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Biomedical subjects

L C Argenta

Publications and source records attributed to L C Argenta.

At least 37 records · Page 2Linked to original sources
PubMed1996

A technique for cranial bone expansion.

There are several techniques for cranial bone remodeling available to the craniofacial surgeon. We present a method for expanding the cranial bone to reconstruct large cranial defects or contour large abnormalities using a progressive series of tongue-and-groove extensions of local cranial bone plates. This technique has been used by the senior author in more than 95 cases with a 6-month to 15-year follow-up. This technique offers several advantages over traditional cranial remodeling techniques, including three-dimensional stabilization of the remodeled calvaria, use of local tissue obviating the need for distant donor tissue or nonautologous biomaterials, greater flexibility in the modeling of the cranial bone, and a controlled decrease in the size of the remaining craniectomy defects, thus improving potential for cranial bone regeneration and closure. Although cranial bone expansion is not applicable or even necessary in all craniofacial procedures, it nevertheless is a valuable tool of the craniofacial surgeon.

Adolescent↗
PubMed1996

Cerebral perfusion defects secondary to simple craniosynostosis.

Premature fusion of multiple cranial sutures has been associated with increased intracranial pressure and the potential for mental impairment. Isolated craniosynostosis, however, has been thought to be a benign condition primarily reconstructed for aesthetic purposes. On the basis of subjective developmental improvement postoperatively, an objective radiographic analysis (single positron emission computed tomography [SPECT] was used to assess differences in cerebral perfusion in the areas compressed secondary to the fused cranial suture both before and after cranial reconstructive surgery in patients with simple craniosynostosis. Seven children with craniosynostosis, six boys and one girl (age age, 3-28 months), were enrolled in this prospective study. Six of the seven had cranial asymmetry on preoperative cranial computed tomographic scans, and one had a symmetric defect and was used as a control. Each subject had a preoperative SPECT scan approximately 3 to 5 days before the cranial reconstruction procedure and a follow-up scan 6 to 10 weeks postoperatively. Preoperative asymmetries in cerebral perfusion ranged from 0 to 30% (mean, 13%) the areas compressed secondary to the premature suture fusion. In five patients cerebral blood flow, which was asymmetric before surgery, became symmetric after craniofacial reconstruction, and no new perfusion defects were documented. The control patient and one another patient had symmetric perfusion both pre- and postoperatively. Craniosynostosis may be associated with decreased cerebral blood flow as a result of the constriction of the brain from the prematurely fused suture. The correction of asymmetric cranial single-suture synostosis is more than a cosmetic procedure in that it allows for normalization of cerebral blood flow. This difference in blood flow supports early surgical intervention to prevent any potential central nervous system compromise secondary to abnormal blood flow.

Brain↗
PubMed1996

Posttraumatic pseudolipoma.

A pseudolipoma is a benign fatty tumor whose etiology is undetermined but is postulated to be secondary to a tear in Scarpa's fascia resulting in herniation of deeper fat through Scarpa's layer. We report ten cases of trauma that resulted in pseudolipoma formation. The literature is reviewed and treatment options are discussed.

Adolescent↗
PubMed1996

Anatomic studies and clinical experience with fasciocutaneous flap closure of large myelomeningoceles.

Thirteen patients have undergone reconstruction of large lumbosacral myelomeningoceles with bilateral paralumbar fasciocutaneous flaps. Fasciocutaneous flap closure is supported by a rich vascular network with three main dominant vascular territories. In the middle third of the flaps, a prominent transverse segmental vascular pattern originating from the muscular perforators and lateral cutaneous branches of the costal groove segment of the lower intercostal arteries was noted. The parascapular and scapular fascial branches of the circumflex scapular artery supplied the upper lateral portion of the flaps. Prominent lateral extensions of the superficial circumflex iliac arterial system formed the dominant fascial vasculature of the lower lateral flap, richly arborizing with the middle segmental intercostal extensions. All 13 patients tolerated the procedure without blood transfusion and without perioperative complications. Stable, durable cutaneous coverage was achieved in all patients. Two postmortem neonate humans with large lumbosacral myelomeningoceles were studied angiographically. Radiopaque silicone-rubber-lead-chrome matrix (Microfil) was infused under physiologic pressures in a 7-day neonate after successful defect closure with bilateral fasciocutaneous flaps. The flaps were reevaluated postmortem, and high-contrast, digitally enhanced computed radiographic imaging confirmed the rich vascular support of the bilateral fasciocutaneous flaps, identifying the dominant vascular pedicles. Rich vascularity was further documented by photographing the orange opaque Microfil cast vessels through the reelevated flaps. A second postmortem (stillborn) myelomeningocele specimen was studied with barium infusion with particular emphasis on the anomalous lumbar aorta. Angiographic studies provide a new understanding of the unique vascular anatomy of both the anomaly and the paralumbar fasciocutaneous flap.

Aorta↗
PubMed1995

Warfarin-induced necrosis of the skin.

Warfarin (Coumadin)-induced necrosis of the skin is an unusual condition associated with the administration of warfarin. The necrotic lesions appear suddenly and are extremely painful. Single or multiple lesions develop in a distinct pattern. A hypercoagulable state created early in the course of warfarin administration is most likely responsible for warfarin-associated necrosis. Functional and inherited low levels of proteins C and S are found in some patients. The differential diagnosis of warfarin necrosis is of interest to the plastic surgeon. The condition may mimic purpura fulminans, necrotizing fasciitis, microembolization, breast cancer, and decubitus ulcers. Early recognition and treatment are essential to avoid significant and prolonged morbidity. Mortality has also been reported. We present 2 cases of warfarin-induced necrosis and a review of the literature.

Diagnosis, Differential↗
PubMed1994

Autologous denatured muscle as a nerve graft.

This study examined the use of freeze-thawed muscle as a nerve graft material in Sprague-Dawley rats. In Group 1 (n = 4), the sciatic nerve was isolated and the incision immediately closed. In Group 2 (n = 4), a 5-mm segment of the nerve was removed and immediately replaced. In Group 3 (n = 50), a 5-mm segment of nerve was removed and muscle (2 x 2 x 5 mm, harvested from the gluteus, frozen in liquid nitrogen, and thawed in sterile water) was sutured in place. The short 5-mm segment of muscle provided an ideal situation for regeneration of myelinated nerve. Sciatic functional indices were comparable in all groups after 8 weeks and at 1 year. Histologic analysis showed comparable nerve regeneration in Groups 2 and 3 at 4 months. Group 3 grafts exhibited new axonal growth distal to the repaired gap at 4 weeks; myelinated fibers were present at 10 weeks. At 1 year, Group 3 nerves had almost the same axon count as contralateral nerves. However, myelin-sheath regeneration in the 5-mm muscle graft was incomplete, at 81 percent of normal, at 1 year.

Animals↗
PubMed1993

Effects of prostaglandins and indomethacin on the cellular inflammatory response following surgical trauma in fetal rabbits.

This study has examined the effects of prostaglandins E2 and F2a (PGE2 and PGF2a) and indomethacin on cellular inflammation in fetal rabbits. Fetuses heal differently from adults: incisions heal with no scar or inflammation; excisional wounds exposed to amniotic fluid (AF) do not heal or become inflamed, and have high tissue levels of PGE2 and PGF2a; excisional wounds protected from AF do heal and become inflamed, and have low tissue PG levels. The authors inserted slow-release pellets [control, PGE2 (10 micrograms), PGF2a (10 micrograms), indomethacin (10 micrograms)] into subcutaneous pockets in fetal rabbits on day 25 of gestation (one per fetus). Pellets were also placed in subcutaneous pockets in the does. Fetuses and doe tissues were recovered 72 h after surgery. Control pellets in fetuses had a slight inflammatory response, with some cells present. Fetal PGE2 pellets had a layer 5-10 cells thick surrounding the pellet, and fetal PGF2a pellets had a 10-15-cell layer. Fetal indomethacin pellets had no response, with no inflammatory cells present. All pellets placed in does elicited a slight cellular inflammatory response, equal to that seen with control pellet in fetuses. These results show that PGE2 and PGF2a are potent in-vivo promoters of cellular inflammation in fetal rabbits, but not in adult rabbits. Indomethacin suppresses the foreign-body response in fetal rabbits, but not in adult rabbits.

Animals↗
PubMed1992

Arachidonic acid metabolites: effects on inflammation of fetal rabbit excisional wounds.

Uncovered fetal rabbit excisional wounds do not exhibit any classic signs of healing; wounds covered with an impermeable cover do contract, reepithelialize, and exhibit inflammation. Prostaglandin E2 (PGE2) is elevated in amniotic fluid, acting as an immunosuppressant at the maternal-fetal interface. Full-thickness excisional wounds were made on 25-day gestational age rabbit fetuses. Half the wounds were covered with an impermeable cover. Tissue from covered, uncovered, and nonwounded fetuses was examined 72 h after wounding for arachidonic acid metabolites. Uncovered wounds had significantly (P less than or equal to 0.05) elevated levels of PGE2, PGF2 alpha, and 12-HETE versus covered wounds and control tissue. Covered wounds had significantly elevated levels of 15-HETE compared to uncovered and control tissue. The elevated PGE2 in uncovered wounds may act as a fetal immunosuppressant; covered wounds (lower PGE2) developed cellular inflammation. Further investigations of these interactions may permit modulation of adult inflammation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1992

Surface area and tissue volume increases with differential expansion.

Increasing sophistication in generating soft tissue by tissue expansion has resulted in the evolution of differential expanders. These prostheses attempt to asymmetrically generate tissue for specific reconstruction, most commonly the breast. Using the pig model, differential expanders were placed in the rib area. A square grid was marked over the area, and the expander inflated. For each grid subunit, the surface area was calculated, the thickness measured, and the volume calculated. Subunits in the area of preferential expansion exhibited the greatest increase in surface area, however, these same subunits exhibited pronounced thinning of the tissue. The corresponding volume of these subunits was greater than that of nonexpanded subunits, but the increase was less than when comparing subunit surface area. All expanders were displaced superiorly during the course of inflation. These findings are of clinical significance in that the mastectomy scar and nipple reconstruction both are situated in the area of minimal thickness. Displacement of differential expanders must be anticipated so that the resultant inframammary fold will ultimately be symmetrical with the opposite side.

Animals↗
PubMed1992

Dentocutaneous fistula.

Chronic dental infection is the most common cause of draining sinus tracts of the face and neck. These lesions can be a diagnostic challenge to the clinician who is not familiar with dentocutaneous fistula. Diagnostic errors can result in multiple excisions, biopsies, and ineffective long-term antibiotic therapy. Patients may require excision of the fistula once the dental abscess has been successfully treated by root-canal therapy or extraction. Nine patients are reported.

Adolescent↗
PubMed1991

Cellular inflammation of fetal excisional wounds: effects of amniotic fluid exclusion.

The development of an cellular inflammatory response secondary to mechanical wounding has not been observed previously in the fetus. The effect of amniotic fluid exclusion on the inflammatory response in fetal rabbits subjected to full-thickness dorsal excisional wounds on day 25 of gestation (term = 31-32) was examined. The fetuses were either returned immediately to the uterus; a silicone cover was sutured over the wound; or a silicone cover with a centrally located hole was sutured over the wound. Seventy-two hours after wounding, uncovered wounds (19 live fetuses) exhibited only occasional inflammatory cells. Covered wounds (14 live fetuses) showed a pronounced cellular inflammatory response. Partially covered wounds (six live fetuses) showed a peripheral, intermediate response. The findings suggest that amniotic fluid contains factors inhibitory to inflammation, which the cover effectively excludes.

Amniotic Fluid↗
PubMed1991

The safety of intravenous fluorescein administration.

Intravenous fluorescein is frequently used to assess tissue perfusion and predict flap viability, although its safety has recently been questioned due to cardiovascular side effects. Vital signs of 50 patients who received fluorescein were monitored by anesthesiologist to assess flap viability. Blood pressure readings were recorded at 5-minute intervals for at least 1 hour before and after fluorescein administration. Repeated measure analysis of variance was performed to determine any significant sustained (greater than or equal to 30 minutes) or transient (less than or equal to 15 minutes) differences in pressure changes after fluorescein administration. No significant (p less than or equal to 0.1) differences in pressure were noted for any identifiable group of patients. Minor reactions included transient nausea with no vomiting (5), sustained blood pressure increases of greater than 10% preadministration values (9), transient pressure drops of greater than 10% (10), and sustained pressure drops of greater than 10% (4). These 4 patients responded to increased fluid therapy without need for pressor agents.

Adult↗
PubMed1991

The effects of partial and total amniotic fluid exclusion on excisional fetal rabbit wounds.

Previous studies have consistently demonstrated that fetal rabbit excisional wounds exposed to amniotic fluid do not heal in utero. This study examines fetal wounds covered to exclude amniotic fluid. Full-thickness excisional wounds were created on fetal rabbits on day 25 of gestation. The following three treatment groups were examined: uncovered (n = 19 live); covered, a silicone cover was sutured over the wound (n = 14 live); and donut, a silicone cover containing a 2-mm central hole was sutured over the wound (n = 6 live). Fetuses were returned to the uterus and harvested by cesarean section 72 hr postoperatively. Fetal (covered) wounds excluded from amniotic fluid contracted and reepithelialized up to confluence. Sixteen of 19 uncovered wounds expanded, 3 were unchanged; minimal reepithelialization was present in all wounds. Partially (donut) covered wounds exhibited an intermediate response. This study shows that excisional wounds in the rabbit fetus respond to injury by contracting and reepithelializing when excluded from amniotic fluid.

Amniotic Fluid↗
PubMed1991

In vitro adhesion of endogenous skin microorganisms to breast prostheses.

Bacterial proliferation on polymeric biomaterials varies with the material and microorganism. Subclinical infection is implicated frequently as the initiative factor in capsular contracture around breast prostheses. The ability of endogenous skin microorganisms to produce an exopolysaccharide "slime" is emerging as an important factor in biomaterial colonization. This study was designed to demonstrate the ability of microorganisms of varying slime productivity to colonize, in vitro, different kinds of breast prostheses. Six-millimeter disks from seven kinds of silicone prostheses and polyurethane foam were exposed to three radioactivity labeled strains of bacteria, one slime producer, and two non-slime producers, for 1 hour. Data were expressed as colony-forming units bound per disk. There was no significant difference in adherence between the bacterial strains used, suggesting that initial adherence was nonspecific. The adherence did not appear to be related to surface type, whether smooth or textured, nor to the polymeric composition of the implant material, whether silicone or polyurethane, nor to the presence or absence of slime. Also, adherence was consistent with expected nonspecific bacterial adherence to biomaterials.

Bacterial Adhesion↗
PubMed1991

Monodelphis domesticus: a model for early developmental wound healing.

Fetuses heal significantly differently than adults; amniotic fluid and the fetal environment have profound effects on the fetus' response to excisional wounding. The Brazilian gray short-tailed opossum (Monodelphis domesticus) is presented as a new model for early developmental wound healing. This is a small, docile, pouchless marsupial whose young, at birth, are equivalent to an 8-week gestational age human, which allows investigations of early developmental wound healing exclusive of the amniotic environment. Incisional and excisional wounds were made on the dorsum of pups 1 or 15 days after birth. The pups were killed 1, 3, or 6 days after wounding and were fixed for histology. All incisional wounds were bridged by keratinocytes within 24 hours. Day 1 excisional wounds healed 6 days after wounding with a hypertrophic layer of keratinocytes and no inflammation. Day 15 excisional wounds exhibited inflammation, focal necrosis, and healing by epithelial migration 6 days after wounding. This model allows for investigations into early developmental wound healing and exhibits responses dependent on age similar to prepartum and postpartum young of higher mammals.

Animals↗
PubMed1991

Analysis of silicon in human breast and capsular tissue surrounding prostheses and expanders.

Diffusion of polydimethylsiloxane from silicone breast prostheses and soft-tissue expanders has been associated with capsular contraction. We used electron dispersive x-ray analysis and scanning electron microscopy to assess the presence of silicon in capsular tissue surrounding three categories of breast prostheses and expanders. Breast and subcutaneous tissues external to the capsules were used as control specimens. Semiquantitative results allowed capsules to be ranked according to implant type. Silicon was localized within the inner 2.0 mm of capsular tissue. The analyses of tissues from 2 patients exhibiting unilateral, Baker grade IV contraction after bilateral placement of prostheses showed less silicon present in the severely contracted capsule than in the less-contracted capsule. Results from this study diminish the importance of silicon as the initiator of capsular contraction.

Breast Diseases↗
PubMed1991

Scalp necrosis in a neonate treated with cultured autologous keratinocytes.

A neonate compromised by a stressful labor, low birth weight, anemia, seizures, and enterocolitis developed necrosis of a caput succedaneum of the calvaria. Coverage with cultured autologous keratinocytes was successful and represents a treatment modality with minimal morbidity compared with conventional split-thickness skin grafts.

Birth Injuries↗