Retrograde ejaculation after anterior lumbar interbody fusion using rhBMP-2: a cohort controlled study

An Update in Complication Rates Associated With Anterior Lumbar Surgery: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic Review and meta-analysis.

OBJECTIVE

To conduct an updated systematic review and meta-analysis of complications associated with different anterior fusion techniques/approaches and adjuvant resources (i.e., computed tomography angiography (CTA), rhBMP-2, and access surgeons).

METHODS

A systematic review was conducted from 1/1/2014-4/1/2024 for studies evaluating the incidence of complications associated with anterior lumbar procedures. Comparisons of complications were made between surgical approach, use of CTA, rhBMP-2, and access surgeons. Meta-analyses were conducted using a generalized linear mixed model.

RESULTS

54 studies were included in the final analysis with 8066 patients and an average follow-up of 31.2 months. The overall complication rate associated with anterior lumbar surgery was 13.1%, including an intraoperative complication rate of 3.8%, postoperative complication rate of 7.4%, infection rate of 1.5%, and reoperation rate of 1.7%. Forest plot analysis showed no significant difference in overall complication rates between open and mini-open techniques, although mini-open techniques were associated with lower overall reoperation rates. The use of CTA was associated with an increase in intraoperative and overall complications, and the use of an access surgeon was associated with a decreased risk of reoperation. The use of rhBMP-2 was not associated with overall complication risk.

CONCLUSIONS

While anterior lumbar surgery provides numerous benefits, surgeons and patients alike should be aware of the complication and safety profile prior to surgery. High quality studies are warranted to help elucidate the true benefit of certain techniques and adjuvant resources in reducing complications.

Advances in implants and bone graft types for lumbar spinal fusion surgery

The increasing prevalence of spinal disorders worldwide necessitates advanced treatments, particularly interbody fusion for severe cases that are unresponsive to non-surgical interventions. This procedure, especially 360° lumbar interbody fusion, employs an interbody cage, pedicle screw-and-rod instrumentation, and autologous bone graft (ABG) to enhance spinal stability and promote fusion. Despite significant advancements, a persistent 10% incidence of non-union continues to result in compromised patient outcomes and escalated healthcare costs. Innovations in lumbar stabilisation seek to mimic the properties of natural bone, with evolving implant materials like titanium (Ti) and polyetheretherketone (PEEK) and their composites offering new prospects. Additionally, biomimetic cages featuring precisely engineered porosities and interconnectivity have gained traction, as they enhance osteogenic differentiation, support osteogenesis, and alleviate stress-shielding. However, the limitations of ABG, such as harvesting morbidities and limited fusion capacity, have spurred the exploration of sophisticated solutions involving advanced bone graft substitutes. Currently, demineralised bone matrix and ceramics are in clinical use, forming the basis for future investigations into novel bone graft substitutes. Bioglass, a promising newcomer, is under investigation despite its observed rapid absorption and the potential for foreign body reactions in preclinical studies. Its clinical applicability remains under scrutiny, with ongoing research addressing challenges related to burst release and appropriate dosing. Conversely, the well-documented favourable osteogenic potential of growth factors remains encouraging, with current efforts focused on modulating their release dynamics to minimise complications. In this evidence-based narrative review, we provide a comprehensive overview of the evolving landscape of non-degradable spinal implants and bone graft substitutes, emphasising their applications in lumbar spinal fusion surgery. We highlight the necessity for continued research to improve clinical outcomes and enhance patient well-being.

Synthesis and evaluation of a novel vancomycin-infused, biomimetic bone graft using a rat model of spinal implant-associated infection

Background

Postoperative infection is a complication of spinal fusion surgery resulting in increased patient morbidity. Strategies including intraoperative application of powdered vancomycin have been proposed to reduce the incidence of infection; however, such antimicrobial effects are short-lived.

Methods

Instrumentation of the L4-L5 vertebrae was performed mimicking pedicle screw and rod fixation in 30 rats. Titanium instrumentation inoculated with either PBS or 1×105 CFU bioluminescent MRSA, along with biomimetic bone grafts infused with varying concentrations of vancomycin and 125 µg of rhBMP-2 (BioMim-rhBMP-2-VCM) were implanted prior to closure. Infection was quantified during the six-week postoperative period using bioluminescent imaging. Arthrodesis was evaluated using micro-CT.

Results

Infected animals receiving a bone graft infused with low-dose (0.18 mg/g) or high-dose vancomycin (0.89 mg/g) both exhibited significantly lower bioluminescent signal over the six-week postoperative period than control animals inoculated with MRSA and implanted with bone grafts lacking vancomycin (p=.019 and p=.007, respectively). Both low and high-dose vancomycin-infused grafts also resulted in a statistically significant reduction in average bioluminescence when compared to control animals (p=.027 and p=.047, respectively), independent of time. MicroCT analysis of animals from each group revealed pseudoarthrosis only in the control group, suggesting a correlation between infection and pseudoarthrosis. MRSA-inoculated control animals also had significantly less bone volume formation on micro-CT than the PBS-inoculated control cohort (p<.001), the MRSA+low-dose vancomycin-infused bone graft cohort (p<.001), and the MRSA+high-dose vancomycin-infused bone graft cohort (p<.001).

Conclusion

BioMim-rhBMP-2-VCM presents a novel tissue engineering approach to simultaneously promoting arthrodesis and antimicrobial prophylaxis in spinal fusion. Despite mixed evidence of potential osteotoxicity of vancomycin reported in literature, BioMim-rhBMP-2-VCM preserved arthrodesis and osteogenesis with increasing vancomycin loading doses due to the graft's osteoinductive composition.

The Food and Drug Administration's (FDA's) 510(k) Process: A Systematic Review of 1000 Cases

BACKGROUND

The vast majority of devices cleared by the Food and Drug Administration (FDA) are through the 510(k) process, which allows medical devices to be quickly introduced into the market. The FDA 510(k) process is designed to minimize the burden and expense of bringing new devices to market; however, as a result, the FDA may be limited in its ability to establish the safety of these devices.

METHODS

The FDA 510(k) online archives were searched for devices cleared from 2013 to 2014. One thousand devices were randomly selected. PubMed was searched for each device to identify publications about the devices. The primary outcome was the percentage of devices cleared through the 510(k) process with no published research. Secondary outcomes included: conflict of interest (COI) of authors and outcomes of published studies on the devices.

RESULTS

A total of 6152 devices were cleared through the 510(k) process in 2013-2014. Of the 1000 randomly selected devices, 17.8% had published research. There were 375 manuscripts, of which 47 (12.5%) were randomized controlled trials. One-fourth (25.1%) of studies had a clearly identifiable COI, while COI was unclear for half (49.9%).

CONCLUSION AND RELEVANCE

There is limited evidence examining the safety and effectiveness of devices cleared via the 510(k) process. Thousands of devices are cleared through the FDA's 510(k) process each year with limited or no evidence publicly available. This has led to the market being introduced to potentially costly, nonbeneficial, or harmful devices. Devices, like prescription drugs, should undergo a more rigorous clearance process.

Trends, payments, and costs associated with BMP use in Medicare beneficiaries undergoing spinal fusion

BACKGROUND CONTEXT

Bone morphogenic protein (BMP) promotes bony fusion but increases costs. Recent trends in BMP use among Medicare patients have not been well-characterized.

PURPOSE

To assess utilization trends, complication, payments, and costs associated with BMP use in spinal fusion in a Medicare-insured population.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Total of 316,070 patients who underwent spinal fusion in a 20% sample of Medicare-insured patients, 2006 to 2015.

OUTCOME MEASURES

Utilization trends across time and geography, complications, payments, and costs.

METHODS

Patients were stratified by fusion type and diagnosis. Multivariable logistic and linear regression were used to adjust for the effect of baseline characteristics on complications and total payments or cost, respectively.

RESULTS

BMP was used in 60,249 cases (19.1%). BMP utilization rates decreased from 23.1% in 2006 to 12.0% in 2015, most significantly in anterior cervical (7.5%-3.1%), posterior cervical (17.0%-8.3%), and posterior lumbar fusions (31.5%-15.8%). There are significant state- and region-level geographic differences in BMP utilization. Across all years, states with the highest BMP use were Indiana (28.5%), Colorado (26.6%), and Nevada (25.7%). States with the lowest BMP use were Maine (2.3%), Vermont (8.2%), and Mississippi (10.4%). After multivariate risk adjustment, BMP use was associated with decreased overall complications in thoracic (odds ratios [OR] [95% confidence intervals [CI]): 0.89 [0.81-0.99]) and anterior lumbar fusions (OR [95% CI]: 0.89 [0.84-0.95]), as well as increased reoperation rates in anterior cervical (OR [95% CI]: 1.11 [1.04-1.19]), posterior cervical (OR (95% CI): 1.14 (1.04-1.25)), thoracic (OR (95% CI): 1.32 (1.23-1.41)), and posterior lumbar fusions (OR (95% CI): 1.11 (1.06-1.16)). BMP use was also associated with greater total costs, independent of fusion type, after multivariate risk adjustment (p<.0001). Payments, however, were comparable between groups in anterior and posterior cervical fusion with or without BMP. BMP use was associated with greater total payments in thoracic, anterior lumbar, and posterior lumbar fusions. Notably, the difference in payments was smaller than the associated cost increase in all fusion types.

CONCLUSIONS

BMP use has declined across all fusion types over the last decade, after a peak in 2007. While BMP is associated with greater costs, reimbursement does not increase proportionally with BMP cost.

L4 Corpectomy: Surgical Approaches and Mitigating the Risk of Femoral Nerve Injuries

OBJECTIVE

Because of the challenging anatomic location, corpectomies are performed less often at the fourth lumbar vertebral body than at other levels. Our objective was to review the literature of L4 corpectomy and anterior column reconstruction.

METHODS

A literature search in the Medline/PubMed database was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to identify all relevant cases and cases series describing corpectomies of the L4 vertebral body using "lumbar" AND "corpectomy" as search terms. We present an illustrative case to describe the technique.

RESULTS

We identified 18 articles with 30 patients who met the search criteria. Including our case illustration, the most common approach used was the lateral retroperitoneal approach (n = 17, 54.8%), of which 8 (26.7%) were performed via a transpsoas approach. Seven (23%) patients underwent corpectomy through a posterior approach, 4 (12.9%) through an anterior retroperitoneal approach, and 3 (10%) through combined anterior and lateral retroperitoneal. The overall complications rate was 19.3% including 1 case each of femoral nerve injury and iatrogenic lumbar nerve root injury.

CONCLUSIONS

Corpectomies of the L4 vertebral body are challenging. None of the various approaches described clearly demonstrates any superiority in mitigating the risk of neural complications. Decision making about which surgical approach to use should be based on patient-specific characteristics.

Anterior spine surgery for the treatment of complex spine pathology: a state-of-the-art review

The use of anterior spinal surgery for the treatment of spinal pathology has experienced a dramatic increase over the past decade. Long relegated to treat complicated anterior pathologies it has returned to mainstream spine surgery techniques for all types of conditions, providing a significant boost to the spine surgeons' armamentarium to address a wide variety of types of spinal diseases more effectively. Anterior surgery is useful whenever there is significant spinal pathology that requires direct visualization of the anterior vertebral column to best restore spinal alignment, structural integrity and neurologic function. These pathologies include spinal deformities, tumors, burst fractures, infections, vertebral avascular necrosis, pseudoarthrosis and other miscellaneous indications. Currently available approaches to the spine include transabdominal, paramedian retroperitoneal, lateral oblique retroperitoneal, thoracotomy, and thoracolumbar extensile. Most of the lumbar approaches are now done through a muscle splitting, minimalistic approach that has decreased their morbidity or more recently via tubular approaches, such as lateral lumbar interbody fusions or other ante-psoas approaches. New retractors, instrumentation, hyperlordotic implants, approved biologics and even image guidance for disc preparation and precise implant placement are all recent advances that will hopefully improve surgical outcomes in patients following anterior spinal surgery. Most importantly, these approaches require added expertise and training with a dedicated team consisting of an anteriorly trained spine surgeon working simultaneously with a dedicated vascular surgeon to ensure maximum safety and superior patient outcomes. This state of the review is dedicated to familiarizing practicing spine surgeons with the most commonly used anterior spinal approaches along with cutting-edge instrumentation and fusion techniques to improve their options for the treatment of difficult spinal pathologies.

Effectiveness and Feasibility of Injectable Escherichia coli-Derived Recombinant Human Bone Morphogenetic Protein-2 for Anterior Lumbar Interbody Fusion at the Lumbosacral Junction in Adult Spinal Deformity Surgery: A Clinical Pilot Study

Objective

To explore the effectiveness and feasibility of injectable Escherichia coli‐derived recombinant human bone morphogenetic protein‐2 (injectable E‐rhBMP‐2, a combination of E. coli‐derived recombinant human bone morphogenic protein‐2 and a hydrogel type beta‐tricalcium phosphate carrier) as a bone substitute for anterior lumbar interbody fusion (ALIF) of the lumbosacral junction in adult spinal deformity (ASD) patients.

Methods

A prospective single‐institution therapeutic exploratory trial was conducted. Twenty patients (average age: 69.1 years; 19 female and one male; average fusion level: 7.95) diagnosed with ASD with sagittal imbalance who underwent surgical treatment including ALIF at the lumbosacral junction from December 2017 to January 2019 were evaluated. Injectable E‐rhBMP‐2 was prepared by dissolving 3 mg of E. coli‐derived recombinant human bone morphogenetic protein‐2 in 1.5 ml H₂O and mixing in situ with 9 g hydrogel type beta‐tricalcium phosphate. This bone graft substitute was loaded onto a metal ALIF cage and L₅–S₁ ALIF was performed in routine manner. Then posterior column osteotomy with multilevel oblique lumbar interbody fusion or pedicle subtraction osteotomy with accessory rod technique was performed to restore sagittal balance. Patients were followed up for 12 months. CT‐based fusion rates were examined at 6 and 12 months after surgery. Also, clinical outcomes (Oswestry Disability Index [ODI], Visual Analog Scale [VAS] score of the back and leg) were evaluated at 6 and 12 months after surgery. All postoperative adverse events were evaluated for the association with injectable E.BMP‐2.

Results

Of the 20 patients, loss to follow‐up occurred with one patient at 6 months after surgery and one patient at 12 months after surgery, resulting in a total of 18 patients who were available for follow‐up. Six months after surgery, 68.4% patients achieved solid fusion. Twelve months after surgery, 100% fusion rate was achieved. Compared to baseline values, ODI scores improved to 45.8% and 63.7%, VAS (back) improved to 69.2% and 72.8%, and VAS (leg) improved to 49.2% and 64.8%, respectively, at 6 and 12 months after surgery (p < 0.001 for all). Ten cases of adverse events occurred. But no adverse events were associated with injectable E‐rhBMP‐2.

Conclusion

Injectable E‐rhBMP‐2 will be an effective bone graft substitute when achieving solid interbody fusion in the lumbosacral junction.

Increased risk of postoperative wound complications among obesity classes II & III after ALIF in 10-year ACS-NSQIP analysis of 10,934 cases

BACKGROUND CONTEXT

Anterior lumbar interbody fusion (ALIF) procedures for lumbar spine disease have been increasing amid a growing obese patient population with limited studies available focusing exclusively on risk-factors for post-operative ALIF complications.

PURPOSE

The objective of this study was to compare 30-day post-operative complications among different obesity World Health Organization classes according to body mass index (BMI) in comparison to non-obese patients who underwent an ALIF procedure.

STUDY DESIGN/SETTING

Retrospective cohort study of the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) from 2009 to 2019.

PATIENT SAMPLE

A total of 10,934 patients undergoing an ALIF.

OUTCOME MEASURES

Primary outcome measures include 30 day cardiac, pulmonary, urinary, infectious, and wound complications. Secondary outcomes included rates of blood transfusion, reintubation, deep vein thrombosis, pulmonary embolism, 30-day return to the operating room (OR), and 30 day mortality.

METHODS

Patients were identified by use of the current procedural terminology codes 22558 and 22585 from 2009 to 2019. Patients were divided into the following groups: non-obese (BMI 18.5-29.9 kg/m²), Obese I (BMI 30-34.9 kg/m²), Obese II (BMI 35-39.9 kg/m²), and Obese III (BMI ≥40 kg/m²). Age, gender, race, American Society of Anesthesiologists status, smoking status, hypertension requiring medication, steroid used, chronic obstructive pulmonary disease, history of a bleeding disorder, and diabetes was identified as risk factors after a univariate analysis conducted for demographic variables and pre-operative comorbidities. A multivariate logistic regression analysis was then performed to adjust for these preoperative risk factors and compare obesity classes I-III to non-obese patients.

RESULTS

Obesity classes II and III had a significant odds ratio (OR) for superficial infection (OR:2.7, 95%CI(1.7-4.5); OR:2.8, 95%CI(1.5-5.2) respectively), organ space infection (OR:3.8, 95%CI(1.6-7.4); OR:3.2, 95%CI(1.1-9.9) respectively), wound disruption (OR:2.8, 95%CI(1.1-7.4); OR:4.6, 95%CI(1.6-13.6) respectively), and total wound complication (OR:2.6, 95%CI(1.8-3.9); OR:3.4, 95%CI(2.2-5.4) respectively) following a multivariate logistic regression analysis.

CONCLUSIONS

Risk for post-operative wound complications following an ALIF were found to be significantly higher for obesity classes II-III in comparison to non-obese patients. These findings can further support the use of additional wound care in the perioperative setting for certain levels of obesity.

Overexpression Effects of miR-424 and BMP2 on the Osteogenesis of Wharton's Jelly-Derived Stem Cells

Recently, the translational application of noncoding RNAs is accelerated dramatically. In this regard, discovering therapeutic roles of microRNAs by developing synthetic RNA and vector-based RNA is attracting attention. Here, we studied the effect of BMP2 and miR-424 on the osteogenesis of Wharton's jelly-derived stem cells (WJSCs). For this purpose, human BMP2 and miR-424 DNA codes were cloned in the third generation of lentiviral vectors and then used for HEK-293T cell transfection. Lentiviral plasmids contained miR424, BMP-2, miR424-BMP2, green fluorescent protein (GFP) genes, and helper vectors. The recombinant lentiviral particles transduced the WJSCs, and the osteogenesis was evaluated by real-time PCR, Western blot, Alizarin Red staining, and alkaline phosphatase enzyme activity. According to the results, there was a significant increase in the expression of the BMP2 gene and secretion of Osteocalcin protein in the group of miR424-BMP2. Moreover, the amount of dye deposition in Alizarin Red staining and alkaline phosphatase activity was significantly higher in the mentioned group (p < 0.05). Thus, the current study results clarify the efficacy of gene therapy by miR424-BMP2 vectors for bone tissue engineering. These data could help guide the development of gene therapy-based protocols for bone tissue engineering.

Is there a variance in complication types associated with ALIF approaches? A systematic review

Purpose

Anterior lumbar interbody fusion (ALIF) is a well-established alternative to posterior-based interbody fusion techniques, with approach variations, such as retroperitoneal, transperitoneal, open, and laparoscopic well described. Variable rates of complications for each approach have been enumerated in the literature. The purpose of this study was to elucidate the comparative rates of complications across approach type.

Methods

A systematic review of search databases PubMed, Google Scholar, and OVID Medline was made to identify studies related to complication-associated ALIF. PRISMA guidelines were utilised for this review. Meta-analysis was used to compare intraoperative and postoperative complications with ALIF for each approach.

Results

A total of 4575 studies were identified, with 5728 patients across 31 studies included for review following application of inclusion and exclusion criteria. Meta-analysis demonstrated the transperitoneal approach resulted in higher rates of retrograde ejaculation (RE) (p < 0.001; CI = 0.05–0.21) and overall rates of complications (p = 0.05; CI = 0.00–0.23). Rates of RE were higher at the L5/S1 intervertebral level. Rates of vessel injury were not significantly higher in either approach method (p = 0.89; CI =  − 0.04–0.07). Rates of visceral injury did not appear to be related to approach method. Laparoscopic approaches resulted in shorter inpatient stays (p = 0.01).

Conclusion

Despite the transperitoneal approach being comparatively underpowered, its use appears to result in a significantly higher rate of intraoperative and postoperative complications, although confounders including use of bone morphogenetic protein (BMP) and spinal level should be considered. Laparoscopic approaches resulted in shorter hospital stays; however, its steep learning curve and longer operative time have deterred surgeons from its widespread adaptation.

Iatrogenic effects of radical cancer surgery on male fertility

Iatrogenic causes of male infertility can include medications, chemotherapy, radiation, and surgery. In this review, we discuss commonly performed urologic cancer surgeries and nonurologic surgeries that harbor a high risk of iatrogenic infertility. These include radical prostatectomy, radical cystectomy, retroperitoneal lymph node dissection, pelvic colon surgery, and anterior spine surgery. In addition, we review the anatomy and surgical strategies that help to reduce the risks of infertility. With an increase in life expectancy and improvements in fertility preservation, it is important to properly counsel patients about the risks of infertility and provide options for fertility preservation before surgery.

Regional Gene Therapy with Transduced Human Cells: The Influence of "Cell Dose" on Bone Repair

Regional gene therapy using a lentiviral vector containing the BMP-2 complementary DNA (cDNA) has been shown to heal critical-sized bone defects in rodent models. An appropriate "cellular dose" needs to be defined for eventual translation into human trials. The purpose of this study was to evaluate bone defect healing potential and quality using three different doses of transduced human bone marrow cells (HBMCs). HBMCs were transduced with a lentiviral vector containing either BMP-2 or green fluorescent protein (GFP). All cells were loaded onto compression-resistant matrices and implanted in the bone defect of athymic rats. Treatment groups included femoral defects that were treated with a low-dose (1 × 10⁶ cells), standard-dose (5 × 10⁶ cells), and high-dose (1.5 × 10⁷ cells) HBMCs transduced with lentiviral vector containing BMP-2 cDNA. The three control groups were bone defects treated with HBMCs that were either nontransduced or transduced with vector containing GFP. All animals were sacrificed at 12 weeks. The bone formed in each defect was evaluated with plain radiographs, microcomputed tomography (microCT), histomorphometric analysis, and biomechanical testing. Bone defects treated with higher doses of BMP-2-producing cells were more likely to have healed (6/14 of the low-dose group; 12/14 of the standard-dose group; 14/14 of the high-dose group; χ²(2) = 15.501, p < 0.001). None of the bone defects in the control groups had healed. Bone defects treated with high dose and standard dose of BMP-2-producing cells consistently outperformed those treated with a low dose in terms of bone formation, as assessed by microCT and histomorphometry, and biomechanical parameters. However, statistical significance was only seen between defects treated with high dose and low dose. Larger doses of BMP-2-producing cells were associated with a higher likelihood of forming heterotopic ossification. Femurs treated with a standard- and high-dose BMP-2-producing cells demonstrated similar healing and biomechanical properties. Increased doses of BMP-2 delivered through higher cell doses have the potential to heal large bone defects. Adapting regional gene therapy for use in humans will require a balance between promoting bone repair and limiting heterotopic ossification. Impact statement Critical bone loss may result from complex traumatic bone injury (i.e., open fracture or blast injury), revision total joint arthroplasty, and spine pseudoarthrosis. This is a challenging clinical problem to treat and regional gene therapy is an innovative means of addressing it. This study provides information regarding the quantity of cells or "cell dose" of transduced cells needed to treat a critical-sized bone defect in a rat model. This information may be extrapolated for use in humans in future trials.

Vulnerability of the L5 nerve root during anterior lumbar interbody fusion at L5-S1: case series and review of the literature

OBJECTIVE

Nerve root injuries associated with anterior lumbar interbody fusion (ALIF) are uncommonly reported in the literature. This case series and review aims to describe the etiology of L5 nerve root injury following ALIF at L5-S1.

METHODS

The authors performed a single-center retrospective review of prospectively collected data of patients who underwent surgery between 2017 and 2019 who had postoperative L5 nerve root injuries after stand-alone L5-S1 ALIF. They also reviewed the literature with regard to nerve root injuries after ALIF procedures.

RESULTS

The authors report on 3 patients with postoperative L5 radiculopathy. All 3 patients had pain that improved. Two of the 3 patients had a neurological deficit, one of which improved.

CONCLUSIONS

Stretch neuropraxia from overdistraction is an important cause of postoperative L5 radiculopathy after L5-S1 ALIF. Judicious use of implants and careful preoperative planning to determine optimal implant sizes are paramount.

Evaluation of the optimal dosage of BMP-9 through the comparison of bone regeneration induced by BMP-9 versus BMP-2 using an injectable microparticle embedded thermosensitive polymeric carrier in a rat cranial defect model

Bone morphogenetic proteins (BMPs) are well known as enhancers and facilitators of osteogenesis during bone regeneration. The use of recombinant BMP-2 (rhBMP-2) in bone defect healing has drawbacks, which has driven the scouting for alternatives, such as recombinant BMP-9 (rhBMP-9), to provide comparable new bone formation. However, the dosage of rhBMP-9 is quintessential for the facilitation of adequate bone defect healing. Therefore, this study has been designed to evaluate the optimal dosage of BMP-9 by comparing the bone defect healing induced by rhBMP-9 over rhBMP-2. The chitosan (CS) microparticles (MPs), coated with BMPs, were embedded in a thermoresponsive methylcellulose (MC) and calcium alginate (Alg) based injectable delivery system containing a dosage of either 0.5 μg or 1.5 μg of the respective rhBMP per bone defect. A 5 mm critical-sized cranial defect rat model has been used in this study, and bone tissues were harvested at eight weeks post-surgery. The standard tools for comparing the new bone regeneration included micro computerized tomography (micro-CT) and histological analysis. A novel perspective of analyzing the new bone quality and crystallinity was employed by using Raman spectroscopy, along with its elastic modulus quantified through Atomic Force Microscopy (AFM). Results showed that the rhBMP-9 administered at a dosage of 1.5 μg per bone defect, using this delivery system, can adequately facilitate the bone void filling with ample new bone mineralization and crystallinity as compared to rhBMP-2, thus approving the hypothesis for a viable rhBMP-2 alternative.

Impact of surgeon rhBMP-2 cost awareness on complication rates and health system costs for spinal arthrodesis

OBJECTIVE

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is used in spinal arthrodesis procedures to enhance bony fusion. Research has suggested that it is the most cost-effective fusion enhancer, but there are significant upfront costs for the healthcare system. The primary objective of this study was to determine whether intraoperative dosing and corresponding costs changed with surgeon cost awareness. The secondary objective was to describe surgical complications before and after surgeon awareness of rhBMP-2 cost.

METHODS

A retrospective medical record review was conducted to identify patients who underwent spinal arthrodesis procedures performed by a single surgeon, supplemented with rhBMP-2, from June 2016 to June 2018. Collected data included rhBMP-2 dosage, rhBMP-2 list price, and surgical complications. Expected Medicare reimbursement was calculated. Data were analyzed before and after surgeon awareness of rhBMP-2 cost.

RESULTS

Forty-eight procedures were performed using rhBMP-2, 16 before and 32 after surgeon cost awareness. Prior to cost awareness, the most frequent rhBMP-2 dosage level was x-small (38.9%, n = 7), followed by large (27.8%, n = 5) and small (22.2%, n = 4). After cost awareness, the most frequent rhBMP-2 dosage was xx-small (56.8%, n = 21), followed by x-small (21.6%, n = 8) and large (13.5%, n = 5). The rhBMP-2 average cost per surgery was $4116.56 prior to surgeon cost awareness versus $2268.38 after. Two complications were observed in the pre-cost awareness surgical group; 2 complications were observed in the post-cost awareness surgical group.

CONCLUSIONS

Surgeon awareness of rhBMP-2 cost resulted in use of smaller rhBMP-2 doses, decreased rhBMP-2 cost per surgery, and decreased overall hospital admission charges, without a detectable increase in surgical complications.

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

Regenerative medicine is becoming a rapidly evolving technique in today's biomedical progress scenario. Scientists around the world suggest the use of naturally synthesized biomaterials to repair and heal damaged cells. Hydroxyapatite (HAp) has the potential to replace drugs in biomedical engineering and regenerative drugs. HAp is easily biodegradable, biocompatible, and correlated with macromolecules, which facilitates their incorporation into inorganic materials. This review article provides extensive knowledge on HAp and collagen-containing compositions modified with drugs, bioactive components, metals, and selected nanoparticles. Such compositions consisting of HAp and collagen modified with various additives are used in a variety of biomedical applications such as bone tissue engineering, vascular transplantation, cartilage, and other implantable biomedical devices.

Designing biomaterials for the delivery of RNA therapeutics to stimulate bone healing

Ribonucleic acids (small interfering RNA, microRNA, and messenger RNA) have been emerging as a promising new class of therapeutics for bone regeneration. So far, however, research has mostly focused on stability and complexation of these oligonucleotides for systemic delivery. By comparison, delivery of RNA nanocomplexes from biomaterial carriers can facilitate a spatiotemporally controlled local delivery of osteogenic oligonucleotides. This review provides an overview of the state-of-the-art in the design of biomaterials which allow for temporal and spatial control over RNA delivery. We correlate this concept of spatiotemporally controlled RNA delivery to the most relevant events that govern bone regeneration to evaluate to which extent tuning of release kinetics is required. In addition, inspired by the physiological principles of bone regeneration, potential new RNA targets are presented. Finally, considerations for clinical translation and upscaled production are summarized to stimulate the design of clinically relevant RNA-releasing biomaterials.

The effect of platelet-rich plasma on the fusion rate and clinical outcome of spinal fusion surgery: A systematic review and meta-analysis

BACKGROUND

Platelet-rich plasma (PRP) is widely used in many orthopedic surgeries and spinal disease treatments; however, the effect of PRP on spinal fusion remains controversial.

QUESTIONS/PURPOSES

To assess the fusion rate and clinical results of PRP compared with non-PRP administration in the treatment of spinal fusion with regard to decreasing pain and improving healing and function.

PATIENTS AND METHODS

Studies comparing PRP to non-PRP treatment with respect to the fusion rate and clinical outcome in patients who underwent spinal fusion surgery were included.

RESULT

Three randomized controlled trials (RCTs) and 7 prospective cohort studies were identified. The spinal fusion rate was not significantly different between the groups in all RCTs or cohort studies at the final follow-up. In comparison, PRP significantly reduced pain after surgery as evaluated in the RCT analysis and the complication rate did not differ significantly between the two groups.

CONCLUSION

According to the available studies, PRP does not contribute to the union rate, relieve pain or increase the complication rate in spinal fusion surgery. As clinical heterogeneity exists in these studies, further large, well-designed RCTs that focus on the standard assessment of PRP are needed.

Safety Profile and Radiographic and Clinical Outcomes of Stand-Alone 2-Level Anterior Lumbar Interbody Fusion: A Case Series of 41 Consecutive Patients

Objective: The use of stand-alone 2-level anterior lumbar interbody fusion (ALIF) for degenerative lumbar disease has been increasing as an alternative to routinely augmenting these constructs with posterior fixation or fusion. Despite the potential benefits of a stand-alone approach (decreased cost and operative time, decreased pain and early mobilization), there is a paucity of information regarding these operations in the literature. This investigation aimed to determine the safety profile, radiographic outcomes including fusion rates, improvement in preoperative pain, and spinopelvic parameter modification, for patients undergoing stand-alone 2-level ALIF.

Methods: This retrospective case series involved a chart review of all patients undergoing 2-level stand-alone ALIF at a single tertiary hospital from 2008 to 2018. Data included patient demographics, hospitalization, complications and radiological studies. Visual analog scale (VAS) back and leg scores were measured via patient-administered surveys preoperatively and up to 18 weeks postoperatively.

Results: Forty-one patients who underwent L4-S1 stand-alone ALIF were included. Sixteen (39%) of patients had undergone previous posterior lumbar surgery. Length of stay averaged 4.2 days. Complication rates were comparable to 1-level ALIF. Two patients required reoperation. Fusion rates were 100% for L4-5 and 94.4% for L5-S1. There was no significant change in lumbar lordosis (LL) or LL-pelvic incidence (PI), but there was improved segmental lordosis (SL) and disc height at L4-S1 on final follow-up imaging. There was also modest but statistically significant improvement in VAS back and leg scores.

Conclusions: Stand-alone 2-level ALIF is an option for a surgeon to perform in the absence of significant instability, even in the setting of prior posterior surgery. These procedures increase SL and disc height, but do not have the same effect on LL or LL-PI.

Proteomics of regenerated tissue in response to a titanium implant with a bioactive surface in a rat tibial defect model

Due to their excellent mechanical and biocompatibility properties, titanium-based implants are successfully used as biomedical devices. However, when new bone formation fails for different reasons, impaired fracture healing becomes a clinical problem and affects the patient's quality of life. We aimed to design a new bioactive surface of titanium implants with a synergetic PEG biopolymer-based composition for gradual delivery of growth factors (FGF2, VEGF, and BMP4) during bone healing. The optimal architecture of non-cytotoxic polymeric coatings deposited by dip coating under controlled parameters was assessed both in cultured cells and in a rat tibial defect model (100% viability). Notably, the titanium adsorbed polymer matrix induced an improved healing process when compared with the individual action of each biomolecules. High-performance mass spectrometry analysis demonstrated that recovery after a traumatic event is governed by specific differentially regulated proteins, acting in a coordinated response to the external stimulus. Predicted protein interactions shown by STRING analysis were well organized in hub-based networks related with response to chemical, wound healing and response to stress pathways. The proposed functional polymer coatings of the titanium implants demonstrated the significant improvement of bone healing process after injury.

Platelet-rich plasma for the spinal fusion

There has been a wide interest in using platelet-rich plasma (PRP) as a therapeutic agent to enhance spinal fusion. There are two review articles based only on clinical studies regarding the effect of PRP on spinal fusion. However, with regard to both animal model studies and clinical studies, there is no review studies regarding its effect on spinal fusion and no review studies focusing on the platelet count and the concentration of the growth factor in the PRP. The purpose is to review the literatures about the effect of PRP on spinal fusion according to the animal model studies and clinical studies, focusing on the effect of the platelet count and the concentration of the growth factor in the PRP. A PubMed search was performed for English-language articles. We identified 20 articles regarding the effect of PRP on fusion in animal model studies and clinical studies, of which 16 articles met the study criteria of case-control studies or prospective randomized studies for the spinal fusion. The articles were categorized into small-sized animal model, middle-sized animal model, and clinical studies. Studies have shown both beneficial and inhibitory effects. The conclusion that PRP has the stimulating effect on spinal fusion was not reached. However, PRP might promote the human spinal fusion if the platelet count or the concentration of growth factors in the PRP increases.

Locally Applied Simvastatin as an Adjunct to Promote Spinal Fusion in Rats

STUDY DESIGN

Basic Science.

OBJECTIVE

To determine if locally delivered simvastatin can enhance bone formation in a rat spinal fusion model.

SUMMARY OF BACKGROUND DATA

The bone-anabolic properties of statins in fracture healing are well established, however, few studies have evaluated the impact of locally delivered statins in spinal fusion.

METHODS

We formulated poly(lactic-co-glycolic acid) (PLGA) nanoparticles by adapting previously published techniques. Two types of nanoparticles were created: simvastatin nanoparticles (SimNP) and nanoparticles without simvastatin (BlankNP). Drug elution from SimNP was characterized. Osteoblastic differentiation was analyzed using MC3T3-E1 cells cultured in differentiation medium containing SimNP or BlankNP. Forty male 12 week old outbred Wistar rats underwent uninstrumented posterolateral fusion using iliac crest bone graft and BlankNP, SimNP or simvastatin drug. X-rays to assess bone formation were obtained at 4 weeks and 9 weeks post-operatively. Spines were explanted at 9 weeks for micro-CT analysis, and a blinded manual assessment of fusion (MAF).

RESULTS

SimNP achieved a release efficiency of 74.1% with ∼50% release occurring in the first day. Simvastatin and SimNP treated cells showed significantly greater expression of osteopontin (OPN) and osteocalcin (OCN). On micro-CT analysis, SimNP animals had higher bone volume and percent bone volume (bone volume/total volume) than control animals. SimNP rats had higher X-ray scores at 4 weeks (p=0.010) and 9 weeks (p<0.001) relative to BlankNP. MAF showed that SimNP had a higher fusion rate than BlankNP (42.9% vs. 0%, p=0.006).

CONCLUSION

We were able to validate that sustained release of simvastatin via a PLGA nanoparticle. SimNP was able to induce an increase in mineralization as well as an increase in markers of bone formation. X-ray analysis, micro-CT quantification, and MAF assessment of SimNP treated rats showed significantly greater bone formation and fusion mass strength relative to vehicle treated animals. Simvastatin may be a safe, cost-effective bone anabolic agent for use in spinal fusion.

LEVEL OF EVIDENCE

N/A.

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.

Effect of bone sialoprotein coating on progression of bone formation in a femoral defect model in rats

PURPOSE

In orthopedic and trauma surgery, calcium phosphate cement (CPC) scaffolds are widely used as substitute for autologous bone grafts. The purpose of this study was to evaluate bone formation in a femoral condyle defect model in rats after scaffold-coating with bioactive bone sialoprotein (BSP). Our hypothesis was that BSP-coating results in additional bone formation.

METHODS

In 20 Wistar rats, defects of 3.0 mm diameter were drilled into the lateral femoral condyles of both legs. BSP-coated scaffolds or uncoated control scaffolds were implanted into the defects. After 4 and 8 weeks, five rats of each group were euthanized, respectively. µCT scans and histological analyses were performed. The ratio of bone volume-total volume (BV/TV) was analyzed and histological sections were evaluated.

RESULTS

At week four, bone fraction reached 5.2 ± 1.7% in BSP-coated scaffolds and 4.5 ± 3.2% in the control (p = 0.06). While bone fraction of the BSP-group did not change much between week four and eight [week eight: 5.4 ± 3.8% (p = 0.53)], there was a tendency towards an increase in the control [week eight: 7.0 ± 2.2% (p = 0.08)]. No significant difference in bone fraction were observable between BSP-coated and uncoated scaffolds at week eight (p = 0.08).

CONCLUSIONS

A significant superiority of BSP-coated scaffolds over uncoated scaffolds could not be proven. However, BSP-coating showed a tendency towards improving bone ingrowth in the scaffolds 4 weeks after implantation. This effect was only short-lived: bone growth in the control scaffolds tended to outpace that of the BSP-group at week eight.

Autograft, Allograft, and Bone Graft Substitutes: Clinical Evidence and Indications for Use in the Setting of Orthopaedic Trauma Surgery

Bone grafts are the second most common tissue transplanted in the United States, and they are an essential treatment tool in the field of acute and reconstructive traumatic orthopaedic surgery. Available in cancellous, cortical, or bone marrow aspirate form, autogenous bone graft is regarded as the gold standard in the treatment of posttraumatic conditions such as fracture, delayed union, and nonunion. However, drawbacks including donor-site morbidity and limited quantity of graft available for harvest make autograft a less-than-ideal option for certain patient populations. Advancements in allograft and bone graft substitutes in the past decade have created viable alternatives that circumvent some of the weak points of autografts. Allograft is a favorable alternative for its convenience, abundance, and lack of procurement-related patient morbidity. Options include structural, particulate, and demineralized bone matrix form. Commonly used bone graft substitutes include calcium phosphate and calcium sulfate synthetics-these grafts provide their own benefits in structural support and availability. In addition, different growth factors including bone morphogenic proteins can augment the healing process of bony defects treated with grafts. Autograft, allograft, and bone graft substitutes all possess their own varying degrees of osteogenic, osteoconductive, and osteoinductive properties that make them better suited for different procedures. It is the purpose of this review to characterize these properties and present clinical evidence supporting their indications for use in the hopes of better elucidating treatment options for patients requiring bone grafting in an orthopaedic trauma setting.

Therapeutic potential of growth differentiation factors in the treatment of degenerative disc diseases

Intervertebral disc (IVD) degeneration is a major contributing factor to chronic low back pain and disability, leading to imbalance between anabolic and catabolic processes, altered extracellular matrix composition, loss of tissue hydration, inflammation, and impaired mechanical functionality. Current treatments aim to manage symptoms rather than treat underlying pathology. Therefore, IVD degeneration is a target for regenerative medicine strategies. Research has focused on understanding the molecular process of degeneration and the identification of various factors that may have the ability to halt and even reverse the degenerative process. One such family of growth factors, the growth differentiation factor (GDF) family, have shown particular promise for disc regeneration in in vitro and in vivo models of IVD degeneration. This review outlines our current understanding of IVD degeneration, and in this context, aims to discuss recent advancements in the use of GDF family members as anabolic factors for disc regeneration. An increasing body of evidence indicates that GDF family members are central to IVD homeostatic processes and are able to upregulate healthy nucleus pulposus cell marker genes in degenerative cells, induce mesenchymal stem cells to differentiate into nucleus pulposus cells and even act as chemotactic signals mobilizing resident cell populations during disc injury repair. The understanding of GDF signaling and its interplay with inflammatory and catabolic processes may be critical for the future development of effective IVD regeneration therapies.

Sexual activity after spine surgery: a systematic review

INTRODUCTION

Sexual function is an important determinant of quality of life, and factors such as surgical approach, performance of fusion, neurological function and residual pain can affect it after spine surgery. Our aim was to perform a systematic review to collate evidence regarding the impact of spine surgery on sexual function.

METHODS

A systematic review of studies reporting measures of sexual function, and incidence of adverse sexual outcomes (retrograde ejaculation) after major spine surgery was done, regardless of spinal location. Pubmed (MEDLINE) and Google Scholar databases were queried using the following search words "Sex", "Sex life", "Sexual function", "Sexual activity", "retrograde ejaculation", "Spine", "Spine surgery", "Lumbar surgery", "Lumbar fusion", "cervical spine", "cervical fusion", "Spinal deformity", "scoliosis" and "Decompression". All articles published between 1997 and 2017 were retrieved from the database. A total of 81 studies were included in the final review.

RESULTS

Majority of the studies were retrospective case series and were low quality (Level IV) in evidence. Anterior lumbar approaches were associated with a higher incidence of retrograde ejaculation, especially with the utilization of transperitoneal laparoscopic approach. There is inconclusive evidence on the preferred sexual position following fusion, and also on the impact of BMP-2 usage on retrograde ejaculation/sexual dysfunction.

CONCLUSION

Despite limited evidence from high-quality articles, there is a general trend towards improvement of sexual activity and function after spine surgery. Future studies incorporating specific assessments of sexual activity will be required to address this important determinant of quality of life so that appropriate pre-operative counselling can be done by providers. These slides can be retrieved under Electronic Supplementary Material.

Transforaminal Lumbar Interbody Fusion With Viable Allograft: 75 Consecutive Cases at 12-Month Follow-up

Background

When conservative treatments fail to alleviate the discomfort of abnormal motion, spinal fusion has been shown to provide symptomatic treatment for spinal instability, stenosis, spondylolisthesis, and symptomatic degenerative disc disease. The trend and rates of fusion over the past few years have been dramatic in the United States. Accompanying that higher incidence has been the shifting from traditional open surgery to minimally invasive techniques to reduce scar tissue formation, extent of muscle stripping, and muscle retraction which all have been shown to adversely affect outcomes. Other reasons supporting the widespread transition to minimally invasive surgical (MIS) techniques include decreased postoperative pain, decreased intraoperative blood loss, shorter postoperative hospital stay, faster return to normal activity, and reduced reoperation rates. Spinal fusion procedures rely on a bony fusion substrate in addition to fixation hardware. While available grafting options include autogenous, allogeneic, and synthetic materials, recent interest in viable allograft material with living cells has drawn attention and attraction for incorporating a biologic basis for regenerative consideration. A recent viable allograft, complete with cellular and designated bone carrier (VIA Graft, Vivex Biomedical, Marietta, Georgia) has been developed. This study represents a retrospective review of a single-practice, single-surgeon evaluation of the product in 75 consecutive patients for fusion by computed tomography (CT) and radiographic evaluation at 12 months in conjunction with a MIS approach. Viable allograft was used to fill the peri-implant space, and central implant lumen was filled with a cancellous bone sponge soaked in perivertebral bone marrow. Posterolateral supplementation was attained with beta-tricalcium phosphate as a bulking agent.

Methods

A retrospective review identified patients treated for both primary and revision surgery who received VIA Graft cellular bone matrix material in minimally invasive interbody fusion (MIS-TLIF) with a minimum of 12-month follow up. The patient diagnoses included radiculopathy in all instances and varied collateral indications such as foraminal collapse, recurrent disc herniation, and spondylolisthesis to which pain and morbidity had been unresolved by conservative treatment. Adverse events including infection, revisions, and evidence of immune response were evaluated and patient comorbidities defined for the entire population of patients. Patient fusion status was assessed using thin slice CT by 2 independent radiologists separate from the surgeon. There were 75 consecutive adult patients with degenerative conditions of the lumbar spine who underwent MIS-TLIF surgery of which 40 (53%) were male and 35 (47%) were female. Mean age, height, and weight were 58 years, 170.18 cm (67 in), and 88.45 kg (195 lbs), respectively. The mean body mass index was 30. There were 16 patients (21%) who smoked and 12 (16%) with a history of diabetes. Independent blinded review of fusion was obtained by a board certified musculoskeletal radiologist and an experienced board certified orthopaedic surgeon to assess patient fusion status. Spinal segments were deemed fused if 12-month CT scans demonstrated evidence of bridging bone at the fusion site without observed motion on flexion-extension radiographs. Findings such as osteolysis around the implant or pedicle screws, extensive endplate cystic changes, or linear defects parallel to the endplates through intradiscal new bone formation were interpreted as signs of pseudarthrosis. Interobserver and intraobserver error and κ assessments were analyzed to assure agreement in the CT outcomes assessment where interpretation of κ were as follows: <0.00 = poor agreement, 0.00-0.20 = slight agreement, 0.21-0.40 = fair agreement, 0.41-0.60 = moderate agreement, 0.61-0.80 = substantial agreement, and 0.81-1.00 = almost perfect agreement. Differences were resolved by consensus amongst the observers.

Results

In total, 96% of the 75 patients with a total of 85 levels (96.5% of levels treated) achieved a fusion at 12 months. There were no perioperative or latent complications and no transfusions in all 75 patients.

Conclusions

In this population, 96% of the patients treated achieved the surgical objective in 96.5% of the levels treated.

Level of Evidence

IV.

Clinical Relevance

The high rate of fusion, the lack of secondary morbidity with autologous bone harvest, and the clinical success account for the benefits of viable allograft matrix for MIS-TLIF use.

In situ bone tissue engineering via ultrasound-mediated gene delivery to endogenous progenitor cells in mini-pigs

More than 2 million bone-grafting procedures are performed each year using autografts or allografts. However, both options carry disadvantages, and there remains a clear medical need for the development of new therapies for massive bone loss and fracture nonunions. We hypothesized that localized ultrasound-mediated, microbubble-enhanced therapeutic gene delivery to endogenous stem cells would induce efficient bone regeneration and fracture repair. To test this hypothesis, we surgically created a critical-sized bone fracture in the tibiae of Yucatán mini-pigs, a clinically relevant large animal model. A collagen scaffold was implanted in the fracture to facilitate recruitment of endogenous mesenchymal stem/progenitor cells (MSCs) into the fracture site. Two weeks later, transcutaneous ultrasound-mediated reporter gene delivery successfully transfected 40% of cells at the fracture site, and flow cytometry showed that 80% of the transfected cells expressed MSC markers. Human bone morphogenetic protein-6 (BMP-6) plasmid DNA was delivered using ultrasound in the same animal model, leading to transient expression and secretion of BMP-6 localized to the fracture area. Micro-computed tomography and biomechanical analyses showed that ultrasound-mediated BMP-6 gene delivery led to complete radiographic and functional fracture healing in all animals 6 weeks after treatment, whereas nonunion was evident in control animals. Collectively, these findings demonstrate that ultrasound-mediated gene delivery to endogenous mesenchymal progenitor cells can effectively treat nonhealing bone fractures in large animals, thereby addressing a major orthopedic unmet need and offering new possibilities for clinical translation.

Effect of bone sialoprotein coated three-dimensional printed calcium phosphate scaffolds on primary human osteoblasts

The combination of the two techniques of rapid prototyping 3D-plotting and bioactive surface functionalization is presented, with emphasis on the in vitro effect of Bone Sialoprotein (BSP) on primary human osteoblasts (hOBs). Our primary objective was to demonstrate the BSP influence on the expression of distinctive osteoblast markers in hOBs. Secondary objectives included examinations of the scaffolds' surface and the stability of BSP-coating as well as investigations of cell viability and proliferation. 3D-plotted calcium phosphate cement (CPC) scaffolds were coated with BSP via physisorption. hOBs were seeded on the coated scaffolds, followed by cell viability measurements, gene expression analysis and visualization. Physisorption is an effective method for BSP-coating. Coating with higher BSP concentrations leads to enhanced BSP release. Two BSP concentrations (50 and 200 μg/mL) were examined in this study. The lower BSP concentration (50 µg/mL) decreased ALP and SPARC expression, whereas the higher BSP concentration (200 μg/mL) did not change gene marker expression. Enhanced cell viability was observed on BSP-coated scaffolds on day 3. hOBs developed a polygonal shape and connected in an intercellular network under BSP influence. Quantitative cell morphology analyses demonstrated for BSP-coated CPCs an enhanced cell area and reduced circularity. The strength of the above-mentioned effects of BSP-coated scaffolds in vivo is unknown, and future work is focusing on bone ingrowth and vascularization in vivo. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2565-2575, 2018.

Long-term Radiological and Clinical Outcomes After Using Bone Marrow Mesenchymal Stem Cells Concentrate Obtained With Selective Retention Cell Technology in Posterolateral Spinal Fusion

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of this study was to evaluate the long-term clinical and radiological outcomes of the use of bone marrow mesenchymal stem cell concentrate obtained with selective cell retention technology using Cellect with a particular collagen scaffold, Healos for posterolateral spinal fusion.

SUMMARY OF BACKGROUND DATA

With the increasing rate of spinal fusion, the problem of pseudarthrosis, which contributes to recurrent pain with patient disability, is considered to be the most common cause of revision lumbar spine surgery. Intensive research is being carried out to develop an alternative source of bone grafting and improve the spinal fusion rate.

METHODS

A retrospective review of hospital records was performed. Identified patients were contacted to have a clinical and radiological evaluation follow-up. Clinical outcome was evaluated using visual analog scales for the back pain (VAS), Oswestry Disability Index (ODI) scores, and quality of life (EQ-5D) questionnaire. Radiological outcome was evaluated by performing dynamic flexion/extension lateral views and calculation of segmental Cobb angle. Any implant-associated complication was reported. Computed tomography (CT) scans were also performed.

RESULTS

Twenty-one patients were included and all patients achieved successful fusion. The mean difference of the segmental Cobb angle was 0.48° (range 0.3°-0.7°). Computed tomography scans showed solid bilateral fusion with bridging bone (Grade I) in all patients, but solid unilateral fusion with bridging bone (Grade II) was detected for one patient at one level. Patients started to resume working activities within a mean period of 3.5 months. The VAS score for the residual back pain was 4.1 ± 2.1, whereas the ODI was 10.5 ± 5.6 points, and the mean disability index was 21.1%.

CONCLUSION

The use of bone marrow mesenchymal stem cell concentrate obtained with selective cell retention technology could be considered as an effective means for augmenting spinal fusion.

LEVEL OF EVIDENCE

3.

Efficacy of Escherichia coli-derived recombinant human bone morphogenetic protein-2 in posterolateral lumbar fusion: an open, active-controlled, randomized, multicenter trial

BACKGROUND CONTEXT

The efficacy and safety of recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute in spinal fusion has been widely researched. However, no study of the efficacy and safety of Escherichia coli-derived rhBMP-2 (E.BMP-2) with a hydroxyapatite (HA) carrier has been proposed.

PURPOSE

This study aimed to compare the efficacy and safety of fusion materials between E.BMP-2 and autogenous iliac bone graft in posterolateral fusion (PLF).

STUDY DESIGN/SETTING

An open, active-controlled, randomized, multicenter trial was carried out.

PATIENT SAMPLE

This study included 93 patients who underwent single-level lumbar or lumbosacral PLF.

OUTCOME MEASURES

The primary outcome measure was computed tomography (CT)-based fusion rate at 12 and 24 weeks. Secondary outcome measures were fusion grade by radiographs and CT at 12 and 24 weeks and changes in Oswestry Disability Index (ODI), Short Form-36 (SF-36) Health Survey, and visual analogue scale (VAS).

METHODS

Patients who underwent 1-level PLF (between L1 and S1) for severe spinal stenosis or grade 1 spondylolisthesis were randomized to receive E.BMP-2 with an HA carrier (E.BMP-2 group) or autogenous iliac bone graft (AIBG group). Thin-section CT (<2 mm), VAS, ODI, and SF-36 were obtained pre- and postoperatively at 12 and 24 weeks. Outcome measures were compared between the groups.

RESULTS

A total of 100 patients were enrolled in this trial. Among them, 93 patients underwent planned surgery. Preoperative demographic and clinical data showed no difference between groups. CT-based fusion rates were 100.0% (41/41) for the E.BMP-2 group and 90.2% (46/51) for the AIBG group (p=.062) at 12 weeks and 100.0% (41/41) and 94.1% (48/51) (p=.251) at 24 weeks, respectively. Fusion grade based on radiographs and CT showed non-inferiority of the E.BMP-2 group compared with the AIBG group. All clinical parameters improved postoperatively. However, there was no difference in changes in VAS, ODI, or SF-36 between the groups. No serious adverse event related to E.BMP-2 was found.

CONCLUSIONS

The fusion rate of E.BMP-2 was comparable with that of AIBG following PLF. Good clinical efficacy and safety of E.BMP-2 in spinal fusion were also revealed. It was also suggested that HA shows suitability as a carrier for E.BMP-2. Thus, E.BMP-2 with an HA carrier can be an alternative bone graft material in spinal fusion.

Comparison of the osteogenesis and fusion rates between activin A/BMP-2 chimera (AB204) and rhBMP-2 in a beagle's posterolateral lumbar spine model

BACKGROUND CONTEXT

Activin A/BMP-2 chimera (AB204) could promote bone healing more effectively than recombinant bone morphogenetic protein 2 (rhBMP-2) with much lower dose in a rodent model, but there is no report about the effectiveness of AB204 in a large animal model.

PURPOSE

The purpose of this study was to compare the osteogenesis and fusion rate between AB204 and rhBMP-2 using biphasic calcium phosphate (BCP) as a carrier in a beagle's posterolateral lumbar fusion model.

STUDY DESIGN

This is a randomized control animal study.

METHODS

Seventeen male beagle dogs were included. Bilateral posterolateral fusion was performed at the L1-L2 and L4-L5 levels. Biphasic calcium phosphate (2 cc), rhBMP-2 (50 µg)+BCP (2 cc), or AB204 (50 µg)+BCP (2 cc) were implanted into the intertransverse space randomly. X-ray was performed at 4 and 8 weeks. After 8 weeks, the animals were sacrificed, and new bone formation and fusion rate were evaluated by manual palpation, computed tomography (CT), and undecalcified histology.

RESULTS

The AB204 group showed significantly higher fusion rate (90%) than the rhBMP-2 group (15%) or the Osteon group (6.3%) by manual palpation. On x-ray and CT assessment, fusion rate and the volume of newly formed bone were also significantly higher in AB204 group than other groups. In contrast, more osteolysis was found in rhBMP-2 group (40%) than in AB204 group (10%) on CT study. In histologic results, new bone formation was sufficient between transverse processes in AB204 group, and obvious trabeculation and bone remodeling were observed. But in rhBMP-2 group, new bone formation was less than AB204 group and osteolysis was observed between the intertransverse spaces.

CONCLUSIONS

A low dose of AB204 with BCP as a carrier significantly promotes the fusion rate in a large animal model when compared with the rhBMP-2. These findings demonstrate that AB204 could be an alternative to rhBMP-2 to improve fusion rate.

A comparison of radiographic and clinical outcomes of anterior lumbar interbody fusion performed with either a cellular bone allograft containing multipotent adult progenitor cells or recombinant human bone morphogenetic protein-2

Background

Both the map3 Cellular Allogeneic Bone Graft® and recombinant human bone morphogenetic protein 2 (rhBMP-2, Infuse®) were developed to provide an alternative to iliac crest autograft, thus eliminating the morbidity associated with its harvest. The recent literature concerning adverse events associated with the use of rhBMP-2, however, highlights the need for a safe and effective alternative. The multipotent adult progenitor cells (MAPC) found in map3 allograft may provide this alternative. The purpose of this study is to report 1-year outcomes of patients treated via anterior lumbar interbody fusion (ALIF) using either map3 Cellular Allogeneic Bone Graft or rhBMP-2 for bony fusion.

Methods

This was a retrospective evaluation of 41 patients treated via ALIF with either map3 or rhBMP-2 in a polyetheretherketone cage with posterior stabilization at 1, 2, or 3 consecutive levels (L3-S1). Patients were equally divided between treatment groups. The Oswestry Disability Index (ODI) and visual analog scores (VAS) for pain were documented as part of the standard of care. An independent radiologist assessed bridging of bone, disc height, and lordosis. Primary outcome measures included radiographic analysis of fusion by plain film and CTs. Secondary clinical outcomes included visual analogue scale for neck and arm pain and low back disability index scores.

Results

The overall fusion rate was 91%, with no significant difference between groups. Improvements in ODI and VAS were observed among all patients (p < 0.001), with no significant difference between groups for ODI (p = 0.966) or VAS (p = 0.251). There was no significant difference in terms of changes to disc height and lordosis between groups (p < 0.05). The rhBMP-2 group had increased post-operative complications when compared to the map3 group, but the low numbers precluded statistical analysis.

Conclusion

Improvements in radiographic and clinical findings were observed in both treatment groups one-year postoperatively. Map3 allograft demonstrated equivalent fusion rates to rhBMP-2. A review of surgical supply costs at the treatment facility favored map3 allograft for the treatment of patients with DDD undergoing an ALIF in 1–3 levels compared to rhBMP-2. Further studies to evaluate long-term outcomes and post-operative complications are required.

Risk Factors for Medical and Surgical Complications Following Single-Level ALIF

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The objective of the study was to determine rates of medical and surgical postoperative complications following anterior lumbar interbody fusion (ALIF) along with their associated predictors.

METHODS

Using the American College of Surgeons National Surgical Quality Improvement database, patients who underwent single-level ALIF surgery from 2006 to 2013 were identified. The 30-day rate of postoperative medical and surgical complications along with associated risk factors were evaluated by multivariable logistic regression.

RESULTS

In total, 1474 patients were included in the analysis. The overall rate of complications was 14.5%. The medical complication rate was 12.7%, while the surgical complication rate was 2.8%. Predictors of surgical complications were diabetes (odds ratio [OR] = 2.79, 95% CI = 1.20-6.01, P = .009), corticosteroid dependence (OR = 4.94, 95% CI = 1.73-14.08, P = .003), and preoperative transfusion of >4 units (OR = 7.12, 95% CI = 1.43-35.37, P = .016). Predictors of medical complications were longer operative times (OR = 4.25, 95% CI = 2.90-6.24, P < .001), preoperative anemia (OR = 2.29, 95% CI = 1.50-3.50, P < .001), >10% weight loss prior to surgery (OR = 6.79, 95% CI = 1.01-45.93, P = .049), and more severe American Society of Anesthesiologists classification (OR = 2.18, 95% CI = 1.54-3.11, P < .001).

CONCLUSIONS

The present study determines postoperative medical and surgical complications among patients undergoing ALIF. The risk factors elucidated in this study indicate that clinical practices to curtail complications should be targeted toward patients with preoperative anemia, weight loss, corticosteroid dependence, and toward those at risk for perioperative transfusions.

A Retrospective Analysis of Complications Associated With Bone Morphogenetic Protein 2 in Anterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective review.

OBJECTIVE

The aim of our study was to quantify the frequency of complications associated with recombinant human bone morphogenetic protein 2 (rhBMP-2) use in anterior lumbar interbody fusion (ALIF).

METHODS

The orthopedic subset of the Medicare database (PearlDiver) was queried for this retrospective cohort study using International Statistical Classification of Diseases 9 (ICD-9) and Current Procedure Terminology (CPT) codes for ALIF procedures with and without rhBMP-2 between 2005 and 2010. Frequencies of complications and reoperations were then identified within 1 year from the index procedure. Complications included reoperations, pulmonary embolus, deep vein thrombosis, myocardial infarction, nerve-related complications, incision and drainage procedures, wound, sepsis, pneumonia, urinary tract infections, respiratory, heterotopic ossification, retrograde ejaculation, radiculopathy, and other medical complications. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the statistical significance.

RESULTS

We identified a total of 41 865 patients who had an ALIF procedure. A total of 14 384 patients received rhBMP-2 while 27 481 did not. Overall, 6016 (41.8%) complications within 1 year from surgery were noted within the group who received rhBMP-2 and 12 950 (47.1%) complications within 1 year from surgery were recorded in those who did not receive rhBMP-2 (OR = 0.81, CI = 0.77-0.84). Overall, exposure to rhBMP-2 was associated with significantly decreased odds of complications with exception to reoperation rates (0.9% rhBMP-2 vs 1.0% no rhBMP-2; OR = 0.88, CI = 0.71-1.09) and radiculopathy (4.4% rhBMP-2 vs 4.3% no rhBMP-2; OR = 1.02, CI = 0.93-1.13).

CONCLUSIONS

The use of rhBMP-2 in patients undergoing ALIF procedure was associated with a significantly decreased rate of complications. Further studies are needed to elucidate a true incidence of complication.

Complications Associated With Bone Morphogenetic Protein in the Lumbar Spine

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

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

Study Design Retrospective database review. Objective To identify trends of the recombinant human bone morphogenetic protein-2 (rhBMP-2) use in the treatment of lumbar degenerative spondylolisthesis (LDS). Methods PearlDiver Patient Record Database was used to identify patients who underwent lumbar fusion for LDS between 2005 and 2011. The distribution of bone morphogenetic protein use rate (BR) in various surgical procedures was recorded. Patient numbers, reoperation numbers, BR, and per year BR (PYBR) were stratified by geographic region, gender, and age. Results There were 11,335 fusion surgeries, with 3,461 cases using rhBMP-2. Even though PYRB increased between 2005 and 2008, there was a significant decrease in 2010 for each procedure: 404 (34.5%) for posterior interbody fusion, 1,282 (34.3%) for posterolateral plus posterior interbody fusion (PLPIF), 1,477 (29.2%) for posterolateral fusion, and 335 (22.4%) for anterior lumbar interbody fusion. In patients using rhBMP-2, the reoperation rate was significantly lower than in patients not using rhBMP-2 (0.69% versus 1.07%, p < 0.0001). Male patients had higher PYBR compared with female patients in 2008 and 2009 (p < 0.05). The West region and PLPIF had the highest BR and PYBR. Conclusions Our data shows that the revision rates were significantly lower in patients treated with rhBMP-2 compared with patients not treated with rhBMP-2. Furthermore, rhBMP-2 use in LDS varied by year, region, gender, and type of fusion technique. In the West region, the posterior approach and patients 65 to 69 years of age had the highest rate of rhBMP-2 use.

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

STUDY DESIGN

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

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

1.

The potential impact of bone tissue engineering in the clinic

Bone tissue engineering (BTE) intends to restore structural support for movement and mineral homeostasis, and assist in hematopoiesis and the protective functions of bone in traumatic, degenerative, cancer, or congenital malformation. While much effort has been put into BTE, very little of this research has been translated to the clinic. In this review, we discuss current regenerative medicine and restorative strategies that utilize tissue engineering approaches to address bone defects within a clinical setting. These approaches involve the primary components of tissue engineering: cells, growth factors and biomaterials discussed briefly in light of their clinical relevance. This review also presents upcoming advanced approaches for BTE applications and suggests a probable workpath for translation from the laboratory to the clinic.

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

STUDY DESIGN

The study was based on porcine posterolateral fusion model.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

N/A.

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

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

Anatomic feasibility of a new endopelvic approach for iliac crest bone harvesting

PURPOSE

For the past few years, anterior exposure for surgery of the lumbar spine has gained popularity for the treatment of disk disease or spondylosis. Cancellous bone remains the gold standard for fusion. Iliac crest bone harvesting is safe but there are donor site complications. Bone substitutes exist, like recombinant human bone morphogenic protein-2 rhBMP-2. This alternative offers a high rate of fusion but with local and general complications. The aim of our study is to show the feasibility of an endopelvic approach for iliac bone crest harvesting to avoid donor site complication.

METHOD

Twenty anterior retroperitoneal lumbar spine approaches have been realized in the anatomy department of the University of Bordeaux. The volumes of cancellous bone have been measured and procedure complications have been reported.

RESULTS

The mean volume of cancellous bone was 5.9 cc, the maximum volume was 8.2 cc and the minimum volume was 4.5 cc. No complications have been reported during the approach or the bone harvesting.

CONCLUSIONS

Anterior retroperitoneal approach for iliac bone crest harvesting is a safe way to obtain sufficient volume of cancellous bone for a single lumbar spinal fusion. This exposure avoids the risks of an iliac crest donor site complications or rhBMP-2 complications.

Complications With the Use of BMP-2 in Scaphoid Nonunion Surgery

PURPOSE

In an effort to improve fracture healing and decrease the need for autologous bone graft, products such as recombinant human bone morphogenetic protein (rhBMP-2) have been developed and used in both spine and nonspine surgery. There is a paucity of literature regarding the use of rhBMP-2 in scaphoid nonunion surgery with very little reporting on the complications associated with its use. The objective of this study was to retrospectively review the complications documented for a case series of patients treated with revision fixation, bone graft, and rhBMP-2 in revision scaphoid nonunion surgery.

METHODS

We retrospectively reviewed 6 cases of scaphoid nonunion revision surgery comprising open reduction and internal fixation (ORIF). All cases were performed for persistent nonunion after a previous scaphoid ORIF. All patients were treated with revision screw fixation, bone graft, and rhBMP-2. Union was determined by computed tomography in all cases. Complications of nonunion, heterotopic bone formation, delayed wound healing, functional loss of motion, and need for revision surgery are reported.

RESULTS

Between 2011 and 2014, 6 cases in which rhBMP-2 was used in revision scaphoid nonunion surgery were identified. All patients had failed an initial attempt at ORIF after delayed union or nonunion. The time from injury to index ORIF ranged from 3 months to 4 years (mean, 24 months). Revision surgery with rhBMP-2 was performed at an average of 6 months from the index ORIF. Of the 6 cases, 2 had resultant persistent nonunion. Both underwent scaphoid excision and midcarpal arthrodesis. Four cases developed notable heterotopic ossification (one of which required revision surgery). One patient had a loss of functional motion after the revision surgery. There were no cases of delayed wound healing. Only one of the 6 patients healed without complications.

CONCLUSIONS

In this case series, the use of rhBMP-2 in scaphoid nonunions was associated with a higher complication rate than reported in previous studies. Surgeons performing off-label use of rhBMP-2 should be aware of the potential for complications including heterotopic ossification.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

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

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