Beta tricalcium phosphate: observation of use in 100 posterolateral lumbar instrumented fusions

Artificial lamina after laminectomy: Progress, applications, and future perspectives

In clinical practice, laminectomy is a commonly used procedure for spinal decompression in patients suffering from spinal disorders such as ossification of ligamentum flavum, lumbar stenosis, severe spinal fracture, and intraspinal tumors. However, the loss of posterior column bony support, the extensive proliferation of fibroblasts and scar formation after laminectomy, and other complications (such as postoperative epidural fibrosis and iatrogenic instability) may cause new symptoms requiring revision surgery. Implantation of an artificial lamina prosthesis is one of the most important methods to avoid post-laminectomy complications. Artificial lamina is a type of synthetic lamina tissue made of various materials and shapes designed to replace the resected autologous lamina. Artificial laminae can provide a barrier between the dural sac and posterior soft tissues to prevent postoperative epidural fibrosis and paravertebral muscle compression and provide mechanical support to maintain spinal alignment. In this paper, we briefly review the complications of laminectomy and the necessity of artificial lamina, then we review various artificial laminae from clinical practice and laboratory research perspectives. Based on a combination of additive manufacturing technology and finite element analysis for spine surgery, we propose a new designing perspective of artificial lamina for potential use in clinical practice.

Frontal sinus obliteration with beta-tricalcium phosphate putty: case series with long-term radiological follow up

OBJECTIVES

Frontal sinus obliteration is often performed using fat, autologous bone or a range of synthetic materials. This paper reports the long-term clinical and radiological outcomes of frontal sinus obliteration using beta-tricalcium phosphate putty.

METHODS

A retrospective audit was performed of patients who underwent frontal sinus obliteration with beta-tricalcium phosphate putty. Patient-, disease- and procedure-related data were collected. Pre- and post-operative computed tomography scans were reviewed to assess bone integration.

RESULTS

Four patients underwent frontal sinus obliteration using beta-tricalcium phosphate putty for treatment of a cerebrospinal leak, mucocele and recalcitrant frontal sinusitis. All patients had disease resolution, with no intra- or post-operative complications reported in the 16.5-month follow up. Post-operative computed tomography scans confirmed native bone obliteration of the frontonasal ducts in all patients.

CONCLUSION

Beta-tricalcium phosphate putty is a safe and effective option for bone obliteration of the frontal sinus in a range of pathologies, including cerebrospinal fluid leak.

Effect of Tricalcium Phosphate on Healing of Non-Unions: An Observational Study of over 400 Non-Unions

Purpose

A central aspect of the treatment of non-unions is the filling of bone defects. The quantity of available autologous bone for this purpose is limited. Alternatively, or additionally, bone substitutes may be used. The aim of this retrospective, single-center study including 404 non-unions in 393 patients is to investigate the effect of tricalcium phosphate (TCP) on the healing of non-unions. Furthermore, the influence of gender, age, smoking status, comorbidities, type of surgical procedure, presence of infection, and length of treatment was investigated.

Methods

We evaluated three groups of patients. Group 1 received TCP + BG, group 2 received BG alone and group 3 received no augmentation. Bone stability was assessed 1 and 2 years after non-union revision surgery through analysis of radiographs using the Lane Sandhu Score. Scores ≥3 were rated as stable Other influencing factors were collected from the electronic medical record.

Results

In 224 non-unions, bone defects were filled with autologous bone and TCP (TCP+BG). In 137 non-unions, bone defects were filled with autologous bone (BG), and in 43 non-unions presenting non-relevant defects, neither autologous bone nor TCP were used (NBG). After 2 years, 72.7% of the TCP+BG patients, 90.1% of the BG patients and 84.4% of the NBG patients achieved a consolidation score ≥3. Advanced age, presence of comorbidities and longer treatment period had a significantly negative effect on consolidation 1 year after surgery. Longer treatment periods also showed a negative significant effect after 2 years. It is notable that larger defects, mainly treated with the combination of autologous bone and TCP, showed similar healing rates to that of smaller defects after 2 years.

Conclusion

The combination of TCP and autologous bone-grafts shows good results in the reconstruction of complicated bone-defects, but patience is required since the healing period exceeds 1 year in most patients.

Safety and Tolerability of Stromal Vascular Fraction Combined with β-Tricalcium Phosphate in Posterior Lumbar Interbody Fusion: Phase I Clinical Trial

The rates of pseudarthrosis remain high despite recent advances in bone graft substitutes for spinal fusion surgery. The aim of this single center, non-randomized, open-label clinical trial was to determine the feasibility of combined use of stromal vascular fraction (SVF) and β-tricalcium phosphate (β-TCP) for patients who require posterior lumbar interbody fusion (PLIF) and pedicle screw fixation. Two polyetheretherketone (PEEK) cages were inserted into the intervertebral space following complete removal of the intervertebral disc. The PEEK cage (SVF group) on the right side of the patient was filled with β-TCP in combination with SVF, and the cage on the left side (control group) was filled with β-TCP alone. Fusion rate and cage subsidence were assessed by lumbar spine X-ray and CT at 6 and 12 months postoperatively. At the 6-month follow-up, 54.5% of the SVF group (right-sided cages) and 18.2% of the control group (left-sided cages) had radiologic evidence of bone fusion (p = 0.151). The 12-month fusion rate of the right-sided cages was 100%, while that of the left-sided cages was 91.6% (p = 0.755). Cage subsidence was not observed. Perioperative combined use of SVF with β-TCP is feasible and safe in patients who require spinal fusion surgery, and it has the potential to increase the early bone fusion rate following spinal fusion surgery.

β-tricalcium phosphate for bone substitution: Synthesis and properties

β-tricalcium phosphate (β-TCP) is one the most used and potent synthetic bone graft substitute. It is not only osteoconductive, but also osteoinductive. These properties, combined with its cell-mediated resorption, allow full bone defects regeneration. Its clinical outcome is sometimes considered to be "unpredictable", possibly due to a poor understanding of β-TCP physico-chemical properties: β-TCP crystallographic structure is not fully uncovered; recent results suggest that sintered β-TCP is coated with a Ca-rich alkaline phase; β-TCP apatite-forming ability and osteoinductivity may be enhanced by a hydrothermal treatment; β-TCP grain size and porosity are strongly modified by the presence of minute amounts of β-calcium pyrophosphate or hydroxyapatite impurities. The aim of the present article is to provide a critical, but still rather comprehensive review of the current state of knowledge on β-TCP, with a strong focus on its synthesis and physico-chemical properties, and their link to the in vivo response. STATEMENT OF SIGNIFICANCE: The present review documents the richness, breadth, and interest of the research devoted to β-tricalcium phosphate (β-TCP). β-TCP is synthetic, osteoconductive, osteoinductive, and its resorption is cell-mediated, thus making it one of the most potent bone graft substitutes. This comprehensive review reveals that there are a number of aspects, such as surface chemistry, crystallography, or stoichiometry deviations, that are still poorly understood. As such, β-TCP is still an exciting scientific playground despite a 50 year long history and > 200 yearly publications.

Radiographic and CT Evaluation of Recombinant Human Bone Morphogenetic Protein-2-assisted Cervical Spinal Interbody Fusion

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

To radiographically demonstrate the distinct fusion pattern of recombinant human bone morphogenetic protein-2 (rhBMP-2) in the setting of anterior cervical discectomy and fusion.

SUMMARY OF BACKGROUND DATA

Studies investigating spinal fusion assisted with rhBMP-2 have yielded promising results, suggesting rhBMP-2 is an efficacious alternative to iliac crest autografts. rhBMP-2-assisted spinal fusion both hastens healing and eliminates patient morbidity from iliac crest autograft. Unique to rhBMP-assisted spinal fusion is its distinct radiographic fusion pattern as fusion is achieved. Despite promising results and increased clinical use of rhBMP-2, there remains a paucity of literature documenting this radiographic process.

MATERIALS AND METHODS

This study included 26 patients who underwent single-level anterior cervical discectomy and fusion using rhBMP-2. All data used for this study was collected from a prior FDA Investigational Device Exemption study.

RESULTS

A polyetheretherketone cage was used as an interbody disk spacer in all 26 patients. Patients were evaluated between 2 and 6 weeks after surgery and subsequently at 3, 6, 12, and 24 months postoperative. All patients underwent plain radiography at every follow-up visit, and computed tomograhy evaluation was performed at 3, 6, 12, and 24 months as part of the study protocol. Earliest fusion was observed at 3 months in 38% of patients. Likely fusion was observed in all patients by 12 months postoperative.

CONCLUSIONS

rhBMP-2 leads to both successful interbody fusion and an enhanced fusion rate with unique imaging characteristics. Additional characteristics of BMP observed in 100% of patients included prevertebral soft-tissue swelling and early endplate resorption. Other common features included polyetheretherketone cage migration, heterotopic bone formation and cage subsidence.

Autologous mesenchymal stromal cells embedded in tricalcium phosphate for posterolateral spinal fusion: results of a prospective phase I/II clinical trial with long-term follow-up

BACKGROUND

Posterolateral spinal fusion with autologous bone graft is considered the "gold standard" for lumbar degenerative disc disease (DDD) when surgical treatment is indicated. The potential role of mesenchymal stromal cells (MSCs) to replace the bone graft in this setting has not been fully addressed.

OBJECTIVE

To analyze the safety, feasibility and potential clinical efficacy of the implantation of autologous MSCs embedded with tricalcium phosphate as a therapeutic alternative to bone graft in patients with DDD during posterolateral spine fusion.

STUDY DESIGN

Phase I/II single-arm prospective clinical trial.

METHODS

Eleven patients with monosegmental DDD at L4-L5 or L5-S1 level were included. Autologous bone marrow-derived MSC were expanded in our Good Manufacturing Practice (GMP) Facility and implanted during spinal surgery embedded in a tricalcium phosphate carrier. Monitoring of patients included a postoperative period of 12 months with four visits (after the 1st, 3rd, 6th, and 12th month), with clinical and radiological assessment that included the visual analog scale (VAS), the Oswestry disability index (ODI), the Short-Form Health Survey (SF-36), the vertebral fusion grade observed through a simple Rx, and the evaluation of possible complications or adverse reactions. In addition, all patients were further followed up to 5 years for outcome.

RESULTS

Median age of patients included was 44 years (range 30-58 years), and male/female ratio was (6/5) L4-L5 and L5-S1 DDD was present five and six patients, respectively. Autologous MSCs were expanded in all cases. There were no adverse effects related to cell implantation. Regarding efficacy, both VAS and ODI scores improved after surgery. Radiologically, 80% of patients achieved lumbar fusion at the end of the follow-up. No adverse effects related to the procedure were recorded.

CONCLUSIONS

The use of autologous MSCs for spine fusion in patients with monosegmental degenerative disc disease is feasible, safe, and potentially effective.

TRIAL REGISTRATION

no. EudraCT: 2010-018335-17 ; code Identifier: NCT01513694 ( clinicaltrials.gov ).

An inception cohort study of patients in a military clinic treated for lower back pain with lumbar fusion and SIGNAFUSE® with a systematic review of the literature

Background: Use of synthetic bone graft substitutes for spinal fusion has increased sharply over the past 20 years. SIGNAFUSE® is one such synthetic graft material that provides an osteostimulatory effect for spinal fusion. Because clinical trials are not required for commercialization of synthetic bone graft substitutes in the United States, fusion rates attained using SIGNAFUSE for lumbar fusion are not well documented. The goal of the current study is to determine the rate of spinal fusion in a military clinic following lumbar fusion surgery augmented with SIGNAFUSE. Methods: We report a retrospective chart review of 8 patients who received lumbar spinal fusion surgery augmented with SIGNAFUSE. All patients were assessed by computed tomographic (CT) imaging at least 1-year post-surgery to determine whether bony fusion had occurred. We also systematically reviewed literature sources that report fusion rate following spinal fusion surgery, for broader context. Results: An average of 1.6 spinal levels were treated with SIGNAFUSE-loaded interbody cages. All patients had stabilization hardware via pedicle screws or integrated cage fixation. Seven of 8 patients successfully fused, for an overall fusion rate of 87.5% (95% confidence interval: 47.4% to 99.7%). Systematic review of 26 recent publications that included 1,126 patients treated with synthetic bone graft showed that the overall fusion rate in the literature is 84.4%. Conclusions: Fusion was achieved in 87.5% of patients treated with SIGNAFUSE. This is comparable to the fusion rate in a systematic review of 1,126 patients treated with synthetic bone graft materials.

Evidence of Negative Effects of Defect Size and Older Patient Age by Quantitative CT-Based 3D Image Analysis in Ultraporous Beta-Tricalcium Phosphate Grafted Extremity Bone Defects at One Year

Introduction

Synthetic bone graft materials are commonly used to fill defects after curettage of benign bone lesions. Ultraporous beta tricalcium phosphate (TCP) is a popular synthetic compound used in this situation. Prior clinical studies based on plain X-ray analysis suggest incorporation of TCP is incomplete, even when combined with bone marrow (BMA).

Purpose

The purpose was to analyze volumetric CT-based changes in defects grafted with TCP with/without BMA in a completed prospective RCT to objectively determine (1) relationship between size and age versus TCP incorporation and (2) whether there is an advantage to addition of BMA.

Methods

Twenty-one patients with CT scans at ≥1 year follow-up available for digital analysis (TCP=10, TCP w/BMA =11) form the study population. CT image stacks were evaluated by creating volumetric masks using MIMICS imaging software for total defect, graft remaining, and graft incorporated volumes graft incorporation endpoints.

Results

Overall, there was significant (p=0.0029) negative correlation (r² = 0.38) between defect size and ratio of incorporated bone to defect size. This relationship remained strong (r² = 0.56) particularly for defects > 20 cc but not for smaller defects. Bone width was also a significantly related factor (r² = 0.94), with less graft incorporation in larger bone sites, in part likely due to the linear relationship between defect size and bone width. Relationship with age was complex and closely tied to defect volume. For larger defect volumes, younger patients were more successful at graft incorporation. Although age itself was not an independently significant factor, as defect volume increased, advanced age more negatively impacted new bone formation.

Conclusions

Larger size defect and affected bone and advancing age appear to be important negative factors in synthetic graft incorporation. Results showed no advantage to addition of BMA to TCP.

Clinical and CT Analysis of Lumbar Spine Arthrodesis: β-Tricalcium Phosphate Versus Demineralized Bone Matrix

Background

Bone graft substitutes have been developed to circumvent donor site morbidity associated with iliac crest bone graft, but sparse literature compares the efficacy of various substitutes. Two commonly used bone graft substitutes used in lumbar fusion are β-tricalcium phosphate (BTP) and demineralized bone matrix (DBM).

Methods

A retrospective review of patients who underwent instrumented posterolateral lumbar fusion was conducted by a single surgeon from January 2013 to December 2016. Patients were divided into two groups based on whether DBM or BTP as graft in conjunction with local autograft. Clinical outcomes scores were collected at a minimum of 1-year follow-up. Postoperative CT scans were evaluated to assess fusion.

Results

Forty-one patients (DBM, 21 and BTP, 20) were reviewed. No significant differences were found in terms of age, sex, body mass index, smoking, diabetes, steroids, osteoporosis, American Society of Anesthesiologists classification, number of levels fused, estimated blood loss, length of stay, or surgical time between the DBM and BTP groups. A trend was found toward lower revision surgery (zero versus 15%), improved visual analog scale scores (postoperative change of 1.81 versus 3.25; P = 0.09), and higher rates of fusion (90% versus 70%; P = 0.09) in the DBM group compared with the BTP group.

Conclusions

No significant difference was found in clinical outcomes at 1 year, with a trend toward a higher fusion rate and lower revision surgery with DBM.

Gelfoam Interposition Minimizes Risk of Fistula and Postoperative Bleeding in Modified-Furlow Palatoplasty

Failure to accomplish a tension-free, watertight closure predisposes the palatoplasty patient to fistula formation. Perioperative bleeding also places the patient at risk for adverse airway events (AAE). This study introduces the incorporation of a hemostatic gelatin sponge (Gelfoam) into layered palatoplasty to minimize adverse postoperative bleeding and fistula formation. A retrospective chart review was performed to identify subjects who underwent Furlow palatoplasty with insertion of Gelfoam from 2010 to 2015. Exclusion criteria include age >3 years, prior palate surgery, <30-day follow-up, immunosuppressive state, and diagnosis of Treacher-Collins or Apert Syndrome. Demographic data include age, sex, cleft laterality, prior surgeries, Veau classification, Pierre Robin status, and tracheostomy dependence. Primary outcome was fistula formation. Secondary outcomes included perioperative metrics and AAE.One hundred subjects met criteria, 45% female. Average age was 14.6 months. Subjects with syndromes comprised 28%, with 16% diagnosed with Pierre Robin. Two subjects were tracheostomy-dependent. Prior cleft and mandibular procedures were performed in 55%. Isolated palatal defects were seen in 46%, unilateral lip and palate in 41%, and bilateral lip and palate in 13%. The majority of defects were Veau II and III (35% and 34%, respectively). Adverse airway events occurred in 2%, one of which resulted in reintubation. One subject (1%) was found to have a postoperative fistula.The incorporation of Gelfoam in the modified-Furlow palatoplasty results in a low rate of oronasal fistula (1%) and low perioperative risk of AAE. Further prospective comparison of this method to others will be the focus of future work.

Calcium orthophosphates (CaPO4): Occurrence and properties

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates (CaPO₄). This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with CaPO₄, while dental caries (tooth decay) and osteoporosis (a low bone mass with microarchitectural changes) mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenorthophosphates. Due to the compositional similarities to the calcified tissues of mammals, CaPO₄ are widely used as biomaterials for bone grafting purposes. In addition, CaPO₄ have many other applications. Thus, there is a great significance of CaPO₄ for the humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Radiographic and Clinical Outcome of Silicate-substituted Calcium Phosphate (Si-CaP) Ceramic Bone Graft in Spinal Fusion Procedures

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To evaluate the radiographic and clinical outcome of silicate-substituted calcium phosphate (Si-CaP), utilized as a graft substance in spinal fusion procedures.

SUMMARY OF BACKGROUND DATA

Specific properties of Si-CaP provide the graft with negative surface charge that can result in a positive effect on the osteoblast activity and neovascularization of the bone.

METHODS

This study included those patients who underwent spinal fusion procedures between 2007 and 2011 in which Si-CaP was used as the only bone graft substance. Fusion was evaluated on follow-up CT scans. Clinical outcome was assessed using Oswestry Disability Index, Neck Disability Index, and the visual analogue scale (VAS) for back, leg, neck, and arm pain.

RESULTS

A total of 234 patients (516 spinal fusion levels) were studied. Surgical procedures consisted of 57 transforaminal lumbar interbody fusion, 49 anterior cervical discectomy and fusion, 44 extreme lateral interbody fusion, 30 posterior cervical fusions, 19 thoracic fusion surgeries, 17 axial lumbar interbody fusions, 16 combined anterior and posterior cervical fusions, and 2 anterior lumbar interbody fusion. At a mean radiographic follow-up of 14.2±4.3 months, fusion was found to be present in 82.9% of patients and 86.8% of levels. The highest fusion rate was observed in the cervical region. At the latest clinical follow-up of 21.7±14.2 months, all clinical outcome parameters showed significant improvement. The Oswestry Disability Index improved from 45.6 to 13.3 points, Neck Disability Index from 40.6 to 29.3, VAS back from 6.1 to 3.5, VAS leg from 5.6 to 2.4, VAS neck from 4.7 to 2.7, and VAS arm from 4.1 to 1.7. Of 7 cases with secondary surgical procedure at the index level, the indication for surgery was nonunion in 3 patients.

CONCLUSIONS

Si-CaP is an effective bone graft substitute. At the latest follow-up, favorable radiographic and clinical outcome was observed in the majority of patients.

LEVEL OF EVIDENCE

Level-III.

Use of Nanocrystalline Hydroxyapatite With Autologous BMA and Local Bone in the Lumbar Spine: A Retrospective CT Analysis of Posterolateral Fusion Results

STUDY DESIGN

A retrospective, multicenter, medical record review and independent analysis of computed tomographic scans was performed in 46 patients to determine radiographic arthrodesis rates after 1-segment, 2-segment, or 3-segment instrumented posterolateral fusions (PLF) using autograft, bone marrow aspirate (BMA), and a nanocrystalline hydroxyapatite bone void filler (nHA).

OBJECTIVE

To determine the radiographic arthrodesis rates after instrumented lumbar PLF using local autograft, BMA, and nHA.

SUMMARY OF BACKGROUND DATA

The use of iliac crest autograft in posterolateral spine fusion carries real and significant risks. Many forms of nanocrystalline hydroxyapatite have been studied in various preclinical models, but no human studies have reviewed its efficacy as a bone graft supplement in PLF.

METHODS

Posterolateral arthrodesis progression was documented approximately 12 months postoperatively using a computed tomographic scan and evaluated by an independent radiologist for the presence of bridging bone. One-year postoperative clinical outcomes were assessed using the PROLO score.

RESULTS

Radiographically, 91% patients treated exhibited bilateral or unilateral posterolateral bridging bone. Ninety-four percent of the segments treated exhibited bilateral or unilateral posterolateral bridging bone, whereas 6% segments exhibited no posterolateral bridging bone on either side. A total of 93% individual sites treated exhibited posterolateral bridging bone. In 1-segment, 2-segment, and 3-segment arthrodesis, 88%, 93%, and 100%, respectively, of individual sites exhibited radiographic bridging bone. One-year postoperative PROLO scores for 77% patients were excellent or good. There were no complications related to the posterolateral graft mass and no symptomatic nonunions.

CONCLUSIONS

The arthrodesis rates after instrumented lumbar fusion using local autograft mixed with BMA and the nHA is equivalent to the rates reported for iliac crest autograft in these indications, including stringent indications, such as 3-segment procedures. By approximately 12 months postoperatively, there was no significant difference in the rates of bridging bone between the 1-segment, 2-segment, and 3-segment procedures.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Comparison of a calcium phosphate bone substitute with recombinant human bone morphogenetic protein-2: a prospective study of fusion rates, clinical outcomes and complications with 24-month follow-up

PURPOSE

Recombinant human bone morphogenetic protein-2 (rhBMP-2) generally provides high rates of clinical improvement and fusion. However, rhBMP-2 has been associated with adverse effects. Recently, a beta tricalcium phosphate (β-TCP) bone substitute has been developed. The aim of this study was to determine the fusion rates and clinical outcomes of patients treated with β-TCP compared to rhBMP-2.

METHODS

One hundred and thirty-five consecutive patients who underwent lateral lumbar interbody fusion with β-TCP (n = 25) or rhBMP-2 (n = 110) in the interbody cage were included in the study. The 25 β-TCP patients were a group of consecutive patients from numbers 46 to 70. Clinical outcomes included back and leg pain, Oswestry Disability Index (ODI), and SF-36 physical and mental component scores (PCS and MCS). CT scans were performed at 6, 12, 18, and 24 months until confirmation of solid interbody fusion, with no further scans performed once fusion was achieved. Targeted CT at the operative level(s) was performed to reduce radiation exposure.

RESULTS

At 24 months there was no significant difference between clinical outcomes of the β-TCP or rhBMP-2 patients, with improvements in back pain (46% and 49%; P = 0.98), leg pain (31 and 52%; P = 0.14), ODI (38 and 41%; P = 0.81), SF-36 PCS (37 and 38%; P = 0.87), and SF-36 MCS (8 and 8%; P = 0.93). The fusion rate was significantly higher for rhBMP-2 with 96% compared to 80% for β-TCP (P = 0.01). Separating patients into those with a standalone cage and those with supplemental posterior instrumentation, there was no significant difference between instrumented fusion rates of the β-TCP and rhBMP-2 patients at 6 (P = 0.44), 12 (P = 0.49), 18 (P = 0.31) or 24 (P = 0.14) months. For standalone patients there was a significant difference at 6 (P = 0.01), 12 (P = 0.008) and 18 months (P = 0.004) with higher fusion rates in the rhBMP-2 group; however, by 24 months this was not significant (P = 0.18).

CONCLUSIONS

Comparable clinical outcomes and complication rates suggest that β-TCP is a viable alternative to rhBMP-2. The difference in fusion rates for the standalone patients suggests that β-TCP may require supplemental posterior instrumentation to enhance fusion.

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

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficacy of i-Factor Bone Graft versus Autograft in Anterior Cervical Discectomy and Fusion: Results of the Prospective, Randomized, Single-blinded Food and Drug Administration Investigational Device Exemption Study

STUDY DESIGN

A prospective, randomized, controlled, parallel, single-blinded noninferiority multicenter pivotal FDA IDE trial.

OBJECTIVE

The objective of this study was to investigate efficacy and safety of i-Factor Bone Graft (i-Factor) compared with local autograft in single-level anterior cervical discectomy and fusion (ACDF) for cervical radiculopathy.

SUMMARY OF BACKGROUND DATA

i-Factor is a composite bone substitute material consisting of the P-15 synthetic collagen fragment adsorbed onto anorganic bone mineral and suspended in an inert biocompatible hydrogel carrier. P-15 has demonstrated bone healing efficacy in dental, orthopedic, and nonhuman applications.

METHODS

Patients randomly received either autograft (N = 154) or i-Factor (N = 165) in a cortical ring allograft. Study success was defined as noninferiority in fusion, Neck Disability Index (NDI), and Neurological Success endpoints, and similar adverse events profile at 12 months.

RESULTS

At 12 months (follow-up rate 87%), both i-Factor and autograft subjects demonstrated a high fusion rate (88.97% and 85.82%, respectively, noninferiority P = 0.0004), significant improvements in NDI (28.75 and 27.40, respectively, noninferiority P < 0.0001), and high Neurological Success rate (93.71% and 93.01%, respectively, noninferiority P < 0.0001). There was no difference in the rate of adverse events (83.64% and 82.47% in the i-Factor and autograft groups, respectively, P = 0.8814). Overall success rate consisting of fusion, NDI, Neurological Success and Safety Success was higher in i-Factor subjects than in autograft subjects (68.75% and 56.94%, respectively, P = 0.0382). Improvements in VAS pain and SF-36v2 scores were clinically relevant and similar between the groups. A high proportion of patients reported good or excellent Odom outcomes (81.4% in both groups).

CONCLUSION

i-Factor has met all four FDA mandated noninferiority success criteria and has demonstrated safety and efficacy in single-level ACDF for cervical radiculopathy. i-Factor and autograft groups demonstrated significant postsurgical improvement and high fusion rates.

LEVEL OF EVIDENCE

1.

Calcium orthophosphates (CaPO4): occurrence and properties

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates (CaPO4). This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with CaPO4, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenorthophosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of CaPO4. Similarly, dental caries and osteoporosis might be considered as in vivo dissolution of CaPO4. In addition, natural CaPO4 are the major source of phosphorus, which is used to produce agricultural fertilizers, detergents and various phosphorus-containing chemicals. Thus, there is a great significance of CaPO4 for the humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Preliminary study showing safety/efficacy of nanoss bioactive versus vitoss as bone graft expanders for lumbar noninstrumented fusions

Background:

The lateral fusion mass for multilevel lumbar laminectomies with noninstrumented posterolateral fusions now often utilizes lamina autograft and bone marrow aspirate (BMA) mixed with one of two bone graft expanders: either Vitoss (Orthovita, Malvern, PA, USA) or NanOss Bioactive (Regeneration Technologies Corporation: RTI, Alachua, FL, USA).

Methods:

Here, we compared two sequential prospective the times to fusion, fusion rates, complications, and infection rates for two prospective cohorts of patients utilizing either Vitoss (first 213 patients) or NanOss (subsequent 45 patients) respectively, undergoing multilevel lumbar laminectomies (average 4.6 vs. 4.5 levels) with noninstrumented fusions (average 1.3 vs. 1.2 levels). Surgery addressed stenosis/ossification of the yellow ligament (OYL) (all patients), with subsets exhibiting degenerative spondylolisthesis synovial cysts, and disc disease. Fusion was documented by two independent neuroradiologists blinded to the study design, utilizing dynamic X-rays and two dimensional computed tomography (2D-CT) studies up to 6 months postoperatively, and up to 1 year where indicated.

Results:

Comparison of patients receiving Vitoss versus NanOss as bone graft expanders revealed nearly comparable; times to fusion (5.3 months vs. 4.8 months), fusion rates (210 [98.6%] vs. 45 [100%] patients), pseudarthroses (3 [1.4%] vs. 0), postoperative seromas (2 [0.94%] vs. 0), and deep wound infections (2 [0.94%] vs. 0).

Conclusion:

In this preliminary study of patients undergoing multilevel lumbar lamienctomies with posterolateral noninstrumented fusions, results were nearly comparable utilizing Vitoss or NanOss as bone graft expanders. Although the number of NanOss patients was substantially lower, the comparable efficacy and absence of postoperative complications for noninstrumented fusions is promising.

Biomaterials for Bone Regenerative Engineering

Strategies for bone tissue regeneration have been continuously evolving for the last 25 years since the introduction of the "tissue engineering" concept. The convergence of the life, physical, and engineering sciences has brought in several advanced technologies available to tissue engineers and scientists. This resulted in the creation of a new multidisciplinary field termed as "regenerative engineering". In this article, the role of biomaterials in bone regenerative engineering is systematically reviewed to elucidate the new design criteria for the next generation of biomaterials for bone regenerative engineering. The exemplary design of biomaterials harnessing various materials characteristics towards successful bone defect repair and regeneration is highlighted. Particular attention is given to the attempts of incorporating advanced materials science, stem cell technologies, and developmental biology into biomaterials design to engineer and develop the next generation bone grafts.

Preliminary documentation of the comparable efficacy of vitoss versus NanOss bioactive as bone graft expanders for posterior cervical fusion

BACKGROUND

Laminectomies with posterior cervical instrumented fusions often utilize bone graft expanders to supplement cervical lamina/iliac crest autograft/bone marrow aspirate (BMA). Here we compared posterior fusion rates utilizing two graft expanders; Vitoss (Orthovita, Malvern, PA, USA) vs. NanOss Bioactive (Regeneration Technologies Corporation [RTI: Alachua, FL, USA]).

METHODS

Two successive prospective cohorts of patients underwent 1-3 level laminectomies with 5-9 level posterior cervical fusions to address cervical spondylotic myelopathy (CSM) and/or ossification of the posterior longitudinal ligament (OPLL). The first cohort of 72 patients received Vitoss, while the second cohort or 20 patients received NanOss. Fusions were performed utilizing the Vertex/Rod/Eyelet System (Medtronic, Memphis, TN, USA) with braided titanium cables through the base of intact spinous processes (not lateral mass screws) cephalad and caudad to laminectomy defects. Fusion was documented by an independent neuroradiologist blinded to the study design, utilizing dynamic X-rays and two dimensional computed tomography (2D-CT) studies up to 6 months postoperatively, or until fusion or pseudarthrosis was confirmed at 1 year.

RESULTS

Vitoss and NanOss resulted in comparable times to fusion: 5.65 vs. 5.35 months. Dynamic X-ray and CT-documented pseudarthrosis developed in 2 of 72 Vitoss patients at one postoperative year (e.g. bone graft resorbed secondary to early deep wound infections), while none occurred in the 20 patients receiving NanOss.

CONCLUSION

In this preliminary study combining cervical laminectomy/fusions, the time to fusion (5.65 vs. 5.35 months), pseudarthrosis (2.7% vs. 0%), and infection rates (2.7% vs. 0%) were nearly comparable sequentially utilizing Vitoss (72 patients) vs. NanOss (20 patients) as bone graft expanders.

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

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

Radiographic fusion rate after implantation of facet bone dowels

BACKGROUND CONTEXT

Achieving a posterolateral fusion in conjunction with performing decompressive laminectomies can prevent recurrence of stenosis or worsening of spondylolisthesis. Facet bone dowels have been introduced and marketed as a less invasive alternative to pedicle screws. Surgeons have been placing them during lumbar laminectomy surgery and coding for intervertebral biomechanical device and posterolateral fusion. These bone dowels have also been placed percutaneously in outpatient surgery centers and pain clinics for facet-mediated back pain.

PURPOSE

To describe fusion outcomes in patients who underwent facet bone dowel placement.

STUDY DESIGN/SETTING

Retrospective analysis of a single center's experience.

PATIENT SAMPLE

Ninety-six patients comprise the entire cohort of patients who underwent facet bone dowel implantation at our institution with adequate postoperative imaging to determine fusion status.

OUTCOME MEASURES

Fusion rates as determined on postoperative computed tomography (CT) scans and dynamic lumbar X-rays if CT is not available.

METHODS

Threaded facet bone dowels in this study were placed according to the manufacturer's recommended methods. The bone dowels were placed after open exploration of the facet complex or percutaneously through a tubular retractor on the contralateral side from a microdiscectomy or synovial cyst resection. The most recent available postoperative imaging was reviewed to determine fusion status.

RESULTS

Of 96 patients in our series, 6 (6.3%) had a fusion seen on CT and 4 did not exhibit any movement on dynamic lumbar X-rays for a total fusion rate of 10.4% (10/96). Eighty-six (89.6%) patients were shown on imaging to not have a solid fusion either by visualizing a patent facet joint on CT or measurable movement between the flexion and the extension lumbar X-rays.

CONCLUSIONS

This article is mainly intended to question whether the implantation of facet bone dowels can produce a solid fusion radiographically. In our experience, the placement of facet bone dowels does not equal the time, skill, or attention to detail that is necessary for a posterolateral lumbar arthrodesis, and our follow-up radiographic studies clearly demonstrate an inadequate fusion rate.

Ceramic-based bone grafts as a bone grafts extender for lumbar spine arthrodesis: a systematic review

Study Design Systematic review. Objective Ceramic-based bone grafts have been widely utilized to reduce the need for iliac crest bone grafting given the complications associated with the harvest of iliac crest autograft. As a family, ceramics vary widely based on differences in composition, manufacturing, porosity, and structure, which may ultimately affect their efficacy. This article reviews the current data of ceramics used in different environments in the lumbar spine to achieve arthrodesis. Methods Medline, EMBASE, and Cochrane Central Register of Controlled Trials were searched for publications from 1980 to 2013 involving ceramic-based bone grafts in the lumbar spine. Variables such as age of patients, volume of ceramic, procedure, time to evaluation, method of evaluation, specific composition of ceramic, adjuncts used with ceramic products, type of fusion, and fusion rate were compared using a multivariate logistic regression model. Results Thirty studies with 1,332 patients met the final inclusion criteria. The overall fusion rate for all ceramic products as a bone graft extender in the lumbar spine was 86.4%. Age, gender, method of evaluation (plain radiographs, computed tomography, or combination), or specific ceramic product did not significantly affect fusion rate. Ceramics used in combination with local autograft resulted in significantly higher fusion rates compared with all other adjuncts, and bone marrow aspirate and platelet concentrates resulted in significantly lower fusion rates. Conclusions Ceramic-based bone grafts represent a promising bone graft extender in lumbar spine fusion when an osteoinductive stimulus, such as local bone graft is available.

Posterior lumbar fusion: choice of approach and adjunct techniques

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

Hydroxyapatite-Based Biomaterials Versus Autologous Bone Graft in Spinal Fusion: An In Vivo Animal Study

STUDY DESIGN

An in vivo study was designed to compare the efficacy of biomimetic magnesium-hydroxyapatite (MgHA) and of human demineralized bone matrix (HDBM), both dispersed in a mixture of biomimetic MgHA nanoparticles, with that of an autologous bone graft.

OBJECTIVE

The objective of this study was to evaluate 2 new bone substitutes as alternatives to a bone autograft for spinal fusion, determining their osteoinductive and osteoconductive properties, and their capacity of remodeling, using a large animal model.

SUMMARY OF BACKGROUND DATA

Spinal fusion is a common surgical procedure and it is performed for different conditions. A successful fusion requires potentially osteogenic, osteoinductive, and osteoconductive biomaterials.

METHODS

A posterolateral spinal fusion model involved 18 sheep, bilaterally implanting test materials between the vertebral transverse processes. The animals were divided into 2 groups: 1 fusion level was treated with MgHA (group 1) or with HDBM-MgHA (group 2). The other fusion level received bone autografts in both groups.

RESULTS

Radiographical, histological, and microtomographic results indicated good osteointegration between the spinous process and the vertebral foramen for both materials. Histomorphometry revealed no significant differences between MgHA and autologous bone for all the parameters examined, whereas significantly lower values of bone volume were observed between HDBM-MgHA and autologous bone. Moreover, the normalization of the histomorphometric data with autologous bone revealed that MgHA showed a significantly higher value of bone volume and a lower value of trabecular number, more similar to autologous bone than HDBM-MgHA.

CONCLUSION

The study showed that the use of MgHA in an ovine model of spinal fusion led to the deposition of new bone tissue without qualitative and quantitative differences with respect to new bone formed with autologous bone, whereas the HDBM-MgHA led to a reduced deposition of newly formed bone tissue.

LEVEL OF EVIDENCE

N/A.

Static versus vacuum cell seeding on high and low porosity ceramic scaffolds

An adequate cell seeding technique is essential for effective bone regeneration on cell seeded constructs of porous tricalcium phosphates. In previous studies, dynamic cell seeding, in which an external force is applied to seed cells on a biomaterial, resulted in more homogeneous cell seeding in low porosity scaffolds than static seeding. The optimal cell seeding technique for high porosity scaffolds has not been defined yet. Human mesenchymal stem cells were isolated from bone marrow and characterized. The cells were seeded on low porosity (45%) and high porosity (90%) tricalcium phosphate scaffolds using a static and a vacuum seeding technique. LIVE/DEAD® staining of the cell-scaffold complexes followed by confocal laser scanning microscopy was used to measure cell proliferation, cell distribution and cell viability one, three and seven days after seeding. Cell proliferation was also quantified using a DNA quantification assay. Neither static nor vacuum seeding resulted in homogeneous cell seeding on both low and high porosity scaffolds. Cell density was lower on the inside than on the outside of the scaffolds. On low porosity scaffolds, the vacuum method yielded the highest numbers of cells compared to the static method. Low porosity scaffolds were seeded most homogeneously using the static seeding method. Seven days after seeding, numbers of adherent cells were comparable for both scaffold types and independent of the cell seeding technique used. In conclusion, on high porosity scaffolds, static seeding results in more homogeneous cell seeding and it is easier to use than a vacuum seeding technique.

Effect of a β-TCP collagen composite bone substitute on healing of drilled bone voids in the distal femoral condyle of rabbits

In this study, we tested the performance and biocompatibility of a composite of β-tricalcium phosphate (β-TCP) to collagen as a bone void filler (Cerasorb(®) Ortho Foam) in a rabbit distal femoral condyle model. β-TCP is a completely resorbable synthetic calcium phosphate and the addition of a collagen matrix couples the osteoconductive effects of the two components. Furthermore, the malleable properties of the implant material during surgical applications for shape control will be enhanced. A critical size defect of 6 mm in diameter and 10 mm in depth was drilled into each distal femur of the rabbits. One hole was filled with the test substance and the other was left empty for control. After 1, 3, and 6 months the animals were killed and the degree of bone healing analyzed. In total, 18 animals were investigated. When the β-TCP composite was used, histological, histomorphometric, and biomechanical evaluations revealed significantly better bone healing in terms of quantity and quality of the newly formed bone. Moreover, no signs of inflammation were observed in the animals and no allergic or foreign body reaction was noted. This suggests high biocompatibility and osteoconductivity of the investigated material to a bone void in an immune responsive species.

Bone graft substitutes currently available in orthopaedic practice: the evidence for their use

We reviewed 59 bone graft substitutes marketed by 17 companies currently available for implantation in the United Kingdom, with the aim of assessing the peer-reviewed literature to facilitate informed decision-making regarding their use in clinical practice. After critical analysis of the literature, only 22 products (37%) had any clinical data. Norian SRS (Synthes), Vitoss (Orthovita), Cortoss (Orthovita) and Alpha-BSM (Etex) had Level I evidence. We question the need for so many different products, especially with limited published clinical evidence for their efficacy, and conclude that there is a considerable need for further prospective randomised trials to facilitate informed decision-making with regard to the use of current and future bone graft substitutes in clinical practice.

A prospective comparative study of radiological outcomes after instrumented posterolateral fusion mass using autologous local bone or a mixture of beta-tcp and autologous local bone in the same patient

BACKGROUND

We previously reported a retrospective analysis of radiographic changes in instrumented posterolateral fusion mass (PLF) established using a mixture of local autologous bone and beta tricalcium phosphate (b-TCP) in lumbar spinal fusion surgery. Here, we report a prospective study to compare the use of local bone and a mixture of local bone and b-TCP in PLF in degenerative spinal surgery.

METHODS

Radiological changes in the PLF mass in 42 patients were analyzed for 12 months. All patients had degenerative lumbar spinal disease and underwent instrumented fusion. Local autologous bone was used for PLF on the left side, and a mixture of local autologous bone and b-TCP was used for PLF on the right side. Lumbar spinal anterior-posterior (AP) images were performed immediately postoperative and at 1, 3, 6, and 12 months. Computed tomography (CT) was also done immediately postoperative and at 12 months. Fusion rate, radiodensity, and the dimensions of the PLF mass bilaterally on the AP X-ray were compared. The change in volume in both fusion bridges in the CT image was also compared.

RESULTS

The overall fusion rates were 31/42 (73.8 %) and 24/42 (57.1 %) on the left and right sides, respectively. The decrease in radiodensity at 1 month postoperative was significantly greater on the left side than on the right side (from 0.79 to 0.74 versus from 0.81 to 0.78; p = 0.002). The mean immediate postoperative volume on the left side measured with CT was 5.1 cc (95 % CI, 4.94-5.34) and on the right side was 5.2 cc (95 % CI, 4.97-5.37). The mean volume at 12 months had decreased to 2.2 cc (95 % CI, 1.85-2.64) on the left side and 1.87 cc (95 % CI, 1.48-2.67) on the right side. The volume decrease on the right side was statistically greater than on the left side (p = 0.048).

CONCLUSIONS

Based on the changes in radiodensity and fusion rate during follow-up, local bone seems to undergo earlier resorption and stabilization than the mixture of local bone and b-TCP..

Improving the clinical evidence of bone graft substitute technology in lumbar spine surgery

Bone graft substitutes have been used routinely for spine fusion for decades, yet clinical evidence establishing comparative data remains sparse. With recent scrutiny paid to the outcomes, complications, and costs associated with osteobiologics, a need to improve available data guiding efficacious use exists. We review the currently available clinical literature, studying the outcomes of various biologics in posterolateral lumbar spine fusion, and establish the need for a multicenter, independent osteobiologics registry.

Silicate-substituted calcium phosphate ceramic bone graft replacement for spinal fusion procedures

STUDY DESIGN

Retrospective study.

OBJECTIVE

To assess the clinical and radiographical outcomes in spinal fusion procedures using silicate-substituted calcium phosphate (Si-CaP).

SUMMARY OF BACKGROUND DATA

Si-CaP is a newer-generation synthetic ceramic designed to maximize osteoinduction and osteoconduction.

METHODS

This is a retrospective analysis of a prospectively collected patient database including 108 patients (204 individual spinal levels). Different surgical procedures performed included 25 anterior cervical discectomy and fusions, 17 posterior cervical fusions, 7 combined anterior and posterior cervical fusions, 10 thoracic fusion surgeries, 18 transforaminal lumbar interbody fusions with 12 axial lumbar interbody fusions, 11 transpsoas discectomy and fusions, and 8 combined thoracolumbar fusion procedures. Si-CaP was used as bone extender without any additional graft material, bone marrow aspirate, or bone morphogenetic protein. Clinical outcomes were assessed using the visual analogue scale (VAS), Oswestry Disability Index, and Neck Disability Index. Fusion was determined by the presence of bony bridging on 2 consecutive sections in at least 2 planes on computed tomographic imaging.

RESULTS

At a follow-up of 12 (± 4.7) months, 90% of all patients demonstrated radiographical fusion. Fusion rates were highest in the cervical spine (97%) followed by thoracic and lumbar spines (86% and 81%, respectively). There were significant improvements in all clinical outcome measures-Oswestry Disability Index, 11.1 (± 10.2) and Neck Disability Index, 9.0 (± 11.4); VAS-back, 3.1(± 3.0); VAS-leg, 3.5 (± 3.6); VAS-neck, 3.7 (± 2.5); and VAS-arm 4.0 (± 3.2). There was no radiographical loosening of instrumentation due to infection or nonunion in this series, and no subsequent revisions for nonunion were required.

CONCLUSION

Si-CaP is an alternative to autogenous bone graft in spinal arthrodesis procedures. At 12-month follow-up, we detected high levels of bony fusion using Si-CaP in combination with various surgical spinal techniques.

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

STUDY DESIGN

A systematic review.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

Spontaneous C1 anterior arch fracture as a postoperative complication of foramen magnum decompression for Chiari malformation type 1

BACKGROUND

C1 fracture accounts for 2% of all spinal column injuries and 10% of cervical spine fractures, and is most frequently caused by motor vehicle accidents and falls. We present a rare case of C1 anterior arch fracture following standard foramen magnum decompression for Chiari malformation type 1.

CASE DESCRIPTION

A 63-year-old man underwent standard foramen magnum decompression (suboccipital craniectomy and C1 laminectomy) under a diagnosis of Chiari malformation type 1 with syringomyelia in June 2009. The postoperative course was uneventful until the patient noticed progressive posterior cervical pain 5 months after the operation. Computed tomography of the upper cervical spine obtained 7 months after the operation revealed left C1 anterior arch fracture. The patient was referred to our hospital at the end of January 2010 and C1-C2 posterior fusion with C1 lateral mass screws and C2 laminar screws was carried out in March 2010. Complete pain relief was achieved immediately after the second operation, and the patient resumed his daily activities.

CONCLUSION

Anterior atlas fracture following foramen magnum decompression for Chiari malformation type 1 is very rare, but C1 laminectomy carries the risk of anterior arch fracture. Neurosurgeons should recognize that fracture of the atlas, which commonly results from an axial loading force, can occur in the postoperative period in patients with Chiari malformation.

Calcium orthophosphates: occurrence, properties, biomineralization, pathological calcification and biomimetic applications

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided.

The state of lumbar fusion extenders

STUDY DESIGN

Review of literature.

OBJECTIVE

To evaluate the available literature supporting the use of lumbar fusion extenders in clinical practice.

SUMMARY OF BACKGROUND DATA

Because of the morbidity associated with the harvest of autologous iliac crest bone grafts, the search for lumber fusion extenders and replacements has accelerated. Many formulations of lumbar fusion extenders have been developed, and it is essential to evaluate clinical literature and available outcome metrics of these extenders.

METHODS

A review of English-language literature was performed between 1990 and January of 2010 for all literature presenting clinical outcomes of lumbar fusion extenders. After controlling for inclusion and exclusion criteria and assigning levels of evidence, 19 clinical studies were fully reviewed including those for demineralized bone matrix, recombinant human bone morphogenetic protein 2 (rhBMP-2), β-tricalcium phosphate, and calcium sulfate.

RESULTS

The most extensively studied of the lumbar fusion extenders is β-tricalcium phosphate, especially with regard to its use in adolescent scoliosis correction. The use of rhBMP-2 and demineralized bone matrix is supported only by two and three clinical studies, respectively. Calcium sulfate and other miscellaneous extenders are not conclusively or consistently supported by available clinical studies.

CONCLUSION

Calcium phosphate is the most supported of the lumbar fusion extenders. rhBMP-2 and demineralized bone matrix are supported by smaller bodies of evidence. These formulations are supported by these initial studies but in some cases need to be better examined with regard to side effect profiles.

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

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

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

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

Efficacy of silicate-substituted calcium phosphate ceramic in posterolateral instrumented lumbar fusion

STUDY DESIGN/SETTING

Retrospective review of a consecutive, nonrandomized series operated on by 2 surgeons.

OBJECTIVE

To evaluate the clinical and radiographic effectiveness of a silicated hydroxyapatite ceramic as a bone graft substitute in a series of patients undergoing posterolateral instrumented lumbar fusion.

SUMMARY OF BACKGROUND DATA

Newer-generation synthetic ceramics have been refined to maximize their host-graft interaction and stimulation of new tissue formation, including silicate-substitution.

METHODS

An independent radiologist interpreted the computed tomography images at 6, 12, and 24 months after surgery. Forty-two patients with 1- or 2-level lumbar degenerative disorders underwent posterior laminectomy (when indicated) and posterolateral fusion with instrumentation. Surgical levels included 15 patients who underwent 2-level and 27 single-level fusion procedures (57 levels operated on in total).

RESULTS

The average back pain scores improved from 5.6 ± 2.5 preoperative to 2.1 ± 2.5 at follow-up (P < 0.05). Similar results were seen with leg pain improvement from 5.8 ± 2.5 to 1.4 ± 1.9 (P < 0.05). At 6 months, 35% of levels revealed fusion, which increased to 76.2% and 76.5% at 12 and 24 months, respectively. No evidence of ectopic bone formation or osteolysis was noted.

CONCLUSION

In this study, a silicated calcium phosphate-based ceramic has been shown to be effective as a graft substitute and eliminate the need for autogenous iliac crest bone graft. The results confirm radiographic healing in posterolateral instrumented lumbar fusion at 24-months follow-up. The clinical outcomes also substantiate significant pain improvement consistent with published data in the literature compared with other bone graft alternatives.

Bone grafting options for lumbar spine surgery: a review examining clinical efficacy and complications

Background

Iliac crest harvest has been considered the “gold standard” at producing successful arthrodesis of the lumbar spine but is also associated with many donor-site morbidities. Many alternatives have been used to avoid iliac crest harvest, including autologous bone from other donor sites, allogeneic bone, ceramics, and recombinant human bone morphogenetic proteins (rhBMPs). This review will highlight the properties and preparations of these graft types and their potential complications and reported clinical efficacy.

Methods

A Medline search was conducted via PubMed by use of the following terms in various combinations: lumbar fusion, freeze-dried allograft, fresh-frozen allograft, autograft, iliac crest, demineralized bone matrix, rhBMP-2, rhBMP-7, scoliosis, bone marrow aspirate, HEALOS, coralline hydroxyapatite, beta tricalcium phosphate, synthetic, ceramics, spinal fusion, PLF, PLIF, ALIF, and TLIF. Only articles written in English were assessed for appropriate material. Related articles were also assessed depending on the content of articles found in the original literature search.

Conclusions

Although iliac crest remains the gold standard, reported success with alternative approaches, especially in combination, has shown promise. Stronger evidence with limited sources of potential bias is necessary to provide a clear picture of their clinical efficacy.