Biomedical subjects

M Rocca

Publications and source records attributed to M Rocca.

At least 37 records · Page 2Linked to original sources

PubMed2000

In vitro pathological model of osteopenia to test orthopaedic biomaterials.

The association of in vitro tests and in vivo bone implants, has significantly improved the characterization of biomaterials for orthopaedic devices before their clinical use. However, neither cell cultures nor most animals models used for these tests entirely reflect the clinical conditions in which biomaterials are implanted. Pathological animal models are considered to substantially improve our knowledge of osteointegration of biomaterials; for this reason researchers increasingly use aged, osteopenic or arthritic animals in their experimental tests. The development of "pathological cell cultures" would also be of great importance for the study of biomaterials. It would allow a complete material evaluation, beginning with a biocompatibility test to a more finalized and specific preclinical evaluation. The present study, looks at the possibility of using cell culture methodology for the improvement of in vitro biomaterials characterization in the case of osteopenia. Cultures derived from normal (NB-OST) rats were compared to those of osteopenic (OB-OST) rats, by testing the osteoblasts against common parameters of characterization. Moreover, the reaction of these cultures to two biological glasses of known in vivo behavior (both in normal and osteopenic bone) by means of parameters on biocompatibility and bone formation index, was evaluated. Our results showed that there was no evidence of differences between the NB-OST and OB-OST cultures. After 6 days of culturing, the bioglass that did not osteointegrate in osteopenic animals, did not induce cytotoxicity in NB-OST, but a significative reduction of viability and Osteocalcin level in OB-OST was observed. We think that these data should stimulate researchers to develop further tests in order to improve preliminary in vitro comprehension on biomaterials.

Alkaline Phosphatase↗

PubMed2000

Assessment of low-power laser biostimulation on chondral lesions: an "in vivo" experimental study.

The purpose of this study was to evaluate whether intraoperative laser biostimulation can enhance healing of cartilaginous lesions of the knee. Surgery was performed on eighteen rabbits: a bilateral chondral lesion of 1.25 +/- 0.2 mm in length and 0.8 +/- 0.2 mm in width was created in the femoral medial condyle with a scalpel. The lesion in the left knee of each animal was treated intraoperatively using the diode Ga-Al-As 780nm. laser (300 Joules/cm2, 1 Watt, 300 Hertz, 10 minutes), while the right knee was left untreated, as control group. The animals were divided into three groups, A, B and C, according to the survival time after surgery, two, six and twelve weeks, respectively. The explants from the femoral condyles, both treated employing laser energy and left untreated, were examined histologically. Results showed a progressive filling with fibrous tissue of the cartilaginous lesion treated with laser irradiation, while no changes in the original lesion of the untreated group were observed at the end of the study. Maybe, in this experimental research, underexposure to laser irradiation was the cause for the absence of the necessary conditions for biostimulation.

Animals↗

PubMed2000

Osteochondral lesion repair of the knee in the rabbit after low-power diode Ga-Al-As laser biostimulation: an experimental study.

The purpose of this study was to evaluate whether low-power laser biostimulation of the osteo-chondral lesions of the knee could by itself reduce repair healing time. Surgery was performed on eighteen rabbits; a bilateral osteo-chondral lesion of 2.5mm in diameter and 2mm depth was created in the femoral medial condyle with a drill. The left knee of each animal was treated intraoperatively using the diode Ga-Al-As laser (780nm) with the following parameters: 300 Joules/cm2, 1 Watts, 300 Hertz, 10 minutes; the right knee was left untreated, as control group. The animals were divided into three groups, A, B and C, according to the survival time after surgery, two, six and twelve weeks, respectively. The explants from the femoral condyles, either treated employing laser energy or left untreated, were examined histomorphometrically. Results after laser treatment showed faster healing of the lesion at week 2 (p=0.043) and an overall improvement in cellular morphology (p=0.044), while a more regular aspect of the osteocartilaginous tissue was observed at week 12 (p=0.004). A relationship between laser biostimulation properties and healing of the osteo-chondral defect has been demonstrated.

Aluminum↗

PubMed2000

The ovariectomised sheep as a model for testing biomaterials and prosthetic devices in osteopenic bone: a preliminary study on iliac crest biopsies.

A histomorphometric and ultrastructural evaluation on sheep iliac bone was performed. Six sheep were ovariectomised (OVX Group) and 6 were left intact (Sham-aged, Control Group). An iliac crest biopsy was performed randomly in 6 animals at the beginning of the study, then, in all the animals, after 12 and 24 months. A significant decrease in trabecular bone volume, trabecular thickness (p<0.0005) and cell volume (p<0.005) was observed in OVX animals. A modest decrease in trabecular number and osteoid thickness together with an increase in trabecular separation were observed in OVX animals at 12 and 24 months. The osteoid volume showed a significant difference (p<0.05) between the groups. In OVX animals, at 12 months, Scanning Electron Microscopy revealed an enlargement of the trabecular space and a progressive replacement of bone matrix with adipose tissue. These signs were accentuated at 24 months. In conclusion, OVX sheep showed a loss of trabecular bone starting at 12 months after ovariectomy. The developed osteopenic state may be considered as a useful tool when doing research on biomaterial osteointegration.

Analysis of Variance↗

PubMed2000

A resorbable biomaterial shaped as a tubular chamber and containing stem cells: a pilot study on artificial bone regeneration.

In a previous study, we showed how healing of non-union defects in rabbit radii can be achieved by means of a tubular resorbable chamber, in comparison with untreated defects. In the present study, we placed bone marrow stem cells inside the chamber. Bone marrow was obtained by percutaneous aspiration from the iliac crest in 9 adult New Zealand rabbits. Stem cells were separated by the centrifugation technique. In the same animals, a defect of 10 mm was created in both radii. On the left side, the defect was treated with the poly-DL-Lactide chamber, in which a suspension of autologous cells was injected; on the right side, only autologous cells were used. Radiological and histomorphometric data were compared within this study as well as with the results of our previous study. At 3, 6 and 9 months, there was no healing on the right side..On the left side, progressive bone formation with reunion of the stumps was observed in the chamber. We conclude that stem cells can accelerate bone healing when contained in the tubular chamber.

Animals↗

PubMed2000

Biomaterials in spinal fixation. An experimental animal study to improve the performance.

Different pedicle screws were biomechanically and morphologically studied and compared through the use of an animal model to determine their efficacy and resistance in spinal fixation. The principal objective was to compare biomechanical and histomorphological aspects of HA-coated screws to uncoated ones. Fourty-eight cylindrical transpedicular self-tapping screws divided into three groups of sixteen each were employed; Group A: stainless steel screws; Group B: titanium screws; Group C: HA-coated titanium screws. The screws were implanted bilaterally and randomly into the L3, L4, and L5 pedicles of eight adult mongrel sheep. The final insertion torque was measured in all the implants. After one and four months, upon euthanization, four samples per group were extracted from the surrounding bone and the screw extraction torque was measured. The remaining samples were examined and processed for histological and histomorphological evaluations. No differences were observed at one month among the extraction torque of the three groups. After four months the only significance between insertion and extraction values was for the HA group, i.e. p=0.001. Comparing the extraction torque values of the three groups after four months of healing, the HA-coated group showed a greater than twofold increase (p<0.0005). No differences were observed at one month among the percentages of bone-implant contact in the three groups. After four months the percentage was significant only for the C group (p<0.0005). At four months a correlation was found between the morphological and the biomechanical data of group C (p<0.0005). The use of hydroxyapatite-coated screws could act as an effective method to improve the bone-implant interface, thus obtaining a strong fixation of the implant independently of the arthrodesis achieved with bone graft.

Analysis of Variance↗

PubMed1999

Measurement of insertion torque of tapered external fixation pins: A comparison between two experimental models.

The aim of this study was to compare an in vitro versus an ex vivo experimental model to test the insertion torque of two different types of external fixation pins. A torque measuring machine was developed in order to perform accurate measurements. Forty tapered pins made of stainless steel were utilized. Half of the pins were plasma-spray coated with hydroxyapatite (HA) and the other half remained uncoated. For the in vitro model 20 cylinders were used that were made of synthetic polymer according to ASTM standards. For the ex vivo model 10 fresh femora harvested from adult sheep were used. All the pins were implanted after predrilling, and insertion torque was measured. Statistical analysis of the in vitro versus the ex vivo model showed significant differences in both coated (p < 0. 0005) and uncoated (p = 0.002) external fixation pins. These results may be due to the surface roughness that caused significant friction between the HA coating and the polyvinylchloride in the in vitro model. The significant difference between the in vitro and ex vivo results lead us to state that the in vitro model does not realistically simulate the behavior of external fixation pins implanted in bone.

Animals↗

PubMed1999

Reconstruction of extensive long-bone defects in sheep using porous hydroxyapatite sponges.

The capacity of hydroxyapatite (HA) implants to support large defect repair in weight-bearing long bones of large size animals was investigated. Diaphyseal resections 3.5 cm of the tibia were performed in five adult sheep. They were substituted with HA macroporous ceramic cylinders anatomically shaped, and an external fixator was assembled. The sheep were sacrificed at 20, 40, 60, 120, and 270 days after surgery, respectively. Histology and micro X-ray study of resected implants and adjacent tissues showed proper integration of ceramic with newly formed periosteal bone as early as 20 days after surgery. In one sheep, the external fixator was removed 5 months after surgery. The animal gained the ability to walk with no functional impairment until it was sacrificed 4 months later. At this time, extensive integration of ceramic with bone was detected radiographically and confirmed by a morphological study of the resected sample. Our data indicate that large defects in a weight-bearing long bone can be repaired to the extent necessary for full functional recovery in large animals. These data set the stage for further intervention on material properties as well as for preliminary attempts to use ceramic prostheses for reconstruction of large bone defects in humans.

Animals↗

PubMed1999

Xenogenic demineralized bone matrix: osteoinduction and influence of associated skeletal defects in heterotopic bone formation in rats.

Demineralized bone matrix (DBM) was ectopically implanted in 36 male Wistar rats. In 18 of the animals a bone defect in the femoral condyles was also created: the left was filled with DBM and the right was left empty as a control. The animals were killed after 2, 4 and 6 weeks and new bone was histologically evaluated, comparing ectopic bone formation with or without distant bone injury. Results showed: (1) osteoinductivity of xenogenic DBM, and (2) earlier mineralization of ectopically implanted DBM in the group with associated skeletal injury. Our results show that xenogenic bone matrix acts as an osteoinductive material and that skeletal injury improves osteogenesis at distant sites.

Animals↗

PubMed1999

Effects of essential amino acids and lactose on bony fractures and defects in rabbits: a preliminary histomorphometric study.

An experimental study was performed in order to test the possibility of improving bone repair with the administration of a drug (Calciofix, Farmaceutici Damor SpA, Naples, Italy) containing essential amino acids and lactose. Fifty rabbits were submitted to an open transversal fracture of the left fibula and to a right femoral condyle defect. They were left untreated or treated daily with the drug orally and were divided into subgroups depending on the experimental time: 15, 30, 40, 50, 60 days. Histomorphometric data showed a significantly faster healing rate in treated animals compared with untreated ones. Firstly, on day 30 there was a significantly larger amount of cartilage in the control bone callus (P < 0.01). On day 50 a significant difference existed between trabecular and lacunar percentages in the two subgroups (P < 0.0005). At 60 days no significant differences were observed, but bony trabeculae had become more oriented parallel to the long axis of the bone in treated animals. Secondly, after 15 days the defect area was significantly smaller in treated animals than in the untreated ones (P < 0.01). At 30 and 40 days, respectively, significant differences existed between the two subgroups in connective tissue and mature bone percentages (P < 0.01 and P < 0.001). Our results seem to demonstrate that the drug significantly accelerates the rate of bone formation in fractures and bone defects in rabbits.

Amino Acids↗

PubMed1999

Polylactide bioabsorbable polymers for guided tissue regeneration.

OBJECTIVE: Guided tissue regeneration is a procedure to improve tissue repair, which creates an optimal environment for the intrinsic growth ability of tissues. METHODS: A prerequisite for guided tissue regeneration is the availability of materials with suitable physicochemical and biocompatibility properties for the preparation of the devices. We investigated bone and peripheral nerve guided tissue regeneration, making two conduits from poly[L-lactide-co-6-caprolactone] (PLLC--peripheral nerve) and with poly [DL-lactide] (PDLLA--bone) with different features. After the polymer synthesis and chemical characterization, the conduits were evaluated in vivo in rat sciatic nerve gaps and in rabbit radius defects. RESULTS: The results demonstrated good biocompatibility of both polymeric conduits. A good axonal regeneration and the restoration of the nerve trunk continuity, similar to that observed with autologous grafts has been obtained with PLLC conduits, that slowly degrade in about 6 months. PDLLA conduits protected the bone defect against the invasion of surrounding soft tissues; an effective bone growth bridging the defect was observed in their lumen. CONCLUSION: These results confirm the versatility of polylactides as biomaterials and will encourage further investigations on hard and soft tissues.

Absorption↗

PubMed1999

Atomic absorption spectrophotometry (AAS) for the evaluation of metallosis in prostheses and artificial organs: a new approach.

To study the presence of metals in body fluids and tissues after implantation of metallic biomaterials and possible related diseases, a new approach in Atomic Absorption Spectrophotometry (AAS) was developed. This technique was compared to three traditional methods: mineralisation with acid digestion (method A) also known as "wet method", dry ashing (with or without oxygen) (method B); classic Kjeldaal (method C). The new approach (method D) modifies the mineralisation phase and the instrument operating instructions. Al, Na, Cr, K, Ni, Co, Ti, Fe, Hg, Pb, V, Sb and Cu levels were tested with the four methods on bone, muscle, cartilage, skin, brain, lymph nodes, blood, urine, and hair. Test results were checked by the addition method. Results demonstrated a significantly higher percentage of Al, Cr, Ni, Ti and Hg recovery with the new approach. The advantages of method D are no residue, no redox reaction, insignificant loss of analytes and enhanced sensitivity (at ppb level vs ppm of the other methods). This approach should be considered especially when testing heavy metals and complex matrices. Its disadvantages are that it is more time consuming and requires the presence of an operator.

Humans↗

PubMed1999

Hydroxyapatite fully coated conic hip prosthetic stem: a long term animal study.

The purpose of this paper is to evaluate in an animal model the long term results obtained with a prosthetic stem fully coated with hydroxyapatite. The cup was manufactured in polyethylene and was cemented. Six arthroplasties were performed in six sheep. After twelve months, the animals were euthanized and the femurs were harvested and processed for undecalcified sectioning. Twelve cross sections were cut perpendicularly to the longitudinal stem axis. Sections one to five corresponded to the area of the stem which, at the time of surgery, had a full initial contact between the bone and the prosthesis; sections six to ten corresponded to the area of the stem which, at the time of surgery, had a gap from 0 to 2 mm between the bone and the prosthesis; sections eleven and twelve had an initial gap larger than 2 mm. At one year after implantation, in the sections one to five, morphological analyses showed extensive direct contact between the bone and the hydroxyapatite coating. Bone prosthesis contact was lower in the sections six to ten. No contact was seen in sections eleven and twelve. Comparing bone to prosthesis contact of each subsequent section, from proximal to distal, the difference becomes significant with section five compared to section six (p < 0.00005). No detachment of the hydroxyapatite coating from the metallic substrate was observed in any section. In conclusion, this study shows that a conic shaped femoral stem, fully coated with hydroxyapatite gives very good histological and histomorphometric results at one year. Prosthesis osteointegration showed to be influenced by the initial bone to prosthesis contact. No direct bone to prosthesis contact was achieved if the initial bone to prosthesis gap was larger than 2 mm.

Animals↗

PubMed1999

[Trauma of the peripheral nervous system: experimental assessments with guided tissue regeneration].

Guided tissue regeneration open interesting perspectives in reconstructive surgery of peripheral nerves. Artificial conduits for nerve repair can be obtained with biodegradable polymers. Lactic and caproic acid copolimers and poliphosphazenes are biocompatible materials and have a slow reabsorption rate. Two types of conduits obtained with Poli[L-lactide-co-6-caprolactone] and poli [bis (etilalanate) phosphazene] were evaluAted as guides for nerve regeneration in an experimental model on two groups of six Wistar rats. Under general anesthesia and with microsurgical technique, the ischiatic nerve was bilaterally isolated. On the right side a segment of the nerve was removed to create a 10 mm gap. The defect was then repaired using the conduit. On the controlateral limb after the creation of the same defect, the nerve continuity was restored using as an autograft the segment removed from the right side. Control were performed at 30, 90, 180 days and consisted in histological and electron microscopy investigations. They showed the gradual degradation of both the conduits without signs of local toxicity. The regeneration of the nerve fibers in the lumen was not significantly different from that observed in the autologous grafts. Both the conduits may be considered effective for guided nerve regeneration, but polyphosphazenes allow the possibility of use the polymer as a carrier for neurite-promoting factors.

Animals↗

PubMed1998

Laser Doppler evaluation of microcirculation behaviour during an ischaemia-reperfusion injury.

Laser Doppler flowmetry (LDF) was tested in an experimental ischaemic model on rat limbs to evaluate the degree of ischaemia and to find a possible correlation with values obtained with this device and prognosis. Under general anaesthesia, 40 Wistar rats were submitted to 4 h and 30 min of ischaemia of the left hind limb. Ten rats formed the control group (group 1). Two enzymes, native superoxide dismutase (SOD) and SOD modified with polyethylene glycol, were employed in 15 rats each (groups 2 and 3). Data were collected by means of LDF both in the sole and muscles before ischaemia (steady state), during ischaemia and at the beginning of reperfusion, and only in the sole after 1 h of reperfusion. A range of predictive (95%) perfusion values (PU) for limb healing or necrosis was identified at the beginning of reperfusion. During ischaemia, PU changed from 0 to 10, both in the sole and in the muscle. A three-factor ANOVA (site, group, time) did not show interaction of these factors with PU (F = 1.655; p = 0.195), even if every single effect was significant (p < 0.0005). A two-factor ANOVA (group, time) showed a significant interaction of these factors with PU (F = 4.079; p = 0.019). The logistic regression between the reperfusion PU of each site and the survival of the limb was observed at the beginning and after 1 h of reperfusion in the sole only. Furthermore, a correlation between sole and muscle PU at the steady state and at the beginning of the reperfusion period was observed. The results showed the effectiveness of LDF, which can be considered a quite reliable tool to evaluate the degree of ischaemia and to have a good correlation with prognosis in this kind of experiments.

Animals↗

PubMed1998

pO2 measurement in an experimental model of patellar tendon autograft pro-anterior cruciate ligament.

Thirty-four sheep were submitted to surgery substituting the native ACL with the central third of the patellar tendon, ten enter this study. The purpose was to find a possible relationship between tissue pO2 and healing processes considering also the biomechanical and histomorphological aspects of the grafts. Four of them were sacrificed under general anaesthesia after 6 months, and six after 1 year in order to perform tissue pO2 measurement and an analysis of microvessel density on specimens of the normal ACL and the graft. Our data showed higher pO2 values of the autografts after 6 months. After 1 year the data was comparable to those of native ACL. This was confirmed by a microvessel count of the histological specimens and the data was in relationship to biomechanical and histomorphological analysis. Tissue pO2 can be observed and recorded in "in vivo" ACL, and patellar tendon used as graft, with no injury to their integrity. The monitoring system might be considered as an experimental tool for indirect controls of the anterior cruciate substitutes.

Animals↗

PubMed1998

A reabsorbable tubular chamber for the treatment of large diaphyseal bone defects. Experimental study in rabbits.

Twenty-five rabbits were used to test the healing of diaphyseal defects by means of a reabsorbable tubular chamber. In 20 animals a 10 mm gap was created in the left radius and bridged with a poly-L-lactide chamber (experimental side). The same defect was created on the right radius, remaining untreated (control side). In the remaining 5 animals, the right radius was left intact and they were used only for biomechanical tests at 12 months. X-rays and histomorphometry showed no bone repair at the control side while the inner surface of the chamber was progressively lined by neoformed bone (75% of the normal cortical thickness). Biomechanical data demonstrated that elastic modulus and ultimate stress were not significantly different in both experimental and intact radii. The chamber, by preventing the passage of soft tissues and creating a close space for intrinsic repair factors, seems to be a suitable device for the repair of long bone defects.

Analysis of Variance↗

PubMed1998

Comparison among three different biocoatings for orthopaedic prostheses. An experimental animal study.

One-hundred-eighty cylindrical monocortical titanium implants, 4mm diameter and 12mm long, with three different coatings: fluorohydroxyapatite (group A), hydroxyapatite (group B), and titanium oxide (group C), all applied by vacuum plasma spray were bilaterally, randomly implanted into the femurs and tibiae of twelve adult mongrel sheep. The sheep were divided into four groups (1, 2, 3 and 4) numbering three sheep each. Sheep of groups 1, 2, 3 and 4 were euthanized at two weeks, one month, three and nine months after implantation, respectively Biomechanical and histomorphological analysis were performed. Extraction torque increased over time in all groups until the nine months period. At all the studied periods, the bone-implant contact was higher in Groups A and B compared to Group C. However, only at nine months did this difference reach statistical significance (p<0.005 comparing Groups A and B to C). The results of this study show that all the three coatings could be recommended for clinical applications.

Animals↗