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Biomedical subjects

S Giannini

Publications and source records attributed to S Giannini.

At least 73 records · Page 4Linked to original sources
PubMed2000

Risk factors for intraoperative femoral fractures during total hip replacement.

BACKGROUND AND AIMS: Intraoperative femoral fractures are a serious complication of total hip replacement. The purpose of this study was to evaluate the risk factors of intraoperative femoral fractures in a retrospective analysis of a series of 3,566 total hip replacements. MATERIALS AND METHODS: The patients were divided into two groups, A and B. Group A patients had no intraoperative femoral fractures and Group B patients had intraoperative femoral fractures. In Group A there were 3,483 patients (97.7%) and in Group B, 83 (2.3%). The following potential risk factors were evaluated: sex, age, diagnosis, previous surgery at the homolateral hip, surgical approach, fixation type of the femoral component, prosthesis type, surgical stage during which the fracture occurred, and the lead operating surgeon. RESULTS: The fracture incidence was higher in females (p < 0.005) in uncemented femoral components (p = 0.005), in patients who had previous surgery at the homolateral hip (p < 0.005), and in revision surgery (p < 0.005). CONCLUSION: The analysis of intraoperative femoral fracture risk factors should allow the surgeon to improve the surgical performance and therefore reduce the incidence of this severe intraoperative complication.

Adult↗
PubMed1999

Human glomerular endothelial cells IGFBPs are regulated by IGF-I and TGF-beta1.

The release of insulin-like growth factor binding proteins (IGFBPs) and their regulation in human glomerular endothelial cells (GENC) was characterised. GENC produce IGFBP-4, IGFBP-2 and IGFBP-3 and express mRNA for IGFBP-2 to IGFBP-5. Due to the fact that IGF-I and TGF-beta1 modulate glomerular hypertrophy, their action on IGFBP release and GENC growth was studied. IGF-I increased IGFBP-3, IGFBP-2 and decreased IGFBP-4, while TGF-beta1 decreased IGFBP-3 and apparently increased IGFBP-4. All of the IGFBPs, except the TGF-beta1-regulated IGFBP-4, were modulated at mRNA level. IGF-I stimulated GENC proliferation, while TGF-beta1 inhibited their growth. It was demonstrated that an IGFBP-3 antibody reduced GENC proliferation. However, rhIGFBP-3 alone had no effect on GENC, but after 48 h pre-incubation the IGF-I stimulated GENC growth was increased, suggesting that IGFBP-3 could modulate the IGF-I induced GENC proliferation. It was concluded that the stimulatory IGFBP-3 and the inhibitory IGFBP-4 could regulate GENC growth, although the IGFBP-3 seems to have a predominant effect in this control.

Cell Division↗
PubMed1999

Electron transfer kinetics of caa3 oxidase from Bacillus stearothermophilus: a hypothesis for thermophilicity.

The O2 reaction and the reverse electron transfer of the thermophilic caa3 terminal oxidase of Bacillus stearothermophilus have been studied by laser flash-photolysis. The results show that both reactions, although studied at a temperature of 20 degreesC, far from the optimal temperature of > 60 degreesC for caa3, follow a kinetic behavior essentially identical to that observed with the electrostatic complex between mammalian cyt c and cyt c oxidase. In the O2 reaction cyt a and cyt a3 are very quickly oxidized; cyt a is then re-reduced via CuA, whereas cyt c oxidation is apparently rate-limited by the oxidation of CuA. Upon photodissociation of the mixed valence-CO caa3, reverse electron transfer from the binuclear center to cyt a3+ (tau1 = 3 micros) and CuA2+ (tau2 = 64 micros) is observed, while cyt c is not reduced by any detectable level. These results seem to rule out accounting for enzymatic thermophilicity by altered kinetics of intramolecular electron transfer involving the cyt center in the reduced configuration, which is very fast. On the basis of these results and previous data, we propose that thermophilicity involves an increased activation barrier for the reduction of cyt a3-CuB in the configuration typical of the oxidized site.

Biophysical Phenomena↗
PubMed1999

Validation of a functional method for the estimation of hip joint centre location.

The present study assesses the accuracy with which the subject specific coordinates of the hip joint centre (HJC) in a pelvic anatomical frame can be estimated using different methods. The functional method was applied by calculating the centre of the best sphere described by the trajectory of markers placed on the thigh during several trials of hip rotations. Different prediction methods, proposed in the literature and in the present investigation, which estimate the HJC of adult subjects using regression equations and anthropometric measurements, were also assessed. The accuracy of each of the above-mentioned methods was investigated by comparing their predictions with measurements obtained on a sample of 11 male adult able-bodied volunteers using roentgen stereophotogrammetric analysis (RSA), assumed to provide the true HJC locations. Prediction methods estimated the HJC location at an average rms distance of 25-30 mm. The functional method performed significantly better and estimated HJCs within a rms distance of 13 mm on average. This result may be confidently generalised if the photogrammetric experiment is carefully conducted and an optimal analytical approach used. The method is therefore suggested for use in motion analysis when the subject's hip range of motion is not limited. In addition, the facts that it is not an invasive technique and that it has relatively small and un-biased errors, make it suitable for regression equations identification with no limit to sample size and population typology.

Adult↗
PubMed1999

Kinematics of the human ankle complex in passive flexion; a single degree of freedom system.

The restoration of original range and pattern of motion is the primary goal of joint replacement and ligament reconstruction. The objective of the present work is to investigate whether or not a preferred path of joint motion at the intact human ankle complex is exhibited during passive flexion. A rig was built to move the ankle complex through its range of flexion while applying only the minimum necessary load to drive ankle flexion. Joint motion was constrained only by the articular surfaces and the ligaments. The movements of the calcaneus, talus and fibula relative to the stationary tibia in seven cadaveric specimens were tracked with a stereophotogrammetric system. It was shown that the calcaneus follows a unique path of unresisted coupled motion relative to the tibia and that most of the motion occurred at the ankle, with little motion at the subtalar level. The calcaneofibular and the tibiocalcaneal ligaments showed near-isometric pattern of rotations. All specimens showed motion of the axis of rotation relative to the bones. Deviations from the unique path due to the application of load involved mostly subtalar motion and were resisted. The ankle complex exhibits one degree of unresisted freedom, the ankle behaving as a single degree of freedom mechanism and the subtalar as a flexible structure. We deduced that the calcaneofibular and tibiocalcaneal ligaments together with the articular surfaces guide ankle passive motion, other ligaments limit but do not guide motion.

Ankle Joint↗
PubMed1999

A geometric model of the human ankle joint.

A two-dimensional four-bar linkage model of the ankle joint is formulated to describe dorsi/plantarflexion in unloaded conditions as observed in passive tests on ankle complex specimens. The experiments demonstrated that the human ankle joint complex behaves as a single-degree-of-freedom system during passive motion, with a moving axis of rotation. The bulk of the movement occurred at the level of the ankle. Fibres within the calcaneofibular and tibiocalcaneal ligaments remained approximately isometric. The experiments showed that passive kinematics of the ankle complex is governed only by the articular surfaces and the ligaments. It was deduced that the ankle is a single-degree-of-freedom mechanism where mobility is allowed by the sliding of the articular surfaces upon each other and the isometric rotation of two ligaments about their origins and insertions, without tissue deformation. The linkage model is formed by the tibia/fibula and talus/calcaneus bone segments and by the calcaneofibular and tibiocalcaneal ligament segments. The model predicts the path of calcaneus motion, ligament orientations, instantaneous axis of rotation, and conjugate talus surface profile as observed in the experiments. Many features of ankle kinematics such as rolling and multiaxial rotation are elucidated. The geometrical model is a necessary preliminary step to the study of ankle joint stability in response to applied loads and can be used to predict the effects of changes to the original geometry of the intact joint. Careful reconstruction of the original geometry of the ligaments is necessary after injury or during total ankle replacement.

Ankle Injuries↗
PubMed1999

An anatomically based protocol for the description of foot segment kinematics during gait.

OBJECTIVE: To design a technique for the in vivo description of ankle and other foot joint rotations to be applied in routine functional evaluation using non-invasive stereophotogrammetry. DESIGN: Position and orientation of tibia/fibula, calcaneus, mid-foot, 1st metatarsal and hallux segments were tracked during the stance phase of walking in nine asymptomatic subjects. Rigid clusters of reflective markers were used for foot segment pose estimation. Anatomical landmark calibration was applied for the reconstruction of anatomical landmarks. BACKGROUND: Previous studies have analysed only a limited number of joints or have proposed invasive techniques. METHODS: Anatomical landmark trajectories were reconstructed in the laboratory frame using data from the anatomical calibration procedure. Anatomical co-ordinate frames were defined using the obtained landmark trajectories. Joint co-ordinate systems were used to calculate corresponding joint rotations in all three anatomical planes. RESULTS: The patterns of the joint rotations were highly repeatable within subjects. Consistent patterns between subjects were also exhibited at most of the joints. CONCLUSION: The method proposed enables a detailed description of ankle and other foot joint rotations on an anatomical base. Joint rotations can therefore be expressed in the well-established terminology necessary for their clinical interpretation. RELEVANCE: Functional evaluation of patients affected by foot diseases has recently called for more detailed and non-invasive protocols for the description of foot joint rotations during gait. The proposed method can help clinicians to distinguish between normal and pathological pattern of foot joint rotations, and to quantitatively assess the restoration of normal function after treatment.

Adult↗
PubMed1999

Acute effects of moderate dietary protein restriction in patients with idiopathic hypercalciuria and calcium nephrolithiasis.

BACKGROUND: High dietary protein intake is a potential risk factor for nephrolithiasis because of its capacity to increase urinary calcium and to facilitate lithogenesis through many other mechanisms. OBJECTIVE: Our aim was to verify the effects of moderate protein restriction in hypercalciuric patients. DESIGN: We studied 18 patients (10 men and 8 women aged 45.6+/-12.3 y) with idiopathic hypercalciuria and renal calculi. Before and after 15 d of a diet with 0.8 g protein x kg(-1) x d(-1) and 955 mg Ca, all patients were evaluated for the main serum and urinary measures of calcium metabolism as well as for urinary uric acid, oxalate, citrate, and prostaglandin E2. RESULTS: Urinary excretion of urea fell after the diet (P < 0.001). Urinary calcium (P < 0.001), uric acid (P < 0.005), oxalate (P < 0.01), and hydroxyproline (P < 0.01) decreased after protein restriction, whereas urinary citrate increased (P < 0.025). Blood pH increased after the hypoproteic diet (P < 0.05). 1,25-Dihydroxycholecalciferol (calcitriol) concentration fell significantly (P < 0.025) and parathyroid hormone increased (P < 0.001). Creatinine clearance tended to decrease (106.4+/-4.8 compared with 97.5+/-5.7 mL/min) after the diet. The decrease in urinary uric acid after the diet correlated with calcitriol concentration (r = 0.57, P < 0.05) and the decrease in urinary urea correlated positively with that in hydroxyproline excretion (r = 0.58, P < 0.01). CONCLUSIONS: In hypercalciuric patients, moderate protein restriction decreases calcium excretion, mainly through a reduction in bone resorption and renal calcium loss; both are likely due to a decreased exogenous acid load. Moreover, dietary protein restriction ameliorates the entire lithogenic profile in these patients.

Calcium↗
PubMed1999

Analysis of function after intra-articular fracture of the os calcis.

Fractures of the os calcis with intra-articular involvement can cause difficulty in treatment and can result in abnormal function throughout the ankle-foot complex. We evaluated the function of the ankle-foot complex and the overall gait pattern after fracture of the os calcis, and we compared the results of surgical and nonsurgical treatment. Those in whom the geometry of the os calcis and joint was restored by reconstructive surgery had better compensation of gait and a better clinical-functional score. Complex disturbances in gait were found in the group of patients that did not undergo open reduction or internal fixation.

Adult↗
PubMed1999

Gait abnormalities in minimally impaired multiple sclerosis patients.

Subclinical evidence of gait abnormalities were identified in a group of seven patients with multiple sclerosis, EDSS scored 0 - 2, without functional limitations. A movement analysis technique was used to identify gait parameters indicative of impaired motor function during walking. Abnormalities related primarily to time-distance parameters (reduced speed of progression, shorter strides, prolonged double support phase) and muscular function (premature recruitment of gastrocnemius and late relaxation of tibialis anterior during stance phase) were identified regardless the severity of the clinical score. The gait analysis procedure was able to provide the clinician with evidence of motor abnormalities prior to functional disturbance observable by a trained physician. These minimal dysfunctions may have resulted from reflex mechanisms impaired by delayed transmission through long loop pathways or else as a result of a nonspecific protective gait strategy to improve balance control. The technique described in this study may be useful to identify earlier starting points for follow-up and physiotherapy.

Adult↗
PubMed1999

Autoantibodies to CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) in Caucasian patients with diabetes: effects on insulin release from human islets.

The type II transmembrane glycoprotein CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) has been proposed as a mediator of insulin secretion from pancreatic beta-cells and as a candidate for autoimmune reactions in type 2 diabetes. We evaluated the presence of anti-CD38 autoantibodies in Caucasian patients with diabetes and investigated the effect of these antibodies on insulin secretion from isolated human pancreatic islets. The presence of anti-CD38 autoantibodies was evaluated by using Western blot analysis in 236 patients with type 2 diabetes (mean age 63 years), in 160 patients with type 1 diabetes (mean age 38 years), and in 159 nondiabetic subjects. Anti-CD38 autoantibody titers at least 3 SD above the mean value of the control group were found in 9.7% of type 2 diabetic patients and in 13.1% of type 1 diabetic patients (chi2 = 15.9, P = 0.0003 vs. 1.3% of control subjects). No significant differences were observed in sex distribution, current age, age at diabetes onset, BMI, fasting serum glucose, or glycemic control between anti-CD38+ and anti-CD38-diabetic patients in either the type 2 or type 1 diabetic groups. The effect of 23 anti-CD38- and 13 anti-CD38+ sera on insulin secretion at low (3.3 mmol/l) or high (16.7 mmol/l) medium glucose concentrations was evaluated in isolated human pancreatic islets. Data are medians (interquartile range). The anti-CD38+ sera potentiated insulin release both at low [95 (64) vs. 23 (12) microU/ml of control incubations, respectively, P < 0.0001] and high [271 (336) vs. a control of 55 (37) microU/ml, respectively, P = 0.001] medium glucose concentrations, whereas the anti-CD38- sera did not. Furthermore, in the pooled data from all 36 tested sera, insulin levels in the islet incubation medium were directly related to the anti-CD38 antibody titer. We conclude that autoantibodies to CD38 are associated with both type 1 and type 2 diabetes in Caucasian subjects. These autoantibodies exert a stimulatory effect on insulin secretion by cultured human islets. The role of this autoimmune reaction in the pathogenesis of diabetes remains to be elucidated.

ADP-ribosyl Cyclase↗
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↗
PubMed1998

Data management in gait analysis for clinical applications.

OBJECTIVE: To study the reliability of gait analysis data obtained using the Calibrated Anatomical System Technique (CAST) protocol and to verify the suitability and repeatability of the extraction of a number of parameters from the waveforms obtained. DESIGN: The experimental protocol and the parametric analysis technique were applied on a population of able-bodied subjects. BACKGROUND: The clinical interpretation process of gait data still needs a more accurate analysis of the reliability and repeatability of the measurements and a suitable procedure for data reduction useful for data comparison. METHODS: Gait analysis was performed in 20 able-bodied subjects using a stereophotogrammetric system and a forceplate. 124 parameters relative to time-distance, kinematic and kinetic variables were calculated by means of an automatic procedure and statistically analysed. RESULTS: Most of the parameters were found to be normally distributed with relatively small range of variation. Few of them showed poor repeatability, mostly due to the experimental inaccuracies introduced. Correlation of several gait parameters with age, sex, and speed of progression was also identified.

Journal Article↗
PubMed1998

A comparison of hydroxyapatite-coated, titanium-coated, and uncoated tapered external-fixation pins. An in vivo study in sheep.

Three types of surfaces for external fixation pins were compared. One hundred and eight stainless-steel tapered 5/6-millimeter pins were divided into three groups: thirty-six pins remained uncoated (Group A), thirty-six were plasma-sprayed with hydroxyapatite (Group B), and thirty-six were plasma-sprayed with titanium (Group C). The pins were implanted in the left tibia of eighteen sheep, with each sheep receiving six pins from the same group. A unilateral fixator then was assembled on the pins. The medial aspect of the mid-part of the tibial diaphysis was exposed, and a five-millimeter-long cylinder of bone was removed so that load would be borne by the bone-pin interfaces. Six weeks after the procedure, radiographs demonstrated rarefaction of twenty-nine pin tracks in Group A, fifteen in Group B, and thirty in Group C (p = 0.021 for Group A compared with Group B and p = 0.016 for Group B compared with Group C). The mean final insertion torque (and standard deviation) was 4360+/-1050 newton-millimeters in Group A, 3420+/-676 newton-millimeters in Group B, and 3740+/-643 newton-millimeters in Group C. With the numbers available, no significant differences could be detected among these values. The mean extraction torque was 253+/-175 newton-millimeters in Group A, 3360+/-1260 newton-millimeters in Group B, and 1720+/-1030 newton-millimeters in Group C (p = 0.002 for Group A compared with Group B, p = 0.017 for Group A compared with Group C, and p = 0.03 for Group B compared with Group C). The extraction torque was significantly lower than the corresponding insertion torque in both Group A (p < 0.001) and Group C (p = 0.003); no significant difference could be found, with the numbers available, in Group B (hydroxyapatite-coated pins). At sixty times magnification, direct contact was seen along a mean of 16+/-9 per cent of the bone-pin interface in Group A, 30+/-12 per cent of the interface in Group B, and 28+/-15 per cent of the interface in Group C (p = 0.042 for Group A compared with Group C). However, at 10,000 times magnification, direct bone-pin contact was found only in Group B.

Animals↗
PubMed1998

Enhanced fixation with hydroxyapatite coated pins.

Three groups of seven patients had external fixation of middiaphyseal tibial fractures using uncoated pins, uncoated bicylindrical pins, and hydroxyapatite coated bicylindrical pins, respectively. All fractures were fixed with six pins, and all fractures united. Median pin insertion torque was 0.6, 1.2, and 1.3 Nm in the three groups, respectively. Median extraction torque was 0.1, 0.1, and 2.1 Nm, respectively. Both types of stainless steel pins showed a lower extraction torque than insertion torque in all cases, whereas the mean extraction torque in the hydroxyapatite coated pins was unchanged. Seven of the 14 patients receiving uncoated pins had pin tract infection, compared with none of the patients receiving hydroxyapatite coated pins. Hydroxyapatite coating of external fixation pins increases stability and thereby reduces the risk for pin tract infection and mechanical failure of fracture fixation.

Adolescent↗
PubMed1998

Bone density and skeletal metabolism are altered in idiopathic hypercalciuria.

OBJECTIVE: To study bone density in hypercalciuric patients, when classified according to the main metabolic defect. METHODS: We studied 49 patients, aged 19-60 years with calcium stones and idiopathic hypercalcuria. All subjects underwent an evaluation of mineral metabolism and a spinal and femoral DEXA measurement. Then, patients were classified as having Fasting (FH, 31 subjects) or Absorptive (AH, 18 patients) Hypercalciuria according to a standard oral calcium load. RESULTS: Spinal bone density was lower only in FH patients as compared to controls (p <0.001). Bone alkaline phosphatase and urine hydroxyproline were higher with respect to controls only in patients with FH (p <0.005 and p <0.015, respectively). After low calcium diet, hydroxyproline excretion continued to be higher in FH patients (p <0.05). Although in the normal range, serum and urine uric acid were higher in hypercalciuric subjects (p <0.03 and p <0.005, respectively); blood pH was lower in hypercalciuric patients than in controls (p <0.01). In FH patients urine hydroxyproline negatively correlated with spinal and femoral density (p <0.001 and p <0.005, respectively), and blood pH positively correlated with spinal density. CONCLUSIONS: a disordered bone metabolism and bone loss are present only in patients with fasting hypercalciuria. An excessive acid load, possibly of dietary origin, might be involved as a pathogenetic factor.

Absorptiometry, Photon↗
PubMed1997

Insulin-like growth factor binding protein production in bovine retinal endothelial cells.

Retinopathy is the most frequent microangiopathic complication in diabetes. Many circulating hormones and locally produced mitogenic factors have been involved. Bovine retinal endothelial cells (BRECs) were cultured to investigate if insulin, insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and a chronic high-glucose condition could control endothelial cell growth. Specific IGF-I receptors with two binding sites with high (Kd 0.03 nmol/L) and low (Kd 1.3 nmol/L) affinity were found when analyzing families of displacement curves between IGF-I versus IGF-I and IGF-I versus insulin. However, IGFs failed to be mitogenic factors in these cells. This could be explained by an inhibitory effect due to the presence of specific IGFBPs with a molecular weight between 24 and 43 kd. Using Western blot and immunoblot analysis, Northern blot study, and specific radioimmunoassay (RIA), these IGFBPs have been identified as IGFBP-3, -2, -5, and -4. Insulin, which does not bind to IGFBPs, was a potent mitogenic factor in these cells at a high concentration (10 nmol/L), suggesting a cross-reaction to IGF-I receptor. These IGFBPs, except the 24-kd form (IGFBP-4), were modulated by both IGF-I and IGF-II, with a maximum effect at 100 and 10 nmol/L, respectively. This regulation on IGFBPs was IGF-I receptor-independent. In fact, (1) IGFBP mRNA levels were not modified after stimulation with 100 nmol/L IGF-I, (2) 100 nmol/L IGF plus an equimolar concentration of alpha IR3 did not affect IGFBP production, (3) Des(1-3)IGF-I had no effect on IGFBP modulation, whereas at 10 nmol/L it enhanced BREC thymidine cell incorporation, and (4) 100 nmol/L insulin, which at this concentration can cross-react with the IGF-I receptor, did not modify the IGFBP pattern. Chronic exposure (4 weeks) of BRECs to 25 mmol/L glucose had no effect on cell growth. However, after 3 weeks, we observed a decreased IGFBP detection, and addition of 100 nmol/L IGF-I did not change IGFBP levels and did not modify cell growth. Conversely, BRECs grown in regular medium for 4 weeks showed increased IGFBP production. In conclusion, we showed that conditions mimicking hyperinsulinemia, rather than high levels of IGFs, could regulate BREC growth and that the IGF-I analog, Des(1-3), even with reduced affinity for IGFBPs but in part capable of binding to IGFBP-3, significantly stimulated BRECs growth only at 10 nmol/L. IGF actions are modulated by locally produced endothelial IGFBPs, and in turn, these endothelial IGFBPs are regulated, via in IGF-I receptor-independent mechanism, by the presence of IGFs. The autoregulatory IGF system together with the direct glucose modulation of IGFBPs could contribute in diabetic subjects to the retinal endothelial cell growth and metabolism through local changes in IGF bioavailability.

Animals↗