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Biomedical subjects

N Passuti

Publications and source records attributed to N Passuti.

At least 55 records · Page 3Linked to original sources
PubMed1996

Macroporous biphasic calcium phosphate ceramics: influence of five synthesis parameters on compressive strength.

Compressive strength measurements were conducted on 32 macroporous biphasic calcium phosphate (MBCP) samples to evaluate the influences and interactions of five synthesis factors: chemical composition, percentage of macropores, mean size of macropores, isostatic compaction pressure, and sintering temperature. These parameters were varied simultaneously between two limit levels. Experiments used a factorial design method (FDM) allowing optimization of the number of samples as well as statistical analysis of results. FDM showed that compressive strength, in a defined experimental area, can be described by a first-order polynomial equation in which the percentage of macroporosity and sintering temperature are the major influences. This study leads up to an isoresponse line diagram that will allow the manufacture of some classes of MBCP with fitted compressive strength.

Bone Substitutes↗
PubMed1996

[An experimental short-term study of intramuscular integration of macroporous biphasic calcium phosphate ceramics. Application to the achievement of biocomposite flaps].

The aim of this research is to prefabricate a bicomposite flap, which can be defined as a composite structure of foreign material and living tissue. An animal model was developed by vascularizing spherical implants of macroporous biphasic calcium phosphate by a latissimus dorsi muscle flap in rabbits. The experiment was divided into three stages to compare the role of blood flow in the flap and autologous marrow bone cells. Biological apatite precipitation inside the macropores requires both factors and allows further clinical applications.

Animals↗
PubMed1996

Histological features of large bone allografts.

We performed biopsies during reoperation for minor complications in two active young patients 9 and 19 months after massive bone allograft implantation for bone tumour. The grafts were dead and resorption-apposition activity, when present, was predominantly in subperiosteal areas. Inflammatory infiltration was very seldom found. Features considered as 'microfractures' or 'microcracks' were noted in the cortical ring together with the formation of woven bone, in areas with remodelling. Such cracks are likely to be of mechanical origin and do not inevitably lead to complications.

Adult↗
PubMed1995

Utilization of activated U937 monocytic cells as a model to evaluate biocompatibility and biodegradation of synthetic calcium phosphate.

The use of calcium phosphate biomaterials as a bone substitute necessitates the use of normative biocompatibility and biodegradation techniques which must be fast, simple and reproducible. In the present study, we have developed an in vitro model to study and to compare different calcium phosphate ceramics. After activation with 1,25-dihydroxy-vitamin D3 and phorbol 12,13-dibutyrate, the monoblastic U937 cells became multinucleated, expressed tartrate-resistant acid phosphatase and several markers of monocyte/macrophage differentiation. Activated U937 cells did not express the vitronectin receptor (VNR) (as revealed using monoclonal antibodies 23C6 or 13C2) but around 25% of the cells were strongly reactive with 211D, a novel monoclonal antibody that recognizes an osteoclast-specific membrane antigenic determinant. These cells remain active/viable with hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP) ceramics. In conclusion, activated U937 cells are good candidates to use in a normative in vitro method to evaluate new biomaterials.

Acid Phosphatase↗
PubMed1995

[Filling of bone defects using biphasic macroporous calcium phosphate ceramic. Apropos of 23 cases].

PURPOSE OF THE STUDY: The authors report their experience with the use of a biphasic macroporous calcium phosphate bone substitute. MATERIALS AND METHODS: In 23 cases (22 patients) a biphasic macroporous calcium phosphate ceramic was used to fill a pathological bone defect. The ceramic used in this study was a macroporous (400 to 600 mu) component consisting of 60 per cent hydroxyapatite and 40 per cent beta-tricalcium phosphate. It was in the form of granules (2 to 3 mm), sticks (20 x 5 x 5 or 10 x 5 x 5 mm) or custom made blocks. In 6 cases, the ceramic was used alone; in 12 cases with autologous bone marrow and in 5 cases with autologous cancellous bone grafts. In 14 cases, the bone defect was due to conservative treatment of a benign tumor, in 3 cases due to aseptic post-traumatic non union, in 3 cases due to wide resection for malignant tumors of the pelvis and in 3 cases following osteotomy. Post operative assessment was made from clinical, radiographic and histological findings. RESULTS: 2 patients died 6 and 8 months post operatively and 2 were lost to follow up at 2 and 5 months with both having good clinical and radiographic results when last seen. For the remaining 19 cases, the average follow-up was 20 months (from 6 to 62 months). No local, regional or general deleterious effects were noted. Radiologically the bone ceramic junction healed in all cases except 2 within 3 months. In these last two cases, healing required 6 and 7 months. No radiolucent line appeared around the ceramic. No stress fractures occurred in the substitute. Histologically, 3 biopsies showed new bone formation throughout the ceramic with apposition of a well differentiated lamellar bone directly apposed to the ceramic. DISCUSSION: Animal experimentations have proven the interest of similar ceramics: macroporosity enhances bone rehabilitation and the biphasic characteristics associate the advantages of slow resorption of hydroxyapatite and more easily resorbed beta-calcium phosphate. No deleterious clinical, radiographical or histological effects were observed, confirming the biocompatibility of this substitute. Despite the poor mechanical properties of this macroporous ceramic before implantation, good clinical and radiographic results suggest improvement of these properties in the composite new formed bone-ceramic after implantation. CONCLUSION: We believe that macroporous biphasic ceramic is a good substitute for use in bone defects when good primary mechanical stability and contact with the host bone are present. Further clinical and experimental studies are necessary to determine the limits of such a substitute in terms of volume and to control its mechanical properties following implantation.

Adolescent↗
PubMed1995

[Dual-energy X-ray absorptiometry: value in orthopedics].

We emphasize the opportunity of an in vivo bone mass measurement with an easy and accurate technique for orthopedic practice. At the present time, Dual Energy X Ray Absorptiometry (DEXA) is the most used technique, and is a safe and short examination. It can assess the quantity of mineral of any region of the body with a remarkable reproducibility (1 to 3 per cent). New machines are improved, and they permit many practical applications beyond the osteoporosis field. Thus, in orthopedics, we can distinguish several interesting topics. Peripheral risk of fracture can be evaluated because of good correlation between bone mineral content and biomechanical properties of bone. Even if a peripheral fracture occurs after a fall, low bone mineral density plays an important role, as in the case of femoral neck fractures in elderly patients. In traumatological practice, a DEXA with a specialized advice has to be requested if the traumatism cannot fully explain the occurrence of the peripheral fracture. Low bone mineral density defines an osteoporotic state, with the possibility of selecting adequate therapy. The good reproducibility of the measurement allows early estimation of bone loss following a period of immobilization. Varying models of osteosynthesis can be compared in vivo, to evaluate a decrease of "stress shielding" bone resorption. The role of stiffness of an implant on regional bone mineral content can be assessed. Likewise, periprosthetic bone mineral content can be measured in various regions, and followed over time. Specific software allows the exclusion of the region where the metallic prosthesis is projected. The reproducibility of this peripheral bone mineral content is 2 to 3 per cent, which individually allows an estimation of variations of more than 5 per cent. It will be possible to evaluate in vivo the influence of various parameters of the prosthesis on bone mineral content in controlled studies, such as the role of the shape, the position, the structure, the coating. Mineral content of biomaterials and bone grafts are taken into account. Focusing the X Ray beam allows ultrahigh resolution. Precise measurements of very small parts of bone such as rodent tibia or vertebra are possible. The good reproducibility (2 per cent) authorizes the evaluation of various parameters which modify bone remodeling, such as immobilization or activity, ovariectomy. Preventive or curative therapeutics which change bone mass can be evaluated in animal pre clinical studies. There are other methods of measurement of bone mineral content. Digitalization of radiographs is not sufficiently accurate and CT Scan generate high levels of radiation. The DEXA is actually the best compromise for an accurate and reproducible measurement of the bone mineral content in vivo. This method will certainly be an important tool in orthopedics for several clinical or animal investigations in the future.

Absorptiometry, Photon↗
PubMed1994

[The contribution of electronic podometry in the postoperative follow-up of feet with double arthrodesis surgery].

The resurgence of interest in electronic podometry, a technique known for many years, has led to its potential use for clinical evaluation. The authors assessed the reliability of the method by examining several patients after triple arthrodesis of the foot. Podometry offered a simple and inexpensive means of localizing and quantifying the areas of increased pressure, even in cases of wart or corn removal, of characterizing the foot type, and of showing the appearance or persistence of varus or valgus of the heel and its dynamic effects on gait. This information may be useful in the follow-up of patients with pain that is difficult to analyze postoperatively, especially in the case of occupational injury with increased subjective symptoms. This preoperative assessment may also give a more precise definition of the surgical indications, especially concerning technical details, as for example in realignment osteotomy of the first metatarsal.

Arthrodesis↗
PubMed1993

[Acetabulum without cement. Short-term results of a series of 112 threaded cups].

Between January 1982 and December 1987 we used 112 threaded acetabular cups in 102 patients undergoing total hip replacement. The clinical and radiographic results of 107 implants are reported in this survey. Using the functional grading of the hip advocated by Merle d'Aubigné and Postel, 62% can be classified as excellent, very good or good. On x-ray only 35% of the cups show neither radiolucency at the bone-implant interface nor migration of the component. There is a statistically significant correlation between a radiolucency in 2 of the 3 areas at the bone-implant interface and the clinical result. The revision rate for failure of the cup is 11.6% (13 implants). The actuarial survival of the threaded cup decreased from 0.95 in the 1st year to 0.75 in the 5th year after implantation. Analysis of our failures and of published data suggest that the problem lies in the lack of primary bone integration. We describe our difficulties in assessing risk factors, in interpreting the radiographs and in the intraoperative determination of component instability. The disappointing short term results have prompted us to abandon the use of threaded cups.

Acetabulum↗
PubMed1993

Diltiazem reduces the dose requirement for nitroprusside-induced hypotension.

The efficacy of diltiazem, a calcium channel blocker, for reducing the dose requirement for nitroprusside-induced hypotension was studied in 20 healthy patients during spine fusion for scoliosis. Anesthesia included methohexital (3 mg/kg followed by 3 mg.kg-1.h-1 intravenously), nitrous oxide, and alfentanil (40 micrograms/kg, followed by 0.7 microgram.kg-1.min-1 intravenously). Patients were assigned randomly to two groups, receiving either nitroprusside alone or nitroprusside and diltiazem (bolus of 80 micrograms/kg with two consecutive infusions of 4.5 micrograms.kg-1.min-1 during the first 30 min and then 1.3 micrograms.kg-1.min-1). Nitroprusside was used to maintain mean arterial pressure at 55-60 mm Hg in both groups. Hypotension was obtained in similar times, 4 min in the group receiving nitroprusside alone (range, 1-8 min) and 2 min in the group receiving nitroprusside and diltiazem (range, 1-8 min). Nitroprusside administration lasted 186 +/- 17 min (mean +/- SEM) in the group receiving nitroprusside alone and 214 +/- 26 min (mean +/- SEM) in the other group (NS). After hypotension, arterial blood pressure returned to its initial value in a time of 7 min in the group receiving nitroprusside alone (range, 5-9 min) and 9 min in the group receiving nitroprusside and diltiazem (range, 7-13 min) (NS). Cumulative doses of nitroprusside were larger in the group receiving nitroprusside alone (0.47 +/- 0.07 mg/kg; mean +/- SEM) than in the other group (0.24 +/- 0.05 mg/kg; mean +/- SEM) (P < 0.01). Significant increase in plasma thiocyanate concentration, cardiac index, and heart rate was observed only in the group receiving nitroprusside alone, but no intergroup differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Value of cutaneous expansion in the repair of skin defects after posterior surgical intervention on the spine].

Tissue expansion spreads widely its field of application through the treatment of large cutaneous defects. Spinal surgery represents a new field for this technique. Iterative and large posterior midline approach can lead to skin necrosis and deep infection which imposes a second look attempt with ablation of orthopaedic devices. Tissue expansion associated with advancement flaps represents a less aggressive choice to treat such post-surgical complications saving regional skin and muscles rather than with conventional flaps. The authors report four cases in which such a technique was applied with long term satisfactory results.

Adult↗
PubMed1992

Long-term hypotensive technique with nicardipine and nitroprusside during isoflurane anesthesia for spinal surgery.

Short-term infusion of nicardipine can be used to induce deliberate hypotension but may result in plasma drug accumulation. To assess long-term nicardipine administration for deliberate hypotension in 10 patients in a moderately hemodiluted state who were undergoing spinal surgery, hemodynamics and plasma nicardipine concentrations were concomitantly measured before and 20, 80, and 140 min after starting nicardipine, at drug discontinuation, and 20 and 80 min later. A dose of 6.2 +/- 0.9 mg (mean +/- SEM) of nicardipine was initially required to obtain mean arterial blood pressures at 55-60 mm Hg. Maintenance doses of nicardipine were 3-5 mg/h. The duration of nicardipine administration was 270 +/- 20 min (mean +/- SEM). Hypotension was associated with decreased systemic and pulmonary vascular resistances, increased cardiac index, and decreased arteriovenous difference in O2 contents. Only two patients required homologous blood transfusion. Plasma nicardipine concentrations peaked at 110 +/- 21 ng/mL (mean +/- SEM) and then decreased to 38 +/- 11 ng/mL (mean +/- SEM) without changes in arterial blood pressure. After vasodilator discontinuation, hypotension was observed during a mean time of 43 min (range 27-88 min) despite plasma concentrations less than 20 ng/mL. No relationship was found between plasma nicardipine concentrations and hemodynamics. These findings suggest that an increasing effect of nicardipine over time may occur during prolonged administration. Because the reasons for this hysteresis remain unclear, use of nicardipine infusion during major surgery and anesthesia requires particular caution.

Adult↗
PubMed1992

[Fracture of the femoral neck complicating algodystrophy of the hip during pregnancy. Apropos of 2 cases].

The authors report 2 cases of fracture of the femoral neck in pregnant women. This is a serious complication of a poorly understood disease, algodystrophy of the hip during pregnancy (transient osteoporosis of the hip of pregnancy, as referred by Anglo-saxon practitioners), whose main clinical, paraclinical and course characteristics are reported. The risk of subcapital fracture is maximal during the period of term, justifying recumbency in painful forms. In spite of the phantom appearance of the femoral head and neck, this type of fractures should not be confused with tumoral osteolysis, since they always unite within usual intervals.

Adult↗
PubMed1992

[Bone anchorage and surface condition of the implant. Validity of extraction tests].

The mechanical strength of the bone-implant interface depends on the morphology and the composition of the implant surface. The great variety of coating materials as well as the condition of the surfaces to be covered, makes a comparative and preclinical evaluation of the different materials for prostheses necessary. The results, the validity and the limits of the extraction tests are discussed in this article.

Animals↗
PubMed1991

[Effects of intravenous clonidine on postoperative shivering].

A study was designed to assess the possible effects of intravenous clonidine on postoperative shivering. Fifty patients undergoing spinal fusion under isoflurane anaesthesia were randomly assigned to two groups (n = 25). Patients in one group were given intravenous clonidine (5 micrograms.kg-1 during the first hour, and 0.3 microgram.kg-1.h-1 thereafter) or placebo. Shivering intensity (rated from 0 to 2) and pulmonary artery blood temperature (theta) was recorded every ten minutes for two hours. Haemodynamic and metabolic data were obtained by way of a Swan-Ganz catheter prior to administering the test drug, and then after 1 and 2 hours. On arrival at the recovery room, theta was 36.2 +/- 0.3 degrees C in the clonidine group, and 36.5 +/- 0.2 degrees C in the placebo group. There were no significant differences in shivering between the two groups. Clonidine significantly decreased blood pressure, heart rate, cardiac output and whole body oxygen consumption. The patients in these series were free from any cardiac disease. Further studies are required to assess the possible beneficial effects of clonidine on postoperative oxygen consumption in patients suffering from heart failure.

Adult↗