DGEA ligand is a feasible approach for selectively inducing an osteogenic phenotype in encapsulated MSCs.

Trends analysis of rhBMP utilization in single-level posterior lumbar fusion (PLF) in the United States

PURPOSE

A retrospective database review was carried out to evaluate the trends and demographics of rhBMP utilization in single-level posterior lumbar fusion (PLF) in the United States.

METHODS

Patients who underwent single-level PLF 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, USA), a national database of orthopaedic 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

Totally 5158 patients had single-level PLF in this study. The average rate of single-level PLF with rhBMP utilization maintained at a relatively stable level (19.1-23.5%) from 2005 to 2009, but sharply decreased to 6.8% in 2010 and 6.9% in 2011. The overall incidence of single-level PLF without rhBMP (1.37 cases per 100,000 patients) was more than five times of the incidence of single-level PLF with rhBMP (0.27 cases per 100,000 patients) (P < 0.01). The average rate of single-level PLF with rhBMP utilization is highest in Midwest (18.7%), followed by West (18.4%), South (16.4%) and Northeast (11.5%). The highest incidence of single-level PLF with rhBMP was observed in the group aged 70-74 years with an incidence of 0.33 per 100,000 patients.

CONCLUSIONS

The incidence of rhBMP utilization in single-level PLF increased from 2006 to 2009, but dropped to a low level in 2010 and 2011. The Northeast region had the lowest incidence of rhBMP utilization. The group aged 70-74 years trended to have the higher incidence of single-level PLF with rhBMP utilization.

Delivery of Phenamil Enhances BMP-2-Induced Osteogenic Differentiation of Adipose-Derived Stem Cells and Bone Formation in Calvarial Defects

Bone morphogenetic proteins (BMPs) have been widely used for bone repair in the craniofacial region. However, its high dose requirement in clinical applications revealed adverse effects and inefficient bone formation, along with high cost. Here, we report a novel osteoinductive strategy to effectively complement the osteogenic activity of BMP-2 using phenamil, a small molecule that can induce osteogenic differentiation via stimulation of BMP signaling. Treatment of adipose-derived stem cells (ASCs) with BMP-2 in combination with phenamil significantly promoted the in vitro osteogenic differentiation of ASCs. The efficacy of the combination strategy of phenamil+BMP-2 was further confirmed in a mouse calvarial defect model using scaffolds consisting of poly(lactic-co-glycolic acid) and apatite layer on their surfaces designed to slowly release phenamil and BMP-2. Six weeks after implantation, the scaffolds treated with phenamil+BMP-2 significantly promoted mouse calvarial regeneration as demonstrated by micro-computerized tomography and histology, compared with the groups treated with phenamil or BMP-2 alone. Moreover, the combination treatment reduced the BMP-2 dose without compromising calvarial healing efficacy. These results suggest promising complementary therapeutic strategies for bone repair in more efficient and cost-effective manners.