Use of recombinant human bone morphogenetic protein-2 to achieve posterolateral lumbar spine fusion in humans: a prospective, randomized clinical pilot trial: 2002 Volvo Award in clinical studies

Development of gelatin-methacryloyl composite carriers for bone morphogenetic Protein-2 delivery: A potential strategy for spinal fusion

To reduce the risk of nonunion after spinal fusion surgery, the in situ transplantation of bone marrow mesenchymal stem cells (BMSCs) induced toward osteogenic differentiation by bone morphogenetic protein-2 (BMP2) has been proven effective. However, the current biological agents used for transplantation have limitations, such as a short half-life and low bioavailability. To address this, our study utilized a safe and effective gelatin-methacryloyl (GelMA) as a carrier for BMP2. In vitro, experiments were conducted to observe the ability of this composite vehicle to induce osteogenic differentiation of BMSCs. The results showed that the GelMA hydrogel, with its critical properties and controlled release performance of BMP2, exhibited a slow release of BMP2 over 30 days. Moreover, the GelMA hydrogel not only enhanced the proliferation activity of BMSCs but also significantly promoted their osteogenic differentiation ability, surpassing the BMP2 effects. To investigate the potential of the GelMA-BMP2 composite vehicle, a rabbit model was employed to explore its ability to induce in situ intervertebral fusion by BMSCs. Transplantation experiments in rabbits demonstrated the effective induction of intervertebral bone fusion by the GelMA-BMP2-BMSC composite vehicle. In conclusion, the GelMA-BMP2-BMSC composite vehicle shows promising prospects in preclinical translational therapy for spinal intervertebral fusion. It addresses the limitations of current biological agents and offers a controlled release of BMP2, enhancing the proliferation and osteogenic differentiation of BMSCs.

Optimal Intermittent Administration Interval of Abaloparatide for Bone Morphogenetic Protein-Induced Bone Formation in a Rat Spinal Fusion Model

Both bone morphogenetic protein 2 (BMP-2) and abaloparatide are used to promote bone formation. However, there is no consensus about their optimal administration. We investigated the optimal administration theory for the pairing of BMP-2 and abaloparatide in a rat spinal fusion model. Group I was only implanted in carriers and saline. Carriers with 3 µg of recombinant human BMP-2 (rhBMP-2) were implanted in other groups. Abaloparatide injections were administered three times a week for group III (for a total amount of 120 µg/kg in a week) and six times a week for group IV (for a total amount of 120 µg/kg in a week) after surgery. They were euthanized 8 weeks after the surgery, and we explanted their spines at that time. We assessed them using manual palpation tests, radiography, high-resolution micro-computed tomography (micro-CT), and histological analysis. We also analyzed serum bone metabolism markers. The fusion rate in Groups III and IV was higher than in Group I, referring to the manual palpation tests. Groups III and IV recorded greater radiographic scores than those in Groups I and II, too. Micro-CT analysis showed that Tbs. Sp in Groups III and IV was significantly lower than in Group I. Tb. N in Group IV was significantly higher than in Group I. Serum marker analysis showed that bone formation markers were higher in Groups III and IV than in Group I. On the other hand, bone resorption markers were lower in Group IV than in Group I. A histological analysis showed enhanced trabecular bone osteogenesis in Group IV. Frequent administration of abaloparatide may be suitable for the thickening of trabecular bone structure and the enhancement of osteogenesis in a rat spinal fusion model using BMP-2 in insufficient doses.

Does Epidural Corticosteroid Application During Spinal Surgery Reduce Postoperative Pain?: An Adjunct to Multimodal Analgesia

STUDY DESIGN

A prospective, randomized, placebo-controlled, double-blinded study.

OBJECTIVE

To examine the effect of intraoperative epidural administration of Depo-Medrol on postoperative back pain and radiculitis symptoms in patients undergoing Transforaminal Lumbar Interbody Fusion (TLIF).

SUMMARY OF BACKGROUND DATA

Postoperative pain is commonly experienced by patients undergoing spinal fusion surgery. Adequate management of intense pain is necessary to encourage early ambulation, increase patient satisfaction, and limit opioid consumption. Intraoperative steroid application has been shown to improve postoperative pain in patients undergoing lumbar decompression surgeries. There have been no studies examining the effect of epidural steroids on both back pain and radicular pain in patients undergoing TLIF.

METHOD

In all, 151 patients underwent TLIF surgery using rh-BMP2 with 3 surgeons at a single institution. Of those, 116 remained in the study and were included in the final analysis. Based on a 1:1 randomization, a collagen sponge saturated with either Saline (1 cc) or Depo-Medrol (40 mg/1 cc) was placed at the annulotomy site on the TLIF level. Follow-up occurred on postoperative days 1, 2, 3, 7, and postoperative months 1, 2, and 3. Lumbar radiculopathy was measured by a modified symptom- and laterality-specific Visual Analog Scale (VAS) regarding the severity of back pain and common radiculopathy symptoms.

RESULTS

The patients who received Depo-Medrol, compared with those who received saline, experienced significantly less back pain on postoperative days 1, 2, 3, and 7 (P<0.05). There was no significant difference in back pain beyond day 7. Radiculopathy-related symptoms such as leg pain, numbness, tingling, stiffness, and weakness tended to be reduced in the steroid group at most time points.

CONCLUSION

This study provides Level 1 evidence that intraoperative application of Depo-Medrol during a TLIF surgery with rh-BMP2 significantly reduces back pain for the first week after TLIF surgery. The use of epidural Depo-Medrol may be a useful adjunct to multimodal analgesia for pain relief in the postoperative period.

Bone Substitute Options for Spine Fusion in Patients With Spine Trauma-Part II: The Role of rhBMP

In Part II, we focus on an important aspect of spine fusion in patients with spine trauma: the pivotal role of recombinant human bone morphogenetic protein-2 (rhBMP-2). Despite the influx of diverse techniques facilitated by technological advancements in spinal surgery, spinal fusion surgery remains widely used globally. The persistent challenge of spinal pseudarthrosis has driven extensive efforts to achieve clinically favorable fusion outcomes, with particular emphasis on the evolution of bone graft substitutes. Part II of this review aims to build upon the foundation laid out in Part I by providing a comprehensive summary of commonly utilized bone graft substitutes for spinal fusion in patients with spinal trauma. Additionally, it will delve into the latest advancements and insights regarding the application of rhBMP-2, offering an updated perspective on its role in enhancing the success of spinal fusion procedures.

Pilot Study on Percutaneous Delivery of Recombinant Human Bone Morphongenetic Protein-2 Augments Fusion in a Nicotine-impaired Rabbit Fusion Model

STUDY DESIGN

A nicotine-impaired spinal fusion rabbit model.

OBJECTIVE

To examine whether controlled delivery of morselized absorbable collagen sponge recombinant human bone morphogenetic protein-2 (rhBMP2) in a delayed manner postsurgery would allow for improved bone healing.

SUMMARY OF BACKGROUND DATA

The current delivery method of rhBMP-2 during surgery causes a burst of rhBMP-2, which is not sustained. Given that bone morphogenetic protein 2 (BMP-2) expression peaks later in the fusion process, there may be the benefit of delivery of rhBMP-2 later in the healing process.

METHODS

Sixteen male 1-year-old rabbits underwent a posterolateral spinal fusion with iliac crest bone graft at L5-L6 while being given nicotine to prevent spinal fusion as previously published. Eight were controls, whereas 8 had morselized rhBMP-2 (4.2 mg) injected at the fusion site at 4 weeks postoperatively. Histologic, radiologic, and palpation examinations were performed at 12 weeks to determine fusion status and the volume of bone formed. Hematoxylin and eosin stains were used for histology. A Student t test was used to compare the computed tomography scan measured volume of bone created between the control cohort (CC) and rhBMP-2 delayed delivery cohort (BMP-DDC).

RESULTS

Of the total, 7/8 rabbits in the BMP-DDC and 5/8 rabbits in the CC formed definitive fusion with a positive palpation examination, bridging bone between transverse processes on computed tomography scan, and an x-ray showing fusion. Histologic analysis revealed newly remodeled bone within the BMP-DDC. There was an increased average volume of bone formed within the BMP-DDC versus the CC (22.6 ± 13.1 vs 11.1 ± 3.6 cm 3 , P = 0.04).

CONCLUSION

Our study shows that injectable morselized absorbable collagen sponge/rhBMP-2 can create twice as much bone within a nicotine-impaired rabbit spine fusion model when delivered 4 weeks out from the time of surgery.

Postoperative Spinal Hematoma and Seroma

Fluid collections after spine surgery are rare complications, although potentially grave, and may be broadly grouped into two major categories. Symptomatic postoperative epidural hematomas have some known risk factors and can present with a widely variable profile of signs and symptoms. Treatment involves emergent surgical evacuation to reduce the risk of permanent neurologic deficit. Postoperative seroma may lead to disruption of wound healing and deep infection and has been associated with the use of recombinant human bone mineral protein. These diagnoses may present diagnostic challenges; thorough understanding of the involved pathophysiology, meticulous clinical evaluation, and radiographic interpretation are critical to appropriate management and optimal outcome.

Usage Trends and Safety Profile of Recombinant Human Bone Morphogenetic Protein-2 for Spinal Column Tumor Surgery: A National Matched Cohort Analysis

STUDY DESIGN

Retrospective Cohort Analysis.

OBJECTIVE

The purpose of this study is to investigate national rates of rhBMP-2 utilization in spinal tumor surgery and examine its association with postoperative complications, revisions, and carcinogenicity.

METHODS

All patients diagnosed with primary or metastatic spinal tumors with subsequent surgical intervention involving a spinal fusion procedure were identified in PearlDiver. Patients were 1:1 matched into 2 cohorts according to rhBMP-2 usage. Postoperative complications and revisions were examined at 1 month, 3 months, 6 months, and 1 year after fusion. New cancer incidence following spinal tumor surgery was assessed until 5 years postoperatively.

RESULTS

A total of 11,198 patients underwent fusion surgery after resection of spinal tumors between 2005 and 2020, with 909 cases reporting the use of rhBMP-2 (8.1%). An annualized analysis revealed that the proportion of spine tumor fusion procedures utilizing rhBMP-2 has been significantly decreasing (R2 = .859, P < .001), with the most recent annual utilization rate at 1.1%. At least 3 months after surgery, significantly increased incidences of surgical site (11.4% vs 3.3%, P = .03) and systemic infections (8.1% vs 1.6%, P = .02) were observed in patients who underwent fusion with rhBMP-2. Across all time points, no significant differences were observed in survival, implant removal, revision rates, or new cancer diagnoses.

CONCLUSION

This analysis demonstrated significantly declining national utilization rates. Spinal tumor cases utilizing rhBMP-2 sustained greater rates of surgical site and systemic infections. rhBMP-2 usage did not significantly reduce the risk of mortality, implant failure, or reoperation.

Lateral lumbar interbody fusion - clinical outcomes, fusion rates and complications with recombinant human bone morphogenetic protein-2

BACKGROUND

The authors report an Australian experience of lateral lumbar interbody fusion (LLIF) with respect to clinical outcomes, fusion rates, and complications, with recombinant human bone morphogenetic protein-2 (rhBMP-2) and other graft materials.

METHODS

Retrospective cohort study of LLIF patients 2011-2021. LLIFs performed lateral decubitus by four experienced surgeons past their learning curve. Graft materials classified rhBMP-2 or non-rhBMP-2. Patient-reported outcomes assessed by VAS, ODI, and SF-12 preoperatively and postoperatively. Fusion rates assessed by CT postoperatively at 6 and 12 months. Complications classified minor or major. Clinical outcomes and complications analysed and compared between rhBMP-2 and non-rhBMP-2 groups.

RESULTS

A cohort of 343 patients underwent 437 levels of LLIF. Mean age 67 ± 11 years (range 29-89) with a female preponderance (65%). Mean BMI 29kg/m2 (18-56). Most common operated levels L3/4 (36%) and L4/5 (35%). VAS, ODI and SF-12 improved significantly from baseline. Total complication rate 15% (53/343) with minor 11% (39/343) and major 4% (14/343). Ten patients returned to OR (2-wound infection, 8-further instrumentation and decompression). Most patients (264, 77%) received rhBMP-2, the remainder a non-rhBMP-2 graft material. No significant differences between groups at baseline. No increase in minor or major complications in the rhBMP-2 group compared to the non-rhBMP-2 group respectively; (10.6% vs 13.9% [p = 0.42], 2.7% vs 8.9% [p < 0.01]). Fusion rates significantly higher in the rhBMP-2 group at 6 and 12 months (63% vs 40%, [p < 0.01], 92% vs 80%, [p < 0.02]).

CONCLUSION

LLIF is a safe and efficacious procedure. rhBMP-2 in LLIF produced earlier and higher fusion rates compared to available non-rhBMP-2 graft substitutes.

The "In-Parallel" Technique for Awake, Bilateral Simultaneous Minimally Invasive Transforaminal Lumbar Interbody Fusion and Multilevel Lumbar Decompression

BACKGROUND

Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) and MIS lumbar decompression have been successfully undertaken in the absence of general anesthesia in well-selected patients. By leveraging spinal anesthesia, surgeons may safely conduct surgeries on one- or two-level lumbar pathology. However, surgeries on more extensive pathology have not yet been described, because of concerns about the duration of efficacy of spinal anesthetic in the awake patient.

OBJECTIVE

To report the use of a novel awake technique for "in parallel," simultaneous lumbar spinal surgery on three-segment pathology.

METHODS

We describe concurrent performance of a dual microscopic, navigated MIS TLIF and MIS two-level decompression, using a combination of liposomal bupivacaine erector spinae block in conjunction with a spinal anesthetic.

RESULTS

We show that a left-sided, two-level MIS tubular microscopic decompression combined with a concurrent right-sided, transfacet MIS TLIF via a tubular microscopic approach was well tolerated in an 87-year-old patient with multilevel lumbar stenosis with a mobile spondylolisthesis.

CONCLUSION

We provide the first description of a dual-surgeon approach for minimally invasive spine surgery. This "in-parallel" technique-reliant on 2, independent spine surgeons-may aid in the performance of surgeries previously considered too extensive, given the time constraints of regional anesthesia and can be successfully applied to patients who otherwise may not be candidates for general anesthesia.

Surgical outcomes between posterior decompression alone and posterior decompression with fusion surgery among patients with Meyerding grade 2 degenerative spondylolisthesis: a multicenter cohort study

Background

Whether lumbar decompression with fusion surgery is effective against Meyerding grade 2 degenerative spondylolisthesis (DS) is unknown. Therefore, the current study aimed to compare the surgical outcomes between posterior decompression alone and posterior decompression with fusion surgery among patients with grade 2 DS with central canal stenosis.

Methods

This retrospective cohort study included prospectively registered patients (n = 3863) who underwent surgery for degenerative lumbar spinal canal stenosis at nine high-volume spine centers from April 2017 to July 2019. Patients with grade 2 DS and central canal stenosis were included in the analysis. Patients with radiculopathy, including foraminal stenosis, degenerative scoliosis, and concomitant anterior spinal fusion, and those with a previous history of lumbar surgery were excluded. The participants were divided into the decompression alone group (group D) and decompression with fusion surgery group (group F). Data about patient-reported outcomes, including Numeric Rating Scale (low back pain, leg pain, leg numbness, and foot numbness), Oswestry Disability Index, EuroQol Five-Dimensional questionnaire, and 12-Item Short-Form Health Survey scores, were obtained preoperatively and 2 years postoperatively.

Results

In total, 2354 (61%) patients, including 42 (1.8%) with grade 2 DS (n = 18 in group D and n = 24 in group F), completed the 2-year follow-up. Group D had a higher proportion of female patients than group F. However, the two groups did not significantly differ in terms of other baseline demographic characteristics. Group D had a significantly shorter surgical time and lower volume of intraoperative blood loss than group F. Postoperative patient-reported outcomes did not significantly differ between the two groups, although the preoperative degree of low back pain was higher in group F than in group D. The slip degree of group D did not worsen during the follow-up period.

Conclusion

The surgical outcomes were similar regardless of the addition of fusion surgery among patients with grade 2 DS. Decompression alone was superior to decompression with fusion surgery as it was associated with a lower volume of intraoperative blood loss and shorter surgical time.

Lumbar spine intervertebral disc gene delivery of BMPs induces anterior spine fusion in lewis rats

Minimally invasive techniques and biological autograft alternatives such as the bone morphogenetic proteins (BMPs) can reduce morbidity associated with spinal fusions. This study was a proof-of-concept for gene-therapy-mediated anterior spine fusion that could be adapted to percutaneous technique for clinical use. Isogeneic bone marrow stromal cells genetically programmed to express b-galactosidase (LACZ, a marker gene), BMP2, BMP7, a mixture of BMP2 and BMP7 infected cells (homodimers, HM), or BMP2/7 heterodimers (HT) were implanted into the discs between lumbar vertebrae 4 and 5 (L4/5) and L5/6 of male Lewis rats. Spine stiffening was monitored at 4, 8 and 12 weeks using noninvasive-induced angular displacement (NIAD) testing. At 12 weeks isolated spines were assessed for fusion and bone formation by palpation, biomechanical testing [four-point bending stiffness, moment to failure in extension, and in vitro angular displacement (IVAD)], faxitron x-rays, microCT, and histology. Progressive loss of NIAD occurred in only the HT group (p < 0.001), and biomechanical tests correlated with the NIAD results. Significant fusion occurred only in the HT group (94% of animals with one or both levels) as assessed by palpation (p < 0.001), which predicted HT bone production assessed by faxitron (p ≤ 0.001) or microCT (p < 0.023). Intervertebral bridging bone was consistently observed only in HT-treated specimens. Induced bone was located anterior and lateral to the disc space, with no bone formation noted within the disc. Percutaneous anterior spine fusions may be possible clinically, but induction of bone inside the disc space remains a challenge.

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a prevalent cause of low back pain. IVDD is characterized by abnormal expression of extracellular matrix components such as collagen and aggrecan. In addition, it results in dysfunctional growth, senescence, and death of intervertebral cells. The biological pathways involved in the development and progression of IVDD are not fully understood. Therefore, a better understanding of the molecular mechanisms underlying IVDD could aid in the development of strategies for prevention and treatment. Autophagy is a cellular process that removes damaged proteins and dysfunctional organelles, and its dysfunction is linked to a variety of diseases, including IVDD and osteoarthritis. In this review, we describe recent research findings on the role of autophagy in IVDD pathogenesis and highlight autophagy-targeting molecules which can be exploited to treat IVDD. Many studies exhibit that autophagy protects against and postpones disc degeneration. Further research is needed to determine whether autophagy is required for cell integrity in intervertebral discs and to establish autophagy as a viable therapeutic target for IVDD.

Long-term posterolateral spinal fusion in rabbits induced by rhBMP6 applied in autologous blood coagulum with synthetic ceramics

Autologous bone graft substitute (ABGS) containing rhBMP6 in autologous blood coagulum (Osteogrow) is a novel therapeutic solution for bone regeneration. This study is aimed to investigate the long-term outcome of ABGS with synthetic ceramics (Osteogrow-C) in rabbit posterolateral spinal fusion (PLF) model. Osteogrow-C implants were implanted bilaterally between rabbit lumbar transverse processes. We compared the outcome following implantation of ABGS with ceramic particles of different chemical composition (TCP and biphasic ceramics containing both TCP and HA) and size (500–1700 µm and 74–420 µm). Outcome was analyzed after 14 and 27 weeks by microCT, histology, and biomechanical analyses. Successful bilateral spinal fusion was observed in all animals at the end of observation period. Chemical composition of ceramic particles has impact on the PLF outcome via resorption of TCP ceramics, while ceramics containing HA were only partially resorbed. Moreover, persistence of ceramic particles subsequently resulted with an increased bone volume in implants with small particles containing high proportion of HA. ABGS (rhBMP6/ABC) with various synthetic ceramic particles promoted spinal fusion in rabbits. This is the first presentation of BMP-mediated ectopic bone formation in rabbit PLF model with radiological, histological, and biomechanical features over a time course of up to 27 weeks.

Hypoxia Preconditioned Serum (HPS) Promotes Osteoblast Proliferation, Migration and Matrix Deposition

Interest in discovering new methods of employing natural growth factor preparations to promote bone fracture healing is becoming increasingly popular in the field of regenerative medicine. In this study, we were able to demonstrate the osteogenic potential of hypoxia preconditioned serum (HPS) on human osteoblasts in vitro. Human osteoblasts were stimulated with two HPS concentrations (10% and 40%) and subsequently analyzed at time points of days 2 and 4. In comparison to controls, a time- and dose-dependent (up to 14.2× higher) proliferation of osteoblasts was observed after 4 days of HPS-40% stimulation with lower lactate dehydrogenase (LDH)-levels detected than controls, indicating the absence of cytotoxic/stress effects of HPS on human osteoblasts. With regards to cell migration, it was found to be significantly faster with HPS-10% application after 72 h in comparison to controls. Further osteogenic response to HPS treatment was evaluated by employing culture supernatant analysis, which exhibited significant upregulation of OPG (Osteoprotegerin) with higher dosage (HPS-10% vs. HPS-40%) and longer duration (2 d vs. 4 d) of HPS stimulation. There was no detection of anti-osteogenic sRANKL (soluble Receptor Activator of NF-κB Ligand) after 4 days of HPS stimulation. In addition, ALP (alkaline phosphatase)-enzyme activity, was found to be upregulated, dose-dependently, after 4 days of HPS-40% application. When assessing ossification through Alizarin-Red staining, HPS dose-dependently achieved greater (up to 2.8× higher) extracellular deposition of calcium-phosphate with HPS-40% in comparison to controls. These findings indicate that HPS holds the potential to accelerate bone regeneration by osteogenic promotion of human osteoblasts.

Engineering biomaterials to 3D-print scaffolds for bone regeneration: practical and theoretical consideration

There are more than 2 million bone grafting procedures performed annually in the US alone. Despite significant efforts, the repair of large segmental bone defects is a substantial clinical challenge which requires bone substitute materials or a bone graft. The available biomaterials lack the adequate mechanical strength to withstand the static and dynamic loads while maintaining sufficient porosity to facilitate cell in-growth and vascularization during bone tissue regeneration. A wide range of advanced biomaterials are being currently designed to mimic the physical as well as the chemical composition of a bone by forming polymer blends, polymer-ceramic and polymer-degradable metal composites. Transforming these novel biomaterials into porous and load-bearing structures via three-dimensional printing (3DP) has emerged as a popular manufacturing technique to develop engineered bone grafts. 3DP has been adopted as a versatile tool to design and develop bone grafts that satisfy porosity and mechanical requirements while having the ability to form grafts of varied shapes and sizes to meet the physiological requirements. In addition to providing surfaces for cell attachment and eventual bone formation, these bone grafts also have to provide physical support during the repair process. Hence, the mechanical competence of the 3D-printed scaffold plays a key role in the success of the implant. In this review, we present various recent strategies that have been utilized to design and develop robust biomaterials that can be deployed for 3D-printing bone substitutes. The article also reviews some of the practical, theoretical and biological considerations adopted in the 3D-structure design and development for bone tissue engineering.

History of Bone Grafts in Spine Surgery

Bone grafting replaces damaged or missing bone with new bone and is used for surgical arthrodesis. Patients benefit from a huge variety of bone graft techniques and options for spinal fusions. This article reviews the rich history of bone grafts in surgery with particular emphasis on spinal fusion. During the early years of bone grafting in spine surgery, bone grafts were used on tuberculosis patients, and the structural support of the graft was most the important consideration. Between 1960 and 2000, many advances were made, specifically in the use of bone graft substitutes. The field of bone grafts in spine surgery has evolved rapidly since first described.

Clinical and Cost-Effectiveness of Lumbar Interbody Fusion Using Tritanium Posterolateral Cage (vs. Propensity-Matched Cohort of PEEK Cage)

Introduction

Surgical management of degenerative lumbar spine disorders is effective at improving patient pain, disability, and quality of life; however, obtaining a durable posterolateral fusion after decompression remains a challenge. Interbody fusion technologies are viable means of improving fusion rates in the lumbar spine, specifically various graft materials including autograft, structural allograft, titanium, and polyether ether ketone. This study assesses the effectiveness of Tritanium posterolateral cage in the treatment of degenerative disk disease.

Methods

Nearest-neighbor 1:1 matched control transforaminal lumbar interbody fusion with PEEK vs. Tritanium posterior lumbar (PL) cage interbody fusion patients were identified using propensity scoring from patients that underwent elective surgery for degenerative disk diseases. Line graphs were generated to compare the trajectories of improvement in patient-reported outcomes (PROs) from baseline to 3 and 12 months postoperatively. The nominal data were compared via the χ² test, while the continuous data were compared via Student's t-test.

Results

The two groups had no difference regarding either the 3- or 12-month Euro-Qol-5D (EQ-5D), numeric rating scale (NRS) leg pain, and NRS back pain; however, the Tritanium interbody cage group had better Oswestry Disability Index (ODI) scores compared to the control group of the PEEK interbody cage at both 3 and 12 months (p=0.013 and 0.048).

Conclusions

Our results indicate the Tritanium cage is an effective alternative to the previously used PEEK cage in terms of PROs, surgical safety, and radiological parameters of surgical success. The Tritanium cohort showed better ODI scores, higher fusion rates, lower subsidence, and lower indirect costs associated with surgical management, when compared to the propensity-matched PEEK cohort.

Top 50 Cited Bone Graft Orthopedic Papers

The purpose of this research is to recognize the highest 50 most-mentioned articles in the literature concentrating on bone grafts. That has been accomplished with the use of the Scopus database and the search slogan "bone grafts," and we inquired for the 50 most-cited articles on bone grafting. The study was completed in September 2020. We investigated the articles issued between 1970 and 2020. The articles were organized and classified based on the total number of citations. We appraised the following information relating to each article: first author, year of publication, journal, and title.

A total of 1,580 studies matched our search standards, of which the 50 most-cited extended between 1,862 and 403 citations. Seven articles were cited more than 1,000 times. The article by Marx et al. was the maximum-cited article, with 1,862 citations, followed by Younger et al.'s with 1,461 and Giannoudis et al.'s with 1,245. The majority of the studies originated from the United States (n = 30) and were published in the 2000s. Biomaterials was the most regular destination journal (n = 8), followed by the Journal of Bone and Joint Surgery American series (n = 7). A maximum of the articles focused on the different types of bone grafts and their alternatives including bone tissue engineering (n=29). Our investigation of the highest 50 articles linking to bone grafting has emphasized the most significant papers in the field. These cover a wide-ranging variety of topics including types, management, and mechanism of action of bone grafts. To recognize the present treatment guidelines and how the use of bone grafting has grown, it is vital to know the most-cited articles relating to this grafting.

A Review of Commercially Available Cellular-based Allografts

STUDY DESIGN

This was a narrative review.

OBJECTIVE

This review discusses our current knowledge regarding cellular-based allografts while highlighting the key gaps in the literature that must be addressed before their widespread adoption.

SUMMARY OF BACKGROUND DATA

Iliac crest bone graft is the gold-standard bone graft material but is associated with donor site morbidity. Commonly utilized bone graft extenders such as demineralized bone matrix and bone morphogenetic protein have conflicting data supporting their efficacy and lack the osteogenic potential of new cellular-based allograft options.

METHODS

An extensive literature review was performed. The literature was then summarized in accordance with the authors' clinical experience.

RESULTS

There is not widespread evidence thus far that the addition of the osteogenic cellular component to allograft enhances spinal fusion, as a recent study by Bhamb and colleagues demonstrated superior bone formation during spine fusion in an aythmic rat model when demineralized bone matrix was used in comparison to Osteocel Plus. Furthermore, the postimplantation cellular viability and osteogenic and osteoinductive capacity of cellular-based allografts need to be definitively established, especially given that a recent study by Lina and colleagues demonstrated a paucity of bone marrow cell survival in an immunocompetent mouse posterolateral spinal fusion model.

CONCLUSIONS

This data indicates that the substantially increased cost of these cellular allografts may not be justified.

LEVEL OF EVIDENCE

Level V.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

Dose Adjustment Associated Complications of Bone Morphogenetic Protein: A Longitudinal Assessment

OBJECTIVE

Bone morphogenetic protein (BMP) is a growth factor that aids in osteoinduction and promotes bone fusion. There is a lack of literature regarding recombinant human BMP-2 (rhBMP-2) dosage in different spine surgeries. This study aims to investigate the trends in rhBMP-2 dosage and the associated complications in spinal arthrodesis.

METHODS

A retrospective study was conducted investigating spinal arthrodesis using rhBMP-2. Variables including age, procedure type, rhBMP-2 size, complications, and postoperative imaging were collected. Cases were grouped into the following surgical procedures: anterior lumbar interbody fusion/extreme lateral interbody fusion (ALIF/XLIF), posterior lumbar interbody fusion/transforaminal lumbar interbody fusion (PLIF/TLIF), posterolateral fusion (PLF), anterior cervical discectomy and fusion (ACDF), and posterior cervical fusion (PCF).

RESULTS

A total of 1209 patients who received rhBMP-2 from 2006 to 2020 were studied. Of these, 230 were categorized as ALIF/XLIF, 336 as PLIF/TLIF, 243 as PLF, 203 as ACDF, and 197 as PCF. PCF (P < 0.001), PLIF/TLIF (P < 0.001), and PLF (P < 0.001) demonstrated a significant decrease in the rhBMP-2 dose used per level, with major transitions seen in 2018, 2011, and 2013, respectively. In our sample, 129 complications following spinal arthrodesis were noted. A significant relation between rhBMP-2 size and complication rates (χ²= 73.73, P = 0.0029) was noted. rhBMP-2 dosage per level was a predictor of complication following spinal arthrodesis (odds ratio = 1.302 [1.05-1.55], P < 0.001).

CONCLUSIONS

BMP is an effective compound in fusing adjacent spine segments. However, it carries some regional complications. We demonstrate a decreasing trend in the dose/vertebral level. A decrease rhBMP-2 dose per level correlated with a decrease in complication rates.

Improved Posterolateral Lumbar Spinal Fusion Using a Biomimetic, Nanocomposite Scaffold Augmented by Autologous Platelet-Rich Plasma

Remodeling of the human bony skeleton is constantly occurring with up to 10% annual bone volume turnover from osteoclastic and osteoblastic activity. A shift toward resorption can result in osteoporosis and pathologic fractures, while a shift toward deposition is required after traumatic, or surgical injury. Spinal fusion represents one such state, requiring a substantial regenerative response to immobilize adjacent vertebrae through bony union. Autologous bone grafts were used extensively prior to the advent of advanced therapeutics incorporating exogenous growth factors and biomaterials. Besides cost constraints, these applications have demonstrated patient safety concerns. This study evaluated the regenerative ability of a nanostructured, magnesium-doped, hydroxyapatite/type I collagen scaffold (MHA/Coll) augmented by autologous platelet-rich plasma (PRP) in an orthotopic model of posterolateral lumbar spinal fusion. After bilateral decortication, rabbits received either the scaffold alone (Group 1) or scaffold with PRP (Group 2) to the anatomic right side. Bone regeneration and fusion success compared to internal control were assessed by DynaCT with 3-D reconstruction at 2, 4, and 6 weeks postoperatively followed by comparative osteogenic gene expression and representative histopathology. Both groups formed significantly more new bone volume than control, and Group 2 subjects produced significantly more trabecular and cortical bone than Group 1 subjects. Successful fusion was seen in one Group 1 animal (12.5%) and 6/8 Group 2 animals (75%). This enhanced effect by autologous PRP treatment appears to occur via astounding upregulation of key osteogenic genes. Both groups demonstrated significant gene upregulation compared to vertebral bone controls for all genes. Group 1 averaged 2.21-fold upregulation of RUNX2 gene, 3.20-fold upregulation of SPARC gene, and 3.67-fold upregulation of SPP1 gene. Depending on anatomical subgroup (cranial, mid, caudal scaffold portions), Group 2 had significantly higher average expression of all genes than both control and Group 1–RUNX2 (8.23–19.74 fold), SPARC (18.67–55.44 fold), and SPP1 (46.09–90.65 fold). Our data collectively demonstrate the osteoinductive nature of a nanostructured MHA/Coll scaffold, a beneficial effect of augmentation with autologous PRP, and an ability to achieve clinical fusion when applied together in an orthotopic model. This has implications both for future study and biomedical innovation of bone-forming therapeutics.

Optimal intermittent administration interval of parathyroid hormone 1-34 for bone morphogenetic protein-induced bone formation in a rat spinal fusion model

INTRODUCTION

Both bone morphogenetic protein 2 (BMP-2) and teriparatide (parathyroid hormone [PTH] 1-34) are used to enhance bone healing. There is still no established opinion regarding the optimum dose and administration method. We investigated the optimal administration method for the combination of BMP-2 and PTH 1-34 in a rat spinal fusion model.

METHODS

Group I was implanted with a control carrier. Groups II, III, and IV were implanted with a carrier containing 3 μg of recombinant human BMP-2 (rhBMP-2). In addition, following implantation, PTH 1-34 injections were administered to Group III thrice a week (total, 180 μg/kg/week) and Group IV six times a week (total, 180 μg/kg/week). The rats were euthanized after 8 weeks, and their spines were explanted; assessed by manual palpation, radiographs, and high-resolution micro-computed tomography (micro-CT); and subjected to histological analysis. Serum markers of bone metabolism were also analyzed.

RESULTS

Manual palpation tests showed that the fusion rates in Groups III and IV were considerably higher than those in Group I. They also had higher radiographic scores than Group I and II. Micro-CT analysis revealed Tb.Th in the Group IV had higher values than that in the Group I, II, III with significant differences and Tb.Sp in the Group IV had lower values than that in the Group I, II, III with significant differences. Serum marker analysis revealed that Group IV had higher osteocalcin and lower tartrate-resistant acid phosphatase-5b than Group III. Histological analysis indicated that Group IV had enhanced trabecular bone structure.

CONCLUSIONS

Frequent administration of PTH may be better in making thicker and strengthening the trabecular bone structure in newly formed bone in the rat spinal fusion model using insufficient BMP-2.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

Osteobiologics

BACKGROUND

Osteobiologics are engineered materials that facilitate bone healing and have been increasingly used in spine surgery. Autologous iliac crest bone grafts have been used historically, but morbidity associated with graft harvesting has led surgeons to seek alternative solutions. Allograft bone, biomaterial scaffolds, growth factors, and stem cells have been explored as bone graft substitutes and supplements.

OBJECTIVE

To review current and emerging osteobiologic technologies.

METHODS

A literature review of English-language studies was performed in PubMed. Search terms included combinations of "spine," "fusion," "osteobiologics," "autologous," "allogen(e)ic," "graft," "scaffold," "bone morphogenic protein," and "stem cells."

RESULTS

Evidence supports allograft bone as an autologous bone supplement or replacement in scenarios where minimal autologous bone is available. There are promising data on ceramics and P-15; however, comparative human trials remain scarce. Growth factors, including recombinant human bone morphogenic proteins (rhBMPs) 2 and 7, have been explored in humans after successful animal trials. Evidence continues to support the use of rhBMP-2 in lumbar fusion in patient populations with poor bone quality or revision surgery, while there is limited evidence for rhBMP-7. Stem cells have been incredibly promising in promoting fusion in animal models, but human trials to this point have only involved products with questionable stem cell content, thereby limiting possible conclusions.

CONCLUSION

Engineered stem cells that overexpress osteoinductive factors are likely the future of spine fusion, but issues with applying viral vector-transduced stem cells in humans have limited progress.

Use of rhBMP-2 for adult spinal deformity surgery: patterns of usage and changes over the past decade

OBJECTIVE

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been shown to increase fusion rates; however, cost, limited FDA approval, and possible complications impact its use. Decisions regarding rhBMP-2 use and changes over time have not been well defined. In this study, the authors aimed to assess changes in rhBMP-2 use for adult spinal deformity (ASD) surgery over the past decade.

METHODS

A retrospective review of the International Spine Study Group prospective multicenter database was performed to identify ASD patients treated surgically from 2008 to 2018. For assessment of rhBMP-2 use over time, 3 periods were created: 2008-2011, 2012-2015, and 2016-2018.

RESULTS

Of the patients identified, 1180 met inclusion criteria, with a mean age 60 years and 30% of patients requiring revision surgery; rhBMP-2 was used in 73.9% of patients overall. The mean rhBMP-2 dose per patient was 23.6 mg. Patients receiving rhBMP-2 were older (61 vs 58 years, p < 0.001) and had more comorbidities (Charlson Comorbidity Index 1.9 vs 1.4, p < 0.001), a higher rate of the Scoliosis Research Society-Schwab pelvic tilt modifier (> 0; 68% vs 62%, p = 0.026), a greater deformity correction (change in pelvic incidence minus lumbar lordosis 15° vs 12°, p = 0.01), and more levels fused (8.9 vs 7.9, p = 0.003). Over the 3 time periods, the overall rate of rhBMP-2 use increased and then stabilized (62.5% vs 79% vs 77%). Stratified analysis showed that after an overall increase in rhBMP-2 use, only patients who were younger than 50 years, those who were smokers, those who received a three-column osteotomy (3CO), and patients who underwent revision sustained an increased rate of rhBMP-2 use between the later two periods. No similar increases were noted for older patients, nonsmokers, primary surgery patients, and patients without a 3CO. The total rhBMP-2 dose decreased over time (26.6 mg vs 24.8 mg vs 20.7 mg, p < 0.001). After matching patients by preoperative alignment, 215 patients were included, and a significantly lower rate of complications leading to revision surgery was observed within the 2012-2015 period compared with the 2008-2011 (21.4% vs 13.0%, p = 0.029) period, while rhBMP-2 was increasingly used (80.5% vs 66.0%, p = 0.001). There was a trend toward a lower rate of pseudarthrosis for patients in the 2012-2015 period, but this difference did not reach statistical significance (7% vs 4.2%, p = 0.283).

CONCLUSIONS

The authors found that rhBMP-2 was used in the majority of ASD patients and was more commonly used in those with greater deformity correction. Additionally, over the last 10 years, rhBMP-2 was increasingly used for ASD patients, but the dose has decreased.

Early Fusion Rates After Direct Lateral Lumbar Interbody Fusion With Bone-Morphogenetic Protein

BACKGROUND

Direct lateral (transpsoas) lumbar interbody fusion (LLIF) reportedly achieves union by 1 year postoperatively, but how soon fusion occurs after these minimally invasive procedures is unclear. This study investigated LLIF fusion progression at 6 months and 1 year in a large-scale cohort using bone morphogenetic protein (BMP) graft and examined risk factors associated with failed fusion.

METHODS

Patients undergoing primary LLIF with a single surgical team from 2015 through 2016 with polyetheretherketone (PEEK) iimplants and BMP graft were identified. Retrospective chart review included demographics and medical history, construct length and location, and concurrent L5-S1 fusion. Inclusion criteria included minimum 1-year follow-up and postoperative lumbar computed tomography at 6 months and 1 year, which was independently assessed for bony union at each level.

RESULTS

166 patients underwent LLIF at a total of 312 levels. Seventy-nine patients (48%) underwent 1-level fusion; 45 (27%), 2 levels; and 42 (25%), 3 or more levels. At 6 months, 160 (51%) levels showed fusion. At 1 year, 70% of the remainder were fused, and total fusion rate was 85%. Fusion rates from L1 through L4 were similar (84%-87%). Nonunion was not significantly associated with construct length (P = .19), concurrent anterior L5-S1 interbody fusion (P = .50), age (P = .70), BMI (P = .15), or comorbidities such as diabetes (P = .86) or thyroid disease (P = .46).

CONCLUSIONS

This large retrospective cohort study corroborates prior 1-year LLIF fusion rate reports (85%) independent of construct length or location or medical comorbidities. Significantly, half showed fusion by 6 months, earlier than previously described and validating the efficacy of LLIF.

LEVEL OF EVIDENCE

5.

CLINICAL RELEVANCE

This study presents a large cohort of patients to support effective lumbar fusion after LLIF with BMP-2.

3D-printed scaffold combined to 2D osteoinductive coatings to repair a critical-size mandibular bone defect

The reconstruction of large bone defects (12 cm³) remains a challenge for clinicians. We developed a new critical-size mandibular bone defect model on a minipig, close to human clinical issues. We analyzed the bone reconstruction obtained by a 3D-printed scaffold made of clinical-grade polylactic acid (PLA), coated with a polyelectrolyte film delivering an osteogenic bioactive molecule (BMP-2). We compared the results (computed tomography scans, microcomputed tomography scans, histology) to the gold standard solution, bone autograft. We demonstrated that the dose of BMP-2 delivered from the scaffold significantly influenced the amount of regenerated bone and the repair kinetics, with a clear BMP-2 dose-dependence. Bone was homogeneously formed inside the scaffold without ectopic bone formation. The bone repair was as good as for the bone autograft. The BMP-2 doses applied in our study were reduced 20- to 75-fold compared to the commercial collagen sponges used in the current clinical applications, without any adverse effects. Three-dimensional printed PLA scaffolds loaded with reduced doses of BMP-2 may be a safe and simple solution for large bone defects faced in the clinic.

Local insulin application has a dose-dependent effect on lumbar fusion in a rabbit model

The purpose of this study was to determine if locally applied insulin has a dose-responsive effect on posterolateral lumbar fusion. Adult male New Zealand White rabbits underwent posterolateral intertransverse spinal fusions (PLFs) at L5-L6 using suboptimal amounts of autograft. Fusion sites were treated with collagen sponge soaked in saline (control, n = 11), or with insulin at low (5 or 10 units, n = 13), mid (20 units, n = 11), and high (40 units, n = 11) doses. Rabbits were euthanized at 6 weeks. The L5-L6 spine segment underwent manual palpation and radiographic evaluation performed by two fellowship trained spine surgeons blinded to treatment. Differences between groups were evaluated by analysis of variance on ranks followed by post-hoc Dunn's tests. Forty-three rabbits were euthanized at the planned 6 weeks endpoint, while three died or were euthanized prior to the endpoint. Radiographic evaluation found bilateral solid fusion in 10%, 31%, 60%, and 60% of the rabbits from the control and low, mid, and high-dose insulin-treated groups, respectively (p < 0.05). As per manual palpation, 7 of 10 rabbits in the mid-dose insulin group were fused as compared to 1 of 10 rabbits in the control group (p < 0.05). This study demonstrates that insulin enhanced the effectiveness of autograft to increase fusion success in the rabbit PLF model. The study indicates that insulin or insulin-mimetic compounds can be used to promote bone regeneration.

A Prospective, Multi-Center, Double-Blind, Randomized Study to Evaluate the Efficacy and Safety of the Synthetic Bone Graft Material DBM Gel with rhBMP-2 versus DBM Gel Used during the TLIF Procedure in Patients with Lumbar Disc Disease

Objective

This study is to evaluate the efficacy and safety of demineralized bone matrix (DBM) gel versus DBM gel with recombinant human bone morphogenetic protein-2 (rhBMP-2) used in transforaminal lumbar interbody fusion (TLIF).

Methods

This study was designed as a prospective, multi-center, double-blind method, randomized study. All randomized subjects underwent TLIF with DBM gel with rhBMP-2 group (40 patients) as an experimental group or DBM gel group (36 patients) as a control group. Post-operative observations were performed at 12, 24, and 48 weeks. The spinal fusion rate on computed tomography scans and X-rays films, Visual analog scale pain scores, Oswestry disability index and SF-36 quality of life (QOL) scores were used for the efficacy evaluation. The incidence rate of adverse device effects (ADEs) and serious adverse device effects (SADEs) were used for safety evaluation.

Results

The spinal fusion rate at 12 weeks for the DBM gel with rhBMP-2 group was higher with 73.68% compared to 58.82% for the DBM gel group. The 24 and 48 weeks were 72.22% and 82.86% for the DBM gel with rhBMP-2 group and 78.79% and 78.13%, respectively, for the DBM gel group. However, there were no significant differences between two groups in the spinal fusion rate at 12, 24, and 48 weeks post-treatment (p=0.1817, p=0.5272, p=0.6247). There was no significant difference between the two groups in the incidence rate of ADEs (p=0.3836). For ADEs in the experimental group, ‘Pyrexia’ (5.00%) was the most common ADE, followed by ‘Hypesthesia’, ‘Paresthesia’, ‘Transient peripheral paralysis’, ‘Spondylitis’ and ‘Insomnia’ (2.50%, respectively). ADEs reported in control group included ‘Pyrexia’, ‘Chest discomfort’, ‘Pain’, ‘Osteoarthritis’, ‘Nephropathy toxic’, ‘Neurogenic bladder’, ‘Liver function analyses’ and ‘Urticaria’ (2.86%, respectively). There was no significant difference between the two groups in the incidence rate of SADEs (p=0.6594). For SADE in the experimental group, ‘‘Pyrexia’ and ‘Spondylitis’ were 2.50%. SADE reported in the control group included 'Chest discomfort’, ‘Osteoarthritis’ and ‘Neurogenic bladder’. All SADEs described above were resolved after medical treatment.

Conclusion

This study demonstrated that the spinal fusion rates of DBM gel group and DBM gel with rhBMP-2 group were not significantly different. But, this study provides knowledge regarding the earlier postoperative effect of rhBMP-2 containing DBM gel and also supports the idea that the longer term follow-up results are essential to confirm the safety and effectiveness.

Bone morphogenetic protein-2 against iliac crest bone graft for the posterolateral fusion of the lumbar spine: A meta-analysis

BACKGROUND

The impact of bone morphogenetic protein-2 compared to autologous iliac crest bone graft to improve fusion rates for the posterolateral fusion of the lumbar spine remains inconclusive. This meta-analysis was performed to evaluate this relationship.

METHODS

A systematic literature search up to May 2020 was performed and 14 studies were detected with 1516 subjects with 789 of them were bone morphogenetic protein-2 and 727 of them were autologous iliac crest bone graft. They reported relationships between bone morphogenetic protein-2 and autologous iliac crest bone graft on fusion rates for the posterolateral fusion of the lumbar spine. Odds ratio (OR) with 95% confidence intervals (CIs) was calculated comparing the bone morphogenetic protein-2 or autologous iliac crest bone graft on the posterolateral fusion of the lumbar spine risks using the dichotomous and continuous method with a random- or fixed-effect model.

RESULTS

Bone morphogenetic protein-2 had significantly higher fusion rates (OR, 4.19; 95% CI, 2.82-6.20, P < .001); lower surgery time (OR, -26.64; 95% CI, -38.71 to -14.57, P < .001); lower blood loss (OR, -92.84; 95% CI, -131.71 to -53.97, P < .001); lower additional surgical procedures (OR, 0.46; 95% CI, 0.31-0.69, P < .001) and higher Oswestry Disability Index (OR, 1.49; 95% CI, 0.02-2.97, P = .05) compared to autologous iliac crest bone graft. However, no significant difference was found between bone morphogenetic protein-2 and autologous iliac crest bone graft in non-union rates (OR, 0.34; 95% CI, 0.08-1.53, P < .001); hospitalisation days (OR, -0.21; 95% CI, -0.48 to 0.07, P = .14) and adverse events (OR, 0.78; 95% CI, 0.52-1.16, P = .22).

CONCLUSIONS

Bone morphogenetic protein-2 significantly had a higher fusion rate, lower surgery time, lower blood loss, lower additional surgical procedures and higher Oswestry Disability Index compared to autologous iliac crest bone graft. This relationship forces us to recommend bone morphogenetic protein-2 for the posterolateral fusion of the lumbar spine to avoid any possible negative postoperative results.

Bone Matrix Non-Collagenous Proteins in Tissue Engineering: Creating New Bone by Mimicking the Extracellular Matrix

Engineering biomaterials that mimic the extracellular matrix (ECM) of bone is of significant importance since most of the outstanding properties of the bone are due to matrix constitution. Bone ECM is composed of a mineral part comprising hydroxyapatite and of an organic part of primarily collagen with the rest consisting on non-collagenous proteins. Collagen has already been described as critical for bone tissue regeneration; however, little is known about the potential effect of non-collagenous proteins on osteogenic differentiation, even though these proteins were identified some decades ago. Aiming to engineer new bone tissue, peptide-incorporated biomimetic materials have been developed, presenting improved biomaterial performance. These promising results led to ongoing research focused on incorporating non-collagenous proteins from bone matrix to enhance the properties of the scaffolds namely in what concerns cell migration, proliferation, and differentiation, with the ultimate goal of designing novel strategies that mimic the native bone ECM for bone tissue engineering applications. Overall, this review will provide an overview of the several non-collagenous proteins present in bone ECM, their functionality and their recent applications in the bone tissue (including dental) engineering field.

Neural crest-derived mesenchymal progenitor cells enhance cranial allograft integration

Replacement of lost cranial bone (partly mesodermal and partly neural crest‐derived) is challenging and includes the use of nonviable allografts. To revitalize allografts, bone marrow‐derived mesenchymal stromal cells (mesoderm‐derived BM‐MSCs) have been used with limited success. We hypothesize that coating of allografts with induced neural crest cell‐mesenchymal progenitor cells (iNCC‐MPCs) improves implant‐to‐bone integration in mouse cranial defects. Human induced pluripotent stem cells were reprogramed from dermal fibroblasts, differentiated to iNCCs and then to iNCC‐MPCs. BM‐MSCs were used as reference. Cells were labeled with luciferase (Luc2) and characterized for MSC consensus markers expression, differentiation, and risk of cellular transformation. A calvarial defect was created in non‐obese diabetic/severe combined immunodeficiency (NOD/SCID) mice and allografts were implanted, with or without cell coating. Bioluminescence imaging (BLI), microcomputed tomography (μCT), histology, immunofluorescence, and biomechanical tests were performed. Characterization of iNCC‐MPC‐Luc2 vs BM‐MSC‐Luc2 showed no difference in MSC markers expression and differentiation in vitro. In vivo, BLI indicated survival of both cell types for at least 8 weeks. At week 8, μCT analysis showed enhanced structural parameters in the iNCC‐MPC‐Luc2 group and increased bone volume in the BM‐MSC‐Luc2 group compared to controls. Histology demonstrated improved integration of iNCC‐MPC‐Luc2 allografts compared to BM‐MSC‐Luc2 group and controls. Human osteocalcin and collagen type 1 were detected at the allograft‐host interphase in cell‐seeded groups. The iNCC‐MPC‐Luc2 group also demonstrated improved biomechanical properties compared to BM‐MSC‐Luc2 implants and cell‐free controls. Our results show an improved integration of iNCC‐MPC‐Luc2‐coated allografts compared to BM‐MSC‐Luc2 and controls, suggesting the use of iNCC‐MPCs as potential cell source for cranial bone repair.

Growth Factors, Carrier Materials, and Bone Repair

This chapter provides an overview of the growth factors active in bone regeneration and healing. Both normal and impaired bone healing are discussed, with a focus on the spatiotemporal activity of the various growth factors known to be involved in the healing response. The review highlights the activities of most important growth factors impacting bone regeneration, with a particular emphasis on those being pursued for clinical translation or which have already been marketed as components of bone regenerative materials. Current approaches the use of bone grafts in clinical settings of bone repair (including bone grafts) are summarized, and carrier systems (scaffolds) for bone tissue engineering via localized growth factor delivery are reviewed. The chapter concludes with a consideration of how bone repair might be improved in the future.

Supramolecular self-assembling peptides to deliver bone morphogenetic proteins for skeletal regeneration

Recombinant human bone morphogenetic proteins (BMPs) have shown clinical success in promoting bone healing, but they are also associated with unwanted side effects. The development of improved BMP carriers that can retain BMP at the defect site and maximize its efficacy would decrease the therapeutic BMP dose and thus improve its safety profile. In this review, we discuss the advantages of using self-assembling peptides, a class of synthetic supramolecular biomaterials, to deliver recombinant BMPs. Peptide amphiphiles (PAs) are a broad class of self-assembling peptides, and the use of PAs for BMP delivery and bone regeneration has been explored extensively over the past decade. Like many self-assembling peptide systems, PAs can be designed to form nanofibrous supramolecular biomaterials in which molecules are held together by non-covalent bonds. Chemical and biological functionality can be added to PA nanofibers, through conjugation of chemical moieties or biological epitopes to PA molecules. For example, PA nanofibers have been designed to bind heparan sulfate, a natural polysaccharide that is known to bind BMPs and potentiate their signal. Alternatively, PA nanofibers have been designed to synthetically mimic the structure and function of heparan sulfate, or to directly bind BMP specifically. In small animal models, these bio-inspired PA materials have shown the capacity to promote bone regeneration using BMP at doses 10-100 times lower than established therapeutic doses. These promising results have motivated further evaluation of PAs in large animal models, where their safety and efficacy must be established before clinical translation. We conclude with a discussion on the possiblity of combining PAs with other materials used in orthopaedic surgery to maximize their utility for clinical translation.

Autologous bone graft substitute containing rhBMP6 within autologous blood coagulum and synthetic ceramics of different particle size determines the quantity and structural pattern of bone formed in a rat subcutaneous assay

Bone morphogenetic proteins (BMPs) are potent osteoinductive agents for bone tissue engineering. In order to define optimal properties of a novel autologous bone graft substitute (ABGS) containing rhBMP6 within the autologous blood coagulum (ABC) and ceramic particles as a compression resistant matrix (CRM), we explored the influence of their amount, chemical composition and particle size on the quantity and quality of bone formation in the rat subcutaneous assay. Tested ceramic particles included tricalcium phosphate (TCP), hydroxyapatite (HA) and biphasic calcium phosphate ceramic (BCP), containing TCP and HA in 80/20 ratio of different particle sizes (small 74-420 μm, medium 500-1700 μm and large 1000-4000 μm). RhBMP6 was either mixed with ABC or lyophilized on CRM prior to use with ABC. The experiments were terminated on day 21 and implants were analysed by microCT, histology and histomorphometry. Addition of CRM to ABGS containing rhBMP6 in ABC significantly increased the amount of newly formed bone and the optimal CRM/ABC ratio was found to be around 100 mg/500 μL. MicroCT analyses revealed that all tested ABGS formulations induced an extensive new bone formation and there were no differences between the two methods of rhBMP6 application as determined by the bone volume. However, the particle size played a significant role in the quantity and quality of newly formed bone. ABGS containing small particles induced new bone forming a dense trabecular network, cortical bone at the rim, bone and bone marrow in apposition to and in between ceramic particles. ABGS containing medium and large particles also resulted in new bone on the surface of particles as well as inside the pores. Histomorphometric analysis revealed that the ceramics particle size correlated with the quality of trabecular pattern of newly formed bone, bone/bone marrow ratio as observed in apposition and between particles, and the ratio between the cortical and trabecular bone. By employing rat subcutaneous implant assay, we showed for the first time that the size of synthetic ceramics particles affected the osteogenesis as defined by both the quantity and quality of ectopic bone.

Complications, Costs, and Quality Outcomes of Patients Undergoing Cervical Deformity Surgery With Intraoperative BMP Use

STUDY DESIGN

An epidemiological study using national administrative data from the MarketScan database.

OBJECTIVE

The aim of this study was to identify the impact of bone morphogenetic protein (BMP) on postoperative outcomes in patients undergoing adult cervical deformity (ACD) surgery.

SUMMARY OF BACKGROUND DATA

BMP has been shown to stimulate bone growth and improve fusion rates in spine surgery. However, the impact of BMP on reoperation rates and postoperative complication rate is controversial.

METHODS

We queried the MarketScan database to identify patients who underwent ACD surgery from 2007 to 2015. Patients were stratified by BMP use in the index operation. Patients <18 years and those with any history of tumor or trauma were excluded. Baseline demographics and comorbidities, postoperative complication rates, and reoperation rates were analyzed.

RESULTS

A total of 13,549 patients underwent primary ACD surgery, of which 1155 (8.5%) had intraoperative BMP use. The overall 90-day complication rate was 27.6% in the non-BMP cohort and 31.1% in the BMP cohort (P < 0.05). Patients in the BMP cohort had longer average length of stay (4.0 days vs. 3.7 days, P < 0.05) but lower revision surgery rates at 90 days (14.5% vs. 28.3%, P < 0.05), 6 months (14.9% vs. 28.6%, P < 0.05), 1 year (15.7% vs. 29.2%, P < 0.05), and 2 years (16.5% vs. 29.9%, P < 0.05) postoperatively. BMP use was associated with higher payments throughout the 2-year follow-up period ($107,975 vs. $97,620, P < 0.05). When controlling for baseline group differences, BMP use independently increased the odds of postoperative complication (odds ratio [OR] 1.22, 95% confidence interval [CI] 1.1-1.4) and reduced the odds of reoperation throughout 2 years of follow-up (OR 0.49, 95% CI 0.4-0.6).

CONCLUSION

Intraoperative BMP use has benefits for fusion integrity in ACD surgery but is associated with increased postoperative complication rate. Spine surgeons should weigh these benefits and drawbacks to identify optimal candidates for BMP use in ACD surgery.

LEVEL OF EVIDENCE

3.

Characteristics of Reported Industry Payments to Neurosurgeons: A 5-Year Open Payments Database Study

OBJECTIVE

The aim of this study was to characterize the payments made by medical industry to neurosurgeons from 2014 to 2018.

METHODS

A retrospective study was performed from January 1, 2014 to December 31, 2018 of the Open Payments Database. Collected data included the total number of industry payments, the aggregate value of industry payments, and the mean value of each industry payment made to neurosurgeons per year over the 5-year period.

RESULTS

A total of 105,150 unique surgeons, with 13,668 (12.99%) unique neurosurgeons, were identified to have received an industry payment during 2014-2018. Neurosurgeons were the second highest industry-paid surgical specialty, with a total 421,151 industry payments made to neurosurgeons, totaling $477,451,070. The mean average paid amount per surgeon was $34,932 (±$936,942). The largest proportion of payments were related to food and beverage (75.5%), followed by travel and lodging (14.9%), consulting fees (3.5%), nonconsulting service fees (2.1%), and royalties or licensing (1.9%), totaling 90.4% of all industry payments to neurologic surgeons. Summed across the 5-year period, the largest paid source types were royalties and licensing (64.0%; $305,517,489), consulting fees (11.8%; $56,445,950), nonconsulting service fees (7.3%; $34,629,109), current or prospective investments (6.8%, $32,307,959), and travel and lodging (4.8%, $22,982,165).

CONCLUSIONS

Our study shows that over the most recent 5-year period (2014-2018) of the Centers for Medicare and Medicaid Services Open Payments Database, there was a decreasing trend of the total number of payments, but an increasing trend of the total amount paid to neurosurgeons.

Minimally Invasive Lumbar Decompression and Removal of Symptomatic Heterotopic Bone Formation After Spinal Fusion with Recombinant Human Bone Morphogenetic Protein-2

We present a case of symptomatic heterotopic bone formation following revision of posterolateral lumbar fusion/instrumentation and "off-label" use of recombinant human bone morphogenetic protein-2, treated successfully with the use of a minimally invasive tubular approach.

The minimally effective dose of bone morphogenetic protein in posterior lumbar interbody fusion: a systematic review and meta-analysis

BACKGROUND CONTENT

The risks and benefits of recombinant human bone morphogenetic protein-2 (BMP) in posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) have been widely reported. However, the BMP dose associated with such reports varied widely. Additionally, data on the location of BMP placement on complications and fusion are lacking.

PURPOSE

To determine the minimally effective dose (MED) of BMP which results in optimal fusion rates while minimizing complications; to determine the effects of the location of BMP placement has on fusion rates and complications.

STUDY DESIGN

Systematic review and meta-analysis.

STUDY SAMPLE

Adult patients undergoing PLIF/TLIF for degenerative indications.

OUTCOME MEASURES

Rates of radiculitis, fusion, osteolysis, heterotopic bone formation, and new cancer diagnosis.

METHODS

PubMed, Embase, and Cochrane Database were used to identify studies published between January 1, 2011 and April 30, 2019 reporting BMP usage in adult patients who underwent PLIF/TLIF degenerative indications. A qualitative and quantitative synthesis was performed to evaluate the MED of BMP and the effect of location of BMP placement on fusion and complications. Complications were defined as osteolysis, heterotopic bone growth, radiculitis, and rate of new cancer diagnosis. Complications and fusion outcomes were each pooled according to commercially available BMP doses. Additionally, complications and fusion outcomes were pooled according to 4 location groups (interbody cage only, interbody cage + posterolateral gutter [PLG], cage + interspace, and interspace + PLG). Heterogeneity was assessed with Q and I² statistics.

RESULTS

Twenty-two articles, totaling 2,729 patients were included. Sixteen studies reported fusion and 15 reported complications. Among fusion studies, the mean BMP/level ranged from 1.28 to 12 mg/level. Among complication studies, the mean BMP/level ranged from 6.7 to 23.6 mg/level. The pooled overall fusion rate was 94.0% (91.4-95.8 confidence intervals). There was no significant difference in fusion and complication rates between different BMP doses. Thirteen studies included data on the location of BMP placement with 1,823 patients. At each BMP location, the fusion rate was not significantly different across the dose ranges (1.28-12 mg/level). We found the fusion rate to be marginally higher in the interspace + PLG group compared to the other groups. When BMP was placed in the interbody cage there was a mild increase in the rate of osteolysis compared to other placement locations.

CONCLUSIONS

Fusion and complication rates did not differ significantly between different doses of BMP with the lowest MED for fusion as low as 1.28 mg/level. The location of BMP placement does not significantly affect fusion or complication rates.

Application of BMP-Bone Cement and FGF-Gel on Periodontal Tissue Regeneration in Nonhuman Primates

The ultimate challenge of tissue engineering research is the translation of experimental knowledge into clinical application. In the preclinical testing phase of any new therapy, animal models remain the gold standard. Therefore, the methodological choice of a suitable model is critical to meet the requirements for a safe clinical application of the developed treatment. For instance, we have shown in rats that the application of calcium phosphate cement (CPC)/propylene glycol alginate (PGA) with bone morphogenetic protein (BMP)-2 or fibroblast growth factor (FGF)-2 resulted in the regeneration of periodontal defects. However, it is debated whether using small models form a predictive method for translation to larger species. At the same time, the 3R framework is encouraged as guiding principles of the ethical use of animal testing. Therefore, based on the successful rat study, the objective of this study was to further investigate the periodontal regenerative efficacy of the CPC/BMP and PGA/FGF system in a periodontal defect model with a low number of nonhuman primates (NHPs). Three Macaca fascicularis-overstocked from breeding for other purposes-were used (reuse of animals and appropriateness of the experimental animal species according to 3R framework). Three-wall periodontal defects were surgically created in the mandible. In total, 10 defects were created and distributed over two groups: (1) control group: PGA+CPC (n = 5) and (2) experimental group: PGA/FGF+CPC/BMP (n = 5). After 3 months, tissue regeneration was evaluated by histomorphometry and radiographic measurements. Data showed that epithelial downgrowth, cementum, and ligament regeneration were significantly enhanced in the experimental group compared with the control group (n = 5; p = 0.013, p = 0.028, and p = 0.018, respectively). However, the amount of newly formed bone did not differ (p = 0.146). Overall, as a translational proof-of-principle study, the hybrid periodontal regenerative method of CPC/BMP+PGA/FGF promoted periodontal regeneration in NHPs. This study warrants the application of CPC/BMP/PGA/FGF in clinical trials. Impact Statement This study validated an earlier successful periodontal regeneration strategy from a rat model into a few spare nonhuman primates (NHPs). The hybrid periodontal regenerative method of calcium phosphate cement (CPC)/bone morphogenetic protein (BMP)-2/propylene glycol alginate (PGA)/fibroblast growth factor (FGF)-2 promoted periodontal regeneration in NHPs, which corroborated the previous rat results. This translational approach was a very practical option and thus reduced the number and species of experimental animals in translational research. These results found in NHPs indicate a consistent conclusion with the earlier findings in the rat model. It further warrants the application of CPC/BMP-2+PGA/FGF-2 in human clinical trials.

Comparative Clinical Effectiveness and Safety of Bone Morphogenetic Protein Versus Autologous Iliac Crest Bone Graft in Lumbar Fusion: A Meta-analysis and Systematic Review

STUDY DESIGN

This is a systematic literature review and meta-analysis.

OBJECTIVE

We aimed to evaluate the efficacy and safety of recombinant human bone morphogenetic protein (RhBMP) and autologous iliac crest bone graft (ICBG) in lumbar fusion.

SUMMARY OF BACKGROUND DATA

RhBMP has been emphasized in lumbar fusion due to high fusion success rate. However, ICBG remains the criterion standard graft approach for lumbar fusion. The safety and effectiveness of rhBMP are controversial.

METHODS

Prospective randomized controlled trials were searched from PubMed, EMBASE, and Cochrane Central Register of Controlled Trails by using Medical Subject Headings terms "bone morphogenetic protein,' "bone transplantation,' and "spinal fusion.' Two independent investigators screened eligible studies, assessed the bias of original articles, extracted data including fusion success, Oswestry disability index improvement, improved short form 36 questionnaire scores, adverse events and re-operation, and a subgroup analysis. The GRADE approach was used to grade quality of evidence.

RESULTS

Twenty randomized controlled trials (2185 patients) met the inclusion criteria. There were higher fusion success rate (odds ratio [OR] 3.79, 95% confidence interval [CI] 1.88-7.63, P = 0.0002), better improvement of Oswestry Disability Index (mean difference 1.54, 95% CI 0.18-2.89, P = 0.03), and lower re-operation rate (OR 0.59, 95% CI 0.43-0.80, P = 0.0007) in rhBMP group. Heterogeneity was obvious in fusion success rate (I = 58%); hence, a subgroup analysis, based on protein type (rhBMP-2 or rhBMP-7), was performed, which suggested that only rhBMP-2 was better than ICBG for lumbar fusion. There was no difference in the incidence of adverse events between rhBMP and ICBG (OR 0.91, 95% CI 0.70-1.18, P = 0.47).

CONCLUSION

In lumbar fusion, rhBMP-2 exhibited a higher fusion success rate and reduced the risk of re-operation. No difference in complication rate is between rhBMP (rhBMP-2 and rhBMP-7) and ICBG. We suggest rhBMP especially rhBMP-2 as an effective substitute for ICBG for lumbar fusion.

LEVEL OF EVIDENCE

1.

Interbody fusion in degenerative lumbar spinal stenosis with additional posterolateral fusion using Escherichia coli-derived bone morphogenetic protein-2: A Pilot study

This case series investigated the efficacy and optimal dose of Escherichia coli-derived bone morphogenetic protein-2 (E.BMP-2) as a bone graft substitute for additional posterolateral spinal fusion, accompanying interbody fusion procedures, for treating lumbar degenerative spinal stenosis. This study focused on the optimal dose for each segment and the efficacy of E.BMP-2 as a substitute for autogenous iliac bone graft.Ten patients were enrolled from January 2015 to December 2015, and underwent an additional posterolateral fusion procedure, with 2.5 mg of E.BMP-2 followed by decompression, transpedicular fixation, and interbody fusion. The mean follow-up period was 13.9 months, and regular radiological examinations were performed in every case. Clinical outcomes were measured with a visual analog scale for back pain (VAS-BP), and leg pain (VAS-LP) and the Korean Oswestry Disability Index (K-ODI). All parameters were assessed preoperatively and postoperatively at 12 months.All 18 segments treated with E.BMP-2 completely fused in 6 months as observed on both simple radiography and computed tomography. The mean fusion period was 4.5 months on simple radiography. At 12 months follow-up, VAS-BP, VAS-LP, and K-ODI scores (1.9 ± 1.5, 1.9 ± 1.9, 11.0 ± 6.6, respectively) had improved significantly compared to preoperative scores (5.5 ± 1.9, 6.5 ± 1.9, and 49.9 ± 11.5, respectively, P < .05). There were no postoperative wound infections, neurological symptoms, or complications associated with the use of E.BMP-2 during the follow-up period.E.BMP-2 could be used to enhance the outcomes in posterolateral spinal fusion following interbody fusion surgery. In the present study, 2.5 mg of the E.BMP-2 per segment was sufficient to obtain bony union in posterolateral fusion surgery. Further large-scale trials with long-term follow-up are necessary to evaluate the various complications related to the use of E.BMP-2.

Evaluation of Heterotopic Ossification After Using Recombinant Human Bone Morphogenetic Protein-2 in Transforaminal Lumbar Interbody Fusion: A Computed Tomography Review of 996 Disc Levels

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Reported incidences and complications of heterotopic ossification (HO) after using recombinant human bone morphogenetic protein-2 (rhBMP-2) in transforaminal lumbar interbody fusion (TLIF) have been inconclusive. This study was designed to evaluate both incidences of radiologic and symptomatic HO in a large series of TLIFs using rhBMP-2.

METHODS

A total of 996 disc levels in 927 consecutive TLIF patients were retrospectively evaluated at 6-month postoperative follow-up in a single surgical practice. Subjects were separated into the BMP group and the control group. Operative reports, pre- and postoperative medical records were reviewed. Computed tomography (CT) scans were analyzed and graded independently for ossification at each disc level of TLIF.

RESULTS

A total of 933 disc levels were in the BMP group, and 63 were in the control group. Six-month fusion rate of interbody was 92.5% in the BMP group, which was significantly higher in contrast to 71.4% in the control group (P < .001). The incidence of radiologic HO in the BMP group was 13.5%, which was significantly higher than 1.6% in the control group (P = .006). After controlling for basic demographics and comorbidities, the presence of radiologic HO was significantly associated with the use of rhBMP-2 (P = .026). However, only one case in the BMP group (0.11%) developed a symptomatic HO (mild-medium left buttock pain, treated nonsurgically) involving left foramen of L5-S1.

CONCLUSIONS

rhBMP-2 can be safely used in TLIF with regard to HO. There was a low rate of radiologic HO and minimal symptomatic HO, with high fusion rates at 6 months postoperative.

Application of Cytokines of the Bone Morphogenetic Protein (BMP) Family in Spinal Fusion - Effects on the Bone, Intervertebral Disc and Mesenchymal Stromal Cells

Low back pain is a prevalent socio-economic burden and is often associated with damaged or degenerated intervertebral discs (IVDs). When conservative therapy fails, removal of the IVD (discectomy), followed by intersomatic spinal fusion, is currently the standard practice in clinics. The remaining space is filled with an intersomatic device (cage) and with bone substitutes to achieve disc height compensation and bone fusion. As a complication, in up to 30% of cases, spinal non-fusions result in a painful pseudoarthrosis. Bone morphogenetic proteins (BMPs) have been clinically applied with varied outcomes. Several members of the BMP family, such as BMP2, BMP4, BMP6, BMP7, and BMP9, are known to induce osteogenesis. Questions remain on why hyper-physiological doses of BMPs do not show beneficial effects in certain patients. In this respect, BMP antagonists secreted by mesenchymal cells, which might interfere with or block the action of BMPs, have drawn research attention as possible targets for the enhancement of spinal fusion or the prevention of non-unions. Examples of these antagonists are noggin, gremlin1 and 2, chordin, follistatin, BMP3, and twisted gastrulation. In this review, we discuss current evidence of the osteogenic effects of several members of the BMP family on osteoblasts, IVD cells, and mesenchymal stromal cells. We consider in vitro and in vivo studies performed in human, mouse, rat, and rabbit related to BMP and BMP antagonists in the last two decades. We give insights into the effects that BMP have on the ossification of the spine. Furthermore, the benefits, pitfalls, and possible safety concerns using these cytokines for the improvement of spinal fusion are discussed.

Scientific, Clinical, Regulatory, and Economic Aspects of Choosing Bone Graft/Biological Options in Spine Surgery

Spinal arthrodesis is a major element of the spinal surgeon's practice. To attain successful fusion rates, attention must be paid to spinal segment immobilization and proper selection of bone graft. Autogenous bone graft (ie, ICBG), the "gold standard," with or without graft extenders and enhancers provides the foundation for most spinal fusions. ABG is the only graft option containing all 3 factors of new bone growth: osteoconductivity, osteoinductivity, and osteogenicity. While many bone graft alternatives function well as bone graft extenders, only growth factors proteins (ie, rhBMP-2 or OP-2) function as bone graft enhancers and substitutes. The search for optimal hybrid interbody cages, bone graft substitutes, autogenous or allogenic stem cells, and nanostructure scaffolds for release of growth factors continues.

Current Treatment Options for Intervertebral Disc Pathologies

The complex structure of the intervertebral disc within the spine is well suited to its mechanical function. However, it is also prone to degeneration, which is associated with various clinical symptoms and conditions, ranging from disc herniation to back pain to spinal stenosis. Most patients' conditions are managed conservatively but a small proportion progress to having surgery. This may be decompression (to remove tissue such as the disc, bone, or hypertrophic ligaments impinging on nerves) or fusion of the normally mobile intervertebral joint to immobilize it and so reduce pain. These used to involve fairly major surgical procedures, but in the past decade there has been much progress to make the surgery more refined and less invasive, for example using endoscopic approaches. Simultaneously, the research world has been studying and developing tissue engineering and cellular techniques for attempting to regenerate the intervertebral disc, whether simply the central nucleus pulposus or a complete intricate assembly to replicate the native structure of this and the surrounding annulus fibrosus, cartilage endplate, and bone. To date, none of the complex entities have been trialed, while cellular approaches are easier to utilize, have progressed to clinical trials, and may offer a better solution.

Sustained delivery of PlGF-2123-144*-fused BMP2-related peptide P28 from small intestinal submucosa/polylactic acid scaffold material for bone tissue regeneration

Bone morphogenetic protein 2 (BMP-2) is one of the most important factors for bone tissue formation. However, its use over the past decade has been associated with numerous side effects. This is due to the fact that recombinant human (rh) BMP-2 has several biological functions, as well as that non-physiological high dosages were commonly administered. In this study, we synthesized a novel BMP-2-related peptide (designated P28) and fused a mutant domain in placenta growth factor-2 (PlGF-2_123-144*) that allowed for the "super-affinity" of extracellular matrix proteins to P28, effectively controlling the release of low dosage P28 from small intestinal submucosa/polylactic acid (SIS/PLA) scaffolds. These have been shown to be excellent scaffold materials both in vivo and in vitro. The aim of this study was to determine whether these scaffolds could support the controlled release of P28 over time, and whether the composite materials could serve as structurally and functionally superior bone substitutes in vivo. Our results demonstrated that P28 could be released slowly from SIS/PLA to promote the adhesion, proliferation, and differentiation of bone marrow stromal cells (BMSCs) in vitro. In vivo, radiographic and histological examination showed that SIS/PLA/P28/PlGF-2_123-144* completely repaired critical-size bone defects, compared to SIS/PLA, SIS/PLA/PlGF-2_123-144*, or SIS/PLA/P28 alone. These findings suggest that this controlled release system may have promising clinical applications in bone tissue engineering.