Alessandro Addis

Surface‐modified zirconia implants: tissue response in rabbits

AIM To evaluate the bone tissue response to zirconia implants with three different surface modifications in comparison with the oxidized titanium surface with the goal to optimize osseointegration in terms of strength and speed. MATERIALS AND METHODS A total of 18 rabbits with 143 implants were used. One hundred and twenty-three were threaded zirconia ceramic implants with three different surface topographies and 20 modified titanium oxide implants were controls. Each rabbit received eight implants and sacrificed after 3 weeks. The removal torque test (RTQ) and histology were performed. RESULTS Sixteen out of 18 rabbits completed the study with a total of 110 implants. No statistical significance was observed between the chemical modification implants compared with the topographically modified zirconia implant in terms of interfacial shear strength proven by the RTQ applied. No statistical significance was also observed in the bone-to-implant contact between the zirconia implants and the control oxidized implants. CONCLUSIONS The findings suggest that additional specific chemical modifications of the topographically modified zirconia implants do not seem to enhance the bone-to-implant contact and appear not to increase the interfacial shear strength.

Effects of a calcium phosphate coating on the osseointegration of endosseous implants in a rabbit model

OBJECTIVES The aim of the present study was to evaluate a Ca-P coated implant surface in a rabbit model. The Ca-P surface (test) was compared to the titanium porous oxide surface (control) in terms of bone-to-implant contact (BIC) and removal torque value. MATERIALS AND METHODS Two hundred and sixteen dental implants were inserted in the tibia and in the femur of 36 rabbits. One hundred and eight were represented by Ca-P oxidized surface implant and other 108 were titanium porous oxide surface modified implants. Each rabbit received six implants. Animals were sacrificed after 2, 4 and 9 weeks of healing. Each group included 12 rabbits. The femoral implant and the proximal implant of the tibia of each animal were subjected to the histologic analysis and the distal implants of the tibia underwent removal torque test (RTQ). RESULTS Histological analysis in terms of BIC and RTQ did not revealed any significant difference between the Ca-P oxidized surface and the oxidized surface at 2 and 4 weeks. At 9 weeks, the oxidized surface demonstrated better results in terms of RTQ in the tibia. CONCLUSION In conclusion, findings from the present study suggested that the Ca-P coating had no beneficial effect in improving bonding strength at the bone-implant interface either at 2, 4 and 9 weeks.

Spine stability after implantation of an interspinous device: an in vitro and finite element biomechanical study

OBJECT Interspinous devices are widely used for the treatment of lumbar stenosis. The DIAM spinal stabilization system (Medtronic, Ltd.) is an interspinous implant made of silicone and secured in place with 2 laces. The device can be implanted via posterior access with the sacrifice of the supraspinous ligament (SSL) or via lateral access with preservation of the ligament. The aim of the present work was to evaluate the role of the laces, the SSL, and the device size and positioning to determine the devices ability in reducing segmental lordosis and in stabilizing motion. METHODS Biomechanical tests were performed in flexion and extension on 8 porcine spines implanted with the DIAM either with or without the laces and the SSL. A finite element model of the human L4-5 spine segments was also created and used to test 2 sizes of the device implanted in 2 different positions in the anteroposterior direction. RESULTS Implantation of the DIAM induced a shift toward kyphosis in the neutral position. Laces, the SSL, and device size and placement had a significant influence on the neutral position, the stiffness of the implanted spine, and the positions of the instantaneous centers of rotation. CONCLUSIONS The shift of the neutral position toward kyphosis may be beneficial in reducing symptoms of spinal stenosis such as radicular pain, sensation disturbance, and loss of strength in the legs. The authors recommend preservation of the SSL and the use of the fixation laces, given their relevant mechanical role. Choosing the proper device size and placement should be achieved by using a correct surgical technique.

Role of autologous rabbit adipose‐derived stem cells in the early phases of the repairing process of critical bone defects

Adipose‐derived stem cells (ASCs) may represent a novel and efficient tool to promote bone regeneration. In this study, rabbit ASCs were expanded in culture and used for the regeneration of full‐thickness bone defects in the proximal epiphysis of tibia of 12 New Zealand rabbits. Defects were implanted with graft material as follows: untreated (control), empty hydroxyapatite (HA) disk, ASCs alone, and HA disk seeded with ASCs. Each isolated ASCs population was tested in vitro: they all showed a high proliferation rate, a marked clonogenic ability, and osteogenic differentiation potential. Eight weeks after implantation, macroscopic analyses of all the samples showed satisfactory filling of the lesions without any significant differences in term of stiffness between groups treated with or without cells (p > 0.05). In both the scaffold‐treated groups, a good osteointegration was radiographically observed. Even if HA was not completely reabsorbed, ASCs‐loaded HA displayed a higher scaffold resorption than the unloaded ones. Histological analyses showed that the osteogenic abilities of the scaffold‐treated defects was greater than those of scaffold‐free samples, and in particular new formed bone was more mature and more similar to native bone in presence of ASCs. These results demonstrated that autologous ASCs–HA constructs is a potential treatment for the regeneration of bone defects.

Porcine adipose-derived stem cells from buccal fat pad and subcutaneous adipose tissue for future preclinical studies in oral surgery

IntroductionAdipose-derived stem cells (ASCs) are progenitor cells used in bone tissue engineering and regenerative medicine. Despite subcutaneous adipose tissue being more abundant, the buccal fat pad (BFP) is easily accessible for dentists and maxillofacial surgeons. For this reason, considering the need for preclinical study and the swine as an optimal animal model in tissue engineering applications, we compared the features of porcine ASCs (pASCs) from both tissue-harvesting sites.MethodsASCs were isolated from interscapular subcutaneous adipose tissue (ScI) and buccal fat pads of six swine. Cells were characterized for their stemness and multipotent features. Moreover, their osteogenic ability when cultured on titanium disks and silicon carbide-plasma-enhanced chemical vapor-deposition fragments, and their growth in the presence of autologous and heterologous serum were also assessed.ResultsIndependent of the harvesting site, no differences in proliferation, viability, and clonogenicity were observed among all the pASC populations. Furthermore, when induced toward osteogenic differentiation, both ScI- and BFP-pASCs showed an increase of collagen and calcified extracellular matrix (ECM) production, alkaline phosphatase activity, and osteonectin expression, indicating their ability to differentiate toward osteoblast-like cells. In addition, they differentiated toward adipocyte-like cells, and chondrogenic induced pASCs were able to increase glycosaminoglycans (GAGs) production over time. When cells were osteoinduced on synthetic biomaterials, they significantly increased the amount of calcified ECM compared with control cells; moreover, titanium showed the osteoinductive effect on pASCs, also without chemical stimuli. Finally, these cells grew nicely in 10% FBS, and no benefits were produced by substitution with swine serum.ConclusionsSwine buccal fat pad contains progenitor cells with mesenchymal features, and they also osteo-differentiate nicely in association with synthetic supports. We suggest that porcine BFP-ASCs may be applied in preclinical studies of periodontal and bone-defect regeneration.

Transapical endovascular implantation of neochordae using a suction and suture device

OBJECTIVE Neochordae implantation is a standard method for treatment of mitral valve prolapse. We describe a transcatheter technology enabling transapical endovascular chordal implantation. METHODS Six adult pigs were anesthetized. Two 10F sheaths were introduced in the femoral vessels for monitoring and intracardiac echo. After midline sternotomy, the pericardium was opened, the apex was punctured inside two 2-0 polypropylene purse strings. A 0.035 in J tipped guidewire was introduced in the left ventricle and an ultra stiff 14F sheath (guide catheter) inserted through the apex. A suction-and-suture device was introduced in the left ventricle. The mitral valve was crossed under echo guidance. Using suction, either the anterior (two cases) or posterior (four cases) leaflet was captured and a loop of 4-0 polypropylene was thrown at the edge of the leaflet. The loop, with a pledget, was exteriorized through the introducer. The introducer was removed and the purse-string tied. Under echo guidance, the neochordae suture was pulled and tied over a pledget to evoke leaflet tethering. The animals were sacrificed and gross anatomy reviewed. RESULTS Leaflet capture was feasible in the intended location in all cases. Following suture tethering, variable degrees of MR were obtained. At gross anatomy, the neochordae were positioned at 1-4mm from the leaflet free edge, and were firmly attached to the leaflets. CONCLUSIONS Transcatheter endovascular neochordae implantation is feasible. A prolapse model is needed to further demonstrate feasibility under pathologic conditions. The apical approach allows easy and direct route to transcatheter beating heart minimally invasive mitral repair.

Self-closing surgical clips for use in pericallosal artery–pericallosal artery side-to-side bypass: Case report

The authors demonstrate the feasibility of a new procedure to create intracranial interrupted microvascular anastomosis. Self-closing nitinol surgical clips were used for a pericallosal artery-pericallosal artery side-to-side bypass in a 52-year-old man harboring an unruptured large aneurysm located on the right A2 segment. The outflow artery was found to arise from the dome of the aneurysm, which was considered unsuitable for stand-alone clip ligation or coil occlusion. After bypass patency was intraoperatively confirmed using near-infrared indocyanine green videoangiography, the aneurysm and feeding artery were embolized with coils and safely occluded. Both postoperative courses were uneventful. The patient was discharged neurologically intact on the 5th postembolization day. Postprocedure angiography demonstrated no ipsilateral aneurysm filling and excellent bilateral distal outflow from the left anterior cerebral artery.

Self-closing U-clips for intracranial microanastomoses in high-flow arterial bypass: technical case report.

OBJECTIVE Self-closing nitinol U-clips (Medtronic, Inc., Minneapolis, MN) have been used to create vascular microanastomoses by vascular surgeons. This device eliminates the need for suture management and knot tying. Therefore, a high-quality interrupted microvascular anastomosis can be obtained in a shorter period of time. This is the first report of a U-clip intracranial arterial microanastomosis for a high-flow extracranial-intracranial bypass using a radial artery graft. CLINICAL PRESENTATION A 24-year-old woman with a history of chronic headache was admitted to the National Neurological Institute Carlo Besta after a brain computed tomographic scan revealed a giant serpentine aneurysm of her right middle cerebral artery. Magnetic resonance angiography and four-vessel angiography confirmed the diagnosis and ruled out other lesions. INTERVENTION A radial artery graft was used to create a high-flow bypass between the external carotid artery and the postaneurysmal M2 segment of the right middle cerebral artery. Nitinol self-closing U-clips were used for the interrupted intracranial microanastomosis. After intraoperative near-infrared indocyanine green video angiography confirmed the bypass patency, the aneurysm could be trapped. CONCLUSION The postoperative course was uneventful. The patient was discharged on the seventh postoperative day and was neurologically intact. Postoperative angiography documented the successful exclusion of the aneurysm and the presence of revascularization of the distal branches of the right middle cerebral artery through the bypass. This case demonstrates the efficacy of U-clips for intracranial microanastomoses.

Transcatheter direct mitral annuloplasty with Cardioband: feasibility and efficacy trial in an acute preclinical model.

AIMS The aim of the study was to report preclinical safety and feasibility of a new transcatheter direct mitral annuloplasty intervention in an acute animal model. METHODS AND RESULTS Twenty healthy pigs underwent Cardioband (Valtech Cardio, Or Yehuda, Israel) transcatheter implantation under intracardiac echocardiographic and fluoroscopic guidance. Through a neo inferior vena cava approach, transseptal access was arranged. The device was delivered into the left atrium using a multi-steerable catheter and fixed to the mitral annulus with multiple helix anchors. Following device cinching, reduction of annular size was evaluated. In all animals the device could be successfully implanted and displayed 100% function, with the average procedure duration and fluoroscopy times being 78±23 minutes and 27±9 minutes, respectively. In total, 246 anchors (average 12.3 per device) were delivered and optimal anchor placement was achieved in 95.1%, while inadequate anchor position (4%) and injury of the coronary sinus or atrium (0.8%) occurred in the rest. Following maximal cinching, diastolic transmitral flow velocity and coaptation lengths were markedly increased (p<0.001), whereas septolateral and intercommissural distances were significantly decreased (p<0.001), when compared to pre-contraction baseline, demonstrating efficient annular reduction by the device. CONCLUSIONS Transcatheter direct annuloplasty with a surgical-like adjustable device is feasible in the porcine animal model. The humanised porcine model has been instrumental in demonstrating feasibility and in establishing the procedural steps.

Meniscus maturation in the swine model: changes occurring along with anterior to posterior and medial to lateral aspect during growth

The meniscus plays important roles in knee function and mechanics and is characterized by a heterogeneous matrix composition. The changes in meniscus vascularization observed during growth suggest that the tissue‐specific composition may be the result of a maturation process. This study has the aim to characterize the structural and biochemical variations that occur in the swine meniscus with age. To this purpose, menisci were collected from young and adult pigs and divided into different zones. In study 1, both lateral and medial menisci were divided into the anterior horn, the body and the posterior horn for the evaluation of glycosaminoglycans (GAGs), collagen 1 and 2 content. In study 2, the menisci were sectioned into the inner, the intermediate and the outer zones to determine the variations in the cell phenotype along with the inner–outer direction, through gene expression analysis. According to the results, the swine meniscus is characterized by an increasing enrichment in the cartilaginous component with age, with an increasing deposition in the anterior horn (GAGs and collagen 2; P < 0.01 both); moreover, this cartilaginous matrix strongly increases in the inner avascular and intermediate zone, as a consequence of a specific differentiation of meniscal cells towards a cartilaginous phenotype (collagen 2, P < 0.01). The obtained data add new information on the changes that accompany meniscus maturation, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint.