Bulk Graft Research Articles

Efficient capture and detoxification of mercury dichloride from wastewater by a PVDF/PEI adsorption membrane

Poly(vinylidene fluoride) (PVDF), as one of the halogenated alkanes, has excellent membrane performance. Polyethyleneimine (PEI), with excellent chelating performance and strong alkalinity, could enable halogenated alkanes to produce active CC bonds, and subsequently, PEI can be grafted onto the CC sites in-situ. In this paper, a novel adsorption membrane (PVDF/PEI) was fabricated via a one-step bulk grafting reaction of branched PEI to PVDF networks by non-solvent-induced phase inversion. This membrane showed highly efficient removal of Hg(II) ions, where 97% of Hg(II) from 20 mL of simulated wastewater solution containing 400 mg/L Hg(II) was removed in just 30 min using 20 mg of the adsorbent. The Langmuir isotherm model fitted the adsorption process well and gave a maximum adsorption capacity of 1036 mg/g at 30 °C, which agreed with the experimental saturation adsorption capacity of 1023 mg/g, suggesting that all binding sites on the membrane were involved in adsorption. After adsorption, Hg(II) was reduced to Hg2Cl2 with low toxicity to generate the crystals with a regular shape. Mechanisms studies implied that the adsorption of Hg(II) onto PVDF/PEI was an integrated chemical process that involved chemical chelation and a redox reaction due to the strong interactions between the mercury atoms and the active sites on the membrane. This novel PVDF/PEI adsorption membrane was resistant to acid and alkali, and can be separated and recovered directly from aqueous by fishing out. To the best of our knowledge, this is the first time to report on a PEI-functionalized PVDF adsorption membrane for the efficient removal of Hg(II).

Ultra-selective chelating membranes for recycling of cobalt from lithium-ion spent battery effluents by electrodialysis

The recovery of valuable resources from spent effluents is critical to ensure sustainable growth and reduce commodity shortages at global levels. Spent batteries are largely untapped resources containing multiple high-value metal ions that may be harnest and resued indefinitely to develop a circular battery economy. Challenges however lay with the cost of purification and recovery strategies and the limited selectivity of existing processes. This work presents the development of selective cation exchange membranes suitable for the selective recovery of cobalt from mixtures of lithium, cobalt, and nickel from spent battery effluents. Efficient cation exchange membranes were generated by modifying poly(vinyl chloride) films with ethylene diamine followed by grafting of 5-chloro-8-hydroxyquinoline (5C8Q) chelating agents and two synthesis routes were compared including surface and bulk grafting and the membrane separation properties were benchmarked against CIMS Neosepta. Besides being stable across a pH range between 2 and 8, relevant to spent battery lixiviat, the surface grafted membranes exhibited the lowest energy of sorption in comparison to bulk membranes, which was ten times lower than that of the commercial CIMS Neosepta reference membranes. The transfer of ions from model single salt solutions across the surface grafted membranes allowed for over 60 % of cobalt recovery within 1 h, while nickel and lithium were transferred only up to 18 % and 0.2 %, respectively. In addition, the electrodialysis-based separation of multi-component solutions remained very cost-effective with cobalt ion removal amounts up to 58 %, leading to Co/Li separation factors as high as 247. This novel chelating agent strategy opens avenues for the development of highly efficient and selective membrane materials, which are able to operate in extreme pH environments and supporting ultra-selective ionic transfer.

Fabrication of S-PBI cation exchange membrane with excellent anti-fouling property for enhanced performance in electrodialysis

A novel anti-fouling cation exchange membrane (CEM) of sulfonated polybenzimidazole (S-PBI) was fabricated by the polymer bulk grafting modification of poly (4,4′-diphenyl ether-5,5′-bibenzimidazole) with sodium styrene sulfonate. FTIR, TGA, XPS, SEM and AFM were used to characterize membrane properties and the results showed that the ion exchange capacity and hydrophilicity of S-PBI increased with increased degrees of grafting and the electric resistance decreased accordingly. When the mass ratio of O-PBI/SSS was 1:4, the electric resistance of S-PBI-4.0 was 4.5 Ω·cm2, while the ion exchange capacity was 2.3 meq/g. The ED experiment with the S-PBI-4.0 membrane exhibited good desalination rate (>96 %), high current efficiency (80.73 %) and low energy consumption (1.13 kW·h/kg), which were very close to the results of a commercial CEM (Neosepta CMX). What's more, because of its good hydrophilicity, the S-PBI-4.0 membrane had better anti-fouling ability than Neosepta CMX, which was manifested as less resistance increase after membrane fouled by bovine serum albumin and smaller resistance after membrane cleaned by deionized water. These results demonstrate that the S-PBI-4.0 membrane is an appropriate candidate CEM and helpful to expand the application of ED in high-salinity organic industrial wastewater treatment.

Mid-term results in revision hip arthroplasty with impaction bone grafted cup reconstruction for acetabular defects

Acetabular defects are a challenging condition for surgeons in revision THA. A crucial aim is an anatomical restoration of the centre of rotation (COR) through grafts. The aim of this study was to determine the cup survival after biological restoration of acetabular defects in THA and the effect of Paprosky classification, age, BMI, and number of previous operations on cup survival. Retrospectively patients with a cup exchange and an impaction of cortico-cancellous or bulk grafts between 2009 and 2012 were included with a follow up with a minimum of 5 year. Implant failure was defined as radiographic loosening or explantation of the cup. The acetabular defect situation was classified to Paprosky. 82 patients (58 female 70.7%) were included. 26 patients were not available to contact. 56 patients (40 female 71.4%) remained for survival analysis with mean age of 75.6 ± 8 years. Survival of the cup after 5 years was 90% and after 7.8 years 88%. There was no difference in survival concerning defect classification, type of implant or graft, age, BMI, and number of previous operations. Patients on the follow up reached an HHS of 67.4 ± 19, a WOMAC Score of 33.4 ± 25.4 points and an unsatisfactory result in the SF-36. Impaction bone grafting of acetabular defects is a good option with satisfactory biomechanical results and survival for small defects. Predictive factors for cup survival could not be clarified in our study. So, the correct indication, knowing the limits of the methods and the correct choice of implant allow a defect-oriented approach and are decisive for the success of the operation.

Osteochondral Lesions of the Talus – A Biomechanical Explanation for Larger OLT Shoulder Lesions Leading to Increased Patient Risk

Category:Ankle, TraumaIntroduction/Purpose:Osteochondral lesions of the talus (OLT) are a common injury that can result in pain, disability, and risk ankle degeneration, with poor outcomes when not managed properly. Unconstrained ‘shoulder’ lesions on the medial edge of the talar dome present a particular challenge. The objective of this study was to assess the effect of increasing size of a medial OLT shoulder lesion on ankle joint contact mechanics and to determine a threshold size that would warrant bulk grafting of the defect. Our hypothesis is that larger defects will demonstrate increased pressure applied over a lesser surface area, with peak pressure progressing towards the rim of the defect, resulting in an increased risk for tissue damage and need for treatment.Methods:Nine cadaver ankle joints were dissected without disrupting the medial and lateral stabilizing ligaments. A Tekscan pressure sensor was inserted into the ankle joint. Intact specimens were axially compressed up to 800 N with the foot in neutral and again at 20° inversion, simulating ankle position during inversion injury. The specimens were then tested with progressively larger semicircular osteochondral lesions at diameters of 8, 10, 12, 14, and 16 mm that were centered on the edge of the medial talar dome, followed by a final ovoid lesion of 16x20 mm. After each lesion was created the specimens were retested. Linear mixed models adjusted for donor characteristics and assessed changes in peak pressure (MPa), contact area (mm2), peak pressure location (mm), and distance from peak pressure location to the lateral rim of the defect (mm) by defect size and ankle position.Results:For all defect sizes, mean peak pressures were significantly higher in inversion compared to neutral. Mean peak pressure magnitude progressively increased with defect size in both ankle positions. Donor characteristics did not significantly affect mean peak pressure. Contact area decreased in both positions as defect size increased, but inversion led to significantly lower contact areas than in neutral. In neutral positions, the location of peak pressure moved laterally on the talar dome but also moved closer to the defect rim as the size of the defect increased. The rim-peak pressure distance stabilized for defect sizes of 10 mm and above. In inversion, however, the rim-peak pressure distance remained unchanged at about 8 mm for all defect sizes.Conclusion:As OLT defect sizes increased, we observed an increase in peak pressure, a decrease in contact surface area, and a lateral translation of peak pressure location relative to the defect rim. Distance between location of peak pressure and defect rim decreased with neutral loading until a 10 mm defect but remained consistent in inversion loading. These findings suggest a biomechanical explanation for secondary injuries and treatment failures in larger OLT shoulder lesions due to maladaptive cartilage tissue on the dome of the talus. Larger defects (=10 mm) remain a critical point of interest with predictive clinical value for OLT outcomes.

Upcycling of polypropylene waste by surface modification using radiation-induced grafting

In this work, upcycling of polypropylene waste into amidoxime functionalized polypropylene adsorbent was studied using radiation-induced grafting technique. Polypropylene waste (PPw) was resulted from accelerated thermal ageing of polypropylene (PP). Bulk grafting of acrylonitrile (AN) onto PPw was achieved by simultaneous radiation grafting method using gamma rays. Degree of grafting of AN on PPw is affected by absorbed dose and dose rate. The acrylonitrile groups of grafted PPw were chemically converted into amidoxime functionality. Both the acrylonitrile-grafted PP waste and its amidoxime product were investigated by FTIR, XRD, SEM-EDX and TGA techniques. The prepared amidoxime adsorbent with amidoxime group density of 8.06mmol/g was used for removal of copper ions from aqueous solutions. The effects of various physicochemical conditions such as: solution pH, adsorbent content, initial metal ion concentration and time on adsorption were studied to maximize adsorption of metal ion. Pseudo-first-order, pseudo-second-order and intra-particle diffusion models were applied to study the kinetics of adsorption. Maximum Langmuir adsorption capacity of 208.3mg/g at pH 5.0 with optimum contact time of 120min was observed. Utilization of PP waste and its comparable adsorption capacity with existing radiation grafted polymer-based adsorbents provide a new, cheap and cost effective system.

Determination of structural femoral head allograft viability and integrity with a novel diagnostic tool: SPECT/CT. A preliminary study.

To evaluate the viability and integrity of fresh frozen bulk femoral head allografts obtained from the institutional bone bank that were used to reconstruct severe acetabular defects and to validate the SPECT/CT method which gives both anatomical and functional data for this purpose. We retrospectively reviewed 9 patients (6 female, 3 male; mean age 63.6 years). Preoperative and postoperative leg lengths, existence of the Trendelenburg sign, range of motion of the hip, visual analogue score (VAS), Harris Hip Score (HHS) and any complication were assesed at each follow-up. Radiographically, position of the cup, signs of loosening or migration, and union of the graft were all determined. At the latest follow-up, patients were evaluated with hybrid SPECT/CT. The average duration of follow-up was 38.1 months (24-50 months). The overall mean HHS and VAS scores were significantly improved (p<0.05). When hybrid SPECT/CT results were evaluated, the vascular phase of scintigraphy showed hyperaemia of the graft and the bone phase of scintigraphy showed normal or increased radiotracer uptake in the graft site in 7 patients. SPECT/CT images were used to determine the exact localisation of osteoblastic activity. 1 patient with minor resorption of the graft without clinical symptoms revealed mild osteoblastic activity. The patient who had no activity in the graft site was rerevised because of infection. Institutional bank allografts are still excellent options for treating large acetabular defects in revision total hip arthroplasty where trabecular metals are not available or in common use. The Hybrid SPECT/CT method is a reliable, noninvasive method for evaluating both the integrity and viability of a bulk graft in 3-D.

Reconstruction of the Shallow Acetabulum With a Combination of Autologous Bulk and Impaction Bone Grafting Fixed by Cement

BackgroundAcetabular bone deficiency, especially proximal and lateral deficiency, is a difficult technical problem during primary total hip arthroplasty (THA) in developmental dysplasia of the hip (DDH). We report a new reconstruction method using a medial-reduced cemented socket and additional bulk bone in conjunction with impaction morselized bone grafting (additional bulk bone grafting method).Questions/purposesIn a population of patients with acetabular dysplasia undergoing THA using a medial-reduced cemented socket and additional bulk bone with impacted morselized bone grafting, we evaluated (1) the radiographic appearance of bone graft; (2) the proportion of cups that developed loosening and subsequent revision; and (3) clinical results (outcome scores and complications).MethodsForty percent of 330 THAs for DDH performed at one center between 1999 and 2009 were defined as shallow dysplastic hips. The additional bulk bone grafting method was performed on 102 THAs with shallow acetabulum (31% for DDH) at one center between 1999 and 2009. We used this approach and technique for shallow acetabuli when a cup protruded from the lateral acetabular edge in preoperative templating. The other 132 dysplastic hips without bone grafting had THA performed at the same periods and served as a control. Acetabuli were defined as shallow when the depth was less than or equal to one-fifth of the pelvic height (cranial-caudal length on radiograph). The additional bulk bone grafting technique was as follows: the resected femoral head was sectioned at 1 to 2 cm thickness, and a suitable size of the bulk bone graft was placed on the lateral iliac cortex and fixed by poly-l-lactate absorbable screws. Autologous impaction morselized bone grafting, with or without hydroxyapatite granules, was performed along with the implantation of a medial-reduced cemented socket. We defined an “incorporated” graft as remodeling and trabeculation including rounding off of the protruding edge of a graft beyond the socket. Radiographic criteria used for determining loosening were migration or a continuous radiolucent zone between the prosthesis/bone cement and host bone. Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) and the Merle d’Aubigne and Postel score; complications were tallied from chart review. The followup was 10 ± 3 years (range, 6–15 years).ResultsOne acetabular component (1%) with severe shallow and steep acetabuli showed definite radiographic evidence of loosening and was revised. Clinically, the mean JOA score for the hips treated with additional bulk bone grafting THA in this study improved from 39 ± 10 points preoperatively to 95 ± 5 points postoperatively (p < 0.05, paired t-test). The mean Merle d’Aubigne and Postel score for the hips improved from 7 ± 2 points to 17 ± 1 points (p < 0.05, paired t-test). Complications included a Trendelenburg sign in one hip, dislocation in one, and transient partial sciatic nerve palsy in one. Within 3 years 6 months postoperatively, 101 of 102 additional bulk bone grafting cases showed successful bone remodeling and bone graft reorientation without collapse on radiographs. Partial resorption of the additional bone graft on the lateral side was observed in two hips (2%) with socket abduction angles of < 35°.ConclusionsAchieving stable acetabular fixation is often challenging in the dysplastic hip, especially shallow acetabulum, and a variety of techniques have been described. Early results of combining bulk graft with impaction of morselized graft are promising. Although each surgical technique was well established, further investigation for clinical results of a combination of these techniques might be necessary to confirm longer term outcomes.Level of EvidenceLevel IV, therapeutic study.

Fabrication and characterization of novel starch-grafted poly l-lactic acid/montmorillonite organoclay nanocomposites

In this work, poly(l-lactic acid)-g-starch layered silicate nanocomposites (NCs) (PLLA-g-starch/MMT) were fabricated by intercalative bulk graft copolymerization of LA with starch, in the presence of either stannous octoate acting as a catalyst or LA-MMT organoclay acting as a cocatalyst-nanofiller. This procedure was performed inside a custom vacuum micro-reactor. To better understand the graft copolymerization mechanism, in situ processing types, interfacial interactions and nanostructure formation of PLLA-g-starch/MMT NCs, methods such as FT-IR, XRD, 1H NMR, 13C CP/MAS-NMR, DSC/TGA, TEM and SEM were utilized. The morphology and thermal behaviors of nanocomposites were found to be strongly dependent on the loading mass fraction of LA-MMT within the nanocomposite structure and the type of in situ processing such as interfacial, physical and chemical interactions. Preintercalated LA-MMT organoclay exhibited dual functions. It demonstrated the ability to act as a catalyst, essentially accelerating in situ graft copolymerization via esterification of LA carboxyl groups with hydroxyl groups of starch macromolecules, whilst also acting as a nananofiller-compatibilizer.

Optimized synthesis of hydroxypropyl cellulose-g-poly(ε-caprolactone) network

The objective of this study was the synthesis of copolymer networks based on poly (e-caprolactone) (PCL), hydroxypropyl cellulose (HPC) and hexamethylene diisocyanate (HDI) via bulk graft copolymerization followed by crosslinking (using routes I and II), and subsequent optimization of the process by response surface methodology (RSM). The studied reaction parameters were: (i) monomer content (weight ratio of CL/HPC), (ii) amount of catalyst, and (iii) amount of crosslinker. FT-IR and 1H NMR results confirmed that the grafting of PCL onto HPC and subsequent crosslinking through terminal hydroxyl groups of PCL grafts by HDI were performed successfully. Through differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD), it was found that the crystallinity of grafted polymers depended on the amount of grafted PCL and degree of crosslinking. In modeling of the process using RSM, the coefficient of determination (R2) for the models (97.3 and 93.3 % for two routes) as well as the probability (p < 0.0001) revealed high significance of the regression models. Also it was found that the obtained systems possessed T m s between 42.94 and 54.57 °C (route I) and 32.49–46.30 °C (route II) that were tunable by the monomer content, catalyst and crosslinker amounts. RSM provided a useful tool to select in a fast way the proper experimental conditions to synthesize crossinked HPC-g-PCL copolymer as a novel biocompatible and biodegradable shape memory polymer with adjustable switching temperature and potential biomedical applications, which would be further studied in the future.

The value of bulk femoral head allograft in acetabular reconstruction using Kerboull-type plate.

This study investigated the mid- and long-term results of acetabular reconstruction using a KT plate with an allograft and showed the utility of filling the bony defect with bulk femoral head allograft rather than morselised allograft. We retrospectively investigated a consecutive series of 31 hips in 30 patients who underwent primary THA or revision THA between March 2002 and March 2012. Bulk grafts from femoral head allografts were used in 16 hips and morselised grafts were used in 15 hips. The mean follow-up period was 7.2 years (3-13 years). The acetabular bone defects were classified according to the American Academy of Orthopedic Surgeons grading system. Type II defects were present in five hips; 26 hips were type III. Radiological failure, defined as absolute error of the inclination of the KT plate >3°, breakage of the KT plate or screw, and/or absolute error of the vertical or horizontal migration of the femoral head >3 mm was found in 12 cases. All these complications appeared in the morselized group; there were no complications in the bulk group. The eight-year survival rate of morselised grafts was 52.5% and that of bulk grafts was 100%, using radiological loosening as an end point. We conclude that using bulk graft from femoral head allografts is necessary to achieve mechanically stable reconstruction for large acetabular bone defects.

Surgical tip: Titanium foam blocks can simplify fusion of failed total ankle replacements

Ankle arthrodesis following failed ankle replacements is a technically challenging task because of the large defect left behind after the prosthesis is removed. The usual practice is to use bulk grafts which are either autografts or allografts to fill the defect. We report our experience with the use of a titanium foam block specifically designed for fusion of failed ankle replacements. This particular method was chosen to avoid the technical difficulties and morbidities associated with the use of bulk autografts and allografts. We describe the surgical technique and early results in the first two cases performed in our unit. The satisfactory clinical and radiologic results in the two cases demonstrate the ability of the titanium foam block to simplify an otherwise complex procedure without compromising the outcome.

Functional copolymer/organo-MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA-alt -1-octadecene)-g -PLA layered silicate nanocomposites with nanoporous core-shell morphology

Novel bioengineering functional copolymer-g-biopolymer-based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L-lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1-octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo-MMT clay (reactive ODA-MMT and non-reactive DMDA-MMT) complexes as nanofillers and tin(oct)2 as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT-IR spectroscopy, X-ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA-DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro- and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H-bonding and self-organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride-containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer-g-biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.

Allografts in Foot and Ankle Surgery: A Critical Analysis Review.

Allografts are commonly used during reconstructive procedures around the foot and ankle1. Compared with autograft tissue, allografts offer the advantage of unlimited tissue sources, decreased operative time, and lack of potential donor-site morbidity1. Allografts can be classified into three broad categories: (1) osteochondral grafts, (2) osseous/structural grafts (which can be subclassified as either bulk grafts or cortical/cancellous chips), and (3) allograft tendons. The use of these grafts has increased dramatically in the past decade, but there is concern that enthusiasm surrounding their use has outpaced the published evidence supporting their efficacy and safety. This article will critically review the available evidence regarding outcomes related to the use of allografts in foot and ankle surgery. Symptomatic osteochondral defects at any anatomic site present a substantial treatment challenge. The goals of operative treatment include the resolution of pain and/or mechanical symptoms, the restoration of articular surface congruity, the prevention of articular surface collapse, and, ultimately, the prevention of degenerative arthritis of the apposing joint surfaces2. In foot and ankle surgery, osteochondral allografts are most commonly …

Total hip arthroplasty with bulk femoral head autograft for acetabular reconstruction in developmental dysplasia of the hip.

Developmental hip dysplasia (DDH) presents considerable technical challenges to the primary arthroplasty surgeon. Autogenous bulk grafting using the femoral head has been utilised to achieve anatomic cup placement and superolateral bone coverage in these patients, but reported outcomes on this technique have been mixed with the lack of graft integration and subsequent collapse, an early cause of failures. We describe a novel technique combining the use of bulk autograft with an iliac osteotomy, which provides primary stability and direct cancellous-cancellous bone contact, optimising the environment for early osseointegration. Twenty-one hips in 21 patients with DDH underwent this technique and were followed for a mean of 8.1 years. The preoperative radiographic classification was Crowe type I in 12 hips (57%), type II in 4 hips, and type III in 5 hips, and the mean Sharp angle was 49.6° (range 42°–60°). All grafts united by year. At time of followup, there was no radiographic evidence of graft collapse or loosening. There were no reoperations. Our study has shown that this technique variation combining an iliac osteotomy with bulk autograft in cases of developmental hip dysplasia provides early stability and reliable graft incorporation, together with satisfactory clinical and radiological outcomes in the medium term. Longer term study is necessary to confirm the clinical success of this procedure.

Bulk grafting of poly(styrene‐alt‐maleic anhydride) onto preirradiated polyolefin membranes in supercritical carbon dioxide

AbstractTo take advantage of the property of supercritical carbon dioxide as both a solvent and swelling agent, the bulk grafting of poly(styrene‐alt‐maleic anhydride) [P(MAH‐alt‐St)] onto preirradiated polyolefin membranes was performed by a combination of γ‐ray‐preirradiation‐induced graft copolymerization and supercritical fluid‐swollen polymerization. The trapped radicals on the polyolefin backbones were uniformly distributed by γ‐ray irradiation under a nitrogen atmosphere. Subsequently, these polymeric trapped radicals initiated the alternating copolymerization of styrene (St) and maleic anhydride (MAH) infused into the swollen polymer matrix with the aid of supercritical CO2. It was important that the graft copolymers were relatively pure without any contaminants, including homopolymers, monomers, and initiators. The experimental results show that the degree of grafting could be easily controlled. In addition, St/MAH could synergistically promote the bulk grafting process and strongly effect on the alternating trend; this was confirmed by element analysis and differential scanning calorimetry. Soxhlet extraction, X‐ray diffraction, and Fourier transform infrared spectroscopy indicated that the P(MAH‐alt‐St) was covalently bonded to the polymeric backbones. Scanning electron microscopy showed that the alternating graft chains were uniformly dispersed throughout the 5‐mm thickness of the polymer membranes on the nanometer scale. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Can Osteochondral Grafting Be Augmented With Microfracture in an Extended-Size Lesion of Articular Cartilage?

Background: Both microfracture and osteochondral autografting procedures have been useful in treating osteochondral lesions. Hypothesis: Combining microfracture and osteochondral autografting procedures can extend the size of lesions that can be treated with either technique. Study Design: Descriptive laboratory study. Methods: Eight adult goats underwent osteochondral autograft transfer of a 4.5-mm femoral trochlea plug into an 8-mm full-thickness chondral defect. Microfracture was performed in the gap region surrounding the autograft. The animals were allowed normal activity until the end of the experiment at 6 months. At harvest, the knees were assessed grossly, and then evaluation was performed by histology, histomorphometry, biochemistry, and biomechanics. Results: The osteochondral plugs healed well, with integration of the bone and preservation of the chondral cap. The chondral gap between the host site articular cartilage and the transferred plug had decreased from 3 mm at implant to less than 0.1 mm. Histologic analysis demonstrated regions of variable cartilage repair, with integration of the cartilage layer at some sites but incomplete healing at others. Histomorphometry demonstrated filling of the chondral gap to 75% to 85% of the normal volume. Biochemical analysis revealed greater than 90% type II collagen at most sites, with some areas containing 80% type II collagen. Biomechanical indentation testing indicated that the repaired area had variable thickness and stiffness, with a trend of increased stiffness in the bulk graft and decreased softness at the proximal microfracture interface site. Conclusion: The performance of a combined microfracture and osteochondral autograft transfer procedure to resurface a large chondral defect appears promising. Clinical Relevance: This combined technique shows promise for treatment of large chondral defects with a single operative procedure with autogenous tissue that is safe and potentially would have a shorter period of rehabilitation, similar to that of osteochondral transfers and microfracture, in a cost-effective setting.

La ricostruzione acetabolare con augment in tantalio nei gravi difetti ossei

Acetabular bone defects are a critical and frustrating issue; while it is possible to obtain a good reconstruction with conventional methods (i.e. bulk graft, cage and cement), such results are rarely observed in longer-term follow-up. The aim of this paper is to present a reconstructive method, based on tantalum properties, designed to perform the filling of defects as augmentation. We analyzed 26 cases of acetabular defects, scored 3A or more according to Paprosky. Preliminary data are encouraging: good clinical results and no failures at 2-year average follow-up, nor pending revisions.

“Grafting-from” polymerization for uniformly bulk modification of pre-existing polymer materials via a supercritical-fluid route

A novel approach to uniformly bulk graft modification of pre-existing polymer materials without ungrafted homopolymers was achieved at relatively low temperature by means of gamma (γ)-rays pre-irradiation-induced “grafting-from” polymerization with supercritical carbon dioxide (scCO2) both as solvent and as swelling agent. The polymer substrates were first irradiated with γ-rays originated from cobalt-60 resource under nitrogen atmosphere at ambient temperature, and thereby leading to uniform formation of trapped radicals on polymer backbone. Then, the produced polymer-trapped radicals were utilized to initiate graft polymerization of vinyl monomers dissolved in scCO2 within polymer substrates. A combination of transmission electron microscopy, scanning electron microscopy and elemental analysis shows that side graft chains covalently bonded to polymer substrate backbone in nanometer scale are uniformly dispersed within polymer membranes with a thickness of 5mm. Altering the experimental conditions can easily control the grafting yield with regard to side graft-chain length. This method can also be applied to various functional polymer chains covalently attached to different polymer substrates, even with high viscosity or limited solubility. The novel graft-polymer materials produced by this method are not formed in the absence of scCO2 and are impossible to prepare by conventional methodologies.

Bulk graft modification of polyolefin membranes by combining pre-irradiation-induced graft and supercritical CO 2-swelling polymerization

Uniform bulk graft modification of vinyl monomers to polypropylene or polyethylene membranes was achieved by combining gamma (γ)-ray pre-irradiation-induced graft copolymerization and supercritical carbon dioxide (scCO 2)-swelling polymerization techniques. In the first step, the polymer membranes were irradiated with γ-rays originated from cobalt-60 resource under oxygen or air atmosphere at ambient temperature, and thus potential active sites, hydroperoxides and diperoxides, were uniformly formed on the polymer backbone. Then, graft copolymerization of vinyl monomers such as styrene, N-vinylpyrrolidone ( N-VP), methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) impregnated into polymer substrates with the aid of scCO 2 was initiated thermally within the host polymer by the polymer radicals (PO ) resulting from the decomposition of peroxides uniformly distributed in the irradiated polymer samples. The process parameters were controlled by the properties of the fluid phase (CO 2/monomer mixture) and experimental conditions, such as monomer concentration, temperature and time. The bulk graft modification of polyolefin membranes was confirmed by element analysis, spectroscopy and microscopy.