Association between cumulative surgeon experience and long-term outcomes in complex abdominal wall reconstruction.

PURPOSE: While many factors have been correlated with lesser outcomes in abdominal wall reconstruction (AWR), the impact of surgeon experience has yet to be elucidated. We sought to evaluate the effect of cumulative surgeon experience on long-term complex AWR outcomes. METHODS: We conducted a comprehensive review of all consecutive patients who underwent AWR using biologic mesh for the repair of ventral hernias or tumor resection defects from March 2005 to June 2019. The primary outcome measure was hernia recurrence (HR). Secondary outcomes were surgical site occurrences (SSOs) and surgical site infections (SSIs). Patients were a priori categorized into the following groups according to the cumulative number of hernia repairs performed by their surgeons: low (< 50), moderate experience (50-100), and high (> 100) experience. RESULTS: We identified 60 surgeons and 650 consecutive patients (62% women) who met our inclusion criteria. In adjusted models, AWR performed by surgeons with high experience was associated with a fourfold lower risk of HR (hazard ratio, 0.28; 95% confidence interval, 0.08 to 0.87), but the odds of surgical site occurrences (odds ratio, 0.72, 95% confidence interval, 0.34 to 1.52) and surgical site infections (odds ratio, 0.89, 95% confidence interval, 0.26 to 2.86) did not differ significantly in the high-experience group. CONCLUSIONS: High surgical experience, defined as > 100 cumulative hernia repairs, is predictive for markedly lower HR rates in complex AWR. These findings have potential implications for preoperative risk assessment, patient-centered surgeon selection, regulatory oversight, specific referral patterns, designations of centers of excellence, and individual provider or trainee quality improvement.

[DOTAP liposome-mediated transfection of human adipose-derived stemcells with pIRES2-EGFP-VEGF plasmid and target gene expression].

Objective:To explore liposome-mediated transfection of human adipose-derived stem cells (hASCs) with vascular endothelial growth factor(VEGF) gene and to investigate the expression of VEGF after transfection.Method:Lipoaspirate was digested using collagenase.Cell pellet was harvested and subcultured to passage 4.Phenotype was detected with flow cytometry and multilineage differentiation was induced for the identification of hASCs.hASCs was transfected with pIRES2-EGFP-VEGF plasmid using DOTAP liposome.The intracellular expression of VEGF was detected by immunofluorescent staining and the VEGF concentration in supernatant was analyzed by ELISA.Result:1 ml lipoaspirate yielded(4.38±0.21)×105 cells.hASCs on passage 4 showed high expression of CD90(81.49%) and low expression of CD19(6.37%),CD31(14.91%),CD34(17.56%) and CD45(15.39%).GFP and VEGF were observed in transfected hASCs.The transfection efficiency was(43.69±18.53)%.Untransfected hASCs did not express GFP but low level of VEGF.The optical density of VEGF intransfected hASCs is 2.13 fold of untransfected hASCs.The VEGF concentration in supernatant of transfected hASCs significantly increased over time and exhibit statistic differences compared with untransfected hASCs(P<0.05).Conclusion:hASCs were successfully transfected with pIRES2-EGFP-VEGF plasmid using DOTAP liposome.The post-transfection expression and secretion of VEGF remarkably increased.

Potential methane reservoirs beneath Antarctica.

Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.

Skin grafts used in combination with free flaps for intraoral oncological reconstruction.

Surgeons have relied less on skin grafts for intraoral reconstruction by extending free flap tissue onto adjacent areas that could be potentially skin grafted. Split-thickness skin grafts provide thin, reliable epithelial coverage to tissue beds that can be grafted without requiring additional flap tissue. The combined use of split-thickness skin grafts with free tissue transfer may be advantageous in select situations. Four patients underwent intraoral tumor resection with immediate reconstruction using free tissue transfer and split-thickness skin grafts. Skin grafting the tongue component of combined hemiglossectomy and floor-of-mouth (FOM) defects rather than spanning the tongue-FOM junction with flap tissue may prevent excessive bulk, improve tongue mobility, and reduce the size requirement of the flap. A split-thickness skin graft can be applied to the intraoral surface of free flaps used to reconstruct through-and-through orocutaneous defects, reducing the complexity of flap design and inset. Maxillectomy defects reconstructed with muscle flaps can be epithelialized immediately with the application of a split-thickness skin graft to provide a stable obturator cavity. In select cases, the combination of split-thickness skin grafts and free tissue transfer may have advantages over the use of flap tissue alone to cover the adjacent areas of a complex defect capable of being grafted.

Comparison of cost for DIEP and free TRAM flap breast reconstructions.

A recent article by Kaplan and Allen suggested that deep inferior epigastric perforator (DIEP) flap breast reconstruction was less expensive than reconstruction performed with free transverse rectus abdominis musculocutaneous (TRAM) flaps. To test that hypothesis, a series of patients who had undergone unilateral breast-mound reconstruction by the first author using DIEP or free TRAM flaps between November 1, 1996, and March 30, 2000, were reviewed. Bilateral reconstructions and reconstructions performed by other surgeons in the department were excluded to eliminate all variables except the choice of flap. All hours in the operating room and days in the hospital until discharge were included. Early readmissions for the treatment of complications were included, as were the costs of the mastectomy in the case of immediate reconstructions, but late revisions and nipple reconstructions were not. The totals were then converted into resource costs in 1999 dollars, and the DIEP and free TRAM flap groups compared. There were 21 DIEP flaps and 24 free TRAM flaps in the series. In this series, there was no significant difference between the cost of DIEP and free TRAM flap breast reconstruction.

Reduction of abdominal adhesions using composite collagen-GAG implants for ventral hernia repair.

Structural biomaterials can restore abdominal wall integrity but may cause adhesions to the underlying viscera. Collagen-glycosaminoglycan (CG) matrices induce the formation of connective tissue and may reduce adhesion formation to permanent biomaterials such as polypropylene (PP) mesh. Composite implants were created by interposing PP mesh within a porous CG matrix created composite implants. The implants were cross-linked with glutaraldehyde one group (CG-G/PP) or left untreated (CG-nG/PP) and compared to PP mesh. At 4 weeks, the abdominal wall was assessed for the degree of adhesions. The composite implants developed a nascent connective tissue-like structure that reduced adhesions to the bowel. The thickest connective tissue developed in the CG-G/PP group (0.7 +/- 0.1 mm) and thinnest in the PP mesh (0.05 +/- 0.01 mm). The surface area covered with adhesions was greatest in the PP group (72 +/- 17%) compared with the CG-G/PP group (28 +/- 15%) or the CG-nG/PP group (21 +/- 8%). Bowel preferentially adhered to the PP mesh, whereas omentum had some adherence to all constructs. Integrating a biodegradable extracellular matrix analog with a permanent structural biomaterial reduced adhesions in this animal model. Alterations in cross-linking of the CG matrix altered the biological response. This technology may be useful in reconstructive surgery by reducing adhesion formation, while maintaining the strength of permanent structural biomaterials.

Comparison of cultured and uncultured keratinocytes seeded into a collagen-GAG matrix for skin replacements.

A well-characterised collagen-glycosaminoglycan (CG) matrix functions as an extracellular matrix analogue (ECMA) of dermis on full-thickness wounds. The epidermis can be reconstituted by seeding autologous uncultured keratinocytes into the matrix prior to grafting. We hypothesised that seeding the CG matrix with keratinocytes cultured to sub-confluence may provide the ECMA with more proliferating keratinocytes than with uncultured keratinocytes. Autologous cells were isolated from split-thickness skin grafts and cultured to sub-confluence. ECMAs were seeded by centrifuging cultured (n = 8) or uncultured (n = 8) autologous keratinocytes into a CG matrix at a density of 100,000 cells/cm2, then applied onto full-thickness wounds on Yorkshire pigs. Gross and histologic observations were made up to 21 days post-grafting. At 14 days, a fully differentiated epidermis was present on all graft sites, but the epidermis of the cultured-cell-seeded matrices was thicker, 180 (19) microns, than the uncultured-cell-seeded matrices, 110 (18) microns. The epidermis of cultured-cell-seeded matrices was acanthotic, containing 14 (4) cell layers, as compared to uncultured-cell-seeded matrices, 9 (1) cell layers. The number of subepithelial keratinocyte cysts/cm cross-section present in the neodermis was also greater in cultured-, 1.35 (0.37), than in uncultured-cell-seeded matrices, 0.47 (0.35). Epidermal confluence on day 14 was 96 (3)% on cultured-cell-seeded grafts and 50 (17)% on uncultured-cell-seeded grafts. These results are consistent with the hypothesis that the process of in vitro cell cultivation increases the proportion of dividing cells in preference to differentiated cells. This technology may be useful in reconstruction of specialised bilayer tissues with minimal donor sites.

Organized skin structure is regenerated in vivo from collagen-GAG matrices seeded with autologous keratinocytes.

A well-characterized collagen-glycosaminoglycan matrix (CGM) that has been shown to function as a dermal analog was seeded with freshly disaggregated autologous keratinocytes and applied to full-thickness wounds in a porcine model. CGM were impregnated with 50,000 keratinocytes per cm2, a seeding density that produces a confluent epidermis within 19 d post-grafting and affords a 60-fold surface expansion of the donor epidermis. In this study, the temporal sequence of events in epidermal and neodermal formation was analyzed histopathologically and immunohistochemically from 4 to 35 d post-grafting. The epidermis was observed to form from clonal growth of individual keratinocytes into epithelial cords and islands that gradually enlarged, coalesced, differentiated to form large horn cysts, and finally reorganized at the graft surface to form a fully differentiated, normally oriented epidermis with rete ridges. Simultaneously, a neodermis formed from migration of endothelial cells, fibroblasts, and macrophages into the CGM from the underlying wound bed, resulting in formation of blood vessels, the production of abundant extracellular matrix, and the degradation of the CGM fibers, respectively. Gradually, the stromal cellularity of the CGM decreased and collagen deposition and remodeling increased to form a neodermal connective tissue matrix beneath the newly formed epidermis. Complete dissolution of the CGM occurred, partly as a result of degradation by an ongoing foreign-body giant cell reaction that peaked at 8-12 d post-grafting, but neither acute inflammation nor evidence of immune stimulation were observed. Within 1 mo, many structural components of normal skin were reconstituted.

Effect of keratinocyte seeding of collagen-glycosaminoglycan membranes on the regeneration of skin in a porcine model.

A collagen-glycosaminoglycan matrix, impregnated with autologous keratinocytes, was applied as island grafts onto full-thickness porcine wounds to determine whether complete epidermal coverage could be achieved in a single grafting procedure. Twenty-four grafts with seeding densities ranging from 0 to 3,000,000 cells/cm2 were used to determine the kinetics of epidermal coverage. The time sequence of epidermal formation was then studied between days 14 and 28 using four additional grafts, each seeded with a density of 500,000 cells/cm2. Autologous keratinocytes proliferated as the collagen-glycosaminoglycan matrix was vascularized to form a confluent epidermis by 2 weeks in matrices seeded with at least 100,000 cells/cm2. The epidermal thickness and the number of keratinocyte cysts observed in the neodermis at 2 weeks increased linearly with the logarithm of the seeding density. Sequential analysis of neoepidermis showed the nascent epidermis to be hyperplastic, parakeratotic, and focally lacking in granular layer differentiation at 2 weeks. After 2 weeks, it underwent normal maturation and differentiation. Irrespective of seeding density at 2 weeks the collagen-glycosaminoglycan matrix was well vascularized, contained a dense cellular infiltrate, and was almost completely degraded. These studies demonstrate that seeded keratinocytes proliferate and differentiate to form a confluent epidermis by 2 weeks in matrices seeded with at least 100,000 cells/cm2.

Evaluation of a DNA probe assay (Gen-Probe PACE 2) as the test of cure for Neisseria gonorrhoeae genital infections.

A DNA probe (Gen-Probe PACE 2) detects portions of viable and nonviable organisms, and test results could remain positive after effective treatment of genital Neisseria gonorrhoeae infection. Twenty patients underwent test-of-cure studies 6 to 11 days after standard treatment for gonorrhea; in each case the DNA probe finding was negative. The Gen-Probe PACE 2 probe is reliable for test-of-cure study as early as 6 days after treatment.

Prevalence of Trichinella spiralis in black bears (Ursus americanus) from Newfoundland and Labrador, Canada.

Tongue and diaphragm samples from 158 black bears (Ursus americanus) from Newfoundland and Labrador were examined for Trichinella spiralis. No larvae were detected in samples from the island of Newfoundland but one animal from the Labrador samples was infected. The results of this and other studies suggest a lack of involvement of the black bear in a sylvatic cycle of T. spiralis in eastern Canada.

Nocardia asteroides keratitis: a case associated with soft contact lens wear.

Ocular nocardiosis is rare. Most cases of nocardial keratitis have resulted from corneal trauma by objects contaminated with the organism. We describe the first case of Nocardia asteroides keratitis associated with an extended wear soft contact lens. We also describe its successful treatment with topical trimethoprim-sulfamethoxazole in combination sulfacetamide.