Complications and concerns with osteobiologics for spine fusion in clinical practice

Global Practices and Preferences in the Use of Osteobiologics for Anterior Cervical Discectomy and Fusion: A Cross-Sectional Study

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To assess global practices and preferences in the use of osteobiologics for anterior cervical discectomy and fusion (ACDF) and identify factors influencing the choice of specific osteobiologics.

METHODS

An online survey developed by AO Spine was distributed to spine surgeons worldwide. The survey captured demographic characteristics, osteobiologic use and related information (i.e., previous training, practice patterns, etc.), and factors influencing osteobiologic choice in ACDF. Descriptive statistics, Chi-square tests, and multiple logistic regression were used to analyze responses, focusing on the associations between osteobiologic use and variables such as training, cost awareness, and regional practices.

RESULTS

Responses from 458 surgeons revealed regional variability in osteobiologic preferences. Autologous iliac crest bone graft (AICBG) was predominant in Asia Pacific and Middle East, while allograft and demineralized bone matrix were favored in North America and Latin America (P < 0.0001). Over half of the respondents (79.7%) lacked formal training in osteobiologics, and 53.1% were unaware of related costs. Surgeons residing in the Asia Pacific region (OR: 0.47, 95% CI: 0.26-0.84, P = 0.0114), without formal training (OR: 0.53, 95% CI: 0.29-0.97, P = 0.0429), or using cages less often (OR: 0.15, 95% CI: 0.06-0.34, P < 0.0001) were less likely to utilize osteobiologics. Osteobiologic use was also more common when related costs were not an issue for the practitioner (OR: 2.32, 95% CI:1.47-3.70, P = 0.0004).

CONCLUSIONS

Significant variation exists in osteobiologic use in ACDF across global regions, influenced by surgeon training, cost awareness, and institutional resources. Enhanced training and guidelines could improve consistency in osteobiologic application.

IL-1β contributes to the secretion of sclerostin by osteocytes and targeting sclerostin promotes spinal fusion at early stages

BACKGROUND

Despite extensive research, there is still a need for safe and effective agents to promote spinal fusion. Interleukin (IL)-1β is an important factor which influences the bone repair and remodelling. The purpose of our study was to determine the effect of IL-1β on sclerostin in osteocytes and to explore whether inhibiting the secretion of sclerostin from osteocytes can promote spinal fusion at early stages.

METHODS

Small-interfering RNA was used to suppress the secretion of sclerostin in Ocy454 cells. MC3T3-E1 cells were cocultured with Ocy454 cells. Osteogenic differentiation and mineralisation of MC3T3-E1 cells were evaluated in vitro. SOST knock-out rat generated using the CRISPR-Cas9 system and rat spinal fusion model was used in vivo. The degree of spinal fusion was assessed by manual palpation, radiographic analysis and histological analysis at 2 and 4 weeks.

RESULTS

We found that IL-1β level had a positive association with sclerostin level in vivo. IL-1β promoted the expression and secretion of sclerostin in Ocy454 cells in vitro. Inhibition of IL-1β-induced secretion of sclerostin from Ocy454 cells could promote the osteogenic differentiation and mineralisation of cocultured MC3T3-E1 cells in vitro. The extent of spinal graft fusion was greater in SOST-knockout rats than in wild-type rats at 2 and 4 weeks.

CONCLUSIONS

The results demonstrate that IL-1β contributes to a rise in the level of sclerostin at early stages of bone healing. Suppressing sclerostin may be an important therapeutic target capable of promoting spinal fusion at early stages.

Use of Autologous Stem Cells in Lumbar Spinal Fusion: A Systematic Review of Current Clinical Evidence

STUDY DESIGN

Systematic review.

OBJECTIVES

To systematically review, critically appraise and synthesize evidence on use of autologous stem cells sources for fusion in the lumbar spine.

METHODS

A systematic search of PubMed/MEDLINE, EMBASE and ClinicalTrials.gov through February 20, 2020 was conducted comparing autologous cell grafts to other biologics for lumbar spine fusion. The focus was on studies comparing distinct patient groups.

RESULTS

From 343 potentially relevant citations, 15 studies met the inclusion criteria set a priori. Seven studies compared distinct patient groups, with BMA being used in combination with allograft or autograft not as a standalone material. No economic evaluations were identified. Most observational studies were at moderately high risk of bias. When used for primary lumbar fusion, no statistical differences in outcomes or complications were seen between BMA+autograft/or +allograft compared to autograft/allograft alone. Compared with allograft, data from a RCT suggested statistically better fusion and lower complication rates with concentrated BMA+allograft. When used in revisions, no differences in outcomes were seen between BMA+allograft and either autograft or rh-BMP-2 but fusion rates were lower with BMA+allograft, leading to additional revision surgery.

CONCLUSIONS

There was substantial heterogeneity across studies in patient populations, sample size, biologic combinations, and surgical characteristics making direct comparisons difficult. The overall quality of evidence for fusion rates and the safety of BMA in lumbar fusion procedures was considered very low, with studies being at moderately high or high risk of bias.

The Impact of Osteobiologic Subtype Selection on Perioperative Complications and Hospital-Reported Charges in Single- and Multi-Level Lumbar Spinal Fusion

BACKGROUND

Over the last several decades, various osteobiologics including allograft, synthetics, and growth factors have been used for lumbar spinal fusion surgery. However, the data on these osteobiologic products remain controversial with conflicting evidence in the literature. This study evaluates the influence of osteobiologic type selection on perioperative complications and hospital-reported charges in single-level and multilevel lumbar fusion.

METHODS

Using the 2016 and 2017 Nationwide Readmission Database, we conducted a retrospective cohort analysis of 125,143 patients who received lumbar fusion with either autologous tissue substitute, nonautologous tissue substitute, or synthetic substitute. This cohort was split into single-level and multilevel fusion procedures, and one-to-one age and sex propensity score matching was implemented. This resulted in cohorts each consisting of 1967 patients for single-level fusion, and cohorts each consisting of 1657 patients for multilevel fusion. Statistical analysis included one-way analysis of variance and Tukey multiple comparisons of means.

RESULTS

Autologous single-level fusion resulted in significantly more postoperative pain at 30-, 90-, and 180-day follow-up compared to fusion with nonautologous graft (P < .05). Multilevel fusion with autologous graft had higher rates of acute postsurgical anemia compared with synthetic (P = .021) and nonautologous (P = .016) alternatives, and less postsurgical infection when compared with nonautologous fusion (P = .0020). In addition, procedures using autologous osteobiologics were associated with significantly more neurological complications at 30 days (P = .049) and 90 days (P = .048) for multi-level fusion and at 30 days (P = .044) for single-level fusion compared with the nonautologous group. Lastly, for both cohorts, the total accrued inpatient hospital charges during admission for patients receiving nonautologous grafts were the most expensive and those for patients receiving autologous grafts were the least expensive.

CONCLUSION

Significant differences were found between the groups with respect to rates of complications, including infection, postoperative pain, and neurologic injury. Furthermore, the hospital-reported charges of each procedure varied significantly. As the field of biologics continues to expand, it is important to continually evaluate the safety, efficacy, and cost-effectiveness of these novel materials and techniques.

LEVEL OF EVIDENCE

3 CLINICAL RELEVANCE: With increased utilization of osteobiologics and spinal fusion being a common procedure, longitudinal data on readmissions, and post-operative complications are critical in guiding evidence-based practice.

Autologous blood coagulum containing rhBMP6 induces new bone formation to promote anterior lumbar interbody fusion (ALIF) and posterolateral lumbar fusion (PLF) of spine in sheep

In the present study, we evaluated an autologous bone graft substitute (ABGS) composed of recombinant human BMP6 (rhBMP6) dispersed within autologous blood coagulum (ABC) used as a physiological carrier for new bone formation in spine fusion sheep models. The application of ABGS included cervical cage for use in the anterior lumbar interbody fusion (ALIF), while for the posterolateral lumbar fusion (PLF) sheep model allograft devitalized bone particles (ALLO) were applied with and without use of instrumentation. In the ALIF model, ABGS (rhBMP6/ABC/cage) implants fused significantly when placed in between the L4-L5 vertebrae as compared to control (ABC/cage) which appears to have a fibrocartilaginous gap, as examined by histology and micro CT analysis at 16 weeks following surgery. In the PLF model, ABGS implants with or without ALLO showed a complete fusion when placed ectopically in the gutter bilaterally between two decorticated L4-L5 transverse processes at a success rate of 88% without instrumentation and at 80% with instrumentation; however the bone volume was 50% lower in the instrumentation group than without, as examined by histology, radiographs, micro CT analyses and biomechanical testing at 27 weeks following surgery. The newly formed bone was uniform within ABGS implants resulting in a biomechanically competent and histologically qualified fusion with an optimum dose in the range of 100 μg rhBMP6 per mL ABC, while in the implants that contained ALLO, the mineralized bone particles were substituted by the newly formed remodeling bone via creeping substitution. These findings demonstrate for the first time that ABGS (rhBMP6/ABC) without and with ALLO particles induced a robust bone formation with a successful fusion in sheep models of ALIF and PLF, and that autologous blood coagulum (ABC) can serve as a preferred physiological native carrier to induce new bone at low doses of rhBMP6 and to achieve a successful spinal fusion.

Fusion Rates of Lateral Lumbar Interbody Fusion Using Recombinant Human Bone Morphogenetic Protein-2

STUDY DESIGN

Retrospective observational case series.

OBJECTIVES

Lateral lumbar interbody fusion (LLIF) has been widely performed with recombinant human bone morphogenetic protein-2 (rhBMP-2), but the fusion rates using this graft alternative have not been well studied. We aimed to evaluate fusion rates in 1- and 2-level LLIF with rhBMP-2 and their relationship with fixation, as well as rates of BMP-related complications.

METHODS

Institutional review board (IRB)-approved spine registry cohort of 93 patients who underwent LLIF with rhBMP-2 (71 one-level cases and 22 two-level cases). Minimum 1-year clinical follow-up and computed tomography (CT) scan for fusion assessment. Postoperative CT scans were used to evaluate the rate of fusion in all patients. Instrumentation and complications were collected from chart and imaging review.

RESULTS

Average age was 65 years (67% female). For 1-level cases, 92% (65/71) had complete fusion and 8% (6/71) had either incomplete or indeterminate fusion. Three of the 6 patients who had incomplete or indeterminate fusion had bilateral pedicle screw instrumentation, 1 patient had unilateral posterior fixation, and 2 had no fixation. In 2-level cases, 86% (19/22) had complete fusion and 14% (3/22) had either incomplete or indeterminate fusion. The 3 patients who had incomplete or indeterminate fusion did not have fixation.

CONCLUSION

Interbody fusion rates with rhBMP-2 via LLIF was 92% in 1-level cases and 86% in 2-level cases, indicating that rhBMP-2 may be used as a viable graft alternative to allograft options for LLIF. Higher rates of pseudarthrosis occurred when not using fixation.

A Prospective, Randomized, Multicenter Study Comparing Silicated Calcium Phosphate versus BMP-2 Synthetic Bone Graft in Posterolateral Instrumented Lumbar Fusion for Degenerative Spinal Disorders

STUDY DESIGN

A prospective, Phase IV, multicenter, randomized study.

OBJECTIVE

The aim of this study was to compare vertebral fusion success rates following posterolateral fusion [(PLF)/posterolateral intertransverse fusion (PITF)] surgery. The surgical procedure combined posterior lumbar interbody fusion (PLIF) and PLF with internal fixation over one or two levels using silicated calcium phosphate (SiCaP) or bone morphogenetic protein (BMP)-2 as graft material in patients with a degenerative disorder of the lumbar spine.

SUMMARY OF BACKGROUND DATA

Few controlled trials have evaluated the bone graft materials available to surgeons treating patients with spinal disorders, including degenerative disc disease, spondylolisthesis, and disc herniation.

METHODS

Following randomization, the surgical procedure consisting of PLIF and PLF with internal fixation over one or two levels was performed using SiCaP or BMP-2. No other osteoconductive/osteoinductive graft materials were permitted. Spinal fusion was assessed radiographically at ≤24 months. Clinical outcomes (pain on visual analog scale, Oswestry Disability Index, SF-36) and adverse events (AEs) were monitored.

RESULTS

One hundred three patients were enrolled. At 12 months, fusion was achieved in 25 of 35 (71.4%) of the SiCaP and 20 of 27 (74.1%) of the BMP-2 group, respectively (P = 1.000). At 24 months, the fusion rate was 78.6% and 84.8% for SiCaP and BMP-2, respectively (P = 0.5613). Clinical outcomes improved similarly in both groups over time. AEs were consistent with this surgical population.

CONCLUSION

SiCaP was safe and well tolerated in patients with degenerative spinal disorders requiring PLF and provided fusion rates similar to BMP-2.

LEVEL OF EVIDENCE

2.

Allograft Versus Demineralized Bone Matrix in Instrumented and Noninstrumented Lumbar Fusion: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The aim was to determine the fusion efficacy of allograft and demineralized bone matrix (DBM) in lumbar instrumented and noninstrumented fusion procedures for degenerative lumbar disorders.

METHODS

A literature search was conducted using the PubMed and Cochrane databases. To be considered, publications had to meet 4 criteria: patients were treated for a degenerative lumbar disorder, a minimum group size of 10 patients, use of allograft or DBM, and at least a 2-year follow-up. Data on the study population, follow-up time, surgery type, grafting material, fusion rates, and its definition were collected.

RESULTS

The search yielded 692 citations with 17 studies meeting the criteria including 4 retrospective and 13 prospective studies. Six studies used DBM and 11 employed allograft alone or in the combination with autograft. For the allograft, fusion rates ranged from 58% to 68% for noninstrumented and from 68% to 98% for instrumented procedures. For DBM, fusion rates were 83% for noninstrumented and between 60% and 100% for instrumented lumbar fusion procedures.

CONCLUSIONS

Both allograft and DBM appeared to provide similar fusion rates in instrumented fusions. On the other hand, in noninstrumented procedures DBM was superior. However, a large variation in the type of surgery, outcomes collection, lack of control groups, and follow-up time prevented any significant conclusions. Thus, studies comparing the performance of allograft and DBM to adequate controls in large, well-defined patient populations and with a sufficient follow-up time are needed to establish the efficacy of these materials as adjuncts to fusion.

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.

Prospective analysis of a new bone graft in lumbar interbody fusion: results of a 2- year prospective clinical and radiological study

Background

This study examined the efficacy and safety of bone graft material ABM/P-15 (iFACTOR) for use in posterior lumbar interbody fusion. ABM/P-15 has been used safely for more than a decade in dental applications.

Methods

Forty patients underwent PLIF surgery, with each patient as control. Assessments up to 24 months included radiographs, CT scan, VAS, and ODI. Primary success criteria were fusion and safety.

Results

Intra-cage bridging bone occurred earlier with ABM/P-15 than autograft (97.73% vs. 59.09% at 6 months). On average pain decreased 29 points and function improved 43 points. Radio dense material outside the disk space occurred more frequently with ABM/P-15 than autograft, without clinical consequence.

Conclusions

This study suggests that ABM/P-15 has equal or greater efficacy at 6 and 12 months. Pain improvements exceeded success criteria at all time points. Functional improvement exceeded success criteria at all time points.

Clinical Relevance

This study explores the safety and efficacy of an osteobiologic peptide enhanced bone graft material as a viable alternative to autograft and its attendant risks.

Rare complications of osteolysis and periprosthetic tissue reactions after hybrid and non-hybrid total disc replacement

PURPOSE

Few complications have been reported for lumbar total disc replacement (TDR) and hybrid TDR fixations. This study evaluated retrieved implants and periprosthetic tissue reactions for two cases of osteolysis following disc arthroplasty with ProDisc-L prostheses.

METHODS

Implants were examined for wear and surface damage, and tissues for inflammation, polyethylene wear debris (polarized light microscopy) and metal debris (energy-dispersive X-ray spectroscopy).

RESULTS

Despite initial good surgical outcomes, osteolytic cysts were noted in both patients at vertebrae adjacent to the implants. For the hybrid TDR case, heterotopic ossification and tissue necrosis due to wear-induced inflammation were observed. In contrast, the non-hybrid implant showed signs of abrasion and impingement, and inflammation was observed in tissue regions with metal and polyethylene wear debris.

CONCLUSIONS

In both cases, wear debris and inflammation may have contributed to osteolysis. Surgeons using ProDisc prostheses should be aware of these rare complications.

National trends in revision spinal fusion in the USA

Using the United States Nationwide Inpatient Sample, we identified national trends in revision spinal fusion along with a comprehensive comparison of comorbidities, inpatient complications and surgical factors of revision spinal fusion compared to primary spinal fusion.

In 2009, there were 410 158 primary spinal fusion discharges and 22 128 revision spinal fusion discharges. Between 2002 and 2009, primary fusion increased at a higher rate compared with revision fusion (56.4% vs 51.0%; p < 0.001). In 2009, the mean length of stay and hospital charges were higher for revision fusion discharges than for primary fusion discharges (4.2 days vs 3.8 days, p < 0.001; USD $91 909 vs. $87 161, p < 0.001). In 2009, recombinant human bone morphogenetic protein (BMP) was used more in revision fusion than in primary fusion (39.6% vs 27.6%, p < 0.001), whereas interbody devices were used less in revision fusion (41.8% vs 56.6%, p < 0.001).

In the multivariable logistic regression model for all spinal fusions, depression (odds ratio (OR) 1.53, p < 0.001), psychotic disorders (OR 1.49, p < 0.001), deficiency anaemias (OR 1.35, p < 0.001) and smoking (OR 1.10, p = 0.006) had a greater chance of occurrence in revision spinal fusion discharges than in primary fusion discharges, adjusting for other variables. In terms of complications, after adjusting for all significant comorbidities, this study found that dural tears (OR 1.41; p < 0.001) and surgical site infections (OR 3.40; p < 0.001) had a greater chance of occurrence in revision spinal fusion discharges than in primary fusion discharges (p < 0.001). A p-value < 0.01 was considered significant in all final analyses.

Cite this article: Bone Joint J 2014;96-B:807–16.

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

BACKGROUND CONTEXT

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

PURPOSE

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

STUDY DESIGN

Case report and literature review.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Transforaminal lumbar interbody fusion rates in patients using a novel titanium implant and demineralized cancellous allograft bone sponge

BACKGROUND

Transforaminal lumbar interbody fusion (TLIF) with grafting and implant options like iliac crest bone graft (ICBG), recombinant bone morphogenetic protein (rhBMP), and polyetheretherketone (PEEK) cages have been reported to achieve extremely high fusion rates. Unfortunately, these options have also been frequently cited in the literature as causing postoperative morbidity and complications at a high cost. Knowing this, we sought to investigate TLIF using an acid-etched, roughened titanium cage that upregulates osteogenesis to see if similar fusion rates to those cited for ICBG, rhBMP, and PEEK cages could be safely achieved with minimal morbidity and complications.

MATERIALS AND METHODS

A radiographic fusion study of 82 patients who underwent TLIF using an acid-etched, roughened titanium cage with demineralized cancellous bone graft was conducted. Fusion was assessed and graded by an independent radiologist using computed tomography scan with sagittal and coronal reconstructions.

RESULTS

Fusion rates at 6 months were 41 of 44 (93.2%) and at 12 months were 37 of 38 (97.4%). There were no radiographic device-related complications.

CONCLUSIONS

TLIF with an acid-etched, roughened titanium cage filled with a decalcified bone graft achieved similar fusion rates to historical controls using ICBG, rhBMP, and PEEK.

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.

A systematic review of comparative studies on bone graft alternatives for common spine fusion procedures

BACKGROUND

The increased prevalence of spinal fusion surgery has created an industry focus on bone graft alternatives. While autologous bone graft remains the gold standard, the complications and morbidity from harvesting autologous bone drives the search for reliable and safe bone graft substitutes. With the recent information about the adverse events related to bone morhogenetic protein use, it is appropriate to review the literature about the numerous products that are not solely bone morphogenetic protein.

PURPOSE

The purpose of this literature review is to determine the recommendations for use of non-bone morphogenetic protein bone graft alternatives in the most common spine procedures based on a quantifiable grading system.

STUDY DESIGN

Systematic literature review.

METHODS

A literature search of MEDLINE (1946-2012), CINAHL (1937-2012), and the Cochrane Central Register of Controlled Trials (1940-April 2012) was performed, and this was supplemented by a hand search. The studies were then evaluated based on the Guyatt criteria for quality of the research to determine the strength of the recommendation.

RESULTS

In this review, more than one hundred various studies on the ability of bone graft substitutes to create solid fusions and good patient outcomes are detailed.

CONCLUSION

The recommendations for use of bone graft substitutes and bone graft extenders are based on the strength of the studies and given a grade.

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

BACKGROUND CONTEXT

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

PURPOSE

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

STUDY DESIGN

Case report and literature review.

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Adjuncts in posterior lumbar spine fusion: comparison of complications and efficacy

PURPOSE

The purpose of this study was to define the efficacy of recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) and Demineralized Bone Matrix (DBM) compared to autograft in posterior lumbar spine fusion by comparing complication rates.

METHODS

During a 7-year period (2003-2009), all patients undergoing posterior lumbar fusion were retrospectively evaluated within a large orthopedic surgery private practice. Patient demographics, comorbidities, number of levels, type of surgery, and types of bone void filler and osteobiologics were analyzed. Complications were defined as reoperation secondary to failed symptomatic fusion, hyper-reaction with fluid collections, bone overgrowth, and infections.

RESULTS

1,398 patients were evaluated with 41.1 % males and 58.9 % females. Mean age was 60 years and BMI 30.6 kg/m². Patients were subdivided in treatment groups: rhBMP-2, 947 (67.7 %), DBM 306 (21.9 %), and autograft 145 (10.4 %). The overall infection rate was 2.1 %. No significant differences were found between the three groups. The incidence of seroma formation was higher in the BMP group (3.2 %) than in the DBM or autograft group (2.0 and 1.4 %, respectively) but this was not significant (p = 0.286 and p = 0.245, respectively). 103 patients (7.4 %) underwent redo surgery for clinically significant nonunion. We found significantly fewer nonunions (4.3 %) in the rhBMP-2 group (p < 0.001) compared to the DBM or autograft group (13.1 and 15.2 %, respectively).

CONCLUSION

ICBG is the gold standard. DBM leads to comparable fusion rates and does not increase infection or seroma formation. rhBMP-2 supplementation instead of ICBG or bone marrow aspirate results in higher fusion rates compared to autograft alone or autograft plus DBM.

Osteoconductive bone graft extenders in posterolateral thoracolumbar spinal fusion: a systematic review

STUDY DESIGN

A systematic review.

OBJECTIVE

To evaluate the efficacy, safety, and outcomes of osteoconductive bone graft extenders (BGEs) compared with iliac crest bone graft (ICBG) in posterolateral thoracolumbar spinal fusion.

SUMMARY OF BACKGROUND DATA

ICBG is the current "gold standard" for achieving spinal arthrodesis. However, morbidity associated with its harvesting has led to the increased use of BGEs.

METHODS

An electronic literature search was conducted through April 2011 using MEDLINE, EMBASE, CENTRAL, and Cochrane Library. Risk of bias and methodological assessment was performed using the Cochrane Risk of Bias Tool. Higgins I(2) test was used to assess for heterogeneity. Pooled weighted relative risk (RR) ratios were calculated to compare fusion and adverse event rates. Weighted standardized mean differences were calculated to compare functional outcome and pain scores.

RESULTS

Thirteen studies were included representing a total of 768 patients. Overall study quality was low (mean Cochrane Risk of Bias score, 4.8 out of 12; range, 3-6). Fusion rates were comparable between the BGE and ICBG groups (RR, 0.96; 95% confidence interval [CI], 0.89-1.03; P = 0.28). Higgins I(2) test (58%) suggested substantial heterogeneity in the pooling of studies. The pooled rate of donor site pain in the ICBG group was 11.2% (95% CI, 7.4%-15.1%). Reported adverse events, excluding donor site pain, were significantly lower in the BGE group (RR, 0.42; 95% CI, 0.28-0.64; P < 0.0001). Functional outcomes were not significantly different between the 2 groups.

CONCLUSION

Osteoconductive BGEs combined with local spine autograft and/or bone marrow aspirate have comparable fusion rates, similar functional outcomes, lower complication rates, and a lower risk of donor site pain than ICBG. Caution should be taken in interpreting these findings, given the low quality of the studies and the heterogeneity in the results. Randomized controlled studies using blinded assessments are required to help elucidate more conclusive evidence.

Effects of a perfusion bioreactor activated novel bone substitute in spine fusion in sheep

PURPOSE

To evaluate the effect of a large perfusion-bioreactor cell-activated bone substitute, on a two-level large posterolateral spine fusion sheep model.

METHODS

A 50 mm long porous biphasic-calcium-phosphate bone substitute reinforced with poly(D,L-lactide) and, activated with bone marrow derived mononuclear-cells (BMNC) was used. Eighteen sheep were divided into two groups and one group (n = 9) had BMNC-activated bone substitutes and cell-free substitutes implanted. The second group (n = 9) had autograft supplemented with BMNC and regular autograft implanted. The implant material was alternated between spine level L2-L3 and L4-L5 in both groups. MicroCT was used to compare the spine fusion efficacy and bone structure of the two groups as well as the implanted bone substitutes and non-implanted substitutes.

RESULTS

After 4½ months six sheep survived in both groups and we found five spine levels were fused when using activated bone substitute compared to three levels with cell-free bone substitute (p = 0.25). Five sheep fused at both levels in the autograft group. A significant increased bone density (p < 0.05) and anisotropy (p < 0.05) was found in the group of activated bone substitutes compared to cell-free bone substitute and no difference existed on the other parameters. The implanted bone substitutes had a significant higher bone density and trabecular thickness than non-implanted bone substitutes, thus indicating that the PLA reinforced BCP had osteoconductive properties (p < 0.05). No effect of the supplemented BMNC to autograft was observed. The autograft group had a significant higher bone density, trabecular thickness and degree of anisotropy than the implanted bone substitutes (p < 0.05), but a lower connectivity density existed (p < 0.05). This indicates that though the activated substitute might have a similar fusion efficacy to autograft, the fusion bridge is not of equal substance.

CONCLUSION

We found that bioreactor-generated cell-based bone substitutes seemed superior in fusion ability when compared to cell-free bone substitute and comparable to autograft in fusion ability, but not in bone structure. This combined with the favorable biocompatible abilities and strength comparable to human cancellous bone indicates that it might be a suitable bone substitute in spine fusion procedures.

[Double traumatic cervical spine lesion (odontoid fracture and spinal cord injury) and Klippel-Feil syndrome]

Klippel-Feil syndrome (KFS) is defined as a congenital fusion of at least two cervical vertebrae. Patients with KFS are known to be at high risk for spinal cord injury in case of cervical trauma even with weak kinetic. We report the case of a patient with C4-C5 and C6-C7 congenital fusion, harbouring C5-C6 post-traumatic spinal cord injury, associated with an odontoid fracture type 2 of Anderson and D'Alonzo classification following a motorbike accident.

Vertebral body osteolysis following the use of bone morphogenetic protein in spinal surgery: a mimicker of infection

This report describes the imaging findings in three patients who developed lumbar spine osteolysis after posterior spinal fusion using rhBMP-2. These cases demonstrate the variable course of osteolysis, as well as the importance of recognizing its radiological appearances to prevent confusion with infection following spinal fusion.