PubMed Health⌕ Search

Biomedical subjects

D P Greenwald

Publications and source records attributed to D P Greenwald.

At least 19 recordsLinked to original sources
PubMed1998

Aprotinin in ischemia-reperfusion injury: flap survival and neutrophil response in a rat skin flap model.

Multiple drugs have been used in experimental skin flap models to reduce the effects of reperfusion ischemia. The effects of antiproteases, however, have not been studied. A skin flap ischemia reperfusion model was developed in the rat to study the effects that aprotinin, a broad-spectrum antiserine protease, would have on skin flap viability. Thirty-two male rats underwent elevation of a ventral pedicled skin flap based on the superficial inferior epigastric artery. The flaps were subjected to 10 hr of warm ischemia by clamping the neurovascular pedicle followed by reperfusion. Aprotinin or saline (control) was administered systemically via the contralateral femoral vein either before or after the ischemic insult. Full-thickness skin biopsies were obtained at 1, 8, and 24 hr into reperfusion. Biopsies were evaluated for neutrophil concentration (using a myeloperoxidase [MPO] assay) and thromboxane B2 [TxB2] content. Flap survival was calculated at 1 week using standardized photography and computer-assisted digital imaging. Aprotinin given before an ischemic insult significantly improved flap survival compared to saline controls (52.3% alive vs. 29.6%, P = 0.0132, unpaired t-test). Aprotinin given after ischemia did not significantly influence flap survival (28.8% vs. 34.4% in saline controls, P = 0.708). MPO levels in the aprotinin preischemia treatment group were significantly less at 1 and 8 hr into reperfusion, indicating decreased neutrophil numbers. No statistical difference in TxB2 levels was noted in either group at any time after reperfusion. Aprotinin significantly improves skin flap survival when given prior to but not after an ischemic insult. Aprotinin appears to lower the concentration of neutrophils in skin flaps pretreated with the drug. Reperfused skin flap levels of thromboxane B2 are unaffected by the pre- or postischemic administration of aprotinin.

Analysis of Variance↗
PubMed1997

Biomechanical analysis of four-strand extensor tendon repair techniques.

Experience with flexor tendon repairs has suggested the superiority of the augmented Becker (MGH) technique for strength, toughness, and gap resistance. In an effort to apply these findings to the extensor tendons, 3 four-strand extensor tendon repair techniques were biomechanically tested in fresh human cadaver limbs: modified Bunnell, modified Krackow-Thomas, and MGH. Repairs were performed in Verdan's zone VI. Repaired tendons were distracted at constant speed until rupture. Tendon load and tendon distraction were continuously monitored. Benchmark values for load were measured as fingers were pulled from full metacarpophalangeal (MP) joint flexion to full extension, to 1-mm gap formation at the tenorrhaphy, and to complete rupture of the repair. The MGH repair proved significantly more resistant to gap formation (stronger and tougher) than the Bunnell and Krackow-Thomas repairs (p < .02). No differences were seen between groups in repair performance at MP joint extension and at complete rupture. This study suggests that the MGH technique has superior gap resistance to the other four-strand methods tested for extensor tendon repair in Verdan's zone VI. The MGH repair is recommended for extensor tendon repairs in zone VI when early postoperative motion regimens are considered.

Biomechanical Phenomena↗
PubMed1997

Metacarpal fracture angulation decreases flexor mechanical efficiency in human hands.

The most common fracture of the hand occurs at the neck of the metacarpal. Despite clinical studies, controversy remains as to how much fracture angulation should be tolerated before more aggressive reduction is required. A controlled biomechanical model was used to simulate fifth metacarpal head fractures in fresh human cadaveric hands. Fracture angulation was varied from 0 to 90 degrees at 10-degree intervals. We measured tendon excursion, tendon load, and work required to flex the small finger from full extension to full flexion with 10-degree incremental increases in vertex-dorsal angulation. Repeated measures analysis of variance revealed a significant decay in the efficiency of the flexor system when fracture angulation exceeded 30 degrees. Tendon excursion, load, and work requirements were all increased, confirming the detrimental effect of excessive fracture angulation on hand mechanics and function.

Biomechanical Phenomena↗
PubMed1997

Incidence and natural history of saline-filled breast implant deflations: comparison of blunt-tipped versus cutting and tapered needles.

The silicone shells of breast implants are known to fail. When failure occurs in saline-filled implants, the consequences are always ultimately symptomatic. Failure may be due to shell elastomer fatigue, fold-flaw cracking, faulty valve mechanisms, trauma, and microperforations (defined as perforations that are too small to be seen with the unassisted eye). To determine the incidence and natural history of microperforations, a major manufacturer of saline-filled breast implants was contacted. Over a 30-month period, 289,033 saline implants were sold, and 2844 were subsequently returned due to perioperative deflation. By using a rigorous and reproducible method of evaluating returned deflated saline-filled breast implants, it was found that 197 (0.068 percent of all implants sold) sustained needle damage at the time of insertion and went on to deflate within 6 months. Of the implants returned, overall 6.93 percent were found to have sustained needle trauma as the cause of the deflation, and the incidence appears to be increasing with time. The actual incidence of needle-related deflations may be significantly greater, since these data reflect only those implants which are voluntarily returned to the manufacturer. As a second part of this study, a segment of the silicone shell from a saline-filled breast implant was tested to determine the resistance to puncture using blunt-tipped, tapered, and cutting needles. The blunt-tipped needle required 6.6 times more force to puncture the shell than a cutting needle (p = 0.0011) and 3.2 times more force than a tapered needle (p = 0.0052). The difference in force needed to puncture the shell for a tapered and a cutting needle was not statistically significantly different (p = 0.5045). Microperforations do occur in the operating room and are responsible for a significant percentage of early (less than 6 months) deflations. Blunt needles require significantly more force to puncture the shell of an implant than do cutting and tapered needles, and their use may reduce the incidence of microperforations and subsequent implant deflations.

Breast Implants↗
PubMed1997

Optimization of the MGH repair using an algorithm for tenorrhaphy evaluation.

Previous investigations have demonstrated the superior strength and toughness of the MGH four-strand tendon repair technique and shown that it neither weakens during maximum tendon softening nor interferes with healing in an in vivo rabbit model. In the current study, the biomechanical performance of the modified Becker (MGH) and the modified Kessler repairs were compared in situ using a dynamic human cadaveric model to evaluate strength, toughness, glide efficiency, and operator variability. Three different surgeons performed a total of 42 zone II flexor digitorum profundus repairs in 14 fresh human cadaver hands. The modified Becker (MGH) repairs were stronger (79 +/- 3 versus 64 +/- 4 N; p < 0.01) and tougher (0.092 +/- 0.002 versus 0.078 +/- 0.003 J; p < 0.01) than the Kessler repairs while allowing equally efficient glide (32 +/- 6 versus 33 +/- 4 percent; p > 0.9). Strength was operator-dependent only for the modified Kessler repair (p < 0.005). We then established the optimal configuration of the MGH tenorrhaphy (number of preloaded crosses on either side of the tendon transection) by examining gap resistance ex vivo. Fifty-one MGH flexor tendon repairs were performed on explanted fresh human cadaver tendons. The experimental groups were randomly assigned to receive 0, 1, 2, 3, or 4 crosses on each side of the tenorrhaphy. Strength and toughness to gap formation and to ultimate failure were assessed tensiometrically. The MGH two-cross configuration was most resistant to gap formation (peak load 39 +/- 3 N; p < 0.05), establishing this configuration as the optimal design of this four-strand crisscrossing repair technique. The augmented Becker (MGH) repair is significantly stronger and tougher than the modified Kessler repair and demonstrates no operator dependence. It is a superior technique for zone II tenorrhaphy in the human hand. An algorithm is presented as a systematic approach that includes the important elements necessary for the rigorous biomechanical evaluation of any tendon repair technique.

Algorithms↗
PubMed1996

Anatomy, physiology, and functional restoration of the thumb.

The essential prehensile nature of the human hand rests on the presence of a mobile, sensate thumb with adequate stability and length. The true significance of the thumb-to-hand function is variable and dependent on a person's vocation, expectations, and needs. The frequently stated opinion that the thumb represents 40% of hand function is too exacting and does not allow for flexibility in evaluating a patient's requirements after thumb injury or loss. It is our approach to consider each patient's specific needs for individualized planning of thumb reconstruction. The patient can often offer useful information regarding need for strength vs. precision, width of hand vs. requirements for fine motor function, and concern for the aesthetic nature of an abnormal thumb vs. the variable deformities resultant from thumb reconstruction. We offer a review of the basic anatomy and physiology of the human thumb, with emphasis on hand-and-thumb function. We present the alternatives for thumb reconstruction, the advantages and disadvantages, and the relationships to a specific patient's needs. Clinical examples of various methods of thumb reconstruction, including metacarpal lengthening, phalangization, osteoplastic reconstruction, pollicization, and toe-to-hand transfer are provided.

Amputation, Traumatic↗
PubMed1996

Effects of laser versus scalpel tenolysis in the rabbit flexor tendon.

The use of surgical lasers has been shown to decrease adhesion formation as compared with scalpel control groups in various surgical procedures. The potential benefits of laser technology have not been assessed in the treatment of adherent tendons. The current study was designed to first develop a reliable and reproducible model for consistent adhesion formation following flexor tendon trauma. The second goal was to compare the effects of laser tenolysis procedures on tendon gliding with those of traditional scalpel tenolysis. In phase I, the adhesion-induction model utilized bilateral standardized crush- abrasion injuries to the hind limb digital flexor tendons of New Zealand White rabbits. Following 4 weeks of immobilization, the animals were sacrificed, and peritendoneal adhesions were assessed biomechanically. A significantly higher maximal force was required to extract the adherent tendons from the foot as compared with nontraumatized control tendons. In phase II, six groups of animals underwent the same standardized tendon trauma. Four weeks later the rabbits were randomly assigned to undergo either CO2 laser or holmium:YAG laser tenolysis on one foot. Scalpel lysis was used on the contralateral foot and served as an intraindividual control. Biomechanical assessment was performed at 1, 2, and 4 weeks following tenolysis. Significantly less force was required to extract the treated tendons at 1 and 2 weeks following holmium:YAG laser tenolysis when compared with scalpel or CO2 laser tenolysis. After 4 weeks, differences between holmium:YAG and CO2 laser and scalpel treatment were no longer significant. Extracted tendons were pulled apart to failure, and no difference in breaking strength was noted between groups. We conclude that holmium:YAG laser tenolysis results in easier tendon gliding as compared with scalpel or CO2 laser tenolysis at early time points. Laser tenolysis does not affect intrinsic tendon strength.

Anesthesia, General↗
PubMed1996

Mechanical analysis of explanted silicone breast implants.

Smooth-walled silicone gel breast implants (n = 25) were removed from 15 women after implantation times that varied from 23 to 216 months (mean = 117 months; SEM = 12.9). Strips of implant shells were tested to failure by computer-controlled tensiometer. Regression analysis revealed significant negative correlation between age of implantation and shell strength (p < 0.05), shell toughness (p < 0.05), and shell elasticity (p < 0.05). These data suggest that exposure to the in vivo environment weakens silicone gel breast implant shells over time.

Breast Implants↗
PubMed1995

Augmented Becker versus modified Kessler tenorrhaphy in monkeys: dynamic mechanical analysis.

The strength and gliding efficiency of an augmented Becker and Kessler tendon repair techniques were compared in fresh cadaver macaque monkey hands. Gliding efficiency was determined by comparing tendon work and load measurements made during tendon excursion to full fist with the same measurements made after tendon repair. Repair strength was then determined by tendon distraction to complete repair rupture. Data were gathered by computer controlled tensiometer and analyzed by factorial and repeated measures ANOVA. The augmented Becker repairs were significantly stronger than Kessler repairs. Repaired tendons required more load and work to bring the fingers into full fist; both repair types resulted in gliding efficiencies of 30% compared to intact controls. The augmented Becker repair is significantly stronger in situ than the modified Kessler and is recommended when early postoperative motion regimens are planned.

Analysis of Variance↗
PubMed1995

Debilitating silicone granuloma of the penis and scrotum.

The restoration and improvement of body contour have intrigued surgeons for over 100 years, generating much interest in the subcutaneous/intradermal injection of highly viscous fluids. The local complications of liquid silicone injection have been well documented over the past 30 years. Although Dow-Corning has not made medical-grade liquid silicone available for use in humans without an approved research application since 1966, practitioners, both licensed and unlicensed, have administered these injections worldwide for a variety of indications throughout the body. There is little or no information concerning the adulteration of these injectates. To date, there have been four case reports of penile injections--the indications being evenly split between the treatment of impotence/sexual inadequacy and augmentation. The most recent description was published in 1982. We present a case of debilitating silicone granuloma of the penis and scrotum secondary to large-volume injections into the corpora cavernosae and penile soft tissues administered in Belgium 14 years prior to presentation. The development of a silicone foreign body reaction, massive edema, and subsequent impotence lends itself to a clinical diagnosis and aggressive treatment with wide local excision and appropriate soft-tissue coverage. The metabolic fate of silicone in vivo remains inadequately characterized and a fertile area for research as new methods involving nuclear magnetic resonance spectroscopy have been devised to identify silicone and highly coordinated silicone complexes.

Adult↗
PubMed1994

Mechanical analysis of tendon suture techniques.

The relative strengths of seven methods of tendon repair were measured by mechanical disruption in an effort to determine the quality of a technique using loaded criss-crossing sutures and a running epitenon stitch. Fifty-seven calcaneus tendons were harvested from adult New Zealand white rabbits and randomized for transection. Standardized oblique transections were repaired with nylon using modified Halsted peripheral suture; modified Kessler technique; Kessler core stitch alone; running peripheral epitenon stitch; modified Becker technique #1; modified Becker technique #2; and a new augmented Becker repair. Sixteen additional rabbits each had bilateral tendon repairs in situ, one leg by Kessler and the other by the new augmented Becker repair technique. Half were lethally injected after 2 weeks and half after 4 weeks. Tenorrhaphies were pulled apart at constant speed until a gap of 1 mm was observed. Strength (maximum stress) and toughness (energy absorption to gap formation) were calculated. At time 0 the new augmented Becker repairs were the strongest, followed by the Kessler and Becker #2 tenorrhaphies. Kessler repairs were weaker at 2 weeks and then gained in strength; new augmented Becker repairs did not weaken at the 2-week point and demonstrated significant gains in strength after 4 weeks in vivo. The new augmented Becker repair was the strongest by a significant margin at all time points.

Animals↗
PubMed1993

Endogenous versus toxin-induced diabetes in rats: a mechanical comparison of two skin wound-healing models.

This study was designed to compare skin wound healing in three groups of Wistar rats: normal, genetically diabetic, and streptozotocin-induced diabetic. All diabetic animals received daily insulin. Full-thickness midline dorsal skin wounds were analyzed biomechanically for strength, toughness, and elasticity (Young's modulus) at 1 and 3 weeks after wounding. Wounds from normal controls were the strongest, toughest, and least compliant. Genetically diabetic rat wounds were the weakest and had the lowest elastic modulus. Wounds from the streptozotocin-induced rats were intermediate for all parameters measured (ANOVA, p = 0.001). Toxin-induced diabetes is less detrimental to skin wound healing than diabetes of endogenous origin. Whether this is due to basic differences in the models or to differences in duration of diabetes is unknown.

Animals↗
PubMed1993

Effects of constant mechanical tension on the healing of rabbit flexor tendons.

The biomechanical effects of constant mechanical load on tendon repair in vitro were determined for rabbit flexor tendons. Tendons were removed from Zone II, transected, reapproximated with four simple sutures, and cultured in standard medium. Tendons from the right forelimbs were loaded with 3.1-g weights; tendons from the contralateral forelimbs served as unloaded tendons. Tenorrhaphies were disrupted at zero, one, three, and six weeks postsuturing by fixed-speed tensiometry. True maximum stress (strength), normalized energy absorbed, and tangent modulus steadily increased over time, becoming significantly greater than unincubated controls in the loaded and unloaded groups at six weeks. True strain at maximum stress increased with duration for unloaded tendons; after six weeks it was significantly greater than unincubated control tendons. This study demonstrates a method for quantifying the biomechanics of tendon after intrinsic tendon segment healing and presents the first biomechanical evaluation of constant tension applied across the laceration site during an in vitro healing phase.

Animals↗
PubMed1992

Full-thickness skin wound explants in tissue culture: a mechanical evaluation of healing.

This study was designed to evaluate biomechanically defined wound healing in full-thickness skin explants in tissue culture. The requirement for preculture incubation of wounds in situ was characterized. Full-thickness skin incisions were made in 44 rats and closed immediately. Wounds were incubated in situ for 0, 12, 24, 36, 48, 72, or 96 hours before harvesting and placement into tissue culture media for 6 weeks. Healing was evaluated by biomechanical criteria: tensiometric distraction to wound rupture generated true stress and energy absorption data. Burst-strength (maximum true stress) and toughness (energy absorption) were five times higher in the 48-hour group than in any other group; other groups were not different from each other. This study demonstrates long-term survival of full-thickness skin in culture and shows that full-thickness skin explants heal in tissue culture. Possible explanations for the narrow window of opportunity for harvest (48 hours, no more and no less) are discussed.

Animals↗
PubMed1991

Family psychoeducation, social skills training, and maintenance chemotherapy in the aftercare treatment of schizophrenia. II. Two-year effects of a controlled study on relapse and adjustment. Environmental-Personal Indicators in the Course of Schizophrenia (EPICS) Research Group.

We demonstrated earlier that a novel family psychoeducational approach and an individual social skills training approach designed for patients living in high-expressed emotion households each reduced schizophrenic relapse by one-half when compared with medication controls in the 1st year after hospital discharge. The combination of treatments resulted in no relapse. Results have now been obtained after 2 years of continuous treatment. By 24 months, a persistent and significant effect of family intervention on forestalling relapse was observed, but the effect of social skills training was lost late in the 2nd year. There was no additive effect on relapse that accrued to the combination of treatments. Beyond 2 years, however, the effect of family intervention was likely compromised as well. Treatment effects on the adjustment of survivors were circumscribed, due, in part, to study design characteristics. Effects generally favored the social skills-alone condition at 1 year and the family condition or combined family/social skills condition at 2 years.

Adult↗
PubMed1991

Skin closure with dye-enhanced laser welding and fibrinogen.

The topical application of wavelength-specific dye and fibrinogen has been used to enhance laser closure of vascular anastomoses. We compared the closure of skin incisions by two different dye-enhanced, fibrinogen-based laser welding systems [argon laser (power density 4.78 W/cm2) with fluorescein isothiocyanate dye (n = 32) and diode laser (power density 9.55 W/cm2) with indocyanine green dye (n = 32)] with closure by interrupted 5-0 nylon suture (n = 64) and examined tensile strength, hydroxyproline production, histology, and cosmesis. Two 3-cm full-thickness incisions were made on the shaved backs of 64 rats. One incision was closed with suture, whereas the other, after treatment with the appropriate dye, was welded with either argon- or diode-lasered fibrinogen. At postoperative days 5, 10, 15, and 28, the closure sites were harvested and sectioned for analysis. Initially, wounds closed with argon-lasered fibrinogen showed less inflammatory response, greater collagen production (34.61 +/- 0.74 mg/gm), and greater mean peak stress at rupture (64.85 lbs/in2) than those closed with suture (16.42 +/- 3.20 mg/gm, 26.68 lbs/in2) (p less than 0.05). By 15 days, both argon and diode laser closures are superior in strength and collagen production to suture closure (p less than 0.05). At 28 days, diode laser closures (1315.60 lbs/in2) are stronger than suture closures (998.09 lbs/in2), whereas both are stronger than argon laser closures (813.16 lbs/in2) (p less than 0.05). Cosmetically, argon-welded wounds consistently appeared finer and lacked cross-hatched suture scars.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗