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Biomedical subjects

J A Spadaro

Publications and source records attributed to J A Spadaro.

At least 19 recordsLinked to original sources
PubMed1992

Bone formation near direct current electrodes with and without motion.

The osteogenesis induced in the medullary canal of rabbits by the implantation of moving and stationary wire electrodes was studied with and without the simultaneous application of 20-microA constant direct cathodic current. After 3 weeks, the formation of new trabecular bone in the canal was studied and measured microscopically. Electrically stimulated osteogenesis was not observed at stationary electrodes. As in previous studies with this model, a movable electrode alone stimulated new bone formation whose area was 7-10% of the canal area. The amount of this bone was not statistically increased by the addition of cathode current. Movable, electrically active cathodes were associated, however, with fluid-filled spaces incorporated within the new trabecular bone. When mechanical stimuli were controlled, we were not able to demonstrate that the direct current stainless steel cathode acts either as an inducer or a substantial enhancer of medullary osteogenesis.

Analysis of Variance↗
PubMed1992

A technique for measuring absolute toe pressures: evaluation of pressure-sensitive film techniques.

Although a number of pathologies of the forefoot in ballet dancers on pointe have been described, pressures and deforming forces have not been adequately measured. To evaluate the possible use of pressure-sensitive film (PSF) in measuring the pressures on the external soft tissues in such a confined space as the dancer's toe shoe, it was tested and calibrated with 20 cadaver toes. Each cadaver toe was internally stabilized and loaded longitudinally against PSF on a flat surface. The resultant films were analyzed with a video imaging system and the pressures and total forces were determined. Results showed that the linearity of the PSF to pressure had a regression value of 0.98. By using two sensitivity ranges of films, the total force measured by the PSF was found to be within 10% of the known applied force on each toe. The PSF, therefore, may very well be a useful and accurate method of measuring external soft tissue pressures on the forefoot.

Biomechanical Phenomena↗
PubMed1992

The effects of fat interposition for central-physeal defects. A histologic study in rabbits.

The effects of autogeneic fat interposition in a central cylindrical physeal defect were observed in rabbits. A 3.6-mm longitudinal drill hole was made across the physis of the distal femur, bilaterally, in four- to six-week-old New Zealand rabbits. One side was filled with an autogeneic fat graft and the contralateral defect was left as a control. The rabbits were killed at intervals during the remaining growth period, and the defects were examined histologically. Although fat grafts reduced the rate of osseous bridging across the physis and allowed more longitudinal growth than controls, transverse regeneration of the physis did not occur in the eight-week period preceding closure. The lack of physeal regeneration across the gap may reflect an important difference between central and peripheral defects.

Adipose Tissue↗
PubMed1991

Somatosensory cortical evoked potential changes after deformity correction.

The somatosensory cortical evoked potentials recorded during posterior spine fusion and instrumentation for 99 consecutive patients with idiopathic scoliosis, 18 years of age or younger, were retrospectively reviewed. The potentials were recorded from scalp electrodes while synchronously stimulating both tibial nerves near the ankles. Signal changes observed during consecutive 30-minute time intervals after deformity correction were analyzed. No changes in neurologic status were observed postoperatively. Latency values tended to remain constant on average. A small, but statistically significant, decrease in the first two interpeak amplitudes was observed during the first 30-minute interval after deformity correction. The first interpeak amplitude recovered, while the second remained statistically significantly decreased. No patient had a decrease of greater than 50% in both of the first two amplitudes, which persisted throughout the 60-minute interval immediately after deformity correction. This study demonstrated a tendency for somatosensory cortical evoked potential interpeak amplitudes to decrease during the first 30 minutes after deformity correction. There was a great deal of individual variation, including amplitude increases in many patients. There was no evidence supporting an association between dramatic, sustained amplitude decreases and uncomplicated deformity correction. The value of thoroughly evaluating somatosensory cortical evoked potential signal trends while making intraoperative decisions is emphasized.

Arthrodesis↗
PubMed1990

Electromagnetic effects on bone formation at implants in the medullary canal in rabbits.

This experiment was aimed at illuminating the relationship between electromagnetic and mechanical stimuli of bone formation when present simultaneously. Movable and stationary intramedullary wire implants were studied in rabbits treated with a pulsing electromagnetic field (PEMF) 4 h/day for 3 weeks, and were compared with identical control animals without PEMF. Trabecular bone formed routinely at spontaneously movable implants, but not at stationary ones. On average, PEMF-treated movable implants in the femur induced 44% more bone than untreated movable implants. Also, in the PEMF-treated femora, a 22% enlargement of the area of the medullary canal was observed compared with no-field controls. In the tibia, these effects were weak or nonexistent. The PEMF used did not induce bone at stationary implants, suggesting that under these conditions it is not a primary trigger in vivo.

Animals↗
PubMed1989

Variability of somatosensory cortical evoked potential monitoring during spinal surgery.

The intraoperative variability of somatosensory cortical evoked potentials (SCEPs) has been measured for 320 consecutive spinal surgeries and found to be a function of patient diagnosis, neuromuscular status, age, and procedural factors. In many cases, it is likely that this variability severely limits the reliability and usefulness of spinal cord monitoring in detecting early cord compromise. Patients with idiopathic scoliosis, spondylolisthesis, and pseudarthrosis have the smallest spontaneous variability and strongest amplitudes, while those with congenital, paralytic scoliosis, stenosis, or tumor have very variable, weak SCEPs. Patients with neurologic disorders, particularly cerebral palsy, myelomeningocele, Friedreich's ataxia, and peripheral deficits, also have high variability and weak amplitudes. A monitoring quality scoring system is proposed that may be useful during surgery in judging how well the SCEPs can discern surgically related changes in cord function from background variations.

Adult↗
PubMed1986

Mechanical factors in electrode-induced osteogenesis.

Previous experiments have suggested that mechanical activity of electrode implants may contribute to the observed bone formation that has been attributed to the electrical currents. This was tested by implanting movable and stationary wires in the medullary canal of the rabbit femora or tibiae. The moving implants uniformly showed significant medullary bone formation at the wire, whereas the stationary ones did not. This bone persisted for as long as 8 weeks and was mostly resorbed by 12 weeks as the implants became fixed. The new trabecular bone closely resembled that typically seen at electrically active implants. Implant motion may have a more important role in electrically induced osteogenesis than previously thought.

Animals↗
PubMed1986

Inhibitory effects of electrically activated silver material on cutaneous wound bacteria.

Silver has had a widespread application in the care of burn wounds and chronic skin ulcers. The in vitro evaluation of unbound ionic silver is reported in this study. A comparison is made between silver-coated fabric alone and the fabric acting under direct electric current anodization. A variety of commonly found predominant skin pathogens were tested in this comparative study. Our studies confirm previous reports demonstrating an effective penetration of the silver ion and its local antibacterial action. Accurate measurements of the bacteria-free "clear zones" surrounding the electrically activated silver-coated fabric showed these to be significantly larger than those of the silver fabric without electric stimulation. This method affords another option in the use of silver for its antibacterial property, i.e., by iontophoresis. Its potential clinical use awaits further in vivo trials.

Anti-Bacterial Agents↗
PubMed1982

Electrically enhanced osteogenesis at various metal cathodes.

Electrode-induced bone formation was studied at six different metallic cathode materials in the rabbit medullary canal. Direct cathodic currents of 0.02 and 0.2 microA/mm2 were applied for 21 days. Quantitative differences in new bone growth were found. Platinum, cobalt-chrome (F-90) and silver had more bone relative to controls at the lower geometric current density, while stainless steel (316L) and titanium cathodes were more effective at the higher current. On average, there was a significant increase (46-48%) in new bone formation at active versus control implants for either current level. No corresponding difference in the number of vascular channels were observed in the 21 day specimens. Metal-specific differences in bone formation at control implants were also found, with platinum being most stimulatory. These observations are consistent with an interfacial electrochemical mechanism for electrode stimulated osteogenesis, which perhaps acts in concert with purely electrical and mechanical forces.

Animals↗
PubMed1982

Silver antibacterial bone cement. Comparison with gentamicin in experimental osteomyelitis.

An animal model was used to evaluate and compare silver methacrylate with gentamicin methacrylate in experimental Staphylococcus osteomyelitis. One tibia from each of 54 rabbits was innoculated with 4 X 10(6) CFU of S. aureus and inserted with prepolymerized PMM rods containing either 1% Ag2SO4, 2.5% gentamicin, or no additives. By six weeks, the mortality rate was 61% in controls, 22% in Ag-PMM animals and 6% in gentamicin-PMM animals. Bacterial counts from the bone of dying and surviving animals were significantly lower than controls, 23.6% of controls for the Ag-PMM treated and 6.0% for the gentamicin-PMM treated groups. All surviving animals were culture positive, except for three sterile bones obtained from the gentamicin-PMM group. In light of these results and the favorable characteristics as an antimicrobial agent, further investigation of silver in bone cement (or other vehicles) for the prevention or treatment of bone infection appears warranted.

Animals↗
PubMed1980

Piezoelectricity in collagen films.

Tissue collagen exhibits several levels of structural organization, and this complicates efforts to determine the origin of its piezoelectricity. We made collagen films-by evaporation and electrodeposition from solution-and examined the relation between collagen's piezoelectricity and its electron microscopic appearance. We found that the electrodeposited films were more organized and exhibited higher piezoelectric coefficients than the evaporated films. Despite this, the evaporated films were piezoelectric, thereby suggesting that the effect originates either at the level of the tropocollagen molecule or, at most, with aggregated structures no larger than 50 A in diameter.

Chemical Phenomena↗
PubMed1979

Silver polymethyl methacrylate antibacterial bone cement.

An improved antibacterial bone cement was sought based on the addition of low concentrations of inorganic silver compounds to polymethyl methacrylate. Composites with AgCl, Ag-AgCl, Ag2O, Ag2SO4 and Ag3PO4 in concentrations of 0.05% to 1% by weight, were tested in vitro against bacterial cultures. All were effective, but Ag2SO4 was especially so, even after 7 weeks of incubation in normal saline. Compressive strength of the cement was not affected by these additions, except in the case of Ag2O. Biocompabibility tests in rabbit muscle for up to 12 weeks showed no significant difference between the Ag -PMM and plain PMM in tissue reactivity, both being minimal. These features, coupled with the broad spectrum of antibacterial activity and low allergic potential of silver, make Ag-PMM an attractive alternative to conventional organic antibiotic/bone cement composites.

Acrylic Resins↗
PubMed1978

Surface model of the collagen fibril as determined by two-stage plastic replica.

Two-stage plastic replicas of fresh and vacuum dried rat tail collagen were examined by electron microscopy. Microphotometer tracings made from the replica micrographs showed that the surface of the collagen has a periodic undulating topography which includes an approximately 20--40 A deep depression located within the major band distance.

Animals↗
PubMed1978

Treatment of orthopaedic infections with electrically generated silver ions. A preliminary report.

Electrically generated silver ions have been shown previously to be a potent antibacterial agent with an exceptionally broad spectrum as indicated by in vitro testing. The present study reports on clinical experience using electrically generated silver ions as adjunctive treatment in the management of chronic osteomyelitis. Fourteen patients had fifteen treatment attempts: thirteen for chronic osteomyelitis of the tibia, one for acute and chronic pyarthrosis and osteomyelitis of the knee, and one for a chronically draining sinus after total hip replacement. Wound débridement, silver ion iontophoresis, and subsequent wound care (usually provided by the patient) resulted in control of the infection in twelve of the fifteen treatment attempts and in healing of the non-union after follow-up ranging from three to thirty-six months. The other three attempts led to two partial and one complete failure.

Adult↗
PubMed1977

Clinical experiences with low intensity direct current stimulation of bone growth.

Low intensity direct current stimulation of bone growth involves the continuous application of cathodic currents in the nanoampere range. The technique has been applied to 13 patients with a variety of non-unions and pseudarthroses with a success rate of 77 per cent. Preliminary data indicate that a range of total energy, from 0.6 to 2.5 Joules, is maximally effective. The technique has been combined with anodic control of local bacterial infection with promising results. Both the osteogenic stimulation and the bacterial suppression techniques as described in this paper, appear to be safe and effective.

Adult↗
PubMed1976

Antifungal properties of electrically generated metallic ions.

A qualitative and quantitative investigation was undertaken to study the susceptibility of unicellular eucaryotic organisms (yeasts) to metallic cations generated by low levels of direct current. Results were characteristic of effects obtained previously using clinical and standard bacteria test organisms. The present study demonstrated that anodic silver (Ag(+)) at low direct currents had inhibitory and fungicidal properties. Broth dilution susceptibility tests were made on several species of Candida and one species of Torulopsis. Growth in all isolates was inhibited by concentrations of electrically generated silver ions between 0.5 and 4.7 mug/ml, and silver exhibited fungicidal properties at concentrations as low as 1.9 mug/ml. The inhibitory and fungicidal concentrations of electrically generated silver ions are lower than those reported for other silver compounds.

Antifungal Agents↗