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

The risk of stroke after spinal fusion surgery: a national cohort study

BACKGROUND CONTEXT

Postoperative stroke is a rare complication of spinal fusion surgery, but its relevant risk and incidence remain unclear.

PURPOSE

To investigate the incidence and risk of stroke after spinal fusion surgery.

STUDY DESIGN

Cohort study.

PATIENT SAMPLE

All study subjects were extracted from a nationwide representative cohort of one million people from 2000 to 2005.

OUTCOME MEASURES

Stroke, including hemorrhagic and ischemic, during the study period.

METHODS

An exposure group of 2,249 subjects who received spinal fusion surgery during the study period was compared with 2,203 control subjects matched by age, sex, and propensity score. All were followed up for 3 years for all kinds of stroke. Demographics, comorbidities, and nonmeasurable covariates were matched between the two groups. Kaplan-Meier analyses were performed, with adjustments by Cox regression model.

RESULTS

There were 4,452 subjects, including 2,249 spinal fusion patients and 2,203 controls, who were followed up for 12,967 person-years. The incidence rates of any, hemorrhagic, and ischemic strokes were 9.95, 1.21, and 8.86, respectively, per 1,000 person-years in the spinal fusion group and 11.5, 1.69, and 9.93, respectively, in the comparison group. Patients who received spinal fusion surgery were less likely to have any stroke (crude hazard ratio [HR]=0.87, p=.393), hemorrhagic stroke (HR=0.72, p=.473), and ischemic stroke (HR=0.89, p=.582) than the comparison group but without statistical significance. After adjusting for demographics, comorbidities, and medications, there were still no significant differences for risks of any, hemorrhagic, and ischemic strokes (adjusted HR=0.89, 1.36, and 0.87; p=.522, .553, and .477, respectively) in the spinal fusion group.

CONCLUSIONS

Patients receiving spinal fusion surgery have similar incidence rates of having a stroke within 3 years postoperation as those without surgery. Risks of any postoperative stroke are similar or insignificantly lower in the spinal fusion group.

Endoscopic image-guided transcervical odontoidectomy: outcomes of 15 patients with basilar invagination

BACKGROUND

Ventral decompression with posterior stabilization is the preferred treatment for symptomatic irreducible basilar invagination. Endoscopic image-guided transcervical odontoidectomy (ETO) may allow for decompression with limited morbidity.

OBJECTIVE

To describe the perioperative outcomes of patients undergoing anterior decompression of basilar invagination with the use of ETO.

METHODS

Fifteen patients who had a follow-up of at least 16 months were retrospectively reviewed. Intraoperatively, the vertebral body of C2 was removed and the odontoid was resected in a "top-down" manner using endoscopic visualization and frameless stereotactic navigation. Posterior instrumented stabilization was subsequently performed.

RESULTS

The average (± standard deviation) age of the patients was 42.6 ± 24.5 (range, 11-72) years. Postoperative complications occurred in 6 patients, including a urinary tract infection (n = 2), upper airway swelling (n = 2), dysphagia (n = 2), gastrostomy tube placement (n = 1), and an asymptomatic pseudomeningocele (n = 1). No patients required a tracheostomy, had bacterial meningitis, or developed a venous thromboembolic event; only 1 patient was intubated for more than 48 hours postoperatively. With a mean follow-up of 41.9 ± 14.4 (range, 16-59) months, myelopathy improved in all patients and no patient experienced late neurological deterioration. The mean modified Japanese Orthopedic Association (JOA) score increased from 11.2 ± 4.2 to 15.9 ± 1.4 (P = .002). Patients with a diagnosis other than rheumatoid arthritis or who had a higher preoperative JOA score had a significantly better postoperative neurological recovery (P = .005).

CONCLUSION

ETO may be a valid treatment for patients with symptomatic irreducible basilar invagination that avoids some of the morbidity of transoral surgery and leads to long-term improvement in myelopathy.

[Spinal arthrodesis. basic science]

Spinal arthrodesis consists of a combination of a system of mechanical stabilisation of one or more vertebral segments with a biological substance that promotes osteoneogenesis, with aim of achieving the permanent fusion between areas more or less the same size of these segments. In spinal arthrodesis, the biological support par excellence is the autograft. However, obtaining this involves a high incidence of morbidity and, in cases of arthrodesis of more than one intervertebral space, the quantity available is usually insufficient. The extraction and implantation time prolongs the surgery, increasing the exposure to and risk of bleeding and infection. For these reasons, there is a search for substances that possess the properties of the autograft, avoiding the morbidity and added surgical time required to extract the autograft. The biomechanical-biological interaction in vertebral arthrodesis has been studied in this article.

Nonintegrating knockdown and customized scaffold design enhances human adipose-derived stem cells in skeletal repair

An urgent need exists in clinical medicine for suitable alternatives to available techniques for bone tissue repair. Human adipose-derived stem cells (hASCs) represent a readily available, autogenous cell source with well-documented in vivo osteogenic potential. In this article, we manipulated Noggin expression levels in hASCs using lentiviral and nonintegrating minicircle short hairpin ribonucleic acid (shRNA) methodologies in vitro and in vivo to enhance hASC osteogenesis. Human ASCs with Noggin knockdown showed significantly increased bone morphogenetic protein (BMP) signaling and osteogenic differentiation both in vitro and in vivo, and when placed onto a BMP-releasing scaffold embedded with lentiviral Noggin shRNA particles, hASCs more rapidly healed mouse calvarial defects. This study therefore suggests that genetic targeting of hASCs combined with custom scaffold design can optimize hASCs for skeletal regenerative medicine.

Enhancement of human adipose-derived stromal cell angiogenesis through knockdown of a BMP-2 inhibitor

BACKGROUND

Previous studies have demonstrated the role of noggin, a bone morphogenetic protein-2 inhibitor, in vascular development and angiogenesis. The authors hypothesized that noggin suppression in human adipose-derived stromal cells would enhance vascular endothelial growth factor secretion and angiogenesis in vitro and in vivo to a greater extent than bone morphogenetic protein-2 alone.

METHODS

Human adipose-derived stromal cells were isolated from human lipoaspirate (n = 6) noggin was knocked down using lentiviral techniques. Knockdown was confirmed and angiogenesis was assessed by tubule formation and quantitative real-time polymerase chain reaction. Cells were seeded onto scaffolds and implanted into a 4-mm critical size calvarial defect. In vivo angiogenic signaling was assessed by immunofluorescence and immunohistochemistry.

RESULTS

Human adipose-derived stromal cells with noggin suppression secreted significantly higher amounts of angiogenic proteins, expressed higher levels of angiogenic genes, and formed more tubules in vitro. In vivo, calvarial defects seeded with noggin shRNA human adipose-derived stromal cells exhibited a significantly higher number of vessels in the defect site than controls by immunohistochemistry (p < 0.05). In addition, bone morphogenetic protein-2-releasing scaffolds significantly enhanced vascular signaling in the defect site.

CONCLUSIONS

Human adipose-derived stromal cells demonstrate significant increases in angiogenesis in vitro and in vivo with both noggin suppression and BMP-2 supplementation. By creating a cell with noggin suppressed and by using a scaffold with increased bone morphogenetic protein-2 signaling, a more angiogenic niche can be created.

Synthetic scaffold coating with adeno-associated virus encoding BMP2 to promote endogenous bone repair

Biomaterial scaffolds functionalized to stimulate endogenous repair mechanisms via the incorporation of osteogenic cues offer a potential alternative to bone grafting for the treatment of large bone defects. We first quantified the ability of a self-complementary adeno-associated viral vector encoding bone morphogenetic protein 2 (scAAV2.5-BMP2) to enhance human stem cell osteogenic differentiation in vitro. In two-dimensional culture, scAAV2.5-BMP2-transduced human mesenchymal stem cells (hMSCs) displayed significant increases in BMP2 production and alkaline phosphatase activity compared with controls. hMSCs and human amniotic-fluid-derived stem cells (hAFS cells) seeded on scAAV2.5-BMP2-coated three-dimensional porous polymer Poly(ε-caprolactone) (PCL) scaffolds also displayed significant increases in BMP2 production compared with controls during 12 weeks of culture, although only hMSC-seeded scaffolds displayed significantly increased mineral formation. PCL scaffolds coated with scAAV2.5-BMP2 were implanted into critically sized immunocompromised rat femoral defects, both with or without pre-seeding of hMSCs, representing ex vivo and in vivo gene therapy treatments, respectively. After 12 weeks, defects treated with acellular scAAV2.5-BMP2-coated scaffolds displayed increased bony bridging and had significantly higher bone ingrowth and mechanical properties compared with controls, whereas defects treated with scAAV2.5-BMP2 scaffolds pre-seeded with hMSCs failed to display significant differences relative to controls. When pooled, defect treatment with scAAV2.5-BMP2-coated scaffolds, both with or without inclusion of pre-seeded hMSCs, led to significant increases in defect mineral formation at all time points and increased mechanical properties compared with controls. This study thus presents a novel acellular bone-graft-free endogenous repair therapy for orthotopic tissue-engineered bone regeneration.

Outcomes for single-level lumbar fusion: the role of bone morphogenetic protein

STUDY DESIGN

Retrospective analysis of a population-based insurance claims data set.

OBJECTIVE

To determine the risk of repeat fusion and total costs associated with bone morphogenetic protein (BMP) use in single-level lumbar fusion for degenerative spinal disease.

SUMMARY OF BACKGROUND DATA

The use of BMP has been proposed to reduce overall costs of spinal fusion through prevention of repeat fusion procedures. Although radiographic fusion rates associated with BMP use have been examined in clinical trials, few data exist regarding outcomes associated with BMP use in the general population.

METHODS

Using the MarketScan claims data set, 15,862 patients that underwent single-level lumbar fusion from 2003 to 2007 for degenerative disease were identified. Propensity scores were used to match 2372 patients who underwent fusion with BMP to patients who underwent fusion without BMP. Logistic regression models, Kaplan-Meier estimates, and Cox proportional hazards models were used to examine risk of repeat fusion, length of stay, and 30-day readmission by BMP use. Cost comparisons were evaluated with linear regression models using logarithmic transformed data.

RESULTS

At 1 year from surgery, BMP was associated with a 1.1% absolute decrease in the risk of repeat fusion (2.3% with BMP vs. 3.4% without BMP, P = 0.03) and an odds ratio for repeat fusion of 0.66 (95% confidence interval [CI] = 0.47-0.94) after multivariate adjustment. BMP was also associated with a decreased hazard ratio for long-term repeat fusion (adjusted hazards ratio = 0.74, 95% CI = 0.58-0.93). Cost analysis indicated that BMP was associated with initial increased costs for the surgical procedure (13.9% adjusted increase, 95% CI = 9.9%-17.9%) as well as total 1-year costs (10.1% adjusted increase, 95% CI = 6.2%-14.0%).

CONCLUSION

At 1 year, BMP use was associated with a decreased risk of repeat fusion but also increased health care costs.

Scaffold translation: barriers between concept and clinic

Translation of scaffold-based bone tissue engineering (BTE) therapies to clinical use remains, bluntly, a failure. This dearth of translated tissue engineering therapies (including scaffolds) remains despite 25 years of research, research funding totaling hundreds of millions of dollars, over 12,000 papers on BTE and over 2000 papers on BTE scaffolds alone in the past 10 years (PubMed search). Enabling scaffold translation requires first an understanding of the challenges, and second, addressing the complete range of these challenges. There are the obvious technical challenges of designing, manufacturing, and functionalizing scaffolds to fill the Form, Fixation, Function, and Formation needs of bone defect repair. However, these technical solutions should be targeted to specific clinical indications (e.g., mandibular defects, spine fusion, long bone defects, etc.). Further, technical solutions should also address business challenges, including the need to obtain regulatory approval, meet specific market needs, and obtain private investment to develop products, again for specific clinical indications. Finally, these business and technical challenges present a much different model than the typical research paradigm, presenting the field with philosophical challenges in terms of publishing and funding priorities that should be addressed as well. In this article, we review in detail the technical, business, and philosophical barriers of translating scaffolds from Concept to Clinic. We argue that envisioning and engineering scaffolds as modular systems with a sliding scale of complexity offers the best path to addressing these translational challenges.

Adult spine deformity

Adult spinal deformity may occur as the result of a number of conditions and patients may present with a heterogeneous group of symptoms. Multiple etiologies may cause spinal deformity; however, symptoms are associated with progressive and asymmetric degeneration of the spinal elements potentially leading to neural element compression. Symptoms and clinical presentation vary and may be related to progressive deformity, axial back pain, and/or neurologic symptoms. Spinal deformity is becoming more common as adults 55-64 years of age are the fastest growing proportion of the U.S. population. As the percentage of elderly in the United States accelerates, more patients are expected to present with painful spinal conditions, potentially requiring spinal surgery. The decision between operative and nonoperative treatment for adult spinal deformity is based on the severity and type of the patient's symptoms as well as the magnitude and risk of potential interventions.

Retrospective analysis of L5-S1 axial lumbar interbody fusion (AxiaLIF): a comparison with and without the use of recombinant human bone morphogenetic protein-2

BACKGROUND CONTEXT

Since approval by the Food and Drug Administration in 2002, use of recombinant human bone morphogenetic protein-2 (rhBMP-2) to promote spinal fusion is increasing.

PURPOSE

In this comparative analysis, the authors assess fusion rates and clinical outcomes of patients who underwent a presacral axial lumbar interbody fusion (AxiaLIF) (TranS1 Inc., Wilmington, NC, USA) at L5-S1 with posterior instrumentation, with or without rhBMP-2.

STUDY DESIGN

Retrospective case-matched chart review.

PATIENT SAMPLE

A matched cohort of 99 patients underwent fusion performed by two surgeons at two institutions (2005-2007): Specifically, 45 patients at The Christ Hospital received rhBMP-2 and 54 patients at the University of Pittsburgh had no rhBMP-2.

OUTCOME MEASURES

Pre- and postoperative visual analog scale (VAS) scores were recorded, as was physiologic data on fusion rates, blood loss, and length of stay. Preoperative and postoperative Oswestry Disability Index (ODI) scores were obtained for patients treated with rhBMP-2. Odom's outcome criteria were obtained at 2-year follow-up for patients without rhBMP-2.

METHODS

Data were collected prospectively. Demographic data, including sex and age, were matched.

RESULTS

During the 2-year follow-up period, patients noted reduction in back pain and improved functional outcome measures. The most rapid reduction in VAS pain scores and improvement in ODI occurred within the first 3 months after surgery. Mean pre- and postoperative VAS scores improved 59% from 72.9 to 30.1 with rhBMP-2 and 72% from 81.3 to 22.6 without rhBMP-2. In rhBMP-2-treated patients, mean ODI scores were 54.4% preoperatively and 23.7% postoperatively, a 56.4% improvement at 2 years. In the non-rhBMP-2 patients, 80% reported excellent to good results using Odom criteria. Fusion rates were 96% with rhBMP-2 and 93% without rhBMP-2. Operative blood loss averaged 82 cm(3) with and less than 50 cm(3) without rhBMP-2. No differences in hospital length of stay were noted between the two groups or in the fusion rates with pedicle screws or facet screws. No major complications occurred with or without rhBMP-2.

CONCLUSIONS

In our case-matched series, clinical outcomes were similar for patients who underwent an AxiaLIF L5-S1 interbody fusion with or without rhBMP-2. The data strongly suggest that there is a high confidence for no effect on fusion rate by using rhBMP-2.

Controllable mineral coatings on PCL scaffolds as carriers for growth factor release

In this study, we have developed mineral coatings on polycaprolactone scaffolds to serve as templates for growth factor binding and release. Mineral coatings were formed using a biomimetic approach that consisted in the incubation of scaffolds in modified simulated body fluids (mSBF). To modulate the properties of the mineral coating, which we hypothesized would dictate growth factor release, we used carbonate (HCO(3)) concentration in mSBF of 4.2 mm, 25 mm, and 100 mm. Analysis of the mineral coatings formed using scanning electron microscopy indicated growth of a continuous layer of mineral with different morphologies. X-ray diffraction analysis showed peaks associated with hydroxyapatite, the major inorganic constituent of human bone tissue in coatings formed in all HCO(3) concentrations. Mineral coatings with increased HCO(3) substitution showed more rapid dissolution kinetics in an environment deficient in calcium and phosphate but showed re-precipitation in an environment with the aforementioned ions. The mineral coating provided an effective mechanism for growth factor binding and release. Peptide versions of vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP2) were bound with efficiencies up to 90% to mineral mineral-coated PCL scaffolds. We also demonstrated sustained release of all growth factors with release kinetics that were strongly dependent in the solubility of the mineral coating.

Impact of total disc arthroplasty on the surgical management of lumbar degenerative disc disease: Analysis of the Nationwide Inpatient Sample from 2000 to 2008

Background:

Spinal fusion is the most rapidly increasing type of lumbar spine surgery for various lumbar degenerative pathologies. The surgical treatment of lumbar spine degenerative disc disease may involve decompression, stabilization, or arthroplasty procedures. Lumbar disc athroplasty is a recent technological advance in the field of lumbar surgery. This study seeks to determine the clinical impact of anterior lumbar disc replacement on the surgical treatment of lumbar spine degenerative pathology. This is a retrospective assessment of the Nationwide Inpatient Sample (NIS).

Methods:

The NIS was searched for ICD-9 codes for lumbar and lumbosacral fusion (81.06), anterior lumbar interbody fusion (81.07), and posterolateral lumbar fusion (81.08), as well as for procedure codes for revision fusion surgery in the lumbar and lumbosacral spine (81.36, 81.37, and 81.38). To assess lumbar arthroplasty, procedure codes for the insertion or replacement of lumbar artificial discs (84.60, 84.65, and 84.68) were queried. Results were assayed from 2000 through 2008, the last year with available data. Analysis was done using the lme4 package in the R programming language for statistical computing.

Results:

A total of nearly 300,000 lumbar spine fusion procedures were reported in the NIS database from 2000 to 2008; assuming a representative cross-section of the US health care market, this models approximately 1.5 million procedures performed over this time period. In 2005, the first year of its widespread use, there were 911 lumbar arthroplasty procedures performed, representing 3% of posterolateral fusions performed in this year. Since introduction, the number of lumbar spine arthroplasty procedures has consistently declined, to 653 total procedures recorded in the NIS in 2008. From 2005 to 2008, lumbar arthroplasties comprised approximately 2% of lumbar posterolateral fusions. Arthroplasty patients were younger than posterior lumbar fusion patients (42.8 ± 11.5 vs. 55.9 ± 15.1 years, P < 0.0000001). The distribution of arthroplasty procedures was even between academic and private urban facilities (48.5% and 48.9%, respectively). While rates of posterolateral lumbar spine fusion steadily grew during the period (OR 1.06, 95% CI: 1.05-1.06, P < 0.0000001), rates of revision surgery and anterior spinal fusion remained static.

Conclusions:

The impact of lumbar arthroplasty procedures has been minimal. Measured as a percentage of more common lumbar posterior arthrodesis procedures, lumbar arthroplasty comprises only approximately 2% of lumbar spine surgeries performed in the United States. Over the first 4 years following the Food and Drug Administration (FDA) approval, the frequency of lumbar disc arthroplasty has decreased while the number of all lumbar spinal fusions has increased.

Skeletal tissue regeneration: current approaches, challenges, and novel reconstructive strategies for an aging population

Loss of skeletal tissue as a consequence of trauma, injury, or disease is a significant cause of morbidity with often wide-ranging socioeconomic impacts. Current approaches to replace or restore significant quantities of lost bone come with substantial limitations and inherent disadvantages that may in themselves cause further disability. In addition, the spontaneous repair capacity of articular cartilage is limited; thus, investigation into new cartilage replacement and regeneration techniques are warranted. Along with the challenges of an increasingly aging demographic, changing clinical scenarios and rising functional expectations provide the imperative for new, more reliable skeletal regeneration strategies. The science of tissue engineering has expanded dramatically in recent years, notably in orthopedic applications, and it is clear that new approaches for de novo skeletal tissue formation offer exciting opportunities to improve the quality of life for many, particularly in the face of increasing patient expectations. However, significant scientific, financial, industrial, and regulatory challenges should be overcome before the successful development of an emergent tissue engineering strategy can be realized. We outline current practice for replacement of lost skeletal tissue and the innovative approaches in tissue regeneration that have so far been translated to clinical use, along with a discussion of the significant hurdles that are presented in the process of translating research strategies to the clinic.

Does bone morphogenetic protein increase the incidence of perioperative complications in spinal fusion? A comparison of 55,862 cases of spinal fusion with and without bone morphogenetic protein

STUDY DESIGN

Retrospective review of a multi-institutional, multisurgeon database.

OBJECTIVE

Assess for associations between bone morphogenetic protein (BMP) use and rate of complications in spinal fusion.

SUMMARY OF BACKGROUND DATA

BMP is commonly used in spinal surgery to augment fusion; however, there is limited evidence demonstrating its associated complications.

METHODS

We performed a retrospective analysis of all fusion cases submitted by members of the Scoliosis Research Society from 2004 to 2007. We stratified on the basis of the use of BMP and evaluated for complications and associated characteristics.

RESULTS

A total of 55,862 cases of spinal fusion were identified with BMP used in 21% (11,933) of the cases. Excluding anterior cervical fusions, there were no significant differences between fusions with and without BMP with regard to overall complications (8.4% vs. 8.5%; P = 0.5), wound infections (2.4% vs. 2.4%; P = 0.8), or epidural hematomas/seromas (0.2% vs. 0.2%; P = 0.3). Anterior cervical fusions with BMP were associated with more overall complications (5.8% vs. 2.4%; P < 0.001) and more wound infections (2.1% vs. 0.4%; P < 0.001) than fusions without BMP. On multivariate analysis for thoracolumbar and posterior cervical fusions, BMP use was not a significant predictor of complications (P = 0.334; odds ratio = 1.039; 95% confidence interval = 0.961-1.124; covariates were BMP use, patient age, revision vs. primary surgery). Multivariate analysis for anterior cervical spinal fusion demonstrated that BMP use remained a significant predictor of complications (P < 0.001, odds ratio = 1.6; 95% confidence interval = 1.516-1.721), after adjusting for the effects of patient age and whether the surgery was a revision procedure.

CONCLUSION

BMP use with anterior cervical fusion was associated with an increased incidence of complications. Use of BMP was not associated with more complications in thoracolumbar and posterior cervical fusions.

Spatiotemporal delivery of bone morphogenetic protein enhances functional repair of segmental bone defects

Osteogenic growth factors that promote endogenous repair mechanisms hold considerable potential for repairing challenging bone defects. The local delivery of one such growth factor, bone morphogenetic protein (BMP), has been successfully translated to clinical practice for spinal fusion and bone fractures. However, improvements are needed in the spatial and temporal control of BMP delivery to avoid the currently used supraphysiologic doses and the concomitant adverse effects. We have recently introduced a hybrid protein delivery system comprised of two parts: a perforated nanofibrous mesh that spatially confines the defect region and a functionalized alginate hydrogel that provides temporal growth factor release kinetics. Using this unique spatiotemporal delivery system, we previously demonstrated BMP-mediated functional restoration of challenging 8mm femoral defects in a rat model. In this study, we compared the efficacy of the hybrid system in repairing segmental bone defects to that of the current clinical standard, collagen sponge, at the same dose of recombinant human BMP-2. In addition, we investigated the specific role of the nanofibrous mesh tube on bone regeneration. Our results indicate that the hybrid delivery system significantly increased bone regeneration and improved biomechanical function compared to collagen sponge delivery. Furthermore, we observed that presence of the nanofiber mesh tube was essential to promote maximal mineralized matrix synthesis, prevent extra-anatomical mineralization, and guide an integrated pattern of bone formation. Together, these results suggest that spatiotemporal strategies for osteogenic protein delivery may enhance clinical outcomes by improving localized protein retention.

What bone graft substitutes should we use in post-traumatic spinal fusion?

Surgical treatment of spinal fractures consists of postural reduction and segmental arthrodesis, together with an eventual performance of spinal canal decompression. Spinal arthrodesis consists of the combination of a hardware system for mechanical stabilisation together with a biological substance for enhancement of bone formation. To date, autologous graft is the only biological substance demonstrated to possess osteogenic properties. Cancellous bone graft has greater cellular activity than cortical graft, whereas cortical graft is stronger. Consequently, according to biological and biomechanical properties of autograft, spinal posterior arthrodesis is better enhanced by cancellous autograft, whereas anterior interbody tricortical bone is more suitable for anterior fusion. Allograft does not cause harvesting complications as autograft does, and also its amount is theoretically unlimited; nevertheless the rate of bone fusion facilitated by allograft is far from that enhanced by autograft given that allograft has no osteoprogenitor cells. There is little evidence on the efficacy of demineralised bone matrix for spinal fusion. Bone morphogenetic proteins (BMPs) are in use in spinal surgery, but their exact role with respect to type, dose, and carrier, together with their cost-effectiveness, need further clinical delineation. Calcium phosphate compounds appear to be good as carriers; however, they have no osteoinductive or osteogenic properties. Current clinical literature seem to indicate their usefulness for bony fusion in spinal surgery, when combined with bone marrow aspirate or used as an extender for autologous bone graft. Age, length of fusion, location, and concurrent diseases should be definitive for fusion outcome; papers on spinal arthrodesis should neatly stratify these variables. Unfortunately, since that is not the rule, conclusions drawn from current literature are very unreliable. Autograft remains the gold standard, and cancellous bone is advisable in posterolateral approaches, whereas tricortical iliac crest autograft appears appropriate for interbody support. In longer segments, its expansion with BMPs looks safe at least. Basic knowledge has been achieved from animal experiments, and clinical application of the findings to humans should be done very cautiously; in any case, both anterior and posterior arthrodesis must be protected with instrumentation used according to appropriate biomechanical principles. A combination of failure of the correct graft together with proper instrumentation will result in poorer outcome, even if the right graft is used.

Safety and efficacy of rhBMP2 in posterior cervical spinal fusion for subaxial degenerative spine disease: Analysis of outcomes in 204 patients

Background:

Many studies offer excellent demonstration of the ability of bone morphogenic protein (BMP) to enhance fusion rates in anterior as well as posterior lumbar surgery. Recently, BMP has also been shown to increase arthrodesis rates in anterior cervical surgery, albeit with concomitant increases in complication rates. To date, however, few studies have investigated the safety and efficacy of BMP in cervical surgeries approached posteriorly.

Methods:

We retrospectively reviewed 204 consecutive patients with degenerative cervical spinal conditions necessitating posterior cervical fusion at a single institution over the past 4 years. The incidence of postoperative mechanical neck pain, fusion rates, as well as neurologic outcomes were compared between patients who received BMP vs those who did not receive BMP intraoperatively.

Results:

There were no significant differences in preoperative variables between the non-BMP vs the BMP cohorts. Over an average follow-up of 24.2 months, there were no significant differences between the two cohorts in duration of hospitalization, cerebrospinal fluid leakage, deep vein thrombosis, pulmonary embolism, hyperostosis, infection, pneumonia, hematoma, C5 palsy, wound dehiscence, reoperation rates, or Nurick/ASIA scores. Eleven (7.1%) patients in the non-BMP group experienced instrumentation failure vs none in the BMP group (P=0.06). Patients receiving BMP had a significantly increased rate of fusion by the chi-square test (P=0.01) and the log-rank test (P=0.02). However, patients receiving BMP also had the highest rates of recurrent/persistent neck pain by the chi-square test (P=0.003) and the log-rank test (P=0.01).

Conclusions:

To date, few studies have evaluated the safety and efficacy of BMP in the posterior cervical spine. Here, we show that BMP usage does not increase complication rates, but it significantly increases arthrodesis rates and also may increase the rate of recurrent/persistent neck pain.

Effects of protein dose and delivery system on BMP-mediated bone regeneration

Delivery of recombinant proteins is a proven therapeutic strategy to promote endogenous repair mechanisms and tissue regeneration. Bone morphogenetic protein-2 (rhBMP-2) has been used to promote spinal fusion and repair of challenging bone defects; however, the current clinically-used carrier, absorbable collagen sponge, requires high doses and has been associated with adverse complications. We evaluated the hypothesis that the relationship between protein dose and regenerative efficacy depends on delivery system. First, we determined the dose-response relationship for rhBMP-2 delivered to 8-mm rat bone defects in a hybrid nanofiber mesh/alginate delivery system at six doses ranging from 0 to 5 μg. Next, we directly compared the hybrid delivery system to the collagen sponge at 0.1 and 1.0 μg. Finally, we compared the in vivo protein release properties of the two delivery methods. In the hybrid delivery system, bone volume, connectivity and mechanical properties increased in a dose-dependent manner to rhBMP-2. Consistent bridging of the defect was observed for doses of 1.0 μg and greater. Compared to collagen sponge delivery at the same 1.0 μg dose, the hybrid system yielded greater connectivity by week 4 and 2.5-fold greater bone volume by week 12. These differences may be explained by the significantly greater protein retention in the hybrid system compared to collagen sponge. This study demonstrates a clear dose-dependent effect of rhBMP-2 delivered using a hybrid nanofiber mesh/alginate delivery system. Furthermore, the effective dose was found to vary with delivery system, demonstrating the importance of biomaterial carrier properties in the delivery of recombinant proteins.

Use of recombinant human bone morphogenetic protein-2 as an adjunct for instrumented posterior arthrodesis in the occipital cervical region: An analysis of safety, efficacy, and dosing

Background:

There have been few reports on the use of recombinant human bone morphogenetic protein (rhBMP)-2 in posterior spine. However, no study has investigated the dosing, safety, and efficacy of its use in the posterior atlantoaxial, and/or craniovertebral junction. Recent case report of the cytokine-mediated inflammatory reaction, following off label use of rhBMP-2 as an adjunct for cervical fusion, particularly in complex cases, has increased concern about complications associated with the product.

Objective:

To assess the safety, efficacy, and dosing of rhBMP-2 as an adjunct for instrumented posterior atlantoaxial and/or craniovertebral junction arthrodesis.

Materials and Methods:

We included all patients treated by the senior author that included posterior atlantoaxial and/or craniovertebral junction instrumented fusion using rhBMP-2 from 2003 to 2008 with a minimum two year follow-up. Diagnosis, levels fused, rhBMP-2 dose, complications, and fusion were assessed.

Results:

Twenty three patients with a mean age of 60.9 years (range 4 - 89 years) and an average follow-up of 45 months (range 27 to 84 months) met inclusion criteria. The indications for surgery included, atlantoaxial instability (n = 16), basilar invagination (n = 6), and kyphoscoliosis (n = 1). The specific pathologic diagnosis included type 2 dens fracture (n = 7), complex C1 and C2 ring fracture (n = 2), chordoma (n = 2), degenerative/osteoporosis (n = 3), rheumatoid disease (n = 8), and pseudogout (n = 1). The average rhBMP-2 dose was 2.38 mg/level, with a total of 76 levels treated (average 3.3 levels, SD= 1.4 levels). There were no complications. During the most recent follow-up, all patients had achieved fusion.

Conclusions:

In a series of patients with complex pathology and/or rheumatoid arthritis, 100% fusion rate was achieved with adjunct use of rhBMP-2, with a safe and effective average rhBMP-2 dose of 2.38 mg per level.

Novel oxysterols have pro-osteogenic and anti-adipogenic effects in vitro and induce spinal fusion in vivo

Stimulation of bone formation by osteoinductive materials is of great clinical importance in spinal fusion surgery, repair of bone fractures, and in the treatment of osteoporosis. We previously reported that specific naturally occurring oxysterols including 20(S)-hydroxycholesterol (20S) induce the osteogenic differentiation of pluripotent mesenchymal cells, while inhibiting their adipogenic differentiation. Here we report the characterization of two structural analogues of 20S, Oxy34 and Oxy49, which induce the osteogenic and inhibit the adipogenic differentiation of bone marrow stromal cells (MSC) through activation of Hedgehog (Hh) signaling. Treatment of M2-10B4 MSC with Oxy34 or Oxy49 induced the expression of osteogenic differentiation markers Runx2, Osterix (Osx), alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin (OCN), as well as ALP enzymatic activity and robust mineralization. Treatment with oxysterols together with PPARγ activator, troglitazone (Tro), inhibited mRNA expression for adipogenic genes PPARγ, LPL, and aP2, and inhibited the formation of adipocytes. Efficacy of Oxy34 and Oxy49 in stimulating bone formation in vivo was assessed using the posterolateral intertransverse process rat spinal fusion model. Rats receiving collagen implants with Oxy 34 or Oxy49 showed comparable osteogenic efficacy to BMP2/collagen implants as measured by radiography, MicroCT, and manual inspection. Histological analysis showed trabecular and cortical bone formation by oxysterols and rhBMP2 within the fusion mass, with robust adipogenesis in BMP2-induced bone and significantly less adipocytes in oxysterol-induced bone. These data suggest that Oxy34 and Oxy49 are effective novel osteoinductive molecules and may be suitable candidates for further development and use in orthopedic indications requiring local bone formation.

Cost-utility analysis of posterior minimally invasive fusion compared with conventional open fusion for lumbar spondylolisthesis

Background

The utility and cost of minimally invasive surgical (MIS) fusion remain controversial. The primary objective of this study was to compare the direct economic impact of 1- and 2-level fusion for grade I or II degenerative or isthmic spondylolisthesis via an MIS technique compared with conventional open posterior decompression and fusion.

Methods

A retrospective cohort study was performed by use of prospective data from 78 consecutive patients (37 with MIS technique by 1 surgeon and 41 with open technique by 3 surgeons). Independent review of demographic, intraoperative, and acute postoperative data was performed. Oswestry disability index (ODI) and Short Form 36 (SF-36) values were prospectively collected preoperatively and at 1 year postoperatively. Cost-utility analysis was performed by use of in-hospital micro-costing data (operating room, nursing, imaging, laboratories, pharmacy, and allied health cost) and change in health utility index (SF-6D) at 1 year.

Results

The groups were comparable in terms of age, sex, preoperative hemoglobin, comorbidities, and body mass index. Groups significantly differed (P < .01) regarding baseline ODI and SF-6D scores, as well as number of 2-level fusions (MIS, 12; open, 20) and number of interbody cages (MIS, 45; open, 14). Blood loss (200 mL vs 798 mL), transfusions (0% vs 17%), and length of stay (LOS) (6.1 days vs 8.4 days) were significantly (P < .01) lower in the MIS group. Complications were also fewer in the MIS group (4 vs 12, P < .02). The mean cost of an open fusion was 1.28 times greater than that of an MIS fusion (P = .001). Both groups had significant improvement in 1-year outcome. The changes in ODI and SF-6D scores were not statistically different between groups. Multivariate regression analysis showed that LOS and number of levels fused were independent predictors of cost. Age and MIS were the only predictors of LOS. Baseline outcomes and MIS were predictors of 1-year outcome.

Conclusion

MIS posterior fusion for spondylolisthesis does reduce blood loss, transfusion requirements, and LOS. Both techniques provided substantial clinical improvements at 1 year. The cost utility of the MIS technique was considered comparable to that of the open technique.

Level of Evidence

Level III.

A critical review of recombinant human bone morphogenetic protein-2 trials in spinal surgery: emerging safety concerns and lessons learned

BACKGROUND CONTEXT

Increasingly, reports of frequent and occasionally catastrophic complications associated with use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in spinal fusion surgeries are being published. In the original peer review, industry-sponsored publications describing the use of rhBMP-2 in spinal fusion, adverse events of these types and frequency were either not reported at all or not reported to be associated with rhBMP-2 use. Some authors and investigators have suggested that these discrepancies were related to inadequate peer review and editorial oversight.

PURPOSE

To compare the conclusions regarding the safety and related efficacy published in the original rhBMP-2 industry-sponsored trials with subsequently available Food and Drug Administration (FDA) data summaries, follow-up publications, and administrative and organizational databases.

STUDY DESIGN

Systematic review.

METHODS

Results and conclusions from original industry-sponsored rhBMP-2 publications regarding safety and related efficacy were compared with available FDA data summaries, follow-up publications, and administrative and organizational database analyses.

RESULTS

There were 13 original industry-sponsored rhBMP-2 publications regarding safety and efficacy, including reports and analyses of 780 patients receiving rhBMP-2 within prospective controlled study protocols. No rhBMP-2-associated adverse events (0%) were reported in any of these studies (99% confidence interval of adverse event rate <0.5%). The study designs of the industry-sponsored rhBMP-2 trials for use in posterolateral fusions and posterior lateral interbody fusion were found to have potential methodological bias against the control group. The reported morbidity of iliac crest donor site pain was also found to have serious potential design bias. Comparative review of FDA documents and subsequent publications revealed originally unpublished adverse events and internal inconsistencies. From this review, we suggest an estimate of adverse events associated with rhBMP-2 use in spine fusion ranging from 10% to 50% depending on approach. Anterior cervical fusion with rhBMP-2 has an estimated 40% greater risk of adverse events with rhBMP-2 in the early postoperative period, including life-threatening events. After anterior interbody lumbar fusion rates of implant displacement, subsidence, infection, urogenital events, and retrograde ejaculation were higher after using rhBMP-2 than controls. Posterior lumbar interbody fusion use was associated with radiculitis, ectopic bone formation, osteolysis, and poorer global outcomes. In posterolateral fusions, the risk of adverse effects associated with rhBMP-2 use was equivalent to or greater than that of iliac crest bone graft harvesting, and 15% to 20% of subjects reported early back pain and leg pain adverse events; higher doses of rhBMP-2 were also associated with a greater apparent risk of new malignancy.

CONCLUSIONS

Level I and Level II evidence from original FDA summaries, original published data, and subsequent studies suggest possible study design bias in the original trials, as well as a clear increased risk of complications and adverse events to patients receiving rhBMP-2 in spinal fusion. This risk of adverse events associated with rhBMP-2 is 10 to 50 times the original estimates reported in the industry-sponsored peer-reviewed publications.

Postoperative cervical myelopathy and cord compression associated with the use of recombinant bone morphogenetic protein-2 in posterior cervical decompression, instrumentation, and arthrodesis: a report of two cases

STUDY DESIGN

Case report.

OBJECTIVE

Two cases are presented in which the use of recombinant bone morphogenetic protein-2 (rh-BMP-2) in a posterior cervical decompression and instrumented arthrodesis may have contributed to seroma formation and cord compression.

SUMMARY OF BACKGROUND DATA

The use of rh-BMP-2 has been proven effective in promoting bone formation in anterior lumbar spine arthrodesis. Whether rh-BMP-2 is safe and/or effective in the cervical spine has not been determined. Adverse effects when it is used for anterior cervical fusion procedures have been reported but its role in posterior cervical decompression and instrumented fusions has yet to be determined.

METHODS

We report on two cases. The first is a 68-year-old man presenting with a substantial decline in his neurologic status approximately 2 weeks after surgery. The second is a 44-year-old man presenting with a substantial decline in his neurologic status approximately 5 days after surgery. Both complications occurred after a posterior cervical laminectomy and instrumented arthrodesis when rh-BMP-2 was used as a bone graft substitute.

RESULTS

Both patients were found to have a moderate-to-large seroma causing severe compression on the spinal cord and were urgently taken to an operating room for evacuation of the seromas. Both showed improvement of their neurologic status immediately after surgery. As rh-BMP-2 is known to occasionally cause seroma formation it is postulated that it may have been the cause of the seromas.

CONCLUSION

Caution should be exercised with rh-BMP-2 use in posterior cervical applications when a laminectomy has been performed. The safe and effective dose and technique for application have yet to be determined. Seroma formation is possible, which can cause acute stenosis with cord compression and neurologic compromise.

Complications associated with recombinant human bone morphogenetic protein use in pediatric craniocervical arthrodesis

OBJECT

Management of pediatric occipitocervical instability remains especially challenging. The off-label use of recombinant human bone morphogenetic protein (rhBMP)-2 for spinal fusion has increased with a well-documented increase in fusion rate in many case series. Unfortunately, recent reports have documented complications associated with rhBMP use in adult spinal fusions. Complications associated with the use of rhBMP in pediatric spinal surgery is less well understood. In this study the authors report on the fusion rate and complications associated with rhBMP in pediatric occipitocervical arthrodesis.

METHODS

The authors reviewed the medical records of those patients 18 years old and younger who underwent dorsal occipitocervical fusion from January 2004 to December 2007 at the University of Iowa Hospitals and Clinics. Forty-eight patients were identified who received rhBMP-augmented fusion. The clinical outcome and complications of these fusions were analyzed.

RESULTS

All 48 patients had fusion confirmed on lateral radiographs within 4-14 months with an average fusion time of 6.7 months. There were 6 complications, 5 of which included seroma formation. Two of 5 patients who developed postoperative seroma presented with symptoms suggesting brainstem compression and obstructive hydrocephalus requiring emergency reoperation. One patient developed heterotopic bone formation causing cervicomedullary compression requiring reoperation.

CONCLUSIONS

The use of rhBMP to augment autograft in occipitocervical fusion allows for a high rate of successful arthrodesis, but is associated with potentially life-threatening complications in pediatric patients.

Outcomes after spine surgery among racial/ethnic minorities: a meta-analysis of the literature

BACKGROUND CONTEXT

Prior research has identified disparities in access to care, resource utilization, and outcomes in members of racial and ethnic minorities. However, the role that race/ethnicity may play in influencing outcomes after spine surgery has not been previously studied.

PURPOSE

To characterize the effect of race and ethnicity on outcome after spine surgery.

STUDY DESIGN

Systematic literature review and meta-analysis.

PATIENT SAMPLE

Of 11 investigations selected in the initial analysis, four reported results in a fashion that enabled their inclusion in the meta-analysis. These four studies included a total of 128,635 patients.

OUTCOME MEASURES

"Favorable" or "unfavorable" postsurgical outcomes were determined based on parameters described in each included investigation.

METHODS

A systematic literature review was performed to identify all studies documenting outcomes, complications, or mortality after spine surgical procedures. Eligible studies had to include raw data that enabled separate analysis of white and nonwhite patients. Outcome was categorized as "favorable" or "unfavorable" based on scales included in each investigation. The Q-statistic was used to determine heterogeneity, and a meta-analysis was performed to assess the relative risk for unfavorable outcome among nonwhite patients after spine surgery.

RESULTS

Eleven studies met initial selection criteria but only four were eligible for inclusion in the meta-analysis. The meta-analysis included 128,635 patients among whom 12,194 (9.5%) had unfavorable outcomes. Among white patients, 9.4% sustained an unfavorable outcome as compared with 10.4% of nonwhites.

CONCLUSIONS

In light of the small number of studies able to be included in the meta-analysis, no firm conclusions can be drawn regarding the effect of race/ethnicity on outcome after spinal surgery. There is a pressing need for more robust research regarding spine surgical outcomes among different racial and ethnic minority groups.

Bone grafting, orthopaedic biomaterials, and the clinical need for bone engineering

As the population ages, the number of operations performed on bone is expected to increase. Diseases such as arthritis, tumours, and trauma can lead to defects in the skeleton requiring an operation to replace or restore the lost bone. Surgeons can use autografts, allografts, and/or bone graft substitutes to restore areas of bone loss. Surgical implants are also used in addition or in isolation to replace the diseased bone. This review considers the application of available bone grafts in different clinical settings. It also discusses recently introduced bioactive biomaterials and highlights the clinical difficulties and technological deficiencies that exist in our current surgical practice.

Return to golf after spine surgery

Object

No published evidence indicates when patients can resume golfing after spine surgery. The objective of this study is to provide data from surveys sent to spine surgeons.

Methods

A survey of North American Spine Society members was undertaken querying the suggested timing of return to golf. Of 1000 spine surgeons surveyed, 523 responded (52.3%). The timing of recommended return to golf and the reasons were questioned for college/professional athletes and avid and recreational golfers of both sexes. Responses were tallied for lumbar laminectomy, lumbar microdiscectomy, lumbar fusion, and anterior cervical discectomy with fusion.

Results

The most common recommended time for return to golf was 4–8 weeks after lumbar laminectomy and lumbar microdiscectomy, 2–3 months after anterior cervical fusion, and 6 months after lumbar fusion. The results showed a statistically significant increase in the recommended time to resume golf after lumbar fusion than after cervical fusion in all patients (p < 0.01). The same holds true for the return to play after cervical fusion compared with either lumbar laminectomy or lumbar microdiscectomy for all golfer types (p < 0.01). There was a statistically significant shorter recommended time for professional and college golfers compared with noncompetitive golfers after lumbar fusion (p < 0.01), anterior cervical discectomy and fusion (p < 0.01), and lumbar microdiscectomy (p < 0.01).

Conclusions

The return to golf after spine surgery depends on many variables, including the general well-being of patients in terms of pain control and comfort when golfing. This survey serves as a guide that can assist medical practitioners in telling patients the average times recommended by surgeons across North America regarding return to golf after spine surgery.

Recombinant human bone morphogenetic protein-2 as an adjunct for spine fusion in a pediatric population

BACKGROUND/AIMS

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is responsible for multiple different signaling processes including positive effects on bone formation and fusion. In 2002, rhBMP-2 was approved for use in anterior lumbar spinal fusion by the Food and Drug Administration. Since that time, rhBMP-2 use for spinal fusion has become widespread. The use of rh-BMP2 for pediatric spinal fusion, however, has not been widely reported. We report the experience of the use of rhBMP-2 for pediatric spinal fusion at the University of Florida.

METHODS

Data on patients under the age of 18 years who underwent spinal fusion with rhBMP-2 as an adjunct were retrospectively collected. Of these, 17 met the inclusion criteria and were reviewed. Two patients did not have adequate postoperative imaging. Fifteen patients were included in the final review.

RESULTS

All 15 patients showed osseous fusion. Complications included one CSF leak and one wound infection, one misplaced screw requiring revision, and one case of adjacent segment kyphosis requiring extension of the original construct.

CONCLUSION

rhBMP-2 is a successful adjunct for fusion in pediatric patients. Many of these patients had congenital defects that historically decrease fusion rates. rhBMP-2 appears safe and has an associated high rate of osseous fusion.

Artrodese na coluna cervical utilizando SICAP como substituto de enxerto ósseo

OBJETIVO: Substitutos de enxerto ósseo autólogo foram desenvolvidos para evitar as complicações da retirada de enxerto ósseo autólogo. SiCaP (Actifuse, ApaTech EUA, Reino Unido) é um enxerto ósseo composto de cálcio-fosfato com um substituição de silicato na estrutura química, com uma estrutura tridimensional que parece osso natural. MÉTODOS: 19 pacientes foram submetidos à fusão óssea cervical e analisados retrospectivamente. A avaliação radiográfica e avaliação clínica foram realizadas utilizando o questionário Neck Disability Index e a escala análoga da dor (VAS) pré- e pós-operação. RESULTADOS: O período médio de acompanhamento pós-operatório foi de 14 meses ± 5 meses (7-30 meses). 11 pacientes foram submetidos à fusão via anterior; 5 pacientes via posterior e 3 pacientes via anterior e posterior. A revisão radiográfica mostrou 19/19 (100%) de fusão óssea, nenhum caso apresentou subsidência, quebra ou soltura de material de implante ou movimento nos níveis fusionados. Nenhum exemplo de ossificação heterotópica ou de crescimento ósseo intracanal foi observado. Clinicamente, os escores médios do Neck Disability decresceram 13,3 pontos (media pré-op. de 34,5, pós-op. de 21,2, melhora de 39%), a média da VAS para dor cervical decresceu 2 pontos (2,7 pré-op para 0,7 pós-op.; melhora de 74,1%). Não foram observadas complicações como infecção, osteólise ou edema excessivo das partes moles. CONCLUSÃO: Os resultados preliminares obtidos nesta série foram encorajadores com o uso do SICaP como enxerto ósseo, com sólida fusão óssea obtida em todos os casos e sem formação de ossificação heterotópica ou crescimento de osso intracanal. SIcaP demonstra ser um substituto confiável para o enxerto ósseo autólogo na coluna cervical.