Complications with recombinant human bone morphogenic protein-2 in posterolateral spine fusion: a consecutive series of 1037 cases

Translational Experimental Basis of Indirect Adenosine Receptor Agonist Stimulation for Bone Regeneration: A Review

Bone regeneration remains a significant clinical challenge, often necessitating surgical approaches when healing bone defects and fracture nonunions. Within this context, the modulation of adenosine signaling pathways has emerged as a promising therapeutic option, encouraging osteoblast activation and tempering osteoclast differentiation. A literature review of the PubMed database with relevant keywords was conducted. The search criteria involved in vitro or in vivo models, with clear methodological descriptions. Only studies that included the use of indirect adenosine agonists, looking at the effects of bone regeneration, were considered relevant according to the eligibility criteria. A total of 29 articles were identified which met the inclusion and exclusion criteria, and they were reviewed to highlight the preclinical translation of adenosine agonists. While preclinical studies demonstrate the therapeutic potential of adenosine signaling in bone regeneration, its clinical application remains unrealized, underscoring the need for further clinical trials. To date, only large, preclinical animal models using indirect adenosine agonists have been successful in stimulating bone regeneration. The adenosine receptors (A1, A2A, A2B, and A3) stimulate various pathways, inducing different cellular responses. Specifically, indirect adenosine agonists act to increase the extracellular concentration of adenosine, subsequently agonizing the respective adenosine receptors. The agonism of each receptor is dependent on its expression on the cell surface, the extracellular concentration of adenosine, and its affinity for adenosine. This comprehensive review analyzed the multitude of indirect agonists currently being studied preclinically for bone regeneration, discussing the mechanisms of each agonist, their cellular responses in vitro, and their effects on bone formation in vivo.

Current Trends in Recombinant Human Bone Morphogenetic Protein 2 (rhBMP2) Usage for Spinal Fusion Surgery

(1) Background: Since first approved by the FDA, on-label and off-label usage of recombinant human bone morphogenetic protein 2 (rhBMP2) for spinal fusion surgeries has become widespread. While many studies have investigated the safety and efficacy of its use, as well as its economic impact, few have looked at the current trends in its on- and off-label use. The goal of this study is to evaluate the current trends of on- and off-label rhBMP2 use for spinal fusion surgery. (2) Methods: A deidentified survey was created and electronically distributed to members of two international spine societies. Surgeons were asked to report their demographic information, surgical experience, and current usage of rhBMP2. They were then presented with five spinal fusion procedures and asked to report if they use rhBMP2 for these indications in their current practice. Responses were stratified between rhBMP2 users vs. non-users and on-label vs. off-label use. Data were analyzed using chi-square with Fisher's exact test for categorical data. (3) Results: A total of 146 respondents completed the survey with a response rate of 20.5%. There was no difference in overall rhBMP2 usage based on specialty, experience, or number of cases per year. Fellowship-trained surgeons and those who practice in the United States were more likely to use rhBMP2. Surgeons who were trained in the Southeast and Midwest regions reported the highest usage rates. rhBMP2 use was more common among fellowship-trained and US surgeons for ALIFs; non-US surgeons for multilevel anterior cervical discectomy and fusions; and fellowship-trained and orthopedic spine surgeons for lateral lumbar interbody fusions. Non-US surgeons were more likely to use rhBMP2 for off-label indications compared to surgeons from the US. (4) Conclusions: While various demographics of surgeons report different rates of rhBMP2 use, off-label use remains relatively commonplace amongst practicing spine surgeons.

Use of Recombinant Human Bone Morphogenetic Protein-2 With Iliac Crest Bone Graft Instead of Iliac Crest Bone Graft Alone in Lumbar Spondylolysis

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to evaluate the clinical and radiographic effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) in pars repair of lumbar spondylolysis.

SUMMARY OF BACKGROUND DATA

BMP-2 is a growth factor that plays a role in the formation of bone and promotes bone healing. However, few studies of using rhBMP-2 in pars repair have been reported.

METHODS

Direct pars repair and pedicle screw fixation was performed, which were added with 1 mg of rhBMP-2 and iliac crest bone graft in the study group (rhBMP-2 group, n=32) and iliac crest bone graft alone in the autograft group (n=36). Patients completed the visual analog scale and the Oswestry Disability Index preoperation, 3, 6, and 12 months after the operation. Computed tomography scans with axial and sagittal reconstructions were performed at 6, 9, 12, 18, and 24 months postoperatively.

RESULTS

Baseline demographic data showed no significant difference between 2 groups. There were significant differences for the Oswestry Disability Index score at 3 and 6 months postoperatively, which were higher in the autograft group. There was no significant difference between the groups with respect to the overall union status. As for union speed, the trabecular bone appeared earlier and union rates were higher in rhBMP-2 group than in the autograft group at 9, and 12 months postoperatively. No complications were identified in either group. One case in the rhBMP-2 group and 2 cases in the autograft group underwent revision surgery.

CONCLUSION

Compared with iliac crest bone graft alone, the use of rhBMP-2 can accelerate fusion in pars repair for young patients with spondylolysis. The union rates were significantly different at 9 and 12 months after surgery. This study showed no clinical difference when adding rhBMP-2 compared with iliac crest bone graft alone.

Characterizing the host response to rhPDGF-BB in a rat spinal arthrodesis model

BACKGROUND

Due to the constraints surrounding autograft bone, surgeons have turned to osteoinductive agents to augment spinal fusion. Reports of complications and questionable efficacy slowed the adoption of these alternatives. Recombinant human platelet-derived growth factor B homodimer (rhPDGF-BB) has been Food and Drug Administration (FDA)-approved (Augment) to promote fusion in other areas of orthopedics, but its characterization in spine fusion has not yet been tested. The purpose of this study is to characterize the host response to PDGF-BB in vivo.

METHODS

Eighty female Fischer rats underwent L4-5 posterolateral fusion using one of four implant types: (a) iliac crest syngeneic allograft harvested from syngeneic donors, (b) β-TCP/bovine collagen matrix (β-TCP/Col) with sodium acetate buffer, (c) β-TCP/Col with 0.3 mg/mL "low dose," or (d) β-TCP/Col with 3.0 mg/mL "high dose" of rhPDGF-BB. Animals underwent magnetic resonance imaging (MRI) and serum cytokine quantification at 4, 7, 10, and 21 days, postoperatively. Tissues were processed for immunofluorescence staining for Ki67 and von Willebrand factor (vWF) to assess neovascularization.

RESULTS

MRI demonstrated no differences in fluid accumulation among the four treatment groups at any of the time points. Serum cytokine analysis showed no clinically significant differences between treatment groups in 20 of the 27 cytokines. Inflammatory cytokines IFN-γ, IL-1β, IL-18, MCP-1, MIP-1α, TNF-α were not induced by rhPDGF-BB. Histology showed no differences in cell infiltration, and Ki67 and vWF immunofluorescence staining was similar among groups.

CONCLUSIONS

rhPDGF-BB delivered with a β-TCP/Col matrix exerts no exaggerated systemic or local host inflammatory response when compared to iliac crest syngeneic allograft bone or the control carrier. rhPDGF-BB mixed with a β-TCP/Col matrix could be a viable and safe biologic alternative to syngeneic allograft in spine fusion. Further studies need to be performed to evaluate efficacy in this setting.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

Effect of Bone Powder/Mesenchymal Stem Cell/BMP2/Fibrin Glue on Osteogenesis in a Mastoid Obliteration Model

BACKGROUND/AIM

This study aimed to prospectively compare the osteogenesis of bone powder (BP) substances with and without mesenchymal stem cells (MSCs) and evaluate the synergistic effect of topically applied recombinant human bone morphogenic protein-2 (BMP2) on MSC-loaded BP using fibrin glue in a mastoid obliteration model.

MATERIALS AND METHODS

To determine the expression of osteocyte-specific genes, total RNA was isolated from three MSC groups: Untreated MSCs, MSCs cultured with BP, and MSCs cultured with BP and BMP2. Real-time polymerase chain reaction was carried out with specific primers of osteogenesis-related genes runt-related transcription factor 2, osteocalcin, osteoprotegerin, osterix, alkaline phosphatase, transforming growth factor beta, and type I collagen. Live/dead staining was also performed. To observe the adhesion of MSCs to the BP, MSCs were treated with BP for 2 days and the surface was observed by scanning electron microscopy (SEM). Under general anesthesia, mastoid obliteration was performed in rats using three groups: treated with BP alone, BP/MSCs, and BP/MSC/BMP2. Before decapitation at 8 weeks post operation, in vivo micro computed tomography (micro CT) was performed. The bullae were dissected, fixed, and decalcified. followed by dehydration, paraffin embedding, and staining by hematoxylin and eosin and Masson's trichrome.

RESULTS

SEM showed the MSCs to be well-attached to the superficial area of the BP. The expression of osteocyte-specific genes was the highest in the MSCs cultured with BP and BMP2, followed by cultured with BP only, and untreated MSCs. The BP/MSC/BMP2 group showed the highest radiodensity of bullae in microCT analysis. The microCT findings revealed that the BP/MSC/BMP2 group showed the most enhanced osteogenesis of the scaffold compared to the other two groups. No significant difference was found in osteoconductive osteogenesis between the control and BP/MSC groups. However, the BP/MSC/BMP2 group showed significantly enhanced osteoconductive osteogenesis and osteoinductive change of the BP as shown by hematoxylin and eosin staining. Histomorphometry of osteogenesis revealed that the difference between the BP/MSC/BMP2 group and the other two groups was statistically significant.

CONCLUSION

A small amount of BMP2 is necessary during MSC loading to enhance the osteogenesis of BP and avoid complications associated with high doses of BMP2. These results may be applicable to mastoid obliteration in clinical practice.

Effect of preoperative symptom duration on outcome in lumbar spinal stenosis: a Canadian Spine Outcomes and Research Network registry study

BACKGROUND CONTEXT

Lumbar degenerative stenosis is one of the most common spine pathologies for which surgical intervention is indicated. There is some evidence that a prolonged duration of neurological compression could lead to a failure of surgery to alleviate symptoms.

PURPOSE

Determination of whether longer symptom duration was associated with worse postoperative disability outcomes after decompressive surgery for lumbar degenerative stenosis.

STUDY DESIGN/SETTING

The Canadian Spine Outcomes and Research Network (CSORN) prospective database includes pre- and postoperative data from 18 tertiary care hospitals.

PATIENT SAMPLE

The CSORN database was queried for all cases of degenerative lumbar stenosis receiving surgical decompression for neurogenic claudication or radiculopathy. Patients with tumor, infection, fracture, or previous surgery were excluded. Patients were divided into groups based on symptom duration (<6 weeks, 6-12 weeks, 3-6 months, 6-12 months, 1-2 years, and >2 years).

OUTCOME MEASURES

Change between preoperative and 12-month postoperative Oswestry Disability Index (ODI) was compared between symptom duration groups. Secondary outcomes included SF12 physical component score (PCS), and numeric rating scales for leg and back pain. Outcomes were also assessed at 3 months and 24 months postoperatively.

METHODS

Change in ODI, and secondary outcome measures, were compared between different symptom duration groups. Multiple regression analysis was used to identify factors interacting with symptom duration to predict change in ODI.

RESULTS

Four hundred and seventy-eight cases of lumbar stenosis with 12-month postoperative data were identified. Longer symptom duration correlated with less improvement in ODI (p<.001). Patients with >1 year of symptoms were less likely to achieve a Minimal Clinically Significant Difference in ODI (54.4% vs. 66.1%; p=.03) and were more likely to experience no improvement or worse disability, postoperatively (22.1% vs. 11.3%; p=.008). Similar results were found at 3- and 24-month timepoints. Smaller postoperative improvements in SF12 PCS and leg pain scales were also correlated with longer symptom duration (p<.05).

CONCLUSIONS

Multicenter registry data provides important real-world evidence to guide consent, surgical planning, and health resource management. Longer symptom duration was found to correlate with less improvement in pain and disability after lumbar stenosis surgery suggesting that these patients may benefit from earlier treatment.

A Computed Tomography Analysis of the Success of Spinal Fusion Using Ultra-Low Dose (0.7 mg per Facet) of Recombinant Human Bone Morphogenetic Protein 2 in Multilevel Adult Degenerative Spinal Deformity Surgery

Study Design

Retrospective cohort study.

Purpose

To report on spinal fusion assessment using computed tomography (CT) after adult spinal deformity (ASD) surgery using ultra-low dose recombinant human bone morphogenetic protein 2 (RhBMP-2).

Overview of Literature

The reported dose of RhBMP-2 needed for successful spinal posterolateral fusion in ASD ranges from 10 to 20 mg per spinal level. This study reports the use of ultra-low dose of RhBMP-2 (0.07 mg per facet) to achieve spinal fusion in multilevel ASD surgery.

Methods

Consecutive patients who underwent ASD surgery using ultra-low dose RhBMP-2 were recruited. Routine postoperative CT analysis for spinal fusion was performed by two spine surgeons. Inter-observer agreement was calculated for facet fusion (FF) and interbody fusion (IBF) at 6 and 12 months after the procedure.

Results

Six consecutive ASD patients with a mean age of 62 years (28–72 years) were examined. Each patient received a total dose of 12 mg with an average dose of 0.69±0.2 mg (0.42–1 mg) per single FF and 1.38±0.44 mg (0.85–2 mg) for IBF. Total 131 FF and 15 IBF were examined in the study, with 88 FFs and nine IBFs being analyzed specifically at 6 months after the surgery. FF and IBF reported by surgeons A and B at 6 months were 97.7% vs. 91.9% FF, respectively (κ=0.95) and 100% vs. 100% IBF, respectively (κ=1). Two patients underwent longitudinal follow-up CT at 12 months, and the FF rates reported by surgeons A and B were 100% vs. 95.8%, respectively (κ=0.96). Five out of nine facet (56%) non-unions were identified at the cross-links. The remaining four facet pseudarthrosis were noted at 1–2 spinal levels caudal to the cross-links. At the final clinical follow-up, there was no rod breakage, deformity progression, neurological deficit, or symptom recurrence. The Oswestry Disability Index improved by an average of 32.8±6.3, while the mental component summary of the 36-item Short-Form Health Survey improved by an average of 4.7±2.1, and physical component summary improved by an average of 10.5±2.1.

Conclusions

To our knowledge, this is the first study to report a CT that defined 92%–98% FF and 100% IBF using the lowest reported dose of RhBMP-2 in multilevel ASD surgery. The use of ultra-low dose RhBMP-2 reduces the RhBMP-2 related complications and healthcare costs.

Combined delivery of bone morphogenetic protein-2 and insulin-like growth factor-1 from nano-poly (γ-glutamic acid)/β-tricalcium phosphate-based calcium phosphate cement and its effect on bone regeneration in vitro

In this study, nano-doped calcium phosphate cement delivery systems (poly (γ-glutamic acid)/β-tricalcium phosphate/calcium phosphate ceramics and nano (γ-glutamic acid)/β-tricalcium phosphate/calcium phosphate ceramic) were fabricated, and low doses (10 µg/g) of two growth factors, insulin-like growth factor-1 and bone morphogenetic protein-2, were encapsulated then sequentially released. We characterized the delivery systems using Fourier transform infrared spectroscopy and X-ray diffraction and measured washout resistance and compressive strength, and thus optimized the most appropriate proportioning of delivery systems for the two growth factors. One of the growth factors was absorbed by the nano-poly (γ-glutamic acid)/β-tricalcium phosphate, which was then mixed into the calcium phosphate ceramic solid phase to create a new solid phase calcium phosphate ceramic. Nano-poly (γ-glutamic acid)/β-tricalcium phosphate/calcium phosphate ceramic carriers were then prepared by blending the new calcium phosphate ceramic solid phase powder with a solution of the remaining growth factor. The effects of different release patterns (studying sequential behavior) of insulin-like growth factor-1 and bone morphogenetic protein-2 on osteogenic proliferation and differentiation of the MC3t3-E1 mouse osteoblast cell were investigated. This combinational delivery system provided a controlled release of the two growth factors, in which nano-doping significantly affected their release kinetics. The incorporation of dual growth factors could potentially stimulate bone healing and promoting bone ingrowth processes at a low dose.

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.

Bone Morphogenetic Protein Usage in Anterior Lumbar Interbody Fusion: What Else Can Go Wrong?

BACKGROUND

Bone morphogenetic protein (BMP) graft showed promising outcome during early phases of its use. However, unreported adverse events and off-label use shattered its safe profile and raised concerns regarding its indication. In 2008 the U.S. Food and Drug Administration prohibited its use in anterior cervical spine procedures due to the possibility of edema, hematoma, and need to intubate. At the molecular level, BMPs act as multifactorial growth factors playing a role in cartilage, heart, and bone formation. However, its unfavorable effect on bone overgrowth or heterotopic ossification post spine surgeries has been described. Reported cases in the literature were limited to epidural bone formation.

CASE DESCRIPTION

We present a rare and interesting case of a 59-year-old female, in whom BMP caused intradural bone growth several years after an anterior lumbar interbody fusion surgery.

CONCLUSION

Caution must be exercised while using BMPs because of inadvertent complications.

Complication Rates in Posterior Lumbar Interbody Fusion (PLIF) Surgery With Human Bone Morphogenetic Protein 2: Medicare Population

STUDY DESIGN

Retrospective cohort study among Medicare beneficiaries who underwent posterior lumbar interbody fusion (PLIF) surgery.

OBJECTIVE

To identify the complication rates associated with the use of bone morphogenetic protein 2 (BMP2) in PLIF. Human BMP2 is commonly used in the "off-label" manner for various types of spine fusion procedures, including PLIF. However, recent studies have reported potential complications associated with the recombinant human BMP2 (rhBMP2) use in the posterior approach.

METHODS

Medicare records within the PearlDiver database were queried for patients undergoing PLIF procedure with and without rhBMP2 between 2005 and 2010. We evaluated complications within 1 year postoperatively. Chi-square was used to compare the complication rates between the 2 groups.

RESULTS

A total of 8609 patients underwent PLIF procedure with or without rhBMP2. Individual complication rates in the rhBMP2 group ranged from 0.45% to 7.68% compared with 0.65% to 10.99 in the non-rhBMP2 group. Complication rates for cardiac, pulmonary, lumbosacral neuritis, infection, wound, and urinary tract (include acute kidney failure and post-operative complications) were significantly lower in the rhBMP2 group (P < .05). There was no difference in the rates of central nervous system complications or radiculitis between the 2 groups.

CONCLUSION

Our data showed that the patients who received rhBMP2 had lower complication rates compared to the non-rhBMP2 group. However, use of rhBMP2 was associated with a higher rate of pseudarthrosis. We did not observe any difference in radiculitis and central nervous system complications between the groups.

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.

Dose-dependent Nerve Inflammatory Response to rhBMP-2 in a Rodent Spinal Nerve Model

STUDY DESIGN

We developed a spinal nerve root wrapping rodent model to evaluate the relationship between recombinant human bone morphogenetic protein 2 (rhBMP-2) dosage and the degree of inflammation.

OBJECTIVE

To investigate the direct effects of recombinant human bone morphogenetic protein 2 (rhBMP-2) dosage and the degree of inflammation in rodent spinal nerve roots.

SUMMARY OF BACKGROUND DATA

rhBMP-2 is commonly used in clinical practice to augment spinal fusion. However, complications such as postoperative leg pain, and a higher rate of postoperative neurologic deficits have been reported. These may be attributable to the exposure of adjacent nerve roots to high doses of rhBMP-2.

METHODS

Eighteen rats were randomized into three groups as follows: Group 1: absorbable collagen sponge (ACS) + 10 μg rhBMP-2, Group 2: ACS + 1 μg rhBMP-2, and Group 3 ACS with 20 μL saline. The ACS containing rhBMP-2 or saline were then wrapped around the L5 nerve root and secured loosely with nonabsorbable sutures. At 1-week postoperation, the rats were sacrificed, and the L5 nerve root and dorsal root ganglion harvested for reverse transcription polymerase chain reaction (RT-PCR), histology and immunohistochemical staining.

RESULTS

In our study, 10 μg rhBMP-2 induced a 10-fold increase in seroma compared with 1 μg group. Using RT-PCR, macrophage markers MIP3-α, and CD-68 were upregulated by 8- and 2-fold respectively in comparison with the saline group. Haematoxylin and eosin (H&E) images demonstrated disruption of nerve structures in the high dose 10 μg rhBMP-2, but not at 1 μg rhBMP-2 and with saline.

CONCLUSION

High doses of rhBMP-2 induced neuroinflammation in a dose dependent manner, resulting in higher seroma volume, macrophage marker gene expressions, and higher proportions of immunohistochemically stained TNF-alpha and more macrophage infiltration.

LEVEL OF EVIDENCE

2.

Teriparatide attenuates scarring around murine cranial bone allograft via modulation of angiogenesis

Nearly all bone fractures in humans can deteriorate into a non-union fracture, often due to formation of fibrotic tissue. Cranial allogeneic bone grafts present a striking example: although seemingly attractive for craniofacial reconstructions, they often fail due to fibrosis at the host-graft junction, which physically prevents the desired bridging of bone between the host and graft and revitalization of the latter. In the present study we show that intermittent treatment with recombinant parathyroid hormone-analogue (teriparatide) modulates neovascularization feeding in the graft surroundings, consequently reducing fibrosis and scar tissue formation and facilitates osteogenesis. Longitudinal inspection of the vascular tree feeding the allograft has revealed that teriparatide induces formation of small-diameter vessels in the 1st week after surgery; by the 2nd week, abundant formation of small-diameter blood vessels was detected in untreated control animals, but far less in teriparatide-treated mice, although in total, more blood capillaries were detected in the animals that were given teriparatide. By that time point we observed expression of the profibrogenic mediator TGF-β in untreated animals, but negligible expression in the teriparatide-treated mice. To evaluate the formation of scar tissue, we utilized a magnetization transfer contrast MRI protocol to differentiate osteoid tissue from scar tissue, based on the characterization of collagen fibers. Using this method we found that significantly more bone matrix was formed in animals given teriparatide than in control animals. Altogether, our findings show how teriparatide diminishes scarring, ultimately leading to superior bone graft integration.

Feasibility of Percutaneous Posterolateral Spinal Fusion With Recombinant Bone Morphogenetic Protein-2 (rhBMP-2): A Comparison With Standard Methods Using an Animal Model Study

BACKGROUND CONTEXT

The clinical application of recombinant bone morphogenetic protein in spinal surgery has been shown to be safe and effective. However, its use in minimally invasive spine surgery has been limited to anterior interbody fusion procedures. To date, no study has evaluated the feasibility of percutaneous posterolateral fusion in the spine utilizing recombinant bone morphogenetic protein-2 (rhBMP-2).

PURPOSE

To evaluate the feasibility of percutaneous posterolateral fusion in the spine utilizing rhBMP-2.

STUDY DESIGN

Animal study.

METHODS

This is an animal research model involving 32 New Zealand white rabbits stratified into 4 study groups: control, autogenous iliac crest bone graft (ICBG), demineralized bone matrix (DBM), and rhBMP-2 groups, with 8 study subjects per group. The rhBMP-2 group was subdivided into the open technique (right side) and the percutaneous technique groups (left side). Fusion was graded at 6 weeks and 3 months after plain radiography, computed tomography, and clinical assessment with the following grading system: grade A, no bone formation; grade B, non-bridging bone formation; grade C, fusion; and grade D, fusion with ectopic bone formation.

RESULTS

No fusion was noted in the placebo and the DBM groups. However, in the DBM group, bone formation occurred in 37.5% of the subjects. The rhBMP-2 group had a higher fusion rate compared with the ICBG group at 6 weeks and 3 months. The fusion rate for the ICBG, the rhBMP-2 (open), and the rhBMP-2 (percutaneous) groups were 37.5%, 87.5%, and 50.0% at 6 weeks and 50.0%, 100.0%, and 62.5% at 3 months, respectively. Ectopic bone formation occurred in 12.5% of the cases in the rhBMP-2 (percutaneous) group and in 25.0% of the cases in the rhBMP-2 (open) group.

CONCLUSIONS

Usage of rhBMP-2 is feasible for percutaneous posterolateral fusion of the lumbar spine in this animal model. However, a more precise delivery system might improve the fusion rate when the percutaneous technique is used. A significant rate of ectopic bone formation occurred when rhBMP-2 was used.

Bone Morphogenic Protein Is a Viable Adjunct for Fusion in Minimally Invasive Transforaminal Lumbar Interbody Fusion

Study Design

Comparison of prospectively collected data of patients undergoing minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF) with and without recombinant human bone morphogenic protein 2 (BMP).

Purpose

To compare the clinical, radiological outcome and complications of patients undergoing MIS-TLIF with and without BMP.

Overview of Literature

BMP is an effective fusion enhancer with potential complications. Direct comparison of MIS-TLIF with and without BMP is limited to retrospective studies with short follow-up.

Methods

From June 2005 to February 2011, consecutive cases of MIS-TLIF performed by a single surgeon were included. North American Spine Society (NASS) score, Oswestry disability index (ODI), Short Form-36 (SF-36), and visual analogue score (VAS) were assessed preoperatively and at 6 and 24 months postoperatively. Fusion rates and complications were noted.

Results

The 252 cases comprised 104 non-BMP and 148 BMP cases. The BMP group was significantly older (mean age, 60.2 vs. 53.9; p<0.01). Preoperative scores were similar. Immediate postoperative morphine usage was significantly lower in the BMP group (12.4 mg vs. 20.1 mg, p<0.01). At 6 months, the BMP group had lower VAS back and leg pain scores (p<0.01). At 2 years, the BMP group had better leg pain scores (p<0.01), ODI (15.4 vs. 20.3, p=0.04) and NASS scores (8.8 vs. 15.8, p<0.01). Both groups showed significant clinical improvement compared to their preoperative levels. The BMP group attained a significantly higher rate of fusion at 6 months follow-up (88.4% vs. 76.8%, p=0.016) with no difference at 2 years. The non-BMP and BMP group had 12 (11.5%) and 9 (6.1%) complications and 5 (4.8%) and 2 (1.4%) reoperations, respectively.

Conclusions

The use of BMP to augment fusion in MIS-TLIF is an acceptable alternative that has potential benefits of less pain in early and intermediate postoperative follow-up.

Regulation of bone and cartilage by adenosine signaling

There is growing recognition that bone serves important endocrine and immunologic functions that are compromised in several disease states. While many factors are known to affect bone metabolism, recent attention has focused on investigating the role of purinergic signaling in bone formation and regulation. Adenosine is a purine nucleoside produced intracellularly and extracellularly in response to stimuli such as hypoxia and inflammation, which then interacts with P1 receptors. Numerous studies have suggested that these receptors play a pivotal role in osteoblast, osteoclast, and chondrocyte differentiation and function. This review discusses the various ways by which adenosine signaling contributes to bone and cartilage homeostasis, while incorporating potential therapeutic applications of these signaling pathways.

Ticagrelor regulates osteoblast and osteoclast function and promotes bone formation in vivo via an adenosine-dependent mechanism

As many as 10% of bone fractures heal poorly, and large bone defects resulting from trauma, tumor, or infection may not heal without surgical intervention. Activation of adenosine A2A receptors (A2ARs) stimulates bone formation. Ticagrelor and dipyridamole inhibit platelet function by inhibiting P2Y12 receptors and platelet phosphodiesterase, respectively, but share the capacity to inhibit cellular uptake of adenosine and thereby increase extracellular adenosine levels. Because dipyridamole promotes bone regeneration by an A2AR-mediated mechanism we determined whether ticagrelor could regulate the cells involved in bone homeostasis and regeneration in a murine model and whether inhibition of P2Y12 or indirect A2AR activation via adenosine was involved. Ticagrelor, dipyridamole and the active metabolite of clopidogrel (CAM), an alternative P2Y12 antagonist, inhibited osteoclast differentiation and promoted osteoblast differentiation in vitro. A2AR blockade abrogated the effects of ticagrelor and dipyridamole on osteoclast and osteoblast differentiation whereas A2BR blockade abrogated the effects of CAM. Ticagrelor and CAM, when applied to a 3-dimentional printed resorbable calcium-triphosphate/hydroxyapatite scaffold implanted in a calvarial bone defect, promoted significantly more bone regeneration than the scaffold alone and as much bone regeneration as BMP-2, a growth factor currently used to promote bone regeneration. These results suggest novel approaches to targeting adenosine receptors in the promotion of bone regeneration.-Mediero, A., Wilder, T., Reddy, V. S. R., Cheng, Q., Tovar, N., Coelho, P. G., Witek, L., Whatling, C., Cronstein, B. N. Ticagrelor regulates osteoblast and osteoclast function and promotes bone formation in vivo via an adenosine-dependent mechanism.

Allograft plus OP-1 enhances ossification in posterolateral lumbar fusion: A seven year follow-up

PURPOSE

To study the results of the combination of allograft plus BMP-7 in comparison with allograft alone in posterolateral lumbar arthrodesis.

PATIENTS AND METHODS

A blinded controlled consecutive prospective cohort of skeletally mature patients study. One hundred and ten patients underwent posterolateral lumbar instrumented arthrodesis. Allograft randomly compacted onto either the right or the left side of the articular and the posterior aspect of the transverse processes of lumbar spine. The same procedure performed on the contralateral side, but allograft was previously mixed with osteogenic protein (OP-1). Clinical, x-ray and CT-scan long follow-up performed. Univariable and multivariable logistic regression analyses.

RESULTS

More bone continuity was found with allograft plus OP-1 than with allograft alone (p>0.0038). The amount of bone mass was greater on the OP-1 side (p<0.001). No local or systemic adverse effect were noted.

CONCLUSIONS

Allograft on one side plus allograft with BMP-7 on the other achieved a fusion rate of 93 per cent. Allograft combined with BMP-7 was more effective than allograft alone.

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

OBJECT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Synthetic bone mimetic matrix-mediated in situ bone tissue formation through host cell recruitment

Advances in tissue engineering have offered new opportunities to restore anatomically and functionally compromised tissues. Although traditional tissue engineering approaches that utilize biomaterials and cells to create tissue constructs for implantation or biomaterials as a scaffold to deliver cells are promising, strategies that can activate endogenous cells to promote tissue repair are more clinically attractive. Here, we demonstrate that an engineered injectable matrix mimicking a calcium phosphate (CaP)-rich bone-specific microenvironment can recruit endogenous cells to form bone tissues in vivo. Comparison of matrix alone with that of bone marrow-soaked or bFGF-soaked matrix demonstrates similar extent of neo-bone formation and bridging of decorticated transverse processes in a posterolateral lumbar fusion rat model. Synthetic biomaterials that stimulate endogenous cells without the need for biologics to assist tissue repair could circumvent limitations associated with conventional tissue engineering approaches, including ex vivo cell processing and laborious efforts, thereby accelerating the translational aspects of regenerative medicine.

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.

Direct or indirect stimulation of adenosine A2A receptors enhances bone regeneration as well as bone morphogenetic protein-2

Promoting bone regeneration and repair of bone defects is a need that has not been well met to date. We have previously found that adenosine, acting via A2A receptors (A2AR) promotes wound healing and inhibits inflammatory osteolysis and hypothesized that A2AR might be a novel target to promote bone regeneration. Therefore, we determined whether direct A2AR stimulation or increasing endogenous adenosine concentrations via purine transport blockade with dipyridamole regulates bone formation. We determined whether coverage of a 3 mm trephine defect in a mouse skull with a collagen scaffold soaked in saline, bone morphogenetic protein-2 (BMP-2; 200 ng), 1 μM CGS21680 (A2AR agonist, EC50 = 160 nM), or 1 μM dipyridamole (EC50 = 32 nM) promoted bone regeneration. Microcomputed tomography examination demonstrated that CGS21680 and dipyridamole markedly enhanced bone regeneration as well as BMP-2 8 wk after surgery (60 ± 2%, 79 ± 2%, and 75 ± 1% bone regeneration, respectively, vs. 32 ± 2% in control, P < 0.001). Blockade by a selective A2AR antagonist (ZM241385, 1 μM) or deletion of A2AR abrogated the effect of CGS21680 and dipyridamole on bone regeneration. Both CGS21680 and dipyridamole treatment increased alkaline phosphatase-positive osteoblasts and diminished tartrate resistance acid phosphatase-positive osteoclasts in the defects. In vivo imaging with a fluorescent dye for new bone formation revealed a strong fluorescent signal in treated animals that was equivalent to BMP-2. In conclusion, stimulation of A2AR by specific agonists or by increasing endogenous adenosine levels stimulates new bone formation as well as BMP-2 and represents a novel approach to stimulating bone regeneration.

Effects of low dose FGF-2 and BMP-2 on healing of calvarial defects in old mice

There is an age-associated reduction in the bone healing activity of bone morphogenetic protein-2 (BMP-2) that is currently addressed by administering higher doses of BMP-2 in elderly patients. The unwanted medical complications from high dose BMP-2 motivated this investigation to determine whether the addition of a low dose of fibroblast growth factor 2 (FGF-2) could enhance the ability of a lower dose of BMP-2 to heal calvarial bone defects in old mice (18-20 months old). FGF-2 (5 ng) and BMP-2 (2 μg) were administered by a controlled release two-phase biomaterial scaffold placed into the bone defect. FGF-2 released more rapidly and completely in vitro than BMP-2 (40% vs 2%). In vivo, both BMP-2 and FGF-2+BMP-2 groups formed more new bone in calvarial defects than scaffold alone (p < 0.001) or FGF-2 only groups (p < 0.01). The overall total volume of new bone was not statistically increased by the addition of FGF-2 to BMP-2 as measured by microCT, but the pattern of bone deposition was different. In old mice, but not young, there was enhanced bony fill in the central bone defect area when the BMP-2 was supplemented with FGF-2. Histological analysis of the center of the defect revealed an increased bone volume (%BV/TV (p = 0.004)) from the addition of FGF-2. These studies suggest that combining a low dose of FGF-2 with a low dose of BMP-2 has the potential to increase bone healing in old mice relative to BMP-2 alone.

Twelve-month results of a multicenter, blinded, pilot study of a novel peptide (B2A) in promoting lumbar spine fusion

OBJECT

Failure of fusion after a transforaminal lumbar interbody fusion (TLIF) procedure is a challenging problem that can lead to ongoing low-back pain, dependence on pain medication, and inability to return to work. B2A is a synthetic peptide that has proven efficacy in achieving fusion in animal models and may have a better safety profile than bone morphogenetic protein. The authors undertook this study to evaluate the safety and efficacy of B2A peptide-enhanced ceramic granules (Prefix) in comparison with autogenous iliac crest bone graft (ICBG, control) in patients undergoing single-level TLIF.

METHODS

Twenty-four patients with single-level degenerative disorders of the lumbar spine at L2-S1 requiring TLIF were enrolled between 2009 and 2010. They were randomly assigned to 3 groups: a control group (treated with ICBG, n = 9), a Prefix 150 group (treated with Prefix 150 μg/cm(3) granules, n = 8), and a Prefix 750 group (treated with Prefix 750 μg/cm(3) granules, n = 7). Outcome measures included the Oswestry Disability Index (ODI), visual analog pain scale, and radiographic fusion as assessed by CT and dynamic flexion/extension lumbar plain radiographs.

RESULTS

At 12 months after surgery, the radiographic fusion rate was 100% in the Prefix 750 group, 78% in the control group, and 50% in the Prefix 150 group, although the difference was not statistically significant (p = 0.08). At 6 weeks the mean ODI score was 41.0 for the control group, 27.7 for the Prefix 750 group, and 32.2 for the Prefix 150 group, whereas at 12 months the mean ODI was 24.4 for control, 31.1 for Prefix 750, and 29.7 for Prefix 150 groups. Complications were evenly distributed among the groups.

CONCLUSIONS

Prefix appears to provide a safe alternative to autogenous ICBG. Prefix 750 appears to show superior radiographic fusion when compared with autograft at 12 months after TLIF, although no statistically significant difference was demonstrated in this small study. Prefix and control groups both appeared to demonstrate comparable improvements to ODI at 12 months.

Bone morphogenetic protein-associated complications in pediatric spinal fusion in the early postoperative period: an analysis of 4658 patients and review of the literature

OBJECT

Use of recombinant human bone morphogenetic protein-2 has risen steadily since its approval by the FDA for use in anterior lumbar interbody fusion in 2002. The FDA has not approved the use of bone morphogenetic protein (BMP) in children. Age less than 18 years or lack of evidence of epiphyseal closure are considered by the manufacturer to be contraindications to BMP use. In light of this, the authors performed a query of the database of one of the nation's largest health insurance companies to determine the rate of BMP use and complications in pediatric patients undergoing spinal fusion.

METHODS

The authors used the PearlDiver Technologies private payer database containing all records from United Health-Care from 2005 to 2011 to query all cases of pediatric spinal fusion with or without BMP use. A review of the literature was also performed to examine the complications associated with BMP use in pediatric spinal fusion.

RESULTS

A total of 4658 patients underwent spinal fusion. The majority was female (65.4%), and the vast majority was age 10-19 years (94.98%) and underwent thoracolumbar fusion (93.13%). Bone morphogenetic protein was used in 1752 spinal fusions (37.61%). There was no difference in the rate of BMP use when comparing male and female patients or age 10 years or older versus less than 10 years. Anterior cervical fusions were significantly less likely to use BMP (7.3%). Complications occurred in 9.82% of patients treated with versus 9.88% of patients treated without BMP. The complication rate was nearly identical in male versus female patients and in patients older versus younger than 10 years. Comparison of systemic, wound-related, CNS, and other complications showed no difference between groups treated with and without BMP. The reoperation rate was also nearly identical.

CONCLUSIONS

Bone morphogenetic protein is used in a higher than expected percentage of pediatric spinal fusions. The rate of acute complications in these operations does not appear to be different in patients treated with versus those treated without BMP. Caution must be exercised in interpreting these data due to the many limitations of the administrative database as a data source, including the short length of follow-up.

Quality-of-Life Outcomes following Thoracolumbar and Lumbar Fusion with and without the Use of Recombinant Human Bone Morphogenetic Protein-2: Does Recombinant Human Bone Morphogenetic Protein-2 Make a Difference?

Design Retrospective study. Objectives (1) To investigate the quality-of-life (QOL) outcomes in the population undergoing lumbar spine surgery with versus without recombinant human bone morphogenetic protein-2 (rhBMP-2); (2) to determine QOL outcomes for those patients who experience postoperative complications; and (3) to identify the effect of patient characteristics on postoperative QOL outcomes. Methods A retrospective review of QOL questionnaires, including the Patient Health Questionnaire-9, Patient Disability Questionnaire (PDQ), EuroQol-5D (EQ-5D), and quality of life-year (QALY), was performed for all patients who underwent thoracolumbar and lumbar fusion surgery with versus without rhBMP-2 between March 2008 and September 2010. Individual preoperative and postoperative QOL data were compared for each patient. Demographic factors and complications were reviewed. Results We identified 266 patients, including 60 with and 206 without rhBMP-2. Questionnaires were completed an average of 10.3 ± 5 months after surgery. For all measures, average scores improved postoperatively compared with preoperatively. No differences in postoperative QOL outcomes were identified between the rhBMP-2 and the control cohorts. Median annual household income was positively associated with EQ-5D and QALY. Compared with those without, patients with postoperative complications had fewer QOL improvements. Conclusions There was no difference in QOL outcomes in the rhBMP-2 compared with the control group. Socioeconomic status and postoperative complications affected QOL outcomes following surgery. The QOL questionnaires provide the clinician with information regarding the patients' self-perceived well-being and can be helpful in the selection of surgical candidates and for understanding the effectiveness of a given surgical procedure.

Multiple myeloma exacerbation following utilization of bone morphogenetic protein-2 in lateral lumbar interbody fusion: a case report and review of the literature

BACKGROUND CONTEXT

Recent studies generated antithetic results regarding the safety of bone morphogenetic protein-2 (BMP-2) use in spine surgery, and the effect of this biologic adjunct on myeloma cells remains to be fully elucidated.

PURPOSE

The purpose of this study was to present a case of multiple myeloma (MM) exacerbation after BMP-2 implantation in the setting of lateral lumbar interbody fusion (LLIF).

STUDY DESIGN

Case report and literature review.

METHODS

The medical records, laboratory findings, and radiographic imaging studies of an 86-year-old female patient with exacerbation of previously undiagnosed MM were reviewed.

RESULTS

The patient presented with a 10-year history of debilitating lower back pain and bilateral lower extremity claudication. Radiographic studies depicted lumbar scoliosis and lateral spondylolisthesis. Preoperative serum immunofixation electrophoresis showed a serum immunoglobulin A kappa paraprotein-peak; however, the patient had never been diagnosed with MM or reported any unexplained fever, night sweats, or weight loss indicative of MM. The patient underwent LLIF from L1-L5 supplemented by BMP-2. On postoperative day 1, the patient was evaluated by the hematology department for paraproteinemia. Serum electrophoresis showed decreased albumin, hypogammaglobulinemia, and suspicious broadening of the complement component in the beta region. Postoperative imaging studies (19 weeks) depicted progression of a previously visible intraosseous lesion, and anterior cortical breakthrough (L5), in addition to a soft tissue mass at the T10 level. Histological examination of iliac crest and T10 vertebral biopsies showed fatty marrow infiltration by plasma cells and plasma cell dyscrasia, proving the diagnosis of MM. The patient died 10 months after surgery due to complications related to a methicillin-resistant Staphylococcus aureus infection.

CONCLUSIONS

Based on the present case, perhaps one should consider that in patients with abnormal electrophoresis results, even in the absence of a prior diagnosis of MM as well as in the absence of symptoms indicative of MM, BMPs should be administered only after preoperative exclusion of neoplastic disease.

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

STUDY DESIGN

Systematic review.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

3.

Contralateral motor deficits after lateral lumbar interbody fusion

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To report on the rare finding of motor deficits contralateral to the transpsoas approach in patients who underwent lateral lumbar interbody fusion (LLIF).

SUMMARY OF BACKGROUND DATA

Although sensorimotor deficits occurring ipsilaterally to a transpsoas approach have more fully been elucidated, there seems to be a paucity of data on motor deficits contralateral to an LLIF approach.

METHODS

The electronic medical records and radiographical studies of 244 patients who underwent LLIF at a single institution between 2006 and 2009 were retrospectively reviewed for reports on motor deficits contralateral to the surgical approach.

RESULTS

Of the patients reviewed, 2.9% (7/244) presented with a postoperative contralateral motor deficit, the most severe of which was a 1/5 weakness of the quadriceps muscle. An average of 3 levels (range: 2-4) was fused in 7 patients who developed a contralateral motor deficit, and in 3 of the 7 patients, an anterior lumbar interbody fusion (ALIF) was performed in addition to the LLIF. At 1 year follow-up, 3 patients presented with complete resolution of their muscle weakness, 1 patient still had mild weakness, 1 patient had decreased range of motion in the affected joint, and 1 patient had a 2/5 foot drop. One patient was lost to follow-up.

CONCLUSION

These data are among the largest reports of contralateral motor deficits after LLIF. Among possible underlying mechanisms are entrapment of the contralateral nerve root through translational correction of spondylolisthesis, front-to-back misalignment of the cage resulting in contralateral nerve root impingement, pressure on the contralateral peroneal nerve during positioning, and overdistraction neurapraxia when using ALIF at L5-S1 concomitantly. Awareness of the possibility of this rare complication can play an important role in surgical consideration and preoperative patient counseling.

LEVEL OF EVIDENCE

4.

Complications of rhBMP-2 utilization for posterolateral lumbar fusions requiring reoperation: a single practice, retrospective case series report

BACKGROUND CONTEXT

Recombinant human bone morphogenetic protein-2 (rhBMP-2) (INFUSE, Medtronic, Memphis, TN, USA) has been used off-label for posterolateral lumbar fusions for many years.

PURPOSE

The goal of this study was to evaluate the complications requiring reoperation associated with rhBMP-2 application for posterolateral lumbar fusions.

STUDY DESIGN/SETTING

During a 7-year period of time (2002-2009), all patients undergoing lumbar posterolateral fusion using rhBMP-2 (INFUSE) were retrospectively evaluated within a large orthopedic surgery private practice.

PATIENT SAMPLE

A total of 1,158 consecutive patients were evaluated with 468 (40.4%) males and 690 (59.6%) females.

OUTCOME MEASURES

Complications related to rhBMP were defined as reoperation secondary to symptomatic failed fusion (nonunion), symptomatic seroma formation, symptomatic reformation of foraminal bone, and infection.

METHODS

Inclusion criteria were posterolateral fusion with rhBMP-2 implant and age equal to or older than 18 years. Surgical indications and treatment were performed in accordance with the surgeon's best knowledge, discretion, and experience. Patients consented to lumbar decompression and arthrodesis using rhBMP-2. All patients were educated and informed of the off-label utilization of rhBMP-2. Patient follow-up was performed at regular intervals of 2 weeks, 6 weeks, 12 weeks, 6 months, 1 year, and later if required or indicated.

RESULTS

Average age was 59.2 years, and body mass index was 30.7 kg/m². Numbers of levels fused were 1 (414, 35.8%), 2 (469, 40.5%), 3 (162, 14.0%), 4 (70, 6.0%), 5 (19, 1.6%), 6 (11, 0.9%), 7 (7, 0.6%), 8 (4, 0.3%), and 9 (2, 0.2%). Patients having complications requiring reoperation were 117 of 1,158 (10.1%): symptomatic nonunion requiring redo fusion and instrumentation 41 (3.5%), seroma with acute neural compression 32 (2.8%), excess bone formation with delayed neural compression 4 (0.3%), and infection requiring debridement 26 (2.2%). Nonunion was related to male sex and previous BMP exposure. Seroma formation was significantly higher in patients with higher doses of rhBMP-2 (p=.050) and with more than 12 mg of rhBMP-2 (χ(2)=0.025). Bone reformation and neural compression at the laminectomy and foraminotomy sites occurred in a delayed fashion. Infection was associated with obesity and respiratory disease. Infections were noted with a greater BMP dose (p<.001), more than 12 mg (χ(2)<0.001), fusion more than three levels (χ(2)<0.001), and reexposed to BMP (χ(2)=0.023).

CONCLUSIONS

rhBMP-2 utilization for posterolateral lumbar fusions has a low symptomatic nonunion rate. Prior rhBMP-2 exposure and male sex were related to symptomatic nonunion formation. rhBMP-2-associated neural compression acutely with seroma formation and delayed with foraminal bone formation is concerning and associated with higher rhBMP-2 concentrations.

Risk of cancer after lumbar fusion surgery with recombinant human bone morphogenic protein-2 (rh-BMP-2)

STUDY DESIGN

Retrospective cohort study among Medicare beneficiaries with lumbar spinal fusion surgery.

OBJECTIVE

To determine the risk of subsequent cancer among patients who received recombinant human bone morphogenic protein (rhBMP) at surgery compared with those who did not.

SUMMARY OF BACKGROUND DATA

rhBMP is commonly used to promote bone union after spinal surgery. BMP receptors are present on multiple cancer types, but the risk of cancer after receiving rhBMP has not been well studied.

METHODS

We identified 146,278 subjects aged 67 years and older who underwent surgery in 2003 to 2008 and were followed through 2010 for a new diagnosis of 1 of 26 cancers. Proportional hazards models were used to determine cancer risk associated with rhBMP use.

RESULTS

rhBMP was administered in 15.1% of the cohort. After an overall average follow-up of 4.7 years, 15.4% of rhBMP-treated and 17.0% of untreated patients had a new cancer diagnosis, with most commonly recorded types as prostate, breast, lung, and colorectal. In a multivariate proportional hazards model, there was no association of rhBMP with cancer risk (hazard ratio: 0.99, 95% confidence interval: 0.95-1.02). There was also no association of rhBMP with the risk of any individual cancer types. The results were consistent in analyses using 2 secondary definitions of incident cancer.

CONCLUSION

In this large population-based analysis of Medicare beneficiaries, we found no evidence that administration of rhBMP at the time of lumbar fusion surgery was associated with cancer risk.

LEVEL OF EVIDENCE

4.

Patient factors, comorbidities, and surgical characteristics that increase mortality and complication risk after spinal arthrodesis: a prognostic study based on 5,887 patients

BACKGROUND CONTEXT

The impact of patient factors and medical comorbidities on the risk of mortality and complications after spinal arthrodesis has not been well described. Prior works have been limited by small sample size, single center data, or the inability to be broadly generalized.

PURPOSE

To determine if there is an association between the patient demographic factors, comorbidities, nutritional status, and surgical characteristics and the occurrence of mortality and complications after spinal arthrodesis.

STUDY DESIGN

Retrospective review of prospectively collected data in the National Surgical Quality Improvement Program (NSQIP).

PATIENT SAMPLE

Patients who underwent spinal arthrodesis and had data registered with the NSQIP between 2005 and 2010.

OUTCOME MEASURES

Primary outcomes were death or any complication after spinal arthrodesis. Secondary measures were the development of a specific complication, including wound infection, thromboembolic disease, or cardiac arrest/myocardial infarction.

METHODS

The data set of the NSQIP from 2005 to 2010 was queried to identify all patients who underwent spinal arthrodesis. Demographic information, body mass index (BMI), medical comorbidities, arthrodesis procedure, operative time, American Society of Anesthesiologists (ASA) classification, and preoperative albumin were recorded for all patients identified. Mortality, the development of postoperative complications, and the presence of specific complications were also abstracted. Risk factors for mortality and complications were initially evaluated using chi-square and univariate logistic regression analyses. The risk factors that maintained p values less than .2 in univariate analysis were then combined in a multivariate fashion that identified significant, independent, predictors of mortality and complications while controlling for other factors present in the model. Sensitivity analysis was also performed, discriminating between the impact of risk factors on major and minor complications and the relative contribution to overall risk of morbidity. Multivariate analysis resulted in odds ratios (ORs) with 95% confidence intervals (CIs) for each risk factor. Only those predictors with ORs and 95% CI exclusive of 1.0 and p values less than .05 were considered statistically significant.

RESULTS

In all, 5,887 patients who underwent spinal arthrodesis were identified. The average age of patients was 55.9 (±14.5) years. Twenty-five (0.42%) patients died after surgery, whereas 608 (10%) sustained a complication. Wound infection was the most common specific complication occurring in 2% of the cohort. Age (p=.03) and pulmonary conditions (p=.002) were found to have a significant association with the risk of mortality. Age exceeding 80 years was found to carry the highest risk of mortality. Age, pulmonary conditions, BMI, history of infection, ASA classification more than 2, neurologic conditions, resident (i.e., trainee) involvement, and procedural times exceeding 309 minutes increased the risk of complications. Body mass index, ASA classification more than 2, resident involvement, and procedural times exceeding 309 minutes were associated with the risk of infection. Although limited to univariate analysis, serum albumin 3.5 g/dL or less increased the risk of mortality, complications, wound infection, and thromboembolic disease. The OR for postoperative mortality among patients with albumin 3.5 g/dL or less was 13.8 (95% CI, 4.6-41.6; p<.001).

CONCLUSIONS

Several factors, including patients' age, BMI, ASA classification more than 2, pulmonary conditions, procedural times, and nutritional status likely influence the risk of postoperative morbidity to varying degrees. The risk factors identified here may be more generalizable to the American population as a whole because of the design and methodology of the NSQIP in comparison with previously published studies.

Radiologic changes of anterior cervical discectomy and fusion using allograft and plate augmentation: comparison of using fixed and variable type screw

Objective

To evaluate radiologic result of anterior cervical discectomy and fusion with allobone graft and plate augmentation, and the change of radiologic outcome between screw type and insertion angle.

Methods

Retrospective review of clinical and radiological data of 29 patients. Segmental angle, height and screw angles were measured and followed. The fusion rate was assessed by plain radiography and CT scans. We divided the patients into two groups according to screw type and angles. Group A: fixed screw, Group B: variable screw. Interscrew angle was measured between most upper and lower screws with Cobb's methods.

Results

Overall fusion rate was 86.2% on plain radiography. Fusion was also assessed by CT scan and Bridwell's grading system. There was no difference in fusion and subsidence rates between two groups. Subsidence was found in 5 patients (17.2%). Segmental lordotic angle was increased from preoperative status and maximized at the immediate postoperative period and then reduced at 1 year follow up. Segmental height showed similar increase and decrease values.

Conclusion

ACDF with allograft and plate showed favorable fusion rates, and the screw type and angle did not affect results of surgery.

High-dose rhBMP-2 for adults: major and minor complications: a study of 502 spine cases

BACKGROUND

Use of recombinant human bone morphogenetic protein-2 (rhBMP-2) has increased considerably since its introduction in 2002. The complications associated with high-dose rhBMP-2 (≥ 40 mg) are unknown. The purpose of our study was to determine outcomes and medical and surgical complications associated with high-dose rhBMP-2 at short-term and long-term follow-up evaluations.

METHODS

Five hundred and two consecutive adult patients who had received high-dose rhBMP-2 as a part of spinal surgery from 2002 to 2009 at one institution were enrolled. Data were entered prospectively and studied and analyzed retrospectively. Surgical procedures in the thoracic and lumbar spine were included. Major and minor complications were documented intraoperatively, perioperatively, and at the latest follow-up examination. Complications potentially associated with rhBMP-2 use were evaluated for correlation with rhBMP-2 dose. Scoliosis Research Society (SRS) and Oswestry Disability Index (ODI) outcome measures were obtained before and after surgery.

RESULTS

On average, 115 mg (range, 40 to 351 mg) of rhBMP-2 was used. The average age of the patients (410 women and ninety-two men) at the time of the index procedure was 52.4 years (range, eighteen to eighty years). There were 265 primary and 237 revision procedures, and 261 patients had interbody fusion. An average of 11.5 vertebrae were instrumented. The average duration of follow-up was forty-two months (range, fourteen to ninety-two months). The diagnoses included idiopathic scoliosis (41%), degenerative scoliosis (31%), fixed sagittal imbalance (18%), and other diagnoses (10%). The rate of intraoperative complications was 8.2%. The rate of perioperative major surgical complications was 11.6%. The rate of perioperative major medical complications was 11.6%. Minor medical complications occurred in 18.9% of the cases, and minor surgical complications occurred in 2.6%. Logistic regression analysis and Pearson correlation did not identify a significant correlation between rhBMP-2 dosage and radiculopathy (r = -0.006), seroma (r = -0.003), or cancer (r = -0.05). Significant improvements in the ODI score (from a mean of 41 points to a mean of 26 points; p < 0.001) and the SRS total score (from a mean of 3.0 points to a mean of 3.7 points; p < 0.001) were noted at the latest follow-up evaluation.

CONCLUSIONS

This is the largest study of which we are aware that examines complications associated with high-dose rhBMP-2. Major surgical complications occurred in 11.6% of patients, and 11.6% experienced major medical complications. There was a cancer prevalence of 3.4%, but no correlation between increasing rhBMP-2 dosage and cancer, radiculopathy (seen in 1% of the patients), or seroma (seen in 0.6%) was found.

Fusion and subsidence rate of stand alone anterior lumbar interbody fusion using PEEK cage with recombinant human bone morphogenetic protein-2

INTRODUCTION

Anterior lumbar interbody fusion (ALIF) is an established treatment for structural instability associated with symptomatic disk degeneration (SDD). Stand-alone ALIF offers many advantages, however, it may increase the risk of non-union. Recombinant human bone morphogenetic protein-2 (BMP-2) may enhance fusion rate but is associated with postoperative complication. The optimal dose of BMP-2 remains unclear. This study assessed the fusion and subsidence rates of stand-alone ALIF using the SynFix-LR interbody cage with 6 ml/level of BMP-2.

METHODS

Thirty-two ALIF procedures were performed by a single surgeon in 25 patients. Twenty-five procedures were performed for SDD without spondylolisthesis (SDD group) and seven procedures were performed for SDD with grade-I olisthesis (SDD-olisthesis group). Patients were followed-up for a mean of 17 ± 6 months.

RESULTS

Solid fusion was achieved in 29 cases (90.6 %) within 6 months postoperatively. Five cases of implant subsidence were observed (16 %). Four of these occurred in the SDD-olisthesis group and one occurred in the SDD group (57 % vs. 4 % respectively; p = 0.004). Three cases of subsidence failed to fuse and required revision. The body mass index of patients with olisthesis who developed subsidence was higher than those who did not develop subsidence (29 ± 2.6 vs. 22 ± 6.5 respectively; p = 0.04). No BMP-2 related complications occurred.

CONCLUSION

The overall fusion rate of stand-alone ALIF using the SynFix-LR system with BMP-2 was 90.6 %, comparable with other published series. No BMP-2 related complication occurred at a dose of 6 mg/level. Degenerative spondylolisthesis and obesity seemed to increase the rate of implant subsidence, and thus we believe that adding posterior fusion for these cases should be considered.

pHEMA-nHA encapsulation and delivery of vancomycin and rhBMP-2 enhances its role as a bone graft substitute

BACKGROUND

Bone grafts are widely used in orthopaedic procedures. Autografts are limited by donor site morbidity while allografts are known for considerable infection and failure rates. A synthetic composite bone graft substitute poly(2-hydroxyethyl methacrylate)-nanocrystalline hydroxyapatite (pHEMA-nHA) was previously developed to stably press-fit in and functionally repair critical-sized rat femoral segmental defects when it was preabsorbed with a single low dose of 300 ng recombinant human bone morphogenetic protein-2/7 (rhBMP-2/7).

QUESTIONS/PURPOSES

To facilitate clinical translation of pHEMA-nHA as a synthetic structural bone graft substitute, we examined its ability to encapsulate and release rhBMP-2 and the antibiotic vancomycin.

METHODS

We analyzed the compressive behavior and microstructure of pHEMA-nHA as a function of vancomycin incorporation doses using a dynamic mechanical analyzer and a scanning electron microscope. In vitro release of vancomycin was monitored by ultraviolet-visible spectroscopy. Release of rhBMP-2 from pHEMA-nHA-vancomycin was determined by ELISA. Bioactivity of the released vancomycin and rhBMP-2 was examined by bacterial inhibition and osteogenic transdifferentiation capabilities in cell culture, respectively.

RESULTS

Up to 4.8 wt% of vancomycin was incorporated into pHEMA-nHA without compromising its structural integrity and compressive modulus. Encapsulated vancomycin was released in a dose-dependent and sustained manner in phosphate-buffered saline over 2 weeks, and the released vancomycin inhibited Escherichia coli culture. The pHEMA-nHA-vancomycin composite released preabsorbed rhBMP-2 in a sustained manner over 8 days and locally induced osteogenic transdifferentiation of C2C12 cells in culture.

CONCLUSIONS

pHEMA-nHA can encapsulate and deliver vancomycin and rhBMP-2 in a sustained and localized manner with reduced loading doses.

CLINICAL RELEVANCE

The elasticity, osteoconductivity, and rhBMP-2/vancomycin delivery characteristics of pHEMA-nHA may benefit orthopaedic reconstructions or fusions with enhanced safety and efficiency and reduced infection risk.

Symptomatic calcified perineural cyst after use of bone morphogenetic protein in transforaminal lumbar interbody fusion: a case report

BACKGROUND CONTEXT

Human recombinant bone morphogenetic protein-2 (BMP-2) is commonly used in spinal surgery to augment arthrodesis, and a number of potential complications have been documented.

PURPOSE

To present the case of a delayed radiculopathy that occurred because of a calcified perineural cyst that formed after an L4-L5 transforaminal lumbar interbody fusion (TLIF) in which BMP-2 was used.

STUDY DESIGN/SETTING

Case report of a 70-year-old man presented with back and right lower extremity pain.

METHODS

A 70-year-old man who had previously undergone a right L4-L5 TLIF presented 20 months after surgery with progressively radiating right leg pain. Imaging revealed a right-sided L4-L5 cystic lesion posterior to the interbody cage. The patient underwent reexploration, and a calcified mass was discovered.

RESULTS

Histopathology revealed fragments of organized collagenous connective tissue, new collagen, and partially calcified fragments of fibrocartilage, bone, and ligament.

CONCLUSIONS

This is the first reported case of a symptomatic calcified perineural cyst developing after a fusion procedure in which BMP-2 was used. The presence of connective tissue with metaplastic bone formation and maturation within the lesion suggests that formation of the cyst was secondary to application of BMP-2, as it possesses both osteogenic and chondrogenic capabilities.

FK506 activates BMPR2, rescues endothelial dysfunction, and reverses pulmonary hypertension

Dysfunctional bone morphogenetic protein receptor-2 (BMPR2) signaling is implicated in the pathogenesis of pulmonary arterial hypertension (PAH). We used a transcriptional high-throughput luciferase reporter assay to screen 3,756 FDA-approved drugs and bioactive compounds for induction of BMPR2 signaling. The best response was achieved with FK506 (tacrolimus), via a dual mechanism of action as a calcineurin inhibitor that also binds FK-binding protein-12 (FKBP12), a repressor of BMP signaling. FK506 released FKBP12 from type I receptors activin receptor-like kinase 1 (ALK1), ALK2, and ALK3 and activated downstream SMAD1/5 and MAPK signaling and ID1 gene regulation in a manner superior to the calcineurin inhibitor cyclosporine and the FKBP12 ligand rapamycin. In pulmonary artery endothelial cells (ECs) from patients with idiopathic PAH, low-dose FK506 reversed dysfunctional BMPR2 signaling. In mice with conditional Bmpr2 deletion in ECs, low-dose FK506 prevented exaggerated chronic hypoxic PAH associated with induction of EC targets of BMP signaling, such as apelin. Low-dose FK506 also reversed severe PAH in rats with medial hypertrophy following monocrotaline and in rats with neointima formation following VEGF receptor blockade and chronic hypoxia. Our studies indicate that low-dose FK506 could be useful in the treatment of PAH.

Contralateral psoas seroma after transpsoas lumbar interbody fusion with bone morphogenetic protein-2 implantation

BACKGROUND CONTEXT

The lateral transpsoas approach to interbody fusion of the lumbar spine (lateral lumbar interbody fusion [LLIF]) with recombinant human bone morphogenetic protein-2 (BMP-2) augmentation has been increasingly performed in recent years. Potential side effects and adverse sequelae of BMP-2 in the acute setting remain to be fully elucidated.

PURPOSE

To review the literature for reports of complications related to BMP-2 implantation in lumbar spinal surgery and present a case of a contralateral psoas muscle seroma after LLIF with BMP-2 implantation.

STUDY DESIGN

Case report and literature review.

METHODS

The PubMed database was searched for articles related to adverse events to BMP-2 in lumbar spinal surgery. We report the case of a 57-year-old woman who underwent routine right-sided transpsoas approach for LLIF with the use of BMP-2 at our institution and developed a left-sided psoas muscle fluid accumulation 2 weeks postoperatively.

RESULTS

No reports of complications contralateral to an LLIF approach attributable to an inflammatory response to BMP-2 were identified in the English literature. In the presented patient, a large (4.2×6.5×2.7 cm) left-sided sterile intramuscular psoas fluid collection was seen on a magnetic resonance imaging study obtained on postoperative day 14. At a 6-month follow-up, left-sided L5 radiculopathy resulting in 4/5 foot drop was confirmed by electromyography. The patient reported here represents the only case of a contralateral psoas seroma with suspected association to BMP-2 utilization in LLIF encountered at our institution.

CONCLUSIONS

A serous psoas muscle fluid accumulation after BMP-2 implantation may rarely occur contralateral to the surgical approach for LLIF. Further characterization of complications related to BMP-2 implantation after lumbar spinal surgery will help guide preoperative informed decision making and the management of this unusual postoperative adverse event.

The cost-effectiveness of periodic safety update reports for biologicals in Europe

We analyzed the cost-effectiveness of all Periodic Safety Update Reports (PSURs) submitted for biologicals in Europe from 1995 to 2009 by comparing two regulatory scenarios: full regulation (PSUR reporting) and limited regulation (no PSUR reporting, but all other parts of the pharmacovigilance framework remain in place). During this period, PSUR reporting resulted in the detection of 2 out of a total of 24 urgent safety issues for biologicals: (i) distant spread of botulinum toxin and (ii) edema/fluid collection associated with off-label use of dibotermin-alfa. We used Markov-chain life tables to calculate costs and health effects of PSURs. The incremental cost-effectiveness ratio (ICER) of full regulation (PSUR reporting) vs. limited regulation (no PSUR reporting) for the base-case scenario was \[euro]342,110 per quality-adjusted life year (QALY) gained. It is possible to assess the cost-effectiveness of regulatory requirements using the same methods as those used in assessing the cost-effectiveness of medical interventions.