Use of Recombinant Human Bone Morphogenetic Protein-2 as an Adjunct in Posterolateral Lumbar Spine Fusion

Assessment of Posterolateral Lumbar Fusion: A Systematic Review of Imaging-Based Fusion Criteria

BACKGROUND

Noninvasive assessment of osseous fusion after spinal fusion surgery is essential for timely diagnosis of patients with symptomatic pseudarthrosis and for evaluation of the performance of spinal fusion procedures. There is, however, no consensus on the definition and assessment of successful posterolateral fusion (PLF) of the lumbar spine. This systematic review aimed to (1) summarize the criteria used for imaging-based fusion assessment after instrumented PLF and (2) evaluate their diagnostic accuracy and reliability.

METHODS

First, a search of the literature was conducted in November 2018 to identify reproducible criteria for imaging-based fusion assessment after primary instrumented PLF between T10 and S1 in adult patients, and to determine their frequency of use. A second search in July 2021 was directed at primary studies on the diagnostic accuracy (with surgical exploration as the reference) and/or reliability (interobserver and intraobserver agreement) of these criteria. Article selection and data extraction were performed by at least 2 reviewers independently. The methodological quality of validation studies was assessed with the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) and QAREL (Quality Appraisal of Reliability Studies).

RESULTS

Of the 187 articles included from the first search, 47% used a classification system and 63% used ≥1 descriptive criterion related to osseous bridging (104 articles), absence of motion (78 articles), and/or absence of static signs of nonunion (39 articles). A great variation in terminology, cutoff values, and assessed anatomical locations was observed. While the use of computed tomography (CT) increased over time, radiographs remained predominant. The second search yielded 11 articles with considerable variation in outcomes and quality concerns. Agreement between imaging-based assessment and surgical exploration with regard to demonstration of fusion ranged between 55% and 80%, while reliability ranged from poor to excellent.

CONCLUSIONS

None of the available criteria for noninvasive assessment of fusion status after instrumented PLF were demonstrated to have both sufficient accuracy and reliability. Further elaboration and validation of a well-defined systematic CT-based assessment method that allows grading of the intertransverse and interfacet fusion mass at each side of each fusion level and includes signs of nonunion is recommended.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Active bone material containing modified recombinant human bone morphogenetic protein-2 induces bone regeneration in rabbit spina bifida

This study focuses on spina bifida, which is a high incidence among the current clinical manifestations of human birth defects. Because in the treatment of bone defects, the source of autologous bone is limited and it is easy to cause secondary injury to the patient. At the same time, since the bone tissue in animals needs to perform a variety of biological functions, its complex structure cannot be replaced by a single material. Therefore, in this study, we used Japanese white rabbits to establish an animal model similar to human congenital spina bifida. The established animal model is used to screen the best regenerative repair products for the treatment of congenital spondylolisthesis defects, and to evaluate the safety of regenerative repair products. The results show that bone morphogenetic protein (BMP)-2 combined with collagen material has a better regeneration effect than collagen material alone, and it did not negatively affect the health of animals. This study is not only suitable for the screening of large-scale biomaterials, accelerating the research progress of regenerative repair products, but also conducive to the research on the mechanism of regeneration and repair of various materials.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Applications of Bone Morphogenetic Proteins in Dentistry: A Bibliometric Analysis

Background

Many articles on bone morphogenetic proteins (BMPs) have been published. Bibliometric analysis is helpful to determine the most influential studies in a specific field. This bibliometric analysis is aimed at identifying and analyzing the top 50 most-cited articles on the dental applications of BMPs.

Methods

An electronic search was conducted using the Web of Science (WoS) “All Databases” without any restriction of language, study design, or publication year. Of 1341 publications, the top 50 were included based on their citation count. After downloading the full texts, their bibliometric data including publication title, authorship, citation count, current citation index 2019, citation density, year of publication, country and institution of origin, journal of publication, type of BMP, study design, evidence level of publication, and keywords were extracted and analyzed.

Results

The citation counts for the top 50 publications ranged from 81 to 557 (median 113.5). The most prolific year was 1997 (n = 7). Wikesjö UM (n = 12) and Wozney JM (n = 11) were the major contributors in this study. Most of the articles were generated primarily from the USA (n = 24), with Loma Linda University Medical Center, USA being the most prolific institution (n = 5). Majority of the articles were published in the Clinical Oral Implants Research and Journal of Periodontology, with nine publications each. Most of the publications were animal studies (n = 30) and focused on BMP-2 (n = 39). Most of the articles were within evidence level V (n = 36). The most frequently used keyword in the top articles was “bone regeneration” (n = 23).

Conclusion

The present study presents insights into the past and recent trends in the applications of BMPs in dentistry. A statistically significant association was observed between citation count, citation density, and age of publication.

Anterior cervical discectomy and fusion with recombinant human bone morphogenetic protein-2-adsorbed β-tricalcium phosphate granules: a preliminary report

Background

Anterior cervical discectomy and fusion (ACDF) is an alternative to conservative therapy in the treatment of cervical spondylopathy. This study evaluated the clinical outcome of ACDF with BMP-2-adsorbed β-tricalcium phosphate granules.

Methods

Thirty-two patients with cervical spondylopathy received treatment of ACDF with BMP-2-adsorbed β-tricalcium phosphate granules. The clinical outcomes were evaluated with the Japanese Orthopedic Association (JOA) scores and Neck Disability Index (NDI). Meanwhile, the cervical curvature and intervertebral heights were obtained through lateral cervical X-ray films pre- and postoperatively at each interval, and the precision of cervical fusion was assessed by three-dimensional computed tomography scan.

Results

The follow-up averaged 15.2 months (range 13–18). Average JOA scores significantly increased from a preoperative point (7.4 ± 1.2) to each interval after surgery (P < 0.05). NDI decreased from preoperative point (43.1 ± 9.0) to each interval after surgery (P < 0.05). The angles of cervical curvature and intervertebral heights were improved postoperatively and kept throughout the follow-up period. CT scan demonstrated a fusion rate of 82.9% at 6 months postoperatively and was improved to 100% at 12 months postoperatively. In all cases, no complications appeared and reported due to any lapse in surgical procedure skills throughout the follow-up period.

Conclusions

Our preliminary findings suggest that BMP-2-adsorbed β-tricalcium phosphate granules will be an effective alternative to autogenous bone grafting for cervical fusion in treating cervical spondylopathy. Our surgical procedure usingβ-tricalcium phosphate granules could improve neurological function, recover intervertebral height and cervical curvature, and could be potentially exploitable in the clinical setting.

Lumbar Spine Fusion Rates With Local Bone in Posterolateral and Combined Posterolateral and Interbody Approaches

Posterolateral lumbar fusion (PLF) used to treat degenerative lumbar conditions still faces pseudarthrosis. Bone graft choice is a key factor; a traditional choice has been autologous iliac crest bone graft (ICBG), but complication rates are quoted up to 39%. Local bone from laminectomy eliminates ICBG harvesting complications.

Methods

Two hundred forty-one patients underwent either PLF or PLF with interbody at a single lumbar level with a prospective, multicenter, randomized controlled trial only using local bone graft. Fusion was assessed with radiographs and CT.

Results

PLF fused bilaterally in 18% and unilaterally in 28.8% at 6 months and 35.7% and 50.3% at 12 months, respectively. At 6-month PLF + interbody, 1.1% fused bilaterally and 11.7% unilaterally; at 12 months, 5.4% fused all three areas, and 50.8% fused at least one area.

Discussion

Local bone fused substantially less than the "benchmark" ICBG.

Can We Justify It? Trends in the Utilization of Spinal Fusions and Associated Reimbursement

BACKGROUND

Previous reports have suggested an increasing rate of utilization of spinal fusions, but contemporary data have not been analyzed, and there has been little investigation of putative drivers of increased utilization.

OBJECTIVE

To investigate whether there is an ongoing trend of increased utilization of spinal fusions in recent data, and if there may be associations with an increasing proportion of elderly in the population, changing patterns of payer-types, and changing reimbursement rates.

METHODS

We analyze 7.1 million cases from the National Inpatient Sample between 1998 and 2014. We measure annual utilization per 100 000 persons and conduct trend analyses with subgroup analysis of the senior (65 + ) population. Spine surgery utilization is compared with nonspine surgical procedures (coronary artery bypass grafting, hernia repair, hip, and knee replacement). We assess trends in charges, payer type, Medicare reimbursement rates, and hospital type.

RESULTS

There was an 88% increase in the utilization rate of spinal fusion procedures from 1998 to 2014 (from 74 to 139 cases per 100 000 persons) with a significant upward trend (P < .001) that persisted in the 65 + subgroup (P < .001). An increasing proportion of spinal fusions is paid for by public payers, but per-procedure reimbursement for spinal fusions by Medicare has decreased recently (5% reduction from 2014 to 2016).

CONCLUSION

Utilization of spinal fusions continues to increase and is not explained by increased proportion of elderly in the population, increased utilization of surgeries across specialties, or increased Medicare reimbursement. In fact, increased utilization of spinal fusions temporally correlated with decreasing per-procedure Medicare reimbursement.

Current Updates on Bone Grafting Biomaterials and Recombinant Human Growth Factors Implanted Biotherapy for Spinal Fusion: A Review of Human Clinical Studies

BACKGROUND

Owing to their great promise in the spinal surgeries, bone graft substitutes have been widely investigated for their safety and clinical potential. By the current advances in the spinal surgery, an understanding of the precise biological mechanism of each bone graft substitute is mandatory for upholding the induction of solid spinal fusion.

OBJECTIVE

The aim of the present review is to critically discuss various surgical implications and level of evidence of most commonly employed bone graft substitutes for spinal fusion.

METHOD

Data was collected via electronic search using "PubMed", "SciFinder", "ScienceDirect", "Google Scholar", "Web of Science" and a library search for articles published in peer-reviewed journals, conferences, and e-books.

RESULTS

Despite having exceptional inherent osteogenic, osteoinductive, and osteoconductive features, clinical acceptability of autografts (patient's own bone) is limited due to several perioperative and postoperative complications i.e., donor-site morbidities and limited graft supply. Alternatively, allografts (bone harvested from cadaver) have shown great promise in achieving acceptable bone fusion rate while alleviating the donor-site morbidities associated with implantation of autografts. As an adjuvant to allograft, demineralized bone matrix (DBM) has shown remarkable efficacy of bone fusion, when employed as graft extender or graft enhancer. Recent advances in recombinant technologies have made it possible to implant growth and differentiation factors (bone morphogenetic proteins) for spinal fusion.

CONCLUSION

Selection of a particular bone grafting biotherapy can be rationalized based on the level of spine fusion, clinical experience and preference of orthopaedic surgeon, and prevalence of donor-site morbidities.

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

Study Design

Prospective observational cohort study.

Purpose

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

Overview of Literature

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

Methods

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

Results

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

Conclusions

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

rhBMP in lumber fusion for lumbar spondylolisthesis: A systematic review and meta-analysis

PURPOSE

To compare the efficacy and safety of recombinant human bone morphogenetic protein (rhBMP) and iliac crest autograft in the fusion treatment of lumbar spondylolisthesis.

METHODS

The studies using randomized controlled trials to compare the rhBMP with iliac crest autograft in the treatment of lumbar spondylolisthesis were retrieved from Embase, Pubmed, ProQuest dissertations & theses (PQDT), China national knowledge infrastructure (CNKI), Chinese Biomedical Database, Wanfang Data, Cochrane Library (from March 1998 to March 2018). Postoperative fusion rate, clinical success rate, postoperative intervertebral height, complications, operation time, blood loss and duration of hospitalization were chosen as the outcome indicators. Methodological quality of the trials was critically assessed, and relevant data were extracted. Statistical software Revman 5.3 was used for data-analysis.

RESULTS

Eleven articles were included in the meta-analysis. The results showed that, comparing the efficacy of rhBMP with iliac crest autograft, statistical significance was found in the 24-month fusion rate post operation [95% CI (1.38, 24.70), p = 0.02] and operation time [95% CI (-14.22, -2.08), p = 0.008]. There is not sufficient evidence for statistical differences in the remaining indicators.

CONCLUSION

The current literature shows rhBMP is a safe and effective grafting material in the treatment of lumbar spondylolisthesis. Further evidence is dependent on the emergence of more randomized controlled trials with higher quality and larger sample sizes in the future.

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.

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

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

Efficacy of Early Fusion With Local Bone Graft and Platelet-Rich Plasma in Lumbar Spinal Fusion Surgery Followed Over 10 Years

STUDY DESIGN

Prospective clinical study.

OBJECTIVE

Many oral surgeons use platelet-rich plasma (PRP) for bone defects, but the efficacy of PRP for spinal arthrodesis remains uncertain. The objective was to compare the efficacy of autologous local bone graft and PRP with local bone graft alone for promotion of bony union in posterolateral lumbar fusion (PLF) surgery, with investigation of the safety of PRP over 10 years.

METHODS

A prospective study was conducted in 29 consecutive patients who underwent one-level PLF at L4/5 for degenerative lumbar disease. Local bone on the left (control) side and local bone with PRP on the right side were grafted. The fusion area and absorption of grafted bone at 58 regions were determined using computed tomography at 2 weeks and 3, 6, and 12 months after surgery.

RESULTS

Average bone fusion areas on the PRP side were significantly wider at 3 and 6 months after surgery (P < .05). Average absorption values were significantly lower on the PRP side than on the control side at 3 and 6 months after surgery (P < .05). The PRP/control ratio was significantly different at 3 and 6 months compared to that at 2 weeks (P < .005). No adverse events related to PRP occurred with good clinical outcome over 10 years follow-up.

CONCLUSIONS

Local application of PRP combined with autologous local bone graft has a positive impact on early fusion for lumbar arthrodesis with no adverse events over 10 years, and thus is a safe and low cost autologous option in spinal fusion.

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.

Complications Associated With Bone Morphogenetic Protein in the Lumbar Spine

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

Quiescent pluripotent stem cells reside within murine peripheral nerves that can be stimulated to proliferate by recombinant human bone morphogenic protein 2 or by nerve trauma

BACKGROUND

The clinical use of recombinant human bone morphogenic protein 2 (rhBMP-2, Infuse) has been associated with nerve-related complications including new-onset sciatica, and retrograde ejaculation.

PURPOSE

To better understand the interaction of rhBMP-2 and peripheral nerves with the intent of making procedures safer.

STUDY DESIGN/SETTING

Using a mouse model to examine the direct effect of diluted rhBMP-2 (Infuse) on murine sciatic nerves.

METHODS

Animal studies were approved by the Institutional Animal Care and Use Committee. Balb/c mouse sciatic nerves were surgically exposed and 60 ng (in 10 µL) of rhBMP-2 was applied to the nerve. In separate experiments, the sciatic nerves were subjected to mechanical compression using forceps (and not exposed to rhBMP-2). The third group of mice received direct injection of the same amount of rhBMP-2, or sterile saline as a control, into the hamstring area of the posterior thigh without surgery. Mouse limbs with intact sciatic nerve were collected at 24, 48, or 72 hours after treatment for histology processing. A separate set of identically treated sciatic nerves were retrieved from mice at the same time points and cells were isolated by collagenase and trypsin digestion. The isolated cells were cultured in a stem cell medium containing 20% knockout serum and human leukemia inhibitory factor. Immunohistochemical or immunofluorescent cell stains against KLF4, Sox2, c-Myc, and Oct4 were performed on the mouse tissue sections and cell culture slides. In addition, real-time polymerase chain reaction (PCR) was performed to quantify the mRNA expression profiles of the stem cell marker genes in cultured cells.

RESULTS

Profound morphological changes of the mouse sciatic nerves were noted after exposure to rhBMP-2, with a rapid and robust cell proliferation within the nerves followed by migration of these cells into surrounding tissue. Immunohistochemical stain revealed strong nuclear stains of KLF4, Sox2, Oct4, and c-Myc on the overwhelming majority of these proliferating cells in the nerve. Intramuscular injections of rhBMP-2 or willful physical compression of the nerves showed similar cell proliferation effects as the direct application of Infuse to the sciatic nerve. The cells in stem cell culture medium grew steadily without feeder cells and appeared fairly uniform. They were adherent to substrate and were motile. Double fluorescent staining on the cells indicated colocalizationof all pairs of the four stem cell markers in the cell nuclei. Real-time PCR confirmed the strong mRNA expressions of KLF4, Sox2, Oct4, and c-Myc in these isolated cells.

CONCLUSION

Exposure to BMP-2 causes a marked proliferation of previously quiescent cells within peripheral nerves. These cells simultaneously express KLF4, Sox2, Oct4, and c-Myc, the transcription factors that confer embryonic pluripotency. Work described in the companion paper reveals some of the differentiation capacity of the cells and their likely clinical significance. In addition, the effects of direct exposure of nerves to rhBMP-2 as described here should clearly illuminate the mechanism of BMP-2-related nerve complications. We would suggest that the use of this agent in proximity to known neural structures should only be done with extreme caution.

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

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Enhancement of posterolateral lumbar spine fusion using recombinant human bone morphogenetic protein-2 and mesenchymal stem cells delivered in fibrin glue

Mesenchymal stem cells have shown great potential for accelerating bone healing. In the present study, we evaluate the efficacy of fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 composite for posterolateral spinal fusion in a rabbit model. Forty adult rabbits underwent posterolateral intertransverse fusion at the L5–L6 level. The animals were randomly divided into four groups based on the implant material: fibrin glue, fibrin glue/mesenchymal stem cells composite, fibrin glue-recombinant human bone morphogenetic protein-2 (fibrin glue/recombinant human bone morphogenetic protein-2) composite, and fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 composite. After six weeks, the rabbits were euthanized for manual palpation, radiographic examination, biomechanical testing, and histology. Manual palpation results showed that the fusion rate for fibrin glue, fibrin glue/mesenchymal stem cells, fibrin glue/recombinant human bone morphogenetic protein-2, and fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 was 0, 0, 40%, and 70%, respectively. Moreover, fusion rate determined by radiographic examination for fibrin glue, fibrin glue/mesenchymal stem cells, fibrin glue/recombinant human bone morphogenetic protein-2, and fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 was 0, 0, 40%, and 80%, respectively. Gray analysis showed that fibrin glue/recombinant human bone morphogenetic protein-2 group had higher ossification area and density than fibrin glue group; and fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 group had higher ossification area and density than fibrin glue/recombinant human bone morphogenetic protein-2 group. Formation of continuous bone masses between L5 and L6 level in mesenchymal stem cells/recombinant human bone morphogenetic protein-2/fibrin glue group was further confirmed by computed tomography scanning and three-dimensional reconstruction. Biomechanical testing demonstrated that the fusion strength (flexion, extension, lateral bending, and axial rotation) in fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 group is significantly higher than that in fibrin glue/recombinant human bone morphogenetic protein-2 group. The formation of mature bone tissues between transverse processes of the fused specimens from both fibrin glue/recombinant human bone morphogenetic protein-2, and fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 groups was confirmed by HE staining, and quantitative real-time polymerase chain reaction results showed the upregulation of CD31, type I collagen, osteocalcin, and osteonectin in the fibrin glue/mesenchymal stem cells/recombinant human bone morphogenetic protein-2 group. In conclusion, our findings show that mesenchymal stem cells delivered with recombinant human bone morphogenetic protein-2 using fibrin glue as carrier are more effective in enhancing spine fusion than recombinant human bone morphogenetic protein-2 without mesenchymal stem cells in the rabbit model.

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.

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.

Comparison of rhBMP-2 versus Autogenous Iliac Crest Bone Graft for 2-Level Anterior Cervical Discectomy and Fusion for Cervical Spondylotic Myelopathy

Background

Few studies have examined the efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2) in 2-level anterior cervical discectomy and fusion (ACDF). The purpose of this study was to compare the outcomes in a series of patients with CSM treated with 2-level ACDF with or without rhBMP-2.

Material/Methods

The retrospective study included a total of 146 patients with CSM. The rhBMP-2 group consisted of 73 patients who underwent 2-level ACDF with rhBMP-2. A total of 73 patients who also received 2-level ACDF with autogenous ICBG alone were included in the matched-pair ICBG group with a ratio of 1:1, based on age, sex, and BMI. All data, including fusion rate and time, VAS, JOA score, operative date, and complications, were assessed.

Results

With respect to the length of hospital stay, operative times, and blood loss, there were no significant difference between the 2 groups. However, the rhBMP-2 group presented a shorter fusion time (P<0.013) and higher fusion rate (P<0.036) than the ICBG group. In the rhBMP-2 group, 22% required additional treatment for complications compared to 18% of patients in the ICBG group, which showed no significant difference (P=0.543).

Conclusions

The application of rhBMP-2 in 2-level ACDF showed higher fusion rates, shorter fusion time, and similar function outcomes compared to those who received ACDF with ICBG alone.

Safety and efficacy of recombinant human bone morphogenetic protein 2 on cranial defect closure in the pediatric population

BACKGROUND

Traditional reconstructive options for cranial defects include autogenous bone graft, bone substitutes, and synthetic materials. The established standard for repairing cranial defects is autogenous bone. However, young children do not have abundant donor sites for bone harvest, which leads to challenges in closing calvarial defects. Synthetic materials are not ideal alternatives because they require subsequent retrieval and are prone to infection. Their long-term effects on growth of the skull are also not well studied. Bone morphogenetic protein 2 (BMP-2), are shown to positively affect closure of cranial defects in animal models. We present a study comparing the efficacy and safety of closure of cranial defect with bone graft augmented with recombinant human BMP-2 (rhBMP-2) and compared with a series of patients treated with bone graft alone.

METHODS

This study is a retrospective multicenter evaluation of 36 patients spanning 5 years. Twenty-one patients undergoing cranial defect closure augmented with rhBMP-2 were compared with 15 patients who underwent cranial defect closure using cranial bone shavings alone. We measured preoperative and postoperative defect size on volumetric computed tomographic scan reconstructions to compare defect sizes.

RESULTS

The rhBMP-2 group had slightly increased proportional closure compared with the control group, 86% versus 76% (P < 0.018), respectively. Two patients in the rhBMP-2 group had postoperative fusion of a suture that was known to be patent at the time of cranial defect closure. No instances of brain edema, herniation, airway compromise, or other adverse effects directly attributable to rhBMP-2 were observed.

CONCLUSIONS

Bone morphogenetic protein 2 may increase the amplitude and uptake of cranial bone grafts in cranial defect closure. This study shows that defect sizes of up to 16 cm can be reliably closed using this technique. Postoperative fusion of uninvolved sutures in 2 patients indicates that rhBMP-2 may have unreported adverse effects; consideration of this finding should be weighed against the benefit of improved closure of calvarial defects.

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.

Posterolateral Lumbar Arthrodesis With and Without Interbody Arthrodesis for L4-L5 Degenerative Spondylolisthesis: A Comparative Value Analysis

STUDY DESIGN

Independent retrospective review of prospectively collected data, comparative cohort study.

OBJECTIVE

The objective of this study was to compare the clinical, radiographical, and cost/value of the addition of an interbody arthrodesis (IBA) to a posterolateral arthrodesis (PLA) in the surgical treatment of L4-L5 degenerative spondylolisthesis (DS). The authors hypothesized that the addition of IBA to PLA would produce added value while incurring minimal additional costs.

SUMMARY OF BACKGROUND DATA

Many lumbar surgical advances have been made during the past several decades, yet there is a paucity of strong evidence-based validation, let alone comparative value analyses. The addition of an IBA to a PLA has become increasingly popular during the past 2 decades, yet the potential added value for the patient has not been carefully defined.

METHODS

Patients undergoing single-level arthrodesis for L4-L5 DS performed at our institution from 2004 to 2012 were identified. Exclusion criteria included multilevel arthrodesis, spinal stenosis requiring decompression at or above L2-L3, previous L4-L5 spinal fusion, spondylolisthesis of greater than 33% of the vertebral body, and use of minimally invasive surgery. Radiographical fusion status, epidemiological, surgical, and functional outcomes, and cost/value data were recorded or calculated.

RESULTS

A total of 179 patients with follow-up meeting inclusion criteria were identified: 68 with PLA alone and 111 with PLA + IBA. No statistical differences were noted in Oswestry Disability Index, 36-item Short-Form Health Survey scores, fusion rates, or cost/value at 6 months and at more than 3 years despite the PLA cohort being significantly older with more medical comorbidities. When length of stay was normalized across cohorts, the addition of an IBA increased hospital costs ranging from $577 to $5276, but this did not reach statistical significance.

CONCLUSION

This single-center review of open surgical treatment of L4-L5 DS demonstrated that the addition of IBA to PLA added cost while producing equivalent results in fusion rates, Oswestry Disability Index, and 36-item Short-Form Health Survey scores when compared with PLA alone.

LEVEL OF EVIDENCE

3.

Posterolateral lumbar fusion using Escherichia coli-derived rhBMP-2/hydroxyapatite in the mini pig

BACKGROUND CONTEXT

Hydroxyapatite (HA) is used as a bone graft extender for posterolateral spinal fusion in human. It is also useful as a recombinant human bone morphogenetic protein (rhBMP)-2 carrier because of its high affinity for rhBMP-2.

PURPOSE

To assess the osteoinductivity of Escherichia coli-derived rhBMP-2 (E-BMP-2) using HA granules as a carrier and to evaluate the bone-forming ability depending on the different dosages of E-BMP-2.

STUDY DESIGN

A mini-pig lumbar posterolateral fusion model using microcomputed tomography (μCT) scanning.

PATIENT SAMPLE

Thirty-one adult male mini pigs were randomized into a single control group (n=8) without E-BMP-2 and two experimental groups with two different doses of E-BMP-2 (1 mg per side, n=8 and 3 mg per side, n=15).

OUTCOME MEASURES

Outcome was measured by plain radiography, manual palpation, CT, three-dimensional μCT, and histologic examinations.

METHODS

Bilateral intertransverse process arthrodesis was performed, and E-BMP-2 (0, 1.0, 3.0 mg per side) was implanted into the intertransverse space using HA granules as a carrier.

RESULTS

Three mini pigs were removed because of death. Among 28 experimental subjects, 19 animals achieved solid bony union. The fusion rates were 37.5% for control group, 71.4% for 1 mg group, and 84.6% for 3 mg group. Fusion rates were significantly different among groups (p=.031). However, there was no statistically significant difference in fusion rates between 1 and 3 mg groups (p=.587). Thirty-eight intertransverse fusion masses of 19 subjects underwent μCT scanning. The bone volumes determined by μCT were 12,603±3,240 mm(3) for control group, 18,718±3,000 mm(3) for 1 mg group, and 26,768±7,256 mm(3) for 3 mg group, and the difference between groups was statistically significant (p<.001).

CONCLUSIONS

This study shows that E-BMP-2 has osteoinductive activity in dose-dependent fashion, and porous HA granule is suitable for E-BMP-2 carrier in a porcine posterolateral fusion model. These preliminary findings suggest that E-BMP-2-adsorbed porous HA granules could be a novel effective bone graft substitute.

Growth factors in orthopaedic surgery: demineralized bone matrix versus recombinant bone morphogenetic proteins

During recent decades the utilisation of growth factors, especially BMPs, has received an increasing interest in orthopaedic surgery. For clinical implantation the two main options are demineralised bone matrix (DBM) and recombinant bone morphogenetic proteins (rhBMP). Many clinical studies agree on an equivalent osteoinductive effect between DBM, BMPs and autologous bone graft; however, the different origins and processing of DBM and rhBMP may introduce some fluctuations. Their respective characteristics are reviewed and possible interactions with their effectiveness are analysed. The main difference concerns the concentration of BMPs, which varies to an order of magnitude of 10(6) between DBM and rhBMPs. This may explain the variability in efficiency of some products and the adverse effects. Currently, considering osteoinductive properties, safety and availability, the DBM seems to offer several advantages. However, if DBM and rhBMPs are useful in some indications, their effectiveness and safety can be improved and more evidence-based studies are needed to better define the indications.

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

STUDY DESIGN

A retrospective cohort study with medical record review.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

3.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 16: bone graft extenders and substitutes as an adjunct for lumbar fusion

In an attempt to enhance the potential to achieve a solid arthrodesis and avoid the morbidity of harvesting autologous iliac crest bone (AICB) for a lumbar fusion, numerous alternatives have been investigated. The use of these fusion adjuncts has become routine despite a lack of convincing evidence demonstrating a benefit to justify added costs or potential harm. Potential alternatives to AICB include locally harvested autograft, calcium-phosphate salts, demineralized bone matrix (DBM), and the family of bone morphogenetic proteins (BMPs). In particular, no option has created greater controversy than the BMPs. A significant increase in the number of publications, particularly with respect to the BMPs, has taken place since the release of the original guidelines. Both DBM and the calciumphosphate salts have demonstrated efficacy as a graft extender or as a substitute for AICB when combined with local autograft. The use of recombinant human BMP-2 (rhBMP-2) as a substitute for AICB, when performing an interbody lumbar fusion, is considered an option since similar outcomes have been observed; however, the potential for heterotopic bone formation is a concern. The use of rhBMP-2, when combined with calcium phosphates, as a substitute for AICB, or as an extender, when used with local autograft or AICB, is also considered an option as similar fusion rates and clinical outcomes have been observed. Surgeons electing to use BMPs should be aware of a growing body of literature demonstrating unique complications associated with the use of BMPs.

Point-counter-point debate: the association between recombinant human bone morphogenetic protein utilization and complications in spine surgery

Bone morphogenetic proteins (BMPs) have been utilized in spine surgery for over 10 years as a bone graft substitute. Potential BMP-related adverse effects including retrograde ejaculation and heterotopic neuroforaminal bone formation have been described. Additionally, some studies have suggested an association between BMP and cancer. Inconsistencies exist in the published spine literature with regards to the incidence and association of complications with BMP utilization. In a point-counterpoint format, this article discusses the current evidence concerning the relationship between the utilization of BMP in spinal fusion and the risk of cancer, retrograde ejaculation (RE), neuroforaminal bone formation, and its role in anterior cervical spine surgery and adolescents.

Posterior lumbar fusion: choice of approach and adjunct techniques

The choice among the many options of approach and adjunct techniques in planning a posterior lumbar fusion can be problematic. Debates remain as to whether solid fusion has an advantage over pseudarthrosis regarding long-term symptom deterioration and whether an instrumented or a noninstrumented approach will best serve clinically and/or cost effectively, particularly in elderly patients. Increased motion resulting in higher rates of nonunion and the use of nonsteroidal anti-inflammatory drugs have been studied in animal models and are presumed risk factors, despite the lack of clinical investigation. Smoking is a proven risk factor for pseudarthrosis in both animal models and level III clinical studies. Recent long-term studies and image/clinical assessment of lumbar fusions and pseudarthrosis show that, although imaging remains a key area of difficulty in assessment, including an instrumented approach and a well-selected biologic adjunct, as well as achieving a solid fusion, all carry important long-term clinical advantages in avoiding revision surgery for nonunion.

Comparing the process of creeping substitution between allograft bone and local bone grafting in lumbar interbody fusion

PURPOSE

A self-control study was designed to compare the process of creeping substitution between allograft bone and local bone grafting in lumbar interbody fusion.

METHODS

From December 2011 to July 2012, 81 patients (mean age: 56.4) were included in this study and randomly allocated to two groups. Leopard cages were using in unilateral instrumentation transforaminal lumbar interbody fusion. In group 1, the cages were filled with the local bone on the side of the instrumentation and allograft bone on the other side. In group 2, they were totally filled with the local bone chips. Then, the special CT-reconstructions were made at 6- and 12-month follow-up. On the sagittal section, the sections of CT-reconstructions were perpendicular to the lateral axis of the cage from the side of the cage to the other side. Similarly, they were parallel to the lateral axis of the cage on the coronal section and intervertebral space on the cross section. The mean area size of bone mass on both sides of the cage was calculated, respectively, using image analysis software (Osirix, version 3.3.2) on each section in two groups.

RESULTS

In group 1, at 6- and 12-month follow-up, significant differences were observed in the mean area size of bone mass between allograft bone and local bone grafting on the coronal, cross, and sagittal section. In group 2, the mean area size of local bone on both sides of the cage had no significant differences at 6- and 12-month follow-up on each section.

CONCLUSIONS

The results of our study showed a superiority of local bone grafting over allograft bone.

Use of autogenous bone graft compared with RhBMP in high-risk patients: a comparison of fusion rates and time to fusion

STUDY DESIGN

A retrospective study.

OBJECTIVE

To evaluate whether recombinant human bone morphogenetic protein (rhBMP-2) can improve fusion rates and time to fusion in high-risk patients when compared with autograft in lumbar posterolateral fusion.

SUMMARY OF BACKGROUND DATA

The use of rhBMP-2 in the general population for posterolateral fusion has resulted in relatively good reported outcomes; however, it is currently considered "off-label" use. Few studies, however, have determined the outcomes of rhBMP-2 when used in patients with numerous risk factors for a pseudarthrosis.

METHODS

One hundred ninety-five patients were divided into 4 groups depending on fusion material and the presence/absence of fusion-related risk factors for nonunions; group A was defined as rhBMP-2 used in the presence of high-risk factors (FRRF), group B was defined as rhBMP-2 used in the absence of FRRF, group C was defined as autograft used in the presence of FRRF, and group D was defined as autograft used in the absence of FRRF. The time to fusion, fusion rate were compared between each group.

RESULTS

The time to fusion was significantly faster in group B than in group D in patients with no history of smoking (P<0.05), hypertension (P<0.01), or other significant comorbidity (P<0.05). The time to complete fusion was also significantly faster in group B than in group D in patients under the age of 65 (P<0.05), patients undergoing primary surgery (P<0.05), single-level surgery (P<0.01), no smoking history (P<0.05), no diabetes mellitus (P<0.01), no hypertension (P=0.001), no osteoporosis (P<0.01), and no significant comorbidity (P<0.01). Although the fusion rate was higher in group B than in group D, with the exception of sex and single-level surgery, there were no significant differences between groups B and D. Although initial fusion mass and time to solid fusion was faster in group A than in group C, there were no significant differences between groups A and C. In addition, fusion rates were higher in group C than in group A, looking at all factors except revision surgery, but the differences were not statistically significant.

CONCLUSIONS

With relative low dosage of rhBMP-2 compared with the dose used in Food and Drug Administration trial, in patients without fusion-related risk factors, rhBMP-2 may lead to acceptable fusion rates and faster fusion time when compared with autograft. Therefore, rhBMP-2 may serve as an acceptable alternative to autogenous bone graft in patients without fusion-related risk factors undergoing instrumented posterolateral lumbar fusions. When compared with patients with fusion-related risk factors, the use of rhBMP-2 was comparable with autograft but was not sufficient to overcome all aspects of the weakened osteoinductive capacity encountered in patients with these risk factors.

In vitro and in vivo evaluation of bone formation using solid freeform fabrication-based bone morphogenic protein-2 releasing PCL/PLGA scaffolds

The aim of this study was to develop novel polycaprolactone/poly(lactic-co-glycolic acid) (PCL/PLGA) scaffolds with a heparin-dopamine (Hep-DOPA) conjugate for controlled release of bone morphogenic protein-2 (BMP-2) to enhance osteoblast activity in vitro and also bone formation in vivo. PCL/PLGA scaffolds were prepared by a solid freeform fabrication method. The PCL/PLGA scaffolds were functionalized with Hep-DOPA and then BMP-2 was sequentially coated onto the Hep-DOPA/PCL/PLGA scaffolds. The characterization and surface elemental composition of all scaffolds were evaluated by scanning electron microscope and x-ray photoelectron spectroscopy. The osteoblast activities on all scaffolds were assessed by cell proliferation, alkaline phosphatase (ALP) activity and calcium deposition in vitro. To demonstrate bone formation in vivo, plain radiograph, micro-computed tomography (micro-CT) evaluation and histological studies were performed after the implantation of all scaffolds on a rat femur defect. Hep-DOPA/PCL/PLGA had more controlled release of BMP-2, which was quantified by enzyme-linked immunosorbent assay, compared with Hep/PCL/PLGA. The in vitro results showed that osteoblast-like cells (MG-63 cells) grown on BMP-2/Hep-DOPA/PCL/PLGA had significantly enhanced ALP activity and calcium deposition compared with those on BMP-2/Hep/PCL/PLGA and PCL/PLGA. In addition, the plain radiograph, micro-CT evaluation and histological studies demonstrated that the implanted BMP-2/Hep-DOPA/PCL/PLGA on rat femur had more bone formation than BMP-2/Hep/PCL/PLGA and PCL/PLGA in vivo.

Efficacy of rhBMP-2 versus iliac crest bone graft for posterior C1-C2 fusion in patients older than 60 years

Few studies have specifically examined the efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2)/absorbable collagen sponge (ACS) in posterolateral lumbar spine fusion. The purpose of this study was to report the clinical outcomes in elderly patients treated with posterior C1-C2 fusion with iliac crest bone graft (ICBG) plus rhBMP-2/ACS vs ICBG alone. One hundred forty patients older than 60 years were enrolled in this prospective, randomized trial and underwent instrumented C1- C2 fusion. Patients were divided into 2 groups based on fusion material. The ICBG group comprised patients who received ICBG alone, and the rhBMP-2/ACS group comprised patients who received ICBG plus rhBMP-2/ACS. The groups were compared based on operative time, estimated blood loss, hospital length of stay, clinical results, perioperative complications, fusion rate, fusion time, and revision rate. There were no significant differences in operative time, estimated blood loss, length of stay, and intraoperative complications between the 2 groups. Improvements in visual analog scale scores and Japanese Orthopaedic Association scores over the 2-year follow-up period were similar between groups. The fusion rate was 82.4% (56 of 68) in the rhBMP-2/ACS group and 78.7% (52 of 66) in the ICBG group (P=.782). Mean fusion time was 11 days shorter in the rhBMP-2/ACS group (81.8±29.4 days) than in the ICBG group (92.9±23.7 days) (P=.034). There were more wound complications requiring treatment in the rhBMP-2/ACS group (n=6; 8.8%) than in the ICBG group (n=2; 3.0%), although this was not statistically significant (P=.118). The use of rhBMP-2/ACS for posterior C1-C2 fusion appears to result in a relatively shorter fusion time, but there may be an increased risk of posterior cervical wound complications.

rhBMP-2 for posterolateral instrumented lumbar fusion: a multicenter prospective randomized controlled trial

STUDY DESIGN

Multicenter randomized controlled trial.

OBJECTIVE

To evaluate the effect of recombinant human bone morphogenetic protein (rhBMP-2) on radiographical fusion rate and clinical outcome for surgical lumbar arthrodesis compared with iliac crest autograft.

SUMMARY OF BACKGROUND DATA

In many types of spinal surgery, radiographical fusion is a primary outcome equally important to clinical improvement, ensuring long-term stability and axial support. Biologic induction of bone growth has become a commonly used adjunct in obtaining this objective. We undertook this study to objectify the efficacy of rhBMP-2 compared with traditional iliac crest autograft in instrumented posterolateral lumbar fusion.

METHODS

Patients undergoing 1- or 2-level instrumented posterolateral lumbar fusion were randomized to receive either autograft or rhBMP-2 for their fusion construct. Clinical and radiographical outcome measures were followed for 2 to 4 years postoperatively.

RESULTS

One hundred ninety seven patients were successfully randomized among the 8 participating institutions. Adverse events attributable to the study drug were not significantly different compared with controls. However, the control group experienced significantly more graft-site complications as might be expected. 36-Item Short Form Health Survey, Oswestry Disability Index, and leg/back pain scores were comparable between the 2 groups. After 4 years of follow-up, radiographical fusion rates remained significantly higher in patients treated with rhBMP-2 (94%) than those who received autograft (69%) (P = 0.007).

CONCLUSION

The use of rhBMP-2 for instrumented posterolateral lumbar surgery significantly improves the chances of radiographical fusion compared with the use of autograft. However, there is no associated improvement in clinical outcome within a 4-year follow-up period. These results suggest that use of rhBMP-2 should be considered in cases where lumbar arthrodesis is of primary concern.

The effect of zoledronic acid on the volume of the fusion-mass in lumbar spinal fusion

Background

Few studies have explored the effects of bisphosphonates on bony healing in patients undergoing spinal fusion surgery. Most previous studies used animal models and found that bisphosphonate shows negative effects on spinal fusion consolidation. We intended to evaluate the effect of a single-dose of zoledronic acid on the volume of the fusion-mass in lumbar spinal fusion.

Methods

A retrospective review was carried out on 44 patients with symptomatic degenerative lumbar spinal stenosis who underwent one or two-level posterolateral fusion from January 2008 and January 2011. They were divided into 4 groups: group 1, autograft and zoledronic acid; group 2, allograft and zoledronic acid; group 3, autograft alone; and group 4, allograft alone. Functional radiography and three-dimensional computed tomography scans were used to evaluate and quantify the volume of the fusion-mass. The visual analog scale (VAS), the Oswestry disability index (ODI), and the short form 36 (SF-36) were used to evaluate the clinical outcomes.

Results

The mean volume of the fusion-mass per level was 8,814 mm³, 8,035 mm³, 8,383 mm³, and 7,550 mm³ in groups 1, 2, 3, and 4, respectively, but there were no significant differences between the groups (p = 0.829). There were no significant decreases in the volume of the fusion-mass (p = 0.533) in the zoledronic acid groups (groups 1 and 2). The VAS, the ODI, and the SF-36 at the 6-month follow-up after surgery were not significantly different (p > 0.05) among the 4 groups. The VAS, the ODI, and the SF-36 were not correlated with the volume of the fusion-mass (p = 0.120, 0.609, 0.642).

Conclusions

A single dose of zoledronic acid does not decrease the volume of the fusion-mass in patients undergoing spinal fusion with osteoporosis. Therefore, we recommend that zoledronic acid may be used after spinal fusion in osteoporotic patients.

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.

Clinical sequelae after rhBMP-2 use in a minimally invasive transforaminal lumbar interbody fusion

BACKGROUND CONTEXT

Recent reports of postoperative radiculitis, bone osteolysis, and symptomatic ectopic bone formation after recombinant human bone morphogenetic protein-2 (rhBMP-2) use in transforaminal lumbar interbody fusions (TLIFs) are a cause for concern.

PURPOSE

To determine the clinical and radiographic complications associated with BMP utilization in a minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) environment.

STUDY DESIGN/SETTING

Retrospective clinical case series at a single institution.

PATIENT SAMPLE

Five hundred seventy-three consecutive patients undergoing an MIS-TLIF.

OUTCOME MEASURES

Reoperation rates and total costs associated with complications of rhBMP-2 use and pseudarthrosis.

METHODS

A retrospective review of 610 consecutive patients undergoing an MIS-TLIF (2007-2010) by a single surgeon at our institution was performed (mean age 48.7 years, range 26-82 years). All patients underwent an MIS laminectomy with bilateral facetectomy, single TLIF cage, unilateral pedicle screw fixation, and 12 mg (large kit) or 4.2 mg (small kit) of rhBMP-2. The BMP-2 collagen-soaked sponge was placed anteriorly in the disc space, followed by local bone graft, and then the cage was filled only with local bone and no BMP-2. Patients were evaluated at 6 months and 1 year with computed tomography (CT) scan. Those demonstrating neuroforaminal bone growth, osteolysis/cage migration, or pseudarthrosis were reviewed, and cost data including direct cost/procedure for both index and revision surgeries were collected.

RESULTS

Of the 573 patients, 10 (1.7%) underwent 15 additional procedures based on recalcitrant radiculopathy and CT evidence of neuroforaminal bone growth, vertebral body osteolysis, and/or cage migration. Thirty-nine patients (6.8%) underwent reoperation for clinically symptomatic pseudarthrosis. Bone overgrowth was associated with nerve impingement and radiculopathy in all 10 patients (small kit, n=9; large kit, n=1). Osteolysis and cage migration occurred in 2 (20%) of these same 10 patients. Average total costs were calculated per procedure ($19,224), and the costs for reoperation equaled $14,785 per encounter for neuroforaminal bone growth and $20,267 for pseudarthrosis.

CONCLUSIONS

Symptomatic ectopic bone formation, vertebral osteolysis, and pseudarthrosis are recognized complications with the use of rhBMP-2 in MIS-TLIFs. Potential causes include improper dosage and a closed space that prevents the egress of the postoperative BMP-2 fluid collection. Management of these complications has a substantial cost for the patient and the surgeon and needs to be considered with the off-label use of rhBMP-2.

RhBMP-2 is superior to iliac crest bone graft for long fusions to the sacrum in adult spinal deformity: 4- to 14-year follow-up

STUDY DESIGN

Matched cohort comparison.

OBJECTIVE

To compare the use of bone morphogenetic protein (BMP) or iliac crest bone graft (ICBG) on the long-term outcomes in patients undergoing long fusions to the sacrum for adult spinal deformity.

SUMMARY OF BACKGROUND DATA

No long-term studies beyond a 2-year follow-up have been performed comparing the use of BMP versus ICBG for fusion rates in long fusions to the sacrum in adult spinal deformity.

METHODS

A total of 63 consecutive patients, from 1997-2006, comprised of 31 patients in the BMP group and 32 patients in the ICBG group, operated on at a single institution with a minimum 4-year follow-up (4-14 yr) were analyzed. Inclusion criteria were ambulators who were candidates for long fusions (thoracic as the upper level) to the sacrum. Exclusion criteria were revisions, neuromuscular scoliosis, ankylosing spondylitis, and patients who had both BMP and ICBG used for fusion. Oswestry Disability Index and 3 domains of the Scoliosis Research Society score were used to assess outcomes.

RESULTS

The 2 groups were similar with respect to age, sex, smoking history, comorbidities, BMI, number of fusion levels and Cobb angles. Eight patients in the BMP group underwent a posterior only, whereas 23 underwent combined anterior and posterior (A/P) surgery. All 32 patients in the ICBG had A/P fusion. The average BMP level was 11.1 mg (3-36 mg). The rate pseudarthrosis was 6.4% (2/31) in the BMP and 28.1% (9/32) in the ICBG group (P = 0.04) using Fisher exact test and odds ratio = 5.67. The fusion rates for BMP group were 93.5% and 71.9% for the ICBG group. Oswestry Disability Indexes were similar between groups. However, the BMP group demonstrated superior sum composite Scoliosis Research Society scores in pain, self-image and function domains (P = 0.02).

CONCLUSION

BMP is superior to ICBG in achieving fusion in long constructs in adult deformity surgery. The rate of pseudarthrosis was significantly higher in the ICBG group than BMP group. The concentration and dosage of recombinant human bone morphogenetic protein 2 (rhBMP-2) used seems to have an effect on the rate of fusion and pseudarthrosis rate because no patient receiving more than 5 mg per level had apparent or detected pseudarthroses (n = 20/20).

LEVEL OF EVIDENCE

3.

Use of recombinant human bone morphogenetic protein-2 with local bone graft instead of iliac crest bone graft in posterolateral lumbar spine arthrodesis

STUDY DESIGN

Prospective clinical study.

OBJECTIVE

Compare fusion rates between recombinant human bone morphogenetic protein-2 (rhBMP-2) and iliac crest bone graft (ICBG) with rhBMP-2 and local bone graft (LBG) (±bone graft extenders) in posterolateral fusion.

SUMMARY OF BACKGROUND DATA

Previous reports have shown higher fusion rates when adding rhBMP-2 to ICBG in lumbar posterolateral fusion, compared with ICBG alone. We compared the fusion success rates between rhBMP-2 delivered with ICBG versus that with LBG.

METHODS

Fusion rates were compared in patients with degenerative spondylolisthesis (1-2 levels) with accompanying lumbar stenosis. RhBMP-2 (INFUSE, Medtronic) was delivered on an absorbable collagen sponge (6 mg/side at 1.5 mg/mL) with ICBG alone or with LBG wrapped inside the sponge. Thin slice computed tomographic scans were assessed at 6, 12, and 24 months.

RESULTS

In a consecutive series, 16 patients (30 levels) received ICBG with rhBMP-2 and 35 patients (49 levels) received LBG with rhBMP-2. For the ICBG cohort, 80.0%, 93.4%, 96.7% of levels were fused at 6, 12, and 24 months. In contrast, for the local bone with rhBMP-2 cohort, 87.7%, 98.0%, and 98.0% were fused at 6, 12, and 24 months. There was no statistically significant difference in fusion success rates between the 2 groups at any time point. As for fusion quality, the fusion mass showed superior quality in ICBG group than in the local bone group at each time point.

CONCLUSION

This study validates the high fusion success rates previously reported by adding rhBMP-2 to ICBG and shows that local bone may be safely substituted for ICBG in 1- to 2-level posterolateral fusion. The fusion rates were comparable. The avoidance of ICBG harvest has implications for operative time, blood loss, and morbidity. Lastly, this is the first study that directly compares the fusion success rate and quality using local bone with rhBMP-2 versus ICBG with rhBMP-2 at various times.

LEVEL OF EVIDENCE

4.

Changes in bone mineral density in the intertransverse fusion mass after instrumented single-level lumbar fusion: a prospective 1-year follow-up

STUDY DESIGN

Prospective cohort.

OBJECTIVE

The purpose of this study was to evaluate changes in bone mineral density (BMD) in the intertransverse fusion mass as representative for the process of bone remodeling after spinal fusion.

SUMMARY OF BACKGROUND DATA

Intertransverse bone graft is frequently applied to facilitate bony fusion between 2 spinal levels. The biological process of bone graft remodeling leading to eventual fusion is, however, poorly understood.

METHODS

In 20 patients with a single-level instrumented posterolateral lumbar fusion for low-grade spondylolisthesis, radiographs, and clinical outcome scores (visual analogue scale for back and leg pain, Oswestry Disability Index, Short Form-36) were obtained. Locally harvested laminectomy bone was used as intertransverse bone graft. The BMD in selected "regions of interest" at both intertransverse fusion areas was assessed on days 4 and 3, after a period of 6 and 12 months after surgery using dual-energy x-ray absorptiometry scans. Eventual fusion status was assessed on computed tomographic scan at 12 months.

RESULTS

All clinical outcome scores significantly improved at the final follow-up (P < 0.05). Baseline BMD in both paraspinal fusion areas was expressed as 100%, which significantly decreased from 81% to 75% and 77% to 70% at 3 and 6 months, for regions of interest 1 and 2, respectively (P < 0.001). From 6 to 12 months, there was an increase in BMD from 90% to 80%, for regions of interest 1 and 2 (P = 0.296). On computed tomography scan a complete fusion was noticed in 70% of the patients.

CONCLUSION

Repeated dual-energy x-ray absorptiometry was able to elucidate the biological process of bone graft remodeling in the intertransverse fusion mass. An active bone remodeling process was quantified with profound resorption or demineralization of the graft during the first 6 months, followed by subsequent bone apposition and restoration of BMD at the final follow-up. No difference in trend in BMD change between patients with and without fusion could be established; however, no firm conclusions can be drawn from small patient numbers.

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) in posterolateral lumbar spine fusion: complications in the elderly

Study design

Retrospective cohort study of 1430 patients undergoing lumbar spinal fusion from 2002 - 2009. Objective: The goal of this study was to compare and evaluate the number of complications requiring reoperation in elderly versus younger patients.

Summary of background data

rhBMP-2 has been utilized off label for instrumented lumbar posterolateral fusions for many years. Many series have demonstrated predictable healing rates and reoperations. Varying complication rates in elderly patients have been reported.

Materials and methods

All patients undergoing instrumented lumbar posterolateral fusion of ≤ 3 levels consenting to utilization of rhBMP-2 were retrospectively evaluated. Patient demographics, body mass index, comorbidities, number of levels, associated interbody fusion, and types of bone void filler were analyzed. The age of patients were divided into less than 65 and greater than or equal to 65 years. Complications related to the performed procedure were recorded.

Results

After exclusions, 482 consecutive patients were evaluated with 42.1% males and 57.9% females. Average age was 62 years with 250 (51.9%) < 65 and 232 (48.1%) ≥ 65 years. Patients ≥ 65 years of age stayed longer (5.0 days) in the hospital than younger patients (4.5 days) (p=0.005).

Complications requiring reoperation were: acute seroma formation requiring decompression 15/482, 3.1%, bone overgrowth 4/482, 0.8%, infection requiring debridement 11/482, 2.3%, and revision fusion for symptomatic nonunion 18/482, 3.7%. No significant differences in complications were diagnosed between the two age groups. Statistical differences were noted between the age groups for medical comorbidities and surgical procedures. Patients older than 65 years underwent longer fusions (2.1 versus 1.7 levels, p=0.001).

Discussion

Despite being older and having more comorbidities, elderly patients have similar complication and reoperation rates compared to younger healthier patients undergoing instrumented lumbar decompression fusions with rhBMP-2.

The effect of recombinant bone morphogenetic protein-2 in revision tibiotalocalcaneal arthrodesis: utilization of the Retrograde Arthrodesis Intramedullary Nail database

The use of bone morphogenetic protein-2 (BMP-2) has been recommended for high-risk fusions and nonunion. Patients undergoing revisional tibiotalocalcaneal (TTC) arthrodesis via a retrograde arthrodesis nail to evaluate the influence of BMP-2 on rate of fusion in this high-risk population are presented. A retrospective chart and radiographic review were performed on 23 patients with failed prior fusion attempts at the ankle treated with retrograde intramedullary nailing. Sixteen patients were treated without BMP-2 (None group) and 7 were treated with BMP-2 (BMP group). The primary and secondary end-points were successful fusion, and time to fusion, respectively, with a variety of variables evaluated for influence. Other than the use of BMP-2, there were no statistical differences in the patient population. Overall, 11 of 16 ankles (68.8%) in the None group and 5 of 7 ankles (71.4%) in the BMP group resulted in a stable, functional limb. Rate of complication was similar between the 2 groups (p > .05). Time to radiographic ankle union was 115.2 and 184.0 days in the None and BMP groups (p > .05). The effect of BMP-2 on revisional TTC fusions with retrograde nails is reported here. The overall result as a stable, functional limb was 69.6%, which suggests that revision surgery in this high-risk population is a reasonable consideration. Even though this study was unable to demonstrate statistically significant differences, biologic augmentation with BMP-2 did not increase the complication rate and showed a slightly enhanced salvage rate for revision TTC fusions with an intramedullary nail.