Harold I. Friedman

Evaluation of porous polyethylene for external ear reconstruction

Autogenous rib cartilage and silicone rubber are materials currently used for ear reconstruction. Increased morbidity and operative time with rib cartilage grafts and a high rate of extrusion with silicone implants render them less than ideal for reconstruction of the human ear. The purpose of the current investigation is to determine the efficacy of porous polyethylene as an alternative synthetic material for ear reconstruction. Porous polyethylene and silicone rubber discs of equal sizes in two thicknesses were implanted in lieu of the cartilage in the external ear of eight baboons. Histological evaluation of the sites after nine weeks revealed excellent anchorage of the thin porous polyethylene implants (1.5 mm) in the surrounding tissues. Silicone rubber implants, however, were encapsulated in a thickened granulation tissue capsule. When thicker implants (3.0 mm) were used, exposure or extrusion occurred in all cases. Porous polyethylene implants demonstrated only partial exposure; half of the silicone rubber implants were extruded; and the other two silicone rubber implants were almost completely extruded. Porous polyethylene was thus better incorporated into the soft tissues than silicone rubber as long as the overlying soft tissues were not stressed by an oversized implant or inadequate soft tissue coverage.

An evidence-based appraisal of the use of hyperbaric oxygen on flaps and grafts.

Summary: Hyperbaric oxygen has been advocated, both as an adjunctive or primary form of treatment, for a variety of disorders, including gas gangrene, osteoradionecrosis, and carbon monoxide poisoning. It has also been used to improve ischemic wounds before skin grafting and to support ischemic flaps. In this review, we analyze the available literature that investigates the use of hyperbaric oxygen for composite grafts, skin grafts, random flaps, distant flaps, and free flaps. An appraisal of the level of evidence for each of these uses of hyperbaric oxygen is offered. Although there are a significant amount of animal data supporting the application of hyperbaric oxygen for grafts and flaps, there is very little clinical information other than case reports and series to sustain its choice over other modalities of therapy. Multicenter prospective clinical studies are clearly needed comparing hyperbaric oxygen to other mechanical or pharmacologic interventions to improve wound healing for grafting or to support flap survival.

The Connexin43 Carboxyl-Terminal Peptide ACT1 Modulates the Biological Response to Silicone Implants

Background: The implantation of a biomedical device elicits a wound-healing response that progresses through the three phases of wound healing: inflammation, cellular proliferation, and matrix remodeling. This response culminates in a fibrous collagen encapsulation of the implant. Subsequent contraction of this “scar-like” tissue can lead to physical disfigurement, implant extrusion, or impairment of implant function, necessitating surgical revision or removal. ACT1 is a synthetic peptide derived from the carboxyl-terminal sequence of the cellular gap junction protein connexin43. This novel peptide has recently been shown to modulate cutaneous wound healing, reduce scarring, and promote regenerative repair of the skin following injury. In this study, the authors investigated the ability of the ACT1 peptide to modulate the wound-healing response to biomedical device implantation. Methods: Silicone disks coated with either vehicle control or ACT1 peptide were implanted submuscularly into male Sprague-Dawley rats. Capsulectomies were performed on days 1, 2, 3, 14, and 28. The implant capsules and surrounding tissue were analyzed histologically and biochemically. Results: ACT1 modulated the wound-healing response to silicone implants by attenuating neutrophil infiltration, increasing vascularity of the capsule tissue, reducing type I collagen deposition around the implant, and reducing the continued presence of contractile myofibroblasts. Conclusion: ACT1 may provide an enabling technology for modulating the wound-healing response to implants, promoting integration of implanted materials and tissue-engineered devices in the human body.

Recurrent basal cell carcinoma in margin-positive tumors

The purpose of this investigation was (1) to determine the incidence of basal cell carcinoma (BCC) recurrence in patients who had microscopic evidence of residual tumor at the margin of resection and (2) to identify morphological characteristics that predispose to recurrence. Twenty-nine patients with margin-positive BCCs were found in a group of 339 patients who underwent BCC resection. Four patients were lost to follow-up. The remaining patients fell into two groups: 10 patients had their margin-positive tumors re-resected within 2 months and 15 patients were followed until a recurrence developed. The pathology slides of these patients were reviewed and certain features were noted, including histological type, pattern of infiltration, size of tumor, and anatomic site. None of the patients who had re-resection of their margin-positive lesions had a recurrence. All of the patients who did not undergo re-resection developed a recurrent tumor at the site of the original resection. The unexpectedly high rate of recurrence in the latter group may have been a consequence of a disproportionate number of tumors containing sclerosing (morpheaform), mixed (nodular and sclerosing), as well as multifocal (horizontally spreading) lesions. A more aggressive approach to margin-positive BCCs is recommended, particularly if the lesion has sclerosing or multifocal components.

Management of regional hidradenitis suppurativa with vacuum-assisted closure and split thickness skin grafts.

Background:Hidradenitis suppurativa can be a debilitating chronic illness. The underlying cause of the disease is still not clear, but effective treatment of widespread regional disease relies on resection of all the involved skin and subcutaneous tissue. Closure of the resulting large wound is dependent on either flap or skin graft coverage. Many of the resulting wounds are too large for flap closure or result in unacceptable flap donor site deficits. Methods:We present a series of 11 patients with 24 regional disease sites treated with a protocol of excision, followed by wound vacuum-assisted closure (VAC; KCI, San Antonio, TX) therapy to stimulate angiogenesis of exposed fat, and then skin grafting with the use of VAC to support the grafts on the recipient sites. Results:Only 3 of the patients required regrafting. One patient had a VAC failure because of poor patient compliance, and 1 patient had 4 sites that each required regrafting as the epithelium would not fill in the residual open areas as it usually did in other patients. All patients were cured of their local disease. Conclusions:Massive regional hidradenitis suppurativa can be successfully managed with wide excision, VAC therapy, and skin grafting to allow these patients to live normal and productive lives.

The fate of the fibrous capsule after saline implant removal.

After removal of a silicone breast implant, if a capsulectomy is not performed, the residual capsule may persist, become calcified, and appear on routine mammograms. The fate of the capsule around saline implants is less clear. The purpose of this study was to determine the fate of the capsule around saline-filled implants in an animal model. Rats were implanted with 6-ml tissue expanders, which were left in place for 4 months. The implants were then removed and the capsules around the injection port (smooth surface) and tissue expander (textured surface) were examined sequentially. The capsules contracted and dissipated gradually over a year in association with a pericapsular vascular proliferation. It may not be necessary to perform a capsulectomy at the time of saline implant removal.

Breast Implants: Facts, Controversy, and Speculations for Future Research

The breast implant crisis has been widely publicized. Beyond its immediate problems for the patients, the crisis has also discredited the use of silicone rubber as one of the most widely used biomaterials. Silicone elastomer or gel, the primary material in mammary prostheses, may be exposed to the bodys tissues via envelope rupture, gel bleed, or elastomer fragmentation. Local responses to silicone include granulomatous inflammation, capsular contraction, and infection, all in varying degrees depending on ill-defined factors, which may include patient condition, peri- and postoperative complications, and hereditary predisposition, as well as material properties such as surface texture. The theory that silicone breast implants cause immunological disorders has not been proven. However, further study is necessary because some patients report autoimmune-like disorders (human adjuvant disease) following implant placement. Like autoimmune disease, human adjuvant disease is characterized by abnormalities of the immune response, autoantibody formation, and chronic inflammation. Silicone has been shown to play the role of an adjuvant, providing constant nonspecific stimulation of the immune system. Some researchers have hypothesized the role of silicone in specific immune reactions, including immunoglobulin formation and T-cell activation. This report examines the role of silicone as an agent of disease, focusing on material surface-tissue interactions.

The Use of Biomedical Sensors to Monitor Capsule Formation Around Soft Tissue Implants

Piezoelectric sensors have been shown to respond reproducibly to changes in tissue mechanical properties surrounding an implant over a 4-month period. The vibrational amplitude at a frequency corresponding to the radial resonance shows a statistically significant change over time. The initial period of inflammation is marked by a significant reduction in amplitude, which is indicative of an increase in viscous dissipation of the tissue. As collagen displaces the cellular response, the amplitude continues to decrease. Finally, as the tissue matures, the capsule becomes stiffer, and the viscous dissipation lessens. These results are consistent with qualitative assessments of explanted capsules. Strain gauges encased in a monolithic block of silicone exhibited a greater degree of variability, yet show similar trends over time. The strain increases in the initial 4-week period and remains relatively steady over the following 4 weeks. Beyond 8 weeks, the gauges begin to extrude from the animal or suffer a loss of electrical continuity. Steps are being taken to improve the strain sensor longevity in the animals.

Electromechanical Impedance Sensor for In Vivo Monitoring the Body Reaction to Implants

A novel sensor for in situ monitoring of the body reaction to implants has been developed. A piezoelectric wafer active sensor was adapted for biomedical applications (bio-PWAS). A number of bio-PWAS sensors have been implanted in rats and left in place up to 64 days. The bio-PWAS were able to oscillate in several resonance modes, radial-wise (in-plane) and thickness-wise (out-of-plane). The electromechanical impedance was measured over a wide frequency band, covering several radial vibration modes and the first thickness mode. The recorded data was processed with impedance spectroscopy methods. Preliminary results indicate a correlation between the electromechanical impedance spectrum of the bio-PWAS and the state of implantation. Quantitative studies have shown that the first radial mode amplitude seems to correlate with the short-time inflammatory and immune response, while the thickness mode amplitude seems to correlate with both the short-term inflammatory response and long-term encapsulation and fibrosis response. Since radial vibrations generate shear waves in the surrounding tissue, while thickness vibrations generate pressure waves, it seems that the shear and pressure wave interactions have specificity in detecting the different stages of the bodys reaction response to implants. These observations were supported by histological examinations of the tissue surrounding the bio-PWAS. Though these initial results are encouraging, further experiments need to be conducted and more data needs to be collected in correlation with histological determinations. In-depth impedance spectroscopy studies should be conducted on this extensive data and closely correlated with extensive histological studies.

Management of head and neck burns.

Treatment of burn injuries of the head and neck can be divided into acute and chronic stages. The acute phase consists of physiologic resuscitation of the patient and early care of the burn wound. The chronic stage begins from completion of wound coverage until the wound has matured. A major advance in the care of the patient with head and neck burns has been the realization that clinical application of exercise, traction, and pressure can reduce the development of contractures and hypertrophic scarring. Once the burn scars mature, the residual scar deformity can be improved by reconstructive surgical procedures.