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Biomedical subjects

A Merolli

Publications and source records attributed to A Merolli.

12 recordsLinked to original sources
PubMed2006

In vivo assessment of the osteointegrative potential of phosphatidylserine-based coatings.

The successful implantation of titanium-based implants for orthopaedic and dental applications is often hindered because of their mobility, which arises because of a lack of direct binding of the metal surface to the mineral phase of the surrounding bone. Ceramic coatings, although ensuring the integration of the implant within the tissue, are unstable and carry risks of delamination and of failure. Recently, a novel biomimetic approach has been developed where porous titanium implants are coated with calcium-binding phospholipids able to catalyse the nucleation of discrete apatite crystals after only 30 min incubation in simulated body fluids. The present work assesses the osteointegrative potential of this new class of coatings in an in vivo rabbit model and compares its performance with those of bare porous titanium and hydroxyapatite-coated titanium. The data obtained show that phosphatidylserine-based coatings, whilst resorbing, drive the growing bone into apposition with the metal surface. This is in contrast to the case of bare titanium.

Animals↗
PubMed2003

Histomorphological study of bone response to hydroxyapatite coating on stainless steel.

Bone response to hydroxyapatite coating on stainless steel has not been so extensively tested in animals as it happened for other metallic substrate, like Ti6Al4V. For this reason, authors performed an in vivo histomorphological electron microscopic study of hydroxyapatite coating on duplex stainless steel cylinders, to gather further evidences on the characters of bone apposition at the interface. Sixteen HA-coated cylinders were implanted in the distal femur of New Zealand White rabbits. Comparison with uncoated controls was made. Retrieval steps were at: 4, 8, 26 and 34 weeks. Specimens were analyzed in a Jeol JSM 6301F scanning electron microscope. The response to HA-coated samples has a morphological character of tight apposition between bone and coating. Osteocytic lacunae may be found few microns close to the coating and newly formed bone is extremely interlocked with it so that even an higher magnification electron-microscopy cannot resolve any discontinuity in between. Pictures of physiological bone-turnover are distinguishable at the bone-coating interface; areas of well preserved coating may be present together with areas where local exfoliation or fragmentation has already completely exposed the metallic substrate. On the opposite in uncoated samples, despite a morphological picture of properly formed bone, the largest area of the metal has no direct apposition with it.

Journal Article↗
PubMed2001

Energy dispersive analysis (EDX) of a degradable bioactive-glass coating on Ti6Al4V in-vivo.

The bioactive-glass coating of metallic substrates provides a gradually degrading interface which can be used to favor the bony integration of the implant by the physiologic processes of bone turn-over and remodeling. Twelve New Zealand White rabbits, about 2700 g of weight, were operated by the sagittal insertion of a bioactive-glass coated plate of Ti6Al4V. Retrievals were performed at 4, 8 and 12 weeks. Undecalcified specimens were embedded in methyl-metacrylate and sectioned at 100 microns of thickness. Blocks were grinded and had an electroconductive coating to be examined by scanning electron microscopy (SEM), back scattering electron microscopy (BSEM) and X-ray energy dispersive spectroscopy microanalysis (EDX). EDX allows to evaluate quantitatively the gradual process of coating degradation. Areas of 200 microns in square were analyzed at the interface between bone and coating to determine their elemental composition. Silicon was the key marker for the presence of the glass. Morphological analysis confirms that a tight apposition with bone can be obtained by utilizing the bioactive glass coating of metal. Results of energy dispersive analysis support the mechanism of a gradual degradation of the bioactive glass coating and its integration with bone, since the presence of silicon can be documented within the newly formed bone after the coating has disappeared.

Journal Article↗
PubMed2001

Bone response to polymers based on poly-lactic acid and having different degradation times.

Authors studied two degradable and resorbable polymers derived from lactic acid: poly-L-Lactic acid (PLLA), with a relatively long time of degradation (longer than 6 months, PL10 Purac NL); poly-DL-Lactic acid (PDLLA), with a relatively short time of degradation (shorter than 6 months, PDL Purac NL). The animal species was the young adult New Zealand White rabbit. The in-vivo study was performed by implantation of small cylinders of 10 x 3 mm in size (length x diameter) in the distal metaepiphysis of the femur; 34 cylinders have been implanted. Retrievals of PLLA specimens took place at 3, 6, 9, 12 and 24 months; for PDLLA specimens at 1, 2, 4 months. Polarized light microscopy of undecalcified tissue sections was performed. The analysis for PLLA and PDLLA has shown a favorable response of bone tissue: alterations in the bone repair, growth and remodeling have not been observed. PLLA is persistent at the times studied; there is never a tight apposition between bone and PLLA implant and an intervening fibrous layer has often been observed. PDLLA is not persistent at the times studied and it degrades quite fast; bone repair of the empty implantation's hole occurs by bony growth from the endosteal trabeculae. The newly formed bone covers the hole's walls with an elongation parallel to them. For both polymers, whether the degradation is fast or slow, the material's substitution by newly formed bone never starts from the walls of the implantation hole. Only after the complete disappearance of the polymeric material newly formed bone begins to fill the hole.

Journal Article↗
PubMed2000

Comparison in in-vivo response between a bioactive glass and a non-bioactive glass.

The authors report on the in-vivo comparison, in the rabbit, between the response to a bioactive glass and the response to a non-bioactive glass. Implants have been performed in muscle and bone. Two different glasses were investigated, namely B01 and I02. B01 is a glass designed to be degradable and resorbable and has a percentual molar composition of: SiO2 49.6%; P2O5 2.7%; CaO + MgO + Na2O + K2O + Al2O3 47.7% with a 1 : 1 CaO/Na2O ratio. I02 is a sodium-calcium-silicate non-resorbable glass lacking P2O5 and has a percentual molar composition of: SiO2 70.7%; CaO + MgO + Na2O + K2O + Al2O3 29.3%. In-vivo tests were planned as: (a) intramuscular implants of glass cylinders in the rectus femoris and retrievals took place at 2, 16 and 43 weeks; (b) intraosseus implants of glass cylinders in the distal femural canal and retrievals took place at 8 and 43 weeks. Histology and light microscopy analysis followed. Bioactive degradable glass elicits a favorable response both in muscle and bone; a gradual degradation process leads to disruption and partial resorption of the material and a tight apposition is promoted with the newly formed bone. The non-bioactive sodium-calcium-silicate glass (named I02) may elicit, like the bioactive degradable B01, a favorable response which is characterized by the absence of inflammatory or other adverse reactions; anyway it does not change its structure at an optical microscopic level and it does not promote any tight apposition with bone.

Journal Article↗
PubMed1999

Response to polyetherimide based composite materials implanted in muscle and in bone.

The in-vivo response to a composite material obtained with polyetherimide (PEI) reinforced with carbon/glass fibers was investigated by histological methods by implanting cylinders in muscle and in bone of the New Zealand White rabbit. A common metallic alloy, widely used in orthopaedic surgery, was used as control (Stellite). The aim of the study was to analyze the biological response towards the surface of the material. Composite implants and metallic implants did not induce adverse or inflammatory reactions. The morphological picture produced was similar, in muscle and in bone, for both materials. In muscle, cylinders were confined by an extremely thin fibrous layer and the overall appearance of the muscular tissue was normal. In bone, cylinders were confined by a nearly annular rim of newly formed bone. From these data it is possible to derive that the response to PEI-based composite material is comparable with the response to metallic substrate and, then, the material can be suitable for clinical application.

Journal Article↗
PubMedDate not supplied

Autosomal dominant transmission of bilateral "opposable" triphalangeal thumb.

Triphalangeal thumb occurs in two functional types: opposable and non-opposable. The opposable type presents a rudimentary middle phalanx and the thumb is frequently angulated. The non-opposable type presents a finger-like thumb (five-fingered hand). Triphalangeal thumb often occurs in syndromes where other anomalies are present, so its pattern of inheritance has often been described jointly with the syndrome itself, then conflicting patterns of inheritance have been reported in literature. The present study reports upon the character of "bilateral opposable triphalangeal thumb" occurring isolated, without association of other anomalies. Authors studied the phenotype distribution in a family over five generations. They found that this character is transmitted with an autosomal dominant pattern of inheritance, and affected individuals are heterozygotes.

Adult↗
PubMedDate not supplied

Treatment of the sequelae of primary pathology of the hip by correction osteotomy and femoral lengthening using a combined external fixator.

It is not an exceptional event to observe the sequelae of primary pathology of the hip in young patients that, as such, are not of the ideal age for replacement surgery. Moreover, one must not overlook the difficulties involved in replacement surgery for the treatment of inveterate modifications in the normal hip anatomy. Often, among the sequelae of primary pathology of the hip, deformities of the lower limb must also be included, associated or consequent, which also need treatment. For these reasons, the authors, in three selected cases, used a combined external fixator (circular and lateral) by means of which they were at the same time able to correct the axial deformity (with a support osteotomy), and the residual hypometria (with femoral lengthening). Osteotomy plus lengthening, using an external fixator, avoid hypometria of the limb and deformity in valgus of the knee, and allow for results which would otherwise not be obtained with replacement surgery alone.

Adult↗
PubMedDate not supplied

The effectiveness of the circular external fixator in the treatment of post-traumatic of the tibia nonunion.

Authors report the results they obtained when the Ilizarov circular external fixator was used for the treatment of post-traumatic nonunion of the tibia. A total of 20 patients were treated. Of these 12 had been submitted to treatment elsewhere and using other methods; 9 presented with septic nonunion; 10 revealed radiographic findings of atrophic nonunion, and 10 were hypertrophic. There was axial deviation in 18 patients. The results of treatment were always: healing of the nonunion; functional recovery of the limb; correction of leg length discrepancy; recovery of the mechanical axis. The mean stabilization time (days between the application and the removal of the fixator) was 138 days. The Ilizarov method thus proved that it was effective in the treatment of post-traumatic nonunion of the tibia where other types of treatment had failed.

Adolescent↗