Demineralized Bone Matrix in Spine Surgery: A Review of Current Applications and Future Trends.

BACKGROUND: Graft augmentation for spinal fusion is an area of continued interest, with a wide variety of available products lacking clear recommendations regarding appropriate use. While iliac crest autograft has long been considered the "gold standard", suboptimal fusion rates along with harvest-related concerns continue to drive the need for graft alternatives. There are now multiple options of products with various characteristics that are available. These include demineralized bone matrix (DBM) and demineralized bone fibers (DBF), which have been used increasingly to promote spine fusion. The purpose of this review is to provide an updated narrative on the use of DBM/DBF in spine surgery. METHODS: Literature review. RESULTS: The clinical application of DBM in spine surgery has evolved since its introduction in the mid-1900s. Early preclinical studies demonstrated its effectiveness in promoting fusion. When used in the cervical, thoracic, and lumbar spine, more recent clinical data suggest similar rates of fusion compared with autograft, although clinical studies are primarily limited to level III or IV evidence with few level I studies. However, significant variability in surgical technique and type of product used in the literature limits its interpretation and overall application. CONCLUSIONS: DBM and DBF are bone graft options in spine surgery. Most commonly used as graft extenders, they have the ability to increase the volume of traditional grafting techniques while potentially inducing new bone formation. While the literature supports good fusion rates when used in the lumbar spine and when used with adjuvant cages or additional grafting techniques in the cervical spine, care should be taken when using as a stand-alone product. As new literature emerges, DBM and DBF can be a useful method in a surgeon's armamentarium for fusion-based procedures.

Analysis and modeling of coolants and coolers for specimen transportation.

Maintaining cold chain while transporting medical supplies and samples is difficult in remote settings. Failure to maintain temperature requirements can lead to degraded sample quality and inaccuracies in sample analysis. We performed a systematic analysis on different types of transport coolers (polystyrene foam, injection-molded, and rotational molded) and transport coolants (ice, cold packs, frozen water bottles) frequently in use in many countries. Polystyrene foam coolers stayed below our temperature threshold (6°C) longer than almost all other types of coolers, but were not durable. Injection-molded coolers were durable, but warmed to 6°C the quickest. Rotational molded coolers were able to keep temperatures below our threshold for 24 hours longer than injection molded coolers and were highly durable. Coolant systems were evaluated in terms of cost and their ability to maintain cold temperatures. Long lasting commercial cold packs were found to be less cost effective and were below freezing for the majority of the testing period. Frozen plastic water bottles were found to be a reusable and economical choice for coolant and were only below freezing briefly. Finally, we modeled the coolers performance at maintaining internal temperatures below 6°C and built a highly accurate linear model to predict how long a cooler will remain below 6°C. We believe this data may be useful in the planning and design of specimen transportation systems in the field, particularly in remote or resource limited settings.

Quantification of ricin, RCA and comparison of enzymatic activity in 18 Ricinus communis cultivars by isotope dilution mass spectrometry.

The seeds of the Ricinus communis (Castor bean) plant are the source of the economically important commodity castor oil. Castor seeds also contain the proteins ricin and R. communis agglutinin (RCA), two toxic lectins that are hazardous to human health. Radial immunodiffusion (RID) and the enzyme linked immunosorbent assay (ELISA) are two antibody-based methods commonly used to quantify ricin and RCA; however, antibodies currently used in these methods cannot distinguish between ricin and RCA due to the high sequence homology of the respective proteins. In this study, a technique combining antibody-based affinity capture with liquid chromatography and multiple reaction monitoring (MRM) mass spectrometry (MS) was used to quantify the amounts of ricin and RCA independently in extracts prepared from the seeds of eighteen representative cultivars of R. communis which were propagated under identical conditions. Additionally, liquid chromatography and MRM-MS was used to determine rRNA N-glycosidase activity for each cultivar and the overall activity in these cultivars was compared to a purified ricin standard. Of the cultivars studied, the average ricin content was 9.3 mg/g seed, the average RCA content was 9.9 mg/g seed, and the enzymatic activity agreed with the activity of a purified ricin reference within 35% relative activity.

Comprehensive laboratory evaluation of a specific lateral flow assay for the presumptive identification of abrin in suspicious white powders and environmental samples.

Abrin is a heterodimeric toxin present in the seeds of the Abrus precatorius plant. The easily obtainable seeds can yield a highly toxic product that can be used in various types of biocrimes and terrorism-related activities, including "white-powder" letters. Although the vast majority of these threats are hoaxes, the lack of rapid and reliable detection assays for abrin, such as lateral flow assays (LFAs), can be an impediment to accurate and rapid hazard assessment. One of the complicating factors associated with LFAs is the use of antibodies of poor affinity and specificity that cross-react with near neighbors or that bind to plant lectins, which are capable of nonspecifically cross-linking the capture and detector antibodies. Because of the critical need to promote public safety and public health, we conducted a comprehensive laboratory evaluation of a commercial LFA for the rapid detection of abrin. This study was conducted using comprehensive inclusivity and exclusivity panels of abrin and near-neighbor plant materials, along with panels of lectins, related proteins, white powders, and environmental background material, to determine the sensitivity, specificity, limit of detection, dynamic range, and repeatability of the assay for the specific intended use of evaluating suspicious white powders and environmental samples for the presumptive presence of abrin.

The relative safety and efficacy of abciximab and eptifibatide in patients undergoing primary percutaneous coronary intervention: insights from a large regional registry of contemporary percutaneous coronary intervention.

OBJECTIVES: This study sought to assess whether the use of eptifibatide instead of abciximab is associated with a difference in outcomes of patients undergoing primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI). BACKGROUND: Pooled data from randomized controlled trials suggest that the use of abciximab may be associated with a survival advantage in patients undergoing primary PCI for acute STEMI. However, a large proportion of patients in the community are treated with eptifibatide, an agent that shares some but not all pharmacological properties with abciximab. METHODS: We evaluated the outcomes of 3,541 patients who underwent primary PCI for STEMI from October 2002 to July 2006 in a large regional consortium and who were treated with abciximab (n = 729) or with eptifibatide (n = 2,812). RESULTS: There was no difference in the incidence of in-hospital death (4.1% with abciximab vs. 3.5% with eptifibatide, p = 0.39), recurrent myocardial infarction (0.8% vs. 1.2%, p = 0.42), or stroke/transient ischemic attack (0.7% vs. 0.6%, p = 0.80). There was no difference in the need for blood transfusion (12.4% vs. 11.7%, p = 0.61), whereas there was a greater incidence of gastrointestinal bleeding with abciximab (4.8% vs. 2.8%, p = 0.01). In parsimonious risk-adjusted models, no significant difference between abciximab and eptifibatide was observed with respect to any of the outcomes measures. CONCLUSIONS: Currently, eptifibatide is used as the adjunct antiplatelet agent in the majority of patients undergoing primary PCI. There is no apparent difference in early outcomes of patients treated with eptifibatide compared with patients treated with abciximab.

Temporal trends, safety, and efficacy of bivalirudin in elective percutaneous coronary intervention: insights from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium.

OBJECTIVE: To evaluate the safety and efficacy of bivalirudin based therapy among patients undergoing percutaneous coronary intervention (PCI) for stable coronary artery disease in a large multicenter registry. BACKGROUND: The REPLACE I trial demonstrated the non-inferiority of a strategy of bivalirudin compared with heparin and glycoprotein (GP) IIbIIIa inhibition in patients undergoing PCI. There is a paucity of outcome data with bivalirudin use in the setting of real-world PCI practice. METHODS: We evaluated the outcome of 11,719 patients who underwent elective PCI for stable coronary artery disease (CAD) from 2002 to 2004 in a large regional consortium, and who were treated with bivalirudin (n = 2051) or with heparin and GP IIbIIIa inhibitors (n = 9,668). The primary endpoints were transfusion and in-hospital major adverse cardiovascular events (MACE) defined as the composite of death, MI, stroke, and any coronary artery bypass grafting (CABG) or target lesion revascularization. RESULTS: Compared with patients who received heparin plus GP IIbIIIa inhibitors, patients who received bivalirudin had a similar incidence of post-procedural MI, stroke, in-hospital death, MACE (2.88 vs. 2.48, P = 0.30), or transfusion (2.83% vs. 2.41%, P = 0.27). Patients at greater risk of bleeding were more likely to be treated with bivalirudin. After adjusting for the propensity to receive bivalirudin and for baseline co-morbidities, there was no difference in the odds of MACE or the need for transfusion between the two groups. CONCLUSION: Compared with heparin plus GP IIbIIIa inhibition, use of bivalirudin in patients undergoing PCI for stable CAD is associated with similar ischemic and bleeding complications. Given the ease of administration and lower cost, bivalirudin provides an attractive treatment option in this patient population.

Coronary artery rupture during balloon angioplasty, rescued with localized thrombin injection and coil embolization.

Distal intracoronary thrombin injection has been used successfully to seal very small, guidewire related, coronary artery perforations during percutaneous coronary intervention. This case report expands upon this therapeutic approach, by describing the use of high dose distal thrombin injection for the successful (non-surgical) management of balloon-induced coronary artery rupture, with an intrapericardial leak.

Injectable biomaterials and vertebral endplate treatment for repair and regeneration of the intervertebral disc.

The objectives of augmentation of the nucleus pulposus following disc removal are to prevent disc height loss and the associated biomechanical and biochemical changes. Flowable materials may be injected via a small incision, allowing minimally invasive access to the disc space. Fluids can interdigitate with the irregular surgical defects and may even physically bond to the adjacent tissue. Injectable biomaterials allow for incorporation and uniform dispersion of cells and/or therapeutic agents. Injectable biomaterials have been developed that may act as a substitute for the disc nucleus pulposus. Our work has focused on the evaluation of a recombinant protein copolymer consisting of amino acid sequence blocks derived from silk and elastin structural proteins as an injectable biomaterial for augmentation of the nucleus pulposus. This implant, NuCoretrade mark Injectable Nucleus is being developed by Spine Wave (Shelton, CT). The NuCoretrade mark material is comprised of a solution of the protein polymer and a polyfunctional cross-linking agent. The material closely mimics the protein content, water content, pH and complex modulus of the natural nucleus pulposus. Extensive mechanical testing, biocompatibility and toxicology testing have been performed on the material. Characterization studies indicate that the NuCoretrade mark Injectable Nucleus is able to restore the biomechanics of the disc following a microdiscectomy. Extensive biomaterial characterization shows the material to be non-toxic and biocompatible. The mechanical properties of the material mimic those of the natural nucleus pulposus. Thus NuCoretrade mark Injectable Nucleus is suitable to replace the natural nucleus pulposus following a discectomy procedure. Human clinical evaluation is underway in a multi center clinical study on the use of the material as an adjunct to microdiscectomy. Further clinical studies of the use of NuCoretrade mark Injectable Nucleus for treatment of early stage degenerative disc disease are planned in the near future. On-going efforts are characterizing the use of the material as a cell delivery vehicle for disc repair and reconstruction. Related development efforts are exploring methods for repair and regeneration of the cartilage endplate that are implemented to enhance the host-implant interface. Prior to the introduction of the above-mentioned biomaterial, our work proposes to utilize a process for the treatment of the vertebral endplates. The goal of this process is to restore the endplates as closely as possible to their natural state prior to disease or degeneration. The nature of the treatment will depend upon the form of the endplate degeneration and on the type of scaffolding that is intended to be introduced in the nuclear cavity. Endplate therapy is a potential means of enhancing biomaterial integration and cell survival, but remains a long-term and currently untested methodology.

Experimental efficacy of an everolimus eluting cobalt chromium stent.

INTRODUCTION: Rapamycin and its analogs are now being coated on different stent platforms, using different polymer matrices to prevent restenosis by impairing vascular smooth muscle cell proliferation and neointimal formation. METHODS: We evaluated the feasibility and compared the efficacy of biostable polymeric everolimus and sirolimus (CYPHER, Cordis) eluting stents in a porcine coronary model. Cobalt chromium balloon expandable stents (ML VISION, Guidant) were coated with a polymer containing everolimus (190 mug/cm(2)). Twelve pigs underwent placement of 36 oversized sirolimus (n = 12), everolimus (n = 12), and bare metal (cobalt chromium, n = 12) stents in the coronary arteries. RESULTS: At day 28, vessel injury scores were low (<0.25) and similar between each of the three test groups. The mean neointimal thickness was significantly lower in the everolimus- (0.13 +/- 0.07 mm, P = 0.02) and sirolimus-eluting stents (0.13 +/- 0.08 mm, P = 0.04) versus the bare metal stents (0.20 +/- 0.07 mm). The mean percent area stenosis was similar for the everolimus-eluting stents [(20.8 +/- 6.9)%] and the sirolimus-eluting stents [(20.8 +/- 7.6)%], and each was significantly less than that of bare metal stents [(26.1 +/- 7.8)%, P = 0.05]. CONCLUSION: Stent-based delivery of sirolimus and everolimus delivered via durable polymeric matrices are equally effective in the suppression of neointimal formation at day 28 in the porcine coronary model. Further study is necessary to document dose response and long-term comparative effects of these drug-eluting stents.

The use of multiple coronary guidewires to occupy secondary branch vessels and facilitate PCI of a complex aneurysmal stenosis.

Percutaneous revascularization of complex coronary stenosis is dependent on establishing suitable guidewire position in the vascular bed distal to the lesion. We report the use of multiple 0.0014'' coronary guidewires to occupy unintended branch vessels and to facilitate PCI of a high-grade left circumflex obtuse marginal branch lesion with post-stenotic aneurysmal dilation of the vessel and multiple branch vessels. This technique enabled successful placement of a nitinol hydrophilic-coated wire into the distal vascular bed beyond the region of obstruction followed by placement of a drug-eluting stent with restoration of luminal dimensions and TIMI-3 angiographic flow.

Segmental vessel wall shear stress and neointimal formation after sirolimus-eluting stent implantation: physiological insights in a porcine coronary model.

BACKGROUND: Low vessel-wall shear stress promotes atherosclerosis and restenosis. We conducted serial analysis of vessel-wall shear stress following placement of metal and sirolimus (SRL) stents to determine the relationship between shear stress and neointima. METHODS: Serial quantitative coronary angiography, intracoronary ultrasound (IVUS), and Doppler flow analysis were performed at baseline, immediately poststent, and at 30 and 90 days on 16 stents (metal, n = 8; SRL, n = 8) implanted in the coronary arteries of eight miniswine. Segmental vessel-wall shear stress (dyn/cm2) was calculated at 10 sections within the stent and normalized to the average proximal and distal reference vessel shear stress using IVUS and hyperemic average peak flow velocity. At 90 days, histological analysis was completed to determine vessel-wall morphometry on corresponding sections from each stent. RESULTS: Stent placement resulted in a similar degree of in-stent stenosis (-5% to 25%) and immediate post-in-stent shear stress. At 30 days, the IVUS neointimal cross-sectional area and percentage of area stenosis were significantly less in SRL (1.2+/-0.8 mm2; 12.7+/-8.5%) versus metal stents (2.3+/-0.4 mm2; 28.2+/-3.4%, P < .003). In-stent normalized shear stress was less for SRL (0.93+/-0.07) versus metal (1.07+/-0.08, P = .002) stents. At 90 days, the mean neointimal area was similar for the SRL (2.50+/-0.47 mm2) and metal stents (2.72+/-1.15 mm2). Linear regression documented a negative correlation between poststent shear stress and neointima for metal stents (r = .61, P < .0001). In the SRL stents, however, the post-in-stent shear stress had a positive correlation with neointima (r = .40, P = .0002). CONCLUSIONS: The placement of oversized stents causes alteration of segmental vessel-wall shear stress, which appears to be an important physiological stimulus for neointimal formation, and may influence the pharmacodynamics of SRL-eluting stent in the porcine coronary model.

Stent-based delivery of ABT-578 via a phosphorylcholine surface coating reduces neointimal formation in the porcine coronary model.

Stent-based delivery of the antiproliferative and immunosuppressive macrocyclic lactone sirolimus reduces neointimal formation and restenosis by cytostatic inhibition of vascular smooth muscle cell proliferation. The objective of this study was to determine the feasibility and efficacy of stent-based delivery of ABT-578, a structurally unique macrocyclic lactone. Stainless steel balloon-expandable stents were coated with thin layer of phosphorylcholine (PC) or PC with ABT-578 (10 microg/mm). Fifteen juvenile domestic pigs underwent placement of oversized bare metal (n = 15), PC (n = 8), and PC with ABT-578 (n = 9) stents in the coronary arteries. At 28 days, histology demonstrated similar mean injury scores for the control, PC-, and ABT-578-coated stents. The mean neointimal area (mm2) was significantly reduced for ABT-578 (1.70 +/- 0.47) as compared with PC (2.82 +/- 1.24) and control (2.89 +/- 1.91) stents (P < or = 0.05). The 40% reduction in neointimal area resulted in significantly less mean percent diameter stenosis for ABT-578 (19.4% +/- 4.0%) as compared with PC (30.3 +/- 12.1 %) and control (29.4% +/- 15.5%) stents (P < or = 0.03). Twelve of the 45 bare metal stent cross-sections (26.7%) exhibited a giant cell reaction, while none of the sections from the ABT-578-eluting stents had a giant cell reaction (P = 0.004). Stent-based delivery of ABT-578 via a PC surface coating inhibits neointimal formation at 28 days in the porcine coronary model. Further study is necessary to determine the dose-response and long-term effects ABT-578-eluting stents in the porcine coronary model.

Impact of frame selection on quantitative coronary angiographic analysis after coronary stenting.

This study examined the impact of frame selection on the results of quantitative coronary angiographic analysis (QCA). Thirty-nine patients who had stent implantation and a follow-up angiogram 5-7 months later were studied using the CMS Medis QCA system. The acute and follow-up films (n = 39) were read in three different ways to assess the impact of frame selection: frame chosen making the stent appear least narrowed (best); frame chosen making the stent appear most narrowed (worst); and measurement from the mean value from three consecutive end-diastolic frames (core). We measured the mean percent diameter stenosis immediately postintervention and at follow-up, the binary restenosis rate, and the late lumen loss (mm). There was a statistically significant difference in all of these variables when comparing the three methods of frame selection (best vs. worst, P values < 0.001; best or worst vs. core, P values < 0.01). This study demonstrates a marked variability in the results obtained using QCA to measure the acute and late coronary stent outcomes when operators have the ability to select which frame to analyze (frame bias).

Long-term effects of polymer-based, slow-release, sirolimus-eluting stents in a porcine coronary model.

BACKGROUND: Stent-based delivery of sirolimus (SRL) has shown reduction in neointimal hyperplasia and restenosis. The purpose of this study was to evaluate the chronic vascular response and the expression of cell cycle regulators after SRL-eluting stent implantation in a porcine coronary model. METHODS: Forty-nine pigs underwent placement of 109 oversized stents (control, n=54, SRL (140 microg/cm(2)), n=55) in the coronary arteries with histologic analysis and Western blot (PCNA, p27(kip1), CD45, MCP-1, IL-2, IL-6, TNF-beta) at 3, 30, 90 or 180 days. RESULTS: At 3 days, the mean thrombus area was similar for control (0.38+/-0.19 mm(2)) and SRL (0.29+/-0.09 mm(2)) stents. After 30 days, the mean neointimal area was significantly less for the SRL (1.40+/-0.35 mm(2)) versus the control stents (2.94+/-1.28 mm(2), p<0.001). At 90 and 180 days, the mean neointimal area was similar for the SRL (3.03+/-0.92 and 3.34+/-0.99 mm(2)) as compared with control stents (3.45+/-1.09 and 3.65+/-1.23 mm(2)). Western blot analysis demonstrated an increased expression of p27(kip1) in the vessel wall at 90 days for the SRL versus control stents (p=0.05) but with increased levels of PCNA in the SRL as compared with control stents (p=0.003). CONCLUSION: SRL-eluting stents favorably modulate neointimal formation for 30 days in the porcine coronary model. Long-term inhibition of neointimal hyperplasia is not sustained presumably due to delayed cellular proliferation despite increased levels of the cyclin-dependent kinase p27(kip1) in the vessel wall.